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  Subjects -> CHEMISTRY (Total: 831 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (584 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (66 journals)

CHEMISTRY (584 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: 31)
ACS Catalysis     Full-text available via subscription   (Followers: 27)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 16)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 17)
ACS Macro Letters     Full-text available via subscription   (Followers: 20)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 24)
ACS Nano     Full-text available via subscription   (Followers: 202)
ACS Photonics     Full-text available via subscription   (Followers: 5)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 12)
Acta Chemica Iasi     Open Access  
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 5)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 6)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 11)
Advanced Functional Materials     Hybrid Journal   (Followers: 41)
Advanced Science Focus     Free   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 24)
Advances in Chemical Science     Open Access   (Followers: 9)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 14)
Advances in Drug Research     Full-text available via subscription   (Followers: 17)
Advances in Enzyme Research     Open Access  
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 13)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 14)
Advances in Nanoparticles     Open Access   (Followers: 11)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Science     Hybrid Journal   (Followers: 37)
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: 6)
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)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
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: 86)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 21)
American Journal of Plant Physiology     Open Access   (Followers: 10)
American Mineralogist     Full-text available via subscription   (Followers: 8)
Analyst     Full-text available via subscription   (Followers: 39)
Angewandte Chemie     Hybrid Journal   (Followers: 20)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 139)
Annales UMCS, Chemia     Open Access   (Followers: 2)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
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: 10)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 12)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Antiviral Chemistry and Chemotherapy     Full-text available via subscription  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 16)
Applied Surface Science     Hybrid Journal   (Followers: 22)
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: 161)
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: 5)
Bioinspired Materials     Open Access  
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 18)
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: 23)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 16)
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: 2)
Carbohydrate Research     Hybrid Journal   (Followers: 11)
Carbon     Hybrid Journal   (Followers: 76)
Catalysis for Sustainable Energy     Open Access   (Followers: 3)

        1 2 3 4 5 6 | Last

Journal Cover   Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [41 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1616-301X - ISSN (Online) 1616-3028
   Published by John Wiley and Sons Homepage  [1597 journals]
  • Metal–Organic Polyhedra Cages Immobilized on a Plasmonic Substrate
           for Sensitive Detection of Trace Explosives
    • Abstract: A novel strategy for highly sensitive detection and discrimination of explosives is developed based on the metal–organic polyhedra (MOP)‐decorated plasmonic substrate. It is found that the careful selection of the geometric and electronic characteristics of the assembly units (organic ligands and unsaturated metals sites) embedded within the MOP cage allows for the integration of multiple weak molecular interactions in a controllable fashion and thus the MOP cage can serve as an excellent receptor for selective uptake and binding of explosives. By further grafting of the MOP cage onto a plasmonic substrate with good surface‐enhanced Raman scattering enhancement factor, the resulting sensor shows a good sensing capability to various groups of ultratrace explosives, especially the challenging aliphatic nitro‐organics. A novel strategy for highly sensitive detection and discrimination of explosives is developed based on a metal–organic polyhedra (MOP)‐decorated plasmonic substrate. MOP can serve as a receptor for selective uptake and binding of explosives. Grafting of the MOP onto a plasmonic substrate with good surface‐enhanced Raman scattering enhancement factor, the sensor shows excellent discrimination power toward explosives.
      PubDate: 2015-08-31T06:54:03.882075-05:
      DOI: 10.1002/adfm.201503071
       
  • Identification of Multiple Dityrosine Bonds in Materials Composed of the
           Drosophila Protein Ultrabithorax
    • Abstract: The recombinant protein Ultrabithorax (Ubx), a Drosophila melanogaster Hox transcription factor, self‐assembles in vitro into biocompatible materials that are remarkably extensible and strong. Here, it is demonstrated that the strength of Ubx materials is due to intermolecular dityrosine bonds. Ubx materials autofluoresce blue, a characteristic of dityrosine, and bind dityrosine‐specific antibodies. Monitoring the fluorescence of reduced Ubx fibers upon oxygen exposure reveals biphasic bond formation kinetics. Two dityrosine bonds in Ubx are identified by site‐directed mutagenesis followed by measurements of fiber fluorescence intensity. One bond is located between the N‐terminus and the homeodomain (Y4/Y296 or Y12/Y293), and another bond is formed by Y167 and Y240. Fiber fluorescence closely correlates with fiber strength, demonstrating that these bonds are intermolecular. This is the first identification of specific residues that participate in dityrosine bonds in protein‐based materials. The percentage of Ubx molecules harboring both bonds can be decreased or increased by mutagenesis, providing an additional mechanism to control the mechanical properties of Ubx materials. Duplication of tyrosine‐containing motifs in Ubx increases dityrosine content in Ubx fibers, suggesting these motifs could be inserted in other self‐assembling proteins to strengthen the corresponding materials. Amino acids that form dityrosine bonds in Ultrabithorax protein‐based materials are identified. Dityrosine content can be increased or decreased by mutagenesis, controlling the strength of the materials. These tyrosine‐containing motifs, inserted in other proteins, should increase the strength of the corresponding materials.
      PubDate: 2015-08-31T05:30:57.399011-05:
      DOI: 10.1002/adfm.201502852
       
  • Rapid and Controllable Digital Microfluidic Heating by Surface Acoustic
           Waves
    • Authors: Richie J. Shilton; Virgilio Mattoli, Marco Travagliati, Matteo Agostini, Andrea Desii, Fabio Beltram, Marco Cecchini
      Abstract: Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Within typical operating conditions, the direct acoustic heating effect is shown to lead to a maximum temperature increase of about 10 °C in microliter water droplets. The importance of decoupling droplets from other on‐chip heating sources is demonstrated. Acoustic‐heating‐driven temperature changes reach a highly stable steady‐state value in ≈3 s, which is an order of magnitude faster than previously published. This rise time can even be reduced to ≈150 ms by suitably tailoring the applied SAW‐power excitation profile. Moreover, this fast heating mechanism can lead to significantly higher temperature changes (over 40 °C) with higher viscosity fluids and can be of much interest for on‐chip control of biological and/or chemical reactions. Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Small temperature changes in typical SAW microfluidic conditions and the possibility for rapid and controllable high temperature changes, for use with lab‐on‐a‐chip devices, are shown.
      PubDate: 2015-08-28T05:39:09.845137-05:
      DOI: 10.1002/adfm.201501130
       
  • Nucleus‐Targeting Gold Nanoclusters for Simultaneous In Vivo
           Fluorescence Imaging, Gene Delivery, and NIR‐Light Activated
           Photodynamic Therapy
    • Abstract: The nucleus is one of the most important cellular organelles and molecular anticancer drugs, such as cisplatin and doxorubicin, that target DNA inside the nucleus, are proving to be more effective at killing cancer cells than those targeting at cytoplasm. Nucleus‐targeting nanomaterials are very rare. It is a grand challenge to design highly efficient nucleus‐targeting multifunctional nanomaterials that are able to perform simultaneous bioimaging and therapy for the destruction of cancer cells. Here, unique nucleus‐targeting gold nanoclusters (TAT peptide–Au NCs) are designed to perform simultaneous in vitro and in vivo fluorescence imaging, gene delivery, and near‐infrared (NIR) light activated photodynamic therapy for effective cancer cell killing. Confocal laser scanning microscopy observations reveal that TAT peptide–Au NCs are distributed throughout the cytoplasm region with a significant fraction entering into the nucleus. The TAT peptide–Au NCs can also act as DNA nanocargoes to achieve very high gene transfection efficiencies (≈81%) in HeLa cells and in zebrafish. Furthermore, TAT peptide–Au NCs are also able to sensitize formation of singlet oxygen (1O2) without the co‐presence of organic photosensitizers for the destruction of cancer cells upon NIR light photoexcitation. A unique nucleus‐targeting gold nanocluster(TAT peptide–Au NC)‐based multifunctional theranostic platform is designed to perform simultaneous in vitro and in vivo cellular fluorescence imaging, gene delivery, and intrinsic near infrared light‐activated photodynamic therapy. This is done without the co‐presence of organic photosensitizers for the effective cancer cell killing.
      PubDate: 2015-08-28T05:38:59.80469-05:0
      DOI: 10.1002/adfm.201502650
       
  • Spiro Linkage as an Alternative Strategy for Promising Nonfullerene
           Acceptors in Organic Solar Cells
    • Abstract: This work focuses on developing diketopyrrolopyrrole (DPP)‐based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF‐DPPs, have an X‐shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro‐dimer of DPP‐fluorene‐DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2‐ethylhexyl (EH), linear n‐octyl (C8), and n‐dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N,N‐positions of the DPP moiety to tune molecular interactions. SF‐DPPEH, the best candidate in SF‐DPPs family, when blended with poly(3‐hexylthiophene) (P3HT) showed a moderate crystallinity and gives a Jsc of 6.96 mA cm−2, Voc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF‐DPPC8 and SF‐DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced Jsc. Coupling DPP units with SF using an acetylene bridge yields SF‐A‐DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors. A series of spiro‐diketopyrrolopyrroles‐based nonfullerene acceptors with X‐shape is developed. The substituted alkyl side chains on the acceptors can significantly tailor their crystallinity and bulk heterojunction film morphology. When paring these acceptors with poly(3‐hexylthiophene), a dramatic variation of power conversion efficiency from 1.42% to 3.63% is observed.
      PubDate: 2015-08-27T12:11:46.881222-05:
      DOI: 10.1002/adfm.201502413
       
  • A Fully Transparent and Flexible Ultraviolet–Visible Photodetector
           Based on Controlled Electrospun ZnO‐CdO Heterojunction Nanofiber
           Arrays
    • Authors: Zhi Zheng; Lin Gan, Huiqiao Li, Ying Ma, Yoshio Bando, Dmitri Golberg, Tianyou Zhai
      Abstract: It is essential for novel photodetectors to show good photoresponses, high stability, and have facile fabrication methods. Herein, an optimized electrospinning method to fabricate a photodetector based on nanowire arrays that has a wide spectral response range is demonstrated. Arrays of ZnO‐CdO hybrid nanowires are carefully fabricated fusing ZnO and CdO portions into the same nanowires and subsequently assembling those nanowires into a regular structure. Compared to pure ZnO or CdO nanowire arrays, the hybrid arrays show comparable photocurrent/dark current ratios and response speeds, but they possess a much wider spectral response range from ultraviolet to visible light. The optoelectronic and electronic properties of the ZnO‐CdO hybrid nanowire arrays are systematically explored. Based on this, a transparent and flexible photodetector made of ZnO‐CdO hybrid nanowire arrays is fabricated. It shows a high transparency of around 95% in the spectral range of 400–800 nm and maintains its properties even after 200 bending cycles. Importantly, the developed, simple method can be directly applied to many types of substrates and a transfer of the nanowires becomes unnecessary, which guarantees a high quality of the devices. A photodetector based on ZnO‐CdO heterojunctions with a large photoresponse range and a fast response speed is fabricated. Its comprehensive photoelectric and carrier transport properties at different wavelengths, light intensities, and pressures are investigated. The detector is highly transparent at 400–800 nm and maintains its properties even after 200 bending cycles. This photodetector has a high potential to be used in multicolor optoelectronic devices.
      PubDate: 2015-08-27T12:11:26.566722-05:
      DOI: 10.1002/adfm.201502499
       
