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  Subjects -> CHEMISTRY (Total: 838 journals)
    - ANALYTICAL CHEMISTRY (48 journals)
    - CHEMISTRY (587 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (46 journals)
    - PHYSICAL CHEMISTRY (68 journals)

CHEMISTRY (587 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 5)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 32)
ACS Catalysis     Full-text available via subscription   (Followers: 28)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 15)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 10)
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: 203)
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: 11)
Advanced Functional Materials     Hybrid Journal   (Followers: 40)
Advanced Science Focus     Free   (Followers: 1)
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: 18)
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: 5)
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: 30)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 85)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 12)
American Journal of Chemistry     Open Access   (Followers: 19)
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: 20)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 142)
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: 6)
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: 11)
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: 23)
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: 141)
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: 3)
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)
C - Journal of Carbon Research     Open Access  
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)

        1 2 3 4 5 6 | Last

Journal Cover   Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [40 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1616-301X - ISSN (Online) 1616-3028
   Published by John Wiley and Sons Homepage  [1607 journals]
  • Three Dimensional Graphene Foam/Polymer Hybrid as a High Strength
           Biocompatible Scaffold
    • Authors: Andy Nieto; Rupak Dua, Cheng Zhang, Benjamin Boesl, Sharan Ramaswamy, Arvind Agarwal
      Abstract: Graphene foam (GrF)/polylactic acid–poly‐ε‐caprolactone copolymer (PLC) hybrid (GrF‐PLC) scaffold is synthesized in order to utilize both the desirable properties of graphene and that of foams such as excellent structural characteristics and a networked 3‐D structure for cells to proliferate in. The hybrid scaffold is synthesized by a dip‐coating method that enables retention of the porous 3D structure. The excellent wettability of PLC with graphene foam along with the formation of PLC bridges leads to a ≈3700% enhancement in strength and a ≈3100% increase in ductility in the GrF‐PLC scaffold. Biocompatibility of both graphene foam and GrF‐PLC scaffold is demonstrated by culturing of human mesenchymal stem cells (hMSCs) for 28 days, a period over which cell proliferation is robust. The hMSCs are differentiated in chondrogenic media and supported chondrogenesis in both scaffolds. The demand for aggrecan extracellular matrix protein synthesis is reduced in hybrids due to improved bearing of cell‐induced loads, this may be critical for ensuring adequate cellular distribution and layering of extracellular matrix. Hence, the unique mechanical and biotolerant properties of the GrF‐PLC scaffold are suited for musculoskeletal tissue engineering applications, such as the growth of de novo cartilage to replace cartilage lost due to injury or osteoarthritis. A novel 3D graphene foam (GrF)/PLC copolymer composite scaffold is synthesized by dip‐coating. GrF‐PLC scaffold retains porous 3D structure resulting in 3700% enhancement in strength and 3100% increase in ductility over pure GrF. The unique mechanical and biotolerant properties of the GrF‐PLC scaffold are studied by culturing of human mesenchymal stem cells for musculoskeletal tissue engineering applications.
      PubDate: 2015-05-20T01:59:43.807731-05:
      DOI: 10.1002/adfm.201500876
       
  • Unraveling the Reasons for Efficiency Loss in Perovskite Solar Cells
    • Authors: Yong Hui Lee; Jingshan Luo, Robin Humphry‐Baker, Peng Gao, Michael Grätzel, Mohammad Khaja Nazeeruddin
      Abstract: The effect of the presence of unreacted PbI2 on the perovskite solar cells efficiency is reported. N,N‐Dimethylformamide vapor treatment is introduced to study the influence of complete conversion to a power conversion efficiency of the device. It is discovered that the optimized morphology of the PbI2 under layer is essential to form a dense perovskite layer preventing recombination by direct contact between TiO2 and a hole transporting layer, and to increase the charge collection efficiency. The present findings provide an insight into the morphology and growth mechanism of perovskite layer, the correlation between the device performance, and the film deposition process. The influence of the unreacted PbI2 to the performance of perovskite solar cells is investigated. The optimized morphology of the PbI2 under layer is found to be essential to form a dense perovskite layer preventing recombination by direct contact between TiO2 and a hole transporting layer, and increase the charge collection efficiency.
      PubDate: 2015-05-20T01:58:31.677821-05:
      DOI: 10.1002/adfm.201501024
       
  • High‐Performance Olivine for Lithium Batteries: Effects of Ni/Co
           Doping on the Properties of LiFeαNiβCoγPO4 Cathodes
    • Authors: Gioele Pagot; Federico Bertasi, Graeme Nawn, Enrico Negro, Giorgio Carraro, Davide Barreca, Chiara Maccato, Stefano Polizzi, Vito Di Noto
      Abstract: New high voltage and high capacity storage systems are needed to sustain the increasing energy demand set by the portable electronics and auto­motive fields. Due to their good electrochemical performance, lithium‐transition metal‐phosphates (LiMPO4) seem to be very attractive as cathode materials for lithium secondary batteries. Here the synthesis and the characterization of five high voltage cathodes for lithium batteries, based on lithium–iron, lithium–nickel, lithium–cobalt phosphates are described. The effect of differing degrees of cobalt and nickel doping on structure, morphology, and the electrochemical properties of the different materials is thoroughly studied. Transition metal atoms in these materials are found to be vicariant within the olivine crystal structure; however, the lattice parameters and cell volume can be modulated by varying the nickel/cobalt ratio during the synthesis. High performance battery prototypes in terms of voltage (>4.0 V), specific capacity (125 mAh g−1), specific energy (560 mWh g−1), and cyclic life (>150 cycles) are also demonstrated. Five high voltage olivine cathodes for lithium batteries, based on lithium transition metal phosphates, are synthesized and characterized. The effect of differing degrees of cobalt and nickel doping on structure, morphology, and electrochemical properties of the different materials is studied; high performances in terms of voltage, specific capacity, specific energy, and cyclic life are obtained.
      PubDate: 2015-05-20T01:57:34.545301-05:
      DOI: 10.1002/adfm.201501167
       
  • Atomic Structure of Antiphase Nanodomains in Fe‐Doped SrTiO3 Films
    • Authors: Hongchu Du; Chun‐Lin Jia, Joachim Mayer, Juri Barthel, Christian Lenser, Regina Dittmann
      Abstract: The atomic structure of antiphase nanodomains in Fe‐doped SrTiO3 films is revealed directly by aberration‐corrected scanning transmission electron microscopy. In particular, the crystallographic translation vector between the antiphase nanodomains and the matrix is determined to be a/2 [0 1 1], distinct from a/2 [0 1 1] for the well‐known Ruddlesden–Popper (RP) planar faults in perovskite structure. The antiphase boundaries lie mostly in the {1 0 0} planes and partially in the {1 1 0} planes. The atomic structure of the antiphase boundaries is found to consist of chains of edge‐sharing TiO6 octahedra implying a local Ti‐enrichment, which is in strong contrast to local Sr‐enrichment at the RP type antiphase boundaries. Atomic structure of antiphase nano­domains in Fe‐doped SrTiO3 films is revealed by aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy. The crystallographic translation vector between the antiphase nanodomains and the matrix is found to be a/2 [0 1 1]. The antiphase boundaries lie mostly in the {1 0 0} planes and partially in the {1 1 0} planes forming chains of edge‐sharing TiO6 octahedra.
      PubDate: 2015-05-19T08:43:27.257174-05:
      DOI: 10.1002/adfm.201500852
       
  • Masthead: (Adv. Funct. Mater. 19/2015)
    • PubDate: 2015-05-18T13:11:14.961031-05:
      DOI: 10.1002/adfm.201570128
       
  • Chondroitin Sulfate‐Coated DNA‐Nanoplexes Enhance Transfection
           Efficiency by Controlling Plasmid Release from Endosomes: A New Insight
           into Modulating Nonviral Gene Transfection
    • Authors: Hongji Yan; Oommen P. Oommen, Di Yu, Jöns Hilborn, Hong Qian, Oommen P. Varghese
      Abstract: Degradation of plasmid DNA (pDNA) in the endosome compartment and its release to the cytosol are the major hurdles for efficient gene transfection. This is generally addressed by using transfection reagents that can overcome these limitations. In this article, the first report is presented which suggests that controlling the release of pDNA from endosome is the key for achieving efficient transfection. In this study, chondroitin sulfate (CS)‐coated DNA‐nanoplexes are developed using a modular approach where CS is coated post‐pDNA/PEI nanoplex formation. To ensure good stability of the nanoplexes, imine/enamine chemistry is exploited by reacting aldehyde‐modified chondroitin sulfate (CS‐CHO) with free amines of pDNA/PEI complex. This supramolecular nanocarrier system displays efficient cellular uptake, and controlled endosomal pDNA release without eliciting any cytotoxicity. On the contrary, burst release of pDNA from endosome (using chloroqine) results in significant reduction in gene expression. Unlike pDNA/PEI‐based transfection, the nanoparticle design presented here shows exceptional stability and gene transfection efficiency in different cell lines such as human colorectal cancer cells (HCT116), human embryonic kidney cells (HEK293), and mouse skin‐derived mesenchymal stem cells (MSCs) using luciferase protein as a reporter gene. This new insight will be valuable in designing next generation of transfection reagents. Preserving the integrity of plasmid DNA (pDNA) after endocytosis by promoting quick release of pDNA from endosome compartment is believed to be vital for gene transfection. In this article, the first evidence is presented that suggests that slow and sustained release of the pDNA from endosome is the key for achieving efficient transfection. This can be achieved by covalent coating of nanoplexes with chondroitin sulfate.
      PubDate: 2015-05-18T13:07:19.296308-05:
      DOI: 10.1002/adfm.201500695
       
  • Underlying Mechanism of Inkjet Printing of Uniform Organic Semiconductor
           Films Through Antisolvent Crystallization
    • Authors: Yuki Noda; Hiromi Minemawari, Hiroyuki Matsui, Toshikazu Yamada, Shunto Arai, Tadashi Kajiya, Masao Doi, Tatsuo Hasegawa
      Abstract: An underlying mechanism is reported for the formation of highly uniform crystalline organic semiconductor films by the double‐shot inkjet printing (IJP) technique utilizing antisolvent crystallization. It is demonstrated that the ability to form uniform films with this technique can be attributed to the unique nature of the initial contact dynamics between the chemically different microdroplets before occurrence of solute crystallization. Experiments are conducted systematically where a single microdroplet is over‐deposited by the IJP technique on a chemically different sessile droplet, for ten kinds of pure and miscible solvent combinations. The subsequent behavior is observed by high speed camera. The initial contact dynamics can be classified into three dramatically different cases that are respectively referred to as wetting, dewetting, and sinking. These phenomena are unique to microdroplets and the conditions for the occurrence of each type of phenomenon can be consistently explained by the fact that the initial contact dynamics are driven by the difference of surface tension of the liquids. Among the three kinds of dynamics, the wetting phenomenon creates a thin solution layer on the antisolvent droplet surface and can be used thus to manufacture uniform semiconductor films, where the coffee ring effect can be eliminated. Double‐shot inkjet printing utilizing antisolvent crystallization has the ability to form uniform organic semiconductor films, which, as demonstrated, is attributed to the unique nature of initial contact dynamics between chemically different microdroplets before occurrence of solute crystallization. Among three kinds of unique dynamics, the “wetting” can create a thin solution layer on antisolvent droplet surface, which eventually eliminates the coffee‐ring effect.
      PubDate: 2015-05-18T13:07:14.324903-05:
      DOI: 10.1002/adfm.201500802
       
  • Enhanced Charge Injection Through Nanostructured Electrodes for Organic
           Field Effect Transistors
    • Authors: Deyang Ji; Yandong Wang, Lifeng Chi, Harald Fuchs
      Abstract: Nanosphere lithography is used to process nanopore‐structured electrodes, which are applied into the fabrication of bottom‐gate, bottom‐contact configuration organic field effect transistors (OFETs) to serve as source/drain elecrodes. The introduction of this nanopore‐structure electrode facilitates the forming of nanopore‐structure pentacene layers with small grain boundaries at the electrode interface, and then reduces the contact resistance, contact‐induces the growth of pentacene and accordingly improves the mobility of charge carriers in the OFETs about 20 times as compared with results in literature through enhancing the charge carrier injection. It is believed that this structure of electrode is a valuable approach for improving organic filed effect transistors. Nanopore‐structured source/drain electro­des are introduced into fabricating bottom‐gate bottom‐contact configuration organic field effect transistors (OFETs) by nanosphere lithography. The introduction of this nanopore structure tremendously enhances the charge injection and accordingly improves the mobility of charge carriers in the OFETs about 20 times as compared with results in literature. It is believed that this structure of electrode is a valuable approach for improving organic filed effect transistors.
      PubDate: 2015-05-18T13:07:04.341422-05:
      DOI: 10.1002/adfm.201500771
       
  • Formation and Movement of Cationic Defects During Forming and Resistive
           Switching in SrTiO3 Thin Film Devices
    • Authors: Christian Lenser; Annemarie Koehl, Ivetta Slipukhina, Hongchu Du, Marten Patt, Vitaliy Feyer, Claus M. Schneider, Marjana Lezaic, Rainer Waser, Regina Dittmann
      Abstract: The resistance switching phenomenon in many transition metal oxides is described by ion motion leading to the formation of oxygen‐deficient, highly electron‐doped filaments. In this paper, the interface and subinterface region of electroformed and switched metal–insulator–metal structures fabricated from a thin Fe‐doped SrTiO3 (STO) film on n‐conducting Nb‐doped SrTiO3 crystals are investigated by photoemission electron microscopy, transmission electron microscopy, and hard X‐ray photoelectron spectroscopy in order to gain a deeper understanding of cation movement in this specific system. During electroforming, the segregation of Sr to the top interface and the generation of defect‐rich cones in the film are observed, apparently growing from the anode toward the cathode during electroforming. An unusual binding energy component of the Sr 3d emission line is observed which can be assigned to Sr″Ti−VO** defect complexes by performing ab initio calculations. Since this Sr component can be reversibly affected by an external electrical bias, the movement of both oxygen and Sr point defects and the formation of defect complexes Sr″Ti−VO** during resistive switching are suggested. These findings are discussed with regard to the point defect structure of the film and the local oxidation of the donor‐doped substrate. In particular, the apparent dichotomy between the observation of acceptor‐type defects and increased electronic conductivity in STO is addressed. A low binding energy component of the Sr 3d photoemission line is observed in Fe‐doped SrTiO3 memristive devices and assigned to Sr″Ti−VO** defect complexes by ab initio calculations. Since this Sr component can be reversibly affected by an electrical bias, the movement of both oxygen and Sr vacancies and the formation of Sr″Ti−VO** defect complexes during resistive switching are suggested.
      PubDate: 2015-05-18T13:06:59.835103-05:
      DOI: 10.1002/adfm.201500851
       
