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  Subjects -> CHEMISTRY (Total: 810 journals)
    - ANALYTICAL CHEMISTRY (48 journals)
    - CHEMISTRY (564 journals)
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CHEMISTRY (564 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 4)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 31)
ACS Catalysis     Full-text available via subscription   (Followers: 25)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 13)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 8)
ACS Macro Letters     Full-text available via subscription   (Followers: 19)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 25)
ACS Nano     Full-text available via subscription   (Followers: 337)
ACS Photonics     Full-text available via subscription   (Followers: 6)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 9)
Acta Chemica Iasi     Open Access  
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 6)
Acta Chromatographica     Full-text available via subscription   (Followers: 10)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 4)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 10)
Advanced Functional Materials     Hybrid Journal   (Followers: 38)
Advances in Chemical Engineering and Science     Open Access   (Followers: 22)
Advances in Chemical Science     Open Access   (Followers: 9)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 15)
Advances in Drug Research     Full-text available via subscription   (Followers: 16)
Advances in Enzyme Research     Open Access  
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 12)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 16)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Science     Hybrid Journal   (Followers: 39)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 10)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 4)
African Journal of Chemical Education     Open Access   (Followers: 1)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 4)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 1)
Alchemy     Open Access   (Followers: 3)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
AMB Express     Open Access  
American Journal of Applied Sciences     Open Access   (Followers: 30)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 201)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 18)
American Journal of Plant Physiology     Open Access   (Followers: 10)
American Mineralogist     Full-text available via subscription   (Followers: 7)
Analyst     Full-text available via subscription   (Followers: 35)
Angewandte Chemie     Hybrid Journal   (Followers: 18)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 263)
Annales UMCS, Chemia     Open Access   (Followers: 2)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 1)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 2)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 11)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 12)
Applied Surface Science     Hybrid Journal   (Followers: 19)
Arabian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 4)
Autophagy     Full-text available via subscription   (Followers: 1)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 253)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 4)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 4)
Bioinspired Materials     Open Access  
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 30)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 24)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 14)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 13)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Carbohydrate Research     Hybrid Journal   (Followers: 11)
Carbon     Hybrid Journal   (Followers: 54)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 5)
Catalysis Science and Technology     Free   (Followers: 4)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 7)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Functional Materials     [SJR: 4.862]   [H-I: 136]
   [40 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1616-301X - ISSN (Online) 1616-3028
   Published by John Wiley and Sons Homepage  [1605 journals]
  • Novel Molybdenum Carbide–Tungsten Carbide Composite Nanowires and
           Their Electrochemical Activation for Efficient and Stable Hydrogen
           Evolution
    • Authors: Peng Xiao; Xiaoming Ge, Haibo Wang, Zhaolin Liu, Adrian Fisher, Xin Wang
      Pages: n/a - n/a
      Abstract: Development of nonnoble metal catalysts for hydrogen evolution reaction (HER) is critical to enable an efficient production of hydrogen at low cost and large scale. In this work, a novel bimetallic carbide nanostructure consisting of Mo2C and WC is synthesized. Based on a highly conductive WC backbone, nanosized Mo2C particles are integrated onto WC, forming a well‐defined and highly robust nanowire structure. More importantly, it is found that electrochemical activation can partially remove surface carbon and activate the catalyst by changing its surface hydrophilicity. As a result, the residual carbon contributes positively to the activity, besides its role of protecting carbide from oxidation. Benefiting from the structure, the catalyst achieves high activity, stable electrolysis towards HER. The well‐defined nanowire structure of complex molybdenum carbide–tungsten carbide is realized by a pseudomorphic transformation and exhibits high activity towards hydrogen evolution reaction after electrochemical activation.
      PubDate: 2015-01-27T08:30:16.282086-05:
      DOI: 10.1002/adfm.201403633
       
  • Lanthanide Ion Codoped Emitters for Tailoring Emission Trajectory and
           Temperature Sensing
    • Authors: Shu‐Na Zhao; Lei‐Jiao Li, Xue‐Zhi Song, Min Zhu, Zhao‐Min Hao, Xing Meng, Lan‐Lan Wu, Jing Feng, Shu‐Yan Song, Cheng Wang, Hong‐Jie Zhang
      Pages: n/a - n/a
      Abstract: A series of lanthanide metal‐organic frameworks (Ln‐MOFs) are synthesized through solvothermal conditions with 1,3‐bis(4‐carboxyphenyl)imidazolium (H2L). Owing to the lanthanide contraction effect, two different types of Ln‐MOFs, namely, {[Ln(L)2(OH)]·3H2O}n (Ln:Pr, Nd, Sm) and {[Ln(L)2(COO)(H2O)2]·H2O}n (Ln: Eu, Gd, Tb, Dy, Tm, Yb, Y), and their corresponding codoped Ln‐MOFs EuxTb1‐xL are obtained. With careful adjustment of the relative concentration of the lanthanide ions and the excitation wavelength, the color of the luminescence can be systematically modulated and white light emission can be further successfully achieved. Furthermore, by virtue of the temperature‐dependent luminescent behavior, Eu0.2Tb0.8L allows for the design of a thermometer with an excellent linear response to temperature over a wide range, from 40 to 300 K. This work highlights the practical applications of Ln‐MOFs for tailoring fluorescent color and even obtaining practical white light emission, and especially for sensing temperature as luminescent thermometers in a single framework by controlling in different ways. Codoped Ln‐metal‐organic frameworks EuxTb1‐xL are synthesized based on the isostructural Ln‐metal‐organic frameworks using lanthanide ion emitters. With careful adjustment of the relative concentration of the lanthanide ions and the excitation wavelength, the emission trajectory can be modulated, allowing white emission. Furthermore, Eu0.2Tb0.8L allows for the design of a thermometer operating over a wide range, from 40 to 300 K.
      PubDate: 2015-01-27T08:28:47.97862-05:0
      DOI: 10.1002/adfm.201402061
       
  • The Effect of Protein Fusions on the Production and Mechanical Properties
           of Protein‐Based Materials
    • Authors: Shang‐Pu Tsai; David W. Howell, Zhao Huang, Hao‐Ching Hsiao, Yang Lu, Kathleen S. Matthews, Jun Lou, Sarah E. Bondos
      Pages: n/a - n/a
      Abstract: Proteins implement most of the vital molecular functions of living organisms, including structural support, energy generation, biomolecule sensing, and chemical catalysis, storage, and degradation. While capturing proteins in materials could create devices that mimic these functions, this process is challenging due to the sensitivity of protein structure to the chemical environment. Using recombinant DNA methods, specific functions can be incorporated by fusing the gene encoding a self‐assembling protein and the desired functional protein, to produce a single polypeptide that self‐assembles into functionalized materials. However, the functional protein has the potential to disrupt protein production, protein assembly, and/or the structure and mechanical properties of the resulting materials. 24 fusion proteins are created based on Ultrabithorax, a Drosophila transcription factor that self‐assembles into materials in vitro. The appended proteins dictate the solubility and purification yield of the corresponding protein fusions. Any loss of solubility and yield can be mitigated by fusing a third protein that is highly soluble. All protein fusions self‐assemble equally well to produce materials with similar morphologies. Fusing enhanced green fluorescent protein to Ultrabithorax influences mechanical properties of the resulting fibers. It is concluded that a far wider range of proteins can be successfully incorporated into elastomeric protein‐based materials than originally anticipated. A wide range of proteins can be incorporated into protein‐based materials via gene fusion, to produce a single polypeptide capable of self‐assembly and the function of interest. 24 proteins are fused to Ultrabithorax, a protein which self‐assembles in vitro. Whereas the appended proteins determine the solubility and purification yield of the corresponding fusion protein, all fusion proteins self‐assemble equally well.
      PubDate: 2015-01-27T08:28:42.50166-05:0
      DOI: 10.1002/adfm.201402997
       
  • Conjugated Polymer Nanoparticles as Nano Floating Gate Electrets for High
           Performance Nonvolatile Organic Transistor Memory Devices
    • Authors: Chien‐Chung Shih; Yu‐Cheng Chiu, Wen‐Ya Lee, Jung‐Yao Chen, Wen‐Chang Chen
      Pages: n/a - n/a
      Abstract: A molecular nano‐floating gate (NFG) of pentacene‐based transistor memory devices is developed using conjugated polymer nanoparticles (CPN) as the discrete trapping sites embedded in an insulating polymer, poly (methacrylic acid) (PMAA). The nanoparticles of polyfluorene (PF) and poly(fluorene‐alt‐benzo[2,1,3]thiadiazole (PFBT) with average diameters of around 50–70 nm are used as charge‐trapping sites, while hydrophilic PMAA serves as a matrix and a tunneling layer. By inserting PF nanoparticles as the floating gate, the transistor memory device reveals a controllable threshold voltage shift, indicating effectively electron‐trapping by the PF CPN. The electron‐storage capability can be further improved using the PFBT‐based NFG since their lower unoccupied molecular orbital level is beneficial for stabilization of the trapped charges, leading a large memory window (35 V), retention time longer than 104 s with a high ON/OFF ratio of >104. In addition, the memory device performance using conjugated polymer nanoparticle NFG is much higher than that of the corresponding polymer blend thin films of PF/polystyrene. It suggests that the discrete polymer nanoparticles can be effectively covered by the tunneling layer, PMAA, to achieve the superior memory characteristics. A molecular nano‐floating gate approach using conjugated polymer nanoparticles is developed for achieving high performance transistor memory devices. The transistor memory device using discrete polyfluorene and poly(fluorene‐alt‐benzo[2,1,3]thiadiazole nanoparticles as the floating gates can effectively trap the electrons and lead to a large memory window, long retention time, and a high ON/OFF ratio of >104.
      PubDate: 2015-01-26T03:26:28.983972-05:
      DOI: 10.1002/adfm.201404329
       
  • Mesoporous Colloidal Superparticles of Platinum‐Group Nanocrystals
           with Surfactant‐Free Surfaces and Enhanced Heterogeneous Catalysis
    • Authors: Yongxing Hu; Yuzi Liu, Yugang Sun
      Pages: n/a - n/a
      Abstract: Synthesis of colloidal superparticles (CSPs) of nanocrystals, a class of assembled nanocrystals in the form of colloidal particles, has been emerging as a new frontier in the field of nanotechnology because of their potential novel properties originated from coupling of individual nanocrystals in CSPs. Here, a facile approach is reported for the controlled synthesis of mesoporous CSPs made of various platinum‐group nanocrystals that exhibit high colloidal stability and ligand‐free surfaces to significantly benefit their applications in solution‐phase heterogeneous catalysis. The synthesis relies on self‐limiting growth of composite particles through coprecipitation of both Pt‐group nanocrystals (or their precursor compounds) and silver halides on sacrificial substrates of colloidal silver particles. The intermediate silver halides in the composite particles play the critical role in limiting the continuous growth (and/or coalescence) of individual Pt‐group nanocrystals and they can be selectively dissolved to create nanoscale pores in the resulting CSPs. Colloidal superparticles consisting of platinum nanocrystals embedded in silver chloride matrix are synthesized through a self‐limited coprecipitation on sacrificial substrates of colloidal silver particles. ­Selective dissolution of silver chloride leads to the formation of porous superparticles of platinum with ligand‐free surfaces that are beneficial for solution‐phase heterogeneous catalysis.
      PubDate: 2015-01-23T11:33:17.91051-05:0
      DOI: 10.1002/adfm.201403664
       
  • Self‐Limited Switching in Ta2O5/TaOx Memristors Exhibiting Uniform
           Multilevel Changes in Resistance
    • Authors: Kyung Min Kim; Seung Ryul Lee, Sungho Kim, Man Chang, Cheol Seong Hwang
      Pages: n/a - n/a
      Abstract: To facilitate the development of memristive devices, it is essential to resolve the problem of non‐uniformity in switching, which is caused by the random nature of the filamentary switching mechanism in many resistance switching memories based on transition metal oxide. In addition, device parameters such as low‐ and high‐state resistance should be regulated as desired. These issues can be overcome if memristive devices have switching limits for both the low‐ and high‐resistance states and if their resistance values are highly controllable. In this study, a method termed self‐limited switching for uniformly regulating the values of both the low‐ and high‐resistance states is suggested, and the circuit configuration required for the self‐limited switching is established in a Ta2O5/TaOx memristive structure. A method of improving the uniformity of multi‐level resistance states in this memristive system is also proposed. A self‐limited switching circuit for uniformly regulating the resistance states is first suggested. This circuit, which is composed of memristor, switch, and resistor, is successfully established in a Ta2O5/TaOx structure. In this device, low‐ and high‐resistance states, and their intermediate resistance states are precisely regulated, and thus, multilevel switching is successfully achieved.
      PubDate: 2015-01-23T11:32:37.794036-05:
      DOI: 10.1002/adfm.201403621
       
  • Ultrafast All‐Polymer Electrically Tunable Silicone Lenses
    • Authors: Luc Maffli; Samuel Rosset, Michele Ghilardi, Federico Carpi, Herbert Shea
      Pages: n/a - n/a
      Abstract: Dielectric elastomer actuators (DEA) are smart lightweight flexible materials integrating actuation, sensing, and structural functions. The field of DEAs has been progressing rapidly, with actuation strains of over 300% reported, and many application concepts demonstrated. However many DEAs are slow, exhibit large viscoelastic drift, and have short lifetimes, due principally to the use of acrylic elastomer membranes and carbon grease electrodes applied by hand. Here a DEA‐driven tunable lens, the world's fastest capable of holding a stable focal length, is presented. By using low‐loss silicone elastomers rather than acrylics, a settling time shorter than 175 μs is obtained for a 20% change in focal length. The silicone‐based lenses show a bandwidth 3 orders of magnitude higher compared to lenses of the same geometry fabricated from the acrylic elastomer. Stretchable electrodes, a carbon black and silicone composite, are precisely patterned by pad‐printing and subsequently cross‐linked, enabling strong adhesion to the elastomer and excellent resistance to abrasion. The lenses operate for over 400 million cycles without degradation, and show no change after more than two years of storage. This lens demonstrates the unmatched combination of strain, speed, and stability that DEAs can achieve, paving the way for complex fast soft machines. Soft and electrically tunable lenses based on dielectric elastomer actuators are fabricated and exhibit settling time below 175 μs. Soft and compliant systems can also display fast response speed by a proper choice of materials and an adequate design. The lens, based on a low‐loss commercial silicone, is able to modulate its focal length by 20%.
      PubDate: 2015-01-23T11:31:48.285286-05:
      DOI: 10.1002/adfm.201403942
       
  • Transparent, Stimuli‐Responsive Films from Cellulose‐Based
           Organogel Nanoparticles
    • Authors: Yonggui Wang; Lars‐Oliver Heim, Yeping Xu, Gerd Buntkowsky, Kai Zhang
      Pages: n/a - n/a
      Abstract: The use of bio‐based nanoscaled cellulose for the construction of novel functional materials has progressed rapidly over the past years. In comparison to most of studies starting with the hydrophilic nanoscaled cellulose, surface‐stearoylated cellulose nanoparticles (SS‐CNPs) are used in this report for the construction of multifunctional, responsive films. SS‐CNPs with an average size of 115 ± 0.5 nm are obtained after the surface‐modification of cellulose under heterogeneous conditions. Crystalline cellulose core is present within SS‐CNPs according to solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy. SS‐CNPs show excellent dispersibility in nonpolar solvents and form temperature‐responsive organogels in tetrahydrofuran (THF) at low temperature or after long time storage at room temperature. Moreover, transparent and self‐standing films of SS‐CNPs from their THF‐suspension show solvent‐responsive surface wettability and responsive shape‐memory property. SS‐CNPs can also be used for the fabrication of nanocomposite films together with nonpolar compounds, such as (2‐stearoylaminoethyl) rhodamine B. Thus, these novel SS‐CNPs derived from sustainable cellulose fibers are promising candidates for the construction of novel functional materials. Novel cellulose‐based organogel nanoparticles, called surface‐stearoylated cellulose nanoparticles (SS‐CNPs), are synthesized after the surface esterification of cellulose fibers under heterogeneous reaction conditions. SS‐CNPs form stimuli‐responsive organogels and transparent, self‐standing films by solvent casting. The films show solvent‐responsive surface wettability, responsive shape‐memory properties as well as switchable optical colors by forming nanocomposite films containing stearoylated rhodamine spiroamide.
      PubDate: 2015-01-22T13:40:20.95653-05:0
      DOI: 10.1002/adfm.201403067
       
  • MoS2/Graphene Composite Anodes with Enhanced Performance for
           Sodium‐Ion Batteries: The Role of the Two‐Dimensional
           Heterointerface
    • Authors: Xiuqiang Xie; Zhimin Ao, Dawei Su, Jinqiang Zhang, Guoxiu Wang
      Pages: n/a - n/a
      Abstract: Graphene has been widely used as conformal nanobuilding blocks to improve the electrochemical performance of layered metal sulfides (MoS2, WS2, SnS, and SnS2) as anode materials for sodium‐ion batteries. However, it still lacks in‐depth understanding of the synergistic effect between these layered sulfides and graphene, which contributes to the enhanced electroactivity for sodium‐ion batteries. Here, MoS2/reduced graphene oxide (RGO) nanocomposites with intimate two‐dimensional heterointerfaces are prepared by a facile one‐pot hydrothermal method. The heterointerfacial area can be effectively tuned by changing the ratio of MoS2 to RGO. When used as anode materials for sodium‐ion batteries, the synergistic effect contributing to the enhanced reversible capacity of MoS2/RGO nanocomposites is closely related with the heterointerfacial area. The computational results demonstrate that Na prefers to be adsorbed on MoS2 in the MoS2/RGO heterostructure rather than intercalate into the MoS2/RGO heterointerface. Interestingly, the MoS2/RGO heterointerfaces can significantly increase the electronic conductivity of MoS2, store more Na ions, while maintaining the high diffusion mobility of Na atoms on MoS2 surface and high electron transfer efficiency from Na to MoS2. It is expected that the efforts to establish the correlation between the two‐dimensional heterointerface and the electrochemical sodium‐ion storage performance offer fundamental understanding for the rational design of layered metal sulfides/graphene composites as high‐performance electrode materials for sodium‐ion batteries. MoS2/reduced graphene oxide nano­composites are prepared as anode materials for sodium‐ion batteries. The performance of MoS2/reduced graphene oxide nano­composites is closely related to the heterointerfacial areas. Computational investigations reveal that the 2D MoS2/reduced graphene oxide heterointerface can increase the conductivity of MoS2, adsorb more Na atoms, and maintain high diffusion mobility of Na on MoS2 surface and electron transfer efficiency from Na to MoS2.
      PubDate: 2015-01-22T13:40:16.09979-05:0
      DOI: 10.1002/adfm.201404078
       