  • Elastoplastic Inverse Opals as Power‐Free Mechanochromic Sensors for
           Force Recording
    • Authors: Younghyun Cho; Su Yeon Lee, Lindsay Ellerthorpe, Gang Feng, Gaojian Lin, Gaoxiang Wu, Jie Yin, Shu Yang
      Abstract: Light‐weight, power‐free mechanochromic sensors that can change and record the reflective color depending on the magnitude and rate of the applied force are fabricated from inverse opals by infiltrating the colloidal crystals of silica particles with uncrosslinked SU‐8, followed by removal of the colloidal templates. The mechanical sensing range of the materials is high, 17.6–20.4 MPa. Due to elastoplastic deformation of the SU‐8 films, the deformed structures and thus colors can be locked after the removal of the load, therefore establishing a quantitative relationship between the mechanical force and optical responses. In comparison, mechanochromic photonic gels reported in the literature typically detect force in the range of 10–100 kPa; once the load is removed, the structure and color return back to the original ones. The mechanochromic sensors are highly sensitive: the ratio of shift in the stopband wavelength to the change in applied strain is up to 5.7 nm per percent, the highest among literature. Comparison of finite element simulations with experiments confirms the elastoplastic deformation of the films and highlights that reconfiguration of pore shape under compression plays a key role in the mechanochromic response. Power‐free and highly sensitive mechanochromic sensors that can quantitatively measure the magnitude of mechanical force are prepared from uncrosslinked SU‐8 inverse opals. They can record impact forces by exhibiting different visible colors depending on the amount and rate of the applied forces. Experiments and finite element simulations attribute this to the elastoplastic deformation of the crystals.
      PubDate: 2015-08-26T09:36:19.264936-05:
      DOI: 10.1002/adfm.201502774
       
  • TiO2 Microspheres with Controllable Surface Area and Porosity for Enhanced
           Light Harvesting and Electrolyte Diffusion in Dye‐Sensitized Solar
           Cells
    • Authors: Yong Ding; Li Zhou, Li'e Mo, Ling Jiang, Linhua Hu, Zhaoqian Li, Shuanghong Chen, Songyuan Dai
      Abstract: An optimized configuration of TiO2 microspheres in photoanodes is of great importance to prepare highly efficient dye‐sensitized solar cells (DSSCs). In this work, TiO2 microspheres with tunable diameter, pore size, and porosity are synthesized by subtly adjusting the synthesizing conditions, including ratios of deionized water, ammonia, and ethanol, respectively. TiO2 microspheres are obtained with large pore sizes and a high porosity without sacrificing specific surface areas. In addition, the effect of their porosity and pore size on the performance of DSSCs is investigated. As confirmed by the dye‐loading ability and electrolyte diffusion resistance, the large mesopores and the high porosity of the TiO2 microspheres can improve dye adsorption and facilitate electrolyte diffusion, giving rise to a high light‐harvesting and electron collection efficiency. Consequently, the highest photocurrent of 19.21 mA cm−2 and a power conversion efficiency of 9.98% are obtained by using the TiO2 microspheres with the highest porosity, compared with a 9.29% efficiency demonstrated by the lowest porosity (an improvement of 7.4%). By modifying the interconnection and the external pores of the microspheres photoanode, a high efficiency of 11.67% is achieved for a DSSC based on the most potent TiO2 microspheres. Mesoporous TiO2 microspheres with controllable diameter, pore size, and porosity are synthesized. The porosity of the microspheres can be easily tuned without sacrificing the specific surface area by adjusting the content of ethanol. The large porosity of microspheres shows an abundant dye adsorption, rapid dye regeneration, and sufficient electrolyte diffusion, resulting in a higher efficiency of 11.67%.
      PubDate: 2015-08-26T02:41:38.525776-05:
      DOI: 10.1002/adfm.201502224
       
  • Living Cells Directly Growing on a DNA/Mn3(PO4)2‐Immobilized and
           Vertically Aligned CNT Array as a Free‐Standing Hybrid Film for
           Highly Sensitive In Situ Detection of Released Superoxide Anions
    • Authors: Fang Xin Hu; Yue Jun Kang, Feng Du, Lin Zhu, Yu Hua Xue, Tao Chen, Li Ming Dai, Chang Ming Li
      Abstract: It is important to detect reactive oxygen species (ROS) in situ for investigation of various critical biological processes, and this is however very challenging because of the limited sensitivity or/and selectivity of existing methods that are mainly based on sensing ROS released by cells with short lifetimes and low concentrations in a culture medium. Here, a new approach is reported to directly grow living cells on DNA/Mn3(PO4)2‐immobilized and vertically aligned carbon nanotube (VACNT) array nanostructure as a smart free‐standing hybrid film, of which the DNA/Mn3(PO4)2 and VACNT provide high electroactivity and excellent electron transport, respectively, while the directly grown cell on the nanostructure offers short diffusion distance to reaction sites, thus constructing a highly sensitive in situ method for detection of cancer‐cell‐released ROS under drug stimulations. Compared to the measured ROS released by cells in a culture medium, the detection sensitivity with this constructed hybrid film increases by more than six times, which implies that ROS molecules (superoxide anions) secreted from living cells are immediately captured by this smart structure without diffusion process or with extremely short diffusion distance. This design considerably reduces the time from release to detection of the target molecules, minimizing the potential molecular decay due to the short lifetime or high reactivity. A DNA/Mn3(PO4)2‐immobilized and vertically aligned carbon nanotube (VACNT) array nanostructure is applied as a smart free‐standing hybrid film for directly growing living cells and investigating their electrochemical behaviors in response to drug stimulation. This holds a great promise for the fabrication of next‐generation biomedical devices for living cell assays, drug screening, and monitoring cell activity in situ.
      PubDate: 2015-08-25T08:37:52.127952-05:
      DOI: 10.1002/adfm.201502341
       
  • Masthead: (Adv. Funct. Mater. 32/2015)
    • PubDate: 2015-08-25T04:04:25.182366-05:
      DOI: 10.1002/adfm.201570217
       
  • Efficient Broadband Triplet–Triplet Annihilation‐Assisted
           Photon Upconversion at Subsolar Irradiance in Fully Organic Systems
    • Authors: Angelo Monguzzi; Sergey Borisov, Jacopo Pedrini, Ingo Klimant, Mario Salvalaggio, Paolo Biagini, Fabio Melchiorre, Clelia Lelii, Francesco Meinardi
      Abstract: The latest trend in solar cell technology is to develop photon managing processes that adapt the solar emission to the spectral range at which the devices show the largest intrinsic efficiency. Triplet–triplet annihilation‐assisted photon upconversion (sTTA‐UC) is currently the most promising process to blue‐shift sub‐bandgap photons at solar irradiance, even if the narrow absorption band of the employed chromophores limits its application. In this work, we demonstrate how to obtain broadband sTTA‐UC at sub‐solar irradiance, by enhancing the system's light‐harvesting ability by way of an ad‐hoc synthesized family of chromophores with complementary absorption properties. The overall absorptance is boosted, thus doubling the number of upconverted photons and significantly reducing the irradiance required to achieve the maximum upconversion yield. An outstanding yield of ≈10% is obtained under broadband air mass (AM) 1.5 conditions, which allows a DSSC device to operate by exploiting exclusively sub‐bandgap photons. Broadband triplet–triplet annihilation‐assisted photon upconversion is demonstrated at subsolar irradiance by the simultaneous use of several light harvesters. An unprecedented yield of 10% is obtained under air mass (AM) 1.5 conditions in a fully organic system, which allows a dye‐sensitized solar cell device to operate by exploiting exclusively sub‐bandgap photons.
      PubDate: 2015-08-25T03:30:59.35226-05:0
      DOI: 10.1002/adfm.201502507
       
  • Recent Advances in Electrospun Nanofibrous Scaffolds for Cardiac Tissue
           Engineering
    • Authors: Guoxu Zhao; Xiaohui Zhang, Tian Jian Lu, Feng Xu
      Abstract: Cardiovascular diseases remain the leading cause of human mortality worldwide. Some severe symptoms, including myocardial infarction and heart failure, are difficult to heal spontaneously or under systematic treatment due to the limited regenerative capacity of the native myocardium. Cardiac tissue engineering has emerged as a practical strategy to culture functional cardiac tissues and relieve the disorder in myocardium when implanted. In cardiac tissue engineering, the design of a scaffold is closely relevant to the function of the regenerated cardiac tissues. Nanofibrous materials fabricated by electrospinning have been developed as desirable scaffolds for tissue engineering applications because of the biomimicking structure of protein fibers in native extra cellular matrix. The versatilities of electrospinning on the polymer component, the fiber structure, and the functionalization with bioactive molecules have made the fabrication of nanofibrous scaffolds with suitable mechanical strength and biological properties for cardiac tissue engineering feasible. Here, an overview of recent advances in various electrospun scaffolds for engineering cardiac tissues, including the design of advanced electrospun scaffolds and the performance of the scaffolds in functional cardiac tissue regeneration, is provided with the aim to offer guidance in the innovation of novel electrospun scaffolds and methods for improving their potential for cardiac tissue engineering applications. Electrospinning has shown great potential for cardiac tissue engineering applications, as a controllable and versatile technique for fabricating nanofibrous scaffolds. An overview of recent advances in various electrospun scaffolds for engineering functional cardiac tissues is provided, with emphasis on the fabrication of advanced electrospun scaffolds and design strategies to improve performance in cardiac tissue engineering applications.
      PubDate: 2015-08-21T07:06:09.381847-05:
      DOI: 10.1002/adfm.201502142
       
  • A Graphene‐Based Vacuum Transistor with a High ON/OFF Current Ratio
    • Authors: Gongtao Wu; Xianlong Wei, Zhiyong Zhang, Qing Chen, Lianmao Peng
      Abstract: A graphene‐based vacuum transistor (GVT) with a high ON/OFF current ratio is proposed and experimentally realized by employing electrically biased graphene as the electron emitter. The states of a GVT are switched by tuning the bias voltage applied to the graphene emitter with an ON/OFF current ratio up to 106, a subthreshold slope of 120 mV dec−1 and low working voltages of
      PubDate: 2015-08-21T07:03:57.30286-05:0
      DOI: 10.1002/adfm.201502034
       
  • Reversible Switching Phenomenon in Diarylethene Molecular Devices with
           Reduced Graphene Oxide Electrodes on Flexible Substrates
    • Abstract: Photoswitching molecular electronic devices with reduced graphene oxide (rGO) top electrodes on flexible substrates are fabricated and characterized. It has been reported previously that diarylethene molecular devices with poly‐(3,4‐ethylenedioxythiophene) stabilized with poly‐(4‐styrenesulfonic acid)/Au top electrodes can hold two stable electrical conductance states when the devices are exposed to UV or visible light during device fabrication. However, those devices fail to show the reversible switching phenomenon in response to illumination after device fabrication. By employing conducting and transparent rGO top electrodes, it is demonstrated that the diarylethene molecular devices show a reversible switching phenomenon, i.e., the fabricated devices change their conductance state in response to the alternating illumination with UV and visible light. Furthermore, the molecular devices with rGO top electrodes also exhibit good longtime stability and reliable electrical characteristics when subjected to various mechanical stresses (bending radius down to 5 mm and bending cycle over 104). The photoswitching characteristics of diarylethene molecular devices with reduced graphene oxide (rGO) electrodes on flexible substrates are studied. The diarylethene molecular devices with rGO electrodes can be converted from the open state to the closed state or vice versa with UV or visible light. The reversible photoswitching of these devices is successfully demonstrated with UV or visible light illumination.
      PubDate: 2015-08-21T07:03:48.952419-05:
      DOI: 10.1002/adfm.201502312
       
