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  Subjects -> CHEMISTRY (Total: 902 journals)
    - ANALYTICAL CHEMISTRY (55 journals)
    - CHEMISTRY (636 journals)
    - CRYSTALLOGRAPHY (21 journals)
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    - INORGANIC CHEMISTRY (43 journals)
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    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (636 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 14)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 29)
ACS Catalysis     Hybrid Journal   (Followers: 49)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 23)
ACS Macro Letters     Hybrid Journal   (Followers: 27)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 42)
ACS Nano     Hybrid Journal   (Followers: 321)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Hybrid Journal   (Followers: 25)
Acta Chemica Iasi     Open Access   (Followers: 6)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 8)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 7)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 8)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Open Access   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 62)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 77)
Advances in Chemical Science     Open Access   (Followers: 20)
Advances in Chemistry     Open Access   (Followers: 25)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20)
Advances in Drug Research     Full-text available via subscription   (Followers: 25)
Advances in Environmental Chemistry     Open Access   (Followers: 7)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 27)
Advances in Nanoparticles     Open Access   (Followers: 17)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Polymer Science     Hybrid Journal   (Followers: 45)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 4)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 8)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 3)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 68)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 22)
American Journal of Chemistry     Open Access   (Followers: 32)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 15)
Anadolu University Journal of Science and Technology A : Applied Sciences and Engineering     Open Access  
Analyst     Full-text available via subscription   (Followers: 37)
Angewandte Chemie     Hybrid Journal   (Followers: 185)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 268)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 26)
Applied Surface Science     Hybrid Journal   (Followers: 34)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 3)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 378)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 11)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 24)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 138)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 92)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 19)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 25)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 11)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 25)
Carbon     Hybrid Journal   (Followers: 70)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 9)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 13)
Cellulose     Hybrid Journal   (Followers: 11)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 22)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 75)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 27)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 216)
Chemical Science     Open Access   (Followers: 28)
Chemical Technology     Open Access   (Followers: 35)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 22)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 33)
Chemistry & Industry     Hybrid Journal   (Followers: 8)
Chemistry - A European Journal     Hybrid Journal   (Followers: 176)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
Chemistry and Materials Research     Open Access   (Followers: 21)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 46)
Chemistry of Materials     Hybrid Journal   (Followers: 281)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 21)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 11)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
Cogent Chemistry     Open Access   (Followers: 2)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 11)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 23)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access   (Followers: 1)
Composite Interfaces     Hybrid Journal   (Followers: 7)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 1)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 13)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 4)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 7)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 8)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Chromatography     Hybrid Journal  
Current Green Chemistry     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Microwave Chemistry     Hybrid Journal  
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 14)
Current Research in Chemistry     Open Access   (Followers: 9)
Current Science     Open Access   (Followers: 74)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 2)
Dalton Transactions     Full-text available via subscription   (Followers: 26)
Detection     Open Access   (Followers: 4)

        1 2 3 4 | Last

Journal Cover
Applied Surface Science
Journal Prestige (SJR): 1.093
Citation Impact (citeScore): 4
Number of Followers: 34  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0169-4332
Published by Elsevier Homepage  [3161 journals]
  • Synthesis, characterization and rare earth elements adsorption properties
           of phosphonate metal organic frameworks
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Bianca Maranescu, Lavinia Lupa, Aurelia Visa The architectural structures of MOFs provide special properties as high thermal and mechanical stability, high surface areas and large pore sizes with potential applications in diverse areas. Rare Earth Elements (REEs) are widely used in the various disciplines: luminescent compounds, catalysis, coordination chemistry, solid state chemistry, organometallic compounds, and environmental chemistry. For environmental protection, the elimination of toxic metals from wastewaters previously releasing into the environment are required. Phosphonate MOFs were obtained in our labs by the reaction of divalent inorganic sulphates with phosphonoacetic acid (Cp) or styrylphosphonic (Sp) in hydrothermal conditions and characterized by FTIR and TGA.The phosphonate MOFs were used in the removal process of Cs(I) and Tl(I) ions from aqueous solutions done in batch mode, varying the initial concentration of the metal ions, keeping for all the samples a solid:liquid ratio of 1 g/L. From the experimental data were observed that the adsorption capacity developed by the studied materials increase in the following order: CuCp 
       
  • Al2O3 formed by post plasma oxidation of Al as a Gate dielectric for
           AlGaN/GaN MIS-HEMTs
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Kuldeep Takhar, Bhanu B. Upadhyay, Yogendra K. Yadav, Swaroop Ganguly, Dipankar Saha We demonstrate patterned Al2O3 formation by post-plasma oxidation of a thin layer of aluminium (Al) film deposited by electron beam evaporator in area selective regions. The oxide quality is observed to further improve by annealing in O2 and N2 environment. Schottky and metal-insulator-semiconductor diodes are also fabricated to characterize its electrical behaviour. The thickness and high quality of the oxide formed is confirmed from Transmission Electron Microscope (TEM) and X-Ray Photoelectron Spectroscopy (XPS) analysis. The O2 and N2 annealed samples show Oxygen to Aluminium atomic ratio of ~1.5 confirming near-ideal stoichiometry. The energy band-gap (Eg) of the Plasma-Oxide, O2-Annealed and N2-Annealed estimated from energy loss spectra of O1s are found to be 5.0, 5.5 and 6.8 eV, respectively. The valance band off-set for the corresponding oxides as estimated from low energy spectra analysis are found to be 0.8, 0.7 and 0.8 eV, respectively. The electrical characteristics also confirm improvement over the control device. The ION/IOFF ratios are observed to be 106, 1010 and 106 for the Plasma Oxide, O2 Annealed and N2 Annealed oxides, respectively, as compared to 103 for the Control sample. The dielectric constants (εox) for the corresponding oxides as determined from the CV characteristics are found to be 5.3, 8.5 and 8.7, respectively.
       
  • ToF-SIMS depth profiling of nanoparticles: Chemical structure of
           core-shell quantum dots
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Alexander Gulin, Aleksander Shakhov, Alexander Vasin, Artyom Astafiev, Olga Antonova, Sergei Kochev, Yurii Kabachii, Alexandre Golub, Victor Nadtochenko Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a valuable tool for chemical imaging of surfaces and depth profiling. The main goal of the present work is to develop technique for chemical composition and structure characterization of core-shell quantum dots (QDs) by ToF-SIMS combined with sputter depth profiling. We report a method to acquire 6 nm CdSe/ZnS core-shell QDs depth profiles distinguishing core and shell layers. Obtained selenium and sulfur profiles correlate with core-shell structure characterized by transmission electron microscopy, X-ray diffraction and luminescence spectroscopy. Sample preparation for ToF-SIMS analysis involves accurate QDs deposition on thoroughly cleaned substrate surface, resulted in fairly flat topography and absence of significant aggregations verified by atomic force microscopy. We demonstrate capabilities of proposed technique for analysis of dopant atoms by establishing depth distribution of dopant atom inside Mn/ZnS/CdS quantum dots. Obtained results suggest that QDs do not melt under Cs+ or Bi3+ bombardment.Graphical abstractUnlabelled Image
       
  • Oscillatory regimes of Langmuir probe current in femtosecond
           laser-produced plasmas: Experimental and theoretical investigations
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): P. Nica, S. Gurlui, M. Agop, C. Focsa We investigate the oscillatory regimes of the Langmuir probe current recorded for the electrical characterization of femtosecond laser-produced plasma. The influence of metallic target biasing, which can perturb the ambipolar electric field generated through the charge separation at early stages of the expansion, is also studied. Two distinct behaviors are evidenced, and they point to the existence of two plasma structures: a fast one consisting in promptly ejected highly charged particles, and a slow “tail” of thermalized particles. Theoretically, a non-differentiable model which involves two scale resolutions is developed. Assuming the principle of scale resolution superposition, the current density at global scale is expressed as the sum of the current density at Coulomb and the thermal scale resolutions, in agreement with the experimental data. Interestingly, the theoretical estimation of oscillation frequencies shows a correspondence with the filling factor hierarchy in the fractional quantum Hall effect.Graphical abstractUnlabelled Image
       
  • Stable hybrid organic/inorganic multiple-read quantum-dot memory device
           based on a PVK/QDs solution
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Sae-Wan Kim, Jin-Beom Kwon, Na-Ri Kim, Jae-Sung Lee, Sang-Won Lee, Byoung-Ho Kang, Ju-Seong Kim, Binrui Xu, Jin-Hyuk Bae, Shin-Won Kang A thin-film memory device is proposed herein, based on quantum dots (QDs) with bi-stable characteristics under a positive voltage bias. The synthesized QDs had a CdSe/ZnS core/shell structure. The charge confinement effect within the QDs in the charge-storage layer was enhanced by adding (poly(9-vinylcarbazole)) (PVK). As the PVK concentration increases, the on/off ratio of the device increases. Noise was also reduced and stable I-V characteristics were demonstrated. Each thin film was fabricated by a spin-coating method, among solution process methods. The on/off ratio of the fabricated device was found to be maximum 378 × 103 at 1.5 wt% PVK concentration. The initial on/off state was maintained even when a negative voltage (commonly used for the “erase” function) was applied. In addition, the write voltage of the fabricated device using the conductive polymer poly-TPD was reduced from 2.8 to 1.7 V. By optimizing PVK concentration and forming the poly-TPD thin film, the fabricated memory device had an on/off ratio of about 4 × 103 at 0.5 V and the stored current maintained the initial value even after 200 h. Even with a single write process, the initially formed high state is maintained for more than 200 h, and it is possible to read repeatedly.
       
  • Compression of dry lysozyme targets: The target preparation pressure as a
           new parameter in protein thin film production by pulsed laser deposition
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Catalin Constantinescu, Andreea Matei, Marshall Tabetah, Maria Dinescu, Leonid V. Zhigilei, Jørgen Schou Film growth of the well-known protein, chicken lysozyme, produced by the dry technique, pulsed laser deposition (PLD), from a compressed powder target has been investigated as a function of the target preparation pressure. PLD is a versatile technique for fabricating high quality films of inorganic materials, but the laser beam will typically produce fragments of molecules in the target and subsequently in the deposited films. We demonstrate that the pressure applied to compact the target prior to the laser irradiation is an important parameter that determines the deposition rate as well as the extent of fragmentation of the deposited molecules. The deposition process was carried out in vacuum using dry targets prepared with compaction pressure in the range 10–160 bar. The residual water in pockets of the lysozyme molecules drives fragments or intact lysozyme out of the target. At the intermediate fluence of 2 J/cm2, the deposition rate of the material (fragments or intact molecules) rises from 3 to 9 ng/cm2 per shot as the compaction pressure increases from 10 to 160 bar. However, the number of intact molecules falls down by almost two orders of magnitude in the same pressure range. This is explained by a stronger cohesion of the target material prepared at higher compression pressure, such that more energy and thus a higher temperature are required for the onset of material ejection. At the highest compression pressure, it means that no intact molecules survive the ejection. The results indicate that there is a pressure range where both a reasonable deposition rate and a considerable fraction of intact molecules in the films can be achieved. These experimental observations are consistent with the results of coarse-grained molecular dynamics simulations, where the fraction of intact lysozyme molecules is observed to vanish as the maximum temperature in the irradiated target increases.
       
  • Effects of porosity and particle size on the gas sensing properties of
           SnO2 films
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Min Ah Han, Hyun-Jong Kim, Hee Chul Lee, Jin-Seong Park, Ho-Nyun Lee Metal oxide semiconductors are widely used as gas sensing materials; thus, improving their gas sensing properties is of some interest. The microstructure of a SnO2 film was controlled using the thermal evaporation technique at a relatively high process pressure. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis were used to characterize microstructures, crystallinity, particle size, and the surface area that was dramatically altered as a function of the process pressure. In all cases, SnO2 films had interconnected network structures with open pores; continuous grain growth was observed through the neck between the SnO2 nanoparticles. The responses of sensors fabricated at different depositional pressure were evaluated by monitoring changes in the electrical resistance of CO gas. The gas sensor deposited at 0.2 Torr showed a high response and short response time owing to its high porosity (97%) and nano-sized particles (8.4 nm). The results confirm that porosity and particle size play key roles in determining the gas response.Graphical abstractUnlabelled Image
       
  • First principles determination of formation of a Cr shell on the interface
           between Y–Ti–O nanoparticles and a ferritic steel matrix
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Ki-Ha Hong, Jae Bok Seol, Jeoung Han Kim Cr-rich shells are known to decrease the lattice misfit of Y–Ti–O nanoparticles and contribute to high thermal stability. In the present work, the formation of a Cr-rich shell on the Y2Ti2O7/Fe interface is studied via density functional theory and examined with electron microscopy analyses. The density functional theory calculation showed that Cr substitution in Y2Ti2O7 is not allowed. Instead, Cr is favorably segregated on the interface of the Fe site owing to the strong binding energy between Cr and O. Atom probe tomography observations confirmed the formation of a Cr shell at the interface between Y2Ti2O7 nanoparticles and the Fe matrix. Contrary to the density functional theory calculation, a considerable Cr concentration was detected inside the oxide. However, additional transmission electron microscopy observation of very coarse Y2Ti2O7 nanoparticles demonstrated that the Cr concentration is almost negligible inside the oxide, which is consistent with the calculated prediction.Graphical abstractUnlabelled Image
       
  • Analysis of enhanced hole transport in naphthalene dicarboxyimide
           (NDI)-based n-type polymer field-effect transistors using
           solution-processed reduced graphene oxide electrodes
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Museok Ko, Yeoryang Lee, Youngjoo Jo, Jun Hyeok Jang, Mi Jung Lee In this study, organic field-effect transistors (OFETs) using a naphthalene dicarboxamide (NDI)-based n-type semiconducting polymer and electrodes comprising either Au or reduced graphene oxide (rGO) were fabricated. Compared with those with Au electrodes, transistors with rGO electrodes exhibited enhanced hole transport characteristics. The analysis of the interaction between the NDI-based polymer and the two electrodes revealed satisfactory hole transport in terms of device performance with the rGO electrode despite the less favorable work function for the injection of holes into the polymer semiconductor, corresponding to the formation of interfacial dipoles of different magnitudes. The electron orbital structure of the rGO electrode induced a smaller shift by the dipole moment at the interface between the electrode and semiconductor compared with that induced by the electron orbital structure of the gold electrode to promote ambipolarity. In both cases, energy barriers for the injection of charge at the interface were determined by ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy analysis. In addition, a complementary logic inverter comprising two identical OFETs based on n-type NDI derivative and rGO electrodes with improved hole transport properties was fabricated.Graphical abstractEnhanced hole transport in n-type semiconducting polymers with reduced graphene oxide contact electrode compared to that with gold electrode was analyzed.Unlabelled Image
       
  • Click chemistry on silicon nitride for biosensor fabrication
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): P.M. Dietrich, N. Lange, A. Lippitz, M. Holzweber, N. Kulak, W.E.S. Unger Biosensors are of essential importance in medical and biological diagnostics. Often, they are produced using silane chemistry on glass or silicon oxide surfaces. However, controlling that silane chemistry is challenging. Here, we present an alternative strategy to form functional organic layers and biosensors on silicon nitride (Si3N4). H-terminated Si3N4 films are used to generate reactive azide groups by various azidation methods. Biomolecular probes can then be immobilized using click chemistry reactions with the azide groups and due to its high sensitivity in XPS a fluorine-substituted test alkyne was utilized to optimize click chemistry conditions. After that a biotinylated alkyne was clicked to Si3N4 surfaces followed by immobilization of streptavidin as analyte in a model assay. The functionalized surfaces were thoroughly characterized by surface chemical analysis using X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy.
       
  • Low temperature epitaxy of high-quality Ge buffer using plasma enhancement
           via UHV-CVD system for photonic device applications
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Bader Alharthi, Wei Dou, Perry C. Grant, Joshua M. Grant, Timothy Morgan, Aboozar Mosleh, Wei Du, Baohua Li, Mansour Mortazavi, Hameed Naseem, Shui-Qing Yu Under low thermal budget, high-quality Ge buffers were grown using plasma enhancement chemical vapor deposition (PECVD) technique by a two-step method in a cold-wall ultra-high vacuum system. Low threading dislocation density on the order of 107 cm−2 with root mean square roughness values of several nanometers was achieved. Photoluminescence and ellipsometry characterizations revealed that the material and optical characteristics are comparable to that of a Ge buffer grown using the conventional CVD method at high temperature. Moreover, growth comparison of an active group IV GeSn layer on Ge buffers that were grown using PECVD at low temperature and CVD at high temperature was carried out to further examine its material and optical properties for optoelectronic device applications. The results indicate GeSn films with similar material and optical properties were achived using both Ge buffers. This work provides a promising growth process for industry to deposit Ge under conditions compatible with complementary metal–oxide–semiconductor technology.
       