  • Hydrogen‐Terminated Si Nanowires as Label‐Free Colorimetric
           Sensors in the Ultrasensitive and Highly Selective Detection of Fluoride
           Anions in Pure Water Phase
    • Authors: Hui Wang; Pei‐Hong Fan, Bin Tong, Yu‐Ping Dong, Xue‐Mei Ou, Fan Li, Xiao‐Hong Zhang
      Pages: n/a - n/a
      Abstract: The detection of anions in pure water phase with colorimetric sensor is a long standing challenge. As one of the most important anions, F– is associated with nerve gases and the refinement of uranium for nuclear weapons. However, limited by its anions nature, few of the reported colorimetric sensors can successfully applied to detect F–1 in pure water phase. This work designs a colorimetric sensor for F–1 pure water phase detection by taking the advantages of the strong specific binding between F and Si, as well as the color‐changing property of H‐terminated Si nanowires (SiNWs). The sensor demonstrates ultra‐sensitivity, high selectivity, and good stability. The results reveal particular interest for the development of new type aqueous phase anions sensors with SiNWs. A colorimetric sensor for F−1 detection in pure water is investigated by taking advantage of the strong specific binding between F and Si, as well as the color change property of SiNWs with their diameter. The sensor demonstrates ultrasensitivity, high selectivity, and good stability.
      PubDate: 2015-01-22T13:40:04.018341-05:
      DOI: 10.1002/adfm.201401632
       
  • Torrent Frog‐Inspired Adhesives: Attachment to Flooded Surfaces
    • Authors: Jagoba Iturri; Longjian Xue, Michael Kappl, Luis García‐Fernández, W. Jon P. Barnes, Hans‐Jürgen Butt, Aránzazu del Campo
      Pages: n/a - n/a
      Abstract: Anatomic differences on the toe pad epithelial cells of torrent and tree frogs (elongated versus regular geometry) are believed to account for superior ability of torrent frogs to attach to surfaces in the presence of running water. Here, the friction properties of artificial hexagonal arrays of polydimethylsiloxane (PDMS) pillars (elongated and regular) in the presence of water are compared. Elongated pillar patterns show significantly higher friction in a direction perpendicular to the long axis. A low bending stiffness of the pillars and a high edge density of the pattern in the sliding direction are the key design criteria for the enhanced friction. The elongated patterns also favor orientation‐dependent friction. These findings have important implications for the development of new reversible adhesives for wet conditions. The friction of artificial hexagonal arrays of polydimethyl­siloxane pillars in the presence of water is studied. Arrays consisting of elongated pillars, resembling the structure of the toe pads of torrent frogs, are compared with arrays of hexagonal pillars as found in the toe pads of tree frogs. Elongated pillar patterns show significantly higher friction in a direction perpendicular to the long axis and favor orientation‐dependent friction.
      PubDate: 2015-01-22T13:39:54.242288-05:
      DOI: 10.1002/adfm.201403751
       
  • Magnetic Helical Microswimmers Functionalized with Lipoplexes for Targeted
           Gene Delivery
    • Authors: Famin Qiu; Satoshi Fujita, Rami Mhanna, Li Zhang, Benjamin R. Simona, Bradley J. Nelson
      Pages: n/a - n/a
      Abstract: Artificial micro‐/nanoswimmers have various potential applications including minimally invasive diagnosis and targeted therapies, environmental sensing and monitoring, cell manipulation and analysis, and lab‐on‐a‐chip devices. Inspired by natural motile bacteria such as E. Coli, artificial bacterial flagella (ABFs) are one kind of magnetic helical microswimmers. ABFs can perform 3D navigation in a controllable fashion with micrometer precision under low‐strength rotating magnetic fields (
      PubDate: 2015-01-22T13:39:44.734553-05:
      DOI: 10.1002/adfm.201403891
       
  • On‐Chip Self‐Assembly of a Smart Hybrid Nanocomposite for
           Antitumoral Applications
    • Authors: Bárbara Herranz‐Blanco; Dongfei Liu, Ermei Mäkilä, Mohammad‐Ali Shahbazi, Eloy Ginestar, Hongbo Zhang, Vladimir Aseyev, Vimalkumar Balasubramanian, Jarno Salonen, Jouni Hirvonen, Hélder A. Santos
      Pages: n/a - n/a
      Abstract: A hybrid nanocomposite comprised by porous silicon nanoparticles and a stimuli responsive polymeric material, polyethylene glycol‐block‐poly(L‐histidine), is spontaneously formed by nanoprecipitation in a flow‐focusing microfluidic chip. The nanocomposite presents a novel hybrid compound micelle structure with a great robustness for therapeutic applications. Therefore, the nanocomposite is developed and tested as a “smart” multistage drug delivery system (MDDS) in response to some of the current problems that cancer treatment presents. Based on the stimuli‐responsive behavior of the nanocomposite, a chemotherapeutic agent is successfully loaded into the nanosystem and released upon changes in the pH‐values. The nanocomposite demonstrates enhanced stability in plasma, narrow size distribution, improved surface smoothness, and high cytocompatibility. Furthermore, the nanocomposite presents reduced nanoparticle internalization by phagocytic macrophage cells and pH‐dependent cell growth inhibition capacity. Overall, the developed hybrid nanocomposite shows very promising features for its further development as a “smart” pH‐responsive MDDS. A multistage drug delivery nanocomposite, comprising porous silicon nanoparticles and micellar pH‐responsive polymers, is fabricated by microfluidic nanoprecipitation. The drug‐loaded multistage platform shows high cytocompatibility, pH‐dependent cell growth inhibition capacity, and reduced internalization by phagocytic macrophage cells. This nanocomposite is a good candidate for further development as a platform for cancer drug delivery.
      PubDate: 2015-01-22T13:39:38.387388-05:
      DOI: 10.1002/adfm.201404122
       
  • Stretchable Conductive Composites Based on Metal Wools for Use as
           Electrical Vias in Soft Devices
    • Authors: Joshua Lessing; Stephen A. Morin, Christoph Keplinger, Alok S. Tayi, George M. Whitesides
      Pages: n/a - n/a
      Abstract: Soft devices can be bent, stretched, and compressed reversibly, but conventional wires are rigid. This work describes stretchable composites that are easily fabricated with simple tools and commodity materials, and that can provide a strategy for electrical wiring that meets certain needs of soft devices. These composites are made by combining metal wool and elastomeric polymers. Embedding fine (average fiber width ≈25 μm) steel wool (or other metal wools) in a silicone polymer creates an electrically conductive path through the nonconductive elastomer. This composite is flexible, stretchable, compressible, inexpensive, and simple to incorporate into the bodies of soft devices. It is also electrically anisotropic, and shows maximum conductivity along the majority axis of the fibers, but maximum extension perpendicular to this axis. The utility of this composite for creating an electrically conductive path through an elastomer was demonstrated in several devices, including: a soft, solderless breadboard, a soft touch sensor, and a soft strain gauge. Soft devices can be bent, stretched, and compressed reversibly, but conventional wires are rigid. This work describes stretchable composites that are easily fabricated with simple tools and commodity materials, and that can provide a strategy for electrical wiring that meets certain needs of soft devices. The utility of this composite is demonstrated in several devices, including a soft, solderless breadboard.
      PubDate: 2015-01-21T11:13:31.328877-05:
      DOI: 10.1002/adfm.201403396
       
  • Regulated Breathing Effect of Silicon Negative Electrode for Dramatically
           Enhanced Performance of Li‐Ion Battery
    • Authors: Xingcheng Xiao; Weidong Zhou, Youngnam Kim, Ill Ryu, Meng Gu, Chongmin Wang, Gao Liu, Zhongyi Liu, Huajian Gao
      Pages: n/a - n/a
      Abstract: Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (≈3600 mAh g–1). However, the huge volume swelling and shrinking during cycling, which mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic efficiency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well‐developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response at electrode level. For the first time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle efficiency. In situ transmission electron microscopy and finite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion. Si–C yolk–shell is applied to regulate the breathing effect and one order of magnitude of reduction on thickness changes at the electrode level during cycling is achieved: the electrode thickness variation reduces down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials.
      PubDate: 2015-01-21T11:12:57.480903-05:
      DOI: 10.1002/adfm.201403629
       
  • Masthead: (Adv. Funct. Mater. 4/2015)
    • Pages: n/a - n/a
      PubDate: 2015-01-21T10:54:51.473762-05:
      DOI: 10.1002/adfm.201570027
       
  • Biospecific Self‐Assembly of a Nanoparticle Coating for Targeted and
           Stimuli‐Responsive Drug Delivery
    • Authors: Jinyang Li; Xue Qu, Gregory F. Payne, Cheng Zhang, Yuxin Zhang, Jianbo Li, Jie Ren, Hua Hong, Changsheng Liu
      Pages: n/a - n/a
      Abstract: Biology provides a range of materials, mechanisms, and insights to meet the diverse requirements of nanomedicine. Here, a biologically based nanoparticle coating system that offers three characteristic features is reported. First, the coating can be self‐assembled through a noncovalent biospecific interaction mechanism between a lectin protein (Concanavalin A) and the polysaccharide glycogen. This biospecific self‐assembly enables the coating to be applied simply without the generation of covalent bonds. Second, glycoprotein‐based biofunctionality can be incorporated into the coating through the same noncovalent biospecific interaction mechanism. Here, the glycoprotein transferrin is incorporated into the coating since this moiety is commonly used to target cancer cells through a receptor‐mediated endocytosis mechanism. Third, the coating can be triggered to disassemble in response to a reduction in pH that is characteristic of endosomal uptake. In a proof‐of‐concept study, comparing coated and uncoated nanoparticles, model drug‐loaded nanoparticles (doxorubicin‐loaded mesoporous silica nanoparticles) are prepared and it is observed that the coated nanoparticle has enhanced cytotoxicity for cancer cell lines but attenuated cytotoxicity for noncancerous cell lines. These studies demonstrate that biology provides unique materials and mechanism appropriate to meet the needs for emerging applications in the medical and life sciences. Biology routinely uses nanoparticles to target the delivery of molecular and macro­molecular cargo. Here, biological materials and mechanisms are listed for the fabrication of a nanoparticle coating that: i) self‐assembles through biospecific interactions (sugar–lectin binding), ii) confers targeting function (selective cellular uptake through receptor‐mediated endocytosis), and iii) is triggered to disassemble for cargo release in response to physiologically relevant stimuli (endosomal pH).
      PubDate: 2015-01-21T05:09:34.547446-05:
      DOI: 10.1002/adfm.201403636
       
  • Molecular Mechanism of Specific Recognition of Cubic Pt Nanocrystals by
           Peptides and of the Concentration‐Dependent Formation from Seed
           Crystals
    • Authors: Hadi Ramezani‐Dakhel; Lingyan Ruan, Yu Huang, Hendrik Heinz
      Pages: n/a - n/a
      Abstract: Metal nanocrystals enable new functionality in sensors, biomarkers, and catalysts while mechanisms of shape‐control in synthesis remain incompletely understood. This study explains mechanisms of biomolecule recognition and ligand‐directed growth of cubic platinum nanocrystals in atomic detail using molecular dynamics simulation (MD), synthesis, and characterization. Peptide T7 is shown to selectively recognize {100} bounded nanocubes through preferential adsorption near the edges as opposed to facet centers. Spatial preferences in peptide binding are related to differences in the binding of water molecules and conformational matching of polarizable atoms in the peptide to {100} epitaxial sites. Changes in peptide concentration also have profound impact on attraction versus repulsion on a given surface. As an example, the selective synthesis of cubes in the presence of peptide T7 demonstrates that only intermediate T7 concentration leads to high yield. High‐resolution transmission electron microscopy (HRTEM) shows concentration‐dependent changes in crystal shape, yield, and size. Large‐scale MD simulations explain associated differences in facet coverage and in adsorption energies of T7 peptides on cuboctahedral seed crystals, supporting a growth mechanism of adatom deposition. A similar analysis using a different peptide S7 is presented as well. Emerging computational opportunities to predict ligand binding to metal nanocrystals and rationalize growth preferences are summarized. The mechanism of selective peptide recognition of nanocrystals and peptide‐directed growth into specific shapes is explained using molecular dynamics simulations and experiments. The adsorption strength of the peptides depends on the spatial location on the surface and on the concentration, in addition to the sequence. Preferences in facet coverage and binding energies correlate with nanocrystal shape, size, and yield.
      PubDate: 2015-01-21T05:09:25.021671-05:
      DOI: 10.1002/adfm.201404136
       
  • Enhanced Specificity in Capturing and Restraining Circulating Tumor Cells
           with Dual Antibody–Dendrimer Conjugates
    • Authors: Jingjing Xie; Yusheng Lu, Haiyan Dong, Rongli Zhao, Hongning Chen, Weiyu Shen, Patrick J. Sinko, Yewei Zhu, Jichuang Wang, Jingwei Shao, Yu Gao, Fangwei Xie, Lee Jia
      Pages: n/a - n/a
      Abstract: Specifically capturing and restraining residual circulating tumor cells (CTCs) in cancer patients are the sine qua non for safely and effectively preventing cancer metastasis, to which the current chemotherapy has been limited due to its toxicity. Moreover, because of CTCs’ rarity and low activity, the current technology for capturing CTCs based solely on a single surface biomarker has limited capacity and is used mainly for in vitro diagnosis. Here, it is possible to sequentially conjugate two CTCs antibodies (aEpCAM and aSlex) to the functionalized dendrimers to specifically capture human hepatocellular CTCs in both artificial and clinical patient blood samples, and restrain their activities. The molecular entities of the conjugates are demonstrated by various means. The dual antibody conjugate captured CTCs threefold more than the single counterparts from the high concentrations of interfering red blood cells or leukocytes, as well as from the blood of liver cancer patients, and exhibits the superiority to their single counterparts in down‐regulating the captured CTCs. These results collectively provide the strong evidence that two antibodies can be compatibly conjugated to a nanomaterial, resulting in an enhanced specificity in restraining CTCs in blood. Synthesized dual antibody‐coated nanomaterial conjugates can specifically capture the rare circulating HepG2 tumor cells mixed with large population of red blood cells and HL‐60, resulting in down‐regulation of HepG2.
      PubDate: 2015-01-21T05:04:43.410473-05:
      DOI: 10.1002/adfm.201403556
       
  • In‐Plane Alignment in Organic Solar Cells to Probe the Morphological
           Dependence of Charge Recombination
    • Authors: Omar Awartani; Michael W. Kudenov, R. Joseph Kline, Brendan T. O'Connor
      Pages: n/a - n/a
      Abstract: Bulk heterojunction (BHJ) organic solar cells are fabricated with the polymer semiconductor aligned in the plane of the film to probe charge recombination losses associated with aggregates characterized by varying degrees of local order. 100% uniaxial strain is applied on ductile poly(3‐hexylthiophene):phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) BHJ films and characterize the resulting morphology with ultraviolet‐visible absorption spectroscopy and grazing incidence X‐ray diffraction. It is found that the strained films result in strong alignment of the highly ordered polymer aggregates. Polymer aggregates with lower order and amorphous regions also align but with a much broader orientation distribution. The solar cells are then tested under linearly polarized light where the light is selectively absorbed by the appropriately oriented polymer, while maintaining a common local environment for the sweep out of photogenerated charge carriers. Results show that charge collection losses associated with a disordered BHJ film are circumvented, and the internal quantum efficiency is independent of P3HT local aggregate order near the heterojunction interface. Uniquely, this experimental approach allows for selective excitation of distinct morphological features of a conjugated polymer within a single BHJ film, providing insight into the morphological origin of recombination losses. The internal quantum efficiency for light absorption in high‐order and low‐order P3HT aggregates is measured in a single photovoltaic cell, enabled by fabricating devices with polymer in‐plane alignment and selective polymer excitation using linearly polarized illumination. The internal quantum efficiency is independent of polarized illumination suggesting losses in disordered films are solely due to charge collection losses.
      PubDate: 2015-01-21T05:04:15.332972-05:
      DOI: 10.1002/adfm.201403377
       