  • Magnetically Induced Fog Harvesting via Flexible Conical Arrays
    • Authors: Yun Peng; Yaxu He, Shuai Yang, Shuang Ben, Moyuan Cao, Kan Li, Kesong Liu, Lei Jiang
      Abstract: Water is the driving force of all nature. Securing freshwater has been one of the most important issues throughout human history, and will be important in the future, especially in the next decade. Fog is ubiquitous in nature and is therefore considered as an alternative and sustainable freshwater resource. Nature has long served as a source of inspiration to develop new fog‐harvesting technologies. However, the collection of freshwater from static fog is still a challenge for the existing bio‐inspired fog‐harvesting systems. Herein, magnetically induced fog harvesting under windless conditions through the integration of cactus‐inspired spine structures and magnetically responsive flexible conical arrays is reported. Under an external magnetic field, static fog can be spontaneously and continuously captured and transported from the tip to the base of the spine due to the Laplace pressure difference. This work demonstrates the advantage of collecting fog water, especially in windless regions, which provides a new avenue for fog harvesting and can serve as a source of inspiration to further optimizations of existing fog‐water‐harvesting strategies. A magnetically induced fog collector is fabricated through the integration of cactus‐inspired spine structures and magnetically responsive flexible conical arrays. Quasistatic fog water can be spontaneously and continuously captured and directionally transported, driven by the external magnetic field and the Laplace pressure difference. This work opens a new avenue for fog‐harvesting systems under windless conditions.
      PubDate: 2015-08-21T07:03:11.448167-05:
      DOI: 10.1002/adfm.201502745
       
  • High‐Efficiency Water‐Transport Channels using the Synergistic
           Effect of a Hydrophilic Polymer and Graphene Oxide Laminates
    • Authors: Kang Huang; Gongping Liu, Jie Shen, Zhenyu Chu, Haoli Zhou, Xuehong Gu, Wanqin Jin, Nanping Xu
      Abstract: Graphene oxide (GO) laminates possess unprecedented fast water‐transport channels. However, how to fully utilize these unique channels in order to maximize the separation properties of GO laminates remains a challenge. Here, a bio‐inspired membrane that couples an ultrathin surface water‐capturing polymeric layer (
      PubDate: 2015-08-19T10:07:17.944363-05:
      DOI: 10.1002/adfm.201502205
       
  • Unusual Circularly Polarized Photocatalytic Activity in Nanogapped
           Gold–Silver Chiroplasmonic Nanostructures
    • Authors: Changlong Hao; Liguang Xu, Wei Ma, Xiaoling Wu, Libing Wang, Hua Kuang, Chuanlai Xu
      Abstract: Gold‐gap‐silver nanostructures (GGS NSs) with interior nanobridged gaps are enantioselectively fabricated. Guided by l/d‐cysteine, the GGS‐L/D (L/D represents l/d‐cysteine) NSs show reversed plasmon‐induced circular dichroism (CD) signals in the visible region. It is found that the nanogap plays a key role in the plasmonic CD of GGS NSs and the chiroptical response can be tailored by adjusting the amount of cysteine. The anisotropy factor of GGS‐L/D NSs with a 0.5 nm interior gap at 430 nm is as high as ≈0.01. The circularly polarized photocatalytic activity of GGS NSs is examined. It is shown that upon irradiation with left‐circularly polarized light, the catalytic efficiency of GGS‐L NSs is 73‐fold and 17‐fold higher than that of Au nanoparticles (NPs) and Au@Ag core–shell NPs, respectively. Upon irradiation with right‐circularly polarized light, the catalytic activity of GGS‐D NSs is about 71 times and 17 times higher than that of Au NPs and Au@Ag core–shell NPs, respectively. These unique chiral NSs with high plasmonic response can be applied to enantioselective catalysis. Guided by l/d‐cysteine, gold‐gap‐silver nanostructures (GGS NSs) with interior nanogaps, which display exceptionally strong chiroptical activity in the visible light region, are prepared. Based on the fabricated GGS NSs, unexpected circularly polarized photocatalytic activity is discovered under the irradiation with circularly polarized light.
      PubDate: 2015-08-18T06:27:32.86164-05:0
      DOI: 10.1002/adfm.201502429
       
  • Rapid and Facile Formation of P3HT Organogels via Spin Coating: Tuning
           Functional Properties of Organic Electronic Thin Films
    • Authors: Cameron S. Lee; Wen Yin, Adam P. Holt, Joshua R. Sangoro, Alexei P. Sokolov, Mark D. Dadmun
      Abstract: Poly(3‐hexyl thiophene) (P3HT) is widely regarded as the benchmark polymer when studying the physics of conjugated polymers used in organic electronic devices. P3HT can self‐assemble via π–π stacking of its backbone, leading to an assembly and growth of P3HT fibrils into 3D percolating organogels. These structures are capable of bridging the electrodes, providing multiple pathways for charge transport throughout the active layer. Here, a novel set of conditions is identified and discussed for P3HT organogel network formation via spin coating by monitoring the spin‐coating process from various solvents. The development of organogel formation is detected by in situ static light scattering, which measures both the thinning rate by reflectance and structural development in the film via off‐specular scattering during film formation. Optical microscopy and thermal annealing experiments provide ex situ confirmation of organogel fabrication. The role of solution characteristics, including solvent boiling point, P3HT solubility, and initial P3HT solution concentration on organogel formation, is examined to correlate these parameters to the rate of film formation, organogel‐onset concentration, and overall network size. The correlation of film properties to the fabrication parameters is also analyzed within the context of the hole mobility and density‐of‐states measured by impedance spectroscopy. Poly(3‐hexylthiophene) organogels offer exploitable electronic properties. These gels agglomerate into 3D percolating networks that span the active layer of a thin‐film device. Novel spin‐coating conditions that produce organogels in a rapid deposition process are discussed, including the interplay of kinetics and solution thermodynamics in organogel formation, control of the network size, and the correlation of structure to electronic properties.
      PubDate: 2015-08-18T06:27:15.581639-05:
      DOI: 10.1002/adfm.201501707
       
  • Van der Waals p–n Junction Based on an Organic–Inorganic
           Heterostructure
    • Authors: Fucai Liu; Wai Leong Chow, Xuexia He, Peng Hu, Shoujun Zheng, Xingli Wang, Jiadong Zhou, Qundong Fu, Wei Fu, Peng Yu, Qingsheng Zeng, Hong Jin Fan, Beng Kang Tay, Christian Kloc, Zheng Liu
      Abstract: Organic–inorganic heterostructures are an emerging topic that is very interesting for optoelectronics. Here, non‐conventional p–n junctions are investigated using organic rubrene single crystal and 2D MoS2 as the p‐ and n‐type semiconducting materials, respectively. The current‐rectifying behavior is clearly observed in the junction device. The rectification ratio can be electrically tuned by the gate voltage due to the 2D nature of the heterostructure. The devices also show good photoresponse properties with a photoresponsivity of ≈500 mA W−1 and a fast response time. These findings suggest a new route to facilitate the design of nanoelectronic and optoelectronic devices based on layered inorganics and organics. Through the marriage of MoS2 and rubrene, a novel organic–inorganic van der Waals heterostructure is demonstrated with a gate‐tunable rectifying behavior. Good photoresponse properties are also obtained from the heterojunction with a photoresponsitivity of 500 A mW–1 and a fast response time.
      PubDate: 2015-08-18T06:26:12.276601-05:
      DOI: 10.1002/adfm.201502316
       
  • Modular and Versatile Spatial Functionalization of Tissue Engineering
           
    • Authors: Rachael H. Harrison; Joseph A. M. Steele, Robert Chapman, Adam J. Gormley, Lesley W. Chow, Muzamir M. Mahat, Lucia Podhorska, Robert G. Palgrave, David J. Payne, Shehan P. Hettiaratchy, Iain E. Dunlop, Molly M. Stevens
      Abstract: Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end‐functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly‐ε‐caprolactone is end functionalized with either a polymerization‐initiating group or a cell‐binding peptide motif cyclic Arg‐Gly‐Asp‐Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization‐initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin‐coupled moieties. These combined processing techniques result in an effective bilayered and dual‐functionality scaffold with a cell‐adhesive surface and an opposing antifouling non‐cell‐adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine. Cell‐adhesive and opposing antifouling surfaces are produced within a single construct for use in tissue engineering of biological interfaces. Different functional groups are zonally organized within a continuously electrospun scaffold before postprocessing modification with a versatile, surface‐initiated controlled radical polymerization production of an effective antifouling polymer bottlebrush in a predetermined, specific location.
      PubDate: 2015-08-17T11:12:05.924333-05:
      DOI: 10.1002/adfm.201501277
       
  • Peptide Length and Dopa Determine Iron‐Mediated Cohesion of Mussel
           Foot Proteins
    • Authors: Saurabh Das; Nadine R. Martinez Rodriguez, Wei Wei, J. Herbert Waite, Jacob N. Israelachvili
      Abstract: Mussel adhesion to mineral surfaces is widely attributed to 3,4‐dihydroxyphenylalanine (Dopa) functionalities in the mussel foot proteins (mfps). Several mfps, however, show a broad range (30%–100%) of tyrosine (Tyr) to Dopa conversion suggesting that Dopa is not the only desirable outcome for adhesion. Here, a partial recombinant construct of mussel foot protein‐1 (rmfp‐1) and short decapeptide dimers with and without Dopa are used and both their cohesive and adhesive properties on mica are assessed using a surface forces apparatus. Our results demonstrate that at low pH, both the unmodified and Dopa‐containing rmfp‐1s show similar energies for adhesion to mica and self–self‐interaction. Cohesion between two Dopa‐containing rmfp‐1 surfaces can be doubled by Fe3+ chelation, but remains unchanged with unmodified rmfp‐1. At the same low pH, the Dopa‐modified short decapeptide dimer did not show any change in cohesive interactions even with Fe3+. The results suggest that the most probable intermolecular interactions are those arising from electrostatic (i.e., cation–π) and hydrophobic interactions. It is also shown that Dopa in a peptide sequence does not by itself mediate Fe3+ bridging interactions between peptide films: peptide length is a crucial enabling factor. Fe3+‐mediated bridging of the mussel foot proteins (mfps) is attributed to two equally influential parameters: peptide architecture and 3,4‐dihydroxyphenyl­alanine (Dopa) residues in the protein. In addition, serial “hydrogen bonding” and cation–π interactions between the aromatic residues in the protein and a mineral surface are more probable than bidentate H‐bonding interactions in adhering mfps to the surface.
      PubDate: 2015-08-17T11:11:52.250315-05:
      DOI: 10.1002/adfm.201502256
       