  • Cell‐Membrane‐Coated Synthetic Nanomotors for Effective
           Biodetoxification
    • Authors: Zhiguang Wu; Tianlong Li, Wei Gao, Tailin Xu, Beatriz Jurado‐Sánchez, Jinxing Li, Weiwei Gao, Qiang He, Liangfang Zhang, Joseph Wang
      Abstract: A red blood cell membrane‐camouflaged nanowire that can serve as new generation of biomimetic motor sponge is described. The biomimetic motor sponge is constructed by the fusion of biocompatible gold nanowire motors and RBC nanovesicles. The motor sponge possesses a high coverage of RBC vesicles, which remain totally functional due to its exclusively oriented extracellular functional portion on the surfaces of motor sponge. These biomimetic motors display efficient acoustical propulsion, including controlled movement in undiluted whole blood. The RBC vesicles on the motor sponge remain highly stable during the propulsion process, conferring thus the ability to absorb membrane‐damaging toxins and allowing the motor sponge to be used as efficient toxin decoys. The efficient propulsion of the motor sponges under an ultrasound field results in accelerated neutralization of the membrane‐damaging toxins. Such motor sponges connect artificial nano­motors with biological entities and hold great promise for treating a variety of injuries and diseases caused by membrane‐damaging toxins. A red blood cell membrane‐coated nano­wire that can function as a biomimetic motor sponge is presented. The unique membrane coating and powerful ultrasound propulsion allow it to serve as a moving toxin decoy to efficiently remove membrane‐damaging toxins. Such motor sponges bridge artificial nanomotors with biological entities and hold great promise for treating injuries and diseases caused by membrane‐damaging toxin.
      PubDate: 2015-05-15T14:29:01.926297-05:
      DOI: 10.1002/adfm.201501050
       
  • A High‐Performance Nitro‐Explosives Schottky Sensor Boosted by
           Interface Modulation
    • Authors: Zheng Yang; Xincun Dou, Shengli Zhang, Linjuan Guo, Baiyi Zu, Zhaofeng Wu, Haibo Zeng
      Abstract: A high‐performance Schottky sensor boosted by interface modulation is fabricated for the detection of trace nitro‐explosives vapors. The interface modulation strategy results in a silicon nanowires (SiNWs) array/TiO2/reduced graphene oxide (rGO) sensor with sensitive and selective response toward nitro‐explosives vapors. The response of the SiNWs array/TiO2/rGO sensor toward nitro‐explosives vapors, such as 9 ppb 2,4,6‐trinitrotoluene, 4.9 ppt hexogen, and 0.25 ppq octagon, is boosted by 2.4, 7.5, and 5 times with the insertion of TiO2. Superior selectivity is shown even compared with interfering gases of 10 ppm. Such good sensing performance can be attributed to the good sensing performance of the Schottky heterojunction‐based sensor, the Schottky barrier height modulation with the insertion of TiO2, SiNWs array structure enhanced diffusion, and TiO2 nanoparticles enhanced adsorption. This is believed to be the first Schottky heterojunction‐based sensor for nitro‐explosives vapors detection. This work would open a new way to develop highly sensitive and selective sensors. A high‐performance Schottky sensor is fabricated for the detection of trace nitro‐explosives vapors. The sensitivity of the silicon nanowires array/TiO2/rGO sensor is boosted with the insertion of TiO2. Superior selectivity is shown even compared with interfering gases of 10 ppm.
      PubDate: 2015-05-15T14:28:57.169199-05:
      DOI: 10.1002/adfm.201501120
       
  • Metal‐Phosphide‐Containing Porous Carbons Derived from an
           Ionic‐Polymer Framework and Applied as Highly Efficient
           Electrochemical Catalysts for Water Splitting
    • Authors: Sheng Han; Yunlong Feng, Fan Zhang, Chongqing Yang, Zhaoquan Yao, Wuxue Zhao, Feng Qiu, Lingyun Yang, Yefeng Yao, Xiaodong Zhuang, Xinliang Feng
      Abstract: A novel phosphorus‐containing porous polymer is efficiently prepared from tris(4‐vinylphenyl)phosphane by radical polymerization, and it can be easily ionized to form an ionic porous polymer after treatment with hydrogen iodide. Upon ionic exchange, transition‐metal‐containing anions, such as tetrathiomolybdate (MoS4 2−) and hexacyanoferrate (Fe(CN)6 3−), are successfully loaded into the framework of the porous polymer to replace the original iodide anions, resulting in a polymer framework containing complex anions (termed HT‐Met, where Met = Mo or Fe). After pyrolysis under a hydrogen atmosphere, the HT‐Met materials are efficiently converted at a large scale to metal‐phosphide‐containing porous carbons (denoted as MetP@PC, where again Met = Mo or Fe). This approach provides a convenient pathway to the controlled preparation of metal‐phosphide‐loaded porous carbon composites. The MetP@PC composites exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) under acidic conditions. In particular, MoP@PC with a low loading of 0.24 mg cm−2 (on a glass carbon electrode) affords an iR‐corrected (where i is current and R is resistance) current density of up to 10 mA cm−2 at 51 mV versus the reversible hydrogen electrode and a very low Tafel slope of 45 mV dec−1, in rotating disk measurements under saturated N2 conditions. Metal‐phosphide‐loaded porous carbons (MetP@PCs) are prepared from a phosphorous‐containing ionic‐polymer framework. Unlike previously reported transition‐metal‐based electrocatalysts, the metal source for MetP@PCs are complex ions, rather than metal salts. Their performance in the electrochemical catalysis of the hydrogen evolution reaction is very promising, and the performance of the PC loaded with molybdenum phosphide is comparable with that of the commercial Pt/C catalyst.
      PubDate: 2015-05-15T14:28:34.798108-05:
      DOI: 10.1002/adfm.201501390
       
  • Tissue Adhesive Catechol‐Modified Hyaluronic Acid Hydrogel for
           Effective, Minimally Invasive Cell Therapy
    • Authors: Jisoo Shin; Jung Seung Lee, Changhyun Lee, Hyun‐Ji Park, Kisuk Yang, Yoonhee Jin, Ji Hyun Ryu, Ki Sung Hong, Sung‐Hwan Moon, Hyung‐Min Chung, Hee Seok Yang, Soong Ho Um, Jong‐Won Oh, Dong‐Ik Kim, Haeshin Lee, Seung‐Woo Cho
      Abstract: Current hyaluronic acid (HA) hydrogel systems often cause cytotoxicity to encapsulated cells and lack the adhesive property required for effective localization of transplanted cells in vivo. In addition, the injection of hydrogel into certain organs (e.g., liver, heart) induces tissue damage and hemorrhage. In this study, we describe a bioinspired, tissue‐adhesive hydrogel that overcomes the limitations of current HA hydrogels through its improved biocompatibility and potential for minimally invasive cell transplantation. HA functionalized with an adhesive catecholamine motif of mussel foot protein forms HA‐catechol (HA‐CA) hydrogel via oxidative crosslinking. HA‐CA hydrogel increases viability, reduces apoptosis, and enhances the function of two types of cells (human adipose‐derived stem cells and hepatocytes) compared with a typical HA hydrogel crosslinked by photopolymerization. Due to the strong tissue adhesiveness of the HA‐CA hydrogel, cells are easily and efficiently transplanted onto various tissues (e.g., liver and heart) without the need for injection. Stem cell therapy using the HA‐CA hydrogel increases angiogenesis in vivo, leading to improved treatment of ischemic diseases. HA‐CA hydrogel also improved hepatic functions of transplanted hepatocytes in vivo. Thus, this bioinspired, tissue‐adhesive HA hydrogel can enhance the efficacy of minimally invasive cell therapy. Bioinspired, catechol‐modified hyaluronic acid (HA) hydrogel is highly biocompatible and exhibits improved tissue adhesiveness in comparison to HA hydrogel crosslinked via photopolymerization. Tissue adhesive catechol‐modified HA hydrogel can mediate highly effective, minimally invasive cell therapy in defected models such as liver resection and myocardial infarction.
      PubDate: 2015-05-15T08:56:25.761128-05:
      DOI: 10.1002/adfm.201500006
       
  • Highly Conductive, Bendable, Embedded Ag Nanoparticle Wire Arrays Via
           Convective Self‐Assembly: Hybridization into Ag Nanowire Transparent
           Conductors
    • Authors: Dong Yun Choi; Yong Suk Oh, Donggeon Han, Seunghyup Yoo, Hyung Jin Sung, Sang Soo Kim
      Abstract: The optoelectrical properties of Ag nanowire (NW) networks are improved by incorporating the NWs into highly conductive ordered arrays of Ag nanoparticle wires (NPWs) fabricated via surfactant‐assisted convective self‐assembly. The NPW–NW hybrid conductor displays a transmittance (T) of 90% at 550 nm and a sheet resistance (R s) of 5.7 Ω sq−1, which is superior to the corresponding properties of the NW network showing a R s of 14.1 Ω sq−1 at a similar T. By the modified wettability of a donor substrate and the capillarity of water, the sintered NPW–NW hybrid conductors are perfectly transferred onto an UV‐curable photopolymer film, and the embedded hybrid conductors exhibit excellent electromechanical properties. The R s and T of the NPW arrays can be predicted by using a simple model developed to calculate the width and height of the hexagonal close‐packed particles formed during the convective self‐assembly. The numerical analysis reveals that the maximum Haacke figure of merit of the NW networks is increased considerably from 0.0260 to 0.0407 Ω−1 by integration with the NPW array. The highly conductive NPW arrays generated using a simple, low‐cost, and nonlithographic process can be applied to enhancing the performances of other transparent conductors, such as carbon nanotubes, metal oxides, and graphenes. Well‐organized and highly conductive Ag nanoparticle wire arrays are realized using the surfactant‐assisted convective self‐assembly. A thermally sintered hybrid structure of nanoparticle wire array and nanowire network is reliably transferred into a transparent polymer matrix, which shows extremely good optoelectrical and electromechanical properties. The nanoparticle wire arrays can be applied to improve the performance of other transparent conductors or electronic devices.
      PubDate: 2015-05-15T08:56:08.777643-05:
      DOI: 10.1002/adfm.201500677
       
  • Metal–Organic Frameworks with Boronic Acid Suspended and Their
           Implication for cis‐Diol Moieties Binding
    • Authors: Xiangyang Zhu; Jinlou Gu, Junying Zhu, Yongsheng Li, Liming Zhao, Jianlin Shi
      Abstract: Introduction of accessible boronic acid functionality into metal–organic frameworks (MOFs) might to endow them with desired properties for potential applications in recognition and isolation of cis‐diol containing biomolecules (CDBs). However, no investigation is found to address this topic until now. Herein, Cr‐based MOFs of MIL‐100 (MIL stands for Materials from Institut Lavoisier) integrated with different pendent boronic acid group (MIL‐100‐B) are reported. This new functional material is successfully prepared using a simple metal–ligand–fragment coassembly (MLFC) strategy with isostructure to the parent MIL‐100 as verified by X‐ray diffraction characterization. The integration and content tunability of the boronic acid group in the framework are confirmed by X‐ray photoelectron spectroscopy and 11B NMR. Transmission electron microscopy reveals that MIL‐100‐B can evolve into well‐defined morphology and nanoscale size at optimized boronic acid incorporating level. The obtained MOFs exhibit comparable surface areas and pore volumes with parent MIL‐100 and present exceptional chemical stability in a wide pH range. The inherent boronic acid components in MIL‐100‐B can effectively serve as the recognition units for the cis‐diol moieties and consequently enhance the capture capabilities for CDBs. The exceptional chemical stability, high porosity, and good reusability as well as the intrinsic cis‐diol moieties recognition function prefigure great potential of the current MIL‐100‐B in CDBs purification, sensing, and separation applications. Introduction of accessible boronic acid functionality into metal–organic frameworks is successfully achieved using a facile linker fragmentation strategy. In virtue of their accessible boronic acid groups, exceptional chemical stability, as well as high porosity, the newly elaborated functional material offers a new platform for the recognition and separation of cis‐diol containing biomolecules.
      PubDate: 2015-05-15T08:56:02.91853-05:0
      DOI: 10.1002/adfm.201500587
       
  • Layer‐by‐Layer Conjugated Extension of a Semiconducting
           Polymer for High‐Performance Organic Field‐Effect Transistor
    • Authors: Mi Jang; Se Hyun Kim, Han‐Koo Lee, Yun‐Hi Kim, Hoichang Yang
      Abstract: A donor–acceptor (D–A) semiconducting copolymer, PDPP‐TVT‐29, comprising a diketopyrrolopyrrole (DPP) derivative with long, linear, space‐separated alkyl side‐chains and thiophene vinylene thiophene (TVT) for organic field‐effect transistors (OFETs) can form highly π‐conjugated structures with an edge‐on molecular orientation in an as‐spun film. In particular, the layer‐like conjugated film morphologies can be developed via short‐term thermal annealing above 150 °C for 10 min. The strong intermolecular interaction, originating from the fused DPP and D–A interaction, leads to the spontaneous self‐assembly of polymer chains within close proximity (with π‐overlap distance of 3.55 Å) and forms unexpectedly long‐range π‐conjugation, which is favorable for both intra‐ and intermolecular charge transport. Unlike intergranular nanorods in the as‐spun film, well‐conjugated layers in the 200 °C‐annealed film can yield more efficient charge‐transport pathways. The granular morphology of the as‐spun PDPP‐TVT‐29 film produces a field‐effect mobility (μ FET) of 1.39 cm2 V−1 s−1 in an OFET based on a polymer‐treated SiO2 dielectric, while the 27‐Å‐step layered morphology in the 200 °C‐annealed films shows high μ FET values of up to 3.7 cm2 V−1 s−1. A donor–acceptor diketopyrrolopyrrole derivative copolymer with long, linear, space‐separated alkyl side chains and thiophene vinylene thiophene can form percolated nanogranules of edge‐on molecules in an as‐spun film. Thermal annealing at 200 °C for 10 min yields a layered morphology with 27 Å steps and π‐overlap of 3.55 Å; the resulting organic field‐effect transistor (OFET) has μ FET as high as 3.7 cm2 V−1 s−1.
      PubDate: 2015-05-15T08:46:52.4968-05:00
      DOI: 10.1002/adfm.201403497
       