  • Gold Nanoclusters‐Based Nanoprobes for Simultaneous Fluorescence
           Imaging and Targeted Photodynamic Therapy with Superior Penetration and
           Retention Behavior in Tumors
    • Authors: Chunlei Zhang; Chao Li, Yanlei Liu, Jingpu Zhang, Chenchen Bao, Shujing Liang, Qing Wang, Yao Yang, Hualin Fu, Kan Wang, Daxiang Cui
      Pages: n/a - n/a
      Abstract: Gold nanoclusters (GNCs) attract increasing attention due to their potential applications in sensing, catalysis, optoelectronics, and biomedicine. Herein, the formation of highly fluorescent glutathione (GSH)‐capped GNCs is achieved through the delicate control of the reduction kinetics and thermodynamic selection of the Au(I)–SG complexes. Furthermore, the GNCs‐based nanoprobes are developed by the covalent coupling folic acid (FA) and PEG (polyethylene glycol) on the surface of GNCs directly, followed by trapping photosensitizer (chlorin e6, Ce6) within PEG networks and attaching to the GNCs surface. The fabricated nanoprobes (Ce6@GNCs‐PEG2K‐FA) possess a uniform particle size (hydrodynamic diameter ≈6.1 ± 1.2 nm), without affecting the yield of singlet oxygen of the trapped Ce6. In vitro studies show the enhanced cellular uptake and satisfactory photodynamic therapy (PDT) effectiveness toward MGC‐803 cells when compared with free Ce6. The biodistribution and excretion pathway studies of the nanoprobes in MGC‐803 tumor‐bearing nude mice reveal their superior penetration and retention behavior in tumors, while the preserved features of renal clearance and stealthy to reticulo‐endothelial system are mainly attributed to the small hydrodynamic diameters and the FA‐capped PEGylated ligands. The enhanced PDT efficacy and the nontoxicity to mice provide an exciting new nano‐platform with promising clinical translational potential. A novel gold nanoclusters‐based Ce6 delivery nano‐platform is developed to achieve selective targeting toward cancer cells and tumors combining photodynamic therapy therapy. Systematic in vitro and in vivo experiments evaluate the cellular uptake, light‐induced cell apoptosis, biodistribution, as well as FA‐directed active tumor targeting and deep‐penetration‐enhanced photodynamic therapy of the gold nanoclusters‐based nanoprobes. The results identify the great potentials of gold nanoclusters for clinical use.
      PubDate: 2015-01-16T07:21:18.231039-05:
      DOI: 10.1002/adfm.201403095
       
  • DNA/Tannic Acid Hybrid Gel Exhibiting Biodegradability, Extensibility,
           Tissue Adhesiveness, and Hemostatic Ability
    • Authors: Mikyung Shin; Ji Hyun Ryu, Joseph P. Park, Keumyeon Kim, Jae Wook Yang, Haeshin Lee
      Pages: n/a - n/a
      Abstract: DNA has emerged as a novel material in many areas of materials science due to its programmability. Especially, DNA hydrogels have been studied to incorporate new functions into gels. To date, only a few methods have been developed for fabricating DNA hydrogels, such as the use of complementary sequences or covalent bond. Herein, it is demonstrated that one of the most well‐known plant‐derived polyphenols, tannic acid (TA), can form a DNA hydrogel which is named TNA hydrogel (TA + DNA). TA plays a role as a “molecular glue” by a new mode of action reversibly connecting between phosphodiester bonds, which is different from the crosslinking utilizing complementary sequences. TA intrinsically degrades due to ester bonds connecting between pyrogallol groups, causing a degradable DNA hydrogel. Furthermore, TNA gel is multifunctional in that the gel is extensible upon pulling and adhesive to tissues because of the rich polyphenol groups in TA (ten phenols per TA). Unexpectedly, TNA gel exhibits superior in vivo hemostatic ability that can be useful for biomedical applications. This new DNA hydrogel preparation method represents a new technique for fabricating a large amount of DNA‐based hemostatic hydrogel without chemically modifying DNA or requiring the crosslinking by complementary sequences. A new concept in DNA gel preparation using a plant‐inspired “molecular glue,” tannic acid (TA), is applied in this study. The gel, named TNA (TA + DNA) hydrogel, exhibits unique characteristics not observed in conventional DNA gels: extensibility, adhesiveness, degradability, and hemostatic ability. The crosslinking mechanism via hydrogen bonds enables the large‐scale preparation of TNA gel and the release of encapsulated DNA.
      PubDate: 2015-01-16T07:20:32.505611-05:
      DOI: 10.1002/adfm.201403992
       
  • Engineered Proteinticles for Targeted Delivery of siRNA to Cancer Cells
    • Authors: Eun Jung Lee; So Jin Lee, Yoon‐Sik Kang, Ju Hee Ryu, Koo Chul Kwon, Eunji Jo, Ji Young Yhee, Ick Chan Kwon, Kwangmeyung Kim, Jeewon Lee
      Pages: n/a - n/a
      Abstract: Considering the problems of small interfering RNA (siRNA) delivery using traditional viral and nonviral vehicles, a new siRNA delivery system to enhance efficiency and safety needs to be developed. Here human ferritin‐based proteinticles are genetically engineered to simultaneously display various functional peptides on the surface of proteinticles: cationic peptide to capture siRNA, tumor cell targeting and penetrating peptides, and enzymatically cleaved peptide to release siRNA inside tumor cell. In the in vitro treatment of poly‐siRNA‐proteinticle complex, both of the tumor cell targeting and penetrating peptides are important for efficient delivery of siRNA, and the red fluorescent protein (RFP) expression in RFP‐expressing tumor cells is notably suppressed by the delivered siRNA with the complementary sequence to RFP mRNA. It seems that the human ferritin‐based proteinticle is an efficient, stable, and safe tool for siRNA delivery, having a great potential for application to in vivo cancer treatment. The unique feature of proteinticles is that multiple and functional peptides can be simultaneously and evenly placed and also easily switched on the proteinticle surface through a simple genetic modification, which is likely to make proteinticles appropriate for targeted delivery of siRNA to a wide range of cancer cells. An efficient system for targeted siRNA delivery to cancer cells is successfully developed using genetically engineered human ferritin‐based proteinticles. The engineered proteinticles display various functional peptides [cationic peptide to capture siRNA, tumor cell targeting and penetrating peptides (CTP and CPP, respectively), and enzymatically cleaved peptide to release small interfering RNA inside tumor cell] on their surface and show no cytotoxicity.
      PubDate: 2015-01-16T02:41:48.47798-05:0
      DOI: 10.1002/adfm.201403680
       
  • Tunable Near UV Microcavity OLED Arrays: Characterization and Analytical
           Applications
    • Authors: Eeshita Manna; Fadzai Fungura, Rana Biswas, Joseph Shinar, Ruth Shinar
      Pages: n/a - n/a
      Abstract: A new approach is demonstrated to fabricate narrow‐band emission near‐UV microcavity OLEDs (μcOLEDs) with peak emission at ≈385 nm, in near‐perfect alignment with the narrow primary 385 nm absorption band of Pt octaethylporphyrin dye, using 4,4′‐bis(9‐carbazolyl)‐1,1′‐biphenyl (CBP) as the emissive layer. Although OLEDs have been extensively operated at optical wavelengths, only few have achieved near‐UV emission. Yet there is a growing need for portable compact narrow‐band near UV sources for many biomedical and forensic applications. A microcavity effect, due to metallic electrodes enclosing an optical cavity, is employed to achieve the desired narrow peak emission. An Al/Pd bi‐layer anode enables attaining a turn on voltage of 3.8 V and a 4,4′‐cyclohexylidenebis [N,N‐bis (4‐methylphenyl) benzenamine] (TAPC) layer improves electron‐hole recombination in the emissive layer. The fabricated μcOLED is efficiently used as the excitation source in a structurally integrated all‐organic oxygen sensor. Moreover, a CBP‐based combinatorial array of μcOLED pixels is fabricated by varying the thickness of the organic layers to obtain nine sharp, discrete emission peaks from 370 to 430 nm, employed in an all‐organic on‐chip spectrophotometer. The photodetectors are based on P3HT:PCBM (poly(3‐hexylthiophene):[6,6]‐phenyl‐C60‐butyric acid methyl ester) or the more sensitive PTB7:PCBM (PTB7 is polythieno [3,4‐b]‐thiophene‐co‐benzodithiophene). Simulations of the OLEDs' emission are used for analysis of the experimental data, assisting in device fabrication. Near‐UV microcavity CBP‐based OLEDs (peak emission ≈385 nm) with Al/Pd anode exhibit increased irradiance and lower turn‐on voltage in comparison to other CBP‐based OLEDs. The peak emission is well aligned with the narrow 385 nm absorption band of the ubiquitous PtOEP. A tunable microcavity OLED array (peak electroluminescence 370–430 nm) is utilized in an all‐organic (OLED/sensing film/OPD) on‐chip spectrophotometer.
      PubDate: 2015-01-16T02:41:38.218242-05:
      DOI: 10.1002/adfm.201403313
       
  • Does Excess Energy Assist Photogeneration in an Organic Low‐Bandgap
           Solar Cell?
    • Authors: Tobias Hahn; Johannes Geiger, Xavier Blase, Ivan Duchemin, Dorota Niedzialek, Steffen Tscheuschner, David Beljonne, Heinz Bässler, Anna Köhler
      Pages: n/a - n/a
      Abstract: The field dependence of the photocurrent in a bilayer assembly is measured with the aim to clarify the role of excess photon energy in an organic solar cell comprising a polymeric donor and an acceptor. Upon optical excitation of the donor an electron is transferred to the acceptor forming a Coulomb‐bound electron–hole pair. Since the subsequent escape is a field assisted process it follows that photogeneration saturates at higher electric fields, the saturation field being a measure of the separation of the electron–hole pair. Using the low bandgap polymers, PCDTBT and PCPDTBT, as donors and C60 as acceptor in a bilayer assembly it is found that the saturation field decreases when the photon energy is roughly 0.5 eV above the S1–S0 0–0 transition of the donor. This translates into an increase of the size of the electron‐hole‐pair up to about 13 nm which is close to the Coulomb capture radius. This increase correlates with the onset of higher electronic states that have a highly delocalized character, as confirmed by quantum‐chemical calculations. This demonstrates that accessing higher electronic states does favor photogeneration yet excess vibrational energy plays no role. Experiments on intrinsic photogeneration in donor photodiodes without acceptors support this reasoning. Exciton dissociation in bilayer solar cells is facilitated by exciting into higher‐lying, more delocalized excited states of the donor polymer. This is shown by measuring the field dependence of the photocurrent in PCDTBT/C60 cells and in PCPDTBT/C60 cells for different excitation energies and comparing this to the delocalization of the associated excited states as determined by quantum‐chemical calculations.
      PubDate: 2015-01-16T02:41:35.368787-05:
      DOI: 10.1002/adfm.201403784
       
  • Novel Biocompatible Polysaccharide‐Based Self‐Healing Hydrogel
    • Authors: Zhao Wei; Jian Hai Yang, Zhen Qi Liu, Feng Xu, Jin Xiong Zhou, Miklós Zrínyi, Yoshihito Osada, Yong Mei Chen
      Pages: n/a - n/a
      Abstract: A novel biocompatible polysaccharide‐based self‐healing hydrogel, CEC‐l‐OSA‐l‐ADH hydrogel (“l” means “linked‐by”), is developed by exploiting the dynamic reaction of N‐carboxyethyl chitosan (CEC) and adipic acid dihydrazide (ADH) with oxidized sodium alginate (OSA). The self‐healing ability, as demonstrated by rheological recovery, macroscopic observation, and beam‐shaped strain compression measurement, is attributed to the coexistence of dynamic imine and acylhydrazone bonds in the hydrogel networks. The CEC‐l‐OSA‐l‐ADH hydrogel shows excellent self‐healing ability under physiological conditions with a high healing efficiency (up to 95%) without need for any external stimuli. In addition, the CEC‐l‐OSA‐l‐ADH hydrogel exhibits good cytocompatibility and cell release as demonstrated by three‐dimensional cell encapsulation. With these superior properties, the developed hydrogel holds great potential for applications in various biomedical fields, e.g., as cell or drug delivery carriers. A novel biocompatible polysaccharide‐based self‐healing hydrogel containing dynamic imine and acylhydrazone bonds can be prepared by the dynamic reaction of N‐carboxyethyl chitosan, adipic acid dihydrazide with oxidized sodium alginate. The self‐healing efficiency can autonomously achieve 95% under physiological conditions, holding great potential for applications in biomedical field.
      PubDate: 2015-01-14T07:11:58.30886-05:0
      DOI: 10.1002/adfm.201401502
       
  • Superparamagnetic Liposomes for MRI Monitoring and External Magnetic
           Field‐Induced Selective Targeting of Malignant Brain Tumors
    • Authors: Hélène Marie; Laurent Lemaire, Florence Franconi, Sonia Lajnef, Yves‐Michel Frapart, Valérie Nicolas, Ghislaine Frébourg, Michael Trichet, Christine Ménager, Sylviane Lesieur
      Pages: n/a - n/a
      Abstract: Magnetic‐fluid‐loadedliposomes (MFLs) of optimized magnetic responsiveness are newly worked out from the entrapment of superparamagnetic maghemite nanocrystals in submicronic PEG‐ylated rhodamine‐labelled phospholipid vesicles. This nanoplatform provides an efficient tool for the selective magnetic targeting of malignant tumors localized in brain and non‐invasive traceability by MRI through intravascular administration. As assessed by in vivo 7‐T MRI and ex vivo electron spin resonance, 4‐h exposure to 190‐T m–1 magnetic field gradient efficiently concentrates MFLs into human U87 glioblastoma implanted in the striatum of mice. The magnetoliposomes are then longer retained therein as checked by MRI monitoring over a 24‐h period. Histological analysis by confocal fluorescence microscopy confirms the significantly boosted accumulation of MFLs in the malignant tissue up to the intracellular level. Electron transmission microscopy reveals effective internalization by endothelial and glioblastoma cells of the magnetically conveyed MFLs as preserved vesicle structures. The magnetic field gradient emphasizes MFL distribution solely in the tumors according to the enhanced permeability and retention (EPR) effect while comparatively very low amounts are recovered in the other cerebral areas. Such a selective targeting precisely traceable by MRI is promising for therapeutic applications since the healthy brain tissue can be expected to be spared during treatments by deleterious anticancer drugs carried by magnetically guided MFLs. Long‐circulating lipid vesicles entrapping highly concentrated superparamagnetic nanocrystals of maghemite (MFLs) provide a reliable MRI traceable tool for systemic targeting of intracerebral tumors. As experienced here on human glioblastomas implanted in the striatum of mice, the application of a magnetic field gradient significantly and selectively accumulates MFLs in the malignant neoplasms up to the intracellular level, while sparing healthy brain tissues.
      PubDate: 2015-01-14T07:11:53.758989-05:
      DOI: 10.1002/adfm.201402289
       
  • Hydrophilic Nanotube Supported Graphene–Water Dispersible Carbon
           Superstructure with Excellent Conductivity
    • Authors: Vasilios Georgakilas; Athanasios Demeslis, Evangelos Ntararas, Antonios Kouloumpis, Konstantinos Dimos, Dimitrios Gournis, Mikuláš Kocman, Michal Otyepka, Radek Zbořil
      Pages: n/a - n/a
      Abstract: In this work, it is shown that the hydrophilic functionalized multiwall carbon nanotubes (MWCNs) can stabilize a large amount of pristine graphene nanosheets in pure water without the assistance of surfactants, ionic liquids, or hydrophilic polymers. Role of stabilizer is conveyed by highly hydrophilic carbon nanotubes, functionalized by dihydroxy phenyl groups, affording a stable dispersion at concentrations as high as 15 mg mL−1. Such multidimensional (2D/1D) graphene/MWCN hybrid is found to be dispersible also in other polar organic solvents such as ethanol, isopropanol, N,N‐dimethylformamide, ethylene glycol, and their mixtures. High‐resolution transmission microscopy and atomic force microscopy (AFM) including a liquid mode AFM manifest several types of interaction including trapping of multiwalled carbon nanotubes between the graphene sheets or the modification of graphene edges. Molecular dynamic simulations show that formation of an assembly is kinetically controlled. Importantly, the hybrid can be deposited on the paper by drop casting or dispersed in water‐soluble polymers resulting in record values of electrical conductivity (sheet resistance up to Rs ≈ 25 Ω sq−1 for free hybrid material and Rs ≈ 1300 Ω sq−1 for a polyvinilalcohol/hybrid composite film). Thus, these novel water dispersible carbon superstructures reveal a high application potential as conductive inks for inkjet printing or as highly conductive polymers. In this work, hydrophilic functionalized carbon nanotubes can stabilize a large amount of pristine graphene nanosheets in pure water without surfactant assistance, affording a stable dispersion at concentrations as high as 15 mg mL−1. The graphene/carbon nanotube hybrid dispersion shows high electrical conductivity with potential application as a conductive ink for inkjet printing.
      PubDate: 2015-01-14T07:11:46.732808-05:
      DOI: 10.1002/adfm.201403801
       
  • High Performance 3D Si/Ge Nanorods Array Anode Buffered by TiN/Ti
           Interlayer for Sodium‐Ion Batteries
    • Authors: Chuang Yue; Yingjian Yu, Shibo Sun, Xu He, Binbin Chen, Wei Lin, Binbin Xu, Mingsen Zheng, Suntao Wu, Jing Li, Junyong Kang, Liwei Lin
      Pages: n/a - n/a
      Abstract: 3D micro/nanobatteries in high energy and power densities are drawing more and more interest due to the urgent demand of them in integrating with numerous micro/nanoscale electronic devices, such as smart dust, miniaturized sensors, actuators, BioMEMS chips, and so on. In this study, the electrochemical performances of 3D hexagonal match‐like Si/Ge nanorod (NR) arrays buffered by TiN/Ti interlayer, which are fabricated on Si substrates by a cost‐effective, wafer scale, and Si‐compatible process are demonstrated and systematically investigated as the anode in sodium‐ion batteries. The optimized Si/TiN/Ti/Ge composite NR array anode displays superior areal/specific capacities and cycling stability by reason of their favorable 3D nanostructures and the effective conductive layers of TiN/Ti thin films. Sodium‐ion insertion behaviors are experimentally investigated in postmorphologies and elemental information of the cycled composite anode, and theoretically studied by the first principles calculation upon the adsorption and diffusion energies of sodium in Ge unit cell. The preferential diffusion of sodium in Ge structure over in Si lattice is evidently proved. The successful configuration of these distinctive wafer‐scale Si‐based Na‐ion micro/nanobattery anodes can provide insight into exploring and designing new Si/Ge‐based electrode materials, which can be integrated into micro‐electronic devices as on chip power systems in the future. 3D hexagonal Si/TiN/Ti/Ge NR arrays as anodes in sodium‐ion batteries (SIBs) present high reversible areal/specific capacity and superior cycling stability even imposed by high current densities. This kind of unique wafer‐scale 3D Si‐based composite electrode portends a promising future for lab‐on‐chip micro/nanoSIBs with practical applications in integrated circuit systems, micro/nano­electro mechanical systems, or other smart electronic devices.
      PubDate: 2015-01-14T07:11:40.148546-05:
      DOI: 10.1002/adfm.201403648
       