  • A High‐Reliability Kevlar Fiber‐ZnO Nanowires Hybrid
           Nanogenerator and its Application on Self‐Powered UV Detection
    • Authors: Lu Zhang; Suo Bai, Chen Su, Youbin Zheng, Yong Qin, Chen Xu, Zhong Lin Wang
      Abstract: A microfiber‐nanowire hybrid structure is the fundamental component for a wearable piezoelectric nanogenerator (PENG) for harvesting body motion energy. Here, a novel approach combining surface coating and plasma etching techniques is reported to enhance the mechanical reliability of Kevlar microfiber‐ZnO nanowires (NWs) hybrid structure that is used for PENG. After treatment, the hybrid structure has dramatically improved high flexibility, robustness, and durability. On the basis of the coupled piezoelectric and semiconducting properties of ZnO, the processed Kevlar fibers covered with ZnO NWs are utilized to fabricate a 2D nanogenerator (2DNG). The open‐circuit voltage and short‐circuit current of the 2DNG are 1.8 mV and 4.8 pA, respectively. Furthermore, the 2DNG is successfully employed to quantitatively detect UV intensity from 0.2 to 1 mW cm−2 as a self‐powered system. A novel approach to combining surface coating and plasma etching techniques is introduced to enhance the mechanical reliability of Kevlar microfiber‐ZnO nano­wires hybrid structure. This is successfully applied to fabricate a high‐reliability Kevlar fiber‐ZnO nanowire hybrid nanogenerator. The nanogenerator can act as a self‐powered system to detect the UV intensity quantitatively.
      PubDate: 2015-08-17T11:08:20.593913-05:
      DOI: 10.1002/adfm.201502646
       
  • Polyazines and Polyazomethines with Didodecylthiophene Units for Selective
           Dispersion of Semiconducting Single‐Walled Carbon Nanotubes
    • Authors: Widianta Gomulya; Vladimir Derenskyi, Erika Kozma, Mariacecilia Pasini, Maria Antonietta Loi
      Abstract: Polymer wrapped single‐walled carbon nanotubes (SWNTs) have been demonstrated to be a very efficient technique to obtain high purity semiconducting SWNT solutions. However, the extraction yield of this technique is low compared to other techniques. Poly‐alkyl‐thiophenes have been reported to show higher extraction yield compare to polyfluorene derivatives. Here, the affinity for semiconducting SWNTs of two polymers with a backbone containing didodecylthiophene units interspersed with N atoms is reported. It is demonstrated that one of the polymers, namely, poly(2,5‐dimethylidynenitrilo‐3,4‐didodecylthienylene) (PAMDD), has very high semiconducting SWNT extraction yield compared to the poly(3,4‐didodecylthienylene)azine (PAZDD). The dissimilar wrapping efficiency of these two polymers for semiconducting SWNTs is attributed to the interplay between the affinity for the nitrogen atoms of the highly polarizable walls of SWNTs and the mechanical flexibility of the polymer backbones. Photoluminescence (PL) measurements demonstrate the presence of metallic tubes and SWNT bundles in the sample selected with PAZDD and higher purity of SWNT‐PAMDD samples. The high purity of the semiconducting SWNTs selected by PAMDD is further demonstrated by the high performance of the solution‐processed field‐effect transistors (FETs) fabricated using a blade coating technique, which exhibit hole mobilities up to 33.3 cm2 V−1 s−1 with on/off ratios of 106. A single‐wall carbon nanotube (SWNT) selective dispersion is obtained using polyazines and polyazomethines. Both polymers have didodecylthiophene units with direct nitrogen atoms in their backbone. The additional benzene ring in polyazomethines, which results in a stiffer polymer backbone, triggers different interaction with SWNTs. The high extraction yield of the SWNT dispersion by polyazomethines is essential for large‐scale separation of SWNT.
      PubDate: 2015-08-17T10:59:16.251924-05:
      DOI: 10.1002/adfm.201502912
       
  • Revisiting Metal Sulfide Semiconductors: A Solution‐Based General
           Protocol for Thin Film Formation, Hall Effect Measurement, and Application
           Prospects
    • Abstract: Nanostructured thin films of metal sulfides (MS) are highly desirable materials for various optoelectronic device applications. However, a general low‐temperature protocol that describes deposition of varieties of MS structures, especially in their film form is still not available in literatures. Here, a simple and highly effective general solution‐based deposition protocol for highly crystalline and well‐defined nanostructured MS thin films from ethanol on variety of conducting and non‐conducting substrates is presented. The films display remarkable electronic properties such as high carrier mobility and high conductivity. When NiS thin film deposited on a flexible polyethylene terephthalate (PET) substrate is used as a fluorine doped tin oxide (FTO)‐free counter electrode in dye‐sensitized solar cells, it exhibits a solar‐to‐electric power conversion efficiency of 9.27 ± 0.26% with the highest conversion efficiency as high as 9.50% (vs 8.97 ± 0.07% exhibited by Pt‐electrode). In addition, the NiS film deposited on a Ti‐foil has demonstrated an outstanding catalytic activity for the hydrogen and oxygen evolution reactions from water. A solution‐based general protocol for the deposition of large varieties of metal sulfide thin films from an ethanol bath on a variety of conducting and non‐conducting substrates is presented. As a proof‐of‐concept for application, a NiS film is investigated as an example, and it is demonstrated to be an outstanding electrocatalytic counter electrode for triiodide reduction in dye‐sensitized solar cells. It also exhibits potentially good electrocatalyst activity for the hydrogen evolution reaction and oxygen evolution reaction from water.
      PubDate: 2015-08-14T08:28:04.800969-05:
      DOI: 10.1002/adfm.201500964
       
  • Biocompatible and Flexible Chitosan‐Based Resistive Switching Memory
           with Magnesium Electrodes
    • Abstract: A flexible and transparent resistive switching memory based on a natural organic polymer for future flexible electronics is reported. The device has a coplanar structure of Mg/Ag‐doped chitosan/Mg on plastic substrate, which shows promising nonvolatile memory characteristics for flexible memory applications. It can be easily fabricated using solution processes on flexible substrates at room temperature and indicates reliable memory operations. The elucidated origin of the bipolar resistive switching behavior is attributed to trap‐related space‐charge‐limited conduction in high resistance state and filamentary conduction in low resistance state. The fabricated devices exhibit memory characteristics such as low power operation and long data retention. The proposed biocompatible memory device with transient electrodes is based on naturally abundant materials and is a promising candidate for low‐cost memory applications. Devices with natural substrates such as chitosan and rice paper are also fabricated for fully biodegradable resistive switching memory. This work provides an important step toward developing a flexible resistive switching memory with natural polymer films for application in flexible and biodegradable nanoelectronic devices. A transparent and flexible resistive switching memory is fabricated using a natural organic polymer by solution processes. The proposed memory device is based on naturally abundant polymers with a coplanar structure of Mg/Ag‐doped chitosan/Mg. The biocompatible and biodegradable memory device shows promising nonvolatile characteristics as a candidate for the next generation of flexible memory applications.
      PubDate: 2015-08-14T08:27:41.772524-05:
      DOI: 10.1002/adfm.201502592
       
  • Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches:
           Synthesis and Application for Efficient Oxygen Reduction
    • Authors: Jing Wei; Yaoxin Hu, Yan Liang, Biao Kong, Jin Zhang, Jingchao Song, Qiaoliang Bao, George P. Simon, San Ping Jiang, Huanting Wang
      Abstract: A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m2 g−1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm−2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐Nx/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐Nx/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media. A zeolitic‐imidazolate‐framework nanocrystal layer‐protected carbonization route is developed to prepare N‐doped carbon/graphene nano‐sandwiches. These act as a highly active and stable nonprecious metal catalyst for oxygen reduction.
      PubDate: 2015-08-13T13:36:32.631755-05:
      DOI: 10.1002/adfm.201502311
       
  • Induction of Potent Antitumor Immunity by Sustained Release of Cationic
           Antigen from a DNA‐Based Hydrogel with Adjuvant Activity
    • Authors: Yuka Umeki; Kohta Mohri, Yohji Kawasaki, Hiroshi Watanabe, Rei Takahashi, Yuki Takahashi, Yoshinobu Takakura, Makiya Nishikawa
      Abstract: Previous studies indicate that immunostimulatory DNA‐based injectable hydrogels harboring unmethylated cytosine‐phosphate‐guanine (CpG) dinucleotides meet the requirements of an effective antigen delivery system, including safety, biodegradability, ease of administration, and stimulation of the innate immune system. However, rapid release of the model antigen ovalbumin (OVA) from the hydrogel limits its potential. Here, the aim is to achieve sustained OVA release from a DNA hydrogel through cationization of the antigen. Ethylenediamine (ED)‐conjugated cationized OVA (ED‐OVA), but not OVA, forms a complex with hexapod‐like structured DNA, a component of the DNA hydrogel. The release of ED‐OVA from the hydrogel is significantly slower than that of OVA. ED‐OVA mixed with CpG DNA hydrogel efficiently binds to mouse dendritic DC2.4 cells and results in high antigen presentation. Intratumoral injections of ED‐OVA/CpG DNA hydrogel significantly delays tumor growth of OVA‐expressing EG7‐OVA cells in mice. Then, a cationic OVA peptide antigen (R8‐L2‐pepI) consisting of an OVA MHC class I epitope, octaarginine, and a linker is designed. Intratumoral injections of R8‐L2‐pepI/CpG DNA hydrogel eradicate tumors in five out of six mice. Thus, it is concluded that a vaccine consisting of immunostimulatory CpG DNA hydrogel and cationized antigens can be effective for cancer immunotherapy. An immunostimulatory DNA hydrogel‐based sustained release system using cationized antigen that can electrostatically interact with DNA is developed. This system can induce antigen‐specific immune responses, which leads to effective inhibition of antigen‐positive tumor growth in mice. This provides experimental evidence for future clinical applications of this system to induce potent antitumor immunity.
      PubDate: 2015-08-13T13:36:26.131562-05:
      DOI: 10.1002/adfm.201502139
       
  • Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as
           Multifunctional Electrocatalysts
    • Authors: Xien Liu; Wen Liu, Minseong Ko, Minjoon Park, Min Gyu Kim, Pilgun Oh, Sujong Chae, Suhyeon Park, Anix Casimir, Gang Wu, Jaephil Cho
      Abstract: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) along with hydrogen evolution reaction (HER) have been considered critical processes for electrochemical energy conversion and storage through metal‐air battery, fuel cell, and water electrolyzer technologies. Here, a new class of multifunctional electrocatalysts consisting of dominant metallic Ni or Co with small fraction of their oxides anchored onto nitrogen‐doped reduced graphene oxide (rGO) including Co‐CoO/N‐rGO and Ni‐NiO/N‐rGO are prepared via a pyrolysis of graphene oxide and cobalt or nickel salts. Ni‐NiO/N‐rGO shows the higher electrocatalytic activity for the OER in 0.1 m KOH with a low overpotential of 0.24 V at a current density of 10 mA cm−2, which is superior to that of the commercial IrO2. In addition, it exhibits remarkable activity for the HER, demonstrating a low overpotential of 0.16 V at a current density of 20 mA cm−2 in 1.0 m KOH. Apart from similar HER activity to the Ni‐based catalyst, Co‐CoO/N‐rGO displays the higher activity for the ORR, comparable to Pt/C in zinc‐air batteries. This work provides a new avenue for the development of multifunctional electrocatalysts with optimal catalytic activity by varying transition metals (Ni or Co) for these highly demanded electrochemical energy technologies. A new class of multifunctional electrocatalysts composed of Co‐CoO/N‐rGO and Ni‐NiO/N‐rGO, via a pyrolysis of graphene oxide and cobalt or nickel salts is synthesized. The two catalysts show excellent activities for oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), or oxygen evolution reaction (OER). In particularly, Co‐CoO/N‐rGO shows comparable performance to Pt/C in zinc‐air batteries.
      PubDate: 2015-08-13T13:36:19.105644-05:
      DOI: 10.1002/adfm.201502217
       
