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  Subjects -> CHEMISTRY (Total: 891 journals)
    - ANALYTICAL CHEMISTRY (55 journals)
    - CHEMISTRY (621 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
    - ORGANIC CHEMISTRY (51 journals)
    - PHYSICAL CHEMISTRY (70 journals)

CHEMISTRY (621 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: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 43)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 21)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 26)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 41)
ACS Nano     Full-text available via subscription   (Followers: 274)
ACS Photonics     Full-text available via subscription   (Followers: 14)
ACS Symposium Series     Full-text available via subscription  
ACS Synthetic Biology     Full-text available via subscription   (Followers: 24)
Acta Chemica Iasi     Open Access   (Followers: 5)
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
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: 6)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 6)
Advanced Functional Materials     Hybrid Journal   (Followers: 57)
Advanced Science Focus     Free   (Followers: 5)
Advances in Chemical Engineering and Science     Open Access   (Followers: 66)
Advances in Chemical Science     Open Access   (Followers: 18)
Advances in Chemistry     Open Access   (Followers: 21)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Environmental Chemistry     Open Access   (Followers: 5)
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: 11)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 25)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 16)
Advances in Polymer Science     Hybrid Journal   (Followers: 43)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
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: 3)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
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: 64)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 17)
American Journal of Chemistry     Open Access   (Followers: 30)
American Journal of Plant Physiology     Open Access   (Followers: 11)
American Mineralogist     Hybrid Journal   (Followers: 15)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 165)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 244)
Annales UMCS, Chemia     Open Access  
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 5)
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: 13)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 9)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 31)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 2)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 350)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 10)
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     Full-text available via subscription   (Followers: 21)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 128)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 84)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
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: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 71)
Catalysis for Sustainable Energy     Open Access   (Followers: 8)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 10)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 18)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 73)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 22)
Chemical Reviews     Full-text available via subscription   (Followers: 191)
Chemical Science     Open Access   (Followers: 24)
Chemical Technology     Open Access   (Followers: 24)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 32)
Chemistry & Industry     Hybrid Journal   (Followers: 7)
Chemistry - A European Journal     Hybrid Journal   (Followers: 163)
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     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 254)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 19)
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: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 11)
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: 24)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 6)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access   (Followers: 1)
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: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 22)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Communications Chemistry     Open Access  
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: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
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  
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: 8)
Current Science     Open Access   (Followers: 69)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  