  • Conductive “Smart” Hybrid Hydrogels with PNIPAM and
           Nanostructured Conductive Polymers
    • Authors: Ye Shi; Chongbo Ma, Lele Peng, Guihua Yu
      Pages: n/a - n/a
      Abstract: Stimuli‐responsive hydrogels with decent electrical properties are a promising class of polymeric materials for a range of technological applications, such as electrical, electrochemical, and biomedical devices. In this paper, thermally responsive and conductive hybrid hydrogels are synthesized by in situ formation of continuous network of conductive polymer hydrogels crosslinked by phytic acid in poly(N‐isopropylcrylamide) matrix. The interpenetrating binary network structure provides the hybrid hydrogels with continuous transporting path for electrons, highly porous microstructure, strong interactions between two hydrogel networks, thus endowing the hybrid hydrogels with a unique combination of high electrical conductivity (up to 0.8 S m−1), high thermoresponsive sensitivity (significant volume change within several seconds), and greatly enhanced mechanical properties. This work demonstrates that the architecture of the filling phase in the hydrogel matrix and design of hybrid hydrogel structure play an important role in determining the performance of the resulting hybrid material. The attractive performance of these hybrid hydrogels is further demonstrated by the developed switcher device which suggests potential applications in stimuli‐responsive electronic devices. Thermal‐responsive and conductive hybrid hydrogels are synthesized by the in situ formation of continuous network of conductive polymer hydrogels in poly(N‐isopropylcrylamide) matrix. The interpenetrating binary network structure provides the hybrid hydrogels with continuous electron transport path, highly porous microstructure, strong interactions between networks, thus endowing them with a unique combination of high electrical conductivity, high thermal‐responsive sensitivity, and good mechanical properties.
      PubDate: 2015-01-14T07:11:16.500508-05:
      DOI: 10.1002/adfm.201404247
       
  • Quinoidal Molecules as a New Class of Ambipolar Semiconductor Originating
           from Amphoteric Redox Behavior
    • Authors: Hansu Hwang; Dongyoon Khim, Jin‐Mun Yun, Eunhwan Jung, Soo‐Young Jang, Yun Hee Jang, Yong‐Young Noh, Dong‐Yu Kim
      Pages: n/a - n/a
      Abstract: The two small molecules, quinoidal bithiophene (QBT) and quinoidal biselenophene (QBS), are designed based on a quinoid structure, and synthesized via a facile synthetic route. These quinoidal molecules have a reduced band gap and an amphoteric redox behavior, which is caused by an extended delocalization. Due to such properties, organic field‐effect transistors based on QBT and QBS have shown balanced ambipolar characteristics. After thermal annealing, the performances of the devices are enhanced by an increase in crystallinity. The field‐effect hole and electron mobilities are measured to be 0.031 cm2 V−1 s−1 and 0.005 cm2 V−1 s−1 for QBT, and 0.055 cm2 V−1 s−1 and 0.021 cm2 V−1 s−1 for QBS, respectively. In addition, we investigate the effect of chalcogen atoms (S and Se) on the molecular properties. The optical, electrochemical properties and electronic structures are mainly dominated by the quinoidal structure, whereas molecular properties are scarcely affected by either type of chalcogen atom. The main effect of the chalcogen atoms is ascribed to the difference of crystallinity. Due to a strong intermolecular interaction of the selenophene, QBS exhibits a higher degree of crystallinity, which leads to an enhancement of both hole and electron mobilities. Consequently, these types of quinoidal molecules are found to be promising for use as ambipolar semiconductors. Quinoidal organic semiconductors containing dichalcogenophene (quinoidal bithiophene and quinoidal biselenophene) are designed and synthesized by facile synthetic route. Due to the extended delocalization of quinoid structure, they show low band gap and amphoteric redox behavior. Compared with common aromatic compounds, such unusual properties of quinoid structure give rise to balanced ambipolar charge transport in the top gate field‐effect transistor devices.
      PubDate: 2015-01-13T10:07:11.773986-05:
      DOI: 10.1002/adfm.201402758
       
  • A Tumor Targeted Chimeric Peptide for Synergistic Endosomal Escape and
           Therapy by Dual‐Stage Light Manipulation
    • Authors: Kai Han; Qi Lei, Hui‐Zhen Jia, Shi‐Bo Wang, Wei‐Na Yin, Wei‐Hai Chen, Si‐Xue Cheng, Xian‐Zheng Zhang
      Pages: n/a - n/a
      Abstract: In this study, a pH sensitive chimeric peptide is developed to codeliver a photosensitizer, protoporphyrin IX (PpIX), and plasmid DNA simultaneously. In the presence of matrix metalloproteinase‐2 (MMP‐2), the chimeric peptide undergoes the process of hydrolysis of PLGVR peptide sequence, exfoliation of PEG, and increase of positive charges. As a result, the chimeric peptide can be preferentially uptaken by MMP‐2 rich tumor cells. To realize synergistic effect of drug and gene delivery, a dual‐stage light irradiation strategy is developed, i.e., the short time light irradiation can efficiently enhance the endosomal escape of the chimeric peptide/PpIX/DNA complexes by the formation the reactive oxygen species (ROS), resulting in synergistic endosomal escape and improved DNA expression. In addition, due to the screened phototoxicity of PpIX, short time light irradiation does not lead to detectable changes in the cell viability. After the gene transfection, the screened phototoxicity of PpIX is subsequently stimulated by long time irradiation to achieve high synergistic efficacy of photodynamic and gene therapies. Both in vitro and in vivo studies confirm the chimeric peptide‐based nanocarrier with a good synergistic effect is a promising nanoplatform for tumor treatments. A MMP‐2 responsiveness chimeric peptide is reported to transport the photosensitizer PpIX and DNA to the target cells. Importantly, a dual‐stage light irradiation strategy is used to enhance the endosome escape via photochemical internalization. A high therapeutic index is achieved due to the synergistic effect between gene therapy and photodynamic therapy.
      PubDate: 2015-01-13T10:06:15.682941-05:
      DOI: 10.1002/adfm.201403190
       
  • Injectable Hydrogels with In Situ Double Network Formation Enhance
           Retention of Transplanted Stem Cells
    • Authors: Lei Cai; Ruby E. Dewi, Sarah C. Heilshorn
      Pages: n/a - n/a
      Abstract: Stem cell transplantation via direct injection is a minimally invasive strategy being explored for treatment of a variety of injuries and diseases. Injectable hydrogels with shear moduli
      PubDate: 2015-01-13T10:05:52.818279-05:
      DOI: 10.1002/adfm.201403631
       
  • Preparation of Mesoporous Sb‐, F‐, and In‐Doped SnO2
           Bulk Powder with High Surface Area for Use as Catalyst Supports in
           Electrolytic Cells
    • Authors: Hyung‐Suk Oh; Hong Nhan Nong, Peter Strasser
      Pages: n/a - n/a
      Abstract: The M‐doped tin oxides (M = Sb, F, and In) to be used as catalyst support are synthesized by using templating process with tetradecylamine (TDA) as the template, combined with a hydrothermal (HT) method to improve its thermal stability. The obtained materials are characterized by XRD, SAXS, TEM, EDX, SEM, and BET to study microstructure and physical properties, which have a mesoporous structure, small particle size, and high surface area (125–263 m2 g–1). The materials show an overall conductivity of 0.102–0.295 S cm–1. Repetitive potential cycling is employed to characterize the electrochemical properties and stability. The M‐doped tin oxides are highly electrochemical stable compared to carbon black. From the observed results, it can be concluded that the combination of TDA and HT treatment are an effective synthetic method for designing mesoporous M‐doped tin oxide as catalyst supports. The M‐doped tin oxides (M = Sb, F, and In) for use as catalyst supports in electrolytic cells are synthesized, showing high surface area, mesoporous structure, good electrical conductivity, and high corrosion resistance. Therefore, this synthesis method is a very effective way to prepare the metal oxide as electrocatalyst supports.
      PubDate: 2015-01-12T11:29:43.595505-05:
      DOI: 10.1002/adfm.201401919
       
  • Ultra‐High Capacity Lithium‐Ion Batteries with Hierarchical
           CoO Nanowire Clusters as Binder Free Electrodes
    • Authors: Kangzhe Cao; Lifang Jiao, Yongchang Liu, Huiqiao Liu, Yijing Wang, Huatang Yuan
      Pages: n/a - n/a
      Abstract: Although transition metal oxide electrodes have large lithium storage capacity, they often suffer from low rate capability, poor cycling stability, and unclear additional capacity. In this paper, CoO nanowire clusters (NWCs) composed of ultra‐small nanoparticles (≈10 nm) directly grown on copper current collector are fabricated and evaluated as an anode of binder‐free lithium‐ion batteries, which exhibits an ultra‐high capacity and good rate capability. At a rate of 1 C (716 mA g−1), a reversible capacity as high as 1516.2 mA h g−1 is obtained, and even when the current density is increased to 5 C, a capacity of 1330.5 mA h g−1 could still be maintained. Importantly, the origins of the additional capacity are investigated in detail, with the results suggesting that pseudocapacitive charge and the higher‐oxidation‐state products are jointly responsible for the large additional capacity. In addition, nanoreactors for the CoO nanowires are fabricated by coating the CoO nanowires with amorphous silica shells. This hierarchical core–shell CoO@SiO2 NWC electrode achieves an improved cycling stability without degrading the high capacity and good rate capability compared to the uncoated CoO NWCs electrode. Hierarchical CoO nanowire clusters comprising ultra‐small nanoparticles (≈10 nm) on copper foil are successfully fabricated. When used as an anode material for lithium‐ion batteries, this binder‐free electrode exhibits an ultra‐high capacity and excellent rate capability. What is more, the origins of the additional capacity are investigated in detail. Hierarchical core–shell CoO@SiO2 nanowire clusters are also fabricated, to improve cycle stability.
      PubDate: 2015-01-12T11:29:22.150719-05:
      DOI: 10.1002/adfm.201403111
       
  • Biodegradable Thin Metal Foils and Spin‐On Glass Materials for
           Transient Electronics
    • Authors: Seung‐Kyun Kang; Suk‐Won Hwang, Sooyoun Yu, Jung‐Hun Seo, Elise A. Corbin, Jiho Shin, Dae Seung Wie, Rashid Bashir, Zhenqiang Ma, John A. Rogers
      Pages: n/a - n/a
      Abstract: Biodegradable substrates and encapsulating materials play critical roles in the development of an emerging class of semiconductor technology, generally referred as “transient electronics”, whose key characteristic is an ability to dissolve completely, in a controlled manner, upon immersion in ground water or biofluids. The results presented here introduce the use of thin foils of Mo, Fe, W, or Zn as biodegradable substrates and silicate spin‐on‐glass (SOG) materials as insulating and encapsulating layers, with demonstrations of transient active (diode and transistor) and passive (capacitor and inductor) electronic components. Complete measurements of electrical characteristics demonstrate that the device performance can reach levels comparable to those possible with conventional, nontransient materials. Dissolution kinetics of the foils and cytotoxicity tests of the SOG yield information relevant to use in transient electronics for temporary biomedical implants, resorbable environmental monitors, and reduced waste consumer electronics. Materials, fabrication strategies, dissolution kinetics, and biocompatibility studies of transient electronics systems built on thin metal foils passivated by layers of spin‐on glass (SOG) are presented. Transient electronic components exhibit comparable performances to conventional, nontransient substrates. Dissolution kinetics of the materials cured at different temperatures reveal key aspects of their corrosion chemistry, and in vitro cell cultures demonstrate their biocompatibility.
      PubDate: 2015-01-12T06:44:01.307523-05:
      DOI: 10.1002/adfm.201403469
       
  • Ternary Hybrids of Amorphous Nickel Hydroxide–Carbon
           Nanotube‐Conducting Polymer for Supercapacitors with High Energy
           Density, Excellent Rate Capability, and Long Cycle Life
    • Authors: Wenchao Jiang; Dingshan Yu, Qiang Zhang, Kunli Goh, Li Wei, Yili Yong, Rongrong Jiang, Jun Wei, Yuan Chen
      Pages: n/a - n/a
      Abstract: The utilization of Ni(OH)2 as a pseudocapacitive material for high performance supercapacitors is hindered by its low electrical conductivity and short cycle life. A coaxial ternary hybrid material comprising of amorphous Ni(OH)2 deposited on multiwalled carbon nanotubes wrapped with conductive polymer (poly (3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)) is demonstrated. A thin layer of disordered amorphous Ni(OH)2 is deposited by an effective “coordinating etching and precipitating” method, resulting in an ultrahigh specific capacitance of 3262 F g−1 at 5 mV s−1 and excellent rate capability (71.9% capacitance retention at 100 mV s−1). More importantly, the polymer layer prevents the degradation of the nanostructure and dis­solution of Ni ion during repeated charge–discharge cycling for 30 000 cycles, a phenomenon which often plagues Ni(OH)2 nanomaterials. Using the ternary Ni(OH)2 hybrid and the reduced graphene oxide/carbon nanotube hybrid as the positive and negative electrodes, respectively, the assembled asymmetric supercapacitors exhibit high energy density of 58.5 W h kg−1 at the power density of 780 W kg−1 as well as long cycle life (86% capacitance retention after 30 000 cycles). The ternary hybrid architecture design for amorphous Ni(OH)2 can be regarded as a general approach to obtain pseudocapacitive materials for supercapacitors with both high energy density, excellent rate capability, and long cycle life. Ternary hybrid: A ternary hybrid material comprising of amorphous Ni(OH)2 deposited on multiwalled carbon nanotubes wrapped with conductive polymer exhibits an ultrahigh gravimetric specific capacitance of 3262 F g−1. The assembled asymmetric supercapacitors exhibit a high specific energy density of 58.5 W h kg−1 as well as excellent long cycle life (86% capacitance retention after 30 000 cycles).
      PubDate: 2015-01-12T06:15:54.852429-05:
      DOI: 10.1002/adfm.201403354
       
  • One‐Pot, Facile, and Versatile Synthesis of Monolayer MoS2/WS2
           Quantum Dots as Bioimaging Probes and Efficient Electrocatalysts for
           Hydrogen Evolution Reaction
    • Authors: Shengjie Xu; Dian Li, Peiyi Wu
      Pages: n/a - n/a
      Abstract: In this work, uniform molybdenum disulfide (MoS2)/tungsten disulfide (WS2) quantum dots are synthesized by the combination of sonication and solvothermal treatment of bulk MoS2/WS2 at a mild temperature. The resulting products possess monolayer thickness with an average size about 3 nm. The highly exfoliated and defect‐rich structure renders these quantum dots plentiful active sites for the catalysis of hydrogen evolution reaction (HER). The MoS2 quantum dots exhibit a small HER overpotential of ≈120 mV and long‐term durability. Moreover, the strong fluorescence, good cell permeability, and low cytotoxicity make them promising and biocompatible probes for in vitro imaging. In addition, this work may provide an alternative facile approach to synthesize the quantum dots of transition metal dichalcogenides or other layered materials on a large scale. A facile, low cost, and versatile way to prepare monolayer MoS2/WS2 quantum dots on a large scale with fluorescent properties is proposed via the combination of sonication and solvothermal treatment of MoS2/WS2 powder. The prepared MoS2/WS2 quantum dots exhibit low cytotoxicity and good cell permeability in living cells as well as excellent electrocatalytic activity toward hydrogen evolution reaction.
      PubDate: 2015-01-08T08:06:27.74731-05:0
      DOI: 10.1002/adfm.201403863
       
  • Edge‐Fluorinated Graphene Nanoplatelets as High Performance
           
    • Authors: In‐Yup Jeon; Myung Jong Ju, Jiantie Xu, Hyun‐Jung Choi, Jeong‐Min Seo, Min‐Jung Kim, In Taek Choi, Hong Mo Kim, Jae Cheon Kim, Jae‐Joon Lee, Hua Kun Liu, Hwan Kyu Kim, Shixue Dou, Liming Dai, Jong‐Beom Baek
      Pages: n/a - n/a
      Abstract: Edge‐selectively fluorinated graphene nanoplatelets (FGnPs) are prepared by mechanochemically driven reaction between fluorine gas (20 vol% in argon) and activated carbon species from graphitic C–C bonds unzipped by high‐speed stainless steel balls with a high kinetic energy. The fluorination at edges of the unzipped graphene nanoplatelets (GnPs) is confirmed by various analytical techniques while the content of fluorine in FGnPs is determined to be 3.0 and 3.4 at% by X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectroscopy, respectively. Because of the large difference in electronegativity between carbon (χ = 2.55) and fluorine (χ = 3.98) and the strong C–F bond, the edge‐fluorination of GnPs can provide the maximized charge polarization with an enhanced chemical stability. Thus, electrodes based on the resultant FGnPs demonstrate superb electrochemical performance with excellent stability/cycle life in dye‐sensitized solar cells (FF: 71.5%; Jsc: 14.44 mA cm−2; Voc: 970 mV; PCE: 10.01%) and lithium ion batteries (650.3 mA h g−1 at 0.5 C, charge retention of 76.6% after 500 cycles). Edge‐selectively fluorinated graphene nanoplatelets (FGnPs) are prepared by simple mechanochemical ball‐milling graphite in the presence of fluorine/argon (20/80, v/v). The FGnPs demonstrate superb electrochemical performance with excellent stability/cycle life in dye‐sensitized solar cells and lithium ion batteries.
      PubDate: 2015-01-08T08:06:19.666579-05:
      DOI: 10.1002/adfm.201403836
       