  • Rapid Thiol‐Yne‐Mediated Fabrication and Dual
           Postfunctionalization of Micro‐Resolved 3D Mesostructures
    • Authors: Alexander S. Quick; Andres de los Santos Pereira, Michael Bruns, Tiemo Bückmann, Cesar Rodriguez‐Emmenegger, Martin Wegener, Christopher Barner‐Kowollik
      Abstract: 3D mesostructures with a height of up to 1 mm and micrometer feature size are fabricated employing a writing speed of 1 cm s−1 via direct laser writing utilizing a novel functional photoresist based on the radical coupling reaction of thiols and alkynes. The refractive index of the resist—consisting of a tetrafunctional thiol, a tetrafunctional alkyne and a photoinitiator—is tailored to be compatible with the employed high numerical aperture (NA) objective lens, thus enabling a Dip‐in configuration. Mesostructures are characterized by scanning electron microscopy, optical photography, and nondestructive 3D time‐of‐flight secondary ion mass spectrometry. Woodpile photonic crystals are fabricated as benchmark structures in order to investigate the axial resolution. Verification of the chemical fabrication mechanism is achieved via transmission Fourier transform infrared (FTIR) spectroscopy of fabricated cuboid structures by monitoring the decrease of corresponding thiol and alkyne absorption peaks. Postmodification reactions, namely the thiol‐Michael addition and the copper‐catalyzed azide alkyne cycloaddition, are conducted employing residual thiols and alkynes throughout the cuboid structures. Successful dual and orthogonal modification throughout the structure and on the surface is achieved and verified utilizing transmission FTIR spectroscopy and time‐of‐flight secondary ion mass spectrometry. Reactive 3D mesostructures with micrometer feature size are fabricated via dip‐in direct laser writing employing the radical thiol‐yne coupling reaction. Axial resolution and the polymerization process of the photoresist are investigated. Residual thiols and alkynes are exploited for postmodification reactions, namely thiol‐Michael addition and copper‐catalyzed azide alkyne cycloaddition, demonstrating successful dual functionalization throughout the structure and on the surface.
      PubDate: 2015-05-15T08:25:31.937772-05:
      DOI: 10.1002/adfm.201500683
       
  • Controllable Broadband Absorption in the Mixed Phase of Metamagnets
    • Authors: Matej Pregelj; Oksana Zaharko, Andrej Zorko, Matjaž Gomilšek, Oles Sendetskyi, Axel Günther, Mykhaylo Ozerov, Sergei A. Zvyagin, Hubertus Luetkens, Christopher Baines, Vladimir Tsurkan, Alois Loidl
      Abstract: Materials with broad absorption bands are highly desirable for electromagnetic filtering and processing applications, especially if the absorption can be externally controlled. Here, a new class of broadband‐absorption materials is introduced. Namely, layered metamagnets exhibit an electromagnetic excitation continuum in the magnetic‐field‐induced mixed ferro‐ and anti­ferromagnetic phase. Employing a series of complementary experimental techniques involving neutron scattering, muon spin relaxation, specific heat, ac and dc magnetization measurements, and electron magnetic resonance, a detailed magnetic phase diagram of Cu3Bi(SeO3)2O2Br is determined and it is found that the excitations in the mixed phase extend over at least ten decades of frequency. The results, which reveal a new dynamical aspect of the mixed phase in metamagnets, open up a novel approach to controllable microwave filtering. Controllable broadband microwave absorption is highly desired for improved electromagnetic shielding and superior signal processing. The absorption of the microwaves in an extremely wide frequency range is demonstrated in layered metamagnets. The effect is controlled by the external magnetic field and should be easily reproduced in artificial metamagnets, that is, magnetic multilayers, allowing a direct tuning of the functional properties.
      PubDate: 2015-05-15T08:25:24.663236-05:
      DOI: 10.1002/adfm.201500702
       
  • Resistive Switching of a Quasi‐Homogeneous Distribution of Filaments
           Generated at Heat‐Treated TiO2 (110)‐Surfaces
    • Authors: Maciej Rogala; Gustav Bihlmayer, Wolfgang Speier, Zbigniew Klusek, Christian Rodenbücher, Krzysztof Szot
      Abstract: Resistive switching of thermally treated rutile single crystals with (110) orientation is studied. A heat treatment procedure is developed that involves reduction and oxidation steps and allows to induce low resistance states in switchable regions at the surface by low‐voltage electrical stimulation with the conducting tip of an atomic force microscope. This way, it is possible to electrically imprint quasi‐homogeneous switchable regions over several square micrometers. These regions are identified to consist of nanofilaments crossing the surface with a density of around 1012 cm−2, much higher in density than observed for single crystals so far. Experimental evidence is given that these nanofilaments are not related to inherent structural imperfections such as dislocations, but may originate from the linear agglomeration of oxygen vacancies as predicted by theory. Ab initio calculations and electrical simulations are performed to analyze the filamentary structures and their network in the effort to explain the observed filamentary switching of heat‐treated single‐crystalline TiO2. The resistive switching of TiO2 crystals is studied. The phenomena occurring in this material prospective to memory devices are related to nanofilamentary structures generated by the thermal treatment. Experimental evidence is given that the observed nanofilaments may originate from the linear agglomeration of oxygen vacancies as predicted by theory and confirmed by presented ab initio calculations and electrical simulations.
      PubDate: 2015-05-15T08:25:18.570357-05:
      DOI: 10.1002/adfm.201500855
       
  • Electrically Driven Random Laser Memory
    • Authors: Cih‐Su Wang; Chuan‐Hsien Nieh, Tai‐Yuan Lin, Yang‐Fang Chen
      Abstract: The first electrically driven random laser diode with nonvolatile resistive random access memory functionality is designed and demonstrated. To illustrate the working principle, a metal–insulator–semiconductor structure based on Pt/MgO/ZnO thin‐film layers is fabricated on indium tin oxide glass. The current–voltage curve of the dual‐function random laser memory (RLM) device exhibits an excellent electrical bistability with a high ON/OFF current ratio (≈107). The random lasing behavior is simultaneously demonstrated by using electrical pumping with the appearance of sharp‐peak emissions and a drastic enhancement of peak intensity. A wide angle‐dependent electroluminescence not only reveals its emitting advantage but also further supports the origin of random lasers. The first proof‐of‐concept presentation of RLM possesses several advantages of dual memory and lasing functions, which enables to open up new avenues to practical applications, such as light emitting memories for electrical and optical communication. This new horizon for the realization of all optical memories should therefore be able to attract academic as well as industrial interests. It is stressed here that the electrical reading of conventional memory array is usually in serial sequence, which limits the maximum data throughput. This hurdle can be overcome by optically readable memory devices. Electrically driven random laser memory (RLM) diodes based on Pt/MgO/ZnO/ITO structure are fabricated. Both the random laser action and nonvolatile resistive random access memory functionality are well demonstrated. The dual functional RLM device paves a new route to advance the traditional memories using electrical detection toward faster parallel optical reading processes.
      PubDate: 2015-05-15T08:25:11.871194-05:
      DOI: 10.1002/adfm.201500734
       
  • Soft Core/Shell Packages for Stretchable Electronics
    • Authors: Chi Hwan Lee; Yinji Ma, Kyung‐In Jang, Anthony Banks, Taisong Pan, Xue Feng, Jae Soon Kim, Daeshik Kang, Milan S. Raj, Bryan L. McGrane, Briana Morey, Xianyan Wang, Roozbeh Ghaffari, Yonggang Huang, John A. Rogers
      Abstract: This paper presents materials and core/shell architectures that provide optimized mechanical properties in packages for stretchable electronic systems. Detailed experimental and theoretical studies quantitatively connect the geometries and elastic properties of the constituent materials to the overall mechanical responses of the integrated systems, with a focus on interfacial stresses, effective modulus, and maximum extent of elongation. Specific results include core/shell designs that lead to peak values of the shear and normal stresses on the skin that remain less than 10 kPa even for applied strains of up to 20%, thereby inducing minimal somatosensory perception of the device on the human skin. Additional, strain‐limiting mesh structures embedded in the shell improve mechanical robustness by protecting the active components from strains that would otherwise exceed the fracture point. Demonstrations in precommercial stretchable electronic systems illustrate the utility of these concepts. Human skin‐like core/shell material structure is presented for use in wearable, stretchable electronic systems. Here, an ultralow‐modulus elastomer (core) with a thin enclosure (shell) serves to minimize interface stresses and mechanical constraints on natural motions, with ability to strain‐isolate the electronics. Demonstration examples exploit emerging commercial classes of stretchable electronic system to wirelessly monitor a subject's motions and body temperatures during exercise.
      PubDate: 2015-05-15T08:24:55.411418-05:
      DOI: 10.1002/adfm.201501086
       
  • Self‐Healing Actuating Adhesive Based on Polyelectrolyte Multilayers
    • Authors: Yuanqing Gu; Nicole S. Zacharia
      Abstract: Creating actuators capable of mechanical motion in response to external stimuli is a key for design and preparation of smart materials. The lifetime of such materials is limited by their eventual wear. Here, self‐healable and adhesive actuating materials are demonstrated by taking advantage of the solvent responsive of weak polyelectrolyte multilayers consisting of branched poly(ethylenimine)/poly(acrylic acid) (BPEI/PAA). BPEI/PAA multilayers are dehydrated and contract upon contact with organic solvent and become sticky when wetted with water. By constructing an asymmetric heterostructure consisting of a responsive BPEI/PAA multilayer block and a nonresponsive component through either layer‐by‐layer assembly or the paste‐to‐curl process, smart films that actuate upon exposure to alcohol are realized. The curl degree, defined as degrees from horizontal that the actuated material reaches, can be as high as ≈228.9°. With evaporation of the ethanol, the curled film returns to its initial state, and water triggers fast self‐healing extends the actuator's lifetime. Meanwhile, the adhesive nature of the wet material allows it to be attached to various substrates for possible combination with hydrophobic functional surfaces and/or applications in biological environments. This self‐healable adhesive for controlled fast actuation represents a considerable advance in polyelectrolyte multilayers for design and fabrication of robust smart advanced materials. Self‐healable adhesive that actuates upon exposure to ethanol is developed by layer‐by‐layer assembly and paste‐to‐curl approaches. The degree of curling is easily controlled by controlling exposure to the organic solvent stimulus as well as engineering the thickness and modulus of the inert part of the actuator. The branched poly(ethylenimine)/poly(acrylic acid) film, which is the active component, can easily be self‐healed in water, prolonging lifetime of the actuator.
      PubDate: 2015-05-15T08:24:48.560703-05:
      DOI: 10.1002/adfm.201501055
       
  • Remarkable Turn‐On and Color‐Tuned Piezochromic Luminescence:
           Mechanically Switching Intramolecular Charge Transfer in Molecular
           Crystals
    • Authors: Qingkai Qi; Jingyu Qian, Xiao Tan, Jibo Zhang, Lijuan Wang, Bin Xu, Bo Zou, Wenjing Tian
      Abstract: The molecular crystals of acridonyl‐tetraphenylethene (AD‐TPE) exhibit an intriguing turn‐on and color‐tuned luminescence in response to mechanical grinding and hydrostatic compression. On the basis of in‐depth experimental and computational studies, it is hypothesized that the origin of the piezochromic behavior from the D‐phase to the B‐phase is the change of the intramolecular geometrical conformation, especially for the torsion angle between the TPE and AD moiety. The different molecular conformation in the two distinctive solid phases causes the substantial switching of the intra­molecular charge transfer (ICT) process, which can be directly correlated with the subsequent fluorescence from locally excited (LE) state and ICT state in both phases. The AD‐TPE molecular system presents a very rare example of high‐contrast reversible fluorescence tuning driven by a switching of the excited state in the solid state under the mechanical stimuli, and thus provides a novel mechanism of the piezochromic behavior. Tuning the solid state luminescence of organic materials under mechanical stimuli is an attractive subject for both the fundamental research and practical application in the optical recording and sensing. Herein, a structurally well‐defined molecule, acridonyl‐tetraphenylethene is reported, whose molecular crystals exhibit an intriguing turn‐on and color‐tuned luminescence with high contrast in response to the mechanical stimuli such as grinding and hydrostatic pressure.
      PubDate: 2015-05-15T08:24:23.206906-05:
      DOI: 10.1002/adfm.201501224
       
  • Mussel Byssus‐Like Reversible Metal‐Chelated Supramolecular
           Complex Used for Dynamic Cellular Surface Engineering and Imaging
    • Authors: Wen Li; Wei Bing, Sa Huang, Jinsong Ren, Xiaogang Qu
      Abstract: Inspired by the load‐bearing biostructures in nature, a multifunctional shell for encapsulating cell using the polyphenol–metal complexes is fabricated. The artificial shell is formed by cross‐linking of tannic acid and iron ion on cell surface. It can protect cells from unfriendly environments, including UV light irradiation and reactive oxygen damage. With the hybrid property of polyphenol and metal liands, the shell provides a versatile platform for cell surface engineering. The magnetic nanoparticles, DNA molecules, as well as the magnetic resonance imaging agents are easily incorporated into the shell. More interestingly, unlike the traditional passive coatings, here the shell can be controllably disassembled under external stimuli. The dynamic coating is used as a reversible element to regulate cell division and surface modification. The cell viability and protein expression experiments further confirm that the shell formation and degradation processes are biocompatible. This multifunctional coating strategy is applicable to multiple living cell types, including yeast cells, Escherichia coli bacteria, and mammalian cells. Therefore, this platform would be useful for living cell based fundamental research and biological applications. Inspired by nature, herein a versatile strategy is reported for encapsulating cells with polyphenolic metal coordination‐based shell. The shell provides powerful tools for simultaneously protecting cells and engineering cell surface with nanoparticles, bioactive molecules, and imaging agents. In addition, in contrast to traditional passive shell, the coating here could be on‐demand removed with stimuli to evoke the original feature of cells.
      PubDate: 2015-05-13T15:13:00.38641-05:0
      DOI: 10.1002/adfm.201500039
       
  • Facile Fabrication of Robust Organic Counterion‐Induced Vesicles:
           Reversible Thermal Behavior for Optical Temperature Sensor and Synergistic
           Catalyst upon Removal of Amine
    • Authors: Chuanqi Li; Shiyong Zhang, Jie Pang, Yao Wu, Zhongwei Gu
      Abstract: A general concept of organic counterion‐directed molecular strategy for thepreparation of robust vesicles is developed. Functional amphiphilic ammonium salts (L1‐L3) bearing readily available oligo‐ethyleneglycol‐based ligand 1 and single‐tailed fatty amines self‐assemble into vesicles with controllable sizes in aqueous media. The organic counterion‐induced vesicles (OCIVs) are characterized by dynamic light scattering, transmission electron microscopy, and acid triggered release of hydrophilic drug (DOX·HCl). The introduction of organic counterion not only plays an important role in vesicle construction, but also endows the material with greatly practical values. By virtue of alkynyl groups attached on the organic ligand, the OCIVs can be easily cross‐linked via thiol‐ene reaction to generate a robust material. Importantly, the cross‐linked OCIVs exploit reversible temperature‐dependant size change, which can be repeated over 10 times without appreciable size fluctuating. Based on the unique property, a robust luminescence temperature sensor with a useful detection range of 35–70 °C is developed. Besides, removing the amines buried in the polymerized OCIVs under acidic condition, the resulting carboxylic acid‐functionalized material is found to have unusual efficiency as “nanozyme” for acetal hydrolysis, which exhibits over 20‐fold rate acceleration compared with that catalyzed by 1 or benzoic acid. A general concept of organic counterion‐induced vesicles is established. The introduction of organic counterion not only plays an important role in vesicle construction, but also endows the material with greatly practical values. As examples, a robust luminescence temperature sensor and a highly efficient synergistic catalyst are developed successfully.
      PubDate: 2015-05-13T15:12:42.80367-05:0
      DOI: 10.1002/adfm.201500176
       