        1 2 3 4 | Last

Journal Cover
Carbon
Journal Prestige (SJR): 2.226
Citation Impact (citeScore): 7
Number of Followers: 71  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0008-6223
Published by Elsevier Homepage  [3163 journals]
  • Graphite cathode and anode becoming graphene structures after cycling
           based on graphite-based dual ion battery using PP14NTF2
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Zhanyu Li, Jian Liu, Jianling Li, Feiyu Kang, Fei Gao
      Herein, a novel graphite-graphite dual ion battery (GGDIB) based on N-butyl-N-methyl-piperidinium bis(trifluoromethyl sulfonyl)imide (PP14NTF2) ionic liquid room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), that is, the NTF2 - anions and PP14 + cations in the electrolyte are intercalated into the graphite electrode during the charging process, while the NTF2 - anions and PP14 + cations are released into the electrolyte from the graphite electrode during discharging process. Interestingly, it is found through transmission electron microscopy (TEM) analysis that the graphite cathode and anode electrode materials of this GGDIB can become a few layers of graphene structure after cycling. The electrochemical performance, especially the discharge capacity, is influenced by the phenomenon of self-discharge. This GGDIB also exhibits excellent electrochemical performance, that is, the discharge capacity is 78.1 mA h g−1 at a current density of 20 mA g−1 over a voltage window of 0.1–5.0 V. In addition, the pseudopotential behavior in the GGDIB is also studied by cyclic voltammetry (CV).
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • An order reduction method for single-walled carbon nanotubes with
           multi-vacancy defects
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Robert B. Hudson, Alok Sinha
      Presented here is a novel method of reducing the computational cost of analyzing the vibrational properties of a single-walled carbon nanotube (CNT) containing multi-vacancy defects (MVDs), while maintaining a high degree of accuracy. This reduced-order model method is described as modal domain reduction (MDR). In the MDR method, a linearized model of a perturbed CNT is first transformed into modal coordinates derived from the pristine system, taking into account the differences in the numbers of degrees of freedom for the pristine CNT and the CNT with MVDs. Next, the system is divided into primary modes, on the basis of the frequency range of interest, and remaining or secondary modes. The impact of secondary modes on primary modes is captured by the dynamic condensation method. The accuracy of MDR is demonstrated on linearized models of nanotubes of differing diameter and chirality and with different sized MVDs. The natural frequencies and normal modes of these reduced-order models are calculated and compared to the results for the full-order systems.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Two orders of magnitude suppression of graphene's thermal conductivity by
           heavy dopant (Si)
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Woorim Lee, Kenneth David Kihm, Hong Goo Kim, Woomin Lee, Sosan Cheon, Sinchul Yeom, Gyumin Lim, Kyung Rok Pyun, Seung Hwan Ko, Seungha Shin
      The in-plane thermal conductivity ( k S i G ) of silicon-doped graphene (SiG) was greatly suppressed primarily due to increased phonon scattering associated with the large mass difference of Si from its host C atoms. For SiG as supported on an 8 nm-thick SiO2 substrate, the measured k S i G represents progressive decrease and saturation with the increase of Si dopants concentration, showing more than an order-of-magnitude reduction from that of supported pristine graphene (PG) and nearly two order-of-magnitude reductions when compared with suspended PG at about 2% doping concentration. The enhanced graphene-substrate conformity through thermal annealing in a vacuum additionally lowers k S i G from that of ambient annealing. The substitutional Si dopants tend to suppress the contribution of temperature-sensitive phonons with long mean free paths and weaken the temperature dependence of k S i G . The presence of Si dopants seems to allow for faster attainment of thermal equilibrium between different heat carriers due to the reduced phonon mean free paths. We believe that SiG holds the possibility of exclusively controlling the thermal properties of graphene, since the substitutional dopants do not violently destruct the hexagonal lattice structure of graphene and may possibly have minimal effects on graphene's electrical properties.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Micromachined nanocrystalline graphite membranes for gas separation
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): S.J. Fishlock, S.H. Pu, G. Bhattacharya, Yisong Han, J. McLaughlin, J.W. McBride, H.M.H. Chong, S.J. O'Shea
      Carbon nanoporous membranes show promising performance for the passive separation and sieving of different gases, for example for helium and hydrogen separation. In this paper, nanocrystalline graphite (or nanographite) has been evaluated as a membrane material for molecular sieving of helium and hydrogen from larger gas constituents. Nanographite of 350 nm thickness was prepared using plasma-enhanced chemical vapour deposition onto fused silica substrates, from which membranes were microfabricated using deep wet etching. Permeability of hydrogen and helium were 1.79 × 10−16 and 1.40 × 10−16 mol m m−2s−1 Pa−1 at 150 °C respectively, and measured separation was 48 for He/Ne, >135 for H2/CO2 and >1000 for H2/O2. The gas separation properties of the nanographite membranes were tested in the temperature range of 25–150 °C, and the permeation measurements show nanographite to be highly selective of helium and hydrogen over all larger gas molecules, including neon.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Strength loss of carbon nanotube fibers explained in a three-level
           hierarchical model
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Enlai Gao, Weibang Lu, Zhiping Xu
      Although the tensile strength of carbon nanotubes inherited from the sp 2 hexagonal carbon lattice is as high as 120 GPa, the state-of-the-art mechanical resistance of carbon nanotube fibers is below 10 GPa. Material imperfections embedded in the complex microstructures are responsible for this remarkable reduction across multiple length scales. In this study, we rationalize this multi-scale degradation of mechanical performance through theoretical analysis of the processing-microstructure-performance relationship for carbon nanotube fibers based on the experiment data, offering a simplified model that not only quantifies the breakdown of material strength at the nanotube, bundle, and fiber levels, respectively, but also provides practical advices to optimize the manufacturing processes for elevated mechanical performance.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Random occurrence of macroscale superlubricity of graphite enabled by
           tribo-transfer of multilayer graphene nanoflakes
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Jinjin Li, Xiangyu Ge, Jianbin Luo
      Superlubricity of layered materials, such as graphite, boron nitride, and molybdenum disulfide, is easy to achieve at the nano- or microscale by the formation of ideal incommensurate contact, but it has never been observed at the macroscale due to the size limitations of the contact zone. In the present study, the instantaneous superlubricity of graphite against steel was achieved at the macroscale, through the formation of many tribo-transferred multilayer graphene nanoflakes (MGNFs) on the steel contact zone after the initial sliding. The friction coefficient could reduce to a minimum of 0.001, which randomly appeared as the test progressed, with a maximal sliding distance of 131 μm. The macroscale superlubricity was derived from the statistical frictional forces of multiple transferred MGNFs (in the contact zone) sliding on the graphite with atomic steps. This finding provides a possible approach to achieving the macroscale superlubricity of layered materials by the discretization of a large contact area into multiple, dispersed nanoflake contacts.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Multi-walled carbon nanotubes photochemistry: A mechanistic view of the
           effect of impurities and oxygen-containing surface groups
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Damián Rodríguez Sartori, María Laura Dell’Arciprete, Giuliana Magnacca, Paola Calza, Enzo Laurenti, Mónica C. Gonzalez
      Continuous photolysis experiments and transient absorption spectroscopy were performed in combination with other techniques including HRTEM, XPS, Raman, TGA, and ESR spectroscopy, to investigate the role of residual metals and amorphous carbon on the photochemical process taking place after 350–355 nm light irradiation of as obtained commercial multi-walled carbon nanotubes, denoted as pCNT. The results indicate that 350–355 nm photolysis of pCNT leads to the oxidation of surface oxygen-containing groups and defects which in turn are eliminated leading to more graphitic –like multi-walled carbon nanotubes (MWCNT). Residual metal catalysts and oxygen containing amorphous carbon and oxidized C-functionalities of MWCNT play an important role in the generation of MWCNT photoinduced charge-separated states. The process of 350 nm excitation of pCNT leads to exciton formation followed by hole transfer to metal oxides and further oxidation of C-O functionalities. A plausible mechanism explaining the elimination of oxidized groups attached to pCNT graphene walls and amorphous carbon and leading to more graphite-like CNTs is discussed. The results presented may have implications in the nanoscale semiconductor materials for optoelectronics applications.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Amine group induced high activity of highly torn amine functionalized
           nitrogen doped graphene as the metal-free catalyst for hydrogen evolution
           reaction
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Binglu Deng, Da Wang, Zhongqing Jiang, Jiye Zhang, Siqi Shi, Zhong-Jie Jiang, Meilin Liu
      A metal-free highly torn amine functionalized nitrogen doped graphene (HT-AFNG) used as hydrogen evolution reaction (HER) catalyst is prepared by using a simple synthesis method involving the hydrothermal reaction of graphene oxide in the presence of ammonia and the subsequent ball milling. The metal-free HT-AFNG is efficient for the HER in the acid solution and can deliver an onset potential of 100 mV and an overpotential of 350 mV at the current density of 10 mA cm−2, which is much lower than those of the singly and dually doped graphene reported previously. The amine functionalized and nitrogen doped structure plays an important role in the high catalytic activity of the HT-AFNG, where the amine group can greatly reduce the ΔGH* value at both defect and edge sites as well as increases the electron transfer capability of nitrogen dope graphene (NG). Significantly, the highly torn structure also makes a big contribution on the high catalytic activity of the HT-AFNG, since it allows for the good accessibility of the active sites for the HER. The strategy involves the introduction of electron donating groups open a new research pathway towards the improvement of HER catalytic activity of graphene-based materials.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • 13C/19F high-resolution solid-state NMR studies on layered carbon-fluorine
           compounds
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Miwa Murakami, Kazuhiko Matsumoto, Rika Hagiwara, Yoshiaki Matsuo
      13C/19F high-resolution solid-state NMR was applied to examine local structures of a stage-1 layered carbon-fluorine compound (C2.8F). Four 19F (F1∼F4) and two 13C signals (C1 and C2) unraveled by high magnetic field (14 T) and fast magic-angle spinning (>35 kHz) were examined by various two-dimensional correlation experiments. In addition to “through space” 13C-19F and 19F-19F dipolar correlation, which reveals distance proximity among 13C/19F spins, we examined feasibility of applying the J interaction for examination of “through bond” correlation. These experiments led assignment of two of the four F signals (F2 and F3) to F directly covalent bonded to sp3 carbon and an interleaving domain for the local structure of the minor C2-F3 group among the major domain composed of C2-F2 and sp2 carbon (C1). The other two 19F signals (F1 and F4) were assigned to as CF2 and F ions, respectively. A spectroscopic evidence for the C-F bond being the σ bond is given by the observation of a non-zero one-bond J value (193 ± 4 Hz) for C2-F. Further, the similar J CF = 197 Hz for C-F in poly(carbon fluoride) confirmed that the so-called “semi-ionic/semi-covalent” C-F bond in C2.8F is actually a “standard” covalent C-F bond.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Low excitation of Raman D band in [2+1] cycloaddition functionalized
           single-walled carbon nanotubes
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Kang Zhang, Jingyuan Wang, Jianping Zou, Weifan Cai, Qing Zhang
      The D band to G band intensity ratio in the Raman spectroscopy has been widely used to identify the degree of covalent functionalizations of single-walled carbon nanotubes (SWCNTs). The Raman D band at ∼1350 cm−1 is extremely sensitive to the sidewall sp3 scattering centers created by covalent functionalizations. However, we report here that [2 + 1] cycloaddition functionalization does not efficiently excite the Raman D band even up to ∼ 3% of the functionalization as manifested by X-ray photoelectron spectroscopy (XPS). In-depth Raman spectra and XPS spectra analysis suggest that such low excitation of the Raman D band originates from the weakened electron scattering in [2 + 1] cycloaddition functionalized SWCNTs due to their unique sidewall bonding configurations. Our results reveal the origin of the low excitation of the Raman D band in [2 + 1] cycloaddition functionalized SWCNTs, and provide a precise and in-depth understanding of [2 + 1] cycloaddition functionalized SWCNTs.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • A long-term anticorrsive coating through graphene passivation
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Ji-Heng Ding, Hong-Ran Zhao, Yan Zheng, Xinpeng Zhao, Hai-Bin Yu
      Despite graphene (G) is impermeable to all molecules and with excellent chemical stability, conductive G is cathodic to most metals and can aggravate metal corrosion at exposed metal-coatings interfaces. This effect may accelerate dangerous localized corrosion and potentially impedes its applications in metal protection. Here, we present successful synthesis of nonconductive G (FmG) through the Diels-Alder reaction between exfoliated G and a bio-based epoxy monomer, and its application in epoxy (EP) anticorrosive coatings. The FmG as-prepared exhibit well solubility in traditional organic solvents due to the graft of FdE chains on the FmG surface. The corrosion resistances of FmG reinforced EP coatings were investigated by electrochemical tests (open circuit potential, Tafel curves, and impedance) after immersed in a 3.5 wt % NaCl solution. The results demonstrated that embedding 0.5 wt% of FmG in EP coating effectively improves the barrier properties of the coating and shows superior corrosion resistance compared with pure EP. In addition, we also gave the protection mechanisms about the corrosion reaction of G-based modified and unmodified EP coatings. The strategy provides a promise strategy for development of G-based heavy coatings with superior barrier properties for metal protection.
      Graphical abstract image

      PubDate: 2018-06-18T18:50:32Z
       
  • Probing of polymer to carbon nanotube surface interactions within highly
           aligned electrospun nanofibers for advanced composites
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Simon G. King, Nicholas J. Terrill, Andrew J. Goodwin, Robert Stevens, Vlad Stolojan, S.Ravi P. Silva
      By electrospinning poly(ethylene oxide) (PEO)-blended sodium dodecyl sulfate (SDS) functionalized carbon nanotube (CNT) solutions, we engineered single- and double-walled nanotubes into highly aligned arrays. CNT alignment was measured using electron microscopy and polarised Raman spectroscopy. Mechanical tensile testing demonstrates that a CNT loading of 3.9 wt% increases the ultimate tensile strength and ductility of our composites by over a factor of 3, and the Young's modulus by over a factor of 4, to ∼260 MPa. Transmission electron microscopy (TEM) reveals how the aligned nanotubes provide a solid structure, preventing polymer chains from slipping, as well as polymer crystallisation structures such as ‘shish-kebabs’ forming, which are responsible for the improved mechanical properties of the composite. Differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) reveals micellar and hexagonal columnar structures along the axis of the fibers, some of which are associated with the presence of the CNT, where these hexagonal structures are associated with the SDS functionalization on the CNT surfaces. This work demonstrates the benefits of CNT alignment within composites, revealing the effectiveness of the electrospinning technique, which enables significantly improved functionality, increasing the utility of the composites for use in many different technological areas.
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      PubDate: 2018-06-18T18:50:32Z
       