  • A High‐Power Symmetric Na‐Ion Pseudocapacitor
    • Abstract: Batteries and supercapacitors are critical devices for electrical energy storage with wide applications from portable electronics to transportation and grid. However, rechargeable batteries are typically limited in power density, while supercapacitors suffer low energy density. Here, a novel symmetric Na‐ion pseudocapacitor with a power density exceeding 5.4 kW kg−1 at 11.7 A g−1, a cycling life retention of 64.5% after 10 000 cycles at 1.17 A g−1, and an energy density of 26 Wh kg−1 at 0.585 A g−1 is reported. Such a device operates on redox reactions occurring on both electrodes with an identical active material, viz., Na3V2(PO4)3 encapsulated inside nanoporous carbon. This device, in a full‐cell scale utilizing highly reversible and high‐rate Na‐ion intercalational pseudocapacitance, can bridge the performance gap between batteries and supercapacitors. The characteristics of the device and the potentially low‐cost production make it attractive for hybrid electric vehicles and low‐maintenance energy storage systems. A novel symmetric Na‐ion pseudocapacitor that operates on oxidation–reduction reactions occurring on both electrodes with an identical active material, viz., Na3V2(PO4)3 encapsulated inside nano­porous carbon, is designed. When used in a full‐cell utilizing highly reversible, high‐rate, and cost‐effective Na‐ion intercalational pseudocapacitance, this device can bridge the performance gap between batteries and supercapacitors.
      PubDate: 2015-08-13T13:36:13.843856-05:
      DOI: 10.1002/adfm.201502433
       
  • pH‐Responsive Round‐Way Motions of a Smart Device through
           Integrating Two Types of Chemical Actuators in One Smart System
    • Authors: Lingling Yu; Mengjiao Cheng, Mengmeng Song, Dequn Zhang, Meng Xiao, Feng Shi
      Abstract: Smart motions of objects from the submicrometer to millimeter scale through chemical control with stimulus‐responsive way are significant to achieve various applications. However, the intelligence of the current devices with chemical responding system remains to be improved; especially, achieving a round‐way motion is still a challenge. Therefore, two types of actuators are simultaneously integrated into single smart device at the opposite ends to achieve cooperated functions in an orderly manner. One actuator is the pH‐responsive power supply of hydrogen bubbles produced from the reaction between magnesium and HCl. The smart device undergoes on–off–on locomotion through control over the solution pH values by using the pH‐responsive actuator of magnesium–HCl system. The other actuator is the hydrogen peroxide‐responsive system of oxygen bubbles generated through the decomposition of hydrogen peroxide catalyzed by platinum aggregates. When introducing hydrogen peroxide solution into the system, the generated oxygen bubbles at the opposite end of the device to push the device backward for round‐way motions. For the first time, two different types of actuators are simultaneously integrated into single smart device without disturbing each other, which realize pH‐responsive round‐way motions of the smart device and improve the system intelligence for further applications. To improve the intelligence of smart devices and realize round‐way smart motions, a smart device is fabricated with two types of actuators of magnesium–acid system and platinum‐hydrogen‐peroxide system at the opposite ends. Under acidic conditions, the magnesium reacts with acid to propel the device forward; changing to alkaline, the device stops motion; adding hydrogen peroxide, it moves back.
      PubDate: 2015-08-13T13:35:18.531003-05:
      DOI: 10.1002/adfm.201502447
       
  • A Multiple‐Functional Ag/SiO2/Organic Based Biomimetic Nanocomposite
           Membrane for High‐Stability Protein Recognition and Cell
           Adhesion/Detachment
    • Authors: Yilin Wu; Ming Yan, Jiuyun Cui, Yongsheng Yan, Chunxiang Li
      Abstract: Biomimetic multilevel structured membrane materials have great potential for energy‐efficient chemical separations and biomedical applications. The current study represents a simple, yet efficient, method to obtain the biomimetic protein separation membrane and controllable cell culture substrate with high stability, selectivity, and antibacterial property. Here, a molecular imprinting methodology is reported to introduce the high‐biocompatible protein ovalbumin (Ova) to a multilevel Ag/SiO2/organic based molecularly imprinted membranes (ASO‐MIMs), which have made significant achievements in protein identification and controllable growth of liver cells in vitro platform. Interestingly, the relative morphological observations of the adhered cells and in vitro viability tests show no significant difference between the ASO‐MIMs binding with 13.6 mg g−1 Ova (13.6‐ASO‐MIMs) and bare glass, indicating the excellent biocompatibility of the 13.6‐ASO‐MIMs. Here, the results on largely enhanced adsorption capacity, perm‐selectivity (β values are more than 2.2), regeneration ability (still maintained 90% of the maximum adsorption capacity after 10 cycling operation), and high‐performance cell adhesion system (controlled by the binding amount of template protein) are shown, which clearly demonstrates the potential value of this method in smart biomaterials and biosensors. Multiple‐functional Ag/SiO2/organic based molecularly imprinted membranes (ASO‐MIMs) are prepared for high‐stability protein recognition and cell adhesion/detachment. Because of the high affinity of ASO‐MIMs (comparable to that of the natural receptor) and the innocuity to bioprotein (compared to covalent interactions), the approach reported is a promising candidate for large‐scale applications in protein recognition and cell‐based regenerative medicine.
      PubDate: 2015-08-13T13:35:11.436181-05:
      DOI: 10.1002/adfm.201502465
       
  • Unconventional Aluminum Ion Intercalation/Deintercalation for Fast
           Switching and Highly Stable Electrochromism
    • Authors: Yuyu Tian; Weikun Zhang, Shan Cong, Yuanchuan Zheng, Fengxia Geng, Zhigang Zhao
      Abstract: Electrochromic devices have many important commercial applications ranging from electronic paper like displays, antiglare rear‐view mirrors in cars, to energy‐saving smart windows in buildings. Monovalent ions such as H+, Li+, and Na+ are widely used as insertion ions in electrochromic devices but have serious limitations such as instability, high‐cost, and hard handling. The utilization of trivalent ions as insertion ions has been largely overlooked probably because of the strong electrostatic interactions between ions and intercalation framework and the resulted difficulties of intercalation. It is demonstrated that the trivalent ion, Al3+, can be used as efficient insertion ion by using metal oxide hosts in nanostructured form, which brings the desired fast‐switch, high‐contrast, and high‐stability as well to electrochromic devices. Differing from the usual structure degradation by repeated guest intercalation/deintercalation, the Al3+ insertion introduces strong electrostatic forces, which on some degree stabilize the crystal structure and consequently yield much enhanced performances. Using Al3+ as insertion ions in electrochromic applications allows for fast switching, high‐contrast, and highly stable electrochromic behavior. It also makes it possible to overcome the existing problems encountered by the conventional insertion ions. The new, low‐cost insertion ion is beneficial for the fabrication of more stable and economical electrochromic devices.
      PubDate: 2015-08-13T13:34:35.650671-05:
      DOI: 10.1002/adfm.201502638
       
  • Near‐Infrared Light‐Absorptive Stealth Liposomes for Localized
           Photothermal Ablation of Tumors Combined with Chemotherapy
    • Authors: Menghuan Li; Cathleen Teh, Chung Yen Ang, Si Yu Tan, Zhong Luo, Qiuyu Qu, Yuanyuan Zhang, Vladimir Korzh, Yanli Zhao
      Abstract: Although near‐infrared (NIR) light‐absorbing organic dyes have recently been proposed for photothermal ablation of tumors, their clinical applications have often been hampered by problems such as low water solubility and minimal tissue absorption. Rapid development of nanotechnology provides various novel nanostructures to address these issues. In this work, doxorubicin (DOX)‐loaded stealth liposomes are engineered through the incorporation of an NIR‐absorptive heptamethine indocyanine dye IR825 into the thermoresponsive liposomes for photothermal/chemo combined cancer therapy. It is demonstrated that the lipid nanostructure can enhance the bioavailability of water‐insoluble IR825 for efficient photothermal treatment, while delivering the anticancer drug doxorubicin to achieve simultaneous anticancer medication. The combined treatment of photothermal ablation and chemotherapy synergistically improves the overall cancer cell killing efficiency, which can be of future clinical interest. NIR light‐absorptive stealth liposomes are developed by incorporating an NIR‐absorptive heptamethine indocyanine dye IR825 into thermoresponsive liposomes, which can be further loaded with doxorubicin for photothermal/chemo combined cancer therapy in vivo.
      PubDate: 2015-08-12T23:07:24.292508-05:
      DOI: 10.1002/adfm.201502469
       
  • Chinese‐Noodle‐Inspired Muscle Myofiber Fabrication
    • Abstract: Much effort has been made to engineer artificial fiber‐shaped cellular constructs that can be potentially used as muscle fibers or blood vessels. However, existing microfiber‐based approaches for culturing cells are still limited to 2D systems, compatible with a restricted number of polymers (e.g., alginate) and always lacking in situ mechanical stimulation. Here, a simple, facile, and high‐throughput technique is reported to fabricate 3D cell‐laden hydrogel microfibers (named hydrogel noodles), inspired by the fabrication approach for Chinese Hele noodle. A magnetically actuated and noncontact method to apply tensile stretch on hydrogel noodles has also been developed. With this method, it is found that cellular strain‐threshold and saturation behaviors in hydrogel noodles differ substantially from their 2D analogs, including proliferation, spreading, and alignment. Moreover, it is shown that these cell‐laden microfibers can induce muscle myofiber formation by tensile stretching alone. This easily adaptable platform holds great potential for the creation of functional tissue constructs and probing mechanobiology in three dimensions. C2C12 muscle myofibers within hydrogel fibers are successfully generated using a simple, facile, and high‐throughput method that is inspired by the fabrication process of Chinese noodles. The effect of mechanical tensile strain on cell viability, spreading, and proliferation is also investigated. Such an approach holds potential to create functional tissue constructs and provides insight into the mechanobiological responses of cells in three dimensions.
      PubDate: 2015-08-12T05:41:54.134648-05:
      DOI: 10.1002/adfm.201502018
       