  • State‐of‐the‐Art Progress in Diverse Heterostructured
           Photocatalysts toward Promoting Photocatalytic Performance
    • Authors: Haijin Li; Yong Zhou, Wenguang Tu, Jinhua Ye, Zhigang Zou
      Pages: n/a - n/a
      Abstract: Semiconductor photocatalysts have received much attention in recent years due to their great potentials for the development of renewable energy technologies, as well as for environmental protection and remediation. The effective harvesting of solar energy and suppression of charge carrier recombination are two key aspects in photocatalysis. The formation of heterostructured photocatalysts is a promising strategy to improve photocatalytic activity, which is superior to that of their single component photocatalysts. This Feature Article concisely summarizes and highlights the state‐of‐the‐art progress of semiconductor/semiconductor heterostructured photocatalysts with diverse models, including type‐I and type‐II heterojunctions, Z‐scheme system, p–n heterojunctions, and homojunction band alignments, which were explored for effective improvement of photocatalytic activity through increase of the visible‐light absorption, promotion of separation, and transportation of the photoinduced charge carries, and enhancement of the photocatalytic stability. This Feature Article concisely summarizes and highlights the state‐of‐the‐art progress of semiconductor/semiconductor heterostructured photocatalysts with diverse models, including type‐I and type‐II heterojunctions, Z‐scheme system, p–n heterojunctions, and homojunction band alignments, which were explored for effective improvement of photocatalytic activity through increase of the visible‐light absorption, promotion of separation and transportation of the photoinduced charge carries, and enhancement of the photocatalytic stability.
      PubDate: 2015-01-07T02:58:24.643545-05:
      DOI: 10.1002/adfm.201401636
       
  • HPbI3: A New Precursor Compound for Highly Efficient
           Solution‐Processed Perovskite Solar Cells
    • Authors: Feng Wang; Hui Yu, Haihua Xu, Ni Zhao
      Pages: n/a - n/a
      Abstract: Recently, there have been extensive research efforts on developing high performance organolead halide based perovskite solar cells. While most studies focused on optimizing the deposition processes of the perovskite films, the selection of the precursors has been rather limited to the lead halide/methylammonium (or formamidium) halide combination. In this work, we developed a new precursor, HPbI3, to replace lead halide. The new precursor enables formation of highly uniform formamidium lead iodide (FAPbI3) films through a one‐step spin‐coating process. Furthermore, the FAPbI3 perovskite films exhibit a highly crystalline phase with strong (110) preferred orientation and excellent thermal stability. The planar heterojunction solar cells based on these perovskite films exhibit an average efficiency of 15.4% and champion efficiency of 17.5% under AM 1.5 G illumination. By comparing the morphology and formation process of the perovskite films fabricated from the formamidium iodide (FAI)/HPbI3, FAI/PbI2, and FAI/PbI2 with HI additive precursor combinations, it is shown that the superior property of the HPbI3 based perovskite films may originate from 1) a slow crystallization process involving exchange of H+ and FA+ ions in the PbI6 octahedral framework and 2) elimination of water in the precursor solution state. HPbI3is introduced as a novel precursor to solve the non‐uniformity problem of formamidium lead iodide (FAPbI3) perovskite films from one‐step solution‐­processed method. Interestingly, the FAPbI3 films exhibit high crystallinity with (110) plane orientation and the corresponding devices yield an average photo­voltaic efficiency of 15.4% under 1 sun illumination. Present results demonstrate that precursor engineering is an effective approach to produce perovskites with attractive properties.
      PubDate: 2015-01-07T02:57:42.686368-05:
      DOI: 10.1002/adfm.201404007
       
  • Impact of Blend Morphology on Interface State Recombination in Bulk
           Heterojunction Organic Solar Cells
    • Authors: Benjamin Bouthinon; Raphaël Clerc, Jérôme Vaillant, Jean‐Marie Verilhac, Jérôme Faure‐Vincent, David Djurado, Irina Ionica, Gabriel Man, Antoine Gras, Georges Pananakakis, Romain Gwoziecki, Antoine Kahn
      Pages: n/a - n/a
      Abstract: This work is a reinvestigation of the impact of blend morphology and thermal annealing on the electrical performance of regioregular‐P3HT:PC60BM bulk heterojunction organic solar cells. The morphological, structural, and electrical properties of the blend are experimentally investigated with atomic force microscopy, X‐ray diffraction, and time‐of‐flight measurements. Current–voltage characteristics of photodiode devices are measured in the dark and under illumination. Finally, the existence of exponential electronic band tails due to gap states is experimentally confirmed by measuring the device spectral response in the subband gap regime. This method reveals the existence of a large density of gap states, which is partially and systematically reduced by thermal annealing. When the band tails are properly accounted for in the drift and diffusion simulations, experimentally measured charge transport characteristics, under both dark and illuminated conditions and as a function of annealing time, can be satisfactorily reproduced. This work further confirms the critical impact of tails states on the performance of solar cells. The predominance of the band tail states reorganization, characterized by spectral response measurement, in the improvement of the solar cell performances during the annealing step of the active layer is discussed. This energetic reorganization leads to a lowering of the recombinations assisted by trap state (efficiency improvement) and a decrease of the thermal generation from trap states (reverse dark current).
      PubDate: 2015-01-05T05:51:16.558315-05:
      DOI: 10.1002/adfm.201401633
       
  • Dual‐Mechanism Antimicrobial Polymer–ZnO Nanoparticle and
           Crystal Violet‐Encapsulated Silicone
    • Authors: Sacha Noimark; Jonathan Weiner, Nuruzzaman Noor, Elaine Allan, Charlotte K. Williams, Milo S. P. Shaffer, Ivan P. Parkin
      Pages: n/a - n/a
      Abstract: The prevalence of healthcare‐associated infection caused by multidrug‐resistant bacteria is of critical concern worldwide. It is reported on the development of a bactericidal surface prepared by use of a simple, upscalable, two‐step dipping strategy to incorporate crystal violet and di(octyl)­phosphinic‐ acid‐capped zinc oxide nanoparticles into medical grade silicone, as a strategy to reduce the risk of infection. The material is characterized by UV–vis absorbance spectroscopy, X‐ray photoelectron spectroscopy (XPS), inductively coupled plasma‐optical emission spectroscopy (ICP‐OES) and transmission electron microscopy (TEM) and confirmed the incorporation of the ZnO nanoparticles in the polymer. The novel system proves to be a highly versatile bactericidal material when tested against both Staphylococcus aureus and Escherichia coli, key causative micro‐organisms for hospital‐acquired infection (HAI). Potent antimicrobial activity is noted under dark conditions, with a significant enhancement exhibits when the surfaces are illuminated with a standard hospital light source. This polymer has the potential to decrease the risk of HAI, by killing bacteria in contact with the surface. Using a simple dipping strategy to incorporate zinc oxide nanoparticles and crystal violet dye in a silicone polymer, a versatile and potent antimicrobial surface is reported to demonstrate high kills under both dark and light conditions, against both Gram‐positive and Gram‐negative bacteria.
      PubDate: 2015-01-05T05:51:10.531352-05:
      DOI: 10.1002/adfm.201402980
       
  • Synthetic Asymmetric‐Shaped Nanodevices with Symmetric
           pH‐Gating Characteristics
    • Authors: Huacheng Zhang; Xu Hou, Jue Hou, Lu Zeng, Ye Tian, Lin Li, Lei Jiang
      Pages: n/a - n/a
      Abstract: Synthetic stimuli‐gated nanodevices displaying intelligent ion transport properties similar to those observed in biological ion channels have attracted increasing interests for their wide potential applications in biosensors, nanofluidics, and energy conversions. Here, bioinspired asymmetric shaped nanodevices are reported that can exhibit symmetric and linear pH‐gating ion transport features based on polyelectrolyte‐asymmetric‐functionalized asymmetric hourglass‐shaped nanochannels. The pH‐responsive polymer brushes grafted on the inner channel surface are acted as a gate that open and close in response to external pH changing to linearly and symmetrically regulate transmembrane ionic currents of the channel. A complete experimental characterization of the pH‐dependent ion transport behaviors of the nanodevice and a comprehensive discussion of the experimental results in terms of theoretical simulation are also presented. Both experimental and theoretical data shown in this work demonstrate the feasibility of using the asymmetric chemical modification method to achieve symmetric pH gating behaviors inside the asymmetric nanochannels, and lay the foundation to build diverse stimuli‐gated artificial asymmetric shaped ion channels with symmetric gating ion transport features. Inspired by asymmetric ion channels with symmetric pH gating features, a bio­inspired asymmetric shaped nanodevice is reported that shows symmetric pH‐gating ion transport features based on an asymmetric‐polyelectrolyte‐functionalized asymmetric hourglass nanochannel. This work, as an example, demonstrates the feasibility of using the asymmetric chemical modification method to achieve symmetric pH gating behaviors inside the asymmetric nanochannels.
      PubDate: 2015-01-05T05:50:50.326836-05:
      DOI: 10.1002/adfm.201403693
       
  • Ultrahigh Tunability of Room Temperature Electronic Transport and
           Ferromagnetism in Dilute Magnetic Semiconductor and PMN‐PT
           Single‐Crystal‐Based Field Effect Transistors via Electric
           Charge Mediation
    • Authors: Qiu‐Xiang Zhu; Ming‐Min Yang, Ming Zheng, Ren‐Kui Zheng, Li‐Jie Guo, Yu Wang, Jin‐Xing Zhang, Xiao‐Min Li, Hao‐Su Luo, Xiao‐Guang Li
      Pages: n/a - n/a
      Abstract: Multiferroic heterostructures composed of complex oxide thin films and ferroelectric single crystals have aroused considerable interest due to the electrically switchable strain and charge elements of oxide films by the polarization reversal of ferroelectrics. Previous studies have demonstrated that the electric‐field‐control of physical properties of such heterostructures is exclusively due to the ferroelectric domain switching‐induced lattice strain effects. Here, the first successful integration of the hexagonal ZnO:Mn dilute magnetic semiconductor thin films with high performance (111)‐oriented perovskite Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) single crystals is reported, and unprecedented charge‐mediated electric‐field control of both electronic transport and ferromagnetism at room temperature for PMN‐PT single crystal‐based oxide heterostructures is realized. A significant carrier concentration‐tunability of resistance and magnetization by ≈400% and ≈257% is achieved at room temperature. The electric‐field controlled bistable resistance and ferromagnetism switching at room temperature via interfacial electric charge presents a potential strategy for designing prototype devices for information storage. The results also disclose that the relative importance of the strain effect and interfacial charge effect in oxide film/ferroelectric crystal heterostructures can be tuned by appropriately adjusting the charge carrier density of oxide films. High‐quality ZnO:Mn semiconductor thin films are successfully integrated with high‐performance (111)‐oriented perovskite Pb(Mg1/3Nb2/3)O3‐PbTiO3 single crystals. Unprecedented room temperature charge‐mediated electric‐field‐control of electronic transport and magnetism is demonstrated for Pb(Mg1/3Nb2/3)O3‐PbTiO3 single‐crystal‐based oxide heterostructures in which the relative importance of the strain effect and the interfacial charge effect can be tuned by appropriately adjusting the charge carrier density of the films.
      PubDate: 2015-01-05T05:49:23.703793-05:
      DOI: 10.1002/adfm.201403763
       
  • Modeling of Organic Light Emitting Diodes: From Molecular to Device
           Properties
    • Authors: Pascal Kordt; Jeroen J. M. van der Holst, Mustapha Al Helwi, Wolfgang Kowalsky, Falk May, Alexander Badinski, Christian Lennartz, Denis Andrienko
      Pages: n/a - n/a
      Abstract: The progress in modeling of charge transport in disordered organic semiconductors on various length scales, from atomistic to macroscopic, is reviewed. This includes evaluation of charge transfer rates from first principles, parametrization of coarse‐grained lattice and off‐lattice models, and solving the master and drift‐diffusion equations. Special attention is paid to linking the length scales and improving the efficiency of the methods. All techniques are illustrated on an amorphous organic semiconductor, DPBIC, a hole conductor and electron blocker used in state of the art organic light emitting diodes (OLEDs). The outlined multiscale scheme can be used to predict OLED properties without fitting parameters, starting from chemical structures of compounds. Multiscale ansatz for modeling of organic light emitting diodes: single‐molecule‐based first principle calculations, parameterization of microscopic and coarse‐grained models, simulation of IV characteristics. OLED properties can be predicted without fitting parameters, starting from chemical structures of compounds.
      PubDate: 2015-01-03T15:06:35.415135-05:
      DOI: 10.1002/adfm.201403004
       
  • Coatings: Dynamic Fluoroalkyl Polyethylene Glycol Co‐Polymers: A New
           Strategy for Reducing Protein Adhesion in Lab‐on‐a‐Chip
           Devices (Adv. Funct. Mater. 4/2015)
    • Authors: Mahesh K. Sarvothaman; Kris S. Kim, Brendon Seale, Peter M. Brodersen, Gilbert C. Walker, Aaron R. Wheeler
      Pages: 497 - 497
      Abstract: An antifouling coating that improves digital microfluidic device lifetime up to 5.5‐fold relative to the state of the art is described by A. R. Wheeler and team on page 506. The material is dynamic: under standard conditions, the surface is flat and fluorinated; upon applying an electrical potential, the surface becomes activated, forming nanometer‐sized fluoropegylated structures that resist protein adhesion. (Image credit: Bill Dai.)
      PubDate: 2015-01-21T10:54:51.414894-05:
      DOI: 10.1002/adfm.201570024
       
  • Porous Materials: Submicrometer‐Sized ZIF‐71 Filled
           Organophilic Membranes for Improved Bioethanol Recovery: Mechanistic
           Insights by Monte Carlo Simulation and FTIR Spectroscopy (Adv. Funct.
           Mater. 4/2015)
    • Authors: Lik H. Wee; Yanbo Li, Kang Zhang, Patrizia Davit, Silvia Bordiga, Jianwen Jiang, Ivo F. J. Vankelecom, Johan A. Martens
      Pages: 498 - 498
      Abstract: Uniform submicrometer‐sized ZIF‐71 crystals are prepared via a simple mixed‐solvent method for the fabrication of high quality defect‐free PDMS mixed‐matrix membranes. As reported by L. H. Wee, I. F. J. Vankelecom, and colleagues on page 516, these membranes demonstrate significant improvement for pervaporation recovery of bioethanol. The host–guest chemistry of ethanol‐water in the cages of ZIF‐71 is unraveled by the combination of FTIR spectroscopy and molecular simulations.
      PubDate: 2015-01-21T10:54:50.663576-05:
      DOI: 10.1002/adfm.201570025
       
  • Contents: (Adv. Funct. Mater. 4/2015)
    • Pages: 499 - 504
      PubDate: 2015-01-21T10:54:52.061159-05:
      DOI: 10.1002/adfm.201570026
       
  • Supercapacitors: An Interface‐Induced Co‐Assembly Approach
           Towards Ordered Mesoporous Carbon/Graphene Aerogel for
           High‐Performance Supercapacitors (Adv. Funct. Mater. 4/2015)
    • Authors: Ruili Liu; Li Wan, Shaoqing Liu, Lixia Pan, Dongqing Wu, Dongyuan Zhao
      Pages: 651 - 651
      Abstract: On page 526, R. L. Liu, D. Q. Wu, and co‐workers develop an interface‐induced co‐assembly approach to fabricate hierarchically porous composites with ordered mesoporous carbon wrapping around macroporous graphene aerogels. The orientation of the mesopores in the resulting composites can be tuned by the adding amount of the starting materials. Combining the advantages of both components, the hierarchically porous composites exhibit excellent performance as the electrodes in supercapacitors.
      PubDate: 2015-01-21T10:54:52.913305-05:
      DOI: 10.1002/adfm.201570028
       
  • Energy Storage: Sodium Storage Behavior in Natural Graphite using
           Ether‐based Electrolyte Systems (Adv. Funct. Mater. 4/2015)
    • Authors: Haegyeom Kim; Jihyun Hong, Young‐Uk Park, Jinsoo Kim, Insang Hwang, Kisuk Kang
      Pages: 652 - 652
      Abstract: The work presented by K. Kang and team on page 534 demonstrates that natural graphite, which has been regarded electrochemically inactive as electrode for Na ion batteries, can function as an excellent anode material for Na ion batteries when ether‐based electrolytes are used. The authors reveal Na storage mechanism in natural graphite in detail where Na+‐solvent co‐intercalation occurs combined with pseudocapacitive behaviors.
      PubDate: 2015-01-21T10:54:52.010484-05:
      DOI: 10.1002/adfm.201570029
       
