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CHEMISTRY (576 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: 26)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 15)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 9)
ACS Macro Letters     Full-text available via subscription   (Followers: 20)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 25)
ACS Nano     Full-text available via subscription   (Followers: 379)
ACS Photonics     Full-text available via subscription   (Followers: 6)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 11)
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: 39)
Advanced Science Focus     Free  
Advances in Chemical Engineering and Science     Open Access   (Followers: 23)
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: 17)
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: 13)
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: 5)
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: 5)
AMB Express     Open Access  
Ambix     Hybrid Journal   (Followers: 2)
American Journal of Applied Sciences     Open Access   (Followers: 32)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 228)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 12)
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: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 19)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 283)
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: 5)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 11)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 12)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Antiviral Chemistry and Chemotherapy     Full-text available via subscription  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 13)
Applied Surface Science     Hybrid Journal   (Followers: 21)
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: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 289)
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: 6)
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: 2)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 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: 55)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 6)

        1 2 3 4 5 6 | Last

Journal Cover   Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [41 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  [1608 journals]
  • Masthead: (Adv. Funct. Mater. 16/2015)
    • PubDate: 2015-04-21T05:49:36.215913-05:
      DOI: 10.1002/adfm.201570109
  • Smart Hybridization of TiO2 Nanorods and Fe3O4 Nanoparticles with Pristine
           Graphene Nanosheets: Hierarchically Nanoengineered Ternary
           Heterostructures for High‐Rate Lithium Storage
    • Authors: Long Pan; Xiao‐Dong Zhu, Xu‐Ming Xie, Yi‐Tao Liu
      Abstract: Today, the ever‐increasing demand for large‐size power tools has provoked worldwide competition in developing lithium‐ion batteries having higher energy and power densities. In this context, advanced anode materials are being extensively pursued, among which TiO2 is particularly promising owing to its high safety, excellent cost and environmental performances, and high cycle stability. However, TiO2 is faced with two detrimental deficiencies, that is, extremely low theoretical capacity and conductivity. Herein, a smart hybridization strategy is proposed for the hierarchical co‐assembly of TiO2 nanorods and Fe3O4 nanoparticles on pristine graphene nanosheets, aiming to simultaneously address the capacity and conductivity deficiencies of TiO2 by coupling it with high‐capacity (Fe3O4) and high‐conductivity (pristine graphene) components. The resulting novel, multifunctional ternary heterostructures effectively integrate the intriguing functionalities of the three building blocks: TiO2 as the major active material can adequately retain such merits as high safety and cycle stability, Fe3O4 as the auxiliary active material can contribute extraordinarily high capacities, and pristine graphene as the conductive dopant can guarantee sufficient percolation pathways. Benefiting from a remarkable synergy, the ternary heterostructures deliver superior reversible capacities and rate capabilities, thus casting new light on developing next‐generation, high‐performance anode materials. A smart hybridization strategy is proposed for the hierarchical co‐assembly of TiO2 nanorods and Fe3O4 nanoparticles on pristine graphene nanosheets, aiming to simultaneously address the deficiencies of TiO2 by coupling it with high‐capacity (Fe3O4) and high‐conductivity (pristine graphene) components. Benefiting from a remarkable synergy, the resulting novel, multifunctional ternary heterostructures deliver superior reversible capacities and rate capabilities, thus casting new light on developing advanced LIB anode materials.
      PubDate: 2015-04-20T10:26:48.023815-05:
      DOI: 10.1002/adfm.201404348
  • Mechanical Switching of Nanoscale Multiferroic Phase Boundaries
    • Authors: Yong‐Jun Li; Jian‐Jun Wang, Jian‐Chao Ye, Xiao‐Xing Ke, Gao‐Yang Gou, Yan Wei, Fei Xue, Jing Wang, Chuan‐Shou Wang, Ren‐Ci Peng, Xu‐Liang Deng, Yong Yang, Xiao‐Bing Ren, Long‐Qing Chen, Ce‐Wen Nan, Jin‐Xing Zhang
      Abstract: Tuning the lattice degree of freedom in nanoscale functional crystals is critical to exploit the emerging functionalities such as piezoelectricity, shape‐memory effect, or piezomagnetism, which are attributed to the intrinsic lattice‐polar or lattice‐spin coupling. Here it is reported that a mechanical probe can be a dynamic tool to switch the ferroic orders at the nanoscale multiferroic phase boundaries in BiFeO3 with a phase mixture, where the material can be reversibly transformed between the “soft” tetragonal‐like and the “hard” rhombohedral‐like structures. The microscopic origin of the nonvolatile mechanical switching of the multiferroic phase boundaries, coupled with a reversible 180° rotation of the in‐plane ferroelectric polarization, is the nanoscale pressure‐induced elastic deformation and reconstruction of the spontaneous strain gradient across the multiferroic phase boundaries. The reversible control of the room‐temperature multiple ferroic orders using a pure mechanical stimulus may bring us a new pathway to achieve the potential energy conversion and sensing applications. A pure mechanical control of the nano­scale multiferroic phase boundaries is achieved in mixed‐phase BiFeO3, which is attributed to pressure‐induced elastic deformation and reconstruction of the spontaneous strain gradient across the boundaries. This demonstrates a new pathway to reversibly control the multiple ferroic orders such as ferroelectricity, ferroelasticity, and so on.
      PubDate: 2015-04-20T10:26:41.577556-05:
      DOI: 10.1002/adfm.201500600
  • Ag Nanowire Reinforced Highly Stretchable Conductive Fibers for Wearable
    • Authors: Seulah Lee; Sera Shin, Sanggeun Lee, Jungmok Seo, Jaehong Lee, Seungbae Son, Hyeon Jin Cho, Hassan Algadi, Saleh Al‐Sayari, Dae Eun Kim, Taeyoon Lee
      Abstract: Stretchable conductive fibers have received significant attention due to their possibility of being utilized in wearable and foldable electronics. Here, highly stretchable conductive fiber composed of silver nanowires (AgNWs) and silver nanoparticles (AgNPs) embedded in a styrene–butadiene–styrene (SBS) elastomeric matrix is fabricated. An AgNW‐embedded SBS fiber is fabricated by a simple wet spinning method. Then, the AgNPs are formed on both the surface and inner region of the AgNW‐embedded fiber via repeated cycles of silver precursor absorption and reduction processes. The AgNW‐embedded conductive fiber exhibits superior initial electrical conductivity (σ0 = 2450 S cm−1) and elongation at break (900% strain) due to the high weight percentage of the conductive fillers and the use of a highly stretchable SBS elastomer matrix. During the stretching, the embedded AgNWs act as conducting bridges between AgNPs, resulting in the preservation of electrical conductivity under high strain (the rate of conductivity degradation, σ/σ0 = 4.4% at 100% strain). The AgNW‐embedded conductive fibers show the strain‐sensing behavior with a broad range of applied tensile strain. The AgNW reinforced highly stretchable conductive fibers can be embedded into a smart glove for detecting sign language by integrating five composite fibers in the glove, which can successfully perceive human motions. Ag nanowire reinforced highly stretchable conductive fiber is developed using simple wet spinning method, which consists of silver nanowires and nanoparticles embedded in elastomeric polymer matrix. The composite fiber can preserve its electrical property under large strain and has superior strain‐sensing behavior. It can be utilized in the wearable smart glove for detecting human motions such as sign language.
      PubDate: 2015-04-20T10:26:01.954444-05:
      DOI: 10.1002/adfm.201500628
  • Nanoporous Silver Thin Films: Multifunctional Platforms for Influencing
           Chain Morphology and Optical Properties of Conjugated Polymers
    • Authors: Zeqing Shen; Deirdre M. O'Carroll
      Abstract: Disordered nanoporous silver (NPAg) thin films fabricated by a thermally assisted dewetting method are employed as a platform to influence chain alignment, morphology, and optical properties of three well‐known conjugated polymers. Grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) measurements show that the porous structure of the metal induces close π–π stacking of poly(3‐hexylthiophene) (P3HT) chains and extended, planar chain conformations of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (PFO) and poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,8‐diyl)] (F8BT). A greater degree of vertically‐oriented P3HT chains are found on NPAg compared with planar Ag. However, PFO and F8BT chain alignment is only affected when pore size is large. The optical properties of NPAg films are investigated by transmission and back‐scattering spectroscopies. Strong back‐scattering is observed for all NPAg morphologies, especially for NPAg with small pore sizes. Photoluminescence spectroscopy of conjugated polymer layers on NPAg showed pronounced emission enhancements (up to factors of 26) relative to layers on glass. The enhancements are attributed primarily to: 1) redistribution of conjugated polymer emission by Ag; 2) redirection of emission by polymer‐filled nanopores; and 3) local electromagnetic field effects. This work demonstrates the potential of NPAg‐thin films to influence molecular chain morphology and to improve light‐extraction in organic optoelectronic devices. Nanoporous metal films are multifunctional platforms that affect both the morphology and emission properties of conjugated polymer layer coatings. Nano­porous silver can reorient and/or planarize a fraction of conjugated polymer molecules in the pores. Photoluminescence emission enhancements of up to 26 are possible from conjugated polymer layers using nanoporous silver instead of bare glass substrates.
      PubDate: 2015-04-17T05:21:38.617487-05:
      DOI: 10.1002/adfm.201500456
  • Thin Films of Dendritic Anatase Titania Nanowires Enable Effective
           Hole‐Blocking and Efficient Light‐Harvesting for
           High‐Performance Mesoscopic Perovskite Solar Cells
    • Authors: Wu‐Qiang Wu; Fuzhi Huang, Dehong Chen, Yi‐Bing Cheng, Rachel A. Caruso
      Abstract: To achieve high‐performance perovskite solar cells, especially with mesoscopic cell structure, the design of the electron transport layer (ETL) is of paramount importance. Highly branched anatase TiO2 nanowires (ATNWs) with varied orientation are grown via a facile one‐step hydrothermal process on a transparent conducting oxide substrate. These films show good coverage with optimization obtained by controlling the hydrothermal reaction time. A homogeneous methyl­ammonium lead iodide (CH3NH3PbI3) perovskite thin film is deposited onto these ATNW films forming a bilayer architecture comprising of a CH3NH3PbI3 sensitized ATNW bottom layer and a CH3NH3PbI3 capping layer. The formation, grain size, and uniformity of the perovskite crystals strongly depend on the degree of surface coverage and the thickness of the ATNW film. Solar cells constructed using the optimized ATNW thin films (220 nm in thickness) yield power conversion efficiencies up to 14.2% with a short‐circuit photocurrent density of 20.32 mA cm−2, an open‐circuit photovoltage of 993 mV, and a fill factor of 0.70. The dendritic ETL and additional perovskite capping layer efficiently capture light and thus exhibit a superior light harvesting efficiency. The ATNW film is an effective hole‐blocking layer and efficient electron transport medium for excellent charge separation and collection within the cells. A facile solution‐based route to fabricate thin films of dendritic anatase TiO2nano­wires on TCO substrates is developed. Solar cells containing the perovskite‐infiltrated nanowire layer and uniform perovskite capping layer yield impressive power conversion efficiencies (>14%) due to efficient light harvesting and charge collection in the bilayer structure.
      PubDate: 2015-04-17T05:21:28.638183-05:
      DOI: 10.1002/adfm.201500616
  • Synergistic Interaction of Dyes and Semiconductor Quantum Dots for
           Advanced Cascade Cosensitized Solar Cells
    • Authors: Vicente M. Blas‐Ferrando; Javier Ortiz, Victoria González‐Pedro, Rafael S. Sánchez, Iván Mora‐Seró, Fernando Fernández‐Lázaro, Ángela Sastre‐Santos
      Abstract: A new procedure for the cosensitization with quantum dots (QDs) and dyes for sensitized solar cells is reported here. Cascade cosensitization of TiO2 electrodes is obtained by the sensitization with CdS QDs and zinc phthalocyanines (ZnPcs), in which ZnPcs containing a sulfur atom are specially designed to produce a cascade injection by direct attachment to QDs. This strategy causes a double synergetic interaction. This is the differentiating point of cascade cosensitization in comparison with other approaches in which dyes with conventional functionalization are anchored to TiO2 electrodes. Cosensitization produces a panchromatic response from the visible to near‐IR region already observed with other sensitization strategies. However, cascade cosensitization produces in addition a synergistic interaction between QDs and dye, that it is not merely limited to the complementary light absorption, but dye enhances the efficiency of QD sensitization acting as a passivating agent. The cascade cosensitization concept is demonstrated with using [Co(phen)3]3+/2+ redox electrolyte. The TiO2/CdS QD‐ZnPc/[Co(phen)3]3+/2+ sensitized solar cell shows a large improvement of short‐circuit photocurrent and open‐circuit voltage in comparison with samples just sensitized with QDs. The advent of such cosensitized QD‐ZnPc solar cells paves the way to extend the absorbance region of the promising QD‐based solar cells and the development of a new family of molecules designed for this purpose. The cascade co‐sensitization concept is demonstrated by the sensitization of TiO2 electrodes with CdS quantum dots (QDs) covalently linked to zinc phthalocyanines (ZnPcs) via a sulfur atom. The efficiency of co‐sensitized CdS QD‐SZnPc cells, using Co(phen)3]3+/[Co(phen)3]2+ as electrolyte, is 212% higher than that of a solar cell sensitized just with CdS QD.
      PubDate: 2015-04-17T05:21:17.997335-05:
      DOI: 10.1002/adfm.201500553
  • Stimuli‐Responsive Materials Based on Interpenetrating Polymer
           Liquid Crystal Hydrogels
    • Authors: Jelle E. Stumpel; Elda Renedo Gil, Anne B. Spoelstra, Cees W. M. Bastiaansen, Dirk J. Broer, Albertus P. H. J. Schenning
      Abstract: Stimuli‐responsive materials based on interpenetrating liquid crystal‐hydrogel polymer networks are fabricated. These materials consist of a cholesteric liquid crystalline network that reflects color and an interwoven poly(acrylic acid) network that provides a humidity and pH response. The volume change in the cross‐linked hydrogel polymer results in a dimensional alteration in the cholesteric network as well, which, in turn, leads to a color change yielding a dual‐responsive photonic material. Furthermore a patterned coating having responsive and static interpenetrating polymer network areas is produced that changes both its surface topography and color. Interpenetrating polymer networks which consist of cholesteric liquid crystals and hydrogels are prepared. These stimuli‐responsive materials change color depending on the relative humidity or pH. In addition, patterned dual‐responsive polymer films are created changing both topography and color.
      PubDate: 2015-04-17T05:21:13.963751-05:
      DOI: 10.1002/adfm.201500745
  • Clay Nanosheets in Skeletons of Controlled Phase Inversion Separators for
           Thermally Stable Li‐ion Batteries
    • Authors: Min Kim; Jung Kyu Kim, Jong Hyeok Park
      Abstract: Phase inversion is a powerful alternative process for preparing ultra‐thin separators for various secondary batteries. Unfortunately, separators prepared from phase inversion generally suffer from uneven pore size and pore size distribution, which frequently results in poor battery performance. Here, a straightforward route is demonstrated to solve the drawbacks of phase‐inversion‐based separators for Li‐ion batteries by means of directly incorporating 2D clay sheets in the skeleton of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) with multiscale pore generation from a simple one‐step solution coating method. Additionally generated pores by the inclusion of 2D nanosheets in PVdF‐HFP skeletons, combined with the multiscale pores (several micrometers + sub‐micrometers) originally generated by means of the controlled phase inversion, can generate additional ionic transport pathways, leading to Li‐ion battery performances better than those of commercialized polyethylene separators. Moreover, the addition of extremely low contents of 2D clay sheets in PVdF‐HFP separators allows thermally stable polymer separators to be realized. A straightforward route to solve the drawbacks of phase‐inversion‐based separators for Li‐ion batteries is demonstrated by means of directly incorporating 2D clay sheets in the skeleton of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) with multiscale pore generation from a simple one‐step solution coating method.