  • Quantifying the Energy Barriers and Elucidating the Charge Transport
           Mechanisms across Interspherulite Boundaries in Solution‐Processed
           Organic Semiconductor Thin Films
    • Abstract: Grain boundaries act as bottlenecks to charge transport in devices comprising polycrystalline organic active layers. To improve device performance, the nature and resulting impact of these boundaries must be better understood. The densities and energy levels of shallow traps within and across triethylsilylethynyl anthradithiophene (TES ADT) spherulites are quantified. The trap density is 7 × 1010 cm−2 in devices whose channels reside within a single spherulite and up to 3 × 1011 cm−2 for devices whose channels span a spherulite boundary. The activation energy for charge transport, EA, increases from 34 meV within a spherulite to 50–66 meV across a boundary, depending on the angle of molecular mismatch. Despite being molecular in nature, these EA’s are more akin to those found for charge transport in polymer semiconductors. Presumably, trapped TES ADT at the boundary can electrically connect neighboring spherulites, similar to polymer chains connecting crystallites in polymer semiconductor thin films. The impact of interspherulite boundaries (ISBs) on charge transport in organic semiconductor thin films is explored using gated four‐probe transistor measurements on triethylsilylethynyl anthradithiophene (TES ADT). Quantification of the densities and energy levels of shallow traps at these boundaries suggests TES ADT's ISBs to be akin to the connected boundaries between crystallites in polymer semiconductor thin films.
      PubDate: 2015-08-12T05:41:38.022259-05:
      DOI: 10.1002/adfm.201501666
       
  • Filling the Gaps between Graphene Oxide: A General Strategy toward
           Nanolayered Oxides
    • Authors: Yoshitaka Saito; Xi Luo, Chunsong Zhao, Wei Pan, Chengmeng Chen, Jianghong Gong, Hidetoshi Matsumoto, Jie Yao, Hui Wu
      Abstract: Despite extraordinary developments in the research of 2D inorganic nanomaterials, a scalable and generalized synthetic method toward 2D oxide materials that lack layered lattice structures is still challenging. Herein, an easy and versatile solution‐based route to synthesize oxides with layered nanostructures by combining sol–gel method with graphene oxide (GO) paper templates is reported. GO can stack together to form a paper‐like membrane, the gap between two GO layers provides ideal 2D space to template the growth of oxide nanolayers. By this simple strategy, the gaps are filled successfully with polycrystalline TiO2, ZnO, Fe2O3, and amorphous SiO2 nanolayers with thickness of 1–5 nm. Single or multilayers of the oxide‐based ceramic/glass nanolayers for applications in electronics, catalysts, energy storage, and gas separation can be expected; as an example, it is shown that layered Fe2O3 electrodes exhibit high performance for lithium‐ion battery due to enhanced electrical connections between the 2D nanolayers. Graphene oxide (GO) provides an ideal 2D space which offers opportunity to confine a chemical reaction. By combining GO gap and sol–gel synthesis, 2D oxide nanolayers are successfully synthesized for a variety of metal oxides that do not naturally have layer molecular architecture.
      PubDate: 2015-08-11T13:33:40.504397-05:
      DOI: 10.1002/adfm.201501358
       
  • Remote Steering of Self‐Propelling Microcircuits by Modulated
           Electric Field
    • Authors: Rachita Sharma; Orlin D. Velev
      Abstract: The principles and design of “active” self‐propelling particles that can convert energy, move directionally on their own, and perform a certain function is an emerging multidisciplinary research field, with high potential for future technologies. A simple and effective technique is presented for on‐demand steering of self‐propelling microdiodes that move electroosmotically on water surface, while supplied with energy by an external alternating (AC) field. It is demonstrated how one can control remotely the direction of diode locomotion by electronically modifying the applied AC signal. The swimming diodes change their direction of motion when a wave asymmetry (equivalent to a DC offset) is introduced into the signal. The data analysis shows that the ability to control and reverse the direction of motion is a result of the electrostatic torque between the asymmetrically polarized diodes and the ionic charges redistributed in the vessel. This novel principle of electrical signal‐coded steering of active functional devices, such as diodes and microcircuits, can find applications in motile sensors, MEMs, and microrobotics. The direction of self‐propulsion of diodes floating on water surface, powered by external alternating (AC) electric fields, can be controlled on‐demand by electronically modifying the symmetry of the applied AC waveform. Changes in the duty cycle of the signal inducing short‐lasting DC fields can be used to remotely reverse its direction of motion or make it move sideways.
      PubDate: 2015-08-11T13:33:30.21744-05:0
      DOI: 10.1002/adfm.201502129
       
  • Micro‐/Nanostructured Highly Crystalline Organic Semiconductor Films
           for Surface‐Enhanced Raman Spectroscopy Applications
    • Authors: Mehmet Yilmaz; Mehmet Ozdemir, Hakan Erdogan, Ugur Tamer, Unal Sen, Antonio Facchetti, Hakan Usta, Gokhan Demirel
      Abstract: The utilization of inorganic semiconductors for surface‐enhanced Raman spectroscopy (SERS) has attracted enormous interest. However, despite the technological relevance of organic semiconductors for enabling inexpensive, large‐area, and flexible devices via solution processing techniques, these π‐conjugated systems have never been investigated for SERS applications. Here for the first time, a simple and versatile approach is demonstrated for the fabrication of novel SERS platforms based on micro‐/nanostructured 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) thin films via an oblique‐angle vapor deposition. The morphology of C8‐BTBT thin films is manipulated by varying the deposition angle, thus achieving highly favorable 3D vertically aligned ribbon‐like micro‐/nanostructures for a 90° deposition angle. By combining C8‐BTBT semiconductor films with a nanoscopic thin Au layer, remarkable SERS responses are achieved in terms of enhancement (≈108), stability (>90 d), and reproducibility (RSD < 0.14), indicating the great promise of Au/C8‐BTBT films as SERS platforms. Our results demonstrate the first example of an organic semiconductor‐based SERS platform with excellent detection characteristics, indicating that π‐conjugated organic semiconductors have a great potential for SERS applications. A simple and versatile approach for the fabrication of novel surface‐enhanced Raman spectroscopy (SERS) platforms based on vertically oriented micro‐/nanostructured 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) films via an oblique‐angle vapor deposition is demonstrated. Remarkable SERS responses are achieved demonstrating the first example of a π‐conjugated small‐molecule based SERS platform with excellent detection characteristics. Our results indicate that organic semiconductors hold great promise for future SERS applications.
      PubDate: 2015-08-11T13:32:50.24377-05:0
      DOI: 10.1002/adfm.201502151
       
  • Solar Water Splitting by TiO2/CdS/Co–Pi Nanowire Array Photoanode
           Enhanced with Co–Pi as Hole Transfer Relay and CdS as Light Absorber
           
    • Authors: Guanjie Ai; Hongxing Li, Shaopei Liu, Rong Mo, Jianxin Zhong
      Abstract: The cobalt phosphate water oxidation catalyst (Co–Pi WOC) stabilized, CdS sensitized TiO2 nanowire arrays for nonsacrificial solar water splitting are reported. In this TiO2/CdS/Co–Pi photoanode, the Co–Pi WOC acts as hole transfer relay to accelerate the surface water oxidation reaction, CdS serves as light absorber for wider solar spectra harvesting, and TiO2 matrix provides direct pathway for electron transport. This triple TiO2/CdS/Co–Pi hybrid photoanode exhibits much enhanced photocurrent density and negatively shifts in onset potential, resulting in 1.5 and 3.4 times improved photoconversion efficiency compared to the TiO2/CdS and TiO2 photoanode, respectively. More importantly, the TiO2/CdS/Co–Pi shows significantly improved photoelectrochemical stability compared to the TiO2/CdS electrode, with ≈72% of the initial photocurrent retained after 2 h irradiation. The reason for the promoted performance is discussed in detail based on electrochemical measurements. This work provides a new paradigm for designing 1D nanoframework/light absorber/WOC photoanode to simultaneously enhance light absorption, charge separation, and transport and surface water oxidation reaction for efficient and stable solar fuel production. A smart hybridization paradigm is proposed by hierarchically assembling CdS shell and Co–Pi electrocatalyst on vertically aligned TiO2 nanowires, aiming to simultaneously enhance the light absorption, charge separation/transport, and surface water oxidation reaction for solar water splitting. The multifunctional heterostructure delivers superior photoelectrochemical conversion efficiency and stability in nonsacrificial electrolyte, thus casting new light on developing advanced photoelectrochemical cell.
      PubDate: 2015-08-11T13:32:41.783417-05:
      DOI: 10.1002/adfm.201502461
       
  • Metallic Glass as a Mechanical Material for Microscanners
    • Abstract: Microelectromechanical system (MEMS) actuators essentially have movable silicon structures where the mechanical motion can be activated electronically. The microscanner is one of the most successfully commercialized MEMS devices which are widely used for collecting optical information, manipulating light, and displaying images. While silicon is abundant, it is also brittle and stiff and when microprocessed, defects are not uncommon. These defects result in weakness under torsional stress and this has been the key factor limiting the scanning performance of the microscanner. Here a metallic glass (MG)‐based microscanner is reported with MG as the material for the moving torsion bars. The low elastic modulus, high fracture toughness, and high strength of MG offers, for the first time, an ultralarge rotating angle of 146° with power consumption lowered to the microwatt range, and a smaller driving force and better actuation performance, than conventional single crystal silicon and polycrystalline silicon. The high spatial resolution and large scanning field of the MG‐based microscanner are demonstrated in the tomographic imaging of a human finger. This development of an MG‐based MEMS possibly opens a new field of low‐powered MEMS devices with extreme actuation and enhanced sensing. A metallic glass‐based microscanner exhibits, for the first time, an ultralarge rotating angle of 146° with power consumption lowered to the microwatt range, as well as a smaller driving force and better actuation performance than conventional single crystal silicon and polycrystalline silicon. This development opens a new field of low‐powered microelectromechanical systems with extreme actuation and enhanced sensing.
      PubDate: 2015-08-10T02:52:07.273674-05:
      DOI: 10.1002/adfm.201502456
       
  • Metallic 1T‐WS2 for Selective Impedimetric Vapor Sensing
    • Abstract: Selective gas sensing is of immense importance for industrial as well as safety purposes. Here it is shown that metallic 1T phase transition metal dichalcogenides, such as tungsten sulfide (WS2), provide sensitive and selective platform for gas sensing. Using impedance spectroscopy distinguishable alterations can be detected on the impedance phase spectrum of interdigitated gold electrode modified with chemically exfoliated 1T‐WS2 caused by different vapors. In particular, it is found that the impedance phase spectra of 1T‐WS2 device present different resonant frequencies with maximum around 1 Hz in the presence of methanol vapor and around 1 kHz in the presence of water vapor. Such a well‐distinguished signal allows their selective detection also when they are present in a mixture. The impedance phase spectra allow the selective methanol and water vapor sensing with an impedimetric device based on 1T‐WS2. This system utilizing 1T phase of WS2 for selective gas sensing based on impedance spectroscopy opens new avenues for gas sensing and shall find wide spectra of applications. The impedance phase spectra of metallic 1T‐WS2 present specific resonant frequencies for methanol and water vapors, meaning that using the same 1T‐WS2 platform is possible to detect methanol and water vapors by selecting specific frequencies (1 Hz for methanol and 1 kHz for water).
      PubDate: 2015-08-10T02:52:00.816605-05:
      DOI: 10.1002/adfm.201502223
       