  • A graphene-based sensor for real time monitoring of sun exposure
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Parisa S. Khiabani, Mehran B. Kashi, Xiao Zhang, Raheleh Pardehkhorram, Bijan P. Markhali, Alexander H. Soeriyadi, Adam P. Micolich, J. Justin Gooding
      The photoreduction of graphene oxide (GO) with titanium dioxide (TiO2) was exploited to fabricate a UV sensor for real time monitoring of sun exposure. The sensor was fabricated by simultaneous deposition of GO sheets and TiO2 nanoparticles onto interdigitated electrodes using an AC electrophoresis deposition method. Changes in the resistance of the GO sheets decorated with TiO2 nanoparticles during repeated cycles of exposure to UV were measured to understand the sensitivity of this sensor to UV radiation. Current-time traces revealed that the fabricated UV sensor retains a memory of each cycle of UV exposure; regardless of whether the sensor is exposed to UV for one long cycle or several short cycles. This memory of the extent of UV exposure is a biomimetic approach, analogous to the response of the skin to sun, and means the sensor requires no power except when the data is read from the sensor.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Fabrication of high-quality or highly porous graphene sheets from
           exfoliated graphene oxide via reactions in alkaline solutions
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Joon Young Cho, Jeong In Jang, Won Ki Lee, Soo Yeon Jeong, Jun Yeon Hwang, Heon Sang Lee, Jong Hwan Park, Seung Yol Jeong, Hee Jin Jeong, Geon-Woong Lee, Joong Tark Han
      The applications of solution-exfoliated graphene oxide (GO) as an electrical/electrochemical conductor require rational design–based approaches. Herein, we show that reduced GO nanosheets with highly ordered or nanoporous structures can be fabricated by treatment of graphite oxide (GrO) having variable-oxidation-degree with hot KOH solution. As model systems, GrO powders fabricated by modified Brodie and Hummers methods (B-GrO and H-GrO, respectively) were exfoliated into GO in alkaline solutions (to afford B-KGO and H-KGO, respectively), followed by 2.5-h refluxing at 100 °C. Notably, B-KGO was exceptionally resistant to hot KOH solution, whereas H-KGO was partially reduced under these conditions, as confirmed by 13C solid-state NMR, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy analyses. Moreover, reduced B-KGO featured highly ordered structures, whereas reduced H-KGO contained nanopores resulting from low-temperature activation in KOH solution. These extraordinary reactions of KGO nanosheets were translated into different electrical properties of reduced KGO nanosheets and different rheological properties of the corresponding pastes.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Non-Eulerian behavior of graphitic materials under compression
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Ch. Androulidakis, E.N. Koukaras, M. Hadjinicolaou, C. Galiotis
      The mechanical behavior of graphitic materials is greatly affected by the weak interlayer bonding with van der Waals forces for a range of thickness from nano to macroscale. Herein, we present a comprehensive study of the effect of layer thickness on the compression behavior of graphitic materials such as graphene which are fully embedded in polymer matrices. Raman Spectroscopy was employed to identify experimentally the critical strain to failure of the graphitic specimens. The most striking finding is that, contrary to what would be expected from Eulerian mechanics, the critical compressive strain to failure decreases with increase of flake thickness. This is due to the layered structure of the material and in particular the weak cohesive forces that hold the layers together. The plate phenomenology breaks down for the case of multi-layer graphene, which can be approached as discrete single layers weakly bonded to each other. This behavior is modelled here by considering the interlayer bonding (van der Waals forces) as springs in series, and very good agreement was found between theory and experiment. Finally, it will be shown that in the post failure regime multi-layer graphenes exhibit negative stiffness and thus behave as mechanical metamaterials.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Ultra-short-pulse laser ablation and modification of fully sprayed single
           walled carbon nanotube networks
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Maximilian Spellauge, Florin-Cristian Loghin, Jürgen Sotrop, Matthias Domke, Marco Bobinger, Alaa Abdellah, Markus Becherer, Paolo Lugli, Heinz P. Huber
      In this study, we report on femtosecond ( 470 fs ) laser pulse ablation and modification of solution processed single-walled carbon nanotube (SWCNT) networks sprayed on oxidized silicon and polyimide substrates. Taking advantage of the small heat affected zone of the femtosecond pulse regime we demonstrate precise and selective laser processes, that advance laser patterning beyond simple galvanic isolation. A thorough investigation regarding the laser pulse-SWCNT film interaction is performed, identifying critical interaction regimes in the single- and multi-pulse operation mode. For the first time we achieve a pronounced debundling of the network, by operating the laser below the ablation threshold, a process that was previously limited to pre-deposition. Furthermore, we investigate the effect of polarized laser pulses on the ablation properties. Making use of linear polarized laser pulses we are able to selectively ablate SWCNTs, which are oriented parallel to the incident laser polarization, resulting in aligned networks with anisotropic conductivity. This feature was previously tied to direct growth of SWCNTs, strongly limiting its implementation. The scaleability of the presented femtosecond laser processes is demonstrated, allowing for the use of low-cost solution processed SWCNT thin-films, while maintaining the advantages of on-chip SWCNT growth such as SWCNT separation and alignment.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Anomalous thermal stability in supergiant onion-like carbon fullerene
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Heng Zhao, Qiao Shi, Zhengde Han, Hao Gong, Zhisen Zhang, Shunqing Wu, Jianyang Wu
      Onion-like carbon fullerenes (OLCFs) are a promising material for applications in nanoscale devices, medicine, lubrication and superhard materials. Knowledge of the pyrolysis chemistry of OLCFs helps understanding the thermal-induced erosion of carbon-based resources and spacecraft materials. Here, using first-principle-based ReaxFF atomistic simulations, thermal and dynamical characteristics of supergiant 20-shell OLCF having concentric arrangement of C60@C240@ … @C24000 are explored. Fullerenes@20-shell OLCF yield larger average radii than isolated single-walled fullerenes (SWFs) at the same scale. The intershell-spacing@OLCF exhibits a reduction tendency from inner to outer shells, but is higher than that of bulk graphite. Because of nonbonded intershell forces, fullerenes@20-shell OLCF are energetically favorable over the corresponding isolated SWFs. In contrast to nonmonotonic variation of melting point with size and shell-index in SWFs and other nanoparticles, an anomalous shell-dependent melting instability in the 20-shell OLCF is identified due to the combined effects of geometrical size, nanoconfinement and surface; Both inner and outer fullerenes are not so resistive against heating, nor are they as strong as the identical-size isolated SWFs, however, the intermediate shells, locally similar to curved graphite, demonstrate higher heat-resisting property than identical-size isolated SWFs. Topological analysis reveals morphological transformation of four stages involving Stone-Wales rearrangement, heterogeneous defects nucleation, amorphization and fragmentation.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Reversible sulfuric acid doping of graphene probed by in-situ
           multi-wavelength Raman spectroscopy
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Gwanghyun Ahn, Sunmin Ryu
      Since lattice strain and charge density affect various material properties of graphene, a reliable and efficient method is required for quantification of the two variables. While Raman spectroscopy is sensitive and non-destructive, its validity towards precise quantification of chemical charge doping has not been tested. In this work, we quantified in-situ the fractional frequency change of 2D and G peaks in response of charge density induced by sulfuric acid solution as well as native lattice strain. Based on the experimental data and theoretical corroboration, we presented an optical method that simultaneously determines strain and chemically-induced charge density for three popular excitation wavelengths of 457, 514 and 633 nm. In order to expedite intercalation of dopant species through the graphene-SiO2 substrates, dense arrays of nanopores were precisely generated in graphene by thermal oxidation. The nano-perforated graphene membrane system was robust for multiple cycles of doping and undoping processes, and will be useful in studying various types of chemical interactions with graphene.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Core-shell structured carbon nanofibers yarn@polypyrrole@graphene for high
           performance all-solid-state fiber supercapacitors
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Long Chen, Deping Li, Lina Chen, Pengchao Si, Jinkui Feng, Lin Zhang, Yanhui Li, Jun Lou, Lijie Ci
      Carbon nanofibers yarns (CNY) have been prepared by carbonizing twisted electrospun PAN nanofibers, which can be used as the electrode of fiber-shaped all-solid-state supercapacitor after depositing conductive polymer of polypyrrole (PPy) and reduced graphene oxide (rGO) on their surface to form a core-shell structure (CNY@PPy@rGO). The flexible and binder-free fiber supercapacitors with PVA/H3PO4 gel electrolyte have a high specific capacitance (92.57 F/g, 80.46 F/cm3, 836.87 mF/cm2, and 111.46 mF/cm of C M, C V, C A, and C L, respectively, at the scan rate of 2 mV/s) thanks to the core-shell structure and synergistic effects of three conponents. It also shows high cycling performance with 86% capacitance retention after 10000 cycles with excellent flexibility and stability at different bending angles.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Tuning electronic properties by oxidation-reduction reactions at
           graphene-ruthenium interface
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Viktor Kandyba, Abdullah Al-Mahboob, Alessio Giampietri, Jerzy T. Sadowski, Alexei Barinov
      Mass production of graphene is associated with the growth on catalysts used also in other chemical reactions. We exploit the oxidation-reduction to tailor the properties of single layer graphene domains with incorporated bi-layer patches on ruthenium. Using photoelectron spectromicroscopy techniques, we find that oxygen, intercalating under single layer and making it p-doped by the formation of Ru-Ox, does not intercalate under the bilayer patches with n-doped upper layer, but decorates them under single layer surrounding creating lateral p-n junctions with chemical potential difference of 1.2 eV. O-reduction by thermal treatment in vacuum results in C-vacancy defects enhancing electronic coupling of remained graphene to Ru, whereas in H2, vacancy formation is suppressed. For the domains below 15–25 μm size, after O-reduction in H2, graphene/Ru coupling is restored, while wrinkle pattern produced by O-intercalation is irreversible and can trap reaction products between the wrinkles and Ru surface step edges. In fact, in certain regions of bigger domains, the products, containing H2O and/or its fragments, remain at the interface, making graphene decoupled and undoped.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Graphene milling dynamics during helium ion beam irradiation
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Songkil Kim, Ondrej Dyck, Anton V. Ievlev, Ivan V. Vlassiouk, Sergei V. Kalinin, Alex Belianinov, Stephen Jesse, Olga S. Ovchinnikova
      We explore the potential of the Helium Ion Microscope (HIM) as a tool for direct-write patterning of graphene and describe the underlying processes of graphene milling with image data processing. Controlled helium ion irradiation of suspended graphene conducted while monitoring the mill in-situ revealed the localized formation of nanopores, their growth, and coalescence. We also explore the effects of defects on the milling dynamics, and show that pre-exposed membranes rupture by cracking and rapid crack propagation at the edges of the growing defects. The mechanism for the rupturing process is described by local defect formation by excessive irradiation of helium ions, dictated by the scanning direction of the beam. These findings enrich fundamental understanding of the graphene milling process with a helium ion beam that, is necessary for high-resolution and high throughput patterning of graphene with nanoscale precision.
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      PubDate: 2018-06-18T18:50:32Z
       