      PubDate: 2015-04-17T05:21:06.729574-05:
      DOI: 10.1002/adfm.201500758
  • Thionation Enhances the Electron Mobility of Perylene Diimide for High
           Performance n‐Channel Organic Field Effect Transistors
    • Authors: Andrew J. Tilley; Chang Guo, Mark B. Miltenburg, Tyler B. Schon, Han Yan, Yuning Li, Dwight S. Seferos
      Abstract: Perylene diimides (PDIs) are one of the most widely studied n‐type materials, showing great promise as electron acceptors in organic photovoltaic devices and as electron transport materials in n‐channel organic field effect transistors. Amongst the well‐established chemical modification strategies for increasing the electron mobility of PDI, substitution of the imide oxygen atoms with sulfur, known as thionation, has remained largely unexplored. In this work, it is demonstrated that thionation is a highly effective means of enhancing the electron mobility of a bis‐N‐alkylated PDI derivative. Successive oxygen–sulfur substitution increases the electron mobility such that the fully thionated derivative (S4) has an average mobility of 0.16 cm2 V−1 s−1. This is two orders of magnitude larger than the nonthionated parent compound (P), and is achieved by solution deposition and without thermal or solvent vapor annealing. A combination of atomic force microscopy and 2D wide angle X‐ray scattering experiments, together with theoretical modeling of charge transport efficiency, is used to explain the strong positive correlation observed between electron mobility and degree of thionation. This work establishes thionation as a highly effective means of enhancing the electron mobility of PDI, and provides motivation for the development of thionated PDI derivatives for organic electronics applications. The effect of oxygen–sulfur atomic substitution (thionation) on the electron mobility of perylene diimide is investigated. Electron mobility correlates with the extent of thionation, with the highest mobilities obtained in solution processed nonannealed devices. This work shows that thionation is a promising strategy for boosting the electron mobility of perylene diimide derivatives.
      PubDate: 2015-04-17T05:20:48.748237-05:
      DOI: 10.1002/adfm.201500837
  • In Situ X‐Ray Diffraction Studies on Structural Changes of a P2
           Layered Material during Electrochemical Desodiation/Sodiation
    • Authors: Young Hwa Jung; Ane S. Christiansen, Rune E. Johnsen, Poul Norby, Do Kyung Kim
      Abstract: Sodium layered oxides with mixed transition metals have received significant attention as positive electrode candidates for sodium‐ion batteries because of their high reversible capacity. The phase transformations of layered compounds during electrochemical reactions are a pivotal feature for understanding the relationship between layered structures and electrochemical properties. A combination of in situ diffraction and ex situ X‐ray absorption spectroscopy reveals the phase transition mechanism for the ternary transition metal system (Fe–Mn–Co) with P2 stacking. In situ synchrotron X‐ray diffraction using a capillary‐based microbattery cell shows a structural change from P2 to O2 in P2–Na0.7Fe0.4Mn0.4Co0.2O2 at the voltage plateau above 4.1 V on desodiation. The P2 structure is restored upon subsequent sodiation. The lattice parameter c in the O2 structure decreases significantly, resulting in a volumetric contraction of the lattice toward a fully charged state. Observations on the redox behavior of each transition metal in P2–Na0.7Fe0.4Mn0.4Co0.2O2 using X‐ray absorption spectroscopy indicate that all transition metals are involved in the reduction/oxidation process. The phase transition of a sodium layered material with P2 stacking during electro­chemical desodiation/sodiation is studied by in situ synchrotron X‐ray diffraction using a capillary‐based microcell. P2–Na0.7Fe0.4Mn0.4Co0.2O2 is transformed to an O2 structure in the voltage plateau at 4.1 V, and the O2 phase shows a rapid change in the c lattice until a fully charged state.
      PubDate: 2015-04-15T06:54:12.022128-05:
      DOI: 10.1002/adfm.201500469
  • One‐Step Self‐Assembly Fabrication of High Quality
           NixMg1‐xO Bowl‐Shaped Array Film and Its Enhanced Photocurrent
           by Mg,2+ Doping
    • Authors: Yan Zhao; Linfeng Hu, Shangpeng Gao, Meiyong Liao, Liwen Sang, Limin Wu
      Abstract: A series of high quality NixMg1‐xO bowl‐shaped array films are successfully prepared by a simple one‐step assembly of polystyrene colloidal spheres and metal oxide precursors at oil–water interface, and further used to fabricate nanodevices. The doping of Mg2+ can greatly enhance the current and spectrum responsivity of NiO film‐based nanodevice. The maximum Rλ value of these bowl‐shaped NixMg1‐xO film‐based devices measured in the study shows 4–5 orders of enhancement than the previously reported NixMg1‐xO film at equal doping. A series of high‐quality monolayer NixMg1‐xO (0.7 ≤ x ≤ 1) bowl‐shaped array films are successfully fabricated by a simple one‐step assembly of polystyrene colloidal spheres and metal oxide precursors at oil–water interface. The NixMg1‐xO film‐based device shows significantly enhanced photocurrent due to the doping of Mg2+ ions and higher optoelectronic properties than the previously reported counterparts.
      PubDate: 2015-04-15T06:53:58.279349-05:
      DOI: 10.1002/adfm.201500071
  • Towards a Better Prediction of Cell Settling on Nanostructure
           Arrays—Simple Means to Complicated Ends
    • Authors: Nina Buch‐Månson; Sara Bonde, Jessica Bolinsson, Trine Berthing, Jesper Nygård, Karen L. Martinez
      Abstract: Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial. Cell settling on nanostructure (NS) arrays is modeled and the effect of geometrical and cell‐related parameters is systematically evaluated. It is found that cell settling is highly dependent on both single‐NS dimensions and NS density, and predictive tools are developed for any NS array or cell type, thus allowing a rational design of future NS arrays for biological applications.
      PubDate: 2015-04-15T06:53:36.569686-05:
      DOI: 10.1002/adfm.201500399
  • Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized
           with Single‐Stranded DNA
    • Authors: Kazi M. Alam; Sandipan Pramanik
      Abstract: High spin polarization materials or spin filters are key components in spintronics, a niche subfield of electronics where carrier spins play a functional role. Carrier transmission through these materials is “spin selective,” that is, these materials are able to discriminate between “up” and “down” spins. Common spin filters include transition metal ferromagnets and their alloys, with typical spin selectivity (or, polarization) of ≈50% or less. Here carrier transport is considered in an archetypical one‐dimensional molecular hybrid in which a single wall carbon nanotube (SWCNT) is wrapped around by single stranded deoxyribonucleic acid (ssDNA). By magnetoresistance measurements, this system can act as a spin filter with maximum spin polarization approaching ≈74% at low temperatures, significantly larger than transition metals under comparable conditions. Inversion asymmetric helicoidal potential of the charged ssDNA backbone induces a Rashba spin‐orbit interaction in the SWCNT channel and polarizes carrier spins. The results are consistent with recent theoretical work that predicted spin dependent conductance in ssDNA‐SWCNT hybrid. Ability to generate highly spin polarized carriers using molecular functionalization can lead to magnet‐less and contact‐less spintronic devices in the future. This can eliminate the conductivity mismatch problem and open new directions for research in organic spintronics. Spin filtering through single‐wall carbon nanotubes (SWCNTs) wrapped with single‐stranded DNA is demonstrated. Significant spin polarization, larger than typical transition metal ferromagnets, is observed at low temperatures. The helical wrapping of the ssDNA induces an inversion asymmetric electric field in the SWCNT channel, which results in a Rashba‐type spin‐orbit interaction and polarizes carrier spins.
      PubDate: 2015-04-15T06:53:30.738285-05:
      DOI: 10.1002/adfm.201500494
  • Light‐Emitting Paper
    • Authors: Amir Asadpoordarvish; Andreas Sandström, Christian Larsen, Roger Bollström, Martti Toivakka, Ronald Österbacka, Ludvig Edman
      Abstract: A solution‐based fabrication of flexible and light‐weight light‐emitting devices on paper substrates is reported. Two different types of paper substrates are coated with a surface‐emitting light‐emitting electrochemical cell (LEC) device: a multilayer‐coated specialty paper with an intermediate surface roughness of 0.4 μm and a low‐end and low‐cost copy paper with a large surface roughness of 5 μm. The entire device fabrication is executed using a handheld airbrush, and it is notable that all of the constituent layers are deposited from solution under ambient air. The top‐emitting paper‐LECs are highly flexible, and display a uniform light emission with a luminance of 200 cd m−2 at a current conversion efficacy of 1.4 cd A−1. A surface‐emitting light‐emitting electrochemical cell (LEC) is fabricated on a conventional low‐cost paper substrate. It is notable that all of the device layers, including the cathode, active material, and anode, are deposited from solution under ambient air using a handheld airbrush. The main merits of the paper‐LEC are the highly flexible and robust form factor, the low weight, and the cost‐efficient and fault‐tolerant fabrication.
      PubDate: 2015-04-15T06:53:25.112102-05:
      DOI: 10.1002/adfm.201500528
  • Flexible, Highly Graphitized Carbon Aerogels Based on Bacterial
           Cellulose/Lignin: Catalyst‐Free Synthesis and its Application in
           Energy Storage Devices
    • Authors: Xuezhu Xu; Jian Zhou, D. H. Nagaraju, Long Jiang, Val R. Marinov, Gilles Lubineau, Husam N. Alshareef, Myungkeun Oh
      Abstract: Currently, most carbon aerogels are based on carbon nanotubes (CNTs) or graphene, which are produced through a catalyst‐assisted chemical vapor deposition method. Biomass based organic aerogels and carbon aerogels, featuring low cost, high scalability, and small environmental footprint, represent an important new research direction in (carbon) aerogel development. Cellulose and lignin are the two most abundant natural polymers in the world, and the aerogels based on them are very promising. Classic silicon aerogels and available organic resorcinol–formaldehyde (RF) or lignin–resorcinol–formaldehyde (LRF) aerogels are brittle and fragile; toughening of the aerogels is highly desired to expand their applications. This study reports the first attempt to toughen the intrinsically brittle LRF aerogel and carbon aerogel using bacterial cellulose. The facile process is catalyst‐free and cost‐effective. The toughened carbon aerogels, consisting of blackberry‐like, core–shell structured, and highly graphitized carbon nanofibers, are able to undergo at least 20% reversible compressive deformation. Due to their unique nanostructure and large mesopore population, the carbon materials exhibit an areal capacitance higher than most of the reported values in the literature. This property makes them suitable candidates for flexible solid‐state energy storage devices. Besides energy storage, the conductive interconnected nanoporous structure can also find applications in oil/water separation, catalyst supports, sensors, and so forth. Intrinsically brittle lignin–resorcinol–formaldehyde carbon aerogels undergo large reversible deformation after bacterial cellulose toughening and exhibit exceptional areal capacitance.
      PubDate: 2015-04-15T06:52:56.441181-05:
      DOI: 10.1002/adfm.201500538
  • Integrative Self‐Assembly of Graphene Quantum Dots and Biopolymers
           into a Versatile Biosensing Toolkit
    • Authors: Yiyang Lin; Robert Chapman, Molly M. Stevens
      Abstract: Hybrid self‐assembly has become a reliable approach to synthesize soft materials with multiple levels of structural complexity and synergistic functionality. In this work, photoluminescent graphene quantum dots (GQDs, 2–5 nm) are used for the first time as molecule‐like building blocks to construct self‐assembled hybrid materials for label‐free biosensors. Ionic self‐assembly of disc‐shaped GQDs and charged biopolymers is found to generate a series of hierarchical structures that exhibit aggregation‐induced fluorescence quenching of the GQDs and change the protein/polypeptide secondary structure. The integration of GQDs and biopolymers via self‐assembly offers a flexible toolkit for the design of label‐free biosensors in which the GQDs serve as a fluorescent probe and the biopolymers provide biological function. The versatility of this approach is demonstrated in the detection of glycosaminoglycans (GAGs), pH, and proteases using three strategies: 1) competitive binding of GAGs to biopolymers, 2) pH‐responsive structural changes of polypeptides, and 3) enzymatic hydrolysis of the protein backbone, respectively. It is anticipated that the integrative self‐assembly of biomolecules and GQDs will open up new avenues for the design of multifunctional biomaterials with combined optoelectronic properties and biological applications. Ionic self‐assembly of disc‐shaped graphene quantum dots (GQDs) and biopoly­mers are employed to design versatile biosensors, in which the GQDs serve as photoluminescent probes and the biopoly­mers confer biological activity. Three key strategies are proposed to design label‐free sensors of pH, glycosaminoglycans, and protease.
      PubDate: 2015-04-15T06:52:47.623314-05:
      DOI: 10.1002/adfm.201500624
  • Micropatterned P(VDF‐TrFE) Film‐Based Piezoelectric
           Nanogenerators for Highly Sensitive Self‐Powered Pressure Sensors
    • Authors: Ju‐Hyuck Lee; Hong‐Joon Yoon, Tae Yun Kim, Manoj Kumar Gupta, Jeong Hwan Lee, Wanchul Seung, Hanjun Ryu, Sang‐Woo Kim
      Abstract: Here micropatterned poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) films‐based piezoelectric nanogenerators (PNGs) with high power‐generating performance for highly sensitive self‐powered pressure sensors are demonstrated. The microstructured P(VDF‐TrFE)‐based PNGs reveal nearly five times larger power output compared to a flat film‐based PNG. The micropatterning of P(VDF‐TrFE) polymer makes itself ultrasensitive in response to mechanical deformation. The application is demonstrated successfully as self‐powered pressure sensors in which mechanical energy comes from water droplet and wind. The mechanism of the high performance is intensively discussed and illustrated in terms of strain developed in the flat and micropatterned P(VDF‐TrFE) films. The impact derived from the patterning on the output performance is studied in term of effective pressure using COMSOL multiphysics software. Micropatterned poly­(vinylidenefluoride‐co‐trifluoroethylene) P(VDF‐TrFE) film‐based piezoelectric nanogenerators with high power‐generating performance for highly sensitive self‐powered pressure sensors are successfully demonstrated. The microstructured P(VDF‐TrFE)‐based PNGs have nearly five times larger power output compared to the flat film‐based PNG. The microstructured nanogenerator efficiently converts external force into electric output with superior mechanical durability under various circumstances such as rain drops and wind blow.
      PubDate: 2015-04-15T06:52:39.868973-05:
      DOI: 10.1002/adfm.201500856
  • A Versatile Buffer Layer for Polymer Solar Cells: Rendering Surface
           Potential by Regulating Dipole
    • Authors: Wei Zhong; Lie Chen, Shuqin Xiao, Liqiang Huang, Yiwang Chen
      Abstract: Spin‐coated film of poly(vinylidenefluoride‐hexafluoropropylene) (P(VDF‐HFP)) acts as a cathode/anode buffer layer in polymer solar cells (PSCs) with conventional/inverted device structures. Such devices show optimized performances comparable with the controlled device, making P(VDF‐HFP) a good substitute for LiF/MoO3 as a cathode/anode buffer layer. Ultraviolet photoelectron spectroscopy (UPS) and Kelvin force microscope (KFM) measurements show that increased surface potential of active layers improves cathode contact. In piezoresponse force microscopy (PFM) measurement, P(VDF‐HFP) responds to applied bias in phase curve, showing tunable dipole. This tunable dipole renders surface potential under applied bias. As a result, open‐circuit voltage of devices alters instantly with poling voltage. Moreover, positive poling of P(VDF‐HFP) together with simultaneous oxidation of Ag gradually improves performance of inverted structure device. Integer charge transfer (ICT) model elucidates improved electrode contacts by dipole tuning, varying surface potential and vacuum level shift. Understanding the function of dipole makes P(VDF‐HFP) a promising and versatile buffer layer for PSCs. Poly(vinylidenefluoride‐hexafluoropropylene) (P(VDF‐HFP)) is demonstrated as an efficient buffer layer in cathode/anode interface of conventional/inverted solar cells, with tunable dipole rendering surface potential of active layers. Integer charge transfer (ICT) model is employed to unveil the effect of surface potential on electrode contact and device performance. Understanding the function of dipole makes P(VDF‐HFP) a versatile buffer layer for PSCs.