  • Formation of Bi2WO6 Bipyramids with Vacancy Pairs for Enhanced
           Solar‐Driven Photoactivity
    • Authors: Gong Zhang; Ziyu Hu, Meng Sun, Yang Liu, Limin Liu, Huijuan Liu, Chin‐Pao Huang, Jiuhui Qu, Jinghong Li
      Abstract: In order to improve the photoactivity, many attempts have focused on increasing the exposure of highly reactive surfaces on crystals. However, the connection between the reactive surfaces and enhancement is still elusive. Herein, Bi2WO6 nanostructured bipyramids with a large fraction of {100} facets are fabricated by the solvothermal method. The formation of “Bi–O” dimer vacancy pairs on the {100} high‐energy facets is responsible for the reduction in band gap and the decrease in the recombination of photo‐excited charge carriers, which is unambiguously confirmed by the positron annihilation spectra (PAS), X‐ray photoelectron spectrum (XPS), and theoretical calculations. The effective separation of electron–hole pairs and the narrowing bandgap significantly improve the photoactivity of Bi2WO6 nanobipyramids, especially under solar light irradiation. These findings can be applied broadly to the design and fabrication of energy efficient and robust catalysts. Bi2WO6 nanobipyramid is fabricated via a facile strategy successfully, in which “Bi–O” vacancy pairs are key to increase its solar‐light photoactivity.
      PubDate: 2015-05-13T15:12:34.571741-05:
      DOI: 10.1002/adfm.201501009
       
  • Configurable Resistive Switching between Memory and Threshold
           Characteristics for Protein‐Based Devices
    • Authors: Hong Wang; Yuanmin Du, Yingtao Li, Bowen Zhu, Wan Ru Leow, Yuangang Li, Jisheng Pan, Tao Wu, Xiaodong Chen
      Abstract: The employ of natural biomaterials as the basic building blocks of electronic devices is of growing interest for biocompatible and green electronics. Here, resistive switching (RS) devices based on naturally silk protein with configurable functionality are demonstrated. The RS type of the devices can be effectively and exactly controlled by controlling the compliance current in the set process. Memory RS can be triggered by a higher compliance current, while threshold RS can be triggered by a lower compliance current. Furthermore, two types of memory devices, working in random access and WORM modes, can be achieved with the RS effect. The results suggest that silk protein possesses the potential for sustainable electronics and data storage. In addition, this finding would provide important guidelines for the performance optimization of biomaterials based memory devices and the study of the underlying mechanism behind the RS effect arising from biomaterials. Resistive switching (RS) devices with configurable functionality based on protein are successfully achieved. By controlling the compliance current in the set process, the types of RS (memory and threshold RS) can be effectively and exactly controlled. In addition, two types of memory devices including random access memory and read only memory can be achieved with the RS effect.
      PubDate: 2015-05-13T15:12:26.8535-05:00
      DOI: 10.1002/adfm.201501389
       
  • Tailoring Cellular Uptake of Gold Nanoparticles Via the
           
    • Authors: Zhiyue Zhang; Katleen Van Steendam, Samarendra Maji, Lieve Balcaen, Yulia Anoshkina, Qilu Zhang, Glenn Vanluchene, Riet De Rycke, Frank Van Haecke, Dieter Deforce, Richard Hoogenboom, Bruno G. De Geest
      Abstract: It is demonstrated how cellular uptake and protein corona of (co)polymer‐coated gold nanoparticles can be altered by the hydrophilic‐to‐hydrophobic comonomer ratio. A novel, label‐free flow cytometry strategy is developed to investigate particle uptake. These findings offer insight in the design and analysis of hybrid nanomaterials for interfacing with biological systems. Cellular uptake of gold nanoparticles depends on the hydrophilic‐to‐hydrophobic balance of the (co)polymer coating as shown by a novel flow cytometry strategy.
      PubDate: 2015-05-13T15:12:20.286218-05:
      DOI: 10.1002/adfm.201500904
       
  • Dichotomy in the Lithiation Pathway of Ellipsoidal and Platelet LiFePO4
           Particles Revealed through Nanoscale Operando State‐of‐Charge
           Imaging
    • Authors: Yiyang Li; Johanna Nelson Weker, William E. Gent, David N. Mueller, Jongwoo Lim, Daniel A. Cogswell, Tolek Tyliszczak, William C. Chueh
      Abstract: LiFePO4 is a promising phase‐separating battery electrode and a model system for studying lithiation. The role of particle synthesis and the corresponding particle morphology on the nanoscale insertion and migration of Li is not well understood, and elucidating the intercalation pathway is crucial toward improving battery performance. A synchrotron operando liquid X‐ray imaging platform is developed to track the migration of Li in LiFePO4 electrodes with single‐particle sensitivity. Lithiation is tracked in two particle types—ellipsoidal and platelet—while the particles cycle in an organic liquid electrolyte, and the results show a clear dichotomy in the intercalation pathway. The ellipsoidal particles intercalate sequentially, concentrating the current in a small number of actively intercalating particles. At the same cycling rate, platelet particles intercalate simultaneously, leading to a significantly more uniform current distribution. Assuming that the particles intercalate through a single‐phase pathway, it is proposed that the two particle types exhibit different surface properties, a result of different synthesis procedures, which affect the surface reactivity of LiFePO4. Alternatively, if the particles intercalate through nucleation and growth, the larger size of platelet particles may account for the dichotomy. Beyond providing particle engineering insights, the operando microscopy platform enables new opportunities for nanoscale chemical imaging of liquid‐based electrochemical systems. A nanoscale liquid imaging platform is developed to track lithium intercalation in LiFePO4 electrodes. The results show that the intercalation pathway strongly depends on the particle morphology and synthesis protocol. Highly faceted ellipsoidal particles intercalate sequentially, with a small number of actively intercalating particles and low electrode utilization. Platelet particles, on the other hand, intercalate simultaneously with a more uniform current distribution.
      PubDate: 2015-05-12T10:18:49.434977-05:
      DOI: 10.1002/adfm.201500286
       
  • From Bonding Asymmetry to Anharmonic Rattling in Cu12Sb4S13 Tetrahedrites:
           When Lone‐Pair Electrons Are Not So Lonely
    • Authors: Wei Lai; Yuxing Wang, Donald T. Morelli, Xu Lu
      Abstract: Some of the best thermoelectrics are complex materials with rattling guests inside oversized atomic cages. Understanding the chemical and structural origins of the rattling behavior is essential to the design of thermoelectric materials. In this work, a clear connection is established between the local bonding asymmetry and anharmonic rattling modes in tetrahedrite thermoelectrics, enabled by the chemically active electron lone pairs. The studies reveal a five‐atom atomic cage Sb[CuS3]Sb in Cu12Sb4S13 tetrahedrites that exhibits strong local bonding asymmetry: covalent bonding inside the CuS3 trigonal plane and weak out‐of‐plane bonding induced by the lone‐pair electrons of Sb. This bonding asymmetry leads to out‐of‐plane rattling modes that are quasilocalized and anharmonic with low frequency and large amplitude, and are likely the origin of low thermal conductivity in tetrahedrites. Such knowledge highlights the importance of local structure asymmetry and lone‐pair atoms in driving anharmonic rattling, providing a stepping stone to the discovery and design of next‐generation thermoelectrics. A strong local bonding asymmetry is identified inside a Sb[CuS3]Sb atomic cage, in which Cu (blue) forms strong covalent bonding with S (green and yellow) and forms weak covalent bonding with one of the Sb atoms (brown) enabled by the lone‐pair electrons. This bonding asymmetry causes the out‐of‐plane anharmonic rattling which leads to the low thermal conductivity.
      PubDate: 2015-05-12T10:18:44.628181-05:
      DOI: 10.1002/adfm.201500766
       
  • A Robust Ion‐Conductive Biopolymer as a Binder for Si Anodes of
           Lithium‐Ion Batteries
    • Authors: Jie Liu; Qian Zhang, Tao Zhang, Jun‐Tao Li, Ling Huang, Shi‐Gang Sun
      Abstract: Binders have been reported to play a key role in improving the cycle performance of Si anode materials of lithium‐ion batteries. In this study, the biopolymer guar gum (GG) is applied as the binder for a silicon nano­particle (SiNP) anode of a lithium‐ion battery for the first time. Due to the large number of polar hydroxyl groups in the GG molecule, a robust interaction between the GG binder and the SiNPs is achieved, resulting in a stable Si anode during cycling. More specifically, the GG binder can effectively transfer lithium ions to the Si surface, similarly to polyethylene oxide solid electrolytes. When GG is used as a binder, the SiNP anode can deliver an initial discharge capacity as high as 3364 mAh g−1, with a Coulombic efficiency of 88.3% at the current density of 2100 mA g−1, and maintain a capacity of 1561 mAh g−1 after 300 cycles. The study shows that the electrochemical performance of the SiNP anode with GG binder is significantly improved compared to that of a SiNP anode with a sodium alginate binder, and it demonstrates that GG is a promising binder for Si anodes of lithium‐ion batteries. Guar gum is used as a robust binder for a silicon nanoparticle anode of a lithium‐ion battery for the first time. With a large number of polar hydroxyl groups, the guar gum binder can provide effective transport pathways for lithium ions, which significantly improves the electrochemical performance.
      PubDate: 2015-05-12T01:54:11.409424-05:
      DOI: 10.1002/adfm.201500589
       
  • A High‐Capacitance Salt‐Free Dielectric for
           Self‐Healable, Printable, and Flexible Organic Field Effect
           Transistors and Chemical Sensor
    • Authors: Weiguo Huang; Kalpana Besar, Yong Zhang, Shyuan Yang, Gregory Wiedman, Yu Liu, Wenmin Guo, Jian Song, Kevin Hemker, Kalina Hristova, Ionnis J. Kymissis, Howard E. Katz
      Abstract: Printable and flexible electronics attract sustained attention for their low cost, easy scale up, and potential application in wearable and implantable sensors. However, they are susceptible to scratching, rupture, or other damage from bending or stretching due to their “soft” nature compared to their rigid counterparts (Si‐based electronics), leading to loss of functionality. Self‐healing capability is highly desirable for these “soft” electronic devices. Here, a versatile self‐healing polymer blend dielectric is developed with no added salts and it is integrated into organic field transistors (OFETs) as a gate insulator material. This polymer blend exhibits an unusually high thin film capacitance (1400 nF cm−2 at 120 nm thickness and 20–100 Hz). Furthermore, it shows pronounced electrical and mechanical self‐healing behavior, can serve as the gate dielectric for organic semiconductors, and can even induce healing of the conductivity of a layer coated above it together with the process of healing itself. Based on these attractive properties, we developed a self‐healable, low‐voltage operable, printed, and flexible OFET for the first time, showing promise for vapor sensing as well as conventional OFET applications. Printable and flexible, low‐voltage operating, particularly self‐healable electronics is a highly desirable suite of technologies proposed for future intelligent electronic devices such as body monitors and window displays. A key material used in printed logic circuits is reported, the “gate dielectric” insulator, with which all these attributes for the first time are demonstrated.
      PubDate: 2015-05-12T01:53:55.851452-05:
      DOI: 10.1002/adfm.201404228
       
  • Thickness Dependence of the Mechanical Properties of Free‐Standing
           Graphene Oxide Papers
    • Authors: Tao Gong; Do Van Lam, Renlong Liu, Sejeong Won, Yun Hwangbo, Sanghyuk Kwon, Jinseon Kim, Ke Sun, Jae‐Hyun Kim, Seung‐Mo Lee, Changgu Lee
      Abstract: Graphene oxide (GO) papers are candidates for structural materials in modern technology due to their high specific strength and stiffness. The relationship between their mechanical properties and structure needs to be systematically investigated before they can be applied to the broad range fields where they have potential. Herein, the mechanical properties of GO papers with various thicknesses (0.5–100 μm) are investigated using bulge and tensile test methods; this includes the Young's modulus, fracture strength, fracture strain, and toughness. The Young's modulus, fracture strength, and toughness are found to decrease with increasing thickness, with the first two exhibiting differences by a factor of four. In contrast, the fracture strain slightly increases with thickness. Transmission electron, scanning electron, and atomic force microscopy indicate that the mechanical properties vary with thickness due to variations in the inner structure and surface morphology, such as crack formation and surface roughness. Thicker GO papers are weaker because they contain more voids that are produced during the fabrication process. Surface wrinkles and residual stress are found to result in increased fracture strain. Determination of this structure–property relationship provide improved guidelines for the use of GO‐based thin‐film materials in mechanical structures. The mechanical properties of graphene oxide (GO) papers are shown to be thickness‐dependent. This dependence arises from the micro‐ and macrostructure formed during the fabrication process; microscopy studies reveal that corrugations, void defects, and surface wrinkles all influence the mechanical properties. Establishing this structure–property relationship is expected to enable improved guidelines for the application of GO to mechanical structures.
      PubDate: 2015-05-12T01:53:38.054603-05:
      DOI: 10.1002/adfm.201500998
       
  • Functionalized Graphene as an Electron‐Cascade Acceptor for
           Air‐Processed Organic Ternary Solar Cells
    • Authors: Francesco Bonaccorso; Nikolaos Balis, Minas M. Stylianakis, Marika Savarese, Carlo Adamo, Mauro Gemmi, Vittorio Pellegrini, Emmanuel Stratakis, Emmanuel Kymakis
      Abstract: Functionalized graphene nanoflakes (GNFs) are used as an electron‐cascade acceptor material in air‐processed organic ternary bulk heterojunction solar cells. The functionalization is realized via the attachment of the ethylenedinitrobenzoyl (EDNB) molecule to the GNFs. Simulation and experimental results show that such nanoscale modification greatly influences the density of states near the Fermi level. Consequently, the GNF‐EDNB blend presents favorable highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels to function as a bridge structure between the poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT) and the [6,6]‐phenyl‐C71‐butyric‐acid‐methyl‐ester (PC71BM). The improved exciton dissociation and charge transport are associated with the better energy level alignment of the ternary blend and the high electrical conductivity of the GNFs, which act as additional electron transport channels within the photoactive layer. The resulting PCDTBT/GNF‐EDNB/PC71BM ternary organic solar cells, fabricated entirely under ambient conditions, exhibit an average power conversion efficiency enhancement of ≈18% as compared with the binary blend PCDTBT/PC71BM. Graphene nanoflakes functionalized with 3,5‐dinitrobenzoyl with tunable energy levels are used as an electron‐cascade acceptor in air‐processed ternary organic solar cells (OSCs). Ternary OSCs exhibit an efficiency of 6.41%, 18% higher than the binary blend and one of the highest for air‐processed OSCs.
      PubDate: 2015-05-12T01:53:18.390123-05:
      DOI: 10.1002/adfm.201501052
       