  • Graphene oxide in generation of nanobubbles using controllable
           microvortices of jet flows
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Marziyeh Jannesari, Omid Akhavan, Hamid R. Madaah Hosseini
      Spontaneous generation of nanobubbles (NBs) was developed by using a controllable platform of superfast microvortices, based on turbulent jet flows in the presence of graphene oxide (GO) sheets. Very high energy dissipation rates through discharging warm water into cold N2 aqueous solutions resulted in creation of micro/submicro-vortices. Shear stresses in these domains generated gas local supersaturations, leading to the formation of high concentration (∼109 mL−1) of stable NBs. Introducing GO sheets into the microvortex system resulted in effective manipulation of NBs by providing energetically favorable sites for prompt heterogeneous nucleation as well as stronger shear rate fluctuations. Furthermore, hydrophilic nature of GO sheets induced releasing surface NBs into the bulk. Decreasing the average dimensions of GO sheets from ∼800 to 150 nm significantly reduced the size of NBs from ∼180 to 40 nm while caused a drastic increase (∼two orders of magnitude) in their concentrations. It was found that in the microvortex platform, NBs are able to screen GO surfaces. These results not only show the role of GO in effective and controllable production of NBs, but also suggest the possibility of surface modification of GO sheets by NBs for various upcoming bioapplications as drug carriers.
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      PubDate: 2018-06-12T06:10:17Z
       
  • Easy fabrication of flexible and multilayer nanocarbon-based cathodes with
           a high areal sulfur loading by electrostatic spraying for lithium-sulfur
           batteries
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Huifa Shi, Shuzhang Niu, Wei Lv, Guangmin Zhou, Chen Zhang, Zhenhua Sun, Feng Li, Feiyu Kang, Quan-Hong Yang
      A high areal sulfur loading in a carbon-based cathode together with a high cell capacity is key to the design of lithium-sulfur batteries guaranteeing a superior energy density for use. However, a high sulfur loading produced using traditional blade coating techniques results in many technical issues such as sluggish electron/ion transport kinetics and cracking of the electrodes. Here a well designed two-step electrostatic spray deposition (ESD) technique is proposed to prepare a flexible, multilayer carbon electrode with a high sulfur areal loading, in which different carbon components by a careful selection are used for different functions in each layer. The unique "aerosol deposition" in the ESD creates buffer voids in the electrode, ensuring fast infiltration of the electrolyte and releasing the internal stress of the electrode thus avoiding the cracking of thick electrodes. With such an integrated design, the as-prepared cathode exhibits excellent flexibility, a long cyclic stability with a low capacity decay of 0.064% per cycle at 1 C for 500 cycles and a high rate capability of 736 mAh g−1 at 2 C. Moreover, a high areal sulfur loading of 9.4 mg cm−2 with an areal capacity of 6.2 mAh cm−2 at 0.1 C has been achieved.
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      PubDate: 2018-06-12T06:10:17Z
       
  • Enhanced electrical and thermal conductivities of silicon oxycarbide
           nanocomposites containing carbon nanofibers
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): M.A. Mazo, A. Tamayo, A.C. Caballero, J. Rubio
      Novel silicon oxycarbide-carbon enriched composites (SiOC-C) were prepared from mixtures of SiOC and different amounts of carbon nanofibers (CNF) (0–10%) sintered through spark plasma sintering at 1500 °C. During sintering, the SiOC matrix experiences a rearrangement to SiO2, SiC and C, and the growth of SiC wires within the material which produce epitaxial graphene-like carbon flakes with AB stacking. Small additions of CNFs (0.5–1%) promote the generation of large amounts of β-SiC which produce more graphene-like carbon. When large amounts of CNFs are added graphene-like carbon and also huge entanglements of turbostratic carbon are formed widespread all over the SiOC-C material. These facts deeply influenced the observed properties. Small additions of CNFs (0.5–1%) produce an improvement of the thermal conductivity of 30% and an enhancement of three orders of magnitude in the electrical conductivity (2.44 × 10−3 to 1.82 Sm-1) mainly due to a great increase in both the crystallite size and structural order of SiC and also the presence of graphene-like carbon homogenously dispersed within the SiOC matrix. Further additions of CNFs (10%) continue increasing both thermal and electrical conductivities (40% and 100 Sm-1, respectively) but such increases are less effectively by the presence of entanglements of turbostratic carbon.
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      PubDate: 2018-06-12T06:10:17Z
       
  • Transferrable polymeric carbon nitride/nitrogen-doped graphene films for
           solid state optoelectronics
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Xin Gan, Ruitao Lv, Tianyi Zhang, Fu Zhang, Mauricio Terrones, Feiyu Kang
      Polymeric carbon nitride (PCN) is a stable semiconducting material with an intermediate band gap (2–3 eV), which is efficient for catalysis and optoelectronics. However, it is still a big challenge to synthesize large-area and transferrable PCN films for applications in solid state optoelectronics. In this work, by using nitrogen-doped graphene (NG) as a van der Waals epitaxial substrate, centimeter-size PCN films are synthesized via polymerization of melamine molecules. As-grown PCN/NG films can be then transferred onto other substrates (e.g. SiO2/Si wafers, quartz slides, polymer substrates). Structural characterization reveals a polymerized structure of PCN films with nitrogen-containing heterocycles. By stacking PCN/NG films with graphene films, it is possible to construct a photodetector responsive to near-UV and UV illumination under ambient conditions. The responsivities of the photodetector are 0.59 mA/W and ∼30 μA/W towards 365 nm lamp and 488 nm laser, respectively. Our PCN photodetectors also show fast response times (e.g. ∼0.29 s to 488 nm laser illumination). Furthermore, our PCN photodetector can be fabricated on polymer substrates. As-obtained flexible photodetectors can maintain its photo-response after 100 times bending. Our results clearly demonstrate the possibility of employing large-area carbon-based semiconductors to meet the increasing demands of wearable and portable electronics.
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      PubDate: 2018-06-12T06:10:17Z
       