      PubDate: 2015-04-14T13:17:16.821086-05:
      DOI: 10.1002/adfm.201500500
  • Donor‐Induced Performance Tuning of Amorphous SrTiO3 Memristive
           Nanodevices: Multistate Resistive Switching and Mechanical Tunability
    • Authors: Hussein Nili; Sumeet Walia, Ahmad Esmaielzadeh Kandjani, Rajesh Ramanathan, Philipp Gutruf, Taimur Ahmed, Sivacarendran Balendhran, Vipul Bansal, Dmitri B. Strukov, Omid Kavehei, Madhu Bhaskaran, Sharath Sriram
      Abstract: Metal–oxide valence‐change memristive devices are the key contenders for the development of multilevel nonvolatile analog memories and neuromorphic computing architectures. Reliable low energy performance and tunability of nonlinear resistive switching dynamics are essential to streamline the high‐density circuit level integration of these devices. Here, manipulation of room temperature‐synthesized defect chemistry is employed to enhance and tune the switching characteristics of high‐performance amorphous SrTiO3 (a‐STO) memristors. Substitutional donor (Nb) doping with low concentrations in the a‐STO oxide structure allows extensive improvements in energy requirements, stability, and controllability of the memristive performance, as well as field‐dependent multistate resistive switching. Evidence is presented that room temperature donor doping results in a modified insulator oxide where dislocation sites act as charge carrier modulators for low energy and multilevel operation. Finally, the performance of donor‐doped a‐STO‐based memristive nanodevices is showcased, with the possibility of mechanical modulation of the nonlinear memristive characteristics of these devices demonstrated. These results highlight the potential of donor‐doped a‐STO nanodevices for high‐density integration as analog memories and multifunctional alternative logic elements. The origins of multifilamentary resistive switching in high‐performance a‐STO memristive devices are investigated to realize donor‐doped devices with improved switching characteristics, capable of stable field‐dependent multistate switching operation. The nonlinear switching characteristics of the donor‐doped a‐STO nanoswitches can be mechanically modulation via force‐controlled nanocontact experiments.
      PubDate: 2015-04-14T05:20:56.781198-05:
      DOI: 10.1002/adfm.201501019
  • High‐Performance Thermally Stable Organic Phototransistors Based on
           PSeTPTI/PC61BM for Visible and Ultraviolet Photodetection
    • Authors: Zhe Qi; Jiamin Cao, Hui Li, Liming Ding, Jizheng Wang
      Abstract: Phototransistors are three‐terminal photodetectors which usually have higher photosensitivity than photodiodes due to the presence of gate electrode. In this report, organic phototransistors (OPTs) based on a donor material, namely, poly{2,5‐selenophene‐alt‐2,8‐(4,10‐bis(2‐hexyldecyl))thieno[2′,3′:5,6]­pyrido[3,4‐g]thieno[3,2‐c]isoquinoline‐5,11(4H,10H)‐dione} (PSeTPTI), are fabricated and intensively studied. As unipolar p‐type organic semiconductor usually has plenty of electron traps in the bulk to impede electron transporting, most of photogenerated electrons will fill the traps in PSeTPTI and this process can prolong the response time. By introducing [6,6]‐phenyl C61 butyric acid methyl ester on top, the p–n heterojunction can produce most of the photocurrent and eliminates the influence from the process of trapping electrons. This mechanism improves the photoresponsivity and response speed. Since ultraviolet (UV) detection is very important in some fields including military, aerospace, and biology, the OPTs are characterized under UV illumination besides the visible light and they present high sensitivity. Furthermore, organic semiconductors often have bad stability in harsh conditions and meanwhile some devices need to work in these environments. At high temperature even up to 200 °C, our OPTs can work normally and show very high stability, indicating the potential of the devices in applications of high‐temperature environments. A donor material, PSeTPTI, is used for fabricating organic phototransistors. Through introducing the heterojunction by depositing PC61BM on top of PSeTPTI, the performance is improved. The photodetectors can detect not only visible light but also ultraviolet. More attractively, the devices can work normally at high temperature, even up to 200 °C.
      PubDate: 2015-04-13T07:17:21.851447-05:
      DOI: 10.1002/adfm.201500525
  • Ultrahigh‐Gain Single SnO2 Microrod Photoconductor on Flexible
           Substrate with Fast Recovery Speed
    • Authors: Kewei Liu; Makoto Sakurai, Masakazu Aono, Dezhen Shen
      Abstract: Owing to the special properties and wide applications, UV photodetectors based on wide‐band‐gap semiconductors have drawn an increasing interest during the last two decades. However, practical UV photodetectors are required two contradictory performances: high internal gain and fast recovery speed, because high internal gain is achieved by long life time of photoexcited carriers and fast recovery needs their fast decay. Their slow decay in wide‐band‐gap semiconductors has been known as a persistent photoconductivity (PPC) problem and hinders applications. In this paper, a good solution to the above contradictory problem is demonstrated on a single SnO2 microrod photoconductor, which shows both high photoconductive gain (≈1.5 × 109) and quick recovery speed (1 d), which is induced by a novel “reset” process: bending and straightening the microrod and subsequently applying a voltage pulse. This result suggests that SnO2 microrods have potential applications in high‐performance UV photodetecting devices. A single SnO2 microrod photoconductor is demonstrated on a flexible substrate with the photoconductive gain as high as ≈1.5 × 109. More interestingly, the recovery time can be reduced from more than 1 d to less than 1 s by a novel “reset” process: bending and straightening the microrod and subsequently applying a voltage pulse.
      PubDate: 2015-04-13T07:17:15.066432-05:
      DOI: 10.1002/adfm.201500231
  • Controllable Generation of Nitric Oxide by
           Near‐Infrared‐Sensitized Upconversion Nanoparticles for Tumor
    • Authors: Xiao Zhang; Gan Tian, Wenyan Yin, Liming Wang, Xiaopeng Zheng, Liang Yan, Jinxia Li, Haoran Su, Chunying Chen, Zhanjun Gu, Yuliang Zhao
      Abstract: NaYbF4:Tm@NaYF4:Yb/Er upconversion nanoparticles are synthesized and then integrated with light‐sensitive nitric oxide (NO) donors (Roussin's black salt) to construct a novel near‐infrared (NIR)‐triggered on‐demand NO delivery platform. This nanocompound can absorb 980 nm NIR photons, convert them into higher energy photons and then transfer the energy to the NO donors, resulting in an efficient release of NO. By manipulating the output power of the 980‐nm NIR light, NO‐concentration‐dependent biological effects for cancer therapy can be fine‐tuned, which is investigated and confirmed in vitro. High concentrations of NO can directly kill cancer cells and low concentrations of NO can act as a potent P‐glycoprotein (P‐gp) modulator to overcome multi‐drug resistance (MDR) if combined with chemotherapy. A new near‐infrared triggered on‐demand nitric oxide (NO) delivery nanoplatform is constructed by incorporating upconversion nanoparticles with light‐sensitive NO donors, Roussin's black salt (RBS). By regulating the output power of the laser, the on‐demand release of NO is realized and results in multi‐functionality of NO for tumor therapy.
      PubDate: 2015-04-11T13:33:12.15763-05:0
      DOI: 10.1002/adfm.201404402
  • Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent
           Vapor Annealing Using Mixtures of Selective Solvents
    • Authors: Michelle A. Chavis; Detlef‐M. Smilgies, Ulrich B. Wiesner, Christopher K. Ober
      Abstract: Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, solvent vapor annealing in supported thin films of poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) [PHEMA‐b‐PMMA] by means of grazing incidence small angle X‐ray scattering (GISAXS) is investigated. A spin‐coated thin film of a lamellar block copolymer is solvent vapor annealed to induce microphase separation and improve the long‐range order of the self‐assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents, which are chosen to be preferential for each block, enables selective formation of ordered lamellae, gyroid, hexagonal, or spherical morphologies from a single‐block copolymer with a fixed volume fraction. The selected microstructure is then kinetically trapped in the dry film by rapid drying. This paper describes what is thought to be the first reported case where in situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram. An approach to achieve selective, controlled, morphological ordering from a single, fixed volume fraction, poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) copolymer is presented. By taking advantage of preferential solvent annealing, it is possible to dial in to a specific block copolymer microstructure that can then be kinetically trapped in the dry film.
      PubDate: 2015-04-11T13:33:05.115192-05:
      DOI: 10.1002/adfm.201404053
  • Citrate Effects on Amorphous Calcium Carbonate (ACC) Structure, Stability,
           and Crystallization
    • Authors: Dominique J. Tobler; Juan Diego Rodriguez‐Blanco, Knud Dideriksen, Nicolas Bovet, Karina K. Sand, Susan L. S. Stipp
      Abstract: Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid–mineral interactions, both in nature and for industrial processes. In this study, ACC formation and its crystallization are monitored in real time as a function of citrate (CIT) concentration in solution. Additionally, synchrotron radiation pair distribution function analyses combined with solid‐state, spectroscopic, and microscopic techniques are used to determine the effect of CIT on ACC structure, composition, and size. Results show an increase in ACC lifetime coupled with an increase in CIT uptake by ACC and slight changes in ACC atomic structure with an increase in CIT concentration. ACC does not form at concentrations ≥ 75% CIT/Ca and vaterite is absent in all cases where CIT is present. These findings can be explained by CIT binding with Ca ions, thereby forming Ca–CIT complexes in solution and decreasing ACC and calcite saturation levels. The formation of CIT‐bearing ACC with calcitic structure and the absence of vaterite formation suggest that these solution complexes form a calcite‐type atomic arrangement while CIT probably also acts as a growth inhibitor. The addition of citrate to solutions supersaturated with respect to amorphous calcium carbonate (ACC) leads to more stable ACC with modified structure and composition and direct crystallization to calcite via a spherulitic growth mechanism. At citrate/Ca ratio ≥ 0.75, ACC formation is inhibited and calcite spherulites form directly from solution.
      PubDate: 2015-04-11T13:32:58.892882-05:
      DOI: 10.1002/adfm.201500400
  • Phosphorescent Cationic Au4Ag2 Alkynyl Cluster Complexes for Efficient
           Solution‐Processed Organic Light‐Emitting Diodes
    • Authors: Liang‐Jin Xu; Jin‐Yun Wang, Xiao‐Feng Zhu, Xian‐Chong Zeng, Zhong‐Ning Chen
      Abstract: Cationic Au4Ag2 heterohexanuclear aromatic acetylides cluster complexes supported by bis(2‐diphenylphosphinoethyl)phenylphosphine (dpep) are prepared. The Au4Ag2 cluster structure originating from the combination of one anionic [Au(CCR)2]− with one cationic [Au3Ag2(dpep)2(CCR)2]3+ through the formation of Ag−acetylide η2‐bonds is highly stabilized by Au–Ag and Au–Au contacts. The Au4Ag2 alkynyl cluster complexes are moderately phosphorescent in the fluid CH2Cl2 solution, but exhibit highly intense phosphorescent emission in solid state and film. As revealed by theoretical computational studies, the phosphorescence is ascribable to significant 3[π (aromatic acetylide) → s/p (Au)] 3LMCT parentage with a noticeable Au4Ag2 cluster centered 3[d → s/p] triplet state. Taking advantage of mCP and OXD‐7 as a mixed host with 20 wt% dopant of phosphorescent Au4Ag2 cluster complex in the emitting layer, solution‐processed organic light‐emitting diodes (OLEDs) exhibit highly efficient electrophosphorescence with the maximum current, power, and external quantum efficiencies of 24.1 cd A−1, 11.6 lm W−1, and 7.0%, respectively. Introducing copper(I) thiocyanate (CuSCN) as a hole‐transporting layer onto the PEDOT:PSS hole‐injecting layer through the orthogonal solution process induces an obvious improvement of the device performance with lower turn‐on voltage and higher electroluminescent efficiency. Cationic Au4Ag2 aromatic alkynyl cluster complexes supported by bis(2‐diphenylphosphinoethyl)phenylphosphine‑ (dpep) are highly phosphorescent in solid states and films. Solution‐processed OLEDs based on Au4Ag2 complexes exhibit highly efficient electroluminescence.
      PubDate: 2015-04-11T13:32:53.87566-05:0
      DOI: 10.1002/adfm.201500060
  • Bioinspired Reversibly Cross‐linked Hydrogels Comprising Polypeptide
           Micelles Exhibit Enhanced Mechanical Properties
    • Authors: Ali Ghoorchian; Joseph R. Simon, Bhuvnesh Bharti, Wei Han, Xuanhe Zhao, Ashutosh Chilkoti, Gabriel P. López
      Abstract: Noncovalently cross‐linked networks are attractive hydrogel platforms because of their facile fabrication, dynamic behavior, and biocompatibility. The majority of noncovalently cross‐linked hydrogels, however, exhibits poor mechanical properties, which significantly limit their utility in load bearing applications. To address this limitation, hydrogels are presented composed of micelles created from genetically engineered, amphiphilic, elastin‐like polypeptides that contain a relatively large hydrophobic block and a hydrophilic terminus that can be cross‐linked through metal ion coordination. To create the hydrogels, heat is firstly used to trigger the self‐assembly of the polypeptides into monodisperse micelles that display transition metal coordination motifs on their coronae, and subsequently cross‐link the micelles by adding zinc ions. These hydrogels exhibit hierarchical structure, are stable over a large temperature range, and exhibit tunable stiffness, self‐healing, and fatigue resistance. Gels with polypeptide concentration of 10%, w/v, and higher show storage moduli of ≈1 MPa from frequency sweep tests and exhibit self‐healing within minutes. These reversibly cross‐linked, hierarchical hydrogels with enhanced mechanical properties have potential utility in a variety of biomedical applications. Hydrogels with enhanced mechanical properties are made by cross‐linking recombinant polypeptide micelles through coordination chemistry. The micelles are created from a genetically engineered, amphiphilic, elastin‐like polypeptide, which contains a hydrophilic block that is terminated with a bioinspired metal‐ion binding domain. Heating polypeptide chains in solution triggers self‐assembly of the biopolymers into monodisperse micelles, which are then reversibly cross‐linked into self‐healing gels with very high modulus.
      PubDate: 2015-04-11T13:32:28.262803-05:
      DOI: 10.1002/adfm.201500699
  • A Three Component Self‐Assembled Epitaxial Nanocomposite Thin Film
    • Authors: Dong Hun Kim; Xue Yin Sun, Nicolas M. Aimon, Jae Jin Kim, Michael J. Campion, Harry L. Tuller, Lior Kornblum, Fred J. Walker, Charles H. Ahn, Caroline A. Ross
      Abstract: A self‐assembled three phase epitaxial nanocomposite film is grown consisting of ≈3 nm diameter fcc metallic Cu nanorods within square prismatic SrO rocksalt nanopillars in a Sr(Ti,Cu)O3‐δ perovskite matrix. Each phase has an epitaxial relation to the others. The core–shell‐matrix structures are grown on SrTiO3 substrates and can also be integrated onto Si using a thin SrTiO3 buffer. The structure is made by pulsed laser deposition in vacuum from a SrTi0.75Cu0.25O3 target, and formed as a result of the limited solubility of Cu in the perovskite matrix. Wet etching removes the 3 nm diameter Cu nanowires leaving porous SrO pillars. The three‐phase nanocomposite film is used as a substrate for growing a second epitaxial nanocomposite consisting of CoFe2O4 spinel pillars in a BiFeO3 perovskite matrix, producing dramatic effects on the structure and magnetic properties of the CoFe2O4. This three‐phase vertical nanocomposite provides a complement to the well‐known two‐phase nanocomposites, and may offer a combination of properties of three different materials as well as additional avenues for strain‐mediated coupling within a single film. nc‐STCu films are grown in vacuum on Nb‐doped (001) STO substrate after etching in ammonium hydroxide for 3 h. Metallic copper rods with ≈3 nm diameter grow in the center of the SrO nanorods in a perovskite matrix, and etching of the Cu by ammonium hydroxide creates uniform size nanopores.