  • Temperature- and position-dependent Raman study on carrier concentration
           of large-area monolayer WS2
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Hong Gu, Kebei Chen, Xiaodong Gao, Ke Xu, Youming Lu, Xinke Liu Large-area monolayer WS2 triangles with an average lateral dimension of ~60 μm were grown by chemical vapor deposition (CVD) and a Raman study on the carrier concentration is presented. With temperature-dependent Raman spectra measured over a temperature range of 3 to 520 K, it indicates that the full width at half maximum and intensity of A1g mode were strongly affected by the carrier concentration and corresponding electron-phonon coupling, while the E12g mode was less influenced. In the position-dependent Raman spectra, an increasing number of charge carriers were also discovered along the growth direction. And an upward energy band bending and impurities adsorption were found in the edge regions, which should be taken into consideration for improving the performance of monolayer growth.Graphical abstractUnlabelled Image
       
  • Structural and chemical investigation of interface related magnetoelectric
           effect in Ni/BiFe0.95Mn0.05O3 heterostructures
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): B. Negulescu, J. Wolfman, C. Daumont, N. Jaber, P. Andreazza, T. Denneulin, S. Schamm-Chardon The magnetoelectric coupling mechanism in Ni/BiFe0.95Mn0.05O3 heterostructures is investigated through a detailed microstructural study of the BiFe0.95Mn0.05O3 film and a chemical analysis of the Ni/BiFe0.95Mn0.05O3 interface. The four structural variants expected in BiFe0.95Mn0.05O3 are detected by high resolution X-ray diffraction reciprocal space mapping method. The ferroelectric domain structure is imaged with transmission electron microscopy. Oxidized Ni is evidenced at the Ni/BiFe0.95Mn0.05O3 interface by electron energy loss spectroscopy and X-ray photoemission spectroscopy, although the degree of Ni oxidation is independent of the magnetoelectric state of the heterostructure.
       
  • Surface layer characteristics of SAF2507 duplex stainless steel treated by
           stress shot peening
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Ming Chen, Chuanhai Jiang, Zhou Xu, Vincent Ji In this study, stress shot peening (SP) treatments were implemented on the austenitic and ferritic stainless steel. The surface layer characteristics including residual stress states and microstructures of the treated material were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods. The stress analysis results showed that stress SP generated a thicker surface region with higher compressive residual stress than conventional SP, and the variations of residual stresses were tightly associated with the level and direction of the preloading. The microstructural evolutions determined by Rietveld refinement demonstrated that stress SP promoted the plastic deformation and conferred more refined crystallite and higher lattice distortion into the material. TEM observations confirmed that severely deformed microstructures characterized by higher density dislocations and smaller subgrains or grains were formed in the samples with stress SP. Moreover, the experimental results suggested that the plastic deformation was inhomogeneous within the two phases, and austenite suffered more changes in microstructure than ferrite during plastic deformation. It was concluded from the present study that stress SP was more potent in inducing compressive stress, microstructure refinement and work hardening in the surface layer of the duplex alloy than conventional SP.
       
  • Novel spinel nanocomposites of NixCo1−xFe2O4 nanoparticles with N-doped
           graphene for lithium ion batteries
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Xinyan Jiao, Li Cai, Xifeng Xia, Wu Lei, Qingli Hao, Daniel Mandler A dual-doping strategy was applied to fabricate the novel electrode materials. For the first time, the spinel hybrids of nanosized NixCo1−xFe2O4 with N-doped graphene (Nx-NG) were synthesized by a hydrothermal co-precipitation method. The size of NixCo1−xFe2O4 (Nx) nanoparticles on N-doped graphene can be tuned with the regulation of Ni/Co content. Among these nanocomposites, the Ni0.4Co0.6Fe2O4 nanoparticles with the smallest average size of 10 nm are uniformly anchored on the N-doped graphene. The electrochemical characterizations display that the N0.4-NG exhibits the best electrochemical lithium storage performance compared to other five nanocomposites. It delivers a high capacity of 1367.0 mA h g−1 at the first discharge process,and the reversible capacity retention of 87% (2nd to 50th) at 0.1 A g−1. The excellent electrochemical performance of N0.4-NG can be owing to the small size of nanoparticles and its well-combination with N-doped graphene, which provide the large surface area and promote the ion/electron transfer rate. The synergistic effect resulted from the strong interaction between N0.4 and N-doped graphene is contributed to the enhanced electrochemical performance of N0.4-NG. This study not only extends graphene-based electrode materials for lithium ion battery, but also promotes the development of energy resources.Graphical abstractUnlabelled Image
       
  • The influence of tensile strain on water adsorbed on Fe (100) surface:
           Surface chemistry aspect of stress corrosion cracking
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Weijia Liu, Jian Sun, Cheng Ye The water adsorption on Fe (100) surface with and without surface tensile strain is studied by spin-polarized self-consistent density functional theory calculations to elaborate the influence of tensile strain on surface chemistry. We find that the surface tension not only enhances the interaction between water and surface but also lowers the energy barrier for water dissociation on the surface. The dissociated reactive OH fragment may further attack the iron surface and the dissociated reactive H fragment could transfer into iron lattice and cause H embrittlement. This study clearly shows that the stressed induced surface chemistry could be an important aspect of stress-corrosion cracking (SCC) in iron based materials.Graphical abstractUnlabelled Image
       
  • Controllable drop splashing on picosecond laser patterned hybrid
           superhydrophobic/-philic surfaces
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Huan Yang, Ke Sun, Yao Xue, Changwen Xu, Dianyuan Fan, Yu Cao, Wei Xue Drop splashing is a very common phenomenon when liquid drops impact on solid surfaces. In this study, picosecond laser fabricated hybrid superhydrophobic/-philic (SH/SHL) surfaces with designed patterns are successfully applied to control drop splashing on solid surfaces. Using high-speed imaging, the water drop impact behaviors on differently patterned hybrid SH/SHL surfaces were investigated. The experimental results show that the water drop splashing could be restrained greatly on patterned hybrid SH/SHL surfaces, compared with SH or SHL surfaces. On a hybrid SH/SHL surface with a 2 mm diameter circular SH pattern, the drop splashing for a Weber number up to 600 (the corresponding impact velocity is 4.2 m/s) can be totally suppressed. Moreover, we found that the oriented distribution of splashing can be regulated by the shape and size of SH patterns. These results suggest that patterned hybrid SH/SHL surfaces could be a practical approach to regulate or control drop splashing.
       
  • Autogenous chemical and structural transition and the wettability of
           electropolymerized PANI surface
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Yoganandan Govindaraj, Smrutiranjan Parida A change in surface wettability due to autogenous chemical and structural transition of electropolymerized polyaniline film is presented. A gradual increase in water contact angle of>150° on electropolymerized PANI surface was observed over the period indicated superhydrophobic surface. While an increase in the content of quinoneimine structure was observed, the surface morphology showed the formation of a dendritic structure on the aged PANI surface. Water contact angle measurement using different liquids showed the surface energy of PANI has decreased>70% after 30 days of exposure in the ambient environment. The findings are explained based on the mechanism of self-assembled micro-nano-cluster formation over PANI surface during continuous exposure.Graphical abstractUnlabelled Image
       
  • Effects of laser power on immersion corrosion and electrochemical
           
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Wen Zhao, Dejun Kong Amorphous AlFeSi coatings were fabricated on S355 structural steel using a laser thermal spraying (LTS). The surface and cross–section morphologies, chemical composition, phases and chemical valences of obtained coatings fabricated at the laser power of 1400, 1600 and 1800 W were analyzed using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X–ray diffractometer (XRD), and X–ray photoelectron spectrometer (XPS), respectively. The immersion corrosion and electrochemical corrosion performances of AlFeSi coatings fabricated at the different laser power were investigated using a salt spray corrosion (SSC) chamber and electrochemical workstation. The results show that the laser thermal sprayed AlFeSi coatings are primarily composed of the crystalline and amorphous mixed phases of AlFe, AlCrFe2, AlFe3 and Al0.7Fe3Si0.3. The Al, Fe and Si of AlFeSi coating are diffused into the substrate at the coating–substrate interface, forming a metallurgical bonding. In the immersion corrosion test, the formation of occluded cell produces the acidification in the porosity, which gradually expands to corrosion pits and cracks, accelerating the corrosion process. The corrosion current densities (Icorr) of AlFeSi coatings at the laser power of 1400, 1600 and 1800 W are 9.989 × 10−6, 8.898 × 10−6, and 6.542 × 10−6 A·cm−2, respectively, lower than 1.617 × 10−5 of substrate, the electrochemical corrosion resistance of AlFeSi coating increases with the increase of laser power.Graphical abstractPolarization curves of AlFeSi coatings fabricated at different laser power and substrate.Fig. 11 shows the potentiodynamic polarization curves of amorphous AlFeSi coatings fabricated at the different laser power and substrate. The current densities increased rapidly at the initial portion of anode branches on the polarization curves, indicating that the AlFeSi coatings were in an active dissolved state at the beginning of electrochemical corrosion. During the cathodic scanning period, oxygen absorption corrosion occurred on the electrode, which corresponded to the cathodic branches of polarization curves. It was generally believed that the corrosion potential (Ecorr) reflected the thermodynamic stability of electrochemical corrosion. The Ecorr values of AlFeSi coatings shifted positively as the laser power increased, indicating that the AlFeSi coatings fabricated at the higher laser power were less likely to be corroded. According to the corrosion kinetics, the corrosion current density (Icorr) reflected the corrosion rates of AlFeSi coatings, and the corrosion resistance of AlFeSi coatings increased with the increase of laser power.Unlabelled Image
       
  • Syngas production modified by oxygen vacancies over CeO2-ZrO2-CuO oxygen
           carrier via chemical looping reforming of methane
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Yajing Wang, Yane Zheng, Yuhao Wang, Kongzhai Li, Yaming Wang, Lihong Jiang, Xing Zhu, Yonggang Wei, Hua Wang Chemical-looping reforming of methane (CLRM) offers an effective approach for the production of syngas. A series of CexZryCu1−x−y (x = 0.6, 0.7, y = 0–0.35) mixed oxides were successfully prepared by sol-gel method, and characterized by means of XRD, H2-TPR, BET, XPS, Raman and CH4-TPR. The addition of Cu and Zr ions caused the distortion of CeO2 lattice and induced more oxygen vacancies, which promoted the mobility of lattice oxygen in the materials. CexZryCu1−x−y mixed oxides also owned smaller grain size and better thermal stability than pure CeO2-CuO mixed oxides. Among the series of CexZryCu1−x−y mixed oxides, the reducibility of Ce0.6ZrxCu0.4−x and Ce0.7ZrxCu0.3−x samples gradually increased with the Cu content. It was found that the Ce0.7Zr0.2Cu0.1 sample owned the most abundant oxygen vacancies on the surface. The CexZryCu1−x−y mixed oxides with lower Cu content (≤0.1) produced higher amount of H2 and CO while smaller CO2. Ce0.7Zr0.2Cu0.1 sample still retained better structural stability and thermal stability after 20 times cycled reaction.Graphical abstractIn the present work, we synthesized a series of CexZryCu1−x−y (x = 0.6, 0.7, y = 0–0.35) mixed oxides by sol-gel method. The Ce0.7Zr0.2Cu0.1 sample still retained better structural stability and thermal stability than CeCu samples during the successive chemical-looping reforming of methane (CLRM) process.Unlabelled Image
       
  • A high growth rate atomic layer deposition process for nickel oxide film
           preparation using a combination of nickel(II) diketonate–diamine and
           ozone
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Yuxiang Zhang, Liyong Du, Xinfang Liu, Yuqiang Ding In this study, we described an atomic layer deposition (ALD) process for the preparation of nanoscale nickel oxide (NiO) films with high growth rate by using a combination of nickel(II) diketonate–diamine (Ni(acac)2(TMEDA), TMEDA = N,N,N′,N′-tetramethyl-ethylenediamine) and ozone (O3). Typical self-limiting film growth behavior was observed between 200 and 275 °C, and growth saturation with respect to both precursor pulse time was verified. The chemical composition, crystalline phase, and surface morphology of the films were studied using X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. All the results confirmed that the ALD process occurred with high growth rate of approximately 2.0 Å/cycle and resulted in high-quality, smooth films.Graphical abstractWe described an atomic layer deposition process for the preparation of nanoscale nickel oxide films with high growth rate using a combination of Ni(acac)2(TMEDA) and O3. Typical self-limiting film growth behavior was observed between 200 and 275 °C, and growth saturation with respect to both precursor pulse time was verified. The obtained results demonstrated that the ALD process occurred with a high growth rate of approximately 2.0 Å/cycle and resulted in high-quality, smooth films.Unlabelled Image
       
  • Improving wear and corrosion properties of alumina coating on AA7075
           
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Babak Haghighat-Shishavan, Rasoul Azari-Khosrowshahi, Safa Haghighat-Shishavan, Masoud Nazarian-Samani, Naghi Parvini-Ahmadi An alumina coating with a thickness of 20–50 μm was deposited by plasma electrolytic oxidation (PEO) on an AA 7075 Al alloy in an alkali-aluminate electrolyte using a 5 kW DC power supply. After the formation of the coating, the effects of current density, electrolyte concentration, and process time on the coating characteristics were investigated comprehensively. In order to achieve improved tribological and corrosion properties, the prepared samples were evaluated by means of various characterization techniques including scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, micro-hardness, thickness and roughness measurements, corrosion potentio-dynamic, and pin-on-disk wear tests. Electrophoretic graphite absorption was subsequently carried out on the samples, which resulted in the desirable experimental results to boost the coating in terms of roughness, tribological, and corrosion properties. The positive effects of graphite absorption on the PEO coatings were also elaborated in detail.Graphical abstractUnlabelled Image
       
  • Great enhancement of electromagnetic wave absorption of
           MWCNTs@carbonaceous CoO composites derived from MWCNTs-interconnected
           zeolitic imidazole framework
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Shibin Lu, Ying Meng, Haibo Wang, Feifei Wang, Jiangtao Yuan, Hong Chen, Yuehua Dai, Junning Chen Associated with the unique structure and superior properties of zeolitic imidazolate frameworks (ZIFs) of Co-based metal-organic frameworks (MOFs), we synthesized the MWCNTs@carbonaceous CoO composites of a 3D interconnected network using multi-walled carbon nanotubes (MWCNTs) as decoration through the wet chemical and pyrolysis method. Due to the mutual coordination between proper magnetic loss and strong dielectric loss together with perfect impedance match, the MWCNTs@carbonaceous CoO composites exhibit the maximal reflection loss (RL) value of −50.2 dB with 1.84 mm thickness at 14.3 GHz, absorbing bandwidth (RL ≤ −10 dB) of 13.2 GHz (4.8–18 GHz) with respect to 1.0–4.0 mm thickness range. More importantly, the content of composites added to paraffin matrix is merely 10 wt%. In addition, the synergistic effect between CoO NPs and MWCNTs is also beneficial to the highly efficient electromagnetic (EM) wave absorption of the composites. Therefore, the obtained CoO NPs/MOF-derived composites with lightweight and thin performance can be an attractive candidate of the EM wave absorptive materials.Graphical abstractUnlabelled Image
       
  • Fractionation of clay colloids and their synthetic utility in vanadium
           hydroxide-clay thin film formation
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Ping Song, Qintang Li, László Almásy, Xianguo Tuo, Minhao Yan, Mark J. Henderson Stable mineral colloids play a role in the mobilization of actinide contaminants in the environment. In this paper we present a method to isolate and identify colloids released from high surface area sorbents associated with a proposed clay mineral barrier in a nuclear waste repository. The mineral colloids, which have a strong tendency to remain dispersed in solution, were separated from Al13- or (CeAl)-pillared clay sediment, adsorbed on glass together with hydrolyzed vanadium(IV) species and studied by a variety of techniques including grazing-incidence X-ray scattering (GIXS), small-angle X-ray scattering (SAXS), Fourier transform-infrared spectroscopy (FT-IR) and atomic force microscopy (AFM). We show that the clay platelets are dimensionally orientated in the continuous, transparent 100 nm thick film until the onset of vanadium oxides above 350 °C. Organic matter and the secondary mineral quartz limit the swelling capacity of the platelets, an indication that the stable colloids originate from a part of the native clay that could not be intercalated by aluminum cations. X-ray scattering from oriented clay films intercalated by aluminum- and mixed cerium/aluminum oxo-hydroxy cations are also investigated by the GIXS technique.Graphical abstractUnlabelled Image
       
  • Controllable synthesis of hierarchical polysilsesquioxane surfaces: from
           spheres-on-sphere to bowls-on-sphere structure
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Liangyu Lu, Jian Li, Hongwei Li, Chengtao Gao, Haibo Xie, Yuzhu Xiong, Zhu Luo, Qi Sun, Fuping Dong Hierarchical structured materials represent an interesting platform for many potential applications such as separation, catalyst and drug delivery etc. However, controlled fabrication of this special structure still remains a big challenge. In the present work, a controllable sol-gel procedure was developed to precisely fabricate polysilsesquioxane particles with bowls-on-sphere structure from mixed organoalkoxysilane precursors with sodium ligninsulfonate as surfactant and polystyrene spheres as structure-directing agents. The morphology of the particles can be fine-tuned by judiciously adjusting the ratio of two silane precursors, amount of ammonia, surfactant content and polystyrene amount. The formation mechanism of spheres-on-sphere structured polysilsesquioxane particles was explored.Graphical abstractUnlabelled Image
       