  • Linking Group Influences Charge Separation and Recombination in
           All‐Conjugated Block Copolymer Photovoltaics
    • Abstract: All‐conjugated block copolymers bring together hole‐ and electron‐conductive polymers and can be used as the active layer of solution‐processed photovoltaic devices, but it remains unclear how molecular structure, morphology, and electronic properties influence performance. Here, the role of the chemical linker is investigated through analysis of two donor–linker–acceptor block copolymers that differ in the chemistry of the linking group. Device studies show that power conversion efficiencies differ by a factor of 40 between the two polymers, and ultrafast transient absorption measurements reveal charge separation only in block copolymers that contain a wide bandgap monomer at the donor–acceptor interface. Optical measurements reveal the formation of a low‐energy excited state when donor and acceptor blocks are directly linked without this wide bandgap monomer. For both samples studied, it is found that the rate of charge recombination in these systems is faster than in poly­mer–polymer and polymer–fullerene blends. This work demonstrates that the linking group chemistry influences charge separation in all‐conjugated block copolymer systems, and further improvement of photovoltaic performance may be possible through optimization of the linking group. These results also suggest that all‐conjugated block copolymers can be used as model systems for the donor–acceptor interface in bulk heterojunction blends. All‐conjugated block copolymers have significant potential for use in photovoltaic active layers, but the role of the linking group between donor and acceptor blocks is poorly understood. An analysis of linking group chemistry is presented, revealing that proper design of the linking group is essential for producing viable block copolymer photovoltaic devices.
      PubDate: 2015-08-10T02:51:16.498944-05:
      DOI: 10.1002/adfm.201502623
       
  • Triphenylphosphonium‐Conjugated
           Poly(ε‐caprolactone)‐Based Self‐Assembled
           Nanostructures as Nanosized Drugs and Drug Delivery Carriers for
           Mitochondria‐Targeting Synergistic Anticancer Drug Delivery
    • Authors: Dong Youl Cho; Hana Cho, Kiyoon Kwon, Minjong Yu, Eunji Lee, Kang Moo Huh, Don Haeng Lee, Han Chang Kang
      Abstract: For mitochondria‐targeting delivery, a coupling reaction between poly(ε‐caprolactone) diol (PCL diol) and 4‐carboxybutyltriphenylphosphonium (4‐carboxybutyl TPP) results in the synthesis of amphiphilic TPP‐PCL‐TPP (TPCL) polymers with a bola‐like structure. In aqueous environments, the TPCL polymer self‐assembled via cosolvent dispersion and film hydration, resulting in the formation of cationic nanoparticles (NPs) less than 50 nm in size with zeta‐potentials of approximately 40 mV. Interestingly, different preparation methods for TPCL NPs result in various morphologies such as nanovesicles, nanofibers, and nanosheets. In vitro cytotoxicity results with TPCL NPs indicate IC50 values of approximately 10–60 μg mL−1, suggesting their potential as anticancer nanodrugs. TPCL NPs can be loaded both with hydrophobic doxorubicin (Dox) and its hydrophilic salt form (Dox·HCl), and their drug loading contents are approximately 2–10 wt% depending on the loading method and the hydrophilicity/hydrophobicity of the drugs. Although Dox·HCl exhibits more cellular and nuclear uptake, resulting in greater antitumor effects than Dox, most drug‐loaded TPCL NPs exhibit higher mitochondrial uptake and approximately 2–7‐fold higher mitochondria‐to‐nucleus preference than free drugs, resulting in superior (approximately 7.5–18‐fold) tumor‐killing activity for most drug‐loaded TPCL NPs compared with free drugs. In conclusion, TPCL‐based nanoparticles have potential both as antitumor nanodrugs themselves and as nanocarriers for chemical therapeutics. Amphiphilic triphenyphosphonium (TPP)‐poly(ε‐caprolactone)(PCL)‐TPP (TPP‐PCL‐TPP, TPCL) polymers are synthesized and self‐assembled to form nanovesicles and nanofibers. TPCL nanoparticles (NPs) themselves exhibit cancer‐killing properties, and can carry either hydrophilic drugs or hydrophobic drugs. Anticancer drug‐loaded TPCL NPs show synergistically strong anticancer effects via a combination of the loaded chemical drugs and TPCL‐based NPs.
      PubDate: 2015-08-06T08:38:10.511183-05:
      DOI: 10.1002/adfm.201501422
       
  • m‐Indolocarbazole Derivative as a Universal Host Material for RGB
           and White Phosphorescent OLEDs
    • Abstract: The host materials designed for highly efficient white phosphorescent organic light‐emitting diodes (PhOLEDs) with power efficiency (PE) >50 lm W‐1 and low efficiency roll‐off are very rare. In this work, three new indolocarbazole‐based materials (ICDP, 4ICPPy, and 4ICDPy) are presented composed of 6,7‐dimethylindolo[3,2‐a]carbazole and phenyl or 4‐pyridyl group for hosting blue, green, and red phosphors. Among this three host materials, 4ICDPy‐based devices reveal the best electroluminescent performance with maximum external quantum efficiencies (EQEs) of 22.1%, 27.0%, and 25.3% for blue (FIrpic), green (fac‐Ir(ppy)3), and red ((piq)2Ir(acac)) PhOLEDs. A two‐color and single‐emitting‐layer white organic light‐emitting diode hosted by 4ICDPy with FIrpic and Ir(pq)3 as dopants achieves high EQE of 20.3% and PE of 50.9 lm W−1 with good color stability; this performance is among the best for a single‐emitting‐layer white PhOLEDs. All 4ICDPy‐based devices show low efficiency roll‐off probably due to the excellent balanced carrier transport arisen from the bipolar character of 4ICDPy. Three new indolocarbazole‐based host materials ICDP, 4ICPPy, and 4ICDPy are synthesized and used as hosts for various color phosphorescent organic light‐­emitting diodes. The blue, green, and red devices using 4ICDPy as host all exhibit very high device efficiencies. In addition, a two‐color white device shows an external quantum efficiency of 20.3% and power efficiency of 50.9 lm W−1 with excellent color stability.
      PubDate: 2015-08-06T08:37:35.790692-05:
      DOI: 10.1002/adfm.201502079
       
  • Structural Origins for Tunable Open‐Circuit Voltage in
           Ternary‐Blend Organic Solar Cells
    • Abstract: Ternary‐blend bulk‐heterojunction solar cells have provided a unique opportunity for tuning the open‐circuit voltage (Voc) as the “effective” highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO) energy levels shift with active‐layer composition. Grazing‐incidence X‐ray diffraction (GIXD) measurements performed on such ternary‐blend thin films reveal evidence that the two polymer donors interact intimately; their ionization potentials are thus reflections of the blend compositions. In ternary‐blend thin films in which the two polymer donors do not interact physically, the polymer donors each retain their molecular electronic character; solar cells constructed with these ternary blends thus exhibit Vocs that are pinned to the energy level difference between the highest of the two lying HOMO and the LUMO of the electron acceptor. These observations are consistent with the organic alloy model proposed earlier. Quantification of the square of the square‐root differences of the surface energies of the components provides a proxy for the Flory–Huggins interaction parameter for polymer donor pairs in these ternary‐blend systems. Of the three ternary‐blend systems examined herein, this quantity has to be below 0.094 in order for ternary‐blend solar cells to exhibit tunable Voc. The first direct structural study of ternary‐blend bulk heterojunction active layers in solar cells that demonstrate tunable open‐circuit voltage (Voc) is performed. Physical mixing of the polymer donors—quantified by the square of the square‐root difference in surface energies—leads to ensemble‐average electronic character that results in composition‐dependent Voc when these blends are incorporated in solar cells.
      PubDate: 2015-08-06T08:37:10.980695-05:
      DOI: 10.1002/adfm.201502287
       
  • Significant Enhancement of Triboelectric Charge Density by Fluorinated
           Surface Modification in Nanoscale for Converting Mechanical Energy
    • Authors: Hua Yang Li; Li Su, Shuang Yang Kuang, Cao Feng Pan, Guang Zhu, Zhong Lin Wang
      Abstract: Excellent triboelectric and mechanical properties are achieved on the same material for the first time by developing an effective, general, straightforward, and area‐scalable approach to surface modification of a polyethylene terephthalate (PET) film via inductive‐coupled plasma etching. The modification enables gigantic enhancement of triboelectric charge density on the PET surface. Based on the modified PET as a contact material, a triboelectric nanogenerator (TENG) exhibits significantly promoted electric output compared to the one without the modification. The obtained electric output is even superior to a TENG made of conventional polytetrafluoroethylene that is known for its strongest ability of being charged by triboelectrification among all engineering plastics. Detailed characterizations reveal that the enhancement of triboelectric charge density on the PET is attributed to both chemical modification of fluorination and physical modification of roughened morphology in nanoscale. Therefore, this work proposes a new route to obtaining high‐performance TENGs by manipulating and modifying surface properties of materials. An effective, general, straightforward, and area‐scalable approach to surface modification of a polyethylene terephthalate (PET) film is developed via inductive‐coupled plasma etching. The modification significantly promotes triboelectric property of the PET, making it a superior material for fabricating high‐performance triboelectric nanogenerators. Chemical fluorination and physical bombardment both play vitally important roles in the modification.
      PubDate: 2015-08-06T08:37:07.367078-05:
      DOI: 10.1002/adfm.201502318
       
  • Etching‐Free Epitaxial Growth of Gold on Silver Nanostructures for
           High Chemical Stability and Plasmonic Activity
    • Authors: Hongpo Liu; Tingzhuo Liu, Lei Zhang, Lu Han, Chuanbo Gao, Yadong Yin
      Abstract: A robust method for epitaxial deposition of Au onto the surface of Ag nanostructures is demonstrated, which allows effective conversion of Ag nano­structures of various morphologies into Ag@Au counterparts, with the anisotropic ones showing excellent plasmonic properties comparable to the original Ag nanostructures while significantly enhanced stability. Sulfite plays a determining role in the success of this epitaxial deposition as it strongly complexes with gold cations to completely prevent galvanic replacement while it also remains benign to the Ag surface to avoid any ligand‐assisted oxidative etching. By using Ag nanoplates as an example, it is shown that the corresponding Ag@Au nanoplates possess remarkable plasmonic properties that are virtually Ag‐like, in clear contrast to Ag@Au nanospheres that exhibit much lower plasmonic activities than their Ag counterparts. As a result, they display high durability and activities in surface‐enhanced Raman scattering applications. This strategy may represent a general platform for depositing a noble metal on less stable metal nanostructures, thus opening up new opportunities in rational design of functional metal nanomaterials for a broad range of applications. Ag@Au core/shell nanostructures are synthesized by epitaxial growth of Au on Ag nanostructures, with the anisotropic ones such as nanoplates showing Ag‐like plasmonic properties and high stability. Sulfite plays a critical role in preventing galvanic replacement and oxidative etching of the Ag nanostructures. The resulting nanocrystals may find broad use in many plasmon‐based applications for superior activities and durability.
      PubDate: 2015-08-06T08:37:01.70744-05:0
      DOI: 10.1002/adfm.201502366
       