  • Liquid‐Metal Electrode for High‐Performance Triboelectric
           Nanogenerator at an Instantaneous Energy Conversion Efficiency of 70.6%
    • Authors: Wei Tang; Tao Jiang, Feng Ru Fan, Ai Fang Yu, Chi Zhang, Xia Cao, Zhong Lin Wang
      Abstract: Harvesting ambient mechanical energy is a key technology for realizing self‐powered electronics, which has tremendous applications in wireless sensing networks, implantable devices, portable electronics, etc. The currently reported triboelectric nanogenerator (TENG) mainly uses solid materials, so that the contact between the two layers cannot be 100% with considering the roughness of the surfaces, which greatly reduces the total charge density that can be transferred and thus the total energy conversion efficiency. In this work, a liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is developed for high power generation through conversion of mechanical energy, which allows a total contact between the metal and the dielectric. Due to that the liquid–solid contact induces large contacting surface and its shape adaptive with the polymer thin films, the LM‐TENG exhibits a high output charge density of 430 μC m−2, which is four to five times of that using a solid thin film electrode. And its power density reaches 6.7 W m−2 and 133 kW m−3. More importantly, the instantaneous energy conversion efficiency is demonstrated to be as high as 70.6%. This provides a new approach for improving the performance of the TENG for special applications. Furthermore, the liquid easily fluctuates, which makes the LM‐TENG inherently suitable for vibration energy harvesting. A liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is developed for high power generation through conversion of mechanical energy, which allows total contact between the metal and the dielectric. The LM‐TENG exhibits a high output charge density of 430 μC m−2, which is four to five times of that using a solid thin film electrode. An instantaneous energy conversion efficiency as high as 70.6% is demonstrated.
      PubDate: 2015-05-12T01:52:59.845798-05:
      DOI: 10.1002/adfm.201501331
       
  • Hybrid Improper Ferroelectricity in Multiferroic Superlattices:
           Finite‐Temperature Properties and Electric‐Field‐Driven
           Switching of Polarization and Magnetization
    • Authors: Bin Xu; Dawei Wang, Hong Jian Zhao, Jorge Íñiguez, Xiang Ming Chen, Laurent Bellaiche
      Abstract: The so‐called hybrid improper ferroelectricity (HIF) mechanism allows to create an electrical polarization by assembling two nonpolar materials within a superlattice. It may also lead to the control of the magnetization by an electric field when these two nonpolar materials are magnetic in nature, which is promising for the design of novel magneto‐electric devices. However, several issues of fundamental and technological importance are presently unknown in these hybrid improper ferroelectrics. Examples include the behaviors of its polarization and dielectric response with temperature, and the paths to switch both the polarization and magnetization under electric fields. Here, an effective Hamiltonian scheme is used to study the multiferroic properties of the model superlattice (BiFeO3)1/(NdFeO3)1. Along with the development of a novel Landau‐type potential, this approach allows to answer and understand all the aforementioned issues at both microscopic and macroscopic levels. In particular, the polarization and dielectric response are both found to adopt temperature dependences, close to the phase transition, that agree with the behavior expected for first‐order improper ferroelectrics. And most importantly, a five‐state path resulting in the switching of polarization and magnetization under an electric field, via the reversal of antiphase octahedral tiltings, is also identified. The hybrid improper ferroelectricity (HIF) mechanism generates an electrical polarization in a superlattice made of two nonpolar materials and is promising for the design of novel multiferroics. A first‐principles‐based technique is used here to resolve unknown issues about HIF, including the discovery of a path allowing the switching of polarization and magnetization, and how the HIF transition occurs upon cooling.
      PubDate: 2015-05-12T01:52:48.683946-05:
      DOI: 10.1002/adfm.201501113
       
  • Stretchable‐Rubber‐Based Triboelectric Nanogenerator and Its
           Application as Self‐Powered Body Motion Sensors
    • Authors: Fang Yi; Long Lin, Simiao Niu, Po Kang Yang, Zhaona Wang, Jun Chen, Yusheng Zhou, Yunlong Zi, Jie Wang, Qingliang Liao, Yue Zhang, Zhong Lin Wang
      Abstract: A stretchable‐rubber‐based (SR‐based) triboelectric nanogenerator (TENG) is developed that can not only harvest energy but also serve as self‐powered multifunctional sensors. It consists of a layer of elastic rubber and a layer of aluminum film that acts as the electrode. By stretching and releasing the rubber, the changes of triboelectric charge distribution/density on the rubber surface relative to the aluminum surface induce alterations to the electrical potential of the aluminum electrode, leading to an alternating charge flow between the aluminum electrode and the ground. The unique working principle of the SR‐based TENG is verified by the coupling of numerical calculations and experimental measurements. A comprehensive study is carried out to investigate the factors that may influence the output performance of the SR‐based TENG. By integrating the devices into a sensor system, it is capable of detecting movements in different directions. Moreover, the SR‐based TENG can be attached to a human body to detect diaphragm breathing and joint motion. This work largely expands the applications of TENG not only as effective power sources but also as active sensors; and opens up a new prospect in future electronics. A stretchable‐rubber‐based triboelectric nanogenerator is developed, which can not only harvest energy but also serve as self‐powered multifunctional sensors. It is composed of a layer of elastic rubber and a layer of aluminum film that acts as the electrode. Electrical outputs are generated by stretching and releasing the rubber. It can be attached to a human body to detect diaphragm breathing and joint motion.
      PubDate: 2015-05-08T14:16:44.462438-05:
      DOI: 10.1002/adfm.201500428
       
  • Phenylboronic Acid‐Decorated Chondroitin Sulfate A‐Based
           Theranostic Nanoparticles for Enhanced Tumor Targeting and Penetration
    • Authors: Jae‐Young Lee; Suk‐Jae Chung, Hyun‐Jong Cho, Dae‐Duk Kim
      Abstract: Phenylboronic acid‐functionalized chondroitin sulfate A (CSA)–deoxycholic‐acid (DOCA)‐based nanoparticles (NPs) are prepared for tumor targeting and penetration. (3‐Aminomethylphenyl)boronic acid (AMPB) is conjugated to CSA–DOCA conjugate via amide bond formation, and its successful synthesis is confirmed using proton nuclear magnetic resonance spectroscopy (1H‐NMR). Doxorubicin (DOX)‐loaded CSA–DOCA–AMPB NPs with a mean diameter of ≈200 nm, a narrow size distribution, negative zeta potential, and spherical morphology are prepared. DOX release from NPs is enhanced at acidic pH compared to physiological pH. CSA–DOCA–AMPB NPs exhibit improved cellular uptake in A549 (human lung adenocarcinoma) cells and penetration into A549 multicellular spheroids compared to CSA–DOCA NPs as evidenced by confocal laser scanning microscopy and flow cytometry. In vivo tumor targeting and penetrating by CSA–DOCA–AMPB NPs, based on both CSA–CD44 receptor and boronic acid–sialic acid interactions, is revealed using near‐infrared fluorescence (NIRF) imaging. Penetration of NPs to the core of the tumor mass is observed in an A549 tumor xenografted mouse model and verified by three‐dimensional NIRF imaging. Multiple intravenous injections of DOX‐loaded CSA–DOCA–AMPB NPs efficiently inhibit the growth of A549 tumor in the xenografted mouse model and increase apoptosis. These boronic acid‐rich NPs are promising candidates for cancer therapy and imaging. (3‐Aminomethylphenyl)boronic acid ­(AMPB)‐­functionalized chondroitin sulfate A (CSA)–deoxycholic acid (DOCA)‐based nanoparticles (NPs) are prepared for anticancer drug delivery and cancer diagnosis. Doxorubicin (DOX)‐loaded CSA–DOCA–AMPB NPs exhibit improved targeting, penetration, and therapeutic efficacies for CD44 receptor‐expressed tumors, compared to CSA–DOCA NPs, via CSA–CD44 receptor and boronic‐acid–sialic‐acid interactions.
      PubDate: 2015-05-08T14:16:36.637113-05:
      DOI: 10.1002/adfm.201500680
       
  • Sea‐Urchin‐Inspired 3D Crumpled Graphene Balls Using
           Simultaneous Etching and Reduction Process for High‐Density
           Capacitive Energy Storage
    • Authors: Jang Yeol Lee; Kwang‐Hoon Lee, Young Jin Kim, Jeong Sook Ha, Sang‐Soo Lee, Jeong Gon Son
      Abstract: A crumpled configuration of graphene is desirable for preventing irreversible stacking between individual nanosheets, which can be a major hurdle toward its widespread application. Herein a sea‐urchin‐shaped template approach is introduced for fabricating highly crumpled graphene balls in bulk quantities with a simple process. Simultaneous chemical etching and reduction process of graphene oxide (GO)‐encapsulated iron oxide particles results in dissolution of the core template with spiky morphology and conversion of the outer GO layers into reduced GO layers with increased hydrophobicity which remain in contact with the spiky surface of the template. After completely etching, the outer graphene layers are fully compressed into the crumpled form along with decrease in total volume by etching. The crumpled balls exhibit significantly larger surface area and good water‐dispersion stability than those of stacked reduced GO or other crumple approaches, even though they also show comparable electrical conductivity. Furthermore, they are easily assembled into 3D macroporous networks without any binders through typical processes such as solvent casting or compression molding. The graphene networks with less pore volume still have the crumpled morphology without sacrificing the properties regardless of the assembly processes, producing a promising active electrode material with high gravimetric and volumetric energy density for capacitive energy storage. Highly crumpled graphene balls with a sea‐urchin‐shaped template strategy are facilely fabricated in bulk quantities with high yield through simultaneous etching–reduction of graphene oxide‐encapsulated iron oxide. The crumpled balls, which exhibit significantly larger surface area and higher water‐dispersion stability than those of stacked graphene and other crumpling approaches, and their 3D macroporous networks present superior gravimetric and volumetric capacitance of electrochemical energy‐storage electrodes.
      PubDate: 2015-05-07T11:28:28.306124-05:
      DOI: 10.1002/adfm.201404507
       
  • Negatively Charged Magnetite Nanoparticle Clusters as Efficient MRI Probes
           for Dendritic Cell Labeling and In Vivo Tracking
    • Authors: Changqiang Wu; Ye Xu, Li Yang, Jun Wu, Wencheng Zhu, Danyang Li, Zhuzhong Cheng, Chunchao Xia, Yingkun Guo, Qiyong Gong, Bin Song, Hua Ai
      Abstract: Cell labeling and tracking via magnetic resonance imaging (MRI) has drawn much attention for its noninvasive property and longitudinal monitoring functionality. Employing of imaging probes with high labeling efficiency and good biocompatibility is one of the essential factors that determine the outcome of tracking. In this study, negatively charged superparamagnetic iron oxide (PAsp‐PCL/SPIO) nanoclusters are developed for dendritic cell (DC) labeling and tracking in vivo. PAsp‐PCL/SPIO has a diameter of 124 ± 41 nm in DLS, negatively charged surface (zeta potential = −27 mV), and presents high T 2 relaxivity (335.6 Fe mm −1 s−1) and good DC labeling efficiency. Labeled DCs are unaffected in their viability, proliferation, and differentiation capacity, and have an excellent MR imaging sensitivity in vitro. To monitor the migration of DCs into lymphoid tissues in vivo, which will be related to the final immunotherapy results, T 2‐wighted and T 2‐map imaging of popliteal nodes at different points in time are acquired under a clinical 3 T scanner after subcutaneous injection of a certain number of labeled DCs at hindleg footpads of mice. The signal intensities decreasing and T 2 values shortening of ipsilateral popliteal nodes are significant and display a time‐ and dose‐dependence, showing DCs' migration to the draining lymph nodes. Negatively charged superparamagnetic iron oxide (SPIO) nanocluster is developed. As magnetic resonance imaging (MRI) probe, it has high T 2 relaxivity (335.6 Fe mm −1 s−1) and good dendritic cell (DC) labeling efficiency. Labeled DCs with this probe are unaffected in their viability, proliferation, and differentiation capacity. The migration of DCs in vivo can easily be monitored via clinical magnetic resonance imaging scan.
      PubDate: 2015-05-07T11:28:22.446958-05:
      DOI: 10.1002/adfm.201501031
       
  • Effect of Spacer Length of Siloxane‐Terminated Side Chains on Charge
           Transport in Isoindigo‐Based Polymer Semiconductor Thin Films
    • Authors: Jianguo Mei; Hung‐Chin Wu, Ying Diao, Anthony Appleton, Hong Wang, Yan Zhou, Wen‐Ya Lee, Tadanori Kurosawa, Wen‐Chang Chen, Zhenan Bao
      Abstract: A series of isoindigo‐based conjugated polymers (PII2F‐CmSi, m = 3–11) with alkyl siloxane‐terminated side chains are prepared, in which the branching point is systematically “moved away” from the conjugated backbone by one carbon atom. To investigate the structure–property relationship, the polymer thin film is subsequently tested in top‐contact field‐effect transistors, and further characterized by both grazing incidence X‐ray diffraction and atomic force microscopy. Hole mobilities over 1 cm2 V−1 s−1 is exhibited for all soluble PII2F‐CmSi (m = 5–11) polymers, which is 10 times higher than the reference polymer with same polymer backbone. PII2F‐C9Si shows the highest mobility of 4.8 cm2 V−1 s−1, even though PII2F‐C11Si exhibits the smallest π–π stacking distance at 3.379 Å. In specific, when the branching point is at, or beyond, the third carbon atoms, the contribution to charge transport arising from π–π stacking distance shortening becomes less significant. Other factors, such as thin‐film microstructure, crystallinity, domain size, become more important in affecting the resulting device's charge transport. Alkyl siloxane‐terminated side chains equipped isoindigo‐based conjugated polymers (PII2F‐CmSi, m = 3–11) are prepared to evaluate the structure–property relationship as the branching point is systematically “moved away” from the conjugated backbone one carbon atom at a time. An improved charge carrier mobility of 4.76 cm2 V−1 s−1 (PII2F‐C9Si) is exhibited.
      PubDate: 2015-05-07T11:27:42.273074-05:
      DOI: 10.1002/adfm.201500684
       