  • In situ direct growth of graphene/hexagonal boron nitride heterostructure
           on SiO2 substrate without metal catalyst
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Qinke Wu, Joohyun Lee, Jia Sun, Young Jae Song
      Here, we report the in situ direct growth of a graphene/hexagonal boron nitride (hBN) heterostructure on a SiO2 substrate without a metal catalyst by chemical vapor deposition (CVD). The hBN could be grown easily on a SiO2 substrate, while graphene growth was difficult and time-consuming as graphite could be grown only partially on the dielectric substrate, even after 5 h. Graphene was grown directly on this hBN/SiO2 substrate sequentially, which demonstrated easy and quick growth of a fully covered and high-quality graphene multilayer film within 40 min. The effect of hydrogen on the direct growth of hBN on a SiO2 substrate was also studied, and it was found that when a higher flow rate of hydrogen was used, the domain size was larger and higher quality of hBN could be grown. The quality of the grown hBN and graphene/hBN samples were confirmed by UV–vis, Raman, and atomic force microscopy (AFM). This new method can be used for graphene multilayer coating on dielectric substrates, on which it is difficult to grow graphene directly, for industrial or scientific applications.
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      PubDate: 2018-06-12T06:10:17Z
       
  • Graphene photodetector with polydiacetylenes acting as both
           transfer-supporting and light-absorbing layers: Flexible, broadband,
           ultrahigh photoresponsivity and detectivity
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Qian-Min Wang, Zhi-Yong Yang
      Polydiacetylene (PDA) films are shown enabling the combination of graphene transfer and photodetector fabrication into one step. Under the assistance of PDA, centimeter pieces of graphene can be acquired with free of broken or fractures. The constructed PDA/graphene hybrid films demonstrate ultrahigh, gate-tunable responsivity (R) and detectivity (D*) from UV to visible wavelengths, for instance, statistical R and D* at 320 nm achieves 556 A W−1 and 6.0*1011 Jones at the irradiance of 0.24 mW cm−2, indicating their superior broadband and sensitive detecting abilities. Kinetic response of our devices is not fast as the cost of high responsivity, which, however, can be efficiently amended by applying potential pulses through back gate electrodes. If supported PDA/graphene films on polymer substrate, the devices can still work reliably after being bended 25,000 cycles, and even can respond to light stimulus evidently at a heavily-stretched state created by a completely-folded human finger, revealing their remarkable flexibilities. The developed strategy of killing two birds (graphene transfer and functionalization) with one stone (PDA films) is highly desirable for developing graphene devices. And, the constructed ultrasensitive PDA/graphene photodetectors have considerable opportunities to be used in assorted photosensing areas that may not have critical requirement on operating speed.
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      PubDate: 2018-06-12T06:10:17Z
       
  • BiVO4 quantum tubes loaded on reduced graphene oxide aerogel as efficient
           photocatalyst for gaseous formaldehyde degradation
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Jianlong Yang, Qiujin Shi, Rui Zhang, Mingzheng Xie, Xiao Jiang, Fangcong Wang, Xiuwen Cheng, Weihua Han
      For efficient degradation of gaseous formaldehyde, BiVO4 (BVO) quantum tubes (QTs) were successfully synthesized and loaded on reduced graphene oxide (rGO) aerogel as a composite photocatalyst. Benefit from the band-gap widening effect in nanostructured BVO, the BVO-QTs can generate energetic photoelectrons required by oxygen reduction. The coupled rGO-aerogel would serve as a fast transfer path for photogenerated electrons, and thus promote the separation rate. Our results show that the composite photocatalyst has a favorable catalytic performance which can degrade formaldehyde from 1.0 ppm to 0.4 ppm in 15 min. The catalytic activity has been significantly improved compared with pristine BVO-QTs and bulk BVO. Moreover, the composite photocatalyst could be reused conveniently with undiminished performance profit from the unique 3D structures of aerogels, which are stable and favorable to the dispersion of BVO-QTs. This work provides a useful model for designing efficient photocatalyst for volatile organic compounds removal.
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      PubDate: 2018-06-12T06:10:17Z
       
  • Flame-assisted chemical vapor deposition for continuous gas-phase
           synthesis of 1-nm-diameter single-wall carbon nanotubes
    • Abstract: Publication date: November 2018
      Source:Carbon, Volume 138
      Author(s): Shohei Okada, Hisashi Sugime, Kei Hasegawa, Toshio Osawa, Shohei Kataoka, Hiroki Sugiura, Suguru Noda
      Flame synthesis enables the mass-production of carbon black and fullerene but not of carbon nanotubes (CNTs) due to the narrow window for producing CNTs while preventing tar generation. We report a flame-assisted chemical vapor deposition method, in which a premixed flame is used for the instantaneous generation of floating catalysts, the heating of the gas, and the growth of single-wall CNTs (SWCNTs) using a furnace at the downstream of the flame. This method yields high quality SWCNTs with a small average diameter of 0.96 nm, a small diameter deviation of 0.21 nm, and a high carbon purity of ∼90 wt%. Multiple parameters affect the SWCNT production significantly, which are investigated systematically and optimized carefully. The effects and possible mechanisms of the key parameters are discussed.
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      PubDate: 2018-06-06T22:13:27Z
       
  • Mapping carbon nanotube orientation by fast fourier transform of scanning
           electron micrographs
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Eileen Brandley, Emile S. Greenhalgh, Milo S.P. Shaffer, Qianqian Li
      A novel method of applying a two-dimensional Fourier transform (2D-FFT) to SEM was developed to map the CNT orientation in pre-formed arrays. Local 2D-FFTs were integrated azimuthally to determine an orientation distribution function and the associated Herman parameter. This approach provides data rapidly and over a wide range of lengthscales. Although likely to be applicable to a wide range of anisotropic nanoscale structures, the method was specifically developed to study CNT veils, a system in which orientation critically controls mechanical properties. Using this system as a model, key parameters for the 2D-FFT analysis were optimised, including magnification and domain size; a model set of CNT veils were pre-strained to 5%, 10% and 15%, to vary the alignment degree. The algorithm confirmed a narrower orientation distribution function and increasing Herman parameter, with increasing pre-strain. To validate the algorithm, the local orientation was compared to that derived from a common polarised Raman spectroscopy. Orientation maps of the Herman parameter, derived by both methods, showed good agreement. Quantitatively, the mean Herman parameter calculated using the polarised Raman spectroscopy was 0.42 ± 0.004 compared to 0.32 ± 0.002 for the 2D-FFT method, with a correlation coefficient of 0.73. Possible reasons for the modest and systematic discrepancy were discussed.
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      PubDate: 2018-05-31T05:44:30Z
       
  • Removal of formaldehyde on carbon -based materials: A review of the recent
           approaches and findings
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): S. Suresh, Teresa J. Bandosz
      Formaldehyde, HCHO, is one of the most common toxic pollutants found in indoor air. Its most common sources are pressed woods and particle boards. National Toxicology Program of Department of Health and Human Services classifies formaldehyde as human carcinogen and its exposure limit is 0.08 ppm for 30 min. So far, besides room venting, no other means have been recommended by Consumer Products Safety Commission to minimize indoor HCHO exposure. Since adsorption seems to be an efficient and cost-effective method of HCHO removal, in this review we summarize the findings on the applications of carbonaceous materials (mainly activated carbons, carbon fibers and their composites with an inorganic phase) as formaldehyde adsorbents from indoor air. Besides experiments, recent theoretical and simulation results are also discussed. Our intention is to use them as a basis for a further development of the next generation of efficient and cost-effective carbon-based reactive adsorbents where adsorption of HCOH will be combined with its mineralization at ambient conditions.
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      PubDate: 2018-05-28T11:10:09Z
       