      PubDate: 2015-04-10T05:04:58.756954-05:
      DOI: 10.1002/adfm.201500332
  • Programmable Persistent Interfacial Metallic State Induced by Frozen Ions
           in Inorganic–Glass Solid Electrolyte
    • Authors: Kouji Taniguchi; Takayuki Fukamichi, Kenji Itaka, Hidenori Takagi
      Abstract: Electric field control of charge carrier density through dielectric layers has long been a key technology in the semiconductor industry and condensed‐matter physics. The new carrier‐doping method by the electric double layers (EDLs) opens up the route to access clean carrier doping with high carrier density, but this method is not practical for a switching device due to its slow response to the electric field. However, if this slow response could be stopped at room temperature as an extreme case, the EDL method can become the practical means for materials design, which produces a persistent carrier‐doped state without impurity introduction or continuous supply of external electric fields. Here, it is demonstrated that the thermally programmable persistent interfacial metallic state can be realized around room temperature by all‐solid heterointerface devices using an inorganic–glass solid electrolyte as a gate insulator. The proposed device, in this study, could pave the way for designing a new category of a highly carrier‐doped semiconductor. A programmable interfacial persistent metallic state is realized up to near room temperature at the interface between the polarized solid glass–electrolyte and SrTiO3. The electric double layer (EDL) is formed from cations and electrons in the all‐solid heterointerface devices. By freezing motion of cations within the EDL, the persistent metallic state is stabilized even after removing the external electric field up to near room temperature.
      PubDate: 2015-04-10T05:03:45.902067-05:
      DOI: 10.1002/adfm.201403742
  • Poly(N‐isopropylacrylamide)‐Clay Nanocomposite Hydrogels with
           Responsive Bending Property as Temperature‐Controlled Manipulators
    • Authors: Chen Yao; Zhuang Liu, Chao Yang, Wei Wang, Xiao‐Jie Ju, Rui Xie, Liang‐Yin Chu
      Abstract: Novel poly(N‐isopropylacrylamide)‐clay (PNIPAM‐clay) nanocomposite (NC) hydrogels with both excellent responsive bending and elastic properties are developed as temperature‐controlled manipulators. The PNIPAM‐clay NC structure provides the hydrogel with excellent mechanical property, and the thermoresponsive bending property of the PNIPAM‐clay NC hydrogel is achieved by designing an asymmetrical distribution of nanoclays across the hydrogel thickness. The hydrogel is simply fabricated by a two‐step photo polymerization. The thermoresponsive bending property of the PNIPAM‐clay NC hydrogel is resulted from the unequal forces generated by the thermoinduced asynchronous shrinkage of hydrogel layers with different clay contents. The thermoresponsive bending direction and degree of the PNIPAM‐clay NC hydrogel can be adjusted by controlling the thickness ratio of the hydrogel layers with different clay contents. The prepared PNIPAM‐clay NC hydrogels exhibit rapid, reversible, and repeatable thermoresponsive bending/unbending characteristics upon heating and cooling. The proposed PNIPAM‐clay NC hydrogels with excellent responsive bending property are demonstrated as temperature‐controlled manipulators for various applications including encapsulation, capture, and transportation of targeted objects. They are highly attractive material candidates for stimuli‐responsive “smart” soft robots in myriad fields such as manipulators, grippers, and cantilever sensors. Poly(N‐isopropylacrylamide)‐clay nanocomposite hydrogels with responsive bending property are successfully developed as temperature‐controlled manipulators by designing an asymmetrical distribution of nanoclays across the hydrogel thickness. The hydrogels show rapid, reversible, and repeatable thermoresponsive bending characteristics, and are demonstrated as temperature‐controlled soft manipulators for applications of encapsulating, grapping, and transporting target objects in aqueous environments.
      PubDate: 2015-04-09T06:39:58.617687-05:
      DOI: 10.1002/adfm.201500420
  • Reversible and Rapid Laser Actuation of Liquid Crystalline Elastomer
           Micropillars with Inclusion of Gold Nanoparticles
    • Authors: Xiyang Liu; Renbo Wei, Phong Tran Hoang, Xiaogong Wang, Tao Liu, Patrick Keller
      Abstract: It is highly desirable for liquid crystal elastomer (LCE) based microactuators to activate and actuate in a highly controlled fashion without perturbing the surrounding environment. To reach this goal, in this study, a novel experimental protocol is developed to successfully incorporate gold nanosphere (AuNS) and gold nanorod (AuNR) into polyacrylate based LCE elastomer to fabricate LCE/AuNR and LCE/AuNS micropillars or microactuators. The effect of gold nanoparticle inclusion has been studied by spectroscopy (UV–vis‐near‐infrared), microscopy (transmission electron microscopy), thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and x‐ray scattering (wide‐angle x‐ray scattering and small‐angle x‐ray scattering). Finite element analysis is performed to examine the feasibility of utilizing the photothermal effect of AuNR/AuNS to enable photothermal actuation of LCE/AuNR and LCE/AuNS micropillars. The comparative experimental studies on the thermal and photothermal actuation behavior of the LCE, LCE/AuNS, and LCE/AuNR micropillar suggested that AuNR is an excellent candidate for developing high‐performance LCE actuators with photothermal actuation capability. With inclusion of less than 1 wt% of AuNR, the very high maximum actuation strain (30%) and rapid response (a few seconds) have been achieved in LCE/AuNR micropillar actuators under 635 nm laser irradiation. By incorporating of gold nanoparticles (AuNPs) into polyacrylate‐based liquid crystal elastomer (LCE), LCE/AuNP micropillars capable of both thermal and photothermal actuation are fabricated and characterized. Upon red laser (635 nm) irradiation, the LCE/AuNR micropillar shows rapid (a few seconds), large amplitude (≈30% strain), and reversible actuation without perturbing the surrounding environment.
      PubDate: 2015-04-09T06:38:18.107881-05:
      DOI: 10.1002/adfm.201500443
  • Harvesting Lost Photons: Plasmon and Upconversion Enhanced Broadband
           Photocatalytic Activity in Core@Shell Microspheres Based on
           Lanthanide‐Doped NaYF4, TiO2, and Au
    • Authors: Zhenhe Xu; Marta Quintanilla, Fiorenzo Vetrone, Alexander O. Govorov, Mohamed Chaker, Dongling Ma
      Abstract: Efficiently harvesting solar energy for photocatalysis remains very challenging. Rational design of architectures by combining nanocomponents of radically different properties, for example, plasmonic, upconversion, and photocatalytic properties, offers a promising route to improve solar energy utilization. Herein, the synthesis of novel, plasmonic Au nanoparticle decorated NaYF4:Yb3+, Er3+, Tm3+‐core@porous‐TiO2‐shell microspheres is reported. They exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity, significantly better than the benchmark P25 TiO2. The enhanced activity is attributed to synergistic effects from nanocomponents arranged into the nanostructured architecture in such a way that favors the efficient charge/energy transfer among nanocomponents and largely reduced charge recombination. Optical and energy‐transfer properties are modeled theoretically to support our interpretations of catalytic mechanisms. In addition to yielding novel materials and interesting properties, the current work provides physical insights that can contribute to the future development of plasmon‐enhanced broadband catalysts. Au nanoparticle decorated NaYF4:Yb3+, Er3+, Tm3+@TiO2 core@porous‐shell microspheres are successfully prepared and exhibit excellent, stable, and broadband photocatalytic activity from UV up to near‐infrared by rationally applying plasmon and upconversion concepts into photocatalysis.
      PubDate: 2015-04-09T06:38:11.995125-05:
      DOI: 10.1002/adfm.201500810
  • Reduction‐Sensitive Dextran Nanogels Aimed for Intracellular
           Delivery of Antigens
    • Authors: Dandan Li; Neda Kordalivand, Marieke F. Fransen, Ferry Ossendorp, Koen Raemdonck, Tina Vermonden, Wim E. Hennink, Cornelus F. van Nostrum
      Abstract: Targeting of antigens to dendritic cells (DCs) to induce strong cellular immune response can be established by loading in a nano‐sized carrier and keeping the antigen associated with the particles until they are internalized by DCs. In the present study, a model antigen (ovalbumin, OVA) is immobilized in cationic dextran nanogels via disulfide bonds. These bonds are stable in the extracellular environment but are reduced in the cytosol of DCs due to the presence of glutathione. Reversible immobilization of OVA in the nanogels is demonstrated by the fact that hardly any release of the protein occurred at pH 7 in the absence of glutathione, whereas rapid release of OVA occurs once the nanogels are incubated in buffer with glutathione. Furthermore, these OVA conjugated nanogels show intracellular release of the antigen in DCs and boost the MHC class I antigen presentation, demonstrating the feasibility of this concept for the aimed intracellular antigen delivery. The model antigen ovalbumin is chemically conjugated to the cationic nanogels via disulfide bonds. The protein is thereby covalently immobilized in the nanogels in the extracellular environment. Rapid release of conjugated protein occurs once the nanogels are internalized into cells, due to cleavage of the disulfide bonds in the presence of relatively high intracellular levels of glutathione (2.5–10 × 10−3 m).
      PubDate: 2015-04-08T13:01:33.932592-05:
      DOI: 10.1002/adfm.201500894
  • Dual‐Stage‐Light‐Guided Tumor Inhibition by
           Mitochondria‐Targeted Photodynamic Therapy
    • Authors: Kai Han; Qi Lei, Shi‐Bo Wang, Jing‐Jing Hu, Wen‐Xiu Qiu, Jing‐Yi Zhu, Wei‐Na Yin, Xu Luo, Xian‐Zheng Zhang
      Abstract: In this paper, a self‐delivery system PpIX‐PEG‐(KLAKLAK)2 (designated as PPK) is fabricated to realize mitochondria‐targeted photodynamic tumor therapy. It is found that the PPK self‐delivery system exhibited high drug loading efficacy as well as novel capacity in generation of intracellular reactive oxygen species (ROS). This study also indicated that the photochemical internalization effect of the photosensitizer protoporphyrin IX (PpIX) under a short time light irradiation improved the cellular internalization of PPK. On the contrary, PPK could target to the subcellular organelle mitochondria due to the presence of proapoptosis (KLAKLAK)2 peptide. Importantly, the in situ generation of ROS in mitochondria enhanced the photodynamic therapy efficacy under another long time irradiation, leading to significant cell death with decreased mitochondrial membrane potential. Besides, relative high tumor accumulation, minimal systemic cytotoxicity and efficacious long‐term tumor inhibition in vivo are also confirmed by using a murine model. All these results demonstrated the self‐delivery system PPK with a dual‐stage light irradiation strategy is a promising nanoplatform for tumor treatment. A mitochondria‐targeted self‐delivery system is developed for optical‐imaging‐guided photodynamic tumor therapy. A dual‐stage light irradiation strategy is used to optimize the synergistic effect between photosensitizer and (KLAKLAK)2, and significant efficacious tumor inhibition was observed both in vitro and in vivo.
      PubDate: 2015-04-08T13:01:25.930085-05:
      DOI: 10.1002/adfm.201500590
  • Tumor‐Penetrating Nanotherapeutics Loading a Near‐Infrared
           Probe Inhibit Growth and Metastasis of Breast Cancer
    • Authors: Xinyu He; Xiaoyue Bao, Haiqiang Cao, Zhiwen Zhang, Qi Yin, Wangwen Gu, Lingli Chen, Haijun Yu, Yaping Li
      Abstract: The tumor growth and metastasis is the leading reason for the high mortality of breast cancer. Herein, it is first reported a deep tumor‐penetrating photothermal nanotherapeutics loading a near‐infrared (NIR) probe for potential photothermal therapy (PTT) of tumor growth and metastasis of breast cancer. The NIR probe of 1,1‐dioctadecyl‐3,3,3,3‐tetramethylindotricarbocyanine iodide (DiR), a lipophilicfluorescent carbocyanine dye with strong light‐absorbing capability, is entrapped into the photothermal nanotherapeutics for PTT application. The DiR‐loaded photothermal nanotherapeutics (DPN) is homogeneous nanometer‐sized particles with the mean diameter of 24.5 ± 4.1 nm. Upon 808 nm laser irradiation, DPN presents superior production of thermal energy than free DiR both in vitro and in vivo. The cell proliferation and migration activities of metastatic 4T1 breast cancer cells are obviously inhibited by DPN in combination with NIR irradiation. Moreover, DPN can induce a higher accumulation in tumor and penetrate into the deep interior of tumor tissues. The in vivo PTT measurements indicate that the growth and metastasis of breast cancer are entirely inhibited by a single treatment of DPN with NIR irradiation. Therefore, the deep tumor‐penetrating DPN can provide a promising strategy for PTT of tumor progression and metastasis of breast cancer. A deep tumor‐penetrating photothermal nanotherapeutics loading a lipophilic near‐infrared (NIR) probe of 1,1‐dioctadecyl‐3,3,3,3‐tetramethylindotricarbocyanine iodide (DiR) (DiR‐loaded photothermal nanotherapeutics (DPN)) is first developed, and can generate high levels of thermal energy upon NIR irradiation for efficient photothermal therapy of tumor growth and metastasis of breast cancer.
      PubDate: 2015-04-08T12:59:10.756381-05:
      DOI: 10.1002/adfm.201500772
  • Temperature‐Induced Switchable Adhesion using
           Nickel–Titanium–Polydimethylsiloxane Hybrid Surfaces
    • Authors: Mareike Frensemeier; Jessica S. Kaiser, Carl P. Frick, Andreas S. Schneider, Eduard Arzt, Ray S. Fertig, Elmar Kroner
      Abstract: A switchable dry adhesive based on a nickel–titanium (NiTi) shape‐memory alloy with an adhesive silicone rubber surface has been developed. Although several studies investigate micropatterned, bioinspired adhesive surfaces, very few focus on reversible adhesion. The system here is based on the indentation‐induced two‐way shape‐memory effect in NiTi alloys. NiTi is trained by mechanical deformation through indentation and grinding to elicit a temperature‐induced switchable topography with protrusions at high temperature and a flat surface at low temperature. The trained surfaces are coated with either a smooth or a patterned adhesive polydimethylsiloxane (PDMS) layer, resulting in a temperature‐induced switchable surface, used for dry adhesion. Adhesion tests show that the temperature‐induced topographical change of the NiTi influences the adhesive performance of the hybrid system. For samples with a smooth PDMS layer the transition from flat to structured state reduces adhesion by 56%, and for samples with a micropatterned PDMS layer adhesion is switchable by nearly 100%. Both hybrid systems reveal strong reversibility related to the NiTi martensitic phase transformation, allowing repeated switching between an adhesive and a nonadhesive state. These effects have been discussed in terms of reversible changes in contact area and varying tilt angles of the pillars with respect to the substrate surface. Switchable adhesion is achieved using a nickel–titanium two‐way shape‐memory alloy combined with a bioinspired micropatterned dry adhesive silicone rubber. The temperature‐induced topography change of the shape memory alloy causes a well‐controlled reversible adhesive performance. The switching efficiency is tunable and reaches up to 100%, meanwhile maintaining high reversibility.
      PubDate: 2015-04-08T12:58:42.989844-05:
      DOI: 10.1002/adfm.201500437
  • Tuning Local Molecular Orientation–Composition Correlations in
           Binary Organic Thin Films by Solution Shearing
    • Authors: Wei Ma; Julia Reinspach, Yan Zhou, Ying Diao, Terry McAfee, Stefan C. B. Mannsfeld, Zhenan Bao, Harald Ade
      Abstract: A general impact of solution shearing on molecular orientation correlation is observed in polymer:fullerene organic solar cells in which one of the components forms fibrils or aggregates. Further investigation with polarized soft X‐ray scattering reveals that solution shearing induces more face‐to‐face orientation relative to the interface of two components compared to spin‐coating. This impact is shearing speed dependent, that is, slow shearing speed can induce more face‐to‐face orientation than a fast shearing speed. These results demonstrate that solution shearing is an effective method to control the relative molecular orientation. Solution shearing can also modify the domain size and average composition variations. The enhancement of local molecular orientation correlations of aggregates is achieved by shear‐coating compared to spin‐coating, the most widely used research fabrication tool. Molecular orientation is measured via polarized resonant soft X‐ray scattering. Such an orientation has been previously shown to be a critical structure factor that impacts the performance of devices. Shearing might thus be a method to improve device performance.