  • Facile One‐Step Micropatterning Using Photodegradable Gelatin
           Hydrogels for Improved Cardiomyocyte Organization and Alignment
    • Authors: Kelly M. C. Tsang; Nasim Annabi, Francesca Ercole, Kun Zhou, Daniel J. Karst, Fanyi Li, John M. Haynes, Richard A. Evans, Helmut Thissen, Ali Khademhosseini, John S. Forsythe
      Pages: n/a - n/a
      Abstract: Hydrogels are often employed as temporary platforms for cell proliferation and tissue organization in vitro. Researchers have incorporated photodegradable (PD) moieties into synthetic polymeric hydrogels as a means of achieving spatiotemporal control over material properties. In this study protein‐based PD hydrogels composed of methacrylated gelatin and a crosslinker containing o‐nitrobenzyl ester groups are developed. The hydrogels are able to degrade rapidly and specifically in response to UV light and can be photopatterned to a variety of shapes and dimensions in a one‐step process. Micropatterned PD hydrogels are shown to improve cell distribution, alignment, and beating regularity of cultured neonatal rat cardiomyocytes. Overall this work introduces a new class of PD hydrogel based on natural and biofunctional polymers as cell culture substrates for improving cellular organization and function. A photodegradable hydrogel comprising a gelatin methacrylamide and an o‐nitrobenzyl PEG crosslinker is utilized to create patterned substrates for tissue engineering. Photodegradation enables a facile method of creating striped patterns onto the gels. Patterned hydrogels are shown to improve the degree of alignment and beating regularity of cultured cardiomyocytes, showing promise for culture platforms with spatiotemporal control capabilities.
      PubDate: 2014-12-28T15:39:36.512672-05:
      DOI: 10.1002/adfm.201403124
       
  • Improved Thermoelectric Performance of Silver
           Nanoparticles‐Dispersed Bi2Te3 Composites Deriving from Hierarchical
           Two‐Phased Heterostructure
    • Authors: Qihao Zhang; Xin Ai, Lianjun Wang, Yanxia Chang, Wei Luo, Wan Jiang, Lidong Chen
      Pages: n/a - n/a
      Abstract: A practical and feasible bottom‐up chemistry approach is demonstrated to dramatically enhance thermoelectric properties of the Bi2Te3 matrix by means of exotically introducing silver nanoparticles (AgNPs) for constructing thermoelectric composites with the hierarchical two‐phased heterostructure. By regulating the content of AgNPs and fine‐tuning the architecture of nanostructured thermoelectric materials, more heat‐carrying phonons covering the broad phonon mean free path distribution range can be scattered. The results show that the uniformly dispersed AgNPs not only effectively suppress the growth of Bi2Te3 grains, but also introduce nanoscale precipitates and form new interfaces with the Bi2Te3 matrix, resulting in a hierarchical two‐phased heterostructure, which causes intense scattering of phonons with multiscale mean free paths, and therefore significantly reduce the lattice thermal conductivity. Meanwhile, the improved power factor is maintained due to low‐energy electron filtering and excellent electrical transport property of Ag itself. Consequently, the maximum ZT is amazingly found to be enhanced by 304% arising from the hierarchical heterostructure when the AgNPs content reaches 2.0 vol%. This study offers an easily scalable and low‐cost route to construct a wide range of multiscale hierarchically heterostructured bulk composites with significant enhancement of thermoelectric performance. A hierarchical two‐phased heterostructure derving from silver nanoparticles and Bi2Te3 is constructed through a bottom‐up chemical route, which causes strong scattering of phonons across integrated length scales, significantly reducing the lattice thermal conductivity. Meanwhile, the power factor is improved due to the combination of low‐energy electron filtering and excellent electrical transport property of silver itself.
      PubDate: 2014-12-28T15:39:24.661366-05:
      DOI: 10.1002/adfm.201402663
       
  • Electronic Structures and Photoconversion Mechanism in
           Perovskite/Fullerene Heterojunctions
    • Authors: Ming‐Fai Lo; Zhi‐Qiang Guan, Tsz‐Wai Ng, Chiu‐Yee Chan, Chun‐Sing Lee
      Pages: n/a - n/a
      Abstract: It has been generally believed and assumed that organometal halide perovskites would form type II P–N junctions with fullerene derivatives (C60 or PCBM), and the P–N junctions would provide driving force for exciton dissociation in perovskite‐based solar cell. To the best of our knowledge, there is so far no experiment proof on this assumption. On the other hand, whether photogenerated excitons can intrinsically dissociate into free carrier in the perovskite without any assistance from a P–N junction is still controversial. To address these, the interfacial electronic structures of a vacuum‐deposited perovskite/C60 and a solution‐processed perovskite/PCBM junctions is directly measured by ultraviolet photoelectron spectroscopy. Contrary to the common believes, both junctions are found to be type I N–N junctions with band gap of the perovskites embedded by that of the fullerenes. Meanwhile, device with such a charge inert junction can still effectively functions as a solar cell. These results give direct experimental evidence that excitons are dissociated to free carriers in the perovskite film even without any assistance from a P–N junction. While perovskites/fullerene is commonly assumed to form a type II P–N junction with its internal E‐field facilitates exciton dissociation, it is found that perovskite/C60 (PCBM) junction is a charge inert type I N–N junction. Devices with such a junction show photovoltaic effects effectively, thus photogenerated excitons can indeed dissociate to free carriers in the perovskite film.
      PubDate: 2014-12-28T15:38:59.115808-05:
      DOI: 10.1002/adfm.201402692
       
  • On‐Demand Wrinkling Patterns in Thin Metal Films Generated from
           Self‐Assembling Liquid Crystals
    • Authors: Laurens T. de Haan; Philippe Leclère, Pascal Damman, Albertus P. H. J. Schenning, Michael G. Debije
      Pages: n/a - n/a
      Abstract: In this work, a new, universal method is described that uses the photopatterning of liquid crystals, which is accurately translated into a controlled, intricately wrinkled metal surface. Remarkably, the patterns have an oscillation in amplitude of the wrinkles. This rapid method allows generation of intricate multidomain patterns and continuous circular structures, including azimuthal, radial, and even higher complexity arrangements as examples. These wrinkled gold surfaces are also strikingly visual, which is interesting for applications ranging from diffractive elements to fine jewelry. Unique wrinkling patterns with oscillating amplitudes in any arbitrarily complex fashion are generated by controlling the alignment director of a liquid crystal network using photoalignment layers in combination with photomasks. The wrinkled gold surfaces are strikingly visual which is interesting for applications ranging from diffractive elements to fine jewelry. Image adapted with permission. Copyright 1973, Pink Floyd Music Ltd.
      PubDate: 2014-12-28T15:29:09.679138-05:
      DOI: 10.1002/adfm.201403399
       
  • Noncovalent Polymer‐Gatekeeper in Mesoporous Silica Nanoparticles as
           a Targeted Drug Delivery Platform
    • Authors: L. Palanikumar; Eun Seong Choi, Jae Yeong Cheon, Sang Hoon Joo, Ja‐Hyoung Ryu
      Pages: n/a - n/a
      Abstract: Selective targeting of tumor cells and release of drug molecules inside the tumor microenvironment can reduce the adverse side effects of traditional chemotherapeutics because of the lower dosages required. This can be achieved by using stimuli‐responsive targeted drug delivery systems. In the present work, a robust and simple one‐pot route is developed to synthesize polymer‐gatekeeper mesoporous silica nanoparticles by noncovalent capping of the pores of drug‐loaded nanocontainers with disulfide cross‐linkable polymers. The method offers very high loading efficiency because chemical modification of the mesoporous nanoparticles is not required; thus, the large empty pore volume of pristine mesoporous silica nanoparticles is entirely available to encapsulate drug molecules. Furthermore, the polymer shell can be easily decorated with a targeting ligand for selective delivery to specific cancer cells by subsequent addition of the thiol‐containing ligand molecule. The drug molecules loaded in the nanocontainers can be released by the degradation of the polymer shell in the intracellular reducing microenvironment, which consequentially induces cell death. A simple and robust polymer‐gatekeeper is developed to load a large mass of hydrophilic drugs inside the nonfunctionalized mesoporous silica. The ligand attached polymer‐gatekeeper can target specific cancer cells. Opening the gate inside cells by degradation of crosslinked polymer shell in response to the intracellular glutathione triggers the drug release inside the cancer cells to induce cell death.
      PubDate: 2014-12-23T12:32:08.976084-05:
      DOI: 10.1002/adfm.201402755
       
  • Materials and Wireless Microfluidic Systems for Electronics Capable of
           Chemical Dissolution on Demand
    • Authors: Chi Hwan Lee; Jae‐Woong Jeong, Yuhao Liu, Yihui Zhang, Yan Shi, Seung‐Kyun Kang, Jeonghyun Kim, Jae Soon Kim, Na Yeon Lee, Bong Hoon Kim, Kyung‐In Jang, Lan Yin, Min Ku Kim, Anthony Banks, Ungyu Paik, Yonggang Huang, John A. Rogers
      Pages: n/a - n/a
      Abstract: Electronics that are capable of destroying themselves, on demand and in a harmless way, might provide the ultimate form of data security. This paper presents materials and device architectures for triggered destruction of conventional microelectronic systems by means of microfluidic chemical etching of the constituent materials, including silicon, silicon dioxide, and metals (e.g., aluminum). Demonstrations in an array of home‐built metal‐oxide‐semiconductor field‐effect transistors that exploit ultrathin sheets of monocrystalline silicon and in radio‐frequency identification devices illustrate the utility of the approaches. Triggerable transient electronics are presented with the use of wireless microfluidics to enable complete dissolution of conventional microelectronic systems on demand in a controlled, programmable manner. Demonstration examples include triggered destruction of home‐built metal‐oxide‐semiconductor field‐effect transistors and commercial microchips in radio‐frequency identification device.
      PubDate: 2014-12-23T03:39:18.602377-05:
      DOI: 10.1002/adfm.201403573
       
  • Efficient Field Emission from Vertically Aligned Cu2O1‐δ(111)
           Nanostructure Influenced by Oxygen Vacancy
    • Authors: Suman Nandy; Ranjit Thapa, Mohit Kumar, Tapobrata Som, Nenad Bundaleski, Orlando M. N. D. Teodoro, Rodrigo Martins, Elvira Fortunato
      Pages: n/a - n/a
      Abstract: In the architecture described, cuprous oxide (Cu2O) is tamed to be highly (111) plane oriented nanostructure through adjusting the deposition postulate by glancing angle deposition technique. In the controlled atmosphere oxygen vacancy is introduced into the Cu2O crystal subsequently fostering an impurity energy state (Eim) close to the conduction band. Our model of Cu2O electronic structure using density functional theory suggests that oxygen vacancies enhance the electron donating ability because of unshared d‐electrons of Cu atoms (nearest to the vacancy site), allowing to pin the work function energy level around 0.28 eV compared to the bulk. This result is also complemented by Kelvin probe force microscopy analysis and X‐ray photoelectron spectroscopy method. Oxygen vacancy in Cu2O (Cu2O1‐δ) exhibits promising field emission properties with interesting field electron tunneling behavior at different applied fields. The films show very low turn‐on and threshold voltages of value 0.8 and 2.4 V μm−1 respectively which is influenced by the oxygen vacancy. Here, a correlation between the work function modulation due to the oxygen vacancy and enhancement of field emission of Cu2O1–δ nanostructure is demonstrated. This work reveals a promising new vision for Cu2O as a low power field emitter device. Cu2O1‐δ (111) exhibits promising field emission properties with interesting electron tunneling behavior at low turn‐on and threshold voltages of 0.8 and 2.4 V μm–1 respectively. DFT suggests that oxygen vacancies enhance the electron ­donating ability because of unshared d‐electrons of Cu atoms (nearest to the vacancy site), allowing an impurity energy state (Eim) close to the conduction band.
      PubDate: 2014-12-23T03:39:14.679663-05:
      DOI: 10.1002/adfm.201402910
       
  • Effect of Doping Concentration on Microstructure of Conjugated Polymers
           and Characteristics in N‐Type Polymer Field‐Effect Transistors
           
    • Authors: Chuan Liu; Junhyuk Jang, Yong Xu, Hyo‐Jung Kim, Dongyoon Khim, Won‐Tae Park, Yong‐Young Noh, Jang‐Joo Kim
      Pages: n/a - n/a
      Abstract: Despite extensive progress in organic field‐effect transistors, there are still far fewer reliable, high‐mobility n‐type polymers than p‐type polymers. It is demonstrated that by using dopants at a critical doping molar ratio (MR), performance of n‐type polymer poly[[N,N9‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,59‐(2,29‐bithiophene)] (P(NDI2DO‐T2)) field‐effect transistors (FETs) can be significantly improved and simultaneously optimized in mobility, on–off ratio, crystallinity, injection, and reliability. In particular, when using the organic dopant bis(cyclopentadienyl)–cobalt(II) (cobaltocene, CoCp2) at a low concentration (0.05 wt%), the FET mobility is increased from 0.34 to 0.72 cm2 V–1 s–1, and the threshold voltage was decreased from 32.7 to 8.8 V. The relationship between the MR of dopants and electrical characteristics as well as the evolution in polymer crystallinity revealed by synchrotron X‐ray diffractions are systematically investigated. Deviating from previous discoveries, it is found that mobility increases first and then decreases drastically beyond a critical value of MR. Meanwhile, the intensity and width of the main peak of in‐plane X‐ray diffraction start to decrease at the same critical MR. Thus, the mobility decrease is correlated with the disturbed in‐plane crystallinity of the conjugated polymer, for both organic and inorganic dopants. The method provides a simple and efficient approach to employing dopants to optimize the electrical performance and microstructure of P(NDI2DO‐T2). Performance and air stability is highly improved in n‐type organic field‐effect transistors by solution‐based chemical doping. The doping effects are systematically investigated the relationship between doping concentration and electrical characteristics as well as the evolution in polymer crystallinity revealed by synchrotron X‐ray diffractions.
      PubDate: 2014-12-23T03:35:18.296529-05:
      DOI: 10.1002/adfm.201402321
       
  • Slowing DNA Transport Using Graphene–DNA Interactions
    • Authors: Shouvik Banerjee; James Wilson, Jiwook Shim, Manish Shankla, Elise A. Corbin, Aleksei Aksimentiev, Rashid Bashir
      Pages: n/a - n/a
      Abstract: Slowing down DNA translocation speed in a nanopore is essential to ensuring reliable resolution of individual bases. Thin membrane materials enhance spatial resolution but simultaneously reduce the temporal resolution as the molecules translocate far too quickly. In this study, the effect of exposed graphene layers on the transport dynamics of both single (ssDNA) and double‐stranded DNA (dsDNA) through nanopores is examined. Nanopore devices with various combinations of graphene and Al2O3 dielectric layers in stacked membrane structures are fabricated. Slow translocations of ssDNA in nanopores drilled in membranes with layers of graphene are reported. The increased hydrophobic interactions between the ssDNA and the graphene layers could explain this phenomenon. Further confirmation of the hydrophobic origins of these interactions is obtained through reporting significantly faster translocations of dsDNA through these graphene layered membranes. Molecular dynamics simulations confirm the preferential interactions of DNA with the graphene layers as compared to the dielectric layer verifying the experimental findings. Based on our findings, we propose that the integration of multiple stacked graphene layers could slow down DNA enough to enable the identification of nucleobases. Graphene–DNA hydrophobic interactions slow DNA transport through a nanopore. The introduction of graphene layers makes the pore and membrane surface hydrophobic leading to sticking interactions with the ssDNA molecules. On the other hand, dsDNA has far less significant hydrophobic interactions with graphene as nucleobases are shielded in the helical structure.
      PubDate: 2014-12-22T06:18:01.642753-05:
      DOI: 10.1002/adfm.201403719
       
  • Understanding the Influence of Lattice Composition on the Photocatalytic
           Activity of Defect‐Pyrochlore‐Structured Semiconductor Mixed
           Oxides
    • Authors: Larissa Schwertmann; Anna Grünert, Anna Pougin, Chenghua Sun, Michael Wark, Roland Marschall
      Pages: n/a - n/a
      Abstract: The defect‐pyrochlore‐structured photocatalyst CsTaWO6 is an ideal starting material for anion doping from the gas phase, and is known to be highly active for solar hydrogen generation under simulated sunlight without co‐catalysts. To investigate the active site of CsTaWO6 for hydrogen generation and to understand the effects of the two d0 elements in the compound, systematic and successive element substitution of tantalum and tungsten on the crystallographic 16c sites of the starting material has been performed. Substituting lattice tantalum with niobium hardly changes the band gap of the resulting compounds CsTa(1 −x)Nb x WO6, but the photocatalytic activity for hydrogen generation and oxidation reactions is strongly influenced. By investigating the surface reactivity toward adsorption, surface effects altering the activity are identified. In contrast, substituting lattice tungsten with molybdenum reduces the band gap of CsTaWO6 into the visible‐light range. Materials containing Mo are however not able to generate hydrogen anymore, due to the altered conduction band positions proven by density functional theory calculations. CsTaMoO6 exhibits a band gap of 2.9 eV and evolves oxygen efficiently under UV light irradiation after CoPi co‐catalyst deposition, and even under visible light small amounts of oxygen. CsTaWO6 is a unique photocatalyst with two d0 elements, exhibiting a defect‐pyrochlore structure. By variation of its lattice composition, the photocatalytic properties of the material are investigated, in pursuit of revealing the active sites for water oxidation and reduction reactions without any cocatalyst, and for the first time oxygen evolution in visible light with CoPiCsTaMoO6.
      PubDate: 2014-12-22T06:17:39.356389-05:
      DOI: 10.1002/adfm.201403092
       