  • Self-assembled HVxOy nanobelts/rGO nanocomposite with an ultrahigh
           specific capacitance: Synthesis and promising applications in
           supercapacitors
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Tao Hu, Yanyan Liu, Yifu Zhang, Meng Chen, Jiqi Zheng, Changgong Meng Since the development of preparing vanadium oxide-graphene nanohybrids holds great promise recently, we report an HVxOy/rGO nanocomposite with novel microstructure assembling V3O7·H2O/V12O26 nanobelts and rGO nanosheets by a green facile one-step hydrothermal approach. The HVxOy nanobelts are self-assembled onto surfaces of rGO nanosheets intimately to develop a unique 3D microstructure through the in-situ and self-assembly growth mechanism. By taking full advantages of individual components, synergy has been created that HVxOy nanobelts offer abundant active sites whereas high conductive rGO nanosheets provide conductive bridges for charge transfer and act as conductive support skeletons to keep a robust structure. Evaluated as electrodes for SCs in a two-electrode system, the nanocomposite exhibits an ultrahigh specific capacitance of 813 F·g−1 at 0.5 A·g−1, a maximum power density of 3000 W·kg−1, a maximum energy density of 40.7 W·h·kg−1 as well as an ultralong lifespan up to 10,000 cycles with only 7% capacitance decline. As far as we know, the specific capacitance that we have obtained is higher than any of vanadium oxide-related materials which have been used for SCs in previous reports.Graphical abstractWe report an HVxOy/rGO nanocomposite with novel microstructure assembling V3O7·H2O/V13O26 nanobelts and reduced graphene oxide (rGO) through a green facile one-step hydrothermal process. The nanocomposite exhibits an ultrahigh specific capacitance (813 F·g−1 at 0.5 A·g−1), a maximum energy density (40.7 W·h·kg−1), a maximum power density (3000 W·kg−1) and a remarkable cycling stability (93% retention in specific capacitance after 10,000 cycles).Unlabelled Image
       
  • An architecture of dandelion-type Ni-Co3O4 microspheres on carbon nanotube
           films toward an efficient catalyst for oxygen reduction in zinc-air
           batteries
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Shengjuan Li, Kun Wu, Lei Li, Lulu Suo, Yufang Zhu Sluggish kinetics of oxygen reduction reaction (ORR) at an air cathode of a rechargeable zinc-air battery (ZAB) is a serious obstacle hindering the development of the ZAB. In the present work, hierarchical Co3O4 nanowires doped with Ni atoms (Ni-Co3O4) were fabricated and self-assembled into dandelion-type microspheres on CNT films (Ni-Co3O4/CNTs) by a hydrothermal method. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscope (HRTEM) results verified the successful incorporation of Ni atoms into the Co3O4 lattice. Electrochemical measurements, such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques, revealed that the dandelion-type Ni-Co3O4/CNT composite could greatly enhance the catalytic activity and ORR durability of the air cathode in the O2-saturated 0.1 M KOH electrolyte. Here, we report that the synergistic effect between Ni-Co3O4 nanowires and CNTs could greatly improve the stability and electrochemical performance of Co3O4 catalysts. Especially, the Ni-Co3O4/CNTs prepared at 160 °C exhibited the best catalytic capability and long-term durability (93.34% after 8.3 h) in the present work, which are better in comparison with the performance of the 20 wt% commercial Pt/C electrode in ZABs.Graphical abstractUnlabelled Image
       
  • MOF-derived rod-like composites consisting of iron sulfides embedded in
           nitrogen-rich carbon as high-performance lithium-ion battery anodes
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Hao Wang, XuKun Qian, Hongyu Wu, Ruihua Zhang, Renbing Wu Rod-like porous composites of iron sulfides embedded in nitrogen-rich carbon have been synthesized through a simultaneous carbonization and sulfuration process of the Fe-based metal-organic framework (MIL-88) for the first time. The composites exhibit combined advantages of the porous structure, uniform distribution of iron sulfide nanoparticles and increased conductivity. As an anode material for lithium-ion batteries (LIBs), the composites show a high reversible capacity of 936.3 mAh g−1 after 300 cycles and an exceptional high-rate capability (1128, 1056, 989, 912, 841 mAh g−1 at the current densities of 0.1, 0.2, 0.4, 0.8, and 1.6 A g−1, respectively). The results indicate that the composites could be a promising candidate for anode materials in LIBs.Graphical abstractUnlabelled Image
       
  • Further optimization of ITO films at the melting point of Sn and
           configuration of Ohmic contact at the c-Si/ITO interface
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Debajyoti Das, Laxmikanta Karmakar Progressive improvement in the TCO characteristics of ITO (In2O3:Sn) thin films grown at substrate temperature (TS ∼ 232 °C) near the melting point of Sn has been pursued via optimization of gas pressure in the RF magnetron sputtering system. The optical transmission characteristics virtually remain consistently impressive on varying the gas pressure; however, crystallinity improves with significant dominance along 〈222〉 crystallographic orientation at an optimum gas pressure of 10 mTorr. Simultaneously, enhanced doping of the In2O3 network by Sn4+ active dopants along with optimum reducing condition attained at 10 mTorr pressure in the magnetron plasma provide maxima of both concentration and mobility of the charge carriers in the ITO films prepared at each substrate temperature in the range 200–350 °C and lead to a very high TCO figure of merit characteristics. At lower gas pressure below 10 mTorr, although dopant incorporation increases, formation of enhanced number of electrically inactive dopants (Sn2+) (reduced Sn4+/Sn2+ ratio) deteriorates the electrical characteristics of the ITO films. On lowering of gas pressure beyond the optimum reducing condition in the plasma, changes in the nature of decay of the concentration and mobility of the charge carriers depend sensitively on the substrate temperature. The carrier concentration reduces rapidly at higher TS while carrier mobility diminishes significantly at lower TS. Accordingly, dopant concentration and the oxidation state of the In2O3:Sn matrix together control the carrier characteristics in a complex manner which is again sensitively influenced by the substrate temperature and the working gas pressure of the magnetron plasma. Significantly superior ohmic contact of the optimum ITO film with c-Si wafer evolves due to narrowing of the junction barrier height (φB) arising by virtue of increased carrier concentration in ITO, thanks to effective doping by Sn4+. Improved c-Si/ITO junction characteristics admit supplementary application feasibility of ITO films in devices fabrication, particularly as transparent electrodes in c-Si p-n junction solar cells.Graphical abstractUnlabelled Image
       
  • Fabrication of scalable and flexible bio-photoanodes by electrospraying
           thylakoid/graphene oxide composites
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): HyeIn Shin, Teayeop Kim, IlHo Seo, SeonIl Kim, Yong Jae Kim, Hyeonaug Hong, Yunjeong Park, Hyung Mo Jeong, Kyunghoon Kim, WonHyoung Ryu For extraction of photosynthetic electrons (PEs) from plant cells and algal cells, there have been many approaches using living algal cells or isolated photosynthetic apparatus such as photosystem II, photosystem I, and thylakoid membranes (TMs). Among these, bio-photoanodes coated with TMs demonstrated stable performance and the possibility for their practical applications. When a TM photoanode is prepared, TMs are deposited on the surface of a metal electrode. However, since the thickness of TM films determines the light absorption and electron transfer processes, the performance of a TM bio-photoanode is significantly affected by the TM film quality. Thus, in this study, electrospraying was employed to deposit TMs with enhanced control of the thickness and uniformity of TM coating on metal electrodes. In particular, we investigated how both the quality of TM films and the magnitude of PE currents were influenced by electrospraying time, substrate motion, solution feed rates, TM concentration, and addition of graphene oxide (GO) nanosheets. Finally, to assess the feasibility of TM electrospraying as a scalable fabrication method, TMs were electrosprayed on 5 × 5 cm2 size films of indium tin oxide (ITO)-coated polyethylene naphthalate (PEN) (ITO-PEN). The coating uniformity was assessed by measuring PE currents from different locations of the TM-deposited ITO-PEN films.
       
  • Preparation and high temperature tribological properties of laser in-situ
           synthesized self-lubricating composite coatings containing metal sulfides
           on Ti6Al4V alloy
    • Abstract: Publication date: 1 July 2019Source: Applied Surface Science, Volume 481Author(s): Zhong-Yan Zhou, Xiu-Bo Liu, Su-Guo Zhuang, Xia-Hui Yang, Mian Wang, Cheng-Feng Sun The composite coatings were prepared on Ti6Al4V alloy with preplaced mixed Ni60-TiC-WS2 powders by laser cladding. The microstructure, phase compositions and tribological properties as well as the corresponding wear mechanisms of the composite coatings at 20, 300, 600, 800 °C were analyzed systematically. The results indicate that the microhardness of the composite coatings is higher than that of the substrate. Due to the synergetic effects of the in-situ synthesized solid lubricants and hard phases, both the wear resistant and friction reducing capabilities of the composite coatings are better than that of the substrate at all experimental temperatures. With the increasing of temperature, the friction coefficients and wear rates of the composite coatings and the substrate all decrease. Moreover, when the composition of cladding powders is Ni60–16.8% TiC-23.2%WS2 (wt%), the friction coefficients is 0.321 and wear rates are 2.9 × 10−5 mm3/Nm at 800 °C. The plastic deformation and delamination as well as oxidation wear are main wear mechanisms of the substrate at 800 °C, while the composite coatings is predominated by the oxidation wear and slight adhesive wear at 800 °C.
       
  • Combined effect of point defects and layer number on the adsorption of
           benzene and toluene on graphene
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Tugce Irfan Akay, Daniele Toffoli, Hande Ustunel Understanding the adsorption properties of organic molecules on graphene-based substrates is important for such applications as air and water filters. Pristine graphene is often the model substrate used in the theoretical investigations of this problem. While useful, pristine single-layer graphene is however an idealized model. In this work, we assess the effect of the presence of point defects (single vacancy, divacancy, and the Stone-Wales defect) in single-layer and bilayer graphene on the energetics of adsorption of benzene and toluene. Our calculations benchmark three different dispersion-corrected DFT schemes, namely PBE-D2, vdW-DF1, and vdW-DF2-C09. Whereas the presence of the single vacancy and the double vacancy does not appear to alter the adsorption energies of the aromatic molecules by an appreciable amount, the Stone-Wales defect and the addition of a second graphene layer stabilizes their interaction with the substrate by several tens of meV.Graphical Unlabelled Image
       
  • Use of image analysis to evaluate surface dispersion and covering
           performance of nanolime coatings sprayed on heritage material substrates
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Marcos Lanzón, Victoria E. García-Vera, Antonio J. Tenza-Abril, Valerio De Stefano Coatings are often used to reinforce the surface of monuments, although little is known about their surface dispersion and effectiveness. This paper examines the surface distribution of Ca(OH)2 nanoparticle-based coatings (Ca(OH)2-NP). The coatings were sprayed on different substrates and studied by image analysis software and microscopy. Using image segmentation techniques the phase of interest (coating) was separated from the background material and evaluated. In control surfaces, up to 92.73% of the examined area was coated by the nanoparticles. In contrast, when the treatment was sprayed on building materials the NP-coatings were preferentially deposited in weaker zones, such as cracks or defects of the surface. In this case, the processed images revealed that less than 30% of the examined surface was coated by the NP-coating.
       
  • Structure and photoluminescence properties of MoO3−x /graphene nanoflake
           hybrid nanomaterials formed via surface growth
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): B.B. Wang, X.X. Zhong, B.M. Ming, M.K. Zhu, Y.A. Chen, U. Cvelbar, K. Ostrikov An unconventional method based on hot filament chemical vapor deposition system is used to fabricate MoO3−x/graphene nanoflake hybrid structures via surface growth. MoO3 precursor is firstly reduced to MoO3−x nanoparticles mediated by N2 molecules excited by electrons emission from hot tungsten filaments. Graphene nanoflakes are then grown on the MoO3−x nanoparticles in a high-flow-rate CH4 environment through the surface conversion of hydrocarbon radicals to benzene. The results indicate that the MoO3−x nanoparticles are mainly composed of Mo4O11 and MoO2 phases and they are covered by the graphene nanoflakes formed via surface growth. This new hybrid structure emits the ultraviolet, blue, green, red and infrared light and the photoluminescence of MoO3−x nanoparticles is quenched by the graphene nanoflakes. The generation of prevailing photoluminescence bands is interpreted by the three mechanisms including the near band edge emission, the transition between two bands and the inter-valence charge transfer transition, which indicates that the intermediate band formed within the bandgap by electrons from oxygen vacancies may cause the emission. The observed photoluminescence quenching of MoO3−x nanoparticles originates from the transfer of electrons from MoO3−x nanoparticles to graphene nanoflakes under electric field formed in the MoO3−x/graphene nanoflake interface. These results not only provide further insights into the rich surface properties of graphene/molybdenum oxide hybrid structures but also contribute to the design and synthesis of new materials and the development of next-generation graphene-based optoelectronic and photovoltaic devices.Graphical abstractUnlabelled Image
       
  • 3D Electron microscopy characterization of Ag mound-like surface
           structures made by femtosecond laser surface processing
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Edwin Peng, Alexander Roth, Craig A. Zuhlke, Soodabeh Azadehranjbar, Dennis R. Alexander, George Gogos, Jeffrey E. Shield Laser processing of metal surfaces by ultrafast pulse lasers is a developing technology with many potential uses including applications in heat transfer, medical implants, and tribology. Laser processed silver surfaces has several potential applications such as biomedical devices, antibacterial surfaces, and chemical sensors. However, there is a lack of previous research on laser processing of silver is more difficult to process compared with other metals. A newly investigated dual-pulse femtosecond laser surface processing technique was capable of producing self-organized, micro/nanoscale surface features on silver where single-pulse techniques had previously failed. Three-dimensional (3D) scanning electron microscopy (SEM) was used to examine mound-like structures produced by this new method to determine their composition and formation processes. The interior microstructure revealed that the mounds were comprised mostly of resolidified Ag grains with approximately 1% porosity. Hydrodynamically-driven fluid flow was the primary process that forms these surface structures without significant oxidation.Graphical abstractUnlabelled Image
       
  • Investigation of spin Seebeck effect and magnetic damping in nanometer
           thick Ce0.5Y2.5Fe5O12 films
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Fida Mohmed, Yuan-Hua Lin The ferromagnetic insulators (FMI) involving the phonon-magnon interaction in generation of spin currents are providing new opportunities to explore the thermal to electrical conversion efficiency in comparison to electron based themoelectrics. Here, we have investigated the magnetic damping behavior and spin Seebeck effect in crystalline, highly smooth surfaced, nano-meter thick FMI Ce0.5Y2.5Fe5O12 (CeYIG) films, synthesized via pulsed laser deposition technique, for their application in spin caloritronics. The CeYIG films reveal an increase of saturation magnetization, strong magnetic anisotropy and a very low magnetic damping, optimum for investigation of pure spin currents generated via inverse spin Hall Effect. The room temperature longitudinal spin Seebeck effect (LSSE) was observed on sputtering of 8 nm thick Hall bar patterned rhodium (Rh) on CeYIG films. The magnitude of LSSE voltage obtained showed a characteristic increase and saturation of signal with the increase of film thickness, indicating the origin of spin current generation from the bulk of CeYIG film. The pure spin Hall magnetoresistance (SMR) was observed in temperature range of 5–300 K implying the LSSE observed in Rh layer is purely from the spin current generated within the FMI and free from parasitic magnetic proximity effect (MPE). The use of Rh as a normal metal for the detection of spin current can open a new window in the exploration of pure spin current related phenomena.
       
  • Hydrazine adsorption on perfect and defective fcc nickel (100), (110) and
           (111) surfaces: A dispersion corrected DFT-D2 study
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Elliot S. Menkah, Nelson Y. Dzade, Richard Tia, Evans Adei, Nora H. de Leeuw We present density functional theory calculations, with a correction for the long-range interactions, of the adsorption of hydrazine (N2H4) on the Ni (110), (100), and (111) surfaces, both defect-free planes and surfaces containing point defects in the form of adatoms and vacancies. Several low-energy adsorption structures for hydrazine on the perfect and defective surfaces have been identified and compared. The hydrazine molecule is shown to interact with the Ni surfaces mainly through the lone-pair of electrons located on the N atoms, forming either monodentate or bidentate bonds with the surface. The strength of N2H4 adsorption on the perfect surfaces is found to be directly related to their stability, i.e. it adsorbs most strongly onto the least stable (110) surface via both N atoms in a gauche-bridge configuration (Eads = −1.43 eV), followed by adsorption on the (100) where it also binds in gauche-bridge configurations (Eads = −1.27 eV), and most weakly onto the most stable (111) surface via one N–Ni bond in a trans-atop configuration (Eads = −1.18 eV). The creation of defects in the form of Ni adatoms and vacancies provides lower-coordinated Ni sites, allowing stronger hydrazine adsorption. Analysis into the bonding nature of N2H4 onto the Ni surfaces reveals that the adsorption is characterized by strong hybridization between the surface Ni d-states and the N p-orbitals, which is corroborated by electron density accumulation within the newly formed N–Ni bonding regions.Graphical abstractDFT calculations have been employed to unravel the fundamental aspects of the adsorption process of hydrazine at a range of nickel surfaces, predicting the adsorption conformations, adsorption energies, structural parameters and electronic properties.Unlabelled Image
       
  • The influence of surface pre-twinning on the friction and wear performance
           of an AZ31B Mg alloy
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Bo Mao, Arpith Siddaiah, Xing Zhang, Bin Li, Pradeep L. Menezes, Yiliang Liao Twinning is an important mode in plastic deformation of hexagonal close-packed magnesium (Mg) alloys that are promising lightweight structural metals. Recent studies show that the hardness, strength, and stretch formability of Mg alloys can be improved by pre-twinning. However, how twinning and associated microstructure influence the tribological properties of Mg alloys have not been studied systematically. In this work, a gradient twin microstructure in which the density of twins decreases with depth was introduced to an AZ31B Mg alloy plate by laser shock peening. Then sliding tests were performed on surfaces with varying twin volume fraction (TVF) under dry condition. The results shown that both the coefficient of friction (COF) and wear rate decrease with the increase of TVF. A possible mechanism responsible for the effect of surface pre-twinning on the tribo-performance of Mg alloys is proposed. In specific, it is discussed that the improved tribo-performance of Mg alloys by pre-twinning are attributed to the twinning-induced hardening effect, twin growth and saturation phenomenon, and twinning-induced surface crystallographic texture change during sliding. We envision the results in the present study can offer new insights on the designing and developing Mg alloys towards enhanced tribological performance.Graphical abstractUnlabelled Image
       