      PubDate: 2015-04-08T12:58:36.422586-05:
      DOI: 10.1002/adfm.201500468
  • Efficient Sb2S3‐Sensitized Solar Cells Via Single‐Step
           Deposition of Sb2S3 Using S/Sb‐Ratio‐Controlled
           SbCl3‐Thiourea Complex Solution
    • Authors: Yong Chan Choi; Sang Il Seok
      Abstract: To replace the conventional chemical bath deposition method, which is time‐consuming and has a high impurity level, a chemical single‐step deposition process employing a S/Sb ratio‐controlled SbCl3‐thiourea complex solution is introduced to load Sb2S3 into a mesoporous TiO2 electrode. This technique enables the fabrication of efficient and reproducible Sb2S3‐sensitzed inorganic–organic heterojunction hybrid solar cells with hole‐conducting conjugated polymers. The most efficient cell exhibits a short‐circuit current density of 16.1 mA cm−2, an open circuit voltage of 595.5 mV, and a fill factor of 66.5%, yielding a power conversion efficiency of ≈6.4% at standard AM1.5G condition (100 mW cm−2). A single‐step solution approach based on SbCl3‐thiourea complex solution processing is introduced for high‐efficiency Sb2S3‐sensitized solar cells. The Sb2S3 is easily deposited on substrates using S/Sb‐ratio‐controlled SbCl3‐thiourea complex solution. The champion device exhibits an overall power conversion efficiency of 6.4% under standard 1.5G conditions.
      PubDate: 2015-04-07T12:36:37.29616-05:0
      DOI: 10.1002/adfm.201500296
  • Fundamental Tradeoff between Emission Intensity and Efficiency in
           Light‐Emitting Electrochemical Cells
    • Authors: Stephan van Reenen; René A. J. Janssen, Martijn Kemerink
      Abstract: The characteristic doping process in polymer light‐emitting electrochemical cells (LECs) causes a tradeoff between luminescence intensity and efficiency. Experiments and numerical modeling on thin film polymer LECs show that, on the one hand, carrier injection and transport benefit from electrochemical doping, leading to increased electron‐hole recombination. On the other hand, the radiative recombination efficiency is reduced by exciton quenching by polarons involved in the doping. Consequently, the quasi‐steady‐state luminescent efficiency decreases with increasing ion concentration. The transient of the luminescent efficiency shows a characteristic roll‐off while the current continuously increases, attributed to ongoing electrochemical doping and the associated exciton quenching. Both effects can be modeled by exciton polaron‐quenching via diffusion‐assisted Förster resonance energy transfer. These results indicate that the tradeoff between efficiency and intensity is fundamental, suggesting that the application realm of future LECs should be sought in high‐brightness, low‐production cost devices, rather than in high‐efficiency devices. A Fundamental tradeoff between emission intensity and efficiency in light‐emitting electrochemical cells is reported. The admixed ions in LECs on the one hand improve charge transport by electrochemical doping, but on the other hand reduce the luminescent efficiency by quenching of excitons for KCF3SO3 densities of >1025 m−3.
      PubDate: 2015-04-07T12:36:33.010586-05:
      DOI: 10.1002/adfm.201403945
  • Theoretical Study of Rotary Freestanding Triboelectric Nanogenerators
    • Authors: Tao Jiang; Xiangyu Chen, Chang Bao Han, Wei Tang, Zhong Lin Wang
      Abstract: The use of triboelectric nanogenerators (TENG) is a highly effective technology for harvesting ambient mechanical energy to produce electricity. In this work, a theoretical model of rotary freestanding TENG with grating structure is constructed, including the conductor‐to‐dielectric and dielectric‐to‐dielectric categories. The finite element simulations are performed to capture the fundamental physics of rotary freestanding TENG. Based on the simulations and derivations of approximate analytical equations, the real‐time output characteristics of TENG with arbitrary load resistance are calculated. Furthermore, the influences of structural parameters of TENG and rotation rate on the output performance are investigated. The theory presented here facilitates a deep understanding of the working mechanism of rotary freestanding TENG and provides useful guidance for designing high performance TENG for energy harvesting applications. A theoretical model for rotary freestanding triboelectric nanogenerators with a grating structure is constructed. The fundamental physics of triboelectric nanogenerators is revealed by using the finite element method, and the dynamic output characteristics are theoretically calculated through the analytical solving of governing equation.
      PubDate: 2015-04-07T12:36:29.19976-05:0
      DOI: 10.1002/adfm.201500447
  • Bioinspired Interlocked and Hierarchical Design of ZnO Nanowire Arrays for
           Static and Dynamic Pressure‐Sensitive Electronic Skins
    • Authors: Minjeong Ha; Seongdong Lim, Jonghwa Park, Doo‐Seung Um, Youngoh Lee, Hyunhyub Ko
      Abstract: The development of electronic skin (e‐skin) is of great importance in human‐like robotics, healthcare, wearable electronics, and medical applications. In this paper, a bioinspired e‐skin design of hierarchical micro‐ and nano‐structured ZnO nanowire (NW) arrays in an interlocked geometry is suggested for the sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. The interlocked hierarchical structures enable a stress‐sensitive variation in the contact area between the interlocked ZnO NWs and also the efficient bending of ZnO NWs, which allow the sensitive detection of both static and dynamic tactile stimuli. The flexible e‐skin in a piezoresistive mode shows a high pressure sensitivity (−6.8 kPa−1) and an ultrafast response time (
      PubDate: 2015-04-07T12:36:23.366688-05:
      DOI: 10.1002/adfm.201500453
  • Improved Photocatalytic Performance of Heterojunction by Controlling the
           Contact Facet: High Electron Transfer Capacity between TiO2 and the {110}
           Facet of BiVO4 Caused by Suitable Energy Band Alignment
    • Authors: Houfen Li; Hongtao Yu, Xie Quan, Shuo Chen, Huimin Zhao
      Abstract: Charge separation at the interface of heterojunctions is affected by the energy band alignments of the materials that compose the heterojunctions. Controlling the contact crystal facets can lead to different energy band alignments owing to the varied electronic structures of the different crystal facets. Therefore, BiVO4‐TiO2 heterojunctions are designed with different BiVO4 crystal facets at the interface ({110} facet or {010} facet), named BiVO4‐110‐TiO2 and BiVO4‐010‐TiO2, respectively, to achieve high photocatalytic performance. Higher photocurrent density and lower photoluminescence intensity are observed with the BiVO4‐110‐TiO2 heterojunction than those of the BiVO4‐010‐TiO2 heterojunction, which confirms that the former possesses higher charge carrier separation capacity than the latter. The photocatalytic degradation results of both Rhodamine B and 4‐nonylphenol demonstrate that better photocatalytic performance is achieved on the BiVO4‐110‐TiO2 heterojunction than the BiVO4‐010‐TiO2 heterojunction under visible light (≥422 nm) irradiation. The higher electron transfer capacity and better photocatalytic performance of the BiVO4‐110‐TiO2 heterojunction are attributed to the more fluent electron transfer from the {110} facet of BiVO4 to TiO2 caused by the smaller interfacial energy barrier. This is further confirmed by the selective deposition of Pt on the TiO2 surface as well as the longer lifetime of Bi5+ in the BiVO4‐110‐TiO2 heterojunction. Two kinds of BiVO4‐TiO2heterojunctions with TiO2 grown on the {110} facet and {010} facet of BiVO4, respectively, are prepared. Heterojunction with TiO2 grown on the {110} facet of BiVO4 possesses higher charge carriers separation efficiency and better photocatalytic performance owing to the lower interfacial energy barrier between conduction band of {110} facet with that of TiO2.
      PubDate: 2015-04-07T12:35:43.086191-05:
      DOI: 10.1002/adfm.201500521
  • Modulated Thermoelectric Properties of Organic Semiconductors Using
           Field‐Effect Transistors
    • Authors: Fengjiao Zhang; Yaping Zang, Dazhen Huang, Chong‐an Di, Xike Gao, Henning Sirringhaus, Daoben Zhu
      Abstract: Organic thermoelectric materials, which can transform heat flow into electricity, have great potential for flexible, ultra‐low‐cost and large‐area thermoelectric applications. Despite rapid developments of organic thermoelectric materials, exploration and investigation of promising organic thermoelectric semiconductors still remain as a challenge. Here, the thermoelectric properties of several p‐ and n‐type organic semiconductors are investigated and studied, in particular, how the electric field modulations of the Seebeck coefficient in organic field‐effect transistors (OFETs) compare with the Seebeck coefficient in chemically doped films. The extracted relationship between the Seebeck coefficient (S) and electrical conductivity (σ) from the field‐effect transistor (FET) geometry is in good agreement with that of chemically doped films, enabling the investigation of the trade‐off relationship among σ, S, carrier concentration, and charging level. The results make OFETs an effective candidate for the thermoelectric studies of organic semiconductors. Investigation of thermoelectric properties of organic semiconductors is a fundamental issue toward effective application of high‐performance organic thermoelectric materials. It is reported on a systematic study of the thermoelectric properties for organic semiconductors via field‐effect transistors, which indicates that organic transistors should provide an effective platform to accelerate the screening of promising organic thermoelectric materials.
      PubDate: 2015-04-07T01:47:58.420877-05:
      DOI: 10.1002/adfm.201404397
  • Holey Graphene Nanomanufacturing: Structure, Composition, and
           Electrochemical Properties
    • Authors: Yi Lin; Xiaogang Han, Caroline J. Campbell, Jae‐Woo Kim, Bin Zhao, Wei Luo, Jiaqi Dai, Liangbing Hu, John W. Connell
      Abstract: Topology is critical for properties and function of 2D nanomaterials. Membranes and films from 2D nanomaterials usually suffer from large tortuosity as a result from dense restacking of the nanosheets and thus have limited utility in applications such as electrodes for supercapacitor and batteries, which require ion transport through the nanosheet thickness. In comparison with conventional porous 2D nanomaterials, introducing holes through the nanosheets to create holey 2D nanomaterials with retention of the 2D‐related properties is a more viable approach to improve molecular transport. Here, graphene is used as a model to study the fundamental structure‐property relationship as a result from defect‐enabled hole creation. Specifically, the correlation of electrochemical capacitive properties with structure and composition for holey graphene materials is prepared using a highly scalable controlled air oxidation process. The presence of holes on graphene sheets is not sufficient to account for the observed capacitance improvement. Rather, the improvement is achieved through the combination of an enhanced mesopore fraction with simultaneous oxygen doping while retaining the graphitic carbon network with minimal damage. The detailed understanding might be further applied to other 2D materials toward a broader range of both energy‐related and other applications. Holey 2D materials such as holey graphene are a novel class of nanomaterials with enhanced through‐plane transport enabled by holes with retained 2D‐related properties. By controlling the synthesis parameters of holey graphene, optimal electrochemical capacitive properties are achieved upon hole formation and modification, which dictates the fine balance of oxidative doping, mesopore formation, and graphitic carbon gasification.
      PubDate: 2015-04-07T01:46:47.799775-05:
      DOI: 10.1002/adfm.201500321
  • Functional and Well‐Defined β‐Sheet‐Assembled
           Porous Spherical Shells by Surface‐Guided Peptide Formation
    • Authors: Steven Harris Wibowo; Adrian Sulistio, Edgar H. H. Wong, Anton Blencowe, Greg G. Qiao
      Abstract: Polypeptides have attracted widespread attention as building blocks for complex materials due to their ability to form higher‐ordered structures such as β‐sheets. However, the ability to precisely control the formation of well‐defined β‐sheet‐assembled materials remains challenging as β‐sheet formation tends to lead to ill‐defined and unprocessable aggregates. This work reports a simple, rapid, and robust strategy to form well‐defined peptide β‐sheet‐assembled shells (i.e., hollow spheres) by employing surface‐initiated N‐carboxyanhydride ring‐opening polymerization under a highly efficient surface‐driven approach. The concept is demonstrated by the preparation of enzyme‐degradable rigid shell architectures composed of H‐bonded poly(L‐valine) (PVal) grafts with porous and sponge‐like surface morphology. The porous PVal‐shells exhibit a remarkable and unprecedented ability to non‐covalently entrap metal nanoparticles, proteins, drug molecules, and biorelevant polymers, which could potentially lead to a diverse range of biodegradable and functional platforms for applications ranging from therapeutic delivery to organic catalysis. Well‐defined peptide β‐sheet‐assembled porous shells with tailored dimensions are prepared by a simple, rapid, and robust bottom‐up strategy involving surface‐initiated ring‐opening polymerization. Further exploitation of the hollow shells demonstrates the ability to non‐covalently entrap small molecules, nanoparticles, proteins, drugs, and polymers to form functional materials for various potential applications.
      PubDate: 2015-04-03T03:16:45.049218-05:
      DOI: 10.1002/adfm.201404091
  • Gate‐Controlled Energy Barrier at a Graphene/Molecular Semiconductor
    • Authors: Subir Parui; Luca Pietrobon, David Ciudad, Saül Vélez, Xiangnan Sun, Fèlix Casanova, Pablo Stoliar, Luis E. Hueso
      Abstract: The formation of an energy‐barrier at a metal/molecular semiconductor junction is a universal phenomenon which limits the performance of many molecular semiconductor‐based electronic devices, from field‐effect transistors to light‐emitting diodes. In general, a specific metal/molecular semiconductor combination of materials leads to a fixed energy‐barrier. However, in this work, a graphene/C60 vertical field‐effect transistor is presented in which control of the interfacial energy‐barrier is demonstrated, such that the junction switches from a highly rectifying diode at negative gate voltages to a highly conductive nonrectifying behavior at positive gate voltages and at room temperature. From the experimental data, an energy‐barrier modulation of up to 660 meV, a transconductance of up to five orders of magnitude, and a gate‐modulated photocurrent are extracted. The ability to tune the graphene/molecular semiconductor energy‐barrier provides a promising route toward novel, high performance molecular devices. Graphene is an ideal candidate for the source electrode in a vertical organic field effect transistor as it has low density of states near the Dirac point and easy gate tunability of the Fermi‐level. By varying the gate electric field, the energy‐barrier is modulated at a graphene/molecular‐semiconductor (fullerene) junction, thus opening a promising route toward molecular‐semiconductor based devices.
      PubDate: 2015-03-31T08:44:38.804228-05:
      DOI: 10.1002/adfm.201403407
  • Dynamic Control of Full‐Colored Emission and Quenching of
           Photoresponsive Conjugated Polymers by Photostimuli
    • Authors: Kazuyoshi Watanabe; Hiroyuki Hayasaka, Tatsuaki Miyashita, Kenta Ueda, Kazuo Akagi
      Abstract: A series of photoresponsive and full‐colored fluorescent conjugated copolymers is synthesized by combining phenylene‐ and thienylene‐based main chains with photochromic dithienylethene (DE) side chains. Solutions and cast films of the polymers exhibit various colored fluorescence in visible wavelengths of 400−700 nm corresponding to emissions of the conjugated main chain. The fluorescence is reversibly photoswitched between emission and quenching through DE photoisomerization using external stimuli from ultraviolet and visible light irradiation. The reprecipitation method with ultrasonication enables the polymers to form spherical aggregates with diameters of 20−70 nm in water. After investigating and comparing the optical properties, the resulting nanosphere solutions are assumed to exist in an intermediate state between an isolated state (i.e., in solution) and an aggregated state in cast film. The majority of the nanosphere solutions also exhibit the same photoswitchable fluorescence behavior as those in the solutions and the cast films. The results demonstrate that the visible fluorescence of the conjugated copolymers is reversibly switchable between emission and quenching using the photoisomerizing DE side chain regardless of the fluorescent colors and the polymer chain aggregation. A series of photoresponsive and full‐colored fluorescent conjugated polymers are synthesized by combining phenylene‐ and thienylene‐based main chains with photochromic dithienylethene side chains. In chloroform solution, nanosphere solution, and solid film, the full‐colored fluorescence is reversibly switchable between emission and quenching through photoisomerization of dithienylethene side chains regardless of the fluorescent colors and the polymer chain aggregation.