  • Liquid‐Crystalline Electrolytes for Lithium‐Ion Batteries:
           Ordered Assemblies of a Mesogen‐Containing Carbonate and a Lithium
           Salt
    • Authors: Junji Sakuda; Eiji Hosono, Masafumi Yoshio, Takahiro Ichikawa, Takuro Matsumoto, Hiroyuki Ohno, Haoshen Zhou, Takashi Kato
      Pages: n/a - n/a
      Abstract: Thermotropic liquid‐crystalline (LC) electrolytes for lithium‐ion batteries are developed for the first time. A rod‐like LC molecule having a cyclic carbonate moiety is used to form self‐assembled two‐dimensional ion‐conductive pathways with lithium salts. Electrochemical and thermal stability, and efficient ionic conduction is achieved for the liquid crystal. The mixture of the carbonate derivative and lithium bis(trifluoromethylsulfonyl)imide is successfully applied as an electrolyte in lithium‐ion batteries. Reversible charge–discharge for both positive and negative electrodes is observed for the lithium‐ion batteries composed of the LC electrolyte. Thermotropic liquid‐crystalline (LC) electrolyte for lithium‐ion batteries is developed. The LC electrolyte is successfully used for lithium‐ion batteries. The electrolyte is a mixture of a carbonate‐based rod‐like molecule and lithium bis(trifluoromethylsulfonyl)imide. This is the first demonstration of the applicability of thermotropic LC electrolytes to lithium‐ion batteries.
      PubDate: 2014-12-22T06:17:33.700504-05:
      DOI: 10.1002/adfm.201402509
       
  • Role of PbSe Structural Stabilization in Photovoltaic Cells
    • Authors: Demet Asil; Brian J. Walker, Bruno Ehrler, Yana Vaynzof, Alessandro Sepe, Sam Bayliss, Aditya Sadhanala, Philip C. Y. Chow, Paul E. Hopkinson, Ullrich Steiner, Neil C. Greenham, Richard H. Friend
      Pages: n/a - n/a
      Abstract: Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC films during processing. Here, an improvement in long‐range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer‐scale rearrangement of PbSe NCs during ligand exchange, improving the long‐range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fission solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface‐bound chloride ions, reduced sub‐bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts. Inorganic treatment of nanocrystals removes traps, increases long‐range ordering of the symmetry, and improves stability in solar cells. A combination of optical, electronic, and material characterization tools demonstrates that chloride treatment confers many benefits on photovoltaic materials.
      PubDate: 2014-12-22T06:17:04.990267-05:
      DOI: 10.1002/adfm.201401816
       
  • An Advanced Nitrogen‐Doped Graphene/Cobalt‐Embedded Porous
           Carbon Polyhedron Hybrid for Efficient Catalysis of Oxygen Reduction and
           Water Splitting
    • Authors: Yang Hou; Zhenhai Wen, Shumao Cui, Suqin Ci, Shun Mao, Junhong Chen
      Pages: n/a - n/a
      Abstract: A novel hybrid electrocatalyst consisting of nitrogen‐doped graphene/cobalt‐embedded porous carbon polyhedron (N/Co‐doped PCP//NRGO) is prepared through simple pyrolysis of graphene oxide‐supported cobalt‐based zeolitic imidazolate‐frameworks. Remarkable features of the porous carbon structure, N/Co‐doping effect, introduction of NRGO, and good contact between N/Co‐doped PCP and NRGO result in a high catalytic efficiency. The hybrid shows excellent electrocatalytic activities and kinetics for oxygen reduction reaction in basic media, which compares favorably with those of the Pt/C catalyst, together with superior durability, a four‐electron pathway, and excellent methanol tolerance. The hybrid also exhibits superior performance for hydrogen evolution reaction, offering a low onset overpotential of 58 mV and a stable current density of 10 mA cm−2 at 229 mV in acid media, as well as good catalytic performance for oxygen evolution reaction (a small overpotential of 1.66 V for 10 mA cm−2 current density). The dual‐active‐site mechanism originating from synergic effects between N/Co‐doped PCP and NRGO is responsible for the excellent performance of the hybrid. This development offers an attractive catalyst material for large‐scale fuel cells and water splitting technologies. A novel hybrid electrocatalyst consisting of nitrogen‐doped graphene/cobalt‐embedded porous carbon polyhedron (N/Co‐doped PCP//NRGO) is obtained through a simple pyrolysis of graphene oxide‐supported cobalt‐based zeolitic imidazolate‐frameworks. The hybrid exhibits excellent electrocatalytic activities for oxygen reduction, hydrogen evolution, and oxygen evolution reactions with good stability. The enhanced performance is correlated with the dual‐active‐site mechanism originating from synergic ­effects between N/Co‐doped PCP and NRGO sheets.
      PubDate: 2014-12-22T06:15:14.977837-05:
      DOI: 10.1002/adfm.201403657
       
  • Synthesis of Dumbbell‐Like Gold–Metal Sulfide Core–Shell
           Nanorods with Largely Enhanced Transverse Plasmon Resonance in Visible
           Region and Efficiently Improved Photocatalytic Activity
    • Authors: Liang Ma; Shan Liang, Xiao‐Li Liu, Da‐Jie Yang, Li Zhou, Qu‐Quan Wang
      Pages: n/a - n/a
      Abstract: The metallic nanostructures with unique properties of tunable plasmon resonance and large field enhancement have been cooperated with semiconductor to construct hetero‐nanostructures for various applications. Herein, a general and facile approach to synthesize uniform dumbbell‐like gold–sulfide core–shell hetero‐nanostructures is reported. The transformation from Au nanorods (NRs) to dumbbell‐like Au NRs and coating of metal sulfide shells (including Bi2S3, CdS, CuxS, and ZnS) are achieved in a one‐pot reaction. Due to the reshaping of Au core and the deposition of sulfide shell, the plasmon resonances of Au NRs are highly enhanced, especially the about 2 times enhancement for the visible transverse plasmon resonance compared with the initial Au NRs. Owing to the highly enhanced visible light absorption and strong local electric field, we find the photocatalytic activity of dumbbell‐like Au–Bi2S3 NRs is largely enhanced compared with pure Bi2S3 and normal Au–Bi2S3 NRs by testing the photodegradation rate of Rhodamine B (RhB). Moreover, the second‐layer sulfide can be coated and the double‐shell Au–Bi2S3–CdS hetero‐nanostructures show further improved photodegradation rate, especially about 2 times than that of Degussa P25 TiO2 (P25) ascribing to the optimum band arrangement and then the prolonged lifetime of photo‐generated carriers. A facile method is reported to synthesize dumbbell‐like Au–metal sulfide nanorods (including CdS, Bi2S3, ZnS, and CuxS) with highly enhanced visible light absorption and strong local electric field. The double‐shell Au–Bi2S3–CdS hetero‐nanostructures show efficiently improved photodegradation rate, especially about 2 times than that of Degussa P25 TiO2 (P25).
      PubDate: 2014-12-22T06:14:57.812803-05:
      DOI: 10.1002/adfm.201403398
       
  • Controlling Polymorphism in Poly(3‐Hexylthiophene) through Addition
           of Ferrocene for Enhanced Charge Mobilities in Thin‐Film Transistors
           
    • Authors: Brandon H. Smith; Michael B. Clark, Hao Kuang, Christopher Grieco, Alec V. Larsen, Chenhui Zhu, Cheng Wang, Alexander Hexemer, John B. Asbury, Michael J. Janik, Enrique D. Gomez
      Pages: n/a - n/a
      Abstract: Crystalline organic molecules often exhibit the ability to assemble into multiple crystal structures depending on the processing conditions. Exploiting this polymorphism to optimize molecular orbital overlap between adjacent molecules in the unit lattice is an effective method for improving charge transport within the material. In this study, grazing incident X‐ray diffraction was employed to demonstrate the formation of tighter π‐π stacking poly(3‐hexylthiophene‐2,5‐diyl) polymorphs in films spin coated from ferrocene‐containing solutions. As a result, the addition of ferrocene to casting solutions yields thin‐film transistors which exhibit approximately three times higher source‐drain currents and charge mobilities than neat polymer devices. Nevertheless, XPS depth profiling and NMR analyses of the active layer reveal that all ferrocene is removed during the spin coating process, which may be an essential factor to achieve high mobilities. Such insights gleaned from ferrocene/poly(3‐hexylthiophene‐2,5‐diyl) mixtures can serve as a template for selection and optimization of other small molecule/polymer systems with greater baseline charge mobilities. The electrical performance of poly(3‐hexylthiophene) thin‐film transistors increases with addition of ferrocene. Intermediate‐to‐high concentrations of ferrocene included in poly(3‐hexylthiophene) spin casting solutions produces transistors demonstrating roughly three times higher source‐drain current and charge mobility than neat components. Interactions between the polymer and metallocene lead to the formation of polymorphs with closer π‐stacking that decreases the charge hopping distance.
      PubDate: 2014-12-15T11:59:56.152157-05:
      DOI: 10.1002/adfm.201403089
       
  • Dynamic Fluoroalkyl Polyethylene Glycol Co‐Polymers: A New Strategy
           for Reducing Protein Adhesion in Lab‐on‐a‐Chip Devices
    • Authors: Mahesh K. Sarvothaman; Kris S. Kim, Brendon Seale, Peter M. Brodersen, Gilbert C. Walker, Aaron R. Wheeler
      Pages: 506 - 515
      Abstract: Non‐specific adsorption of biomolecules (or “biofouling”) is a major problem in microfluidics and many other applications. The problem is particularly pernicious in digital microfluidics (DMF, a technique in which droplets are manipulated electrodynamically on an array of electrodes coated with a hydrophobic insulator), as local increases in surface energy that arise from fouling can cause droplet movement to fail. We report a new solution to this problem: a device coating bearing a combination of fluorinated poly(ethylene glycol) functionalities (FPEG) and perfluorinated methacrylate (FA) moieties. A range of different FPEG‐FA copolymers were synthesized containing varying amounts of FPEG relative to the fluorinated backbone. Coatings with low%FPEG were found to result in significant reductions in protein adsorption and improvements in device lifetime (up to 5.5‐fold) relative to the state of the art. An analysis of surface topology and chemistry suggests that FPEG‐FA surfaces undergo a dynamic reconstruction upon activation by applying DMF driving potentials, with FPEG groups forming vertical protrusions out of the plane of the device surface. An analysis of changes in surface wettability and adhesion as a function of activation supports this hypothesis. This innovation represents an advance for digital microfluidics, and may also find use in other applications that are currently limited by biofouling. An antifouling coating is described that improves digital microfluidic device lifetime up to 5.5‐fold relative to the state of the art. The material is dynamic: under standard conditions, the surface is flat and fluorinated; upon applying an electrical potential, the surface becomes activated, forming nanometer‐sized fluoropegylated structures.
      PubDate: 2014-11-20T03:09:58.008631-05:
      DOI: 10.1002/adfm.201402218
       
  • Submicrometer‐Sized ZIF‐71 Filled Organophilic Membranes for
           Improved Bioethanol Recovery: Mechanistic Insights by Monte Carlo
           Simulation and FTIR Spectroscopy
    • Authors: Lik H. Wee; Yanbo Li, Kang Zhang, Patrizia Davit, Silvia Bordiga, Jianwen Jiang, Ivo F. J. Vankelecom, Johan A. Martens
      Pages: 516 - 525
      Abstract: Template‐free self‐assembly synthesis of nano‐sized metal‐organic frameworks (MOFs) is of particular interest in MOF research since organized nanostructures possessing distinctive properties are useful for many advanced applications. In this work, the facile room temperature synthesis of robust submicrometer‐sized ZIF‐71 crystals with different particle sizes (140, 290, or 430 nm), having a high permanent microporosity (SBET = 827 cm2 g−1) and synthesis yield up to 80% based on Zn on a gram‐scale, is reported. These small ZIF‐71 particles are ideal filler for the fabrication of thinner and homogeneous polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) with excellent filler dispersion and filler‐polymer adhesion at high loading up to 40 wt%, as confirmed by scanning electron microscopy. Pervaporation tests using these submicrometer‐sized ZIF‐71 filled MMMs show significant improvement for bioethanol recovery. Interesting phenomena of i) reversible ethanol‐ethanol hydrogen interaction in the ethanol liquid‐phase and ii) irreversible hydrogen interaction of ethanol and –Cl functional group in the α‐cages and octagonal prismatic cages of ZIF‐71 in ethanol vapor‐phase are discovered for the first time by a Fourier transform infrared spectroscopy (FTIR) study. In full agreement with molecular simulation results, these explain fundamentally the ZIF‐71 filled MMMs pervaporation performance. Gram scale synthesis of submicrometer‐sized ZIF‐71 crystal is demonstrated via a simple mixed solvent approach for improving mixed matrix membrane pervaporation separation of bioethanol. The host–guest chemistry at its molecular level is unravelled by grand canonical Monte Carlo simulation and FTIR spectroscopy. The results reveal a strong hydrogen interaction between the cages of ZIF‐71 and ethanol, well explaining the pervaporation performance.
      PubDate: 2014-11-19T06:56:18.223768-05:
      DOI: 10.1002/adfm.201402972
       
  • An Interface‐Induced Co‐Assembly Approach Towards Ordered
           Mesoporous Carbon/Graphene Aerogel for High‐Performance
           Supercapacitors
    • Authors: Ruili Liu; Li Wan, Shaoqing Liu, Lixia Pan, Dongqing Wu, Dongyuan Zhao
      Pages: 526 - 533
      Abstract: Hierarchically porous composites with mesoporous carbon wrapping around the macroporous graphene aerogel can combine the advantages of both components and are expected to show excellent performance in electrochemical energy devices. However, the fabrication of such composites is challenging due to the lack of an effective strategy to control the porosity of the mesostructured carbon layers. Here an interface‐induced co‐assembly approach towards hierarchically mesoporous carbon/graphene aerogel composites, possessing interconnected macroporous graphene networks covered by highly ordered mesoporous carbon with a diameter of ≈9.6 nm, is reported. And the orientation of the mesopores (vertical or horizontal to the surface of the composites) can be tuned by the ratio of the components. As the electrodes in supercapacitors, the resulting composites demonstrate outstanding electrochemical performances. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications. When ordered mesoporous carbons meet graphene areogel, the resulting hierarchically porous composites conglomerating the advantages of both components are obtained and exhibit excellent performance in electrochemical energy devices. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications.
      PubDate: 2014-11-19T06:56:37.464703-05:
      DOI: 10.1002/adfm.201403280
       
  • Sodium Storage Behavior in Natural Graphite using Ether‐based
           Electrolyte Systems
    • Authors: Haegyeom Kim; Jihyun Hong, Young‐Uk Park, Jinsoo Kim, Insang Hwang, Kisuk Kang
      Pages: 534 - 541
      Abstract: This work reports that natural graphite is capable of Na insertion and extraction with a remarkable reversibility using ether‐based electrolytes. Natural graphite (the most well‐known anode material for Li–ion batteries) has been barely studied as a suitable anode for Na rechargeable batteries due to the lack of Na intercalation capability. Herein, graphite is not only capable of Na intercalation but also exhibits outstanding performance as an anode for Na ion batteries. The graphite anode delivers a reversible capacity of ≈150 mAh g−1 with a cycle stability for 2500 cycles, and more than 75 mAh g−1 at 10 A g−1 despite its micrometer‐size (≈100 μm). An Na storage mechanism in graphite, where Na+‐solvent co‐intercalation occurs combined with partial pseudocapacitive behaviors, is revealed in detail. It is demonstrated that the electrolyte solvent species significantly affect the electrochemical properties, not only rate capability but also redox potential. The feasibility of graphite in a Na full cell is also confirmed in conjunction with the Na1.5VPO4.8F0.7 cathode, delivering an energy of ≈120 Wh kg−1 while maintaining ≈70% of the initial capacity after 250 cycles. This exceptional behavior of natural graphite promises new avenues for the development of cost‐effective and reliable Na ion batteries. This study reports an unusual Na storage behavior in natural graphite through Na+‐solvent co‐intercalation combined with pseudocapacitive behaviors using ether‐based electrolytes which is confirmed by electrochemical and ex situ analyses. This work can be used as a foundation for further studies on graphite as a promising anode for NIBs in conjunction with its straightforward advantages, such as low costs, earth abundance, environmental friendliness, and non‐toxicity.
      PubDate: 2014-11-20T03:10:35.691029-05:
      DOI: 10.1002/adfm.201402984
       
  • Finite‐Temperature Properties of Rare‐Earth‐Substituted
           BiFeO3 Multiferroic Solid Solutions
    • Authors: Bin Xu; Dawei Wang, Jorge Íñiguez, Laurent Bellaiche
      Pages: 552 - 558
      Abstract: Rare‐earth substitution in the multiferroic BiFeO3 (BFO) material holds promise for resolving drawbacks inherent to pure BFO, and for enhancing piezoelectric and magneto‐electric properties via a control of structural and magnetic characteristics. Rare‐earth‐doped BFO solid solutions also exhibit unresolved features, such as the precise nature and atomic characteristics of some intermediate phases. Here, an effective Hamiltonian scheme is developed that allows the investigation of finite‐temperature properties of these systems from an atomistic point of view. In addition to reproducing experimental results of Nd‐doped BFO on structural and magnetic transitions with temperature and composition, this scheme also provides an answer (in form of nanotwins) to these intermediate phases. A striking magneto‐electric effect—namely a paramagnetic–to–antiferromagnetic transition that is induced by an applied electric field—is further predicted near critical compositions, with the resulting structural path being dependent on the orientation of the electric field relative to the antiferroelectric vector. Rare‐earth substituted BiFeO3 (BFO) holds great promise as a piezoelectric and magnetoelectric material. A first‐principles based scheme is developed to investigate the structural and magnetic transitions of Nd‐doped BFO at finite temperatures. Thanks to this new method, the nature of the composition‐induced transformations is unveiled, and the possibility to control the magnetic order by an applied electric field is demonstrated.
      PubDate: 2014-12-02T02:55:57.584523-05:
      DOI: 10.1002/adfm.201403811
       