  • Decreasing the dielectric constant and water uptake by introducing
           hydrophobic cross-linked networks into co-polyimide films
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Ningning Song, Hongyan Yao, Tengning Ma, Tianjiao Wang, Kaixiang Shi, Ye Tian, Bo Zhang, Shiyang Zhu, Yunhe Zhang, Shaowei Guan The high durability of low-k value is the key parameter for the low dielectric materials especially used under humid conditions, because the k value is very sensitive to moisture. Here, to decrease the dielectric constant and improve the water resistance, a series of novel co-polyimides are successfully prepared based on cross-linkable diamine monomer by a two-step pathway combining polymerization and crosslinking reaction. It is intriguingly found that with the gradual increase content of cross-linkable group, the dielectric properties, water resistance as well as thermal and mechanical properties of those co-polyimides can be finely tuned. After cross-linking, the dielectric properties are significantly enhanced and the film surface changed from hydrophilic (78.7–89.2°) to hydrophobic (93.0–104.2°), which endow the cross-linked films with superior water resistance and high durability of low-k value. The best performance is obtained for cross-linked co-polyimide (CL-Co-PI-4) containing 30% cross-linkable group. The CL-Co-PI-4 exhibits low dielectric constant of 2.32 and dielectric loss of 0.016 at 1 MHz. Excitingly, the CL-Co-PI-4 demonstrates an extremely low water uptake of 0.051 ± 0.010%, which represents the best water resistance for the reported polyimides. After exposing to different humidity conditions for 12 h, the increasing percentage of k value is very low and below 0.84%. The CL-Co-PI-4 still keep its k value below 2.35 after equilibrating at 75% R.H. for 14 days. The excellent moisture resistance and overall performance make the CL-Co-PI-4 a good candidate for dielectric material under both dry and humid conditions.Graphical abstractA series of new fluorinated co-polyimides (CL-Co-PIs) containing hydrophobic crosslinked network were synthesized. The CL-Co-PIs exhibit significantly reduced dielectric constant, extremely low water uptake and outstanding stability of low k value at high humidity for a long time.Unlabelled Image
       
  • Electrosynthesis of polydopamine films - tailored matrices for
           laccase-based biosensors
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Luís C. Almeida, Rui D. Correia, Andreia Marta, Giuseppe Squillaci, Alessandra Morana, Francesco La Cara, Jorge P. Correia, Ana S. Viana This work explores the electrosynthesis of bio-inspired polydopamine thin films (ePDA), a route that is still overlooked in polycatecholamine coatings formation, aiming at the construction of prime matrices for biosensor applications. A combination of surface characterization techniques attests the electrochemical and optical properties, wettability, morphology, thickness and chemical composition of the ePDA films. ePDA coatings exhibit structural differences from the chemically synthesized polymers unveiling distinct polymerization pathways. We propose that fast electropolymerization forms a co-polymer enriched by chains of dopamine in the open form, in detriment of indole moieties, yielding more organized and conducting polymeric matrices. For thin coatings (ca. 3 nm), ePDA presents high electroactivity of pendent quinone groups, appropriate for covalent biomolecule interaction. The suitability of the functional ePDA films towards electrochemical biosensing was demonstrated through the catalytic activity of immobilized laccase. A clear improvement of transducing performances towards 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) detection was achieved when using the more electroactive ePDA thin film as supporting matrix, reaching a sensitivity of 342 mA M−1 cm−2. The new structural insights presented in this work, undoubtedly prove the advantage of electrosynthesis regarding molecular oxygen-driven polymerization to prepare more reproducible and organized polycatecholamines for amperometric sensors.Graphical abstractUnlabelled Image
       
  • Corrosion behavior of an Al added high-Cr ODS steel in supercritical water
           at 600 °C
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Jian Ren, Liming Yu, Yongchang Liu, Zongqing Ma, Chenxi Liu, Huijun Li, Jiefeng Wu Corrosion behavior in the supercritical water (SCW) of an Al added high-Cr oxide dispersion strengthened (ODS) steel was investigated in this study. The steel was exposed to SCW at 600 °C and 25 MPa for various exposure times up to 1000 h, and the resultant oxide layers were characterized by using weight change measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopies (XPS), scanning/transmission electron microscopy (SEM/TEM), and energy dispersive spectroscopy (EDS). The weight gain after exposure for 1000 h was 6.24 mg/dm2, indicating the superior corrosion resistance of 16Cr-3Al ODS steel to SCW. Chemical analysis of the surface oxides showed that the content of Cr-rich oxides increased with the increase of exposure time in SCW. Cross-sectional observation of the oxide scales revealed that an outer layer composed of (Cr, Fe)2O3 and an inner layer composed of Al2O3 formed on the sample surface. The growth of both outer and inner oxide layers followed the parabolic law with the increase of exposure times. The corrosion mechanism was discussed in detail based on the microstructure evolution process with exposure time in SCW.Graphical abstractUnlabelled Image
       
  • Solid-phase epitaxy and pressure-induced topotaxy of the VO2 and V2O3 thin
           films on sapphire using annealing under uniaxial compression
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Akifumi Matsuda, Yasuhisa Nozawa, Satoru Kaneko, Mamoru Yoshimoto The vanadium oxide thin films of both VO2 (V4+) and V2O3 (V3+) are phase-selectively synthesized on atomically stepped α-Al2O3 (0001) substrates by pulsed laser deposition of an amorphous precursor VxOy (V5+) phase at room-temperature, and subsequent uniaxial compressive annealing (UCA) at at 773 K under vacuum conditions. The thin films are epitaxially crystallized under uniaxial pressure, however, the process produces randomly oriented VO2-based polycrystalline when compression is not used. The VO2 (010) epitaxial film can be obtained under an applied pressure of 1 MPa; further, the V2O3 (0001) epitaxial film is formed under a pressure of more than 10 MPa. The epitaxial films indicate a distinct metal-insulator transition in which the resistivity is varied by 103 in accordance with the ρ-T measurement, i.e., the transition temperature (TC) is estimated to be ∼350 K for VO2 thin films crystallized under a pressure of 1 MPa, and ∼150 K and ∼120 K for V2O3 thin films formed under 10 and 30 MPa, respectively. Additional sequential UCA with distinct pressures of 1, 10, and 1 MPa again reveals a corresponding and reversible phase transformation between VO2 and V2O3 with consistent resistivity variation. Therefore, pressure-induced topotaxy can be proved in both the phases. The obtained epitaxial thin films demonstrate a relatively flat surface with a root-mean square roughness of
       
  • Self-assembled nitrogen-doped graphene quantum dots (N-GQDs) over graphene
           sheets for superb electro-photocatalytic activity
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Rabia Riaz, Mumtaz Ali, Iftikhar Ali Sahito, Alvira Ayoub Arbab, T. Maiyalagan, Aima Sameen Anjum, Min Jae Ko, Sung Hoon Jeong Nitrogen-doped graphene quantum dots (N-GQDs) are emerging electroactive and visible light active organic photocatalysts, known for their high stability, catalytic activity and biocompatibility. The edge surfaces of N-GQDs are highly active, however, when N-GQDs make the film the edges are not fully exposed for catalysis. To avoid this issue, the N-GQDs are shaped to branched leaf shape, with an extended network of voids, offering highly active surfaces (edge) exposed for electrocatalytic and photocatalytic activity. The nitrogen doping causes a decrease in the bandgap of N-GQDs, thus enabling them to be superb visible light photocatalyst, for degradation of Methylene blue dye from water. Photoluminescence results confirmed that by a synergistic combination of the highly conductive substrate; Carbon fabric coated graphene sheets (CF-rGO) the recombination of photogenerated excitons is significantly suppressed, hence enabling their efficient utilization for catalysis. Comparatively, uniformly coated N-GQDs showed 49.3% lower photocatalytic activity, owing to their hidden active sites. The degradation was further boosted by 30% by combining the electrocatalytic activity, i.e. electro-photocatalysis of the proposed electrode. The proposed electrode material was analyzed using TEM, FE-SEM, FTIR, AFM, and WA-XRD, whereas the stability of electrode was confirmed by TGA, tensile test, bending test, and in harsh chemical environments. The proposed photo-electrocatalyst electrode is binder-free, stable, flexible and highly conductive, which makes the electrode quite suitable for flexible catalytic devices like flexible solar cells and wearable supercapacitors.Graphical abstractNitrogen doped graphene quantum dots (N-GQDs) were self-assembled (with high porosity) on reduced graphene oxide coated carbon fabric to fabricate a highly stable visible light photocatlytically and electrocatalytically active flexible electrode for water treatment.Unlabelled Image
       
  • Nucleation of diamond micro-patterns with photoluminescent SiV centers
           controlled by amorphous silicon thin films
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Jan Fait, Štěpán Potocký, Štěpán Stehlík, Jiří Stuchlík, Anna Artemenko, Alexander Kromka, Bohuslav Rezek Selective deposition of diamond allows bottom-up growth of diamond nanostructures and nanoscale devices. However, it remains challenging to reduce the size of the patterns and to suppress parasitic spontaneous nucleation. We show here that thin layers of hydrogenated amorphous silicon (down to 40 nm) efficiently suppress spontaneous nucleation of diamond. The suppression of diamond nucleation does not depend on the substrate materials below hydrogenated amorphous silicon (Si, SiO2, Pt, Ni). We attribute the suppressed diamond nucleation to surface disorder on atomic scale. By using a structured layer of hydrogenated amorphous silicon, highly selective growth of diamond micro-patterns with optically active SiV centers by low-temperature microwave plasma chemical vapor deposition is achieved.Graphical abstractUnlabelled Image
       
  • In situ X-ray observations of pure-copper layer formation with blue direct
           diode lasers
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yuji Sato, Masahiro Tsukamoto, Takahisa Shobu, Yoshinori Funada, Yorihiro Yamashita, Takahiro Hara, Masanori Sengoku, Yu Sakon, Tomomasa Ohkubo, Minoru Yoshida, Nobuyuki Abe A blue direct diode laser metal deposition system, which uses multiple lasers, was developed to realize a high-quality coating layer with a dense, fine structure and high purity. To clarify the formation mechanism of the pure copper layer, the formation process using a blue direct diode laser system was observed using in situ X-ray observations. The stainless steel 304 substrate melts, generating bubbles in the molten pool at a laser power density of 7.2 × 103 W/cm2 and a scanning speed of 3.0 mm/s. At a laser scanning speed of 9.0 mm/s, the bubbles disappear because only a slightly molten pool is formed on the surface of the substrate. The bubble amount and penetration depth depend on the laser input energy with a blue direct diode laser. By controlling the amount of input energy, a copper coating is produced minutely without a weld penetration.
       
  • Static and dynamic tuning of surface plasmon resonance by controlling
           interparticle distance in arrays of Au nanoparticles
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Ayana Mizuno, Atsushi Ono Static and dynamic tuning of plasmonic resonance in arrays of Au nanoparticles fabricated using self-assembly method on stretchable substrates was investigated. Static tuning was realized by altering the self-assembly conditions, which allowed varying average separation between Au nanoparticles and tune their collective plasmon mode with a broad wavelength range. Dynamic tuning was achieved by applying uniaxial or biaxial strain to the Au nanoparticle arrays on a stretchable substrate. Plasmonic tunability and anisotropy were demonstrated by strain-controlled stretchable substrate. Spectral shifts of collective plasmon modes with strain were found to depend on incident polarization and interparticle distance. The obtained plasmonic nanostructures can be applied as mechanically tunable plasmonic optical filters and sensors.
       
  • Effect of iron doping on the properties of SnO2
           nano/microfibers
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): E. Mudra, I. Shepa, O. Milkovic, Z. Dankova, A. Kovalcikova, A. Annušová, E. Majkova, J. Dusza The present work is focused on the preparation and characterization of SnO2-based fibers suitable for gas sensing application. The pure SnO2 fibers were synthesized together with Fe3+-doped and Fe3O4 nanoparticles-doped SnO2 fibers by needle-less electrospinning technique and followed the calcination process. Fe modification of SnO2 fibers was prepared by the simple addition of Fe(NO3)3.9H2O or Fe3O4 nanoparticles to the spinning solution. Subsequently, the individual fibers were deposited using the spin coating process on the silicon substrate to form structured fiber films. The prepared fibers and films were characterized by SEM, TEM, XRD, BET, and UV–Vis. The calcination of individual fibers led to the formation of tube-like or full fiber structures in dependence on the doping type of the spinning solution. The full fiber structures with a higher surface area and decreased grain sizes were obtained after doping the precursor solution with Fe3+. On the other hand, doping with Fe3O4 nanoparticles does not have a significant effect on the fibers morphology compared to pure SnO2 tube-like fibers. The resulting morphology of the fibers has a substantial effect on the thickness, roughness, and compactness of the structured final films.Graphical abstractUnlabelled Image
       
  • Dewetting behavior of Ag in Ag-coated Cu particle with thick Ag shell
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Eun Byeol Choi, Jong-Hyun Lee With the aim of application as either a conductive filler or a sinter-bonding material with enhanced antioxidation properties, Ag-coated Cu (Cu@Ag) particles with thick Ag shells were fabricated and heated at 220 °C for 10 min in air to observe the dewetting behavior of the thick Ag shell. The fabricated Cu@Ag particles were spherical with the average size of 2 μm, and the Ag shell was 250–400 nm in thickness, comprising a mixed Ag-Cu layer and a dense Ag layer. As the heat-treatment time increased, the Cu@Ag particles were aggregated by forming numerous Ag nodules covering the surface of the particle. Dewetting in the thick Ag shell occurred from 4 min and only in the outer layer of the Ag shell even after 10 min of heat-treatment. In addition, the thickness of the dewetting layer and the mixed Ag-Cu layer were increased because the outward diffusion of Cu and Ag were increased proportionally with the time. However, because the dense Ag layer remained even after the dewetting of the Ag shell and the formation of the mixed Ag-Cu layer, the Cu@Ag particles were not oxidized after heating at 220 °C for 10 min in air.
       
  • Effect of TiC particle size on high temperature oxidation behavior of TiC
           reinforced stainless steel
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yeong-Hwan Lee, Sungmin Ko, Hyeonjae Park, Donghyun Lee, Sangmin Shin, Ilguk Jo, Sang-Bok Lee, Sang-Kwan Lee, Yangdo Kim, Seungchan Cho For the development of a lightweight, high-strength, and oxidation-resistant steel matrix composite, titanium carbide (TiC) reinforced SUS431 metal matrix composites (MMCs) were proposed in this study. TiC–SUS431 composite, which is 25.5% lighter than SUS431, was successfully fabricated by a liquid pressing infiltration (LPI) process. The TiC particles are homogenously distributed in the SUS431 matrix without apparent pores or impurities. Effect of TiC particle size on the anti-oxidation properties of the composites was also investigated in the research. The mass gain of the tested TiC(1 μm)–SUS431 composite, held at 700 °C for 50 h in an air environment, decreased by about 90% compared to that of the TiC(3 μm)–SUS431 composite, which indicates improved oxidation resistance originating from the formation of a thermally stable thin Ti oxides on the composite.Graphical abstractUnlabelled Image
       
  • Activation energy of oxygen diffusion: A possible indicator of
           supercurrents through YBa2Cu3O7 grain boundaries
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Tian-Ge Wang, Jin-Jin Cao, Xiao-Fan Gou Oxygen diffusion is the main transportation form during the preparation process of polycrystalline superconductor YBa2Cu3O7 (YBCO) thin films. Especially the diffusion of oxygen ions in grain boundaries (GBs) can lead to the formation of oxygen vacancies, and finally have an impact on the critical current density (Jc) of YBCO conductors. To deeply understand the supercurrent-limiting mechanism of GBs, for an YBCO bicrystal (containing a single GB), in this article we intensively studied the diffusion of oxygen ions through GB region by molecular dynamics simulations. The calculated results show that the oxygen diffusion in the YBCO bicrystals can be enhanced in GBs, and specifically which is closely related to the grain boundary angle (θ). The most interesting finding is that the activation energy of oxygen diffusion shows an exponential fall with the grain boundary angle, which is exactly consistent with the relation of the critical current density versus the grain boundary angle (Jc ~ θ) in GBs. We firmly believe that the activation energy of oxygen diffusion should have an essential relevance with the Jc especially in YBCO GBs, and can be as an indicator for predicting supercurrents. For these results we further gave an in-depth discussion.
       