      PubDate: 2015-03-30T08:07:22.318082-05:
      DOI: 10.1002/adfm.201500136
  • Oxygen Vacancy Creation, Drift, and Aggregation in TiO2‐Based
           Resistive Switches at Low Temperature and Voltage
    • Authors: Jonghan Kwon; Abhishek A. Sharma, James A. Bain, Yoosuf N. Picard, Marek Skowronski
      Abstract: Transmission electron microscopy with in situ biasing has been performed on TiN/single‐crystal rutile TiO2/Pt resistive switching structures. Three elementary processes essential for switching: i) creation of oxygen vacancies by electrochemical reactions at low temperatures (
      PubDate: 2015-03-30T07:55:38.420043-05:
      DOI: 10.1002/adfm.201500444
  • In‐Depth Studies on Rapid Photochemical Activation of Various
           Sol–Gel Metal Oxide Films for Flexible Transparent Electronics
    • Authors: Sungjun Park; Kwang‐Ho Kim, Jeong‐Wan Jo, Sujin Sung, Kyung‐Tae Kim, Won‐June Lee, Jaekyun Kim, Hyun Jae Kim, Gi‐Ra Yi, Yong‐Hoon Kim, Myung‐Han Yoon, Sung Kyu Park
      Abstract: Despite intensive research on photochemical activation of sol–gel metal oxide materials, the relatively long processing time and lack of deep understanding of the underlying chemical courses have limited their broader impact on diverse materials and applications such as thin‐film electronics, photovoltaics, and catalysts. Here, in‐depth studies on the rapid photochemical activation of diverse sol–gel oxide films using various spectroscopic and electrical investigations for the underlying physicochemical mechanism are reported. Based on the exhaustive chemical and physical analysis, it is noted that deep ultraviolet‐promoted rapid film formation such as densification, polycondensation, and impurity decomposition is possible within 5 min via in situ radical‐mediated reactions. Finally, the rapid fabrication of all‐solution metal oxide thin‐film‐transistor circuitry, which exhibits stable and reliable electrical performance with a mobility of >12 cm2 V−1 s−1 and an oscillation frequency of >650 kHz in 7‐stage ring oscillator even after bending at a radius of
      PubDate: 2015-03-30T07:54:12.61539-05:0
      DOI: 10.1002/adfm.201500545
  • Flexible and Controllable Piezo‐Phototronic Pressure Mapping Sensor
           Matrix by ZnO NW/p‐Polymer LED Array
    • Authors: Rongrong Bao; Chunfeng Wang, Lin Dong, Ruomeng Yu, Kun Zhao, Zhong Lin Wang, Caofeng Pan
      Abstract: A functional tactile sensing device is essential for next‐generation robotics and human–machine interfaces technologies, since the emulation of touching requires large‐scale pressure sensor arrays with distinguishable spatial‐resolution, high sensitivity, and fast response. Here, a flexible LED array composed of PEDOT:PSS and patterned ZnO NWs with a spatial resolution of 7 μm for mapping of spatial pressure distributions is designed and fabricated. The emission intensity of the LED array sensor matrix is dominated by locally applied strains as indicated by the piezo‐phototronic effect. Therefore, spatial pressure distributions are immediately obtained by parallel‐reading the illumination intensities of the LED arrays based on an electroluminescence working mechanism. A wide range of pressure measurements from 40 to 100 MPa are achieved through controlling the growth conditions of the ZnO nanowire array. These devices may find prospective applications as electronic skins by taking advantage of their high spatial‐resolution, flexibility, and wide pressure mapping range. The piezo‐phototronic effect is applied to prepare a flexible LED array composed of PEDOT:PSS and patterned ZnO NWs for mapping of spatial pressure distributions. The spatial resolution achieved is as high as 7 μm by fabricating ZnO nanowires on flexible substrates. By controlling the growth conditions of the ZnO nanowire array, a wide range of pressure measurements from 40 to 100 MPa are derived under different ZnO morphologies.
      PubDate: 2015-03-30T07:53:14.208996-05:
      DOI: 10.1002/adfm.201500801
  • Lanthanide–Organic Framework Nanothermometers Prepared by
    • Authors: Zhuopeng Wang; Duarte Ananias, Arnau Carné‐Sánchez, Carlos D. S. Brites, Inhar Imaz, Daniel Maspoch, João Rocha, Luís D. Carlos
      Abstract: Accurate, noninvasive, and self‐referenced temperature measurements at the submicrometer scale are of great interest, prompted by the ever‐growing demands in the fields of nanotechnology and nanomedicine. The thermal dependence of the phosphor's luminescence provides high detection sensitivity and spatial resolution with short acquisition times in, e.g., biological fluids, strong electromagnetic fields, and fast‐moving objects. Here, it is shown that nanoparticles of [(Tb0.914Eu0.086)2(PDA)3(H2O)]·2H2O (PDA = 1,4‐phenylenediacetic acid), the first lanthanide–organic framework prepared by the spray‐drying method, are excellent nanothermometers operating in the solid state in the 10–325 K range (quantum yield of 0.25 at 370 nm, at room temperature). Intriguingly, this system is the most sensitive cryogenic nanothermometer reported so far, combining high sensitivity (up to 5.96 ± 0.04% K−1 at 25 K), reproducibility (in excess of 99%), and low‐temperature uncertainty (0.02 K at 25 K). One of the most sensitive cryogenic thermometers (5.96% K−1 at 25 K) reported so far is described, consisting of lanthanide (Tb3+, Eu3+) organic framework nanoparticles prepared by spray‐drying, exhibiting an excellent reproducibility (>99%) and low‐temperature uncertainty (0.02 K at 25 K).
      PubDate: 2015-03-30T07:52:26.593074-05:
      DOI: 10.1002/adfm.201500518
  • Ultralight, Soft Polymer Sponges by Self‐Assembly of Short
           Electrospun Fibers in Colloidal Dispersions
    • Authors: Gaigai Duan; Shaohua Jiang, Valérie Jérôme, Joachim H. Wendorff, Amir Fathi, Jaqueline Uhm, Volker Altstädt, Markus Herling, Josef Breu, Ruth Freitag, Seema Agarwal, Andreas Greiner
      Abstract: Ultralight polymer sponges are prepared by freeze‐drying of dispersions of short electrospun fibers. In contrast to many other highly porous materials, these sponges show extremely low densities (
      PubDate: 2015-03-30T02:58:44.088661-05:
      DOI: 10.1002/adfm.201500001
  • In Situ Production of Biofunctionalized Few‐Layer Defect‐Free
           Microsheets of Graphene
    • Authors: Alfredo M. Gravagnuolo; Eden Morales‐Narváez, Sara Longobardi, Everson T. da Silva, Paola Giardina, Arben Merkoçi
      Abstract: Biological interfacing of graphene has become crucial to improve its biocompatibility, dispersability, and selectivity. However, biofunctionalization of graphene without yielding defects in its sp2‐carbon lattice is a major challenge. Here, a process is set out for biofunctionalized defect‐free graphene synthesis through the liquid phase ultrasonic exfoliation of raw graphitic material assisted by the self‐assembling fungal hydrophobin Vmh2. This protein (extracted from the edible fungus Pleurotus ostreatus) is endowed with peculiar physicochemical properties, exceptional stability, and versatility. The unique properties of Vmh2 and, above all, its superior hydrophobicity, and stability allow us to obtain a highly concentrated (≈440–510 μg mL−1) and stable exfoliated material (ζ‐potential, +40/+70 mV). In addition controlled centrifugation enables the selection of biofunctionalized few‐layer defect‐free micrographene flakes, as assessed by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and electrophoretic mobility. This biofunctionalized product represents a high value added material for the emerging applications of graphene in the biotechnological field such as sensing, nanomedicine, and bioelectronics technologies. Biofunctionalized defect‐free few‐layer graphene microsheets can be obtained using liquid phase ultrasonic exfoliation of raw graphitic material assisted by the self‐assembling fungal hydrophobin Vmh2. This approach enables a highly concentrated and stable exfoliated product. The obtained material is likely to prove valuable for the emerging applications of graphene in the biotechnological field.
      PubDate: 2015-03-30T02:58:20.632739-05:
      DOI: 10.1002/adfm.201500016
  • Biocompatible Nanoparticles Based on Diketo‐Pyrrolo‐Pyrrole
           (DPP) with Aggregation‐Induced Red/NIR Emission for In Vivo
           Two‐Photon Fluorescence Imaging
    • Authors: Yuting Gao; Guangxue Feng, Tao Jiang, Chiching Goh, Laiguan Ng, Bin Liu, Bo Li, Lin Yang, Jianli Hua, He Tian
      Abstract: Compared with traditional one‐photon fluorescence imaging, two‐photon fluorescence imaging techniques have shown advantages such as increased penetration depth, lower tissue autofluorescence, and reduced photo­damage, and therefore are particularly useful for imaging tissues and animals. In this work, the design and synthesis of two novel DPP‐based compounds with large two‐photon absorption (2PA) cross‐sections (σ ≥ 8100 GM) and aggregation‐induced emission (AIE) properties are reported. The new compounds are red/NIR emissive and show large Stokes shifts (Δλ ≥ 3571 cm−1). 1,2‐Distearoyl‐sn‐glycero‐3‐phosphoethanol amine‐N‐[maleimide(polyethylene glycol)‐2000 (DSPE‐PEG‐Mal) is used as the encapsulation matrix to encapsulate DPP‐2, followed by surface functionalization with cell penetrating peptide (CPP) to yield DPP‐2‐CPP nanoparticles with high brightness, good water dispersibility, and excellent biocompatibility. DPP‐2 nanoparticles have been used for cell imaging and two‐photon imaging with clear visualization of blood vasculature inside mouse ear skin with a depth up to 80 μm. Design and synthesis of two novel red/NIR emissive DPP‐based compounds with large two‐photon absorption cross‐sections and aggregation‐induced emission properties are reported. After being fabricated by DSPE‐PEG‐Mal and CPP, DPP‐2‐CPP nanoparticles are used for cell imaging and two‐photon imaging, with clear visualization of blood vasculature inside mouse ear skin.
      PubDate: 2015-03-30T02:58:12.940393-05:
      DOI: 10.1002/adfm.201500010
  • MoS2/Si Heterojunction with Vertically Standing Layered Structure for
           Ultrafast, High‐Detectivity, Self‐Driven Visible–Near
           Infrared Photodetectors
    • Authors: Liu Wang; Jiansheng Jie, Zhibin Shao, Qing Zhang, Xiaohong Zhang, Yuming Wang, Zheng Sun, Shuit‐Tong Lee
      Abstract: As an interesting layered material, molybdenum disulfide (MoS2) has been extensively studied in recent years due to its exciting properties. However, the applications of MoS2 in optoelectronic devices are impeded by the lack of high‐quality p–n junction, low light absorption for mono‐/multilayers, and the difficulty for large‐scale monolayer growth. Here, it is demonstrated that MoS2 films with vertically standing layered structure can be deposited on silicon substrate with a scalable sputtering method, forming the heterojunction‐type photodetectors. Molecular layers of the MoS2 films are perpendicular to the substrate, offering high‐speed paths for the separation and transportation of photo‐generated carriers. Owing to the strong light absorption of the relatively thick MoS2 film and the unique vertically standing layered structure, MoS2/Si heterojunction photodetectors with unprecedented performance are actualized. The self‐driven MoS2/Si heterojunction photodetector is sensitive to a broadband wavelength from visible light to near‐infrared light, showing an extremely high detectivity up to ≈1013 Jones (Jones = cm Hz1/2 W−1), and an ultrafast response speed of ≈3 μs. The performance is significantly better than the photodetectors based on mono‐/multilayer MoS2 nanosheets. Additionally, the MoS2/Si photodetectors exhibit excellent stability in air for a month. This work unveils the great potential of MoS2/Si heterojunction for optoelectronic applications. A new type of visible–near infrared self‐driven photodetector is developed by sputtering a layer of n‐type MoS2 film with a vertically standing layered structure on p‐type silicon. With the advantages of easy fabrication, wide response spectrum, extremely high detectivity (≈1013 Jones), ultrafast response speed (≈3 μs), and good durability, this heterojunction photodetector shows great potential for optoelectronic applications.
      PubDate: 2015-03-30T02:57:33.736852-05:
      DOI: 10.1002/adfm.201500216
  • Symmetric and Asymmetric Decoration of Graphene: Bimetal‐Graphene
    • Authors: Peter S. Toth; Matěj Velický, Quentin M. Ramasse, Desponia M. Kepaptsoglou, Robert A. W. Dryfe
      Abstract: Low‐dimensional carbon materials, i.e., graphene and its functionalization with a number of semiconductor or conductor materials, such as noble metal nanostructures, have primary importance for their potential exploitation as electro‐active materials, i.e., as new generation catalysts. Here, low‐cost, solution chemistry‐based, two‐step functionalization of an individual, free‐standing, chemical vapor‐deposited graphene monolayer is reported, with noble metal (Au, Pt, Pd) nanoparticles to build up two‐side decorated graphene‐based metal nanoclusters. Either the same metal (symmetric decoration) or different metals (asymmetric decoration) are used for the preparation of bimetal graphene sandwiches, which are adsorbed at the liquid/liquid (organic/water) interface. The successful fabrication of such dual‐decorated graphene‐based metal nanocomposites is confirmed using various microscopic techniques (scanning electron and atomic force microscopies) and several spectroscopic methods (x‐ray photoelectron, energy dispersive x‐ray, mapping mode Raman spectroscopy, and electron energy loss spectroscopy). Taken together, it is inferred from these techniques that the location of deposited metal nanoparticles is on opposite sides of the graphene. Graphene is asymmetrically functionalized with different metal nanoparticles. Such dual‐decorated graphene‐based metal nanoclusters are studied using various microscopic techniques and several spectroscopic methods to prove the double‐side decorated monolayer graphene. The preparation of sandwich structures of graphene with two different species opens the way for further asymmetric decoration processes at the polarizable liquid/liquid interface.
      PubDate: 2015-03-30T02:56:34.206207-05:
      DOI: 10.1002/adfm.201500277
  • Controllable Patterning of Different Cells Via Optical Assembly of 1D
           Periodic Cell Structures
    • Authors: Hongbao Xin; Yuchao Li, Baojun Li
      Abstract: Flexible patterning of different cells into designated locations with direct cell–cell contact at single‐cell patterning precision and control is of great importance, however challenging, for cell patterning. Here, an optical assembly method for patterning of different types of cells via direct cell–cell contact at single‐cell patterning precision and control is demonstrated. Using Escherichia coli and Chlorella cells as examples, different cells are flexibly patterned into 1D periodic cell structures (PCSs) with controllable configurations and lengths, by periodically connecting one type of cells with another by optical force. The patterned PCSs can be flexibly moved and show good light propagation ability. The propagating light signals can be detected in real‐time, providing new opportunities for the detection of transduction signals among patterned cells. This patterning method is also applicable for cells of other kinds, including mammalian/human cells. Cells of different types can be patterned into periodic cell structures with controlled lengths and configurations at single‐cell patterning control via direct cell–cell contact, using an optical assembly method. Light can propagate along the patterned cell structures, and the propagating signal can be detected in real‐time. This patterning method is also applicable for mammalian/human cells.
      PubDate: 2015-03-30T02:56:02.001058-05:
      DOI: 10.1002/adfm.201500287
  • Mussel‐Inspired Electrospun Smart Magnetic Nanofibers for
           Hyperthermic Chemotherapy
    • Authors: Amin GhavamiNejad; Arathyram Ramachandra Kurup Sasikala, Afeesh Rajan Unnithan, Reju George Thomas, Yong Yeon Jeong, Mohammad Vatankhah‐Varnoosfaderani, Florian J. Stadler, Chan Hee Park, Cheol Sang Kim
      Abstract: A method for the versatile synthesis of novel, mussel‐inspired, electrospun nanofibers with catechol moieties is reported. These mussel‐inspired nanofibers are used to bind iron oxide nanoparticles (IONPs) and the borate‐containing anticancer drug Bortezomib (BTZ) through a catechol metal binding mechanism adapted from nature. These smart nanofibers exhibit a unique conjugation of Bortezomib to their 1, 2‐benzenediol (catechol) moieties for enabling a pH‐dependent drug delivery towards the cancer cells and the IONPs via strong coordination bonds for exploiting the repeated application of hyperthermia. Thus the synergistic anticancer effect of these mussel‐inspired magnetic nanofibers were tested in vitro for the repeated application of hyperthermia along with the chemotherapy and found that the drug‐bound catecholic magnetic nanofibers exhibited excellent therapeutic efficacy for potential anticancer treatment. Drug‐loaded magnetic nanofibers are designed for a synergistic anticancer treatment that combines hyperthermia treatment and chemotherapy. A mussel‐inspired binding is used to incorporate iron oxide nanoparticles (IONPs) and the drug onto the nanofibers. The smart nanofibers are capable of pH‐dependent drug delivery to cancer cells, and their IONPs enable multiple cycles of hyperthermia therapy with the application of an alternating magnetic field (AMF).