  • Structured Reduced Graphene Oxide/Polymer Composites for
           Ultra‐Efficient Electromagnetic Interference Shielding
    • Authors: Ding‐Xiang Yan; Huan Pang, Bo Li, Robert Vajtai, Ling Xu, Peng‐Gang Ren, Jian‐Hua Wang, Zhong‐Ming Li
      Pages: 559 - 566
      Abstract: A high‐performance electromagnetic interference shielding composite based on reduced graphene oxide (rGO) and polystyrene (PS) is realized via high‐pressure solid‐phase compression molding. Superior shielding effectiveness of 45.1 dB, the highest value among rGO based polymer composite, is achieved with only 3.47 vol% rGO loading owning to multi‐facet segregated architecture with rGO selectively located on the boundaries among PS multi‐facets. This special architecture not only provides many interfaces to absorb the electromagnetic waves, but also dramatically reduces the loading of rGO by confining the rGO at the interfaces. Moreover, the mechanical strength of the segregated composite is dramatically enhanced using high pressure at 350 MPa, overcoming the major disadvantage of the composite made by conventional‐pressure (5 MPa). The composite prepared by the higher pressure shows 94% and 40% increment in compressive strength and compressive modulus, respectively. These results demonstrate a promising method to fabricate an economical, robust, and highly efficient EMI shielding material. The rGO/PS composite with segregated architecture is realized via high‐pressure solid‐phase compression molding for efficient EMI shielding. The highest EMI SE of 45.1 dB among rGO based polymer composites is achieved with only 3.47 vol% rGO loading. The high‐pressure molded composite shows 94% and 40% enhancement in compressive strength and modulus compared to conventional‐pressure molded composite.
      PubDate: 2014-12-02T02:55:55.280079-05:
      DOI: 10.1002/adfm.201403809
       
  • Enhanced Light‐Harvesting by Integrating Synergetic Microcavity and
           Plasmonic Effects for High‐Performance ITO‐Free Flexible
           Polymer Solar Cells
    • Authors: Kai Yao; Xu‐Kai Xin, Chu‐Chen Chueh, Kung‐Shih Chen, Yun‐Xiang Xu, Alex K.‐Y. Jen
      Pages: 567 - 574
      Abstract: In this work, a high‐performance ITO‐free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO‐free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well‐manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light‐harvesting with microcavity resonance in the regions of 400–500 nm and 600–700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light‐harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs. Highly efficient ITO‐free, flexible polymer solar cells are successfully demon­strated by integrating the plasmonic effect into microcavity‐based devices. By carefully controlling the embedded Ag nanoprisms sizes, the power conversion efficiency of the devices can be significantly enhanced to as high as 9.4% on both glass and flexible (PET) substrates.
      PubDate: 2014-12-06T09:48:20.847223-05:
      DOI: 10.1002/adfm.201403297
       
  • Epoxy Toughening with Low Graphene Loading
    • Authors: Yong Tae Park; Yuqiang Qian, Clement Chan, Taewon Suh, Mehrdad Ghasemi Nejhad, Christopher W. Macosko, Andreas Stein
      Pages: 575 - 585
      Abstract: The toughening effects of graphene and graphene‐derived materials on thermosetting epoxies are investigated. Graphene materials with various structures and surface functional groups are incorporated into an epoxy resin by in situ polymerization. Graphene oxide (GO) and GO modified with amine‐terminated poly(butadiene‐acrylonitrile) (ATBN) are chosen to improve the dispersion of graphene nanosheets in epoxy and increase their interfacial adhesion. An impressive toughening effect is observed with less than 0.1 wt% graphene. A maximum in toughness at loadings as small as 0.02 wt% or 0.04 wt% is observed for all four types of graphene studied. An epoxy nanocomposite with ATBN‐modified GO shows a 1.5‐fold improvement in fracture toughness and a corresponding 2.4‐fold improvement in fracture energy at 0.04 wt% of graphene loading. At such low loadings, these graphene‐type materials become economically feasible components of nanocomposites. A microcrack mechanism is proposed based on microscopy of the fracture surfaces. Due to the stress concentration by graphene nanosheets, microcracks may be formed to absorb the fracture energy. However, above a certain graphene concentration, the coalescence of microcracks appears to facilitate crack propagation, lowering the fracture toughness. Crack deflection and pinning likely contribute to the slow increase in fracture toughness at higher loadings. Epoxy toughening by graphene is demonstrated at graphene loadings as low as 0.02 wt%. Functionalization of graphene can further improve the toughening effect at such a small loading level. A mechanism based on the formation and coalescence of microcracks generated by graphene is proposed to explain the fracture behavior of epoxy/graphene nanocomposites.
      PubDate: 2014-12-06T09:48:16.108792-05:
      DOI: 10.1002/adfm.201402553
       
  • A Timely Synthetic Tailoring of Biaxially Extended
           Thienylenevinylene‐Like Polymers for Systematic Investigation on
           Field‐Effect Transistors
    • Authors: Dohyuk Yoo; Benjamin Nketia‐Yawson, Seok‐Ju Kang, Hyungju Ahn, Tae Joo Shin, Yong‐Young Noh, Changduk Yang
      Pages: 586 - 596
      Abstract: Considering there is growing interest in the superior charge transport in the (E)‐2‐(2‐(thiophen‐2‐yl)‐vinyl)thiophene (TVT)‐based polymer family, an essential step forward is to provide a deep and comprehensive understanding of the structure–property relationships with their polymer analogs. Herein, a carefully chosen set of DPP‐TVT‐n polymers are reported here, involving TVT and diketopyrrolopyrrole (DPP) units that are constructed in combination with varying thiophene content in the repeat units, where n is the number of thiophene spacer units. Their OFET characteristics demonstrate ambipolar behavior; in particular, with DPP‐TVT‐0 a nearly balanced hole and electron transport are observed. Interestingly, the majority of the charge‐transport properties changed from ambipolar to p‐type dominant, together with the enhanced hole mobilities, as the electron‐donating thiophene spacers are introduced. Although both the lamellar d‐spacings and π‐stacking distances of DPP‐TVT‐n decreased with as the number of thiophene spacers increased, DPP‐TVT‐1 clearly shows the highest hole mobility (up to 2.96 cm2 V−1 s−1) owing to the unique structural conformations derived from its smaller paracrystalline distortion parameter and narrower plane distribution relative to the others. These in‐depth studies should uncover the underlying structure–property relationships in a relevant class of TVT‐like semiconductors, shedding light on the future design of top‐performing semiconducting polymers. A tactically chosen set of DPP‐TVT‐n polymers involving biaxially extended thienylenevinylene (TVT) and diketopyrrolopyrrole (DPP) units is synthesized by tuning the thiophene‐to‐vinylene ratio in the backbone. This in‐depth study uncovers that the degrees of the paracrystalline nature and the (h00) plane distribution, rather than densely packed organization, play a critical role in facilitating charge transport.
      PubDate: 2014-12-08T11:21:53.449091-05:
      DOI: 10.1002/adfm.201403527
       
  • Graphene Foam with Switchable Oil Wettability for Oil and Organic Solvents
           Recovery
    • Authors: Haiguang Zhu; Dongyun Chen, Najun Li, Qingfeng Xu, Hua Li, Jinghui He, Jianmei Lu
      Pages: 597 - 605
      Abstract: One of the most pervasive environmental issues is water contaminated with oil or organic solvents; this global challenge calls for emerging materials that could effectively separate oil or organic solvents from water. Here, such a material is presented by integrating 3D porous graphene foam (GF) with a smart pH‐responsive surface, showing switchable superoleophilic and superoleophobic properties in response to the medium pH. The key chemistry applied in this study is to modify the 3D porous GF with an amphiphilic copolymer containing a block of poly(2‐vinylpyridine) and polyhexadecyl acrylate (P2VP‐b‐PHA), resulting in a smart GF (ss‐GF) with an either superoleophilic or superoleophobic surface at different medium pH. The as‐designed ss‐GF can effectively absorb oil or organic solvents from the aqueous media by using its superoleophilic surface at pH of 7.0, and it can also completely release the adsorbates when the pH is switched to 3.0 (and the surface of ss‐GF is therefore shifted to superoleophobic); with a continuous operation of many cycles (e.g., >10). Furthermore, the as‐designed ss‐GF shows superior absorption capacity for oil and organic solvent, with a high capacity of ≈196 times of the weight relative to that of the pristine ss‐GF. The present work suggests encouraging applications of the ss‐GF to water–oil and water–organic solvent separation. The pH‐responsive material based on graphene foam coated poly(2‐vinylpyridine) and polyhexadecyl acrylate is successfully prepared for removing oil and organic solvents from water. It can switch its adsorption and desorption of oil and organic solvents in response to the change of pH. In addition, it exhibits high adsorption capacity and excellent reusability.
      PubDate: 2014-12-15T04:41:05.870432-05:
      DOI: 10.1002/adfm.201403864
       
  • Ambient‐Stable, Annealing‐Free, and Ambipolar Organic
           Field‐Effect Transistors Based on Solution‐Processable
           Poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene)
           without Long Alkyl Side Chains
    • Authors: Chi‐Jui Chiang; Jyh‐Chien Chen, Hsiang‐Yen Tsao, Kuan‐Yi Wu, Chien‐Lung Wang
      Pages: 606 - 614
      Abstract: An ambipolar conjugated polymer CF3‐PBTV, poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene), consisting of thienylenevinylene as the donor and trifluoromethyl‐substituted biphenyl as the acceptor has been successfully synthesized. CF3‐PBTV shows solution‐processability without electrically insulating long alkyl side chains. Grazing incidence X‐ray diffraction results suggest a nearly equal population of flat‐on and end‐on domains in CF3‐PBTV thin film. The excellent ambipolarity of CF3‐PBTV is demonstrated by well‐equivalent charge mobilities of 0.065 and 0.078 cm2 V−1 s−1 for p‐ and n‐channel, respectively. The organic field‐effect transistors (OFET) also shows very high on/off ratio (≈107) which is attributed to the relatively large bandgap and low‐lying highest occupied molecular orbital (HOMO) of CF3‐PBTV. The OFET performance barely changes after the device is stored in ambient conditions for 90 days. The ambient‐stability is attributed to the enhanced oxidative stability from its low‐lying HOMO and the better moisture resistance from its fluorine contents. The performance of CF3‐PBTV based OFET is annealing independent. It is noteworthy that the solution‐processable, ambipolar, and thienylenevinylene‐containing conjugated polymer without any long alkyl side chains is reported for the first time. And to the best of our knowledge, it is the first ambient‐stable, annealing‐free OFET with well‐equivalent ambipolarity. An ambipolar organic field‐effect transistor based on a solution‐processable conjugated polymer, CF3‐PBTV, is developed. The solution‐processability is achieved without long alkyl side chains. The organic field‐effect transistor shows well‐equivalent ambipolarity with hole mobility of 0.065 cm2 V−1 s−1 and electron mobility of 0.078 cm2 V−1 s−1 in air. This annealing‐free OFET also demonstrates very high on/off ratio (≈107) and excellent ambient‐stability over 90 days.
      PubDate: 2014-12-15T04:36:02.846211-05:
      DOI: 10.1002/adfm.201403428
       
  • Intratumoral Thermal Reading During Photo‐Thermal Therapy by
           Multifunctional Fluorescent Nanoparticles
    • Authors: Elisa Carrasco; Blanca del Rosal, Francisco Sanz‐Rodríguez, Ángeles Juarranz de la Fuente, Patricia Haro Gonzalez, Ueslen Rocha, Kagola Upendra Kumar, Carlos Jacinto, José García Solé, Daniel Jaque
      Pages: 615 - 626
      Abstract: The tremendous development of nanotechnology is bringing us closer to the dream of clinical application of nanoparticles in photothermal therapies of tumors. This requires the use of specific nanoparticles that must be highly biocompatible, efficient light‐to‐heat converters and fluorescent markers. Temperature reading by the heating nanoparticles during therapy appears of paramount importance to keep at a minimum the collateral damage that could arise from undesirable excessive heating. In this work, this thermally controlled therapy is possible by using Nd3+ ion‐doped LaF3 nanocrystals. Because of the particular optical features of Nd3+ ions at high doping concentrations, these nanoparticles are capable of in vivo photothermal heating, fluorescent tumor localization and intratumoral thermal sensing. The successful photothermal therapy experiments here presented highlight the importance of controlling therapy parameters based on intratumoral temperature measurements instead of on the traditionally used skin temperature measurements. In fact, significant differences between intratumoral and skin temperatures do exist and could lead to the appearance of excessive collateral damage. These results open a new avenue for the real application of nano­particle‐based photothermal therapy at clinical level. The unique ability of Neodymium‐doped LaF3 nanoparticles for simultaneous heating and temperature sensing is used here for the development of efficient and damage‐free photo‐thermal treatment of cancer tumors with real time intratumoral thermal reading.
      PubDate: 2014-12-06T09:48:24.85848-05:0
      DOI: 10.1002/adfm.201403653
       
  • Facile Synthesis of Hematite Quantum‐Dot/Functionalized
           Graphene‐Sheet Composites as Advanced Anode Materials for Asymmetric
           Supercapacitors
    • Authors: Hui Xia; Caiyun Hong, Bo Li, Bin Zhao, Zixia Lin, Mingbo Zheng, Serguei V. Savilov, Serguei M. Aldoshin
      Pages: 627 - 635
      Abstract: For building high‐energy density asymmetric supercapacitors, developing anode materials with large specific capacitance remains a great challenge. Although Fe2O3 has been considered as a promising anode material for asymmetric supercapacitors, the specific capacitance of the Fe2O3‐based anodes is still low and cannot match that of cathodes in the full cells. In this work, a composite material with well dispersed Fe2O3 quantum dots (QDs, ≈2 nm) decorated on functionalized graphene‐sheets (FGS) is prepared by a facile and scalable method. The Fe2O3 QDs/FGS composites exhibit a large specific capacitance up to 347 F g−1 in 1 m Na2SO4 between –1 and 0 V versus Ag/AgCl. An asymmetric supercapacitor operating at 2 V is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 aqueous electrolyte. The Fe2O3/FGS//MnO2/FGS asymmetric supercapacitor shows a high energy density of 50.7 Wh kg−1 at a power density of 100 W kg−1 as well as excellent cycling stability and power capability. The facile synthesis method and superior supercapacitive performance of the Fe2O3 QDs/FGS composites make them promising as anode materials for high‐performance asymmetric supercapacitors. Hematite quantum‐dot/functionalized graphene‐sheet composites are prepared and the composite electrode can reach a maximum specific capacitance of 347 F g−1, which is much larger than the reported values for the Fe2O3‐based electrodes in neutral aqueous electrolyte. A high‐performance 2 V asymmetrical supercapacitor is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 electrolyte.
      PubDate: 2014-12-12T04:34:47.061797-05:
      DOI: 10.1002/adfm.201403554
       
  • Shear‐Thinning Supramolecular Hydrogels with Secondary Autonomous
           Covalent Crosslinking to Modulate Viscoelastic Properties In Vivo
    • Authors: Christopher B. Rodell; John W. MacArthur, Shauna M. Dorsey, Ryan J. Wade, Leo L. Wang, Y. Joseph Woo, Jason A. Burdick
      Pages: 636 - 644
      Abstract: Clinical percutaneous delivery of synthetically engineered hydrogels remains limited due to challenges posed by crosslinking kinetics—too fast leads to delivery failure, too slow limits material retention. To overcome this challenge, supramolecular assembly is exploited to localize hydrogels at the injection site and introduce subsequent covalent crosslinking to control final material properties. Supramolecular gels are designed through the separate pendant modifications of hyaluronic acid (HA) by the guest–host pair cyclodextrin and adamantane, enabling shear‐thinning injection and high target site retention (>98%). Secondary covalent crosslinking occurs via addition of thiols and Michael‐acceptors (i.e., methacrylates, acrylates, vinyl sulfones) on HA and increases hydrogel moduli (E = 25.0 ± 4.5 kPa) and stability (>3.5 fold in vivo at 28 d). Application of the dual‐crosslinking hydrogel to a myocardial infarct model shows improved outcomes relative to untreated and supramolecular hydrogel alone controls, demonstrating its potential in a range of applications where the precise delivery of hydrogels with tunable properties is desired. Injectable hyaluronic acid hydrogels with high target site retention, tunable properties, and potential for percutaneous delivery are developed through a tandem crosslinking approach. Supramolecular crosslinking provides initial hydrogel formation and shear‐thinning delivery, while secondary covalent crosslinking stabilizes the hydrogel in situ. Material properties and treatment of myocardial infarct are examined.
      PubDate: 2014-12-12T04:35:06.358554-05:
      DOI: 10.1002/adfm.201403550
       
  • Orthogonal Molecular Structure for Better Host Material in Blue
           Phosphorescence and Larger OLED White Lighting Panel
    • Authors: Lei Ding; Shou‐Cheng Dong, Zuo‐Quan Jiang, Hua Chen, Liang‐Sheng Liao
      Pages: 645 - 650
      Abstract: High‐efficiency blue phosphorescence devices with external quantum efficiencies above 25% are developed using a new bipolar host material, diphenyl(10‐phenyl‐10H‐spiro[acridine‐9,9′‐fluoren]‐2′‐yl)phosphine oxide (POSTF), which is constructed in orthogonal molecular structure with a spiro‐coree. The separation of bipolarity from effective spiro‐fluorene‐triphenylamine (STF) structure is elucidated and its versatility in device is evaluated by two kinds of sky‐blue phosphors. Noticeably, large‐size white light‐emitting panel (150 mm × 150 mm) is fabricated with max power efficiency of 75.9 l m W−1 using this new host. Over 25% external quantum efficiency in blue phosphorescence by spiro‐bipolar host diphenyl(10‐phenyl‐10H‐spiro[acridine‐9,9′‐fluoren]‐2′‐yl)phosphine oxide is achieved and over 75 lm W‐1 large white organic light‐emitting diodes lighting panel is fabricated.
      PubDate: 2014-12-15T04:37:51.518528-05:
      DOI: 10.1002/adfm.201403402
       
 
 
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