  • Copper(I) Iodide as Hole‐Conductor in Planar Perovskite Solar Cells:
           Probing the Origin of J–V Hysteresis
    • Abstract: Organic–inorganic lead halide perovskite solar cells are promising alternatives to silicon‐based cells due to their low material costs and high photovoltaic performance. In this work, thin continuous perovskite films are combined with copper(I) iodide (CuI) as inorganic hole‐conducting material to form a planar device architecture. A maximum conversion efficiency of 7.5% with an average efficiency of 5.8 ± 0.8% is achieved which, to our knowledge, is the highest reported efficiency for CuI‐based devices with a planar structure. In contrast to related planar 2,2′,7,7′‐tetrakis‐(N,N ‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene (spiro‐OMeTAD)‐based devices, the CuI‐based devices do not show a pronounced hysteresis when tested by scanning the potential in a forward and backward direction. The strong quenching of photoluminescence (PL) signal and comparatively fast decay of open‐circuit voltage demonstrates a more rapid removal of positive charge carriers from the perovskite layer when in contact with CuI compared to spiro‐OMeTAD. A slow response on a timescale of 10–100 s is observed for the spiro‐OMeTAD‐based devices. In comparison, the CuI‐based device displays a significantly faster response as determined through electrochemical impedance spectroscopy (EIS) and open‐circuit voltage decays (OCVDs). The characteristically slow kinetics measured through EIS and OCVD are linked directly to the current–voltage hysteresis. Planar perovskite/copper(I) iodide solar cells with near to no J–V hysteresis, made by employing thin CuI and perovskite layers, result in a record conversion efficiency of 7.5%. The magnitude of dielectric polarization at the perovskite/hole‐conductor interface is proposed to influence the degree of J–V hysteresis.
      PubDate: 2015-08-06T08:36:15.25885-05:0
      DOI: 10.1002/adfm.201502541
       
  • Oxygen Diffusion in SrTiO3 and Related Perovskite Oxides
    • Authors: R. A. De Souza
      Abstract: The transport of oxygen ions plays a central role in determining the performance or the degradation of perovskite‐type oxides in applications as diverse as ceramic capacitors, solid electrolytes, memristive devices and all‐oxide electronics. In this Feature Article, experimental data reported in the literature for oxygen diffusion in SrTiO3 and in related titanate, zirconate and cerate perovskite oxides [CaTiO3, BaTiO3, (Na,Bi)TiO3, Pb(Ti,Zr)O3, CaZrO3, SrZrO3, BaZrO3, SrCeO3, BaCeO3] are reviewed. The two related aims are to draw attention to discrepancies and to identify reliable diffusion data. The physical limit to the diffusivity of oxygen vacancies in a perovskite oxide is also considered. Methods of studying diffusion in oxides are reviewed. Oxygen diffusion coefficients extracted from the literature for SrTiO3 and related titanate, zirconate and cerate perovskites are compared.
      PubDate: 2015-08-06T07:04:49.37961-05:0
      DOI: 10.1002/adfm.201500827
       
  • Rational Construction of a Functionalized V2O5 Nanosphere/MWCNT
           Layer‐by‐Layer Nanoarchitecture as Cathode for Enhanced
           Performance of Lithium‐Ion Batteries
    • Authors: Bin Sun; Kai Huang, Xiang Qi, Xiaolin Wei, Jianxin Zhong
      Abstract: Vanadium pentoxide (V2O5) has received considerable attention owing to its potential application in energy storage with high specific capacity (294 mAh g−1). However, the development of V2O5 cathodes has been limited by the intrinsically low electrical conductivity and slow electrochemical kinetics resulting in a significant capacity decay. In this article, in order to overcome the issues, V2O5 nanospheres and multiwalled carbon nanotubes (MWCNTs) are used to fabricate layer‐by‐layer composited paper as the cathode, which is prepared via electrostatic interaction and vacuum filtration by alternating the positively charged V2O5 nanospheres and the negatively charged terminated MWCNT solutions. As a result, the V2O5 nanospheres are closely intercalated between the adjacent MWCNT layers leading to minimize the disadvantage voids and enhance the overall conductivity of the composited electrode, which exhibits an enhanced cycling durability as well as improved rate capability. A layer‐by‐layer nanoarchitecture as cathode is successfully fabricated, assembled by alternating the positively charged V2O5 nanospheres and the negatively charged terminated multiwalled carbon nanotube (MWCNT) solutions. The V2O5 nanospheres are closely intercalated between the adjacent MWCNT layers, minimizing disadvantagageous voids and improving overall conductivity, leading to an enhanced cycling durability as well as improved rate capability.
      PubDate: 2015-08-04T06:30:25.456029-05:
      DOI: 10.1002/adfm.201502382
       
  • Organic Tribotronic Transistor for
           Contact‐Electrification‐Gated Light‐Emitting Diode
    • Authors: Chi Zhang; Jing Li, Chang Bao Han, Li Min Zhang, Xiang Yu Chen, Li Duo Wang, Gui Fang Dong, Zhong Lin Wang
      Abstract: Tribotronics is a new field about the devices fabricated using the electrostatic potential created by contact electrification as a “gate” voltage to tune/control charge carrier transport in semiconductors. In this paper, an organic tribotronic transistor is proposed by coupling an organic thin film transistor (OTFT) and a triboelectric nanogenerator (TENG) in vertical contact‐separation mode. Instead of using the traditional gate voltage for controlling, the charge carrier transportation in the OTFT can be modulated by the contact‐induced electrostatic potential of the TENG. By further coupling with an organic light‐emitting diode, a contact‐electrification‐gated light‐emitting diode (CG‐LED) is fabricated, in which the operating current and light‐emission intensity can be tuned/controlled by an external force–induced contact electrification. Two different modes of the CG‐LED have been demonstrated and the brightness can be decreased and increased by the applied physical contact, respectively. Different from the conventional organic light‐emitting transistor controlled by an electrical signal, the CG‐LED has realized the direct interaction between the external environment/stimuli and the electroluminescence device. By introducing optoelectronics into tribotronics, the CG‐LED has open up a new field of tribophototronics with many potential applications in interactive display, mechanical imaging, micro‐opto‐electro‐mechanical systems, and flexible/touch optoelectronics. An organic tribotronic transistor and a contact‐electrification‐gated light‐emitting diode (CG‐LED) are proposed, in which the operating current and light‐emission intensity can be tuned/controlled by an external force‐induced contact electrification. Different from the conventional organic light‐emitting transistor controlled by an electrical signal, the CG‐LED can realize the direct interaction between the external environment/stimuli and the electroluminescence device.
      PubDate: 2015-08-04T06:30:18.849339-05:
      DOI: 10.1002/adfm.201502450
       
  • Probing Molecular and Crystalline Orientation in Solution‐Processed
           Perovskite Solar Cells
    • Abstract: The microstructure of solution‐processed organometallic lead halide perovskite thin films prepared by the “gas‐assisted” method is investigated with synchrotron‐based techniques. Using a combination of GIWAXS and NEXAFS spectroscopy the orientational alignment of CH3NH3PbI3 crystallites and CH3NH3+ cations are separately probed. The GIWAXS results reveal a lack of preferential orientation of CH3NH3PbI3 crystallites in 200–250 nm thick films prepared on both planar TiO2 and mesoporous TiO2. Relatively high efficiencies are observed for device based on such films, with 14.3% achieved for planar devices and 12% for mesoporous devices suggesting that highly oriented crystallites are not crucial for good cell performance. Oriented crystallites however are observed in thinner films (≈60 nm) deposited on planar TiO2 (but not on mesoporous TiO2) indicating that the formation of oriented crystallites is sensitive to the kinetics of solvent evaporation and the underlying TiO2 morphology. NEXAFS measurements on all samples found that CH3NH3+ cations exhibit a random molecular orientation with respect to the substrate. The lack of any NEXAFS dichroism for the thin CH3NH3PbI3 layer deposited on planar TiO2 in particular indicates the absence of any preferential orientation of CH3NH3+ cations within the CH3NH3PbI3 unit cell for as‐prepared layers, that is, without any electrical poling. Using a combination of GIWAXS and NEXAFS spectroscopy, the orientational alignment of CH3NH3PbI3 crystallites and CH3NH3+ cations are separately probed. The orientation of CH3NH3PbI3 crystallites is sensitive to film thickness, solvent evaporation rate, and the underlying TiO2 morphology. However, CH3NH3+ cations exhibit a random molecular orientation independent of the TiO2 architecture and the perovskite film thickness.
      PubDate: 2015-08-04T06:29:59.936017-05:
      DOI: 10.1002/adfm.201502553
       
  • Stretchable Chemical Patterns for the Assembly and Manipulation of Arrays
           of Microdroplets with Lensing and Micromixing Functionality
    • Authors: John J. Bowen; Jay M. Taylor, Christopher P. Jurich, Stephen A. Morin
      Abstract: The chemical properties of a surface are readily controlled using a layer (or layers) of surface‐functional groups that can be generated with, for example, self‐assembled monolayers (SAMs) or polymer brushes. These methods have enabled rational control over surface chemistry, which directly impacts surface properties, such as wettability, but generally follow a serial approach to building up surface‐functional groups (i.e., separate chemical steps are needed for the initial and each subsequent surface modification). This paper describes systems based on soft materials—stretchable chemical patterns—that have surface properties that are easily and reversibly modified using mechanical deformations. These systems couple surface‐chemical features such as the density and arrangement of functional groups on elastomeric polymers (e.g., polydimethylsiloxane) to mechanically induced surface deformations. This approach enables rapid and reversible control of surface chemistry and thus surface properties and processes. The behavior of these systems is characterized using fluorescent molecules and their utility illustrated through the organization and manipulation of arrays of micrometer‐scale droplets, which have optical and small‐volume mixing functionalities applicable to microlens and microreactor technologies, respectively. The capabilities of these systems may be extended to, for example, the control of heterogeneous nucleation, surface reactivity, and micro/nanoscale assembly. Chemically patterned silicone films drive the assembly of microdroplets into ordered arrays. These microdroplets can be “stretched”—a capability that was used to drive mixing in the droplets and to change the lensing characteristics of the array. Synthesizing “stretchable” chemical patterns of different geometries and functional groups provides a method to explore soft, mechanoresponsive surfaces with rapidly reversible properties unavailable in hard systems.
      PubDate: 2015-08-04T06:02:22.858767-05:
      DOI: 10.1002/adfm.201502174
       
  • Functional Organic Semiconductors Assembled via Natural Aggregating
           Peptides
    • Abstract: Specific peptide sequences designed by inspection of protein–protein interfaces have been identified and used as tectons in hybrid functional materials. Here, an 8‐mer peptide derived from an interface of the peroxiredoxin family of self‐assembling proteins is exploited to encode the assembly of the perylene imide‐based organic semiconductor building blocks. By augmenting the peptide with additional functionality to trigger aggregation and manipulate the directionality of peptide‐semiconductor coupling, a series of hybrid materials based on the natural peptide interface is presented. Using spectroscopic probes, the mode of self‐assembly and the electronic coupling between neighboring perylene units is shown to be strongly affected by the number of peptides attached, and by their backbone directionality. The disubstituted material with peptides extending in the N to C direction away from the perylene core exhibits strong coupling and long‐range order, both attractive properties for electronic device applications. A bio‐organic field‐effect transistor is fabricated using this material, highlighting the possibilities of exploiting natural peptide tectons to encode self‐assembly in other functional materials and devices. Natural aggregating