  • Well‐Defined Pillararene‐Based Azobenzene Liquid Crystalline
           Photoresponsive Materials and Their Thin Films with Photomodulated
           Surfaces
    • Authors: Shi Pan; Mengfei Ni, Bin Mu, Qian Li, Xiao‐Yu Hu, Chen Lin, Dongzhong Chen, Leyong Wang
      Abstract: Photoresponsive materials (PRMs) have long been a hot topic and photo‐modulated smart surface is very appealing. Particularly, liquid crystalline PRMs are able to amplify and stabilize photoinduced orientation thanks to their self‐assembling and ordering characteristics. Herein, the first pillararene‐based azobenzene liquid crystalline PRM with well‐defined structure is presented, which can avoid the usually ill‐defined composition drawback of polymer PRMs and prevent the severe H‐aggregation from suppressing or even completely blocking photoresponse in simple azobenzene derivatives. The pillar[5]arene‐based macrocyclic azobenzenes with variant length spacers show wide temperature range smectic liquid crystalline mesophases and excellent film‐formation property. The tubular pillar[5]arene macrocyclic framework provides sufficient free volume for azobenzene moieties to achieve reversible photoisomerization and photoalignment; thus, their thin films demonstrate excellent light‐triggered modulation of surface free energy, wettability, and even photoalignment‐mediated orientation of an upper layer discotic liquid crystal columnar mesophase. Such pillararene‐based azobenzene liquid crystals represent novel and promising PRMs with extensive fascinating applications. Fascinating photoresponsive thin films are well prepared from the first synthesized pillararene‐based macrocyclic azobenzene liquid crystals, which demonstrate rapid reversible photoisomerization and on–off switching property, with further excellent light‐triggered modulation of surface free energy, wettability, and even photoalignment‐mediated orientation of discotic liquid crystal columnar mesophase. Such well‐defined photoresponsive materials provide a promising platform for constructing various novel photoresponsive systems.
      PubDate: 2015-05-07T11:27:37.13586-05:0
      DOI: 10.1002/adfm.201500942
       
  • Thin Film Silicon Photovoltaic Cells on Paper for Flexible Indoor
           Applications
    • Authors: Hugo Águas; Tiago Mateus, António Vicente, Diana Gaspar, Manuel J. Mendes, Wolfgang A. Schmidt, Luís Pereira, Elvira Fortunato, Rodrigo Martins
      Abstract: The present development of non‐wafer‐based photovoltaics (PV) allows supporting thin film solar cells on a wide variety of low‐cost recyclable and flexible substrates such as paper, thereby extending PV to a broad range of consumer‐oriented disposable applications where autonomous energy harvesting is a bottleneck issue. However, their fibrous structure makes it challenging to fabricate good‐performing inorganic PV devices on such substrates. The advances presented here demonstrate the viability of fabricating thin film silicon PV cells on paper coated with a hydrophilic mesoporous layer. Such layer can not only withstand the cells production temperature (150 °C), but also provide adequate paper sealing and surface finishing for the cell's layers deposition. The substances released from the paper substrate are continuously monitored during the cell deposition by mass spectrometry, which allows adapting the procedures to mitigate any contamination from the substrate. In this way, a proof‐of‐concept solar cell with 3.4% cell efficiency (41% fill factor, 0.82 V open‐circuit voltage and 10.2 mA cm−2 short‐circuit current density) is attained, opening the door to the use of paper as a reliable substrate to fabricate inorganic PV cells for a plethora of indoor applications with tremendous impact in multi‐sectorial fields such as food, pharmacy and security. Inkjet printing paper with a cast‐coated hydrophilic mesoporous material is proven to be highly suitable to process n–i–p amorphous silicon hydrogenated photovoltaic cells with efficiencies above 3%, opening a new era of energy harvesting, including its seamless integration into ubiquitous formats for a plethora of low‐cost flexible and disposable products.
      PubDate: 2015-05-07T11:27:31.50498-05:0
      DOI: 10.1002/adfm.201500636
       
  • Highly Stretchable, Global, and Distributed Local Strain Sensing Line
           Using GaInSn Electrodes for Wearable Electronics
    • Authors: Ryosuke Matsuzaki; Kosuke Tabayashi
      Abstract: For identifying human or finger movement, it is necessary to sense subtle movements at multiple points, including the local strain and global deformation simultaneously; however, this has not yet been realized. Therefore, a highly stretchable, global, and distributed local strain sensing electrode made of GaInSn and polydimethylsiloxane is developed for wearable devices. To investigate the electrical properties of multiple sections of the GaInSn electrode when stretching, tensile, cyclic, and three‐point‐bending tests are performed. The results demonstrate that the electrode can withstand a strain up to 50% and has little hysteresis without any delay. Moreover, the distributed local strain and global strain can be simultaneously measured using just a single electrode line. Finally, a prototype of a data glove as an application of the strain sensing line is manufactured, and it is demonstrated that the folding state of fingers could be identified. The proposed technology may allow the creation of a lightweight master hand manipulator or 3D data entry device. A highly stretchable, global, and distributed local strain sensing electrode made of GaInSn and polydimethylsiloxane is developed for wearable devices. Simultaneous measurement of the distributed local and global strains can be achieved using a single electrode line. A data‐glove prototype is manufactured as an application of the strain sensing line, demonstrating identification of the folding state of fingers.
      PubDate: 2015-05-07T11:27:22.822874-05:
      DOI: 10.1002/adfm.201501396
       
  • Self‐Assembled, Millimeter‐Sized TIPS‐Pentacene
           Spherulites Grown on Partially Crosslinked Polymer Gate Dielectric
    • Authors: Hocheon Yoo; Hyun Ho Choi, Tae Joo Shin, Taiuk Rim, Kilwon Cho, Sungjune Jung, Jae‐Joon Kim
      Abstract: Here, a highly crystalline and self‐assembled 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐Pentacene) thin films formed by simple spin‐coating for the fabrication of high‐performance solution‐processed organic field‐effect transistors (OFETs) are reported. Rather than using semiconducting organic small‐molecule–insulating polymer blends for an active layer of an organic transistor, TIPS‐Pentacene organic semiconductor is separately self‐assembled on partially crosslinked poly‐4‐vinylphenol:poly(melamine‐co‐formaldehyde) (PVP:PMF) gate dielectric, which results in a vertically segregated semiconductor‐dielectric film with millimeter‐sized spherulite‐crystalline morphology of TIPS‐Pentacene. The structural and electrical properties of TIPS‐Pentacene/PVP:PMF films have been studied using a combination of polarized optical microscopy, atomic force microscopy, 2D‐grazing incidence wide‐angle X‐ray scattering, and secondary ion mass spectrometry. It is finally demonstrated a high‐performance OFETs with a maximum hole mobility of 3.40 cm2 V−1 s−1 which is, to the best of our knowledge, one of the highest mobility values for TIPS‐Pentacene OFETs fabricated using a conventional solution process. It is expected that this new deposition method would be applicable to other small molecular semiconductor–curable polymer gate dielectric systems for high‐performance organic electronic applications. Partial crosslinking of polymer gate‐dielectrics (pc‐PVP:PMF) allows semiconducting small molecules in solvent to permeate into it. The solvent evaporation during spinning promotes the extraction of TIPS‐Pentacene solution onto pc‐PVP:PMF surface. The residual solvent in pc‐PVP:PMF network evaporates slowly, so it helps millimeter‐sized crystallization of TIPS‐Pentacene molecules. Consequently, the OFET devices exhibit high mobilities with maximum value of 3.40 cm2 V−1 s−1.
      PubDate: 2015-05-07T11:27:03.423255-05:
      DOI: 10.1002/adfm.201501381
       
  • Locally and Dynamically Controllable Surface Topography Through the Use of
           Particle‐Enhanced Soft Composites
    • Authors: Mark Guttag; Mary C. Boyce
      Abstract: A new class of soft composite materials with dynamically tunable and reversible surface topographies is introduced that allows a wide diversity and local positioning of surface features. The particle‐enhanced soft composites are comprised of a soft elastomeric matrix with relatively stiff particles embedded below the surface. Upon application of external stimuli, a surface that is originally smooth and flat (or of other initial topology) transforms to engineered surface topographies. Finite element based micromechanical simulations are used to design and study the hybrid material structures that govern the evolution in surface topographies. Physical prototypes are fabricated using multimaterial 3D‐printing, and then experimentally evaluated to validate the accuracy of our simulations. It is demonstrated that a rich variety in periodic and random surface features including variable waves, crease‐like features, flat apexes, and valleys can be attained by changing different dimensionless geometric parameters (e.g., relative particle size, shapes, spacing, and distributions). Furthermore, these surface features can be locally controlled by positioning of particles and do not rely on instabilities. The material design depends primarily on the geometry of the particles and the arrays, making this approach to on‐demand custom and reversible surface patterning applicable over a wide range of size scales. Creating tunable and reversible surfaces is an interesting challenge with no single solution. A new approach using a composite of stiff particles embedded into a soft matrix provides a wide range of tunable and locally controllable surface topographies. By applying an external load to the composite, complex surface topographies take shape.
      PubDate: 2015-05-07T11:26:58.230891-05:
      DOI: 10.1002/adfm.201501035
       
  • Size‐Dependent Optical Absorption of Layered MoS2 and DNA
           Oligonucleotides Induced Dispersion Behavior for Label‐Free
           Detection of Single‐Nucleotide Polymorphism
    • Authors: Bang Lin Li; Hao Lin Zou, Lu Lu, Yu Yang, Jing Lei Lei, Hong Qun Luo, Nian Bing Li
      Abstract: Size‐dependent optical absorption of semiconductive (2H) layered molybdenum disulfide (MoS2), exhibiting great discrimination abilities to single‐ and double‐stranded DNA (ssDNA) and (dsDNA), is studied. In the presence of high concentration of salt, layered MoS2 trends to aggregate rapidly, leading to the increases of sizes in both vertical and lateral dimensions of the nanosheets, which results from the interplay between van der Waals attraction and electrical double‐layer repulsion. Meanwhile, the aggregation behavior of layered MoS2 is remarkably inhibited by the synergistic effects of DNA oligonucleotides. ssDNA can adsorb on the surface of layered MoS2, resulting in a great dispersion, even in the presence of high concentration of salt, while the dispersion behavior is weakened when ssDNA is replaced by dsDNA. Whereas compared to graphene with zero bandgap energy, layered MoS2, with semiconductive properties, exhibits great characteristic optical absorption in visible wavelength region devoted to exploring the aggregation behavior of layered MoS2. Therefore, DNA oligonucleotides induced size control of layered MoS2, contributing to the regular change of its characteristic absorption in visible region, is considered a label‐free bioassay for the detection of single‐nucleotide polymorphism. Due to its easy operation and high specificity, it is expected that the proposed assay holds great promise for further applications. Size‐dependent optical absorption of semiconductive (2H) layered molybdenum disulfide (MoS2), exhibiting great discriminated abilities to single‐ and double‐stranded DNA, is explored through salt‐induced aggregation of 2D nanosheets. Meanwhile, the aggregation behavior of layered MoS2 is remarkably inhibited by the synergistic effects of DNA oligonucleotides, contributing to the developments of biosensors based on optical absorption spectrum of layered MoS2.
      PubDate: 2015-05-06T13:49:32.587375-05:
      DOI: 10.1002/adfm.201500180
       
  • Sn‐Based Nanoparticles Encapsulated in a Porous 3D Graphene Network:
           Advanced Anodes for High‐Rate and Long Life Li‐Ion Batteries
    • Authors: Chao Wu; Joachim Maier, Yan Yu
      Abstract: Sn‐based materials have triggered significant research efforts as anodes for lithium‐storage because of their high theoretical capacity. However, the practical applications of Sn‐based materials are hindered by low capacity release and poor cycle life, which are mainly caused by structural pulverization and large volume changes on cycling. Herein, a surfactant‐assisted assembly method is developed to fabricate 3D nanoarchitectures in which Sn‐based nanoparticles are encapsulated by a porous graphene network. More precisely, the graphene forms a 3D cellular network, the interstices of which only partially filled by the electroactive masses, thus establishing a high concentration of interconnected nanosized pores. While the graphene‐network itself guarantees fast electron transfer, it is the characteristic presence of nanosized pores in our network that leads to the favorable rate capability and cycling stability by i) accommodating the large volume expansion of Sn‐based nanoparticles to ensure integrity of the 3D framework upon cycling and ii) enabling rapid access of Li‐ions into Sn‐based nanoparticles, which are in addition prevented from agglomerating. As a result, the 3D Sn‐based nanoarchitectures deliver excellent electrochemical properties including high rate capability and stable cycle performance. Importantly, this strategy provides a new pathway for the rational engineering of anode materials with large volume changes to achieve improved electrochemical performances. 3D porous graphene network‐encapsulated Sn‐based nanoarchitectures (0D‐CoSnO3⊂3D‐pGN and 0D‐Co–Sn⊂3D‐pGN) are successfully fabricated by an assembly route. It is the characteristic presence of nanosized pores in the nanostructure that facilitates the access of Li‐ions into Sn‐based nanoparticles, accommodates the large volume expansion of Sn‐based nanoparticles, and preserves the integrity of the 3D graphene‐network, leading to excellent electrochemical properties in terms of high rate capability and ultralong cycle life.
      PubDate: 2015-05-06T13:49:27.231244-05:
      DOI: 10.1002/adfm.201500514
       
  • Tumor Intracellular‐Environment Responsive Materials Shielded
           Nano‐Complexes for Highly Efficient Light‐Triggered Gene
           Delivery without Cargo Gene Damage
    • Authors: Sin‐jung Park; Wooram Park, Kun Na
      Abstract: Gene therapy has great potential to bring tremendous improvement to cancer therapy. Recently, photochemical internalization (PCI) has provided the opportunity to overcome endo‐lysosomal sequestration, which is one of the main bottlenecks in both gene and chemotherapeutic delivery. Despite PCI having shown great potential in gene delivery systems, it still remains difficult to perform due to the photo‐oxidation of exogenous cargo genes by reactive oxygen species (ROS) generated from activated photosensitizers (PSs). In this paper, a new type of a stable light‐triggered gene delivery system is demonstrated based on endo‐lysosomal pH‐responsive polymeric PSs, which serve as shielding material for the polymer/gene complex. By taking advantage of the endo‐lysosomal pH‐sensitive de‐shielding ability of the pH‐responsive shielding material incorporated in the ternary gene complexes (pH‐TCs), a more significant photo‐triggered gene expression effect is achieved without damage to the gene from ROS. In contrast, pH‐insensitive material‐shielded nanocarriers cause photo‐oxidation of the payload and do not generate a notable transfection efficacy. Importantly, with the benefit of our newly developed gene delivery system, the deep penetration issue can be resolved. Finally, the light‐triggered gene delivery system using pH‐TCs is applied to deliver the therapeutic p53 gene in melanoma K‐1735 bearing mice, showing excellent therapeutic potential for cancer. A new type of stable light‐triggered gene delivery system is designed based on a pH‐responsive shielding material incorporated into ternary gene complexes (pH‐TCs). The endosomal pH‐sensitive de‐shielding effect of pH‐TCs exhibits highly discriminating light‐triggered gene expression both in vitro and in vivo without cargo gene damage.
      PubDate: 2015-05-05T09:07:10.238019-05:
      DOI: 10.1002/adfm.201500737
       