      PubDate: 2015-03-30T02:55:24.705411-05:
      DOI: 10.1002/adfm.201500389
  • Doped Organic Semiconductors: Trap‐Filling, Impurity Saturation, and
           Reserve Regimes
    • Authors: Max L. Tietze; Paul Pahner, Kathleen Schmidt, Karl Leo, Björn Lüssem
      Abstract: A typical human being carries billions of silicon‐based field‐effect transistors in his/her pockets. What makes these transistors work is Fermi level control, both by doping and field effect. Organic semiconductors are the core of a novel flexible electronics age, but the key effect of doping is still little understood. Here, precise handling is demonstrated for molar doping ratios as low as 10−5 in p‐ and n‐doped organic thin‐films by vacuum co‐sublimation, allowing comprehensive studying of the Fermi level control over the whole electronic gap of an organic semiconductor. In particular, dopant saturation and reserve regimes are observed for the first time in organic semiconductors. These results will allow for completely new design rules of organic transistors with improved long term stability and precise parameter control. Fermi level control over the whole electronic gap of an organic semiconductor is demonstrated by applying the concept of molecular p‐ and n‐type doping. In particular, observation of the dopant saturation and reserve regimes is shown for the first time in organic semiconductors, substantiating the cross‐link to classical semiconductor theory. At ultralow concentrations doping provides filling of trap states.
      PubDate: 2015-03-26T13:22:16.479618-05:
      DOI: 10.1002/adfm.201404549
  • How to Improve Spermbot Performance
    • Authors: Veronika Magdanz; Mariana Medina‐Sánchez, Yan Chen, Maria Guix, Oliver G. Schmidt
      Abstract: Spermbots are biocompatible hybrid machines that consist of microtubes which are propelled by single spermatozoa and have promising features for powering nano and microdevices. This article presents three approaches on how to improve the performance of such spermbots. First, 20 μm microtubes produce faster spermbots compared to the previously reported 50 μm long microtubes. Furthermore, biofunctionalization by microcontact printing and surface chemistry of biomolecules on the inner tube surface improve the coupling efficiency between sperm cell and microtube, and the addition of caffeine results in a speed boost of the sperm‐driven micromotor. Improved spermbot performance is demonstrated by biofunctionalization of the inner tube surface, shorter tube design, and caffeine addition. Firstly, spermbot velocity is improved by the use of shorter microtubes; secondly, better coupling efficiency is achieved by binding of fibronectin inside the microtube; and finally, caffeine addition gives a temporary speed boost to the spermbot.
      PubDate: 2015-03-26T13:22:11.458307-05:
      DOI: 10.1002/adfm.201500015
  • Efficiently Releasing the Trapped Energy Flow in White Organic
           Light‐Emitting Diodes with Multifunctional Nanofunnel Arrays
    • Authors: Lei Zhou; Qing‐Dong Ou, Yan‐Qing Li, Heng‐Yang Xiang, Lu‐Hai Xu, Jing‐De Chen, Chi Li, Su Shen, Shuit‐Tong Lee, Jian‐Xin Tang
      Abstract: White organic light‐emitting diodes (OLEDs) hold great promise for applications in displays and lighting due to high efficiency and superior white color balance. However, further improvement in efficiency remains a continuous and urgent demand due to limited energy flow extraction. A powerful method for drastically releasing the trapped energy flow in conventional white OLEDs is demonstrated by implementing unique quasi‐periodic subwavelength nanofunnel arrays (NFAs) via soft nanoimprinting lithography, which is ideal for enhancing light extraction without any spectral distortion or angular dependence. The resulting efficiency is over 2 times that of a conventional OLED used as a comparison. The external quantum efficiency and power efficiency are raised to 32.4% and 56.9 lm W−1, respectively. Besides, the substantial increase in efficiency over a broad bandwidth with angular color stability, the experimental proofs show that the NFA‐based extraction structure affords the enticing capacity against scrubbing and the self‐cleaning feature, which are critical to the commercial viability in practical applications. A powerful method for drastically releasing the trapped energy flow in white organic light‐emitting diodes is demonstrated by nanoimprinting multifunctional quasi‐periodic nanofunnel arrays. The broadband light extraction is realized without spectral changes and angular dependence, yielding an external quantum efficiency 2.3 times that of the conventional device and improved power efficiency. This extraction nanostructure also affords the enticing capacity against scrubbing and the self‐cleaning feature.
      PubDate: 2015-03-26T13:21:46.215831-05:
      DOI: 10.1002/adfm.201500310
  • Hydrogen Evolution: Hybrid Z‐Scheme Using Photosystem I and BiVO4
           for Hydrogen Production (Adv. Funct. Mater. 16/2015)
    • Authors: Younghye Kim; Della Shin, Woo Je Chang, Hae Lin Jang, Chan Woo Lee, Hye‐Eun Lee, Ki Tae Nam
      Pages: 2345 - 2345
      Abstract: In the Z‐scheme of photosynthesis, two photosynthetic proteins, photosystem II and photosystem I, excite electrons step‐wise using the light energy. On page 2369, K. T. Nam and team report a hybrid Z‐scheme using photosystem I and a BiVO4 semiconductor. In this study, step‐wise charge separation in photosystem I and BiVO4 enables the production of hydrogen from only water under visible light, for the first time.
      PubDate: 2015-04-21T05:49:29.191376-05:
      DOI: 10.1002/adfm.201570106
  • Hybrid Perovskites: Photophysics of Organic–Inorganic Hybrid Lead
           Iodide Perovskite Single Crystals (Adv. Funct. Mater. 16/2015)
    • Authors: Hong‐Hua Fang; Raissa Raissa, Mustapha Abdu‐Aguye, Sampson Adjokatse, Graeme R. Blake, Jacky Even, Maria Antonietta Loi
      Pages: 2346 - 2346
      Abstract: Hybrid organometal halide perovskites have been demonstrated to have outstanding performance as semiconductors for solar energy conversion. The understanding of their intrinsic properties is a fundamental step towards the technological exploitation of these materials. The article by G. R. Blake, J. Even, M. A. Loi, and co‐workers on page 2378 investigates these intrinsic properties by studying the structural and photophysical properties of high quality single crystals of CH3NH3PbI3 from room temperature to 5 K.
      PubDate: 2015-04-21T05:49:34.538761-05:
      DOI: 10.1002/adfm.201570107
  • Contents: (Adv. Funct. Mater. 16/2015)
    • Pages: 2347 - 2352
      PubDate: 2015-04-21T05:49:35.945608-05:
      DOI: 10.1002/adfm.201570108
  • Shear‐Band Dynamics in Metallic Glasses
    • Authors: Robert Maaß; Jörg F. Löffler
      Pages: 2353 - 2368
      Abstract: The future of metallic glasses as an advanced structural and functional material will to a great extent depend on the understanding and control of their mesoscopic flow defects called shear bands. These defects are sweet‐and‐sour; sweet because they mediate macroscopic plasticity at room temperature, and sour because they quickly promote failure. In the past decade, fundamental research generated great progress in characterizing the role that shear bands play during plastic deformation of disordered systems, including metallic glasses. Similar to those in many other materials, shear bands in metallic glasses are only active for a very short time, which directed research focus towards topological, structural, chemical, and thermal properties of formed, but inactive shear bands. In this paper, recent progress in directly characterizing the shear‐band dynamics in situ during straining experiments is presented. Various shear‐banding stages are outlined, including formation, propagation, and arrest, as well as shear‐band creep and aging. The results are discussed in a more general context of disordered materials, concluding with a summarizing overview of time‐scales involved in shear banding, and describing future research directions that may lead to controlled shear‐band plasticity in metallic glasses. Dynamic properties of shear bands are a key element for the design of plastically stable bulk metallic glasses. In this Feature Article, recent progress on in situ characterization of shear‐band dynamics is summarized. The aim is to provide a comprehensive understanding of shear‐band initiation, propagation, arrest, creep, and aging, and how they determine the plastic flow behavior of bulk metallic glasses.
      PubDate: 2015-03-18T03:10:47.378201-05:
      DOI: 10.1002/adfm.201404223
  • Hybrid Z‐Scheme Using Photosystem I and BiVO4 for Hydrogen
    • Authors: Younghye Kim; Della Shin, Woo Je Chang, Hae Lin Jang, Chan Woo Lee, Hye‐Eun Lee, Ki Tae Nam
      Pages: 2369 - 2377
      Abstract: The so‐called Z‐scheme is a means of utilizing photo‐induced electrons from a photosystem and has consistently motivated the design of synthetic photocatalytic systems. Although progress has been made in many pioneering studies on an inorganic‐based Z‐scheme, there have been no reports of a hybrid Z‐scheme for an inorganic and a photosystem. Here, a hybrid Z‐scheme is demonstrated by integrating a platinized photosystem I (PSI) and BiVO4 for hydrogen production. Up to now, PSI‐driven systems have been limited to a one‐step photoreduction reaction using sacrificial reductants. In this hybrid Z‐scheme, step‐wise charge separation in PSI and BiVO4 enables the production of hydrogen from only water under visible light. PSI and BiVO4 are conjugated via metal mediators to form an all‐linked structure. The novel design exhibits potential for the development of a protein hybrid system for electrochemical devices, sensors, and a solar energy conversion system. The first hybrid Z‐scheme by using photo­system I and a semiconductor in an all‐linked structure is reported. The hybrid system produces hydrogen from water without the use of a reducing additive under visible light. This novel system provides a new means of using photosynthetic proteins in photocatalytic applications.
      PubDate: 2015-02-18T07:53:27.917139-05:
      DOI: 10.1002/adfm.201404556
  • Photophysics of Organic–Inorganic Hybrid Lead Iodide Perovskite
           Single Crystals
    • Authors: Hong‐Hua Fang; Raissa Raissa, Mustapha Abdu‐Aguye, Sampson Adjokatse, Graeme R. Blake, Jacky Even, Maria Antonietta Loi
      Pages: 2378 - 2385
      Abstract: Hybrid organometal halide perovskites have been demonstrated to have outstanding performance as semiconductors for solar energy conversion. Further improvement of the efficiency and stability of these devices requires a deeper understanding of their intrinsic photophysical properties. Here, the structural and optical properties of high‐quality single crystals of CH3NH3PbI3 from room temperature to 5 K are investigated. X‐ray diffraction reveals an extremely sharp transition at 163 K from a twinned tetragonal I4/mcm phase to a low‐temperature phase characterized by complex twinning and possible frozen disorder. Above the transition temperature, the photoluminescence is in agreement with a band‐edge transition, explaining the outstanding performances of the solar cells. Whereas below the transition temperature, three different excitonic features arise, one of which is attributed to a free‐exciton and the other two to bound excitons (BEs). The BEs are characterized by a decay dynamics of about 5 μs and by a saturation phenomenon at high power excitation. The long lifetime and the saturation effect make us attribute these low temperature features to bound triplet excitons. This results in a description of the room temperature recombination as being due to spontaneous band‐to‐band radiative transitions, whereas a diffusion‐limited behavior is expected for the low‐temperature range. Low‐temperature photophysical investigations of CH3NH3PbI3 single crystals indicate that the recombination in these perovskites is due to spontaneous band‐to‐band radiative transition at room temperature and to singlet‐free‐exciton and bound‐triplet excitons below the phase transition temperature. The bound‐triplet excitons are characterized by a decay dynamics of about 5 μs and by a saturation phenomenon due to many‐body interactions.
      PubDate: 2015-02-13T06:37:53.374625-05:
      DOI: 10.1002/adfm.201404421
  • Remotely Controlled Red Blood Cell Carriers for Cancer Targeting and
           Near‐Infrared Light‐Triggered Drug Release in Combined
    • Authors: Xiaoqi Sun; Chao Wang, Min Gao, Aiyan Hu, Zhuang Liu
      Pages: 2386 - 2394
      Abstract: Red blood cells (RBCs), the “innate carriers” in blood vessels, are gifted with many unique advantages in drug transportation over synthetic drug delivery systems (DDSs). Herein, a tumor angiogenesis targeting, light stimulus‐responsive, RBC‐based DDS is developed by incorporating various functional components within the RBC platform. An albumin bound near‐infrared (NIR) dye, together with a chemotherapy drug doxorubicin, is encapsulated inside RBCs, the surfaces of which are modified with a targeting peptide to allow cancer targeting. Under stimulation by an external NIR laser, the membrane of the RBCs would be destroyed by the light‐induced photothermal heating, resulting in effective drug release. As a proof of principle, RBC‐based cancer cell targeted drug delivery and light‐controlled drug release is demonstrated in vitro, achieving a marked synergistic therapeutic effect through the combined photothermal–chemotherapy. This work presents a novel design of smart RBC carriers, which are inherently biocompatible, promising for targeted combination therapy of cancer. A tumor angiogenesis targeting red blood cell (RBC)‐based drug delivery system is successfully fabricated by incorporating various functional components within the RBC platform, and is responsive to near‐infrared light stimulus. As a proof of principle, RBC‐based cancer cell targeted drug delivery and light‐controlled drug release is demonstrated in vitro, achieving a marked synergistic therapeutic effect through the combined photothermal–chemotherapy.
      PubDate: 2015-02-25T05:46:41.626855-05:
      DOI: 10.1002/adfm.201500061
  • Flexible and Highly Sensitive Strain Sensors Fabricated by Pencil Drawn
           for Wearable Monitor
    • Authors: Xinqin Liao; Qingliang Liao, Xiaoqin Yan, Qijie Liang, Haonan Si, Minghua Li, Hualin Wu, Shiyao Cao, Yue Zhang
      Pages: 2395 - 2401
      Abstract: Functional electrical devices have promising potentials in structural health monitoring system, human‐friendly wearable interactive system, smart robotics, and even future multifunctional intelligent room. Here, a low‐cost fabrication strategy to efficiently construct highly sensitive graphite‐based strain sensors by pencil‐trace drawn on flexible printing papers is reported. The strain sensors can be operated at only two batteries voltage of 3 V, and can be applied to variously monitoring microstructural changes and human motions with fast response/relaxation times of 110 ms, a high gauge factor (GF) of 536.6, and high stability >10 000 bending–unbending cycles. Through investigation of service behaviors of the sensors, it is found that the microcracks occur on the surface of the pencil‐trace and have a major influence on the functions of the strain sensors. These performances of the strain sensor attain and even surpass the properties of recent strain sensing devices with subtle design of materials and device architectures. The pen‐on‐paper (PoP) approach may further develop portable, environmentally friendly, and economical lab‐on‐paper applications and offer a valuable method to fabricate other multifunctional devices. Easy‐to‐fabricate, cost‐effective, soft, lightweight, versatile sensors revolutionize the sensing technology and can be applied in personal electronic devices, artificial intelligence systems, and structural health monitoring. The pen‐on‐paper approach endows the pencil trace based on a printing paper with strain‐sensing capability for monitoring the rapid microstrain structural variation, book folding, and human motion. The sensors are low carbon footprint, disposable, and green products.