  • Photoinduced pure spin-current in triangulene-based nano-device
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Hao Jin, Jianwei Li, Tao Wang, Yunjin Yu
      Triangulene has drawn great attention due to its extraordinary chemical and material properties. This magnetic molecule has the ferromagnetic ground state due to its two unpaired π electrons, making it suitable for spintronic applications. In this work, a triangulene based spin-photovoltaic device is proposed using a two-probe model. The quantum transport and spin current in triangulene device under the light irradiation are investigated based on the density functional theory combined with the nonequilibrium Green's functions. We finds that by adjusting photon energy ( E p h ) and gate voltage ( V g ), the proposed device can produce large pure spin current without charge current. The origin of the pure spin current is also analyzed based on the through-bond mechanism. Our work may provide theoretical reference for design of novel spintronic device with high performance.
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      PubDate: 2018-05-28T11:10:09Z
       
  • Self-assembled complexes of graphene oxide and oxidized vapor-grown carbon
           fiber for simultaneously enhancing the strength and toughness of epoxy and
           multi-scale carbon fiber/epoxy composites
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Guodong Zhou, Huichao Yao, Yang Zhou, Weitao Wang, Mao Peng
      Reinforcement of polymers with small addition of nanofillers has been intensively investigated. It has been suggested that combination of few-layer graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) is more effective than single nanofillers for polymer reinforcement. Herein, we report that the complexes of single-layer graphene oxide (GO) and oxidized vapor-grown carbon fibers (OVGCFs), with dimensionalities of 2 and 1, respectively, simultaneously improve the strength and toughness of epoxy and multi-scale carbon fiber reinforced composites at an extremely low content (∼0.2 wt%). The GO-OVGCF complexes are formed in water by the π-π stacking-induced self-assembly of OVGCFs and GO, and then rapidly transferred to a tertiary amine type epoxy oligomer for the preparation of epoxy and multi-scale composites. OVGCFs were observed to be wrapped by small GO sheets, which greatly improve the dispersion uniformity of OVGCFs in epoxy matrix and the filler-matrix interfacial interactions. The influences of the complexes with various GO-to-OVGCF ratios on the mechanical properties of epoxy and multi-scale composites were investigated systematically. At the optimized GO-to-OVGCF ratio, the complexes increase the mechanical properties of epoxy and multi-scale composites more significantly than previously reported individual nanofillers and the CNT-GNP hybrids.
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      PubDate: 2018-05-28T11:10:09Z
       
  • "Alternated cooling and heating" strategy enables rapid fabrication of
           highly-crystalline g-C3N4 nanosheets for efficient photocatalytic water
           purification under visible light irradiation
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Shifei Kang, Lu Zhang, Maofen He, Yuanyi Zheng, Lifeng Cui, Di Sun, Bing Hu
      Highly-crystalline 2-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets with low structural imperfection usually possess high photocatalytic activity that benefits from the suppressed electron–hole recombination. However, the conventional exfoliation strategy is incapable for fast and clean preparation of such highly-quality g-C3N4 nanosheets from their bulk-type counterparts. Herein, highly-crystalline few-layer g-C3N4 nanosheets were synthesized only within 10 min by judiciously combining flash freezing and microwave-assisted thermo-exfoliation. Physicochemical characterization showed the ultrathin g-C3N4 nanosheets had high crystallinity, narrowed band gap (2.62 eV), enlarged specific surface area (88.59 m2/g) and enhanced electron transport ability. The quasi-2D few-layer g-C3N4 nanosheets were more efficient than bulk g-C3N4 in photocatalytic water purification and disinfection, as evidenced by 3-fold enhancement in humic acid photodegradation and fast water disinfection against Escherichia coli under visible-light irradiation. Such improvements were mainly attributed to the reduction of structural defects and enrichment of exposed active sites, which together led to efficient self-suppression of electron–hole recombination. These findings provide an inspiration for scale-up and clean production of highly-active 2D materials towards environmental and biological application.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Turning gelidium amansii residue into nitrogen-doped carbon nanofiber
           aerogel for enhanced multiple energy storage
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Daohao Li, Yu Wang, Yuanyuan Sun, Yun Lu, Shuai Chen, Bingbing Wang, Huawei Zhang, Yanzhi Xia, Dongjiang Yang
      Three-dimensional (3D) carbonaceous aerogels assembled by one-dimensional (1D) carbon nanofibers (CNF) have attracted much attention, because their unique interconnected and hierarchical porous structure can offer a wide range of applications in environmental remediation and energy storage. Herein, the residue of gelidium amansii (mainly endofibers, ∼1.6 μm) after extraction of agar were used as precursor to fabricate nanofibrilated cellulose by using facile ultrosonication treatment. The nanofibrilated celluloses are highly engineered nanofibers with average diameter of ∼90 nm. Then the 1D cellulose nanofibers could be assembled into 3D nanofiber aerogels after freeze drying. The subsequent pyrolysis in NH3 and activition could result in the formation of N-doped CNF areogel (N-PCNFA), where the oxygen-containing groups in cellulose macromolecules converted to H2O, CO, and CO2. The N-PCNFA with hierarchically porous structure, high surface area (2290 m2 g−1), N-doping, and 3D interconnected channels are beneficial to electrolyte ions and electron transportation. The N-PCNFA displayed high capacity and long-term stability as energy storage material. This work highlights a new strategy in highly efficient utilizing the marine biomass waste for developing low-cost and functional carbon aerogel for multiple energy storage.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • PEGlated graphene as nanoadditive for enhancing the tribological
           properties of water-based lubricant
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Yiwen Hu, Yongxin Wang, Zhixiang Zeng, Haichao Zhao, Xuewu Ge, Kai Wang, Liping Wang, Qunji Xue
      Dispersion of Graphene in water is conducive to their practical applications as lubricating additive in water-based fluids due to their safety, low cost and environmental-friendliness. But owing to its hydrophobicity, it is difficult to achieve stable aqueous graphene suspension. Here, we use the Toluene-2,4-diisocyanate as bridging agent between hydrophilic Poly (ethylene glycol) (PEG) and ethanolamine to prepare the amino-containing PEG (PEG-NH2), followed by covalently grafting PEG-NH2 onto the surface of carboxylaed graphene (G-COOH) nanosheets to synthesize the PEGlated graphene (PEG-G) via facile amidation under mild conditions. The physical, chemical properties of product were characterized by Fourier transformed infrared spectra (FTIR), Raman spectra, X-ray photo electron spectroscopy (XPS) and so on. Transmission electron microscopy (TEM) and scanning probe microscope (SPM) were utilized to observed the morphology of G-COOH and PEG-G. The frictional properties of PEG-G as nanoadditive of water-based lubricant were characterized by UMT-3 tribometer, following with analyzes on wear surfaces by 3D laser scanning confocal microscopy. Based on the results of characterization, the PEG-G was prepared successfully and the dispersion shows superior friction-reducing and anti-wear properties owing to the formation of fluid adhesive film and carbon protective film, especially the concentration of PEG-G in water is 0.05 wt%.
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      PubDate: 2018-05-28T11:10:09Z
       