  • High‐Fidelity Bioelectronic Muscular Actuator Based on
           Graphene‐Mediated and TEMPO‐Oxidized Bacterial Cellulose
    • Authors: Si‐Seup Kim; Jin‐Han Jeon, Hyun‐Il Kim, Chang Doo Kee, Il‐Kwon Oh
      Abstract: High‐performance electoactive artificial muscles with biofriendly, biodegradable, and biocompatible functionalities have attracted enormous attention in the era of human friendly electronic devices such as wearable electronics, soft haptic devices, and implantable or disposal biomedical devices. Here, a high‐fidelity bioelectronic soft actuator is reported based on biofriendly 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical‐oxidized bacterial cellulose (TOBC), chemically modified graphene, and ionic liquid [EMIM][BF4] as plasticizer, thereby realizing large deformable, faster, biodegradable, air working, and highly durable TOBC‐IL‐G muscular actuator. Especially, the TOBC‐IL‐G(0.10 wt%) membrane shows a dramatic increment of the ionic conductivity up to 120%, of specific capacitance up to 95%, of tensile modulus up to 63%, and of tensile strength up to 60%, for TOBC‐IL, resulting in 2.3 times larger bending deformation without serious back‐relaxation phenomena. The developed high‐performance and durable bioelectronic muscular actuator can be a promising candidate for satisfying the tight requirements of human‐related bioengineering as well as biomimetic robotics and biomedical active devices. A high‐fidelity bioelectronic muscular actuator is described that is based on 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical‐oxidized bacterial cellulose (TOBC), chemically modified graphene, ionic liquid, and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate. The TOBC‐IL‐G muscular actuator has biodegradable and biofriendly functionalities and shows exceptionally large static deformation without apparent back‐relaxation, much faster response time, and highly durable harmonic actuation compared with conventional biopolymer actuators.
      PubDate: 2015-05-05T09:06:28.289728-05:
      DOI: 10.1002/adfm.201500673
       
  • Crystallization Properties of the Ge2Sb2Te5 Phase‐Change Compound
           from Advanced Simulations
    • Authors: Ider Ronneberger; Wei Zhang, Hagai Eshet, Riccardo Mazzarello
      Abstract: Ge2Sb2Te5 (GST) is an important phase‐change material used in optical and electronic memory devices. In this work, crystal growth of GST at 600 K is investigated by ab initio molecular dynamics. Simulations of two different crystallization processes are performed. In the first set of simulations, the growth of crystalline nuclei generated using the metadynamics method is studied. In the second set, models containing a planar amorphous–crystalline interface are considered and the crystallization at the interface is investigated. The extracted crystal growth velocities are in the range of 1 m s−1 in both cases and compare well with recent experimental measurements. It is also found that GST crystallizes into a disordered cubic phase in all the simulations. The crystallization properties of the phase‐change material Ge2Sb2Te5 (GST) at high temperature are investigated by advanced ab initio molecular dynamics simulations. The crystal growth processes from both a quasi‐spherical nucleus and a planar amorphous–crystalline interface are considered. The obtained growth velocities are compatible with recent experiments. The simulations elucidate the fast crystal growth of the phase change GST compound at the atomistic level.
      PubDate: 2015-05-05T09:05:12.087967-05:
      DOI: 10.1002/adfm.201500849
       
  • Valence‐Optimized Vanadium Oxide Supercapacitor Electrodes Exhibit
           Ultrahigh Capacitance and Super‐Long Cyclic Durability of 100 000
           Cycles
    • Authors: Minghao Yu; Yan Zeng, Yi Han, Xinyu Cheng, Wenxia Zhao, Chaolun Liang, Yexiang Tong, Haolin Tang, Xihong Lu
      Abstract: Vanadium oxides (VOx) have been intensely investigated as cathode materials for SCs due to the multiple stable oxidation states (III–V) of vanadium in its oxides and typical layered structure. Nevertheless, fast capacity fading is always observed for VOx upon cycling in aqueous electrolyte. Developing an efficient strategy to essentially promote the durability of VOx in mild aqueous electrolyte remains a crucial challenge. Here, an innovative and effective method is reported to significantly boost the durability and capacitance of VOx through tuning the valence state of vanadium. The valence state of vanadium is optimized through a very facile electrochemical oxidation method. A superior electrochemical performance and an ultralong cyclic stability of 100 000 cycles are obtained for these electrodes. An in‐depth study on the variation for the valence state of vanadium during the oxidation process and the cyclic stability test indicates that the long cyclic stability has an important relationship with the distribution of the valence state of vanadium. Aiming at the crucial challenge of poor electrochemical stability for vanadium oxides electrodes, an innovative and effective method is reported to significantly boost their durability and capacitance through tuning the valence state of vanadium.
      PubDate: 2015-05-05T09:04:14.747373-05:
      DOI: 10.1002/adfm.201501342
       
  • Structure‐Invertible Nanoparticles for Triggered Co‐Delivery
           of Nucleic Acids and Hydrophobic Drugs for Combination Cancer Therapy
    • Authors: Kai Wang; Qida Hu, Wei Zhu, Mengmeng Zhao, Yuan Ping, Guping Tang
      Abstract: Here, a new type of structure‐invertible, redox‐responsive polymeric nanoparticle for the efficient co‐delivery of nucleic acids and hydrophobic drugs in vitro and in vivo is reported for the first time, to combat the major challenges facing combination cancer therapy. The co‐delivery vector, which is prepared by conjugating branched poly(ethylene glycol) with dendrimers of two generations (G2) through disulfide linkages, is able to complex nucleic acids and load hydrophobic drugs with high loading capacity through structure inversion. The cleavage of disulfide linkages at intracellular glutathione‐rich reduction environment significantly decreases the cytotoxicity, and promotes more efficient drug release and gene transfection in vitro and in vivo. The co‐delivery carrier also displays enhanced endosomal escape capability and improved serum stability in vitro as compared with G2, and exhibits prolonged residence time and stronger transfection activity in vivo. Most importantly, co‐delivery of doxorubicin (DOX) and B‐cell lymphoma 2 (Bcl‐2) small interfering RNA (siRNA) exerts a combinational effect against tumor growth in murine tumor models in vivo, which is much more effective than either DOX or Bcl‐2 siRNA‐based monotherapy. The structure‐invertible nanoparticles may constitute a promising stimuli‐responsive system for the efficacious co‐delivery of multiple cargoes in future clinical applications of combination cancer therapies. Structure‐invertible nanoparticles are developed for the triggered co‐delivery of nucleic acids and hydrophobic drugs for combination cancer therapy in vivo. The co‐delivery nanoparticle is able to ‘lock’ loaded cargos through structure inversion, and release these cargos in the glutathione‐rich reduction environment. The low cytotoxic structure‐invertible nanoparticles may constitute a promising stimuli‐responsive system for the efficacious co‐delivery of multiple cargoes in future applications of combination therapies.
      PubDate: 2015-05-04T10:01:57.211215-05:
      DOI: 10.1002/adfm.201403921
       
  • Soft, Flexible Freestanding Neural Stimulation and Recording Electrodes
           Fabricated from Reduced Graphene Oxide
    • Authors: Nicholas V. Apollo; Matias I. Maturana, Wei Tong, David A. X. Nayagam, Mohit N. Shivdasani, Javad Foroughi, Gordon G. Wallace, Steven Prawer, Michael R. Ibbotson, David J. Garrett
      Abstract: There is an urgent need for conductive neural interfacing materials that exhibit mechanically compliant properties, while also retaining high strength and durability under physiological conditions. Currently, implantable electrode systems designed to stimulate and record neural activity are composed of rigid materials such as crystalline silicon and noble metals. While these materials are strong and chemically stable, their intrinsic stiffness and density induce glial scarring and eventual loss of electrode function in vivo. Conductive composites, such as polymers and hydrogels, have excellent electrochemical and mechanical properties, but are electrodeposited onto rigid and dense metallic substrates. In the work described here, strong and conductive microfibers (40–50 μm diameter) wet‐spun from liquid crystalline dispersions of graphene oxide are fabricated into freestanding neural stimulation electrodes. The fibers are insulated with parylene‐C and laser‐treated, forming “brush” electrodes with diameters over 3.5 times that of the fiber shank. The fabrication method is fast, repeatable, and scalable for high‐density 3D array structures and does not require additional welding or attachment of larger electrodes to wires. The electrodes are characterized electrochemically and used to stimulate live retina in vitro. Additionally, the electrodes are coated in a water‐soluble sugar microneedle for implantation into, and subsequent recording from, visual cortex. Strong, flexible fibers are wet‐spun from a liquid crystalline dispersion of graphene oxide (LCGO), then coated with parylene‐C, and laser‐excised to create free‐standing stimulation electrodes with high charge injection capacity (14 mC cm−2). LCGO electrodes stimulated retina in vitro; water‐soluble microneedles are utilized to implant the flexible electrodes into cortical tissue enabling acquisition of neural activity.
      PubDate: 2015-05-04T10:01:41.562845-05:
      DOI: 10.1002/adfm.201500110
       
  • A Natural 3D Interconnected Laminated Composite with Enhanced Damage
           Resistance
    • Authors: Ling Li; Christine Ortiz
      Abstract: Due to their lightweight, high specific stiffness and strength, cost effectiveness, corrosion and fatigue resistance, laminated composites have been widely used in many engineering applications, such as aircraft, automobiles, sporting products, and civil infrastructure. However, delamination damage along in‐plane interfaces has been one of the issues that still remain unsolved. Although many natural load‐bearing materials are also essentially laminated composites composed of mineral and organic phases, the underlying mechanisms for antidelamination are still largely unexplored. Here it is reported that the remarkable resistance to macroscopic indentation damage in the highly mineralized shell of the bivalve Placuna placenta originates from a characteristic nanoscale structural motif, i.e., screw dislocation‐like connection centers, which join adjacent mineral layers together in the laminate structure. This leads to the formation of a complex interconnected network of microcracks surrounding the damage zone, which allows for both efficient energy dissipation and damage localization even when the shell is completely penetrated. Both theoretical analysis and experiment‐based calculations suggest that the interfacial fracture toughness is enhanced by almost two orders of magnitude in comparison to classic laminated composites without connection centers. This design strategy for achieving a 3D integrative laminate architecture can be potentially applied in the design of advanced laminated composite materials. The remarkable resistance to macroscopic mechanical damage in a highly mineralized shell of the bivalve Placuna placenta originates from a characteristic nanoscale structural motif, that is, screw dislocation‐like connection centers, which join adjacent mineral layers together in its laminated structure. This enables the formation of an interconnected network of microcracks within the damage zone, allowing for simultaneous efficient energy dissipation and damage localization.
      PubDate: 2015-05-04T10:00:58.706648-05:
      DOI: 10.1002/adfm.201500380
       
  • Rational Design of Small Molecular Donor for Solution‐Processed
           Organic Photovoltaics with 8.1% Efficiency and High Fill Factor via
           Multiple Fluorine Substituents and Thiophene Bridge
    • Authors: Jin‐Liang Wang; Qing‐Ru Yin, Jing‐Sheng Miao, Zhuo Wu, Zheng‐Feng Chang, Yue Cao, Ru‐Bo Zhang, Jie‐Yu Wang, Hong‐Bin Wu, Yong Cao
      Abstract: A series of tetrafluorine‐substituted small molecules with a D1‐A‐D2‐A‐D1 linear framework based on indacenodithiophene and difluorobenzothiadiazole is designed and synthesized for application as donor materials in solution‐processed small‐molecule organic solar cells. The impacts of thiophene π‐bridge and multiple fluorinated modules on the photophysical properties, the energy levels of the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), charge carrier mobility, the morphologies of blend films, and their photovoltaic properties as electron donor material in the photoactive layer are investigated. By incorporating multiple fluorine substituents of benzothiadiazole and inserting two thiophene spacers, the fill factor (FF), open‐circuit voltage, and short‐circuit current density are dramatically improved in comparison with fluorinated‐free materials. With the solvent vapor annealing treatment, further enhancement in charge carrier mobility and power conversion efficiency (PCE) are achieved. Finally, a high PCE of 8.1% with very‐high FF of 0.76 for BIT‐4F‐T/PC71BM is achieved without additional additive, which is among one of the highest reported for small‐molecules‐based solar cells with PCE over 8%. The results reported here clearly indicate that high PCE in solar cells based small molecules can be significantly increased through careful engineering of the molecular structure and optimization on the morphology of blend films by solvent vapor annealing. Small molecules (BIT‐4F‐T) based on indacenodithiophene (IDT) and difluorobenzothiadiazole are synthesized for bulk‐heterojunction organic solar cells (BHJ‐OSCs). Best power conversion efficiency (PCE) of 8.1% and very‐high FF of 0.76 are achieved, which is among one of the best small‐molecule donor materials in simple single‐junction organic solar cells. These exciting results verify the significant importance of multiple fluorine substituents of benzothiadiazole and two thiophene moieties for high PCE.
      PubDate: 2015-05-04T10:00:49.52161-05:0
      DOI: 10.1002/adfm.201500190
       
  • Simultaneous Detection of Diverse Glycoligand‐Receptor Recognitions
           Using a Single‐Excitation, Dual‐Emission Graphene Composite
    • Authors: Ding‐Kun Ji; Guo‐Rong Chen, Xiao‐Peng He, He Tian
      Abstract: Ligand–protein interactions (LPIs) are fundamental biological processes that manipulate a variety of cellular events. While multiple LPIs can occur concurrently or concertedly at a cellular interface, techniques which are able to simultaneously probe these diverse interactions remain challenging. Here, to the best of our knowledge, the first fluorogenic composite material (FCM) is developed that can probe diverse LPIs at a single biomimetic interface. We determined that two glycoligands coupled with fluorescence dyes with different emission colors can coassemble to a graphene oxide platform, producing an integrated FCM with a quenched fluorescence. The fluorescence of each “glycodye” is uniquely elicited upon interaction with a pairing protein (lectin) that selectively recognizes the glycoligand. Importantly, the dual emission of the FCM can be produced, on a single excitation, while both proteins exist, providing a concise means for the simultaneous probing of diverse LPIs. Simultaneous detection of diverse glycoligand‐protein recognitions is made possible using a dual‐fluorogenic composite material. This multiplex sensing material shows a dual emission, with no interference with each other on a single excitation, upon concurrent interaction with two protein receptors.
      PubDate: 2015-05-04T10:00:31.719069-05:
      DOI: 10.1002/adfm.201500448
       