  • Defect induced broadband visible to near-infrared luminescence in ZnAl2O4
           nanocrystals
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Megha Jain, Manju, Abhiram Gundimeda, Sanjay Kumar, Govind Gupta, Sung Ok Won, Keun Hwa Chae, Ankush Vij, Anup Thakur Materials emitting over a broad range of wavelengths have been gaining attention consistently owing to their potential applications. ZnAl2O4 has been an attractive material due to its robust luminescence properties. Herein, we report white and intense near-infrared emission, simultaneously, in undoped ZnAl2O4 nanocrystals at a relatively lower temperature (550 ∘C) than reported earlier. Emission is accompanied by various types of shallow and deep donor/acceptor defects, for instance, ionic vacancies and antisite defects existing in the crystal lattice. Switching of white to blue color is observed with annealing owing to rearrangement of defects. Rietveld refinement of X-ray diffraction patterns confirm the presence of multiple defects in the crystal lattice. Transmission electron microscopic analysis has revealed the change in morphology from spherical to polyhedron and increase in crystallite size on annealing. Suitable values of illuminating engineering society colorimetric parameters such as fidelity index, luminous efficiency of radiation, color gamut etc. predict its potential applications in lighting and bioimaging.Graphical abstractUnlabelled Image
       
  • Synthesis of NaX zeolite-graphite amine fiber composite membrane: Role of
           graphite amine in membrane formation for H2/CO2 separation
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Priyanka Roy, Nandini Das Pore surface modification of zeolite membrane is a challenging area to combat the trade-off between the high flux and high selectivity of the gas separation membrane. Herein we report facile method of pore along with defects modification of NaX zeolite membrane by incorporating graphite amine (Ga) into the membrane structure. Permeation properties of different membranes were evaluated by single gas permeance of H2, CO2 and separation factors for mixed gas H2-CO2 with different mixture ratio. These studies were done at room temperature and 100–300 kPa feed pressure. The results show that Ga is not only active for defect removal of NaX membrane but also enhanced the formation of NaX zeolite from mother sol. In addition, presence of graphite amine into NaX zeolite membrane increase the permeance of H2 from 5.1 × 10−7 mol m−2 s−1 kPa−1 to 36.5 × 10−7 moll m−2 s−1 kPa−1 with increase of feed pressure 100–300 kPa feed pressure due to its hydrophobic properties and separation factor of H2-CO2 enhanced up to 31 for H2-CO2 mixture gas compared to literature reported value 6.5 for FAU membrane over 3-aminopropyltriethoxysilane functionalized alumina. Herein for the first time we report that graphite amine catalyzes for the formation of NaX zeolite in addition to pore modification in zeolite membrane.Graphical abstractGa fiber woven structure in NaX–Ga composite membrane minimizes defects and shows enhanced separation factor for H2-CO2 mixture gas.Unlabelled Image
       
  • New protein-resistant surfaces of amphiphilic graft copolymers containing
           hydrophilic poly(ethylene glycol) and low surface energy fluorosiloxane
           side-chains
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Lingmin Yi, Kai Xu, Guanying Xia, Jiawei Li, Weixiang Li, Ying Cai Methacryloyl-terminated poly[methyl(3,3,3-trifluoropropyl)siloxane] (PMTFPS-MA) macro-monomers with controlled segment length were designed and synthesized by anionic ring-opening polymerization of 1,3,5-trimethyl-1,3,5-tri(3′,3′,3′-trifluoropropyl)cyclotrisiloxane (F3). Then, a series of novel amphiphilic fluorosiloxane-containing graft copolymers were prepared using PMTFPS-MA, poly(ethylene glycol) methyl ether methacrylate (PEG-MA) and methyl methacrylate (MMA) as the co-monomers, and their surface properties and protein-resistant performance were investigated. It was found that the composition of amphiphilic graft copolymers would play an important role in the protein-resistant properties. When the copolymers contain 65.5 wt% PEO segments and 6.4 wt% PMTFPS segments, the coating surface exhibits strong protein-resistant property and shows almost no protein adsorption on it. Based on the surface analysis of amphiphilic graft copolymer films both in dry and wet conditions, the protein-resistant property of amphiphilic copolymers can be owing to the transition from a hydrophobic surface to hydrophilic surface with highly efficient water-driven PEO surface migration. The PEO segments are utilized to prevent protein adsorption whereas the low surface energy PMTFPS segments are utilized to drive away the adsorbed proteins.Graphical abstractUnlabelled Image
       
  • The surface-modified effects of Zn anode with CuO in Zn-air batteries
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Young-Jin Kim, Kwang-Sun Ryu Copper oxide nanoparticles (CuO-NPs) can be used to prevent dendrite formation and increase the reversibility of Zn anode. The zinc surface was modified with CuO and the Cu source used was copper nitrate. It also contained 0.1 wt%, 0.5 wt%, 1.0 wt%, and 3.0 wt% CuO by weight of zinc. The morphologies of the Zn surfaces modified by CuO-NPs were observed by scanning electron microscopy (SEM). The structures of the surface-modified and bare zinc powders showed that the modification did not affect the crystal structure, but Cu 2p details from XPS were detected in the form of a satellite peak of CuO. SEM images of CuO modified on the zinc particles revealed homogeneous modification on the Zn surface. The use of an appropriate CuO particle can prevent direct contact with Zn and KOH electrolyte, and minimize side reactions within the batteries. In a DC-cycling test, the 0.1 wt% CuO-modified Zn anode powder provided the best cycle performance up to 24 h. A surface-modified zinc electrode can increase reversibility and reduce self-discharge with electrochemical stability. The results suggest that surface modification is effective for improving the comprehensive properties of Zn anode materials for Zn-air batteries.Graphical abstractUnlabelled Image
       
  • Design of high efficient oxygen reduction catalyst from the transition
           metal dimer phthalocyanine monolayer
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yanan Meng, Cong Yin, Kai Li, Hao Tang, Ying Wang, Zhijian Wu Due to the large surface area, unique atomic configurations and dispersed metal sites, metal-organic porous monolayers provide a promising strategy for catalysis. Among them, the transition metal dimer phthalocyanine (TM2Pc) monolayer is one of the interesting members. Herein, we studied the oxygen reduction reaction (ORR) of TM2Pc with a series of transition metal dimers (M = Mn-Cu and Ru-Pd) by using the density functional theory. Volcano plot suggests that Fe2Pc has the best ORR activity. This is also confirmed by thermodynamic and kinetic study. Among the studied TM2Pc, Fe2Pc has the highest working potential of 0.98 V (smallest overpotential of 0.25 V), larger than 0.78 V for pure Pt. The energy barrier calculations show that for Fe2Pc, the rate-determining step is the *OOH hydrogenation to form *OH + *OH with an energy barrier of 0.25 eV, much smaller than 0.80 eV for pure Pt. Therefore, Fe2Pc has good ORR activity compared with pure Pt. These results also indicate that the introduction of transition metal dimer on phthalocyanine monolayer would provide a novel strategy for the design of high efficient ORR catalysts.Graphical abstractFe2Pc monolayer exhibits the highest catalytic activity for ORR and is promising catalyst for ORR.Unlabelled Image
       
  • Hydrothermal reduction of commercial P25 photocatalysts to expand their
           visible-light response and enhance their performance for photodegrading
           phenol in high-salinity wastewater
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Ting Wang, Yan-ling Zhang, Jia-hao Pan, Bing-rui Li, Li-guang Wu, Bo-qiong Jiang This study aimed to expand the visible-light response of commercial titanium dioxide (TiO2, P25) photocatalysts using surface modification by hydrothermal reduction with various reductants to improve their photocatalytic performance for phenol degradation in high-salinity wastewater under room visible-light irradiation. Structure characterization results for different reduced P25 photocatalysts show that hydrothermal reduction cannot only generate disordered crystalline shell–core structures on the catalyst surface but also introduce several Ti3+ into the photocatalysts, facilitating the visible-light response of reduced P25. The moderate conditions of hydrothermal reduction not necessarily destroyed the inner crystalline structure of P25 to form amorphous TiO2 as deep trapping sites for photogenerated charges, different from the results for the reduced P25 obtained by hydrogeneration reduction (P25–H2). Therefore, the reduced P25 obtained by hydrothermal reduction with Zn as reductant featured a slightly higher photocatalytic activity for phenol than P25–H2 under visible-light irradiation, although P25–H2 exhibited a smaller Eg and stronger visible-light absorbance. The highest removal rate for phenol of reduced P25 within 5 h reached up to 87.5% and considerably exceeded that of P25–H2 (60.0% removal rate of phenol). Apart from the reduction capability of metals, the solubility of the corresponding metal hydroxide plays a major role in P25 reduction in the hydrothermal process. The water-insoluble metal hydroxide precipitates on the metal surface and inhibits the reduction between metal and P25, thereby decreasing the photocatalytic performance of reduced P25 for phenol excited by room visible-light.Graphical abstractUnlabelled Image
       
  • Catalytic hydrogenation of p-nitrophenol using a metal-free catalyst of
           porous crimped graphitic carbon nitride
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Ting Huang, Yongsheng Fu, Qiong Peng, Chunyan Yu, Junwu Zhu, Aiping Yu, Xin Wang Currently, most catalysts for hydrogenation of p-nitrophenol employ the size- and shape-controlled noble metal (Au, Ag, Pd and Pt, etc.) nanomaterials or which supported on appropriate supports. Nevertheless, their high prices and low reserves severely limit the industrial application. Here we report a metal-free catalyst of porous crimped graphitic carbon nitride, which is prepared by calcining dicyandiamidine (a new precursor). This catalyst possesses abundant amino groups on the terminal edges of in-planar tri-s-triazine ring and large specific surface area, thus exhibits extremely high catalytic activity for catalytic hydrogenation of p-nitrophenol in the presence of NaBH4, which can be equivalent to (or even higher than) those of the previously reported noble metal-based catalysts. Interestingly, the kinetics analysis of hydrogenation of p-nitrophenol to p-aminophenol shows that the reaction follows the zero-order kinetics, different from the pseudo-first-order kinetics for the hydrogenation over the noble metal-based catalysts. In fact during reaction process, the catalytic oxidation of BH4− and the generation of hydride ion (H−) occur on the catalyst surface, while the hydrogenation process of p-nitrophenol proceeds in the bulk solution. This work establishes a new understanding of the hydrogenation process of p-nitrophenol using the metal-free catalyst based on graphitic carbon nitride.Graphical abstractUnlabelled Image
       
  • Hierarchical flower-like structures composed of cross-shaped vanadium
           dioxide nanobelts as superior performance anode for lithium and sodium
           ions batteries
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Hang Su, Kuan Chang, Yuhang Ma, Dingcheng Yang, Canpei Wang, Kai Zhang, Dan Li, Jianmin Zhang Until now, both lithium ion batteries (LIBs) and sodium ion batteries (SIBs), have been broadly researched, which is either attractive or challenging. Among the transition metal oxides (TMOs), VO2 (B), with a high theoretical capacity and appealing rate capability, has been studied as anode materials. In our work, the flower-like structures composed of cross-shaped VO2 (B) nanobelts were synthesized via a simple solvothermal method. The electrochemical properties were investigated for lithium storage (with capacities of 529.2 mA h g−1 at current density of 0.2 A g−1 after 200 cycles and 683.1 mA h g−1 at 1 A g−1 after 1000 cycles) and sodium storage (225.2 mA h g−1 at 0.2 A g−1 after 200 cycles, 150 mA h g−1 at 5 A g−1). The reaction mechanisms were explored by ex-situ XRD and ex-situ TEM, which reveals the intercalation mechanism for both LIBs and intercalation combined with conversion mechanisms for SIBs.
       
  • Thermodynamic analysis of molecular simulations of N2 and O2 adsorption on
           zeolites under plateau special conditions
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yaoguo Fu, Yingshu Liu, Xiong Yang, Ziyi Li, Lijun Jiang, Chuanzhao Zhang, Haoyu Wang, Ralph T. Yang Adsorption thermodynamics of N2 and O2 on two most commonly used zeolites (5A and Li-LSX) under plateau special conditions of wide ranges of temperature (238–298 K) and pressure (0–300 kPa) for pressure swing adsorption (PSA) oxygen production were studied based on molecular simulations and theoretical model fitting. Adsorption isotherms for each adsorbate-adsorbent pair at different temperatures were fitted by Langmuir, Freundlich and Sips models, obtaining equilibrium parameters including adsorption capacity, strength, heterogeneity and N2/O2 selectivity. Thermodynamic parameters such as Gibb's free energy, enthalpy, and entropy changes were numerically derived, and isosteric adsorption heats and distributions of potential energy were simulated. The results suggest that the adsorption capacity and affinity follow the order of N2-Li-LSX > N2-5A > O2-5A > O2-Li-LSX, leading to higher N2/O2 selectivity on Li-LSX compared to 5A. For Li-LSX, N2/O2 selectivity increases significantly with temperature above 273 K due to the difference in adsorption thermodynamics of N2 and O2 varying with temperature in terms of different adsorption heterogeneities. For 5A, the homogeneous distributions of N2 and O2 as well as the wide scopes of affinities from Na+ and Ca2+ exhibit N2/O2 selectivity with negligible temperature dependence, which is beneficial for stable oxygen production with a fixed PSA process under large day-and-night temperature difference. This study provides theoretical basis for obtaining an optimal balance between efficiency and stability of oxygen production by using a proper mixture of Li-LSX and 5A.
       
  • Multifunctional magnetic superhydrophobic carbonaceous aerogel with
           micro/nano-scale hierarchical structures for environmental remediation and
           energy storage
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yeqiang Lu, Zixuan Niu, Weizhong Yuan Multifunctional magnetic superhydrophobic carbonaceous (MSC) aerogel with hierarchically porous structures is successfully prepared via carbonization process using disposable cotton balls followed by surface-coating of Fe3O4 particles and post hydrophobic-modified treatment with long-chain silanes. The developed MSC aerogel demonstrates ultralow density (99.9%), robust superhydrophobicity and superoleophilicity (θwater = 160.5°, θoil = 0°, a rolling contact angle of 1.8°). The aerogel has excellent absorption capacity (61–113 g/g) for various oily liquids, and can be manipulated above the contaminated water under magnetism. More importantly, benefitting from its fire resistance and compressibility, the MSC aerogel can be recycled easily using distillation, squeezing and combustion, depending on the kinds of contaminants. Furthermore, this material can be a good candidate for supercapacitors. All these features make the material a versatile and comprehensive material for various applications in oil spill cleanup and energy storage.Graphical abstractUnlabelled Image
       
  • Synthesis of Ti3C2/Fe3O4/PANI hierarchical architecture composite as an
           efficient wide-band electromagnetic absorber
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yan Wang, Xiang Gao, Lijuan Zhang, Xinming Wu, Qiguan Wang, Chunyan Luo, Guanglei Wu A hierarchical architecture of Ti3C2/Fe3O4/PANI composite as a high-efficiency microwave absorber was synthesized using HF etching, coprecipitation and in-situ polymerization route. Layered Ti3C2 was used as a matrix material with high surface area and a network offering more paths of electron transfer. The adding of PANI and Fe3O4 can generate an outstanding microwave absorption property because of enhanced interfacial polarization, strong attenuation loss and excellent impedance matching. The hierarchical Ti3C2/Fe3O4/PANI ternary composite shows a strongest reflection loss (RL) of −40.3 dB at 15.3 GHz, which is higher than those of Fe3O4 and Ti3C2/Fe3O4. Furthermore, it also displays broad absorption frequency band, possessing the efficient absorption bandwidth (
       
  • Decreased bacterial colonization of additively manufactured Ti6Al4V
           metallic scaffolds with immobilized silver and calcium phosphate
           nanoparticles
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Maria Surmeneva, Ales Lapanje, Ekaterina Chudinova, Anna Ivanova, Andrey Koptyug, Kateryna Loza, Oleg Prymak, Matthias Epple, Franka Ennen-Roth, Mathias Ulbricht, Tomaž Rijavec, Roman Surmenev The design of an ideal bone graft substitute has been a long-standing effort, and a number of strategies have been developed to improve bone regeneration. Electron beam melting (EBM) is an additive manufacturing method allowing for the production of porous implants with highly defined external dimensions and internal architectures. The increasing surface area of the implant may also increase the abilities of pathogenic microorganisms to adhere to the surfaces and form a biofilm, which may result in serious complications. The aim of this study was to explore the modifications of Ti6Al4V alloy scaffolds to reduce the abilities of bacteria to attach to the EBM-manufactured implant surface. The layers composed of silver (Ag), calcium phosphate (CaP) nanoparticles (NPs) and combinations of both were formed on the EBM-fabricated metallic scaffolds by electrophoretic deposition in order to provide them with antimicrobial properties. The assay of bacterial colonization on the surface was performed with the exposure of scaffold surfaces to Staphylococcus aureus cells for up to 17 h. Principal component analysis (PCA) was used to assess the relationships between different surface features of the studied samples and bacterial adhesion. The results indicate that by modifying the implant surface with appropriate nanostructures that change the hydrophobicity and the surface roughness at the nano scale, physical cues are provided that disrupt bacterial adhesion. Our results clearly show that AgNPs at a concentration of approximately 0.02 mg/сm2 that were deposited together with CaPNPs covered by positively charge polyethylenimine (PEI) on the surface of EBM-sintered Ti6Al4V scaffolds hindered bacterial growth, as the total number of attached cells (NAC) of S. aureus remained at the same level during the 17 h of exposure, which indicates bacteriostatic activity.Graphical abstractUnlabelled Image
       
  • Surface-engineered Li4Ti5O12 nanoparticles by TiO2 coating for superior
           rate capability and electrochemical stability at elevated temperature
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Binitha Gangaja, Shantikumar Nair, Dhamodaran Santhanagopalan Lithium ion batteries are dominating the energy storage market owing to its capability in powering portable electronics to electric vehicles. However, the power capabilities of these batteries are still relatively low limiting their applications in fast charging. In this paper, we report a strategy in elevating the rate capability of lithium titanate (Li4Ti5O12 - LTO), one of the safest anode materials known. We demonstrate that a simple chemical method of coating titania (TiO2) on lithium titanate nanoparticles followed by low temperature annealing yields a superior anode to bare-LTO. The surface coated electrode exhibits high discharge capacity of 212 mAh/g at 10C rate while the bare-LTO deliver only 138 mAh/g. Likewise, the surface engineered electrode displays excellent ultra-high rate capability (150C) and long cycling stability of 1000 cycles (at 60C rate). Impedance spectroscopy results confirm that the charge transfer resistance in surface engineered sample (CS-3) is comparatively lower than the bare-LTO electrode. Ex situ TEM investigation shows that the titania inhibits surface phase transition when cycled at elevated temperature which could be advantageous as it is a manifestation of minimal gassing in the batteries.Graphical abstractUnlabelled Image
       