      PubDate: 2015-03-11T11:08:49.884974-05:
      DOI: 10.1002/adfm.201500094
  • TAPE: A Medical Adhesive Inspired by a Ubiquitous Compound in Plants
    • Authors: Keumyeon Kim; Mikyung Shin, Mi‐Young Koh, Ji Hyun Ryu, Moon Sue Lee, Seonki Hong, Haeshin Lee
      Pages: 2402 - 2410
      Abstract: Adhesives play an important role in industrial fields such as electronics, architectures, energy plantation, and others. However, adhesives used for medical purpose are rather under‐developed compared with those used in industry and consumer products. One key property required for medical adhesives is to maintain their adhesiveness in the presence of body fluid. Here, an entirely new class of medical adhesives called TAPE is reported; this is produced by intermolecular hydrogen bonding between a well‐known polyphenol compound, tannic acid, and poly(ethylene glycol). The preparation method of TAPE is extremely easy, forming a few liters at once by just the simple mixing of the two compounds without any further chemical synthetic procedures. TAPE shows a 250% increase in adhesion strength compared with fibrin glue, and the adhesion is well maintained in aqueous environments. It is demonstrated that TAPE is an effective hemostatic material and a biodegradable patch for detecting gastroesophageal reflux disease in vivo. Widespread use of TAPE is anticipated in various medical and pharmaceutical applications such as muco‐adhesives, drug depots, and others, because of its scalability, adhesion, and facile preparation. TAPE is a medical glue inspired by the adhesive properties of polyphenols and is found ubiquitously in plant species. The adhesion strength of TAPE exhibits a 250% increase relative to that of fibrin glue, and TAPE exhibits wet‐resistant adhesion. TAPE can be an effective hemostatic material and a pH‐sensitive patch for detecting gastroesophageal reflux disease in vivo.
      PubDate: 2015-03-16T02:45:20.294042-05:
      DOI: 10.1002/adfm.201500034
  • Printing Nanostructures with a Propelled Anti‐Pinning Ink Droplet
    • Authors: Gady Konvalina; Alexander Leshansky, Hossam Haick
      Pages: 2411 - 2419
      Abstract: Striving for cheap and robust manufacturing processes has prompted efforts to adapt and extend methods for printed electronics and biotechnology. A new “direct‐write” printing method for patterning nanometeric species in addressable locations has been developed, by means of evaporative deposition from a propelled anti‐pinning ink droplet (PAPID) in a manner analogous to a snail‐trail. Three velocity‐controlled deposition regimes have been identified; each spontaneously produces distinct and well‐defined self‐assembled deposition patterns. Unlike other technologies that rely on overlapping droplets, PAPIDs produce continuous patterns that can be formed on rigid or flexible substrates, even within 3D concave closed shapes, and have the ability to control the thickness gradient along the pattern. This versatile low cost printing method can produce a wide range of unusual electronic systems not attainable by other methods. Lateral actuation of propelled anti‐pinning ink droplets is presented and explored as a new approach for patterning nanomaterials. This approach achieves continuous patterns that can be formed on rigid or flexible substrates, even within 3D concave closed shapes, and offers the ability to produce a controlled thickness gradient along the patterns.
      PubDate: 2015-03-16T02:54:40.711731-05:
      DOI: 10.1002/adfm.201500215
  • Self‐Powered Electronics by Integration of Flexible
           Solid‐State Graphene‐Based Supercapacitors with High
           Performance Perovskite Hybrid Solar Cells
    • Authors: Pengcheng Du; Xiaowen Hu, Chao Yi, Huckleberry C. Liu, Peng Liu, Hao‐Li Zhang, Xiong Gong
      Pages: 2420 - 2427
      Abstract: To develop high‐capacitance flexible solid‐state supercapacitors and explore its application in self‐powered electronics is one of ongoing research topics. In this study, self‐stacked solvated graphene (SSG) films are reported that have been prepared by a facile vacuum filtration method as the free‐standing electrode for flexible solid‐state supercapacitors. The highly hydrated SSG films have low mass loading, high flexibility, and high electrical conductivity. The flexible solid‐state supercapacitors based on SSG films exhibit excellent capacitive characteristics with a high gravimetric specific capacitance of 245 F g−1 and good cycling stability of 10 000 cycles. Furthermore, the flexible solid‐state supercapacitors are integrated with high performance perovskite hybrid solar cells (pero‐HSCs) to build self‐powered electronics. It is found that the solid‐state supercapacitors can be charged by pero‐HSCs and discharged from 0.75 V. These results demonstrate that the self‐powered electronics by integration of the flexible solid‐state supercapacitors with pero‐HSCs have great potential applications in storage of solar energy and in flexible electronics, such as portable and wearable personal devices. Self‐powered electronics is demonstrated by integration of high‐performance perovskite hybrid solar cells with flexible solid‐state supercapacitors, which is based on self‐stacked solvated graphene films and possess high capacitance and excellent mechanical properties. The self‐powered electronics is further demonstrated to have great potential applications in storage of solar energy.
      PubDate: 2015-03-21T09:14:45.307538-05:
      DOI: 10.1002/adfm.201500335
  • 2D Janus Hybrid Materials of Polymer‐Grafted Carbon
           Nanotube/Graphene Oxide Thin Film as Flexible, Miniature Electric Carpet
    • Authors: Peng Xiao; Changjin Wan, Jincui Gu, Zhenzhong Liu, Yonghong Men, Youju Huang, Jiawei Zhang, Liqiang Zhu, Tao Chen
      Pages: 2428 - 2435
      Abstract: Ultrathin, freestanding polymer hybrid film with macroscopic sizes and molecular thicknesses have received significant interest due to their applications as functional devices, microsensors or nanoactuators. Herein, a 2D Janus hybrid of polymer‐grafted carbon nanotubes/graphene oxide (CNTs/GO) thin film is fabricated using microcontact printed CNTs/GO as photo active surface to grow polymer brushes by self‐initiated photografting and photopolymerization selectively from one side of CNTs/GO film. This achieved 2D Janus hybrid materials with grafted polymer layer as insulative carpet and supported CNTs/GO thin film as conductive element have the potential application as flexible and miniature electric carpet for heating micro‐/nano devices locally. A polymeric electrical carpet of 2D Janus hybrid thin film, with grafted polymer layer as insulative carpet and supported carbon materials as conductive element, has the potential application in heating micro‐/nano devices locally.
      PubDate: 2015-02-27T05:56:50.354035-05:
      DOI: 10.1002/adfm.201404624
  • Flexible Janus Nanoribbons Array: A New Strategy to Achieve Excellent
           Electrically Conductive Anisotropy, Magnetism, and Photoluminescence
    • Authors: Qianli Ma; Jinxian Wang, Xiangting Dong, Wensheng Yu, Guixia Liu
      Pages: 2436 - 2443
      Abstract: A new type of flexible Janus nanoribbons array with anisotropic electrical conductivity, magnetism, and photoluminescence has been successfully fabricated by electrospinning technology using a specially designed parallel spinneret. Every single Janus nanoribbon in the array consists of a half side of Fe3O4 nanoparticles/polyaniline/polymethylmethacrylate (PMMA) conductive‐magnetic bifunctionality and the other half side of Tb(BA)3phen/PMMA insulative‐photoluminescent characteristics, and all the Janus nanoribbons are aligned to form array. Owing to the unique nanostructure, the conductance along with the length direction of nanoribbons reaches up to eight orders of magnitude higher than that along with perpendicular direction, which is by far the most excellent conductive anisotropy for anisotropic conductive materials. The Janus nanoribbons array is also simultaneously endowed with magnetic and photoluminescent characteristics. The obtained Janus nanoribbons array will have important applications in the future subminiature electronic equipments owing to its high electrical anisotropy and multifunctionality. Furthermore, the design concept and fabrication technique for the flexible Janus nanoribbons array provide a new and facile approach for the preparation of anisotropic conductive films with multifunctionality. Novel Janus nanoribbons arrays with excellent electrically conductive anisotropy, magnetism, and photoluminescence are prepared via electrospinning technology. Based on the unique nanostructure, conductance in the direction parallel to the Janus nanoribbons is almost eight orders of magnitude higher than that in the perpendicular direction, which is by far the most excellent conductive anisotropy for anisotropic conductive materials.
      PubDate: 2015-03-12T09:44:30.545353-05:
      DOI: 10.1002/adfm.201500348
  • A Novel Bioinspired Switchable Adhesive with Three Distinct Adhesive
    • Authors: Paula Yagüe Isla; Elmar Kroner
      Pages: 2444 - 2450
      Abstract: A novel switchable adhesive, inspired by the gecko's fibrillar dry attachment system, is introduced. It consists of a patterned surface with an array of mushroom‐shaped pillars having two distinct heights. The different pillar heights allow control of the pull‐off force in two steps by application of a low and a high preload. For low preload, only the long pillars form contact, resulting in a low pull‐off force. At higher preload, all pillars form contact, resulting in high pull‐off force. Even further loading leads to buckling induced detachment of the pillars which corresponds to extremely low pull‐off force. To achieve the respective samples a new fabrication method called double inking is developed, to achieve multiple‐height pillar structures. The adhesion performance of the two‐step switchable adhesive is analysed at varying preload and for different pillar aspect ratios and height relations. Finally, the deformation behavior of the samples is investigated by in situ monitoring. Novel bioinspired, switchable adhesives with pillars of different length are successfully prepared, and allow control of the pull‐off force by means of preloading. Three distinct adhesive states are accessible. Adhesive properties are characterized by force–distance experiments and in situ observation of the deformation. Various applications, for example, in transportation, handling, and robotics, may benefit from the new bioinspired adhesive.
      PubDate: 2015-03-16T02:45:00.053554-05:
      DOI: 10.1002/adfm.201500241
  • Vinylogous Urethane Vitrimers
    • Authors: Wim Denissen; Guadalupe Rivero, Renaud Nicolaÿ, Ludwik Leibler, Johan M. Winne, Filip E. Du Prez
      Pages: 2451 - 2457
      Abstract: Vitrimers are a new class of polymeric materials with very attractive properties, since they can be reworked to any shape while being at the same time permanently cross‐linked. As an alternative to the use of transesterification chemistry, we explore catalyst‐free transamination of vinylogous urethanes as an exchange reaction for vitrimers. First, a kinetic study on model compounds reveals the occurrence of transamination of vinylogous urethanes in a good temperature window without side reactions. Next, poly(vinylogous urethane) networks with a storage modulus of ≈2.4 GPa and a glass transition temperature above 80 °C are prepared by bulk polymerization of cyclohexane dimethanol bisacetoacetate, m‐xylylene diamine, and tris(2‐aminoethyl)amine. The vitrimer nature of these networks is examined by solubility, stress‐relaxation, and creep experiments. Relaxation times as short as 85 s at 170 °C are observed without making use of any catalyst. In addition, the networks are recyclable up to four times by consecutive grinding/compression molding cycles without significant mechanical or chemical degradation. Catalyst‐free vitrimers based on the transamination of vinylogous urethanes are prepared from readily accessible chemicals. These high Tg, cross‐linked materials exhibit excellent mechanical properties, while the exchangeable bonds enable full stress‐relaxation on short time scales and recycling over many cycles.
      PubDate: 2015-03-13T05:48:40.95722-05:0
      DOI: 10.1002/adfm.201404553
  • Lab in a Tube: Purification, Amplification, and Detection of DNA Using
           Poly(2‐oxazoline) Multilayers
    • Authors: Meike N. Leiske; Matthias Hartlieb, Christian Paulenz, David Pretzel, Martin Hentschel, Christoph Englert, Michael Gottschaldt, Ulrich S. Schubert
      Pages: 2458 - 2466
      Abstract: Fast and easy purification and amplification of DNA are prerequisites for the development of point‐of‐care diagnostics. For this reason covalent coatings of amine containing poly(2‐oxazoline)s (POx) on glass and poly(propylene) surfaces are prepared, to reversibly bind genetic material directly from biological samples. The polymer is deposited in a layer‐by‐layer process, whereas initial immobilization of macromolecules on the surface is accomplished by the use of an epoxy functionalized siloxane monolayer. Alternating treatment with polymer and cross‐linker leads to the construction of amine containing POx multilayers on the substrates. Successful deposition is investigated by confocal laser scanning microscopy (using labeled polymers), contact angle measurements, as well as reflectometric interference spectroscopy. The interaction of these layer systems with DNA regarding binding and temperature dependent release is studied using labeled genetic material. Finally, polymerase chain reaction (PCR) vessels are coated with POx layers on the inside, and used for quantitative real‐time PCR (qPCR) experiments. It is possible to bind genetic material directly from cell lysates to perform qPCR assays from surface adsorbed DNA within the same tube including amplification, as well as detection. The presented system displays an easy to use device for a point of care diagnostic. Detection of DNA directly from biological material is performed by the use of covalently bound poly(2‐oxazoline) multilayers on polypropylene. Layer‐by‐layer assembly and interaction with genetic material is investigated in detail, and the amplification and detection of surface adsorbed DNA is performed by quantitative real‐time polymerase chain reaction using coated reaction vessels.
      PubDate: 2015-03-16T02:45:12.969826-05:
      DOI: 10.1002/adfm.201404510
  • Self‐Repairable, High Permittivity Dielectric Elastomers with Large
           Actuation Strains at Low Electric Fields
    • Authors: Simon J. Dünki; Yee Song Ko, Frank A. Nüesch, Dorina M. Opris
      Pages: 2467 - 2475
      Abstract: A one‐step process for the synthesis of elastomers with high permittivity, excellent mechanical properties and increased electromechanical sensitivity is presented. It starts from a high molecular weight polymethylvinylsiloxane, P1, whose vinyl groups serve two functions: the introduction of polar nitrile moieties by reacting P1 with 3‐mercaptopropionitrile (1) and the introduction of cross‐links to fine tune mechanical properties by reacting P1 with 2,2′‐(ethylenedioxy)diethanethiol (2). This twofold chemical modification furnished a material, C2, with a powerful combination of properties: permittivity of up to 10.1 at 104 Hz, elastic modulus Y10% = 154 kPa, and strain at break of 260%. Actuators made of C2 show lateral actuation strains of 20.5% at an electric field as low as 10.8 V μm–1. Additionally, such actuators can self‐repair after a breakdown, which is essential for an improved device lifetime and an attractive reliability. The actuators can be operated repeatedly and reversibly at voltages below the first breakdown. Due to the low actuation voltage and the large actuation strain applications of this material in commercial products might become reality. A one‐step process is presented for the synthesis of dielectric elastomers with permittivity of up to 10.1 at 10 kHz, Y(10%) = 154 kPa, and strain at break of 260%. Actuators made with them are able to self‐repair after a breakdown and show lateral strains of up to 20.5% at an electric field as low as 10.8 V µm–1.
      PubDate: 2015-03-16T02:45:05.804396-05:
      DOI: 10.1002/adfm.201500077
  • Thin Films: 2D Janus Hybrid Materials of Polymer‐Grafted Carbon
           Nanotube/Graphene Oxide Thin Film as Flexible, Miniature Electric Carpet
           (Adv. Funct. Mater. 16/2015)
    • Authors: Peng Xiao; Changjin Wan, Jincui Gu, Zhenzhong Liu, Yonghong Men, Youju Huang, Jiawei Zhang, Liqiang Zhu, Tao Chen
      Pages: 2479 - 2479
      Abstract: A 2D ultrathin Janus hybrid of polymer‐grafted CNTs/GO film is fabricated by Y. Huang, J. Zhang, T. Chen, and co‐workers on page 2428 using microcontact printed CNTs/GO as photo active surface to grow polymer brushes by self‐initiated photografting and photopolymerization selectively from one side of CNTs/GO film. The achieved 2D Janus hybrid materials, with polymer layer as insulative carpet and CNTs/GO thin film as conductive element, serve as flexible and miniature electric carpet for heating micro‐/nano devices locally.
      PubDate: 2015-04-21T05:49:29.918077-05:
      DOI: 10.1002/adfm.201570110
  • Drug Delivery: Remotely Controlled Red Blood Cell Carriers for Cancer
           Targeting and Near‐Infrared Light‐Triggered Drug Release in
           Combined Photothermal–Chemotherapy (Adv. Funct. Mater. 16/2015)
    • Authors: Xiaoqi Sun; Chao Wang, Min Gao, Aiyan Hu, Zhuang Liu
      Pages: 2480 - 2480
      Abstract: On page 2386 Z. Liu and colleagues introduce a tumor angiogenesis targeting, near‐infrared light stimulus‐response red blood cell (RBC)‐based drug delivery by incorporating various functional components within the RBC platform, for potential combined photothermal–chemotherapy of cancer.
      PubDate: 2015-04-21T05:49:34.65902-05:0
      DOI: 10.1002/adfm.201570111
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