  • Structure effects of sp2-rich carbon films under super-low friction
           contact
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Yongfu Wang, Kaixiong Gao, Bin Zhang, Qi Wang, Junyan Zhang
      Driven by the advent of fullerenes, carbon nanotubes and graphene, designing or tailoring sp2-rich carbon clusters in carbon based films attains very interesting properties which can be ideal in various applications. Depositing sp2-rich clusters evolve toward a three-dimensional arrangement (composed of extended, bent, and cross-linked graphite basal planes, i.e. fullerene-like carbon (FLC)) or nanocrystalline planar graphitic configurations with the promotion in size and ordering of six-membered ring clusters (i.e. graphite-like carbon (GLC)). However, the films are studied separately and their structure effects on sliding-induced structure changes has never enjoyed elaboration. Here we built the self-mated friction groups of single structural films coated at two sliding surfaces, and designed a smart device to gather the transformed products under different load and sliding cycles. Super-low friction was realized under higher load by low-shear strength from graphene formed at the GLC interface (0.005), or reduced contact area from spherical nanoparticles with outer graphite shells produced at the FLC interface (0.009), resulting by different rehybridization pathways from different film structures. The role of film and rehybridized structures under super-low friction contact was discussed. The results could enrich the understanding of friction-induced rehybridization mechanism and help to deposit suitable films to significantly reduce friction.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • N-graphdiyne two-dimensional nanomaterials: Semiconductors with low
           thermal conductivity and high stretchability
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Bohayra Mortazavi, Meysam Makaremi, Masoud Shahrokhi, Zheyong Fan, Timon Rabczuk
      Most recently, N-graphdiyne two-dimensional (2D) nanomaterials were successfully experimentally realized at the gas/liquid and liquid/liquid interfaces. We accordingly conducted density functional theory (DFT) and molecular dynamics simulations to explore the mechanical/failure, thermal conductivity and stability, electronic and optical properties of three N-graphdiyne nanomembranes. Our DFT results of uniaxial tensile simulations reveal that these monolayers can yield remarkably high stretchability or tensile strength depending on the atomic structure and loading direction. Studied N-graphdiyne nanomembranes were found to exhibit semiconducting electronic character, with band-gap values ranging from 0.98 eV to 3.33 eV, based on the HSE06 estimations. The first absorption peak suggests that these 2D structures can absorb visible, IR and NIR light. Ab initio molecular dynamics results reveal that N-graphdiyne 2D structures can withstand at high temperatures, like 2000 K. Thermal conductivities of suspended single-layer N-graphdiyne sheets were predicted to be almost temperature independent and about three orders of magnitude smaller than that of the graphene. The comprehensive insight provided by this work highlights the outstanding physics of N-graphdiyne 2D nanomaterials, and suggest them as highly promising candidates for the design of novel stretchable nanodevices.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Chitosan/phytic acid hydrogel as a platform for facile synthesis of
           heteroatom-doped porous carbon frameworks for electrocatalytic oxygen
           reduction
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Guoliang Liu, Zhiming Liu, Jinlei Li, Min Zeng, Zhiyun Li, Lin He, Fuwei Li
      Development of heteroatom-doped porous carbon frameworks derived from renewable biomaterials is highly desirable. Here we report phytic acid-chitosan (PA-CS) hydrogel as a platform for facile preparation of N, P dual-doped porous carbon networks via direct pyrolysis. The hydrogel system shows great versatility towards incorporating graphene oxide or metal ions, providing a way to introduce graphene sheets or metal nanoparticles into carbon matrix as needed. After the incorporation of graphene, the obtained N, P dual-doped carbon/graphene (NPC/G) sample shows a large specific surface area (1824 m2 g−1), with a mixed meso- and micro-pore volume of 1.04 cm3 g−1. Importantly, the NPC/G sample exhibits high activity towards electrochemical oxygen reduction reaction in both alkaline and acidic electrolyte, ensuring a high-performance air catalyst of primary zinc-air batteries. Hopefully, this work provides a new method for the preparation of porous carbon materials with desired properties for catalysis.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Strong and super-hydrophobic hybrid carbon nanotube films with superior
           loading capacity
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Feifei Chen, Yi Jia, Qinggong Wang, Xiaobing Cao, Yahui Li, Yi Lin, Xian Cui, Jinquan Wei
      Superhydrophobic surface has attracted enormous interests due to its attractive potential applications. Here, we prepare all carbon nanotube hybrid films simply by depositing multi-walled carbon nanotubes on strong single-walled carbon nanotube films through vacuum filtration. The hybrid films behave some exciting superhydrophobic properties of a large water contact angle of 152° and an ultra-low sliding angle of only 2°. The rebounding height of a water droplet dipping from 5 cm above the hybrid film reaches 9.4 mm, which is 3 times that of on the natural lotus leaf. The superhydrophobic hybrid film also have high specific loading capacity of 627 g/g, more than 12 times that of the natural lotus leaf. The hybrid films can mimic lotus leaf in water repelling, self-cleaning, and carrying heavy things quite well.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Highly porous defective carbons derived from seaweed biomass as efficient
           electrocatalysts for oxygen reduction in both alkaline and acidic media
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Yajuan Hao, Xu Zhang, Qifeng Yang, Kai Chen, Jun Guo, Dongying Zhou, Lai Feng, Zdeněk Slanina
      In this work, we report a series of defective carbon catalysts prepared through a facile and scalable “N-doping-removal” process using seaweed biomass sodium alginate (SA) as precursor. Our systematic studies reveal that the defect content, porosity characteristic and conductivity of defective carbons can be finely tuned by manipulating the pyrolysis temperature and viscosity of precursor polymer SA, which significantly affect the ORR performance. The optimized defective porous carbon catalyst (i.e., D-PC-1(900)) that was revealed to possess abundant ORR-active defects, large surface area of 1377 m2g-1, abundant hierarchical porosity and good conductivity, exhibited very nice ORR activity and selectivity in 0.1 M KOH, comparable to the commercial Pt/C catalyst. In 0.5 M H2SO4, considerable ORR activity was also observed for D-PC-1(900), which is among the highest reported for defective carbons and comparable to many of N-doped carbons. Density functional theory calculations indicate that the carbon defect can create the active sites for ORR in acidic media. More importantly, in both alkaline and acidic media, D-PC-1(900) shows much better stability and methanol tolerance than those of the Pt/C catalyst. All these results demonstrate that the seaweed biomass derived defective carbon is an excellent candidate for non-precious-metal ORR catalyst in various fuel cells.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Excellent mechanical properties of long length multiwalled carbon nanotube
           bridged Kevlar fabric
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Sushant Sharma, Abhishek K. Pathak, Vidya Nand Singh, Satish Teotia, S.R. Dhakate, B.P. Singh
      The major causes of failure of Kevlar reinforced composites are inter-yarn slippage and poor adhesion with polymer. Herein, long length multiwalled carbon nanotubes (MWCNTs) are used as a secondary reinforcement to enhance the interfacial interaction between Kevlar and epoxy through bridging action. Different wt. % of MWCNT based Kevlar reinforced hybrid composite tape and their laminar composites have been prepared and their quasi-static unidirectional and dynamic mechanical properties are studied. It is found that the maximum tensile strength, Young's modulus and storage modulus of optimized i.e. 0.3 wt % of MWCNTs in epoxy resin (0.3KE) composite showed an overall improvement of ∼81%, ∼56% and ∼139%, respectively over base line composite tape (KE). The flexural modulus, Young's modulus and storage modulus of 0.3 wt % multi-scaled laminar composite (KEC) showed an overall improvement of ∼33%, ∼50%, and ∼233%, respectively over KE. The effects of MWCNTs on interfacial properties of multi-scaled composite tapes are correlated by Raman spectral shift, FTIR and XRD analysis. Further the bridging actions of long length MWCNTs are visualized by using high resolution transmission electron microscopy.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Substrate effect on electrical conductance at a nanoasperity-graphene
           contact
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Xiaoli Hu, Jihyung Lee, Diana Berman, Ashlie Martini
      The use of graphene for applications such as micro- and nano-scale electronic devices often involves incorporating the two-dimensional material onto various substrates. However, the effects of the substrate's mechanical properties on electrical contact conductance are not fully understood. Here, we explore these effects by measuring the conductance between a nanoscale probe and a single layer of graphene with three different levels of substrate support: no substrate, i.e. free-standing graphene, an elastic substrate, and a rigid substrate. These three systems are studied using conductive atomic force microscopy experiments complemented by molecular dynamics simulations using the electrochemical dynamics with implicit degrees of freedom method. In both experiments and simulations, at a given normal force, current increases as: rigid substrate < elastic substrate < no substrate. We demonstrate that the substrate support influences graphene/tip contact conductance through substrate's elasticity, which determines contact size, as well as through variability of interatomic distances in the contact, which contributes to the interface resistivity.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Single exposure to aerosolized graphene oxide and graphene nanoplatelets