  • Carbon quantum dots/TiO2 nanosheets with dominant (001) facets for
           enhanced photocatalytic hydrogen evolution
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yulei Sui, Ling Wu, Shengkui Zhong, Qingxia Liu Carbon quantum dots/TiO2 nanosheets with a majority of (001) facet (CQDs/TiO2-001) samples are successfully prepared via a facile method. Compared to TiO2-001 and CQDs/P25, the synthesized CQDs/TiO2-001 presents a remarkably higher photocatalytic activity for H2 evolution with a considerable stability. XRD, XPS, HRTEM, FESEM, FTIR, Photoluminescence (PL) spectroscopy, Fluorescence spectroscopy and UV–visible reflectance spectroscopy are adopted to investigate the morphology, structure and properties of synthesized CQDs/TiO2-001. The mechanism of the improved photocatalytic activity over CQDs/TiO2-001 is also investigated. The results show that the improved photocatalytic activity over CQDs/TiO2-001 can be attributed to the synergistic effects of TiO2-001 and CQDs: the highly exposed (001) facets of TiO2-001 promote the transportation of photogenerated electrons and the loading of CQDs restrains the recombination of electrons-holes on (001) facets. Meanwhile, the visible-light absorption is extended because the CQDs serve as a photosensitizer and sensitize TiO2-001 through the newly formed TiOC bond between the CQDs and TiO2-001.Graphical abstractUnlabelled Image
       
  • Electronic, magnetic properties of 4d series transition metal substituted
           black phosphorene: A first-principles study
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yusheng Wang, Nahong Song, Na Dong, Yafeng Zheng, Xiaohui Yang, Weifen Jiang, Bin Xu, Jianjun Wang To enrich the electronic and induce useful magnetic properties of the monolayer black phosphorene (BP) we study the structural, electric and magnetic properties of substitutional 4d transition metal (TM) impurities in BP by means of first-principles methods. In the 4d single TM atom doped cases, the magnetic moment shows oscillation character with the increasing of the 4d shell valence electrons, which is attributed to the P-p and TM-d orbital hybridization mechanism. We found no spin polarized state in the Y, Nb, Tc, Rh and Cd doped BP. In other systems, the spin polarized states are found. Importantly, the 4d TMs also enrich the electronic properties of BP, such as half-metallic, metallic and semiconducting features. For two same TMs doped BP, the 2Mo doping on the both sides of BP show a half-metal character. Only 2Nb doped BP shows diluted magnetic semiconductor (DMS) character. Interestingly, for two different TMs doped BP, the DMS characteristics can be found in the MoY-BP, MoNb-BP, MoTc-BP and MoRh-BP cases. It is worth to be expected that doping with different 4d TMs is a promising method to realize the DMS properties of BP.
       
  • Catalytic de-chlorination of products from PVC degradation by magnetite
           (Fe3O4)
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Oday H. Ahmed, Mohammednoor Altarawneh, Mohammad Al-Harahsheh, Zhong-Tao Jiang, Bogdan Z. Dlugogorski This contribution provides a systematic theoretical thermo-kinetic study of the initial reactions between Fe3O4(111) surface, as a representative model for metal oxides in electric arc furnace dust (EAFD) with HCl and selected chlorinated hydrocarbons, as major products from thermal degradation of PVC. Formation of the experimentally observed iron chloride occurs by subsequent dissociative addition of HCl molecules followed by H migration into a surface hydroxyl group. We provided Arrhenius parameters for reactions dictating the conversion of iron oxide into its chloride. In the course of the interaction of chlorinated alkanes and alkenes with the Fe3O4 surface, the opening channel in the dissociative addition route requires lower activation barriers in reference to the direct HCl elimination pathways. However, sizable activation barriers are encountered in the subsequent β CH bond elimination step. Estimated electronic charges confirm the nature of surface FeCl bonds as Lewis acid−base pair. The obtained accessible reaction barriers for reactions of chlorinated alkanes and alkenes with the title iron oxide demonstrate that the latter serve as active catalysts in producing clean olefins streams from chlorinated alkanes. Results from this study should be instrumental to understand, on a precise atomic scale, mechanisms operating in fixation of halogens on transitional metal oxides; a viable thermal recycling approach for polymeric materials laden with halogenated constituents.Graphical abstractUnlabelled Image
       
  • Adsorption characteristics of Co-anchored different graphene substrates
           toward O2 and NO molecules
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Jinglan Dong, Zhengyang Gao, Weijie Yang, Ang Li, Xunlei Ding The adsorption characteristics of O2 and NO on Co-anchored different graphene-based substrates (single vacancy, double vacancy and N atoms doped) have been investigated using density functional theory. The geometric stability of the single atom catalysts, adsorption configurations of gas molecules, adsorption energies, electronic structure and thermodynamic analysis have been performed. Co/vacancy-graphene shows high thermodynamic stability through calculating and comparing the binding energy of Co-anchored single atom catalysts and the cohesive energy of Co bulk. For O2 adsorption, it prefers to form two chemical bonds with the Co atom, and electron transfer dominates the formation of the strong chemical ionic bonds. While on Co single and double vacancy graphene substrates, N atom in NO invariably bonds to the Co atom, with electron transfer and orbital hybridization dominating the process of bonding formation respectively, afterwards ionic and covalent bonds formed between gas molecule and the metal atom. Additionally, electro-negativity and partial d-band centre are good descriptors of adsorption energies and can well reveal the relationship of adsorption energy with adsorption activity and the electronic structure. Co/single vacancy-graphene substrate with three pyridine nitrogen atoms (Co/SV-N123) is a promising catalyst in catalytic oxidation of NO. The results can provide reference for the further study of the NO oxidation mechanism on the Co/GN surface as well as the new non-noble-metal catalysts design.
       
  • Deep eutectic solvents appended to UiO-66 type metal organic frameworks:
           Preserved open metal sites and extra adsorption sites for CO2 capture
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Zhong Li, Wenzhe Sun, Chong Chen, Qirui Guo, Xue Li, Mengwei Gu, Nengjie Feng, Jing Ding, Hui Wan, Guofeng Guan Targeting CO2 capture at low pressure due to the partial pressure of CO2 in flue gases (0.01 MPa–0.02 MPa), a facile method was constructed to build functional UiO-66 structure via mixing ligands of terephthalic acid and 1,2,4-benzenetricarboxylic acid. The free -COOH from 1,2,4-benzenetricarboxylic acid could graft quantitative and dispersive deep eutectic solvents onto UiO-66 with reserved open metal sites for CO2 adsorption. Compared to 1,3,5-benzenetricarboxylic acid, mixing ligands by 1,2,4-benzenetricarboxylic acid preserved the stability of UiO-66 structure, which was more suitable for CO2 capture from flue gases. The active -NH2 and -OH groups from incorporated DES synergized with the intrinsic open metal sites to enhance the CO2 uptake at low pressure and improve adsorption selectivity of CO2/N2. At 298 K, the CO2 uptake of DES@UiO-66-COOH(0.05) was increased by 26% at 1 bar and 50% at 0.15 bar compared to UiO-66. In addition, the selectivity of CO2/N2 for DES@UiO-66-COOH(0.05) was 24.7 times as high as UiO-66 at low pressure. The strong interaction between guest CO2 and modified UiO-66 was confirmed by higher isosteric heats of adsorption (Qst) for DES-appended UiO-66. Even so, the sample could be regenerated at 373 K and vacuum, and could be recycled without drop of CO2 uptake after 6 times.Graphical abstractExtra adsorption sites from DES synergized with the preserved metal sites from UiO-66 to enhance CO2 capture performance at low pressure.Unlabelled Image
       
  • Sarin chemisorbent based on cobalt-doped graphene
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Neeraj K. Jaiswal, Goran Kovačević Ion bombardment on graphene sheets can produce atomic vacancies that can trap metal atoms. In this paper, we demonstrated that these trapped metal atoms can effectively bind other molecules with heteroatoms, making them chemisorbed to the graphene. The trapped cobalt atom can bind sarin molecule through fluorine atom with dissociation energy significantly higher than the one bonded via oxygen atom. This suggests that it can displace water molecule and therefore pledge for sarin chemisorbent in atmospheric environment. Our investigations also revealed that metallic character is enhanced upon sarin adsorption unlike the bonding of water molecule with trapped metal atom in graphene lattice which causes an opening of small (0.02 eV) band gap. Present findings can have promising application towards detecting the presence of toxic sarin molecules.Graphical Unlabelled Image
       
  • AFM and DFT study of depression of hematite in oleate-starch-hematite
           flotation system
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Lixia Li, Chen Zhang, Zhitao Yuan, Xinyang Xu, Zhenguo Song The depression of hematite in the reverse flotation system of oleate-starch-hematite was investigated at the atomic level by atomic force microscopy (AFM) combined with density functional theory (DFT). AFM imaging and cross-sectional imaging show that the adsorption configurations of oleate and starch on hematite were in shuttle and flake patterns, respectively, resulting in a greater adsorption thickness and adsorption area for starch than for oleate on the hematite surface. After functioned by starch, hematite was almost fully covered by starch so that there was no sufficient space for the adsorption of oleate. Corn starch was also detected aggregating fine hematite particles just like a flocculant. In the DFT study of the system, convergence tests were conducted to get the optimized hematite crystal geometry. The calculated interaction energies and Mulliken populations verified the favorable adsorption of oleate and starch on the hematite surface. Results indicated that covalent bonds formed between oleate and hematite, as well as between starch and hematite. However, in the oleate-starch-hematite system, the calculations showed that the distance between oleate and hematite in the presence of starch was too long to allow the adsorption of oleate. As for the water effect on the depression of hematite, the water molecules acted as a bridge between starch and the hematite surface by hydrogen bonds and were accompanied by chemical bonds between hematite surfaces and starch, which led to the depression of hematite. Therefore, in reverse flotation, oleate is hindered from adsorbing on the starch-covered hematite surface. The work presented here has profound implications for future studies of the depression of hematite, and may help solve the problem of screening and design of depressant of hematite.
       
  • Fabrication of MoS2/WSe2 heterostructures as electrocatalyst for enhanced
           hydrogen evolution reaction
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Dhanasekaran Vikraman, Sajjad Hussain, Linh Truong, K. Karuppasamy, Hyun-Jung Kim, T. Maiyalagan, Seung-Hyun Chun, Jongwan Jung, Hyun-Seok Kim Two-dimensional material based heterostructures produce novel phenomena due to distinctive interactions between stacked layers. This paper details fabrication of van der Waals heterostructure consisting of layered MoS2 and WSe2 on FTO substrates by combining solution bath and radio-frequency sputtering. Raman scattering confirmed WSe2/MoS2 heterostructure formation, X-ray photoelectron spectroscopy surface profile detailed the heterostructure composition, and depth profile showed heterostructure interfacial structure with stacked WSe2 and MoS2 layers on the FTO substrate. Surface properties confirmed the WSe2/MoS2 heterostructure formed a multi-structured array of nanograins, and high resolution electron micrographs confirmed vertically formed layered fringes. Hydrogen evolution showed enhanced electrocatalytic behavior with 116 mV overpotential at 10 mA/cm2 and 76 mV/decade Tafel slope. Electrocatalytic property robustness was confirmed by over 20 h continuous hydrogen evolution reaction in an acidic solution. Enhanced electrocatalytic outcomes were due to increased interfacial hole-electron separation, dispersing active facets through the interface. The stacked layered structure provides a new avenue for two-dimensional heterostructures for energy harvesting devices.Graphical abstractUnlabelled Image
       
  • Effect of heat treatment and synergistic rare-earth modified NiCrAlY on
           bonding strength of nanostructured 8YSZ coatings
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Feifei Zhou, Zhenguo Zhang, Saiyue Liu, Lan Wang, Jin Jia, You Wang, Xue Gong, Junfeng Gou, Chunming Deng, Min Liu In this paper, the nanostructured 8YSZ coatings and two kinds of bond coatings including NiCrAlY and NiCrAlYCe coatings were deposited by atmospheric plasma spraying onto nickel-based superalloys. The microstructure of as-sprayed coatings and the effect of heat treatment on bonding strength of NiCrAlY/8YSZ and NiCrAlYCe/8YSZ coatings were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), together with energy dispersive spectrum (EDS) and X-ray diffraction (XRD) analysis. The results indicate that the coatings exhibit typical bi-modal microstructure and the grain size of 8YSZ coatings keeps nanostructure. As for 8YSZ coatings, the phase transformation occurs from t phase to t′ phase during plasma spraying and the heat treatment does not change the phase structure. The heat treatment and rare-earth modified NiCrAlY coatings play an important role in enhancing the bonding strength of as-sprayed coatings significantly compared with NiCrAlY/8YSZ coatings. The bonding strength of NiCrAlYCe/8YSZ coatings whose temperature of the heat treatment is 800 °C @ 6 h can reach 48.9 MPa, which is 1.5 times than that of as-sprayed NiCrAlYCe/8YSZ coatings.
       
  • Surface 3-D lubrication structure design of Al2O3/Ni-laminated ceramics to
           improve tribological properties under combined environments
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Hengzhong Fan, Yunfeng Su, Junjie Song, Hongqi Wan, Litian Hu, Yongsheng Zhang High-performance alumina matrix ceramics have potential applications in harsh environments such as corrosive and high-temperature conditions because of their excellent mechanical properties, corrosion-resistance, and oxidation stability. In this study, a 3-D lubrication structure was designed and prepared on the surface of Al2O3/Ni-laminated ceramics using laser surface texture technology and bonded PTFE coatings. The wear mechanisms of the materials were also studied, and the effects of the 3-D lubrication structure on the tribological properties of Al2O3/Ni-laminated ceramics under dry and aqueous conditions were investigated. Four types of micro-dimples with different diameters and bonded PTFE solid lubricating coatings were successfully prepared on the surface of Al2O3/Ni-laminated ceramics. Experimental results demonstrated that the bonded PTFE coating combined with micro-dimples on the surface of ceramics had excellent load-carrying capacities and wear-resistance under both dry and aqueous conditions. The wear life showed a marked increase under both dry and aqueous conditions because the solid lubricant that was embedded in the micro-dimples improved the bonding strength of the coating and provided secondary lubrication. The synergistic effects of the micro-texture and the bonded PTFE coating significantly improved the tribological properties of the materials.Graphical abstractUnlabelled Image
       
  • The study of structural, morphological and optical properties of (Al,
           Ga)-doped ZnO: DFT and experimental approaches
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Pornsawan Sikam, Pairot Moontragoon, Zoran Ikonic, Thanayut Kaewmaraya, Prasit Thongbai ZnO is a widely studied material for several applications, such as a photocatalyst, a working electrode for dye-sensitized solar cells, and for thermoelectric devices. This work studies the effects of an increase in the number of carriers by doping ZnO with Al and Ga. The 6.25 mol% Al-doped ZnO, 6.25 mol% Ga-doped ZnO, and 12.5 mol% (Al, Ga)-co-doped ZnO nanoparticles were prepared using the combustion method. The prepared samples were then characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV–visible spectroscopy techniques. Moreover, the density functional theory (DFT) was also employed for computational study of Al and Ga doped ZnO. Optimized crystal structures, density of states (DOS) and band structure of these systems were calculated using Vienna Ab initio Simulation Package code. From this study, Al and Ga are found to play an important role in both the morphology and optical properties of the ZnO: Al and Ga doping can change the band gap and the Fermi level position in the ZnO. The prepared samples were characterized for their thermoelectric properties, and these were also modelled, using BolzTraP code, for ZnO, Al-doped ZnO, Ga-doped ZnO and (Al, Ga)-co-doped ZnO. The Seebeck coefficient, electrical conductivity, relaxation time, electronic thermal conductivity and power factor were all analysed. The experimental and computational results all point in the same direction, indicating that the thermoelectric properties of ZnO change because the semiconductor ZnO transforms into metallic ZnO when doped with Al and Ga. This leads to ZnO showing different thermoelectric properties, particularly Ga-doped ZnO and (Al, Ga)-co doped ZnO: they provide a high electrical conductivity and power factor. Therefore, it is expected that these favorable properties might promote the ZnO to be a potential candidate for improved efficiency thermoelectric devices.Graphical abstractUnlabelled Image
       
  • Correlated emission of X-ray and sound from water film irradiated by
           femtosecond laser pulses
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Hsin-hui Huang, Saulius Juodkazis, Koji Hatanaka Simultaneous measurements of hard X-ray by a Geiger counter and audible sound (10 Hz–20 kHz) by a microphone from a thin water film in air were carried out under intense single and double pulse irradiations of femtosecond laser (35 fs, 800 nm, 1 kHz). Emission profiles of X-ray and sound under the single pulse irradiation by changing the water film position along the laser incident direction (Z-axis) show the same peak positions with a broader emission in sound (403 μm at FWHM) than in X-ray (37 μm). Under the double pulse irradiation condition with the time delay at 0 ps and 4.6 ns, it was clearly observed that the acoustic signal intensity is enhanced in associated with X-ray intensity enhancements. The enhancements can be assigned to laser ablation dynamics such as pre-plasma formation and transient surface roughness formation induced by the pre-pulse irradiation. For the acoustic signal under the double-pulse irradiation with the time delay, there was a weak dependence observed on the pre-pulse irradiation position at the laser focus. It is consistent with a long breakdown filament formation which makes the microphone-detection less position-sensitive.
       