  • Synthesis of Layer‐Tunable Graphene: A Combined Kinetic Implantation
           and Thermal Ejection Approach
    • Authors: Gang Wang; Miao Zhang, Su Liu, Xiaoming Xie, Guqiao Ding, Yongqiang Wang, Paul K. Chu, Heng Gao, Wei Ren, Qinghong Yuan, Peihong Zhang, Xi Wang, Zengfeng Di
      Abstract: Layer‐tunable graphene has attracted broad interest for its potentials in nanoelectronics applications. However, synthesis of layer‐tunable graphene by using traditional chemical vapor deposition method still remains a great challenge due to the complex experimental parameters and the carbon precipitation process. Herein, by performing ion implantation into a Ni/Cu bilayer substrate, the number of graphene layers, especially single or double layer, can be controlled precisely by adjusting the carbon ion implant fluence. The growth mechanism of the layer‐tunable graphene is revealed by monitoring the growth process, it is observed that the entire implanted carbon atoms can be expelled toward the substrate surface and thus graphene with designed layer number can be obtained. Such a growth mechanism is further confirmed by theoretical calculations. The proposed approach for the synthesis of layer‐tunable graphene offers more flexibility in the experimental conditions. Being a core technology in microelectronics processing, ion implantation can be readily implemented in production lines and is expected to expedite the application of graphene to nanoelectronics. By taking advantage of the dual metal substrate of Ni‐coated Cu foils, the precise control of layer number of graphene by ion implantation is demonstrated and the layer number of graphene strictly corresponds to the implantation fluence as expected. Besides, the formation mechanism is explored by the experimental analysis in detail and confirmed by the theoretical calculations.
      PubDate: 2015-05-04T10:00:26.181618-05:
      DOI: 10.1002/adfm.201500981
       
  • Radiolabeled Polymeric Nanoconstructs Loaded with Docetaxel and Curcumin
           for Cancer Combinatorial Therapy and Nuclear Imaging
    • Authors: Cinzia Stigliano; Jaehong Key, Maricela Ramirez, Santosh Aryal, Paolo Decuzzi
      Abstract: Growing evidence suggests that multifaceted diseases as cancer can be effectively tackled by hitting simultaneously different biological targets and monitoring patient‐specific responses. Combinatorial therapies, relying on the administration of two or more molecules with different cytotoxic mechanisms, are rapidly progressing in the clinic. Here, 100 nm spherical polymeric nanoconstructs (SPNs) are proposed for the combinatorial treatment of tumors by codelivering a potent antimitotic drug—docetaxel (DTXL)—and a broad spectrum anti‐inflammatory molecule—curcumin (CURC). In vitro, SPNs loaded with DTXL and CURC induce a threefold decrease in IC50 as compared to DTXL‐loaded SPNs. This synergic antitumor effect is also significant in mouse models of glioblastoma multiforme, where, after 22 d of treatment, the combinatorial approach leads to complete disease regression. At 90 d post‐treatment initiation, mice injected with DTXL + CURC SPNs have a 100% survival, whereas only 50% of the DTXL SPN treated mice survive. SPNs are also labeled with radioactive 64Cu(DOTA) molecules to document, via PET imaging, the progressive tumor mass shrinkage. Sensitization of DTXL by CURC is associated with NF‐κB downregulation and increased apoptosis. These theranostic nanoconstructs could be used for combinatorial treatment and assessment of therapeutic efficacy in other malignancies. Spherical polymeric nanoconstructs (SPNs) are multifunctional nanoparticles designed for combinatorial therapy and disease management. The platform presented here is used to codeliver docetaxel, a strong anti­tumor drug, with curcumin as sensitizing agent. SPNs are labeled with 64Cu for PET imaging to detect the delivery of SPNs and follow the therapy efficacy over time. This combinatorial approach is successful in glioblastoma xenograft mouse model.
      PubDate: 2015-05-04T10:00:16.575798-05:
      DOI: 10.1002/adfm.201500627
       
  • Fabrication and Shell Optimization of Synergistic TiO2‐MoO3
           Core–Shell Nanowire Array Anode for High Energy and Power Density
           Lithium‐Ion Batteries
    • Authors: Chong Wang; Lingxia Wu, Hai Wang, Wenhua Zuo, Yuanyuan Li, Jinping Liu
      Abstract: A novel synergistic TiO2‐MoO3 (TO‐MO) core–shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process. The nano‐MoO3 shell provides large specific capacity as well as good electrical conductivity for fast charge transfer, while the highly electrochemically stable TiO2 nanowire core (negligible volume change during Li insertion/desertion) remedies the cycling instability of MoO3 shell and its array further provides a 3D scaffold for large amount electrodeposition of MoO3. In combination of the unique electrochemical attributes of nanostructure arrays, the optimized TO‐MO hybrid anode (mass ratio: ca. 1:1) simultaneously exhibits high gravimetric capacity (ca. 670 mAh g−1; approaching the hybrid's theoretical value), excellent cyclability (>200 cycles) and good rate capability (up to 2000 mA g−1). The areal capacity is also as high as 3.986 mAh cm−2, comparable to that of typical commercial LIBs. Furthermore, the hybrid anode was assembled for the first time with commercial LiCoO2 cathode into a Li ion full cell, which shows outstanding performance with maximum power density of 1086 W kgtotal −1 (based on the total mass of the TO‐MO and LiCoO2) and excellent energy density (285 Wh kgtotal −1) that is higher than many previously reported metal oxide anode‐based Li full cells. Synergistic TiO2‐MoO3 core–shell nano­wire array anode is developed, showing high capacity (ca. 670 mAh g−1; 3.986 mAh cm−2), excellent cycleability (>200 times), and good rate performance. Ultrahigh energy density (285 Wh kgtotal −1) and power density (1086 W kgtotal −1) are further achieved for a full cell LIB device assembled using our TiO2‐MoO3 hybrid array as anode and commercial LiCoO2 film as cathode.
      PubDate: 2015-05-04T10:00:09.751932-05:
      DOI: 10.1002/adfm.201500634
       
  • Fast and Reversible Li Ion Insertion in Carbon‐Encapsulated Li3VO4
           as Anode for Lithium‐Ion Battery
    • Authors: Changkun Zhang; Huanqiao Song, Chaofeng Liu, Yaguang Liu, Cuiping Zhang, Xihui Nan, Guozhong Cao
      Abstract: Carbon‐encapsulated Li3VO4 is synthesized by a facile environmentally benign solid‐state method with organic metallic precursor VO(C5H7O2)2 being chosen as both V and carbon sources yielding a core–shell nanostructure with lithium introduced in the subsequent annealing process. The Li3VO4 encapsulated with carbon presents exceeding rate capability (a reversible capability of 450, 340, 169, and 106 mAh g−1 at 0.1 C, 10 C, 50 C, and 80 C, respectively) and long cyclic performance (80% capacity retention after 2000 cycles at 10 C) as an anode in lithium‐ion batteries. The superior performance is derived from the structural features of the carbon‐encapsulated Li3VO4 composite with oxygen vacancies in Li3VO4, which increase surface energy and could possibly serve as a nucleation center, thus facilitating phase transitions. The in situ generated carbon shell not only facilitates electron transport, but also suppresses Li3VO4 particle growth during the calcination process. The encouraging results demonstrate the significant potential of carbon encapsulated Li3VO4 for high power batteries. In addition, the simple generic synthesis method is applicable to the fabrication of a variety of electrode materials for batteries and supercapacitors with unique core–shell structure with mesoporous carbon shell. The carbon‐encapsulated Li3VO4 composite fabricated by a novel one‐step solid‐state reaction without external carbon sources presents exceeding rate capability (a reversible capability of 340, 169, and 106 mAh g−1 at 10 C, 50 C, and 80 C, respectively) and long cyclic performance (80% capacity retention after 2000 cycles at 10 C) as an anode in lithium‐ion batteries.
      PubDate: 2015-05-04T10:00:00.616088-05:
      DOI: 10.1002/adfm.201500644
       
  • Sol–Gel Metal Oxides: In‐Depth Studies on Rapid Photochemical
           Activation of Various Sol–Gel Metal Oxide Films for Flexible
           Transparent Electronics (Adv. Funct. Mater. 19/2015)
    • 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
      Pages: 2785 - 2785
      Abstract: The front cover demonstrates the fabrication of sol–gel derived metal oxide electronic devices and circuits by low‐temperature photochemical activation via in‐situ radical‐mediated reactions. On page 2807, M.‐H. Yoon, S. K. Park, and colleagues show that the rapid photoactivation process enables the conversion of the sol–gel precursors into metal oxide electronic materials directly on ultra‐flexible plastic substrates, which will serve as a general methodology in a rapid, scalable, and economic manner.
      PubDate: 2015-05-18T13:11:15.786308-05:
      DOI: 10.1002/adfm.201570125
       
  • Cell Patterning: Controllable Patterning of Different Cells Via Optical
           Assembly of 1D Periodic Cell Structures (Adv. Funct. Mater. 19/2015)
    • Authors: Hongbao Xin; Yuchao Li, Baojun Li
      Pages: 2786 - 2786
      Abstract: 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. The patterning method demonstrated by B. Li and co‐workers on page 2816 is also applicable for mammalian/human cells.
      PubDate: 2015-05-18T13:11:20.899472-05:
      DOI: 10.1002/adfm.201570126
       
  • Contents: (Adv. Funct. Mater. 19/2015)
    • Pages: 2787 - 2793
      PubDate: 2015-05-18T13:11:20.778238-05:
      DOI: 10.1002/adfm.201570127
       
  • 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
      Pages: 2794 - 2806
      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
       
  • 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
      Pages: 2807 - 2815
      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
       
  • Controllable Patterning of Different Cells Via Optical Assembly of 1D
           Periodic Cell Structures
    • Authors: Hongbao Xin; Yuchao Li, Baojun Li
      Pages: 2816 - 2823
      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
       
  • Lanthanide–Organic Framework Nanothermometers Prepared by
           Spray‐Drying
    • Authors: Zhuopeng Wang; Duarte Ananias, Arnau Carné‐Sánchez, Carlos D. S. Brites, Inhar Imaz, Daniel Maspoch, João Rocha, Luís D. Carlos
      Pages: 2824 - 2830
      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
       
  • 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
      Pages: 2831 - 2839
      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
       
  • Electronic Skin: Bioinspired Interlocked and Hierarchical Design of ZnO
           Nanowire Arrays for Static and Dynamic Pressure‐Sensitive Electronic
           Skins (Adv. Funct. Mater. 19/2015)
    • Authors: Minjeong Ha; Seongdong Lim, Jonghwa Park, Doo‐Seung Um, Youngoh Lee, Hyunhyub Ko
      Pages: 2840 - 2840
      Abstract: Flexible electronic skins (e‐skins) with static and dynamic tactile sensing capabilities are demonstrated on page 2841 by H. Ko and co‐workers based on the interlocked geometry of hierarchical polydimethylsiloxane (PDMS) micopillar arrays decorated with ZnO nanowire forests. While the e‐skin in a piezoresistive mode enables a static pressure detection with high sensitivity, the piezoelectric e‐skin mode permits the dynamic sensing of high frequency vibrations.
      PubDate: 2015-05-18T13:11:22.064661-05:
      DOI: 10.1002/adfm.201570129
       
  • 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
      Pages: 2841 - 2849
      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
       
  • 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
      Pages: 2850 - 2856
      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
       
  • 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
      Pages: 2857 - 2866
      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
       
  • 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
      Pages: 2867 - 2875
      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
       
  • 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
      Pages: 2876 - 2883
      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
       
  • 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
      Pages: 2884 - 2891
      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
       
  • 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
      Pages: 2892 - 2898
      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
       
  • Symmetric and Asymmetric Decoration of Graphene: Bimetal‐Graphene
           Sandwiches
    • Authors: Peter S. Toth; Matěj Velický, Quentin M. Ramasse, Despoina M. Kepaptsoglou, Robert A. W. Dryfe
      Pages: 2899 - 2909
      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
       
  • 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
      Pages: 2910 - 2919
      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
       
  • 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
      Pages: 2920 - 2927
      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
       
  • Theoretical Study of Rotary Freestanding Triboelectric Nanogenerators
    • Authors: Tao Jiang; Xiangyu Chen, Chang Bao Han, Wei Tang, Zhong Lin Wang
      Pages: 2928 - 2938
      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
       
  • Metal–Organic Frameworks: Lanthanide–Organic Framework
           Nanothermometers Prepared by Spray‐Drying (Adv. Funct. Mater.
           19/2015)
    • Authors: Zhuopeng Wang; Duarte Ananias, Arnau Carné‐Sánchez, Carlos D. S. Brites, Inhar Imaz, Daniel Maspoch, João Rocha, Luís D. Carlos
      Pages: 2939 - 2939
      Abstract: Nanoparticles of the first lanthanide‐organic framework prepared by a spray‐drying method are used by J. Rocha, L. D. Carlos, and team as luminescent thermometers operating in the 10–325 K range (emission quantum yield of 0.25). The system presented on page 2824 is the most sensitive cryogenic nanothermometer reported so far, combining high thermal sensitivity (5.96%.K−1 at 25 K), repeatibility (99%), and low‐temperature uncertainty (0.02 K at 25 K).
      PubDate: 2015-05-18T13:11:20.2616-05:00
      DOI: 10.1002/adfm.201570130
       
  • Photothermal Therapy: Tumor‐Penetrating Nanotherapeutics Loading a
           Near‐Infrared Probe Inhibit Growth and Metastasis of Breast Cancer
           (Adv. Funct. Mater. 19/2015)
    • Authors: Xinyu He; Xiaoyue Bao, Haiqiang Cao, Zhiwen Zhang, Qi Yin, Wangwen Gu, Lingli Chen, Haijun Yu, Yaping Li
      Pages: 2940 - 2940
      Abstract: A deep tumor‐penetrating photothermal nanotherapeutic is developed on page 2831 by Z. Zhang, Y. Li, and co‐workers by loading a near‐infrared (NIR) probe into nanoscaled polymeric carrier for simultaneous inhibition of tumor growth and metastasis. The nanotherapeutic can produce high levels of heat when exposed to NIR light. Moreover, it can penetrate into the deep interior of tumor tissues and be changed into firebombs under NIR light, surprisingly suppressing tumor growth and lung metastases of breast cancer in a single treatment.
      PubDate: 2015-05-18T13:11:15.884973-05:
      DOI: 10.1002/adfm.201570131
       
 
 
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