           did not initiate an acute biological response in a 3D human lung model
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Barbara Drasler, Melanie Kucki, Flavien Delhaes, Tina Buerki-Thurnherr, Dimitri Vanhecke, Daria Korejwo, Savvina Chortarea, Hana Barosova, Cordula Hirsch, Alke Petri-Fink, Barbara Rothen-Rutishauser, Peter Wick
      The increased mass production of graphene related materials (GRM), intended for a broad spectrum of applications, demands a thorough assessment of their potential hazard to humans and the environment. Particularly, the paramount concern has been expressed in regard to their interaction with the respiratory system in occupational exposure settings. It has been shown that GRM are easily respirable and can interact with lung cells resulting in the induction of oxidative stress or pulmonary inflammation. However, a comprehensive assessment of potential biological effects induced by GRM is currently hardly feasible to accomplish due to the lack of well-defined GRM materials and realistic exposure data. Herein, a 3D human lung model was combined with a commercial aerosolization system to study potential side effects of GRM. Two representative types of GRM were aerosolized onto the lung epithelial tissue surface. After 24 h post exposure, selected biological endpoints were evaluated, such as cell viability, morphology, barrier integrity, induction of (pro-)inflammation and oxidative stress reactions and compared with the reference material carbon black. Single exposure to all tested GRM at the two different exposure concentrations (∼300 and 1000 ng/cm2) did not initiate an observable adverse effect to the 3D lung model under acute exposure scenarios.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Facile laser fabrication of high quality graphene-based
           microsupercapacitors with large capacitance
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Soongeun Kwon, Yeoheung Yoon, Junhyoung Ahn, Hyungjun Lim, Geehong Kim, Jae-Hyun Kim, Kee-Bong Choi, JaeJong Lee
      We have demonstrated facile laser fabrication of high quality graphene-based microsupercapacitors (MSCs) by carbon dioxide (CO2) laser-assisted reduction and successive ultraviolet (UV) pulsed laser direct carving of a graphene oxide (GO) film. Irradiation of GO films by a high power CO2 laser generated high quality laser reduced graphene oxide (LrGO) films with fewer defects (ID/IG = 0.24) and excellent expansion ratio (∼16) suitable for a large capacitance electrode. UV laser direct carving was applied to fabricate a high resolution interdigitated electrode (IDE) pattern of an LrGO film (LrGO-IDE) with both the minimum electrode width and gap between the electrodes, being as small as 50 μm. A typical MSC based on the LrGO-IDE shows large areal specific capacitance of 32.6 mF cm−2 at a scan rate of 10 mV s−1 and 29.8 mF cm−2 at a current density of 0.2 mA cm−2, outperforming most rGO-based MSCs. Moreover, the electrochemical performance of the MSCs based on LrGO-IDEs is greatly improved by minimizing the electrode width in the same electrode footprint. High resolution IDE patterns composed of the high quality LrGOs developed here can be further applied for high power pseudo-capacitors by incorporating pseudo-capacitive materials into the porous LrGO structure.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Uniform dispersion and interface analysis of nickel coated graphene
           nanoflakes/ pure titanium matrix composites
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): X.N. Mu, H.N. Cai, H.M. Zhang, Q.B. Fan, F.C. Wang, Z.H. Zhang, Y.X. Ge, R. Shi, Y. Wu, Z. Wang, D.D. Wang, S. Chang
      An increasing number of reports have demonstrated enormous strength enhancements in titanium matrix composites (TiMCs) reinforced with graphene nanoflakes (GNFs) on account of the superior mechanical properties of GNFs. Unfortunately, the difficulty of uniform dispersion and severe interfacial reaction are simultaneously the most challenging and serious issues in GNFs reinforced TiMCs. In this work, we applied electroless plating method to prepare Ni decorated GNFs (Ni-GNFs) as a reinforcement in Ti matrix to uniformly disperse the GNFs in Ti matrix and relieve the severe interfacial reaction between metal and carbon nanophase. The composite reinforced by low content Ni-GNFs (0.05 wt%GNFs) exhibiting ultimate strength of 793 MPa (+40% compared to monolithic pure Ti), have been processed by short time ball milling process followed by spark plasma sintering (SPS) and hot-rolling (HR). Enormous strength increase of the composite can be attributed to a homogeneous distribution of Ni-GNFs in the Ti matrix coupled with the formation of special interface (Ti/Ti2Ni/nano-TiCX/Ni-GNFs). The load transfer mechanism of Ni-GNFs in composites was investigated by in-situ tensile test, which shows the great interfacial load transfer capability. This work provides a new strategy for dispersion and interface analysis of GNFs reinforced Ti matrix composites.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • High-throughput screening for superhard carbon and boron nitride
           allotropes with superior stiffness and strength
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Shihao Zhang, Dominik Legut, Zhongheng Fu, Timothy C. Germann, Ruifeng Zhang
      In search of intrinsically superhard materials with superior stiffness and strength, we performed a comprehensive high-throughput hunting on hundreds of carbon and BN allotropes based on energetic and mechanical criteria. Our results suggest that at ambient pressure, an approximate linear relationship exists between the ideal strengths and elastic moduli in two allotrope regions with high elastic moduli, while no carbon (BN) allotrope can possess both superior stiffness and strength than diamond (c-BN). With further consideration of pressure induced stiffening and strengthening, it is interestingly found that the strength enhancement shows distinct characteristic trend, resulting in some intriguing ultra-stiffening and strengthening phenomena. In particular, a superdense carbon allotrope termed as tI12-C was unexpectedly discovered to possess superior stiffness and strength than diamond under high pressure. Electronic structure analysis indicates that an increasing charge accumulation appearing in tI12-C under pressure is responsible for its ultra-stiffening and strengthening phenomena, differing from the appearance of abnormal charge depletions and the accompanied metallization in diamond under applied strain. These findings provide a fundamental basis for screening the novel superhard carbon and BN allotropes based on mechanical criteria, and highlight the importance to understand the effect of strain tunable electronic structure on mechanical response of materials.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Hard carbons issued from date palm as efficient anode materials for
           sodium-ion batteries
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Ilyasse Izanzar, Mouad Dahbi, Manami Kiso, Siham Doubaji, Shinichi Komaba, Ismael Saadoune
      Sodium-ion batteries (SIBs) are among the most promising candidates for large-scale electrical energy storage devices owing to the low cost, abundance, and widespread of sodium resources. However, finding a suitable anode material is a critical necessity to uphold the commercialisation of SIBs. Herein, we report a facile synthesis process to prepare hard carbons derived from date palm biomass consisting of direct pyrolysis of seeds or pulp at different heat treatment temperatures in the range between 800 and 1400 °C. The electrochemical performances of the prepared hard carbons were investigated in SIBs and exhibited high reversible capacity of 300 mAh g−1 and promising initial coulombic efficiency (ICE) of 88.4%, which is the highest ICE reported for hard carbon materials to date. This work is the first to report a successful implementation of date palm as precursor to prepare low cost and high performance hard carbon anode materials for SIBs.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride
           quantum dots (CNFQDs) for visible light driven water splitting
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Pawan Kumar, Ujwal Kumar Thakur, Kazi Alam, Piyush Kar, Ryan Kisslinger, Sheng Zeng, Sahil Patel, Karthik Shankar
      Graphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and transfer of holes to the aqueous electrolyte. CNFQD-sensitized TiO2 nanorods exhibited a strong photoelectrochemical response up to 500 nm. Reuse experiments confirmed robustness and long term stability of the sample without exhausting the catalytic performance. The present work demonstrates a new pathway to sensitize TiO2 to visible photons by the in situ formation of embedded heterojunctions with fluorine doped carbon nitride quantum dots.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
  • Temperature-independent piezoresistive sensors based on carbon
           nanotube/polymer nanocomposite
    • Abstract: Publication date: October 2018
      Source:Carbon, Volume 137
      Author(s): Shen Gong, Di Wu, Yixuan Li, Mengyin Jin, Tao Xiao, Yang Wang, Zhu Xiao, Zhenghong Zhu, Zhou Li
      Temperature-independent property and high piezoresistivity are critical for carbon nanotube polymer nanocomposites with sensing capability. In this work, a temperature-independent CNT/Epoxy resin nanocomposite was fabricated successfully. This composite has good and stable piezoresistivity between 233 K and 373 K. By developing a multi-scale percolation network model, this work also reveals theoretically the inherent mechanisms to obtain temperature-independent sensors. In order to fully consider the tube–tube and/or tube–matrix interaction in the composite, the structural distortion of nanotubes is determined self-consistently by minimizing the pseudo-potential energy and the thermally assisted tunneling transport is calculated by the Landauer-Büttiker formula. Simulation results show that temperature-independent composite with further improved piezoresistivity (gauge factor > 40) can be achieved by dispersing the treated and selected CNTs to the theoretically matched polymer matrix. These temperature-independent, highly sensitive, low cost and homogeneous sensors have a great potential for wide range applications, such as in electronic skin, man-machine interaction and body monitoring.
      Graphical abstract image

      PubDate: 2018-05-28T11:10:09Z
       
 
 
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