  • A robust and versatile superhydrophobic coating: Wear-resistance study
           upon sandpaper abrasion
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Meng Li, Yu Li, Fang Xue, Xinli Jing The mechanical durability, especially wear-resistance seriously restricts the practical application of superhydrophobic surfaces. Lots of efforts have been put to improve the mechanical durability of superhydrophobic surfaces. However, due to the lack of a standard evaluation criterion, it is inaccurate to evaluate the mechanical durability of superhydrophobic surfaces by merely comparing the abrasion cycles or distance it can stand before losing superhydrophobicity. In this paper, the wear-resistance of superhydrophobic surfaces against sandpaper abrasion was evaluated based on a typical resin-hydrophobic filler formula. The mechanical strength, coefficient of friction and evolution of superhydrophobicity with growing abrasion cycles of as-prepared superhydrophobic surfaces were carefully studied by considering the hydrophobic filler sizes. In spite that superhydrophobic surfaces can all be achieved with hydrophobic fillers from nano-meter scale particles to micro-meter scale clusters at a certain content, the larger the filler size, the better the wear-resistance. For superhydrophobic coatings with a given surface roughness, its superhydrophobicity can be preserved when abraded against items which were rougher than coating itself. Furthermore, drag reduction performance of the developed superhydrophobic surfaces was evaluated against the polymer solution. This work will provide useful clues for establishing the standard to evaluate the wear-resistance of superhydrophobic coatings.Graphical abstractUnlabelled Image
       
  • Rational design of a sandwiched structure Ni(OH)2 nanohybrid sustained by
           amino-functionalized graphene quantum dots for outstanding capacitance
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Lingxia Zheng, Lingtong Guan, Jianlan Song, Huajun Zheng The rational structure design of nanohybrids plays a vital role in the supercapacitor performance of electrode materials. Herein, a novel sandwiched structure based on Ni(OH)2 and amino-functionalized graphene quantum dots (Ni(OH)2/af-GQDs) is prepared via a facile green strategy. The layered Ni(OH)2 nanosheets are spaced by amino groups from af-GQDs to afford a sandwiched configuration with an enlarged pore diameter of 1.8 nm, which leads to the decrease of random aggregation of Ni(OH)2 nanosheets and dramatically facilitates the ion transport, thus contributing to the increased surface area and improved electrochemical capacitance. Besides, the introduction of af-GQDs leads to enhanced electrical conductivity and better cycling stability as well as contributing additional electrochemical double-layer capacitance, resulting in an outstanding specific capacitance of 2653 F g−1 at 1 A g−1. An asymmetric supercapacitor (ASC) based on Ni(OH)2/af-GQDs and electrochemical-exfoliated graphene (EG) is assembled, exhibiting a wide potential window range, a high energy density, and an excellent cycling stability with 90.15% capacitance retention. These results definitely demonstrate the great potential of Ni(OH)2-based hybrid materials in the development of high-performance supercapacitors.
       
  • A novel magnetic heterogeneous catalyst oxygen-defective CoFe2O4−x for
           activating peroxymonosulfate
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Liying Wu, Yongbo Yu, Qian Zhang, Junming Hong, Ji Wang, Yuecheng She Through direct and indirect radical mechanism of peroxymonosulfate (PMS) activation, novel CoFe2O4−x catalysts were successfully developed via hydrogen calcination to overcome popular disadvantages of the dependence on pH. Bisphenol A (BPA) was selected as the model pollutant to decipher the mechanism of catalysts for peroxymonosulfate (PMS) activation. Possible degradation pathways of Bisphenol A were proposed via analysis of liquid chromatograph mass spectrometer (LC-MS). The findings indicated that catalytic activation of CoFe2O4−x was not dependent upon the initial pH, as the direct and indirect radicals seemed to be generated in parallel. FTIR analysis confirmed that surface hydroxyl groups were actively involved in the activation of PMS under alkaline conditions. During the reaction, the oxygen defects promoted electron transfer and participated in the redox cycle from Co3+/Fe3+ to Co2+/Fe2+ to generate 1O2 and O2−. Hydroxyl (OH) and sulfate (SO4−) radicals were generated on the surface of CoFe2O4−x by the synergistic interactions among oxygen defects, transition metal, and surface hydroxyl groups. To the best of our knowledge, this combined mechanism of direct and indirect radical generation for advanced oxidation was a first-attempt study to be disclosed in public domain.Graphical abstractNovel CoFe2O4−x with abundant oxygen defects that were successfully developed via hydrogen calcination were used for peroxymonosulfate (PMS) activation. The oxygen defects promoted electronic transfer and participated in the redox cycle from Co3+/Fe3+ to Co2+/Fe2+ to generate 1O2 and O2−. Hydroxyl (OH) and sulfate (SO4−) radicals were generated on the surface of CoFe2O4−x by the synergistic action of oxygen defects, transition metal, and surface hydroxyl groups for the degradation of BPA.Unlabelled Image
       
  • Functionalization of single-layer graphene for immunoassays
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Elisabete Fernandes, Patrícia D. Cabral, Rui Campos, George Machado, M. Fátima Cerqueira, Cláudia Sousa, Paulo P. Freitas, Jérôme Borme, Dmitri Y. Petrovykh, Pedro Alpuim The excellent electronic properties of single-layer graphene provide the fundamental basis for its use in advanced electronics applications. Graphene-based biosensors, however, are one of the exceptions among the applications that take advantage of the unique properties of this material, because high hydrophobicity of graphene hinders the controlled immobilization of biomolecular probes, particularly of antibodies for immunoassays. In contrast to methods that rely on aggressive chemical oxidation of graphene, we overcome this challenge by implementing an effective strategy that modifies single-layer graphene to render it hydrophilic and biocompatible without compromising the electronic structure. Graphene produced in-house by chemical vapor deposition (CVD) was modified with a heterobifunctional linker that attached to the surface via a pyrene group and presented a standard N-hydroxysuccinimide (NHS) ester ligand for covalent immobilization of biomolecules. The suitability of thus modified surface for biofunctionalization was then confirmed via real-time monitoring of the immobilization of an antibody by quartz crystal microbalance (QCM) measurements followed by the chemical characterization by x-ray photoelectron spectroscopy (XPS). Finally, as a proof-of-concept for biofunctionalization of graphene without compromising its electronic structure, a graphene immuno-field-effect transistor (immuno-FET) was fabricated, biofunctionalized, and tested for detection of Matrix Metalloproteinase 9 (MMP-9), a biomarker related to clinical diagnostics of ischemic stroke.Graphical abstractUnlabelled Image
       
  • Fabrication of Ag2O/TiO2 composites on nanographene platelets for the
           
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Rosari Saleh, Ardiansyah Taufik, Suhendro Purbo Prakoso Ternary Ag2O/TiO2/nanographene platelet (Ag2O/TiO2/NGP) composites containing various amounts of NGP were synthesized using a microwave-assisted method and were used as catalysts for degradation of organic dyes in aqueous solution. The composites were characterized by various methods, and their photocatalytic performance was systematically investigated with respect to degradation of methylene blue. Compared with pure TiO2 and Ag2O nanoparticles as well as Ag2O/TiO2 composites, the Ag2O/TiO2/NGP composites exhibited superior photocatalytic performance in the UV and visible light range. The results also indicated that Ag2O/TiO2/NGP composites could be used as efficient broad-spectrum catalysts for the removal of several dye contaminants in aqueous solutions. The correlation between photocatalytic mechanism and physical properties of the catalysts was discussed. The effects of the addition of hydrogen peroxide (H2O2) and persulfate on MB degradation were also investigated. Photocatalytic efficiency was noticeable in the presence of both oxidizers. Because inorganic anions are common substances in natural water, their influence was also evaluated. They were found to inhibit the catalytic activity of Ag2O/TiO2/NGP composites. Their effectiveness in inhibiting photocatalytic degradation of MB was CO32− > NO3− > HPO4− > Cl− > SO42−.Graphical abstractUnlabelled Image
       
  • Novel electrocatalyst of nickel sulfide boron coating for hydrogen
           evolution reaction in alkaline solution
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yihui Wu, Ying Gao, Hanwei He, Ping Zhang Seeking cost-effective and highly active non-precious hydrogen evolution reaction (HER) electrocatalysts is still strongly desired in water splitting. In this work, a low-cost and highly efficient HER electrocatalysts of amorphous Ni–S–B coating on nickel mesh is successfully synthesized by means of a simple current-density electrodeposition. The obtained Ni–S–B coating shows superior HER electrocatalytic activity as evidenced by low onset overpotential of 27 mV and 240 mV to drive 10 mA·cm−2 under alkaline conditions. Such high hydrogen evolution activity for Ni–S–B coating can be mainly attributed to the larger surface area (more exposed active sites), faster electron transport between electrode-catalyst-electrolyte interfaces, and nickel mesh substrate. Therefore, Ni–S–B coating can be applied as an efficient HER electrocatalyst to use in alkaline water electrolyzers.Graphical abstractUnlabelled Image
       
  • Thermally driven reversible photoluminescence modulation in WS2/VO2
           heterostructure
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Pawan Kumar, Davinder Singh, Viswanath Balakrishnan We demonstrate reversible modulation of photoluminescence in chemical vapor deposition (CVD) grown WS2 monolayer transferred on VO2 thin films that undergo insulator-metal transition. Thermally driven phase transition in VO2 thin film involving structural change as well as thermal expansion mismatch at interfaces induce strain and able to reversibly tune photoluminescence (PL) of atomic thin WS2 layer. PL intensity is increased with enhancement factor of 1.83 which corresponds to ~250% enhancement when heated from 30 °C to 70 °C. With further increase of temperature, PL intensity is found to be decreasing due to thermal quenching. While interference effect arising from metallic VO2/WS2 interface may also contribute for luminescence enhancement in metallic state, the observed increase in photoluminescence intensity during heating within the insulating state reveals the role of thermal strain. Systematic in-situ Raman and PL measurements revealed role of phase transition in controlling the PL intensity of excitons in WS2 monolayer. Single crystalline VO2 microplates also have been used to confirm the PL intensity modulation across phase transition. The observed direct correlation between photoluminescence and phase change interaction of VO2 with atomic thin layer of WS2 provide novel platform to tune the optical properties for diverse smart photonic applications.Graphical abstractUnlabelled Image
       
  • High performance flexible solid-state symmetric supercapacitors based on
           laser induced porous reduced graphene oxide-graphene oxide hybrid
           nanostructure devices
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): T. Kavinkumar, P. Kavitha, N. Naresh, S. Manivannan, M. Muneeswaran, B. Neppolian Materials with a porous structure and high surface area have gained tremendous research interests in the design of advanced high energy density supercapacitors because of their great capacitance and chemical stability. Herein, an effective method is introduced to achieve a large-scale production of porous graphene network by laser irradiation of graphene oxide films with a short span of time. Interestingly, this method introduces a porous structure, high surface area and promising electrochemical properties which significantly enhances the reversible capacitance behaviour. Notably, laser irradiated graphene oxide films electrodes show excellent areal capacitance of 149.7 mF cm−2 at 3 mV s−1 with a maximum energy density of 7.5 mWhcm−3. Also, these electrodes demonstrate an outstanding cycling stability, which retains above 85% capacitance of its initial capacitance after 5000 charge-discharge cycles shows a significant enhancement over other values reported in the literature. Furthermore, the bending tests confirms that the superior flexible performance of the laser irradiated graphene oxide electrodes holds a great potential for the development of wearable electronic devices.Graphical abstractUnlabelled Image
       
  • Self-generated N-doped anodized stainless steel mesh for an efficient and
           stable overall water splitting electrocatalyst
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Mengqi Yao, Baolong Sun, Ni Wang, Wencheng Hu, Sridhar Komarneni In this work, N-doped anodized stainless-steel mesh (NASSM) with mesoporous structure is demonstrated as a highly efficient, stable and bifunctional electrocatalyst with tuned electronic structure and surface morphology. NASSM was fabricated by anodic oxidation with Cr as non-catalytic substance by in situ removal of the SSM surface to regulate the morphology with mesoporous structure, followed by nitrogenization. NASSM showed an overpotential of 225 mV at 10 mA cm−2, which exceeded that of commercial IrO2/C catalyst, with a low Tafel slope of 49.7 mV dec−1 and excellent stability for over 100 h. NASSM exhibited an overpotential of 146 mV at 10 mA cm−2 and a Tafel slope of 60.1 mV dec−1. NASSM, as a bifunctional electrocatalyst, showed potentials of 1.61 and 1.76 V at 10 and 50 mA cm−2, respectively, for overall water-splitting with only a 0.01 V increase after a long-term stability test. These values are superior to those reported for directly modified SS-based bifunctional electrocatalysts. The remarkable catalytic properties of NASSM could be attributed to the tuning of not only electronic structure but also surface morphology. This work reports an efficient approach to synthesize and tune an effective and low-cost bifunctional catalyst based on SSM for large-scale application.Graphical abstractUnlabelled Image
       
  • Investigation of the anticorrosion properties of graphene oxide doped thin
           organic anticorrosion films for hot-dip galvanized steel
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Qi Liu, Ruina Ma, An Du, Xiaoran Zhang, Huazhen Yang, Yongzhe Fan, Xue Zhao, Xiaoming Cao Graphene oxide (GO) was doped into a silicylacrylate core-shell copolymer emulsion to prepare a thin organic anticorrosion film on galvanized steel. The effect of GO on the composition, morphology, and corrosion resistance of the protective film was investigated. X-ray photoelectron spectroscopy studies revealed that the film composition remained unchanged after the incorporation of GO. Further, scanning electronic microscopic observations revealed significant modification of the defects in the film after the addition of GO, resulting in decreased surface roughness. The increase in the water contact angle and decreases in both the surface free energy and adhesion work confirmed a decrease in the hydrophilicity of the anticorrosion film after incorporation of GO. Most importantly, the corrosion rate of the film and the corrosion current density decreased by one and two orders of magnitude, respectively. The results of electrochemical impedance spectroscopy also suggested significant increase in resistance to the ionic current through the pores and the charge transfer resistance. All these results proved the positive effect of GO on the enhancement of corrosion resistance.Graphical abstractThe introduction of graphene oxide into the organic anticorrosion film can significantly modify the morphology, leaving the decrease of surface roughness and the hydrophilicity. The corrosion resistance is also remarkably enhanced.Unlabelled Image
       
  • Chitosan modified Cu2O nanoparticles with high catalytic activity for
           p-nitrophenol reduction
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Yan Guo, Mingming Dai, Zhixu Zhu, Yuqi Chen, Hui He, Tianheng Qin Chitosan modified cuprous oxide (Cu2O-CTS) were prepared via facile chemical reduction method. The morphology and structure of Cu2O-CTS nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The catalytic ability of Cu2O-CTS, both in photocatalysis and electrocatalysis, was carried out on p-nitrophenol reduction. In comparison with the pristine Cu2O, Cu2O-CTS exhibits improved photocatalytic abilities with the reduction rate increased by 1.7 times. The catalytic capacity increases along with the increased proportion of CTS in Cu2O-CTS nanoparticles. Cu2O-CTS modified electrodes shows enhanced electrocatalytic capacities as well, with more positive reduction peak potential and higher peak current. Based on the experimental results, a catalytic mechanism for p-NP reduction over Cu2O-CTS catalysts is proposed. The improvement might come from the reduced band gap energy after the chitosan modification, thus Cu2O-CTS nanoparticles have higher catalytic activity. On the other hand, the more beneficial (111) crystal surface involves in the improvement as well, which endows Cu2O-CTS stronger activity and interaction with p-nitrophenol.
       
  • Fractal characteristics of TiO2-Ag nanocomposite films deposited by a
           grid-assisted co-sputtering method
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Mohammad Reza Zamani Meymian, Rouhollah Haji Abdolvahab, Ali Kosari Mehr TiO2-Ag composite films are deposited on glass substrates by a novel grid-assisted co-sputtering method, aiming at preparing films with different silver contents. The films are characterized by energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, atomic force microscopy (AFM), ultraviolet-visible spectroscopy, and photoluminescence spectroscopy. Furthermore, the parameters of saturation roughness, fractal spectra, and permutation entropy are utilized to analyze the AFM images; the permutation entropy is employed in a 2D matrix to measure the complexity. The atomic ratios of silver to titanium range from 0.09 to 7.80, and the observed optical band gaps are in the range of 3.17 to 3.26 eV. Photoluminescence spectroscopy reveals the photoinduced-electron-trapping effect of Ag particles in the structure and surface of the films governs the emission intensities. The AFM images show the roughness of the films increases by increasing the Ag content, and it can be seen that an increase in the TiO2 content of the films results in an increase in fluctuation per area, hence increasing the permutation entropy. Therefore, it is proposed that the Ag content of the films could be predicted by surface roughness and permutation entropy measurements; the fractality of the data allows a more precise determination of silver content.
       
  • Core@shell β-FeOOH@polypyrolle derived N, S-codoped Fe3O4@N-doped porous
           carbon nanococoons for high performance supercapacitors
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Maiyong Zhu, Qi Chen, Jingjing Tang, Wenjing Wei, Songjun Li The combination of carbon and iron oxide has recently attracted increasing research interest in energy conversion and storage. Here, the hybrid nanostructure with N, S-codoped Fe3O4 supported/embedded on/in N-doped porous carbon (NS-Fe3O4@N-PC) nanococoon was prepared via direct pyrolysis of core@shell β-FeOOH@Polypyrrole (β-FeOOH@PPy) composite. Benefiting from the synergistic effect of high redox activity of NS-Fe3O4 and excellent electrical conductivity as well as good mechanical stability of N-PC, the obtained NS-Fe3O4@N-PC exhibited an enhanced specific capacitance of 866 F/g at 1 A/g along with excellent rate capability (383 F/g at 10 A/g) and improved cycling stability (78.2% of initial capacitance retained after 5000 cycles test) while applied as electrode materials of supercapacitor. Significantly, the asymmetric supercapacitor devices assembled using NS-Fe3O4@N-PC as anodes and commercial carbon nanotubes as cathodes can achieve a large stack energy density of 38.9 Wh/Kg at a stack power density of 700.2 W/Kg along with good stability (only 8.4% decay of initial capacitance after 5000 cycles at 4 A/g). The present work may provide a general approach for fabricating other metal oxide@carbon hybrid nanomaterials for various applications.Graphical abstractUnlabelled Image
       
  • Direct p-doping of Li-TFSI for efficient hole injection: Role of polaronic
           level in molecular doping
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Kiwoong Kim, Junkyeong Jeong, Minju Kim, Donghee Kang, Sang Wan Cho, Hyunbok Lee, Yeonjin Yi Bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) has been popularly employed as an efficient p-dopant that increases the conductivity of a hole transport layer (HTL) in perovskite solar cells and dye-sensitized solar cells. However, the working mechanism of the Li-TFSI dopant is a long-standing question. The hygroscopicity of Li-TFSI makes it difficult to isolate the exact doping mechanism. In this study, we unveil the role of Li-TFSI in the p-doping to the N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) HTL. A series of systematic in situ measurements using ultraviolet and inverse photoelectron spectroscopy reveal that electron transfer from NPB to Li-TFSI occurs due to the lower-lying negative polaronic level of Li-TFSI rather than the positive polaronic level of NPB. The hole injection barrier between NPB and indium tin oxide is significantly reduced with Li-TFSI doping, enhancing the device performance of hole-only devices and organic light-emitting diodes dramatically. With excessive dopants, however, the agglomerative property of Li-TFSI became dominant, decreasing the doping efficiency. These results provide robust guidelines for developing an efficient doping method for a molecular system with high conductivity.Graphical abstractUnlabelled Image
       
  • Visible photoactivity and antiphotocorrosion performance of CdS
           photocatalysts by the hybridization of N-substituted carboxyl group
           polyaniline
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Jiali Zhang, Jiayu Fang, Xiaoai Ye, Zanru Guo, Yongxin Liu, Qi Song, Shan Zheng, Xi Chen, Shaohui Wang, Shaoming Yang In the paper, we report on the visible photocatalytic activity and antiphotocorrosion performance of CdS quantum dots (CdSQDs) by the combination of polyaniline with the modification of the carboxyl group, which was prepared by an N-substituted carboxyl group polyaniline (NPAN) cadmium precursor. The photocurrent response and photodegradation of Rhodamine B experiments show a higher current output and photocatalytic activity for the CdSQDs/NPAN hybrid photocatalysts in comparison with the mechanical blends of CdS nanoparticles and NPAN, as well as pure CdS nanoparticles. The enhanced photocatalytic performance could be attributed to the hybrid effect between CdSQDs and the carboxyl group in the polyaniline matrix. TEM morphology and XRD patterns of CdSQDs/NPAN hybrids had no significant differences before and after the photocatalytic oxidation, indicating that the incorporation of the carboxyl group in polyaniline could completely inhibit the photocorrosion of the CdS semiconductor. A possible photocatalytic mechanism of the CdSQDs/NPAN hybrid photocatalysts was proposed in accordance with the experimental results.Graphical abstractUnlabelled Image
       
  • Ordered mesoporous Co3O4/CMC nanoflakes for superior cyclic life and ultra
           high energy density supercapacitor
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): I. Manohara Babu, J. Johnson William, G. Muralidharan Development of micro/nanoarchitectures with unique morphology and size remains a great challenge in the pursuit of electrochemically active electrode materials for supercapacitors. Ordered mesoporous, flaky structures have been achieved by combined species (Co3O4/CMC) to meet the energy necessities in supercapacitors. Present study suggests an energy budget approach to address the preparation of cobalt oxide (electrical conductivity) with remarkable enhanced electrochemical performance by utilizing carbon (carboxymethyl cellulose-CMC) as physical support. This structure also offers short diffusion path for ions and accelerate effective charge transport which results in high specific capacitance (298 C g−1 at 1 A g−1), outstanding stability (90% capacity retention after 5000 cycles) and low charge transfer resistance (0.5 Ω) in three electrode system. In addition, we have designed an asymmetric supercapacitor (operating voltage 0–1.2 V) which shows desirable electrochemical behavior with an energy density of 18 W h kg−1 (at 2 A g−1). These outcomes endorse the potential capabilities of integrated Co3O4 & CMC which could be a promising electrode in future generation supercapacitors.Graphical abstractUnlabelled Image
       
  • Ultra-high photoresponse with superiorly sensitive
           metal-insulator-semiconductor (MIS) structured diodes for UV photodetector
           application
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): R. Marnadu, J. Chandrasekaran, S. Maruthamuthu, V. Balasubramani, P. Vivek, R. Suresh Here, we fabricated highly sensitive metal-insulator-semiconductor (MIS) type diodes with positive photo-response by introducing a polycrystalline Ce-WO3 composite thin films as an interfacial layer (IL) between the metal (Cu) and semiconductor (p-Si). Ce-WO3 films were successfully grown on a quartz substrate through JNSP technique with 0, 4, 8 and 12 wt% of Ce on an optimized substrate temperature of 400 °C. Polycrystalline Ce-WO3 films with mono-phase of monoclinic crystal structure were observed in XRD analysis, in which the mean crystallite size of the films were found to dwindle and their corresponding lattice parameters improved with Ce concentration. Randomly arranged rectangular shaped nanoplate-like surface morphology was observed through FESEM. From AFM study, the observed surface roughness of the films was found to be varying between 183 and 116 nm. Incorporation of Ce atoms in WO3 matrix facilitated better optical absorption and minimized Eg values which was studied using UV–vis spectrum. Current-voltage (I-V) characteristics exhibit highest σdc with low ρ and Ea values for higher concentration of Ce. For Cu/Ce-WO3/p-Si type diodes, as the light intensity of the diodes increased from 0 to 130 mW/cm2 their corresponding ideality factor (n) was found to decrease. Moreover, significant photodiode parameters like PS, R, QE (%) and D* enhanced with Ce and in particular the MIS diode fabricated with its 12 wt% showed better results in which a remarkable responsivity of 20.61 mA/W was recorded.Graphical abstractUnlabelled Image
       
  • TiO2/SnO2 and TiO2/CuO thin film nano-heterostructures as gas sensors
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Wojciech Maziarz The nano-heterostructures of TiO2/SnO2 and TiO2/CuO thin films have been investigated towards NO2 detection. Thin films have been deposited by reactive magnetron sputtering of metallic targets in Ar + O2 atmosphere. The properties of samples have been characterized by means of X-ray diffraction in grazing incidence GIXRD, X-ray reflectivity XRR, scanning electron microscopy SEM, optical methods and X-ray photoelectron spectroscopy XPS. It has been shown the SnO2 and CuO surface is well developed, with uniformly dispersed polycrystalline nanoparticles of TiO2. The addition of TiO2 thin layer increased the response of SnO2 nanostructure towards NO2. A very high resistance change ~4500 has been demonstrated for TiO2/SnO2 at 150 °C for 4 ppm of NO2, while for the SnO2 sensor the resistance change has been ~2300. The TiO2/SnO2 sensor responses to CO and H2 reducing gases were significantly lower. Such extremely good sensing properties of the n-n heterostructure to NO2 may be assigned to the formed interfaces and higher surface-to-volume ratio. However, TiO2/CuO n-p heterostructures reveal much smaller responses to NO2, what may be attributed to the effect of charge compensation.Graphical abstractUnlabelled Image
       
  • Pulsed laser deposition of thin carbon films on SiO2/Si
           substrates
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Teodor Milenov, Anna Dikovska, Georgi Avdeev, Ivalina Avramova, Kiril Kirilov, Daniela Karashanova, Penka Terziyska, Biliana Georgieva, Boris Arnaudov, Stefan Kolev, Evgenia Valcheva Pulsed laser deposition (PLD) of thin carbon films on SiO2/Si substrates was performed and the resulting films were examined by X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), Raman spectroscopy and ellipsometry. The deposition process was accomplished by laser ablation with Nd:YAG laser (third harmonic λ = 355 nm, pulse width τ = 18 ns and a repetition rate of 10 Hz) on 320–420 nm SiO2/(001) Si substrates with surface area of 15 × 15 mm2. The laser ablation process was carried out in two different deposition regimes: i) continuous regime with a deposition time of 15–1800 s; and (ii) pulse mode. As a target, carbon microcrystalline graphite disks (OD 15 mm, thickness 0.5 mm) were used. We established that films consisting of graphite nanoparticles/graphene grains of 5 to 30 nm thickness were deposited by the continuous PLD process while films comprising one to few-layered nano-sized graphene were deposited by pulsed PLD. Some films have low resistance (ρ = (0.1–1.5) × 10−3 Ω·m) and consist predominantly of sp2 hybridized carbon with Raman spectrum, which resembles that of nano-sized graphene. Regardless of the PLD process used, we observed an interface film enriched with sp3 hybridized carbon, which could be related to CO, CH and other interface bonds.Graphical abstractUnlabelled Image
       
  • Mesoporous nickel sulphide nanostructures for enhanced supercapacitor
           performance
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Nandhini Sonai Muthu, Muralidharan Gopalan The nanostructured electrode material with high surface area, good porous texture and appropriate pore-size distribution are facilitating more active sites for accumulation of ions and a large rate of ionic diffusion. Here, the mesoporous Ni3S4 nanostructures were prepared through a one-pot hydrothermal method. Annealing temperature which is known to affect the structural, morphological and electrochemical properties of the nanostructure has been optimized. Mesoporous Ni3S4 nanoflakes show a high surface area of 73 m2 g−1 at an annealing temperature of 200 °C (N2). This porous nanostructure exhibits a high specific capacitance of 1184 ± 71 to 548 ± 9 F g−1 at realistic specific currents of 5 to 40 A g−1. The symmetric two-electrode system (N2//N2) made up of mesoporous nanoflakes delivers a maximum energy density of 9 W h kg−1 at 2 A g−1 and maximum power density of 4.6 kW kg−1 at 40 A g−1. It retains 72% of initial capacitance after 5000 repeated cycling process. In addition, we have used two such symmetric devices to power a red LED. It demonstrates the intrinsic capability of porous Ni3S4 nanoflakes annealed at 200 °C to offer enhanced electrochemical performance and further appear to be a promising electrode material for real-life supercapacitors.Graphical abstractUnlabelled Image
       
  • Metal sulfide nanosheet–nitrogen-doped graphene hybrids as low-cost
           counter electrodes for dye-sensitized solar cells
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): R. Sankar Ganesh, K. Silambarasan, E. Durgadevi, M. Navaneethan, S. Ponnusamy, C.Y. Kong, C. Muthamizhchelvan, Y. Shimura, Y. Hayakawa Transparent thin two-dimensional nitrogen-doped graphene (NG) nanosheets coated with Ni- and Cu-doped MoS2 nanosheets (denoted as Ni-Mo-S@NG and Cu-Mo-S@NG, respectively) were synthesized by a simple hydrothermal process. The synthesized samples were coated by a simple spray pyrolysis technique onto fluorine-doped tin oxide substrates. Scanning transmission electron microscopy analysis showed that square-like Ni-Mo-S and hexagonal-like Cu-Mo-S nanosheets were anchored on the surface of NG without aggregation in Ni-Mo-S@NG and Cu-Mo-S@NG, respectively. Raman analysis confirmed the presence of graphene in both samples because of the high G-band intensity. Cyclic voltammetry analysis indicated that Ni-Mo-S@NG possessed superior catalytic activity to Cu-Mo-S@NG as an electrode in dye-sensitized solar cells; the separation between its oxidation and reduction peak currents (Epp) of about 382 mV was smaller than that of a platinum electrode (450 mV). A solar cell with Ni-Mo-S@NG showed a higher open circuit voltage (0.72 ± 0.02 V) and fill factor (0.57 ± 0.04) than those of solar cells with Cu-Mo-S@NG and Pt counter electrodes. The solar cell with Cu-Mo-S@NG showed higher current density and lower Epp (421 mV) than those of an equivalent cell with Pt. The solar cells with Ni-Mo-S@NG and Cu-Mo-S@NG showed power conversion efficiencies of 2.85% and 2.62%, respectively, which were equivalent to that of a cell with a Pt counter electrode (2.41%).Graphical abstractUnlabelled Image
       
  • Complex behavior of hydrogen sensor using nanoporous palladium film
           prepared by evaporation
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Hee-Jun Noh, Hyun-Jong Kim, Young Min Park, Jin-Seong Park, Ho-Nyun Lee Palladium is widely used as a hydrogen-sensing material owing to its high affinity for H2 adsorption at room temperature. In order to improve the gas-sensing performance, three-dimensional (3D) nanoporous Pd films with interconnected network structure were prepared by thermal evaporation at relatively high process pressures. The morphology, particle size, and crystallinity of the Pd films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Nanoporous Pd films with open pores and porosity greater than 96.4% were successfully fabricated. All Pd films were composed of metallic Pd and Pd oxide. The gas-sensing properties were evaluated by the change in resistance from 0.05 to 2% H2. When exposed to H2, the Pd films exhibited complex behavior, with a successive decrease and increase in resistance. This behavior was attributed to three effects – scattering, geometry, and reduction-oxidation. Nanoporous Pd films with a particle size of ~20 nm showed high sensitivity and fast reaction. The results demonstrated that 3D nanoporous Pd films with appropriate particle size were a promising candidate for a H2 sensor.Graphical abstractUnlabelled Image
       
  • Nano-porous shape memory membrane: Fabrication based on double
           bicontinuous structures in ternary blend and pore-size manipulation by
           macroscopic deformation
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Qiucheng Yang, Tao Wang, Liang Zhang, Jifei Zhang, Fei Wang, Yukun Ni, Silin Pan, Yongjin Li, Jichun You Nano-pore size is the key factor to determine the performance of porous membrane in various applications. The programmable and continuous manipulation of it remains as a great challenge. In this work, nano-porous shape memory polymer (SMP) membrane has been fabricated successfully in ternary blend of PVDF, PBSU and random copolymer (BMG) based on the special interface interaction and complicated phase behaviors among them. On one hand, phase separation takes place, producing bicontinuous structures with the characteristic size of microns including BMG rich phase and PVDF/PBSU mixed phase. The former provides shape memory effect in which cross-linked points and network play the roles of shape fixed phase and recovery phase respectively; on the other hand, exclusion of PBSU during crystallization of PVDF contributes to bicontinuous structures in nanoscale. The removal of PBSU based on double bicontinuous structures results in the interconnected nano-pores. The obtained nano-porous PVDF/BMG composite membranes possess not only shape memory performance, but also the interpenetrated channels. The pore size has been manipulated successfully by means of biaxial tension based on the proportional deformation in macro- and micro-scales. Our results provide a new strategy for the fabrication of nano-porous SMPs and the manipulation of pore size in them.
       
  • Coverage dependent CO adsorption manners on seven MoP surfaces with DFT
           based thermodynamics method
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): Xinxin Tian, Jie Min, Tao Wang CO interaction with MoP catalyst plays an important role in understanding the reaction mechanisms of syngas conversion into hydrocarbons and alcohols, which are promising feedstocks in industry. Herein, systematic ab initio computations were performed to identify the CO adsorption configurations and stable concentrations on different MoP surfaces at different conditions. Our investigations demonstrated that CO molecular adsorption is favored on MoP catalyst, and the saturation coverage ranges from 4/9 to 2 monolayers (ML) on different surfaces. With the atomistic thermodynamics method, the equilibrium phase diagrams were built to show the relationship of stable CO concentration with temperature and CO partial pressure on each surface. These results provide essential references for further converage dependent reaction mechanism studies.Graphical abstractUnlabelled Image
       
  • Effect of graphene oxide additive on tribocorrosion behavior of MAO
           coatings prepared on Ti6Al4V alloy
    • Abstract: Publication date: 30 June 2019Source: Applied Surface Science, Volume 480Author(s): You Zuo, Tianlu Li, Peihang Yu, Zicong Zhao, Xiaoyi Chen, You Zhang, Fei Chen Titanium and its alloys possess the superiority on corrosion resistance and the shortage on wear resistance. Tribocorrosion, a new study orientation concerning both corrosion and wear resistances and fascinating researchers in recent years, has to be considered on the titanium, its alloys and their surface treated materials. In this study, graphene oxide (GO) particles inserted coatings were prepared by micro-arc oxidation (MAO) treatment with various GO concentrations. The composition, morphology and topography were measured to analyze the structure and properties of coatings. Electrochemical impedance spectroscopy (EIS) and polarization measurements were utilized to assess the corrosion resistance of samples. Tribocorrosion behavior was evaluated by the open circuit potential (OCP) and coefficient of friction (COF) evolutions in advance to, during and after reciprocating sliding. The results showed that in GO concentration of 5 mL/L and 10 mL/L, the GO particles were inserted into the MAO coatings and the MAO coating by adding 10 mL/L GO particles possessed best tribocorrosion resistance.
       
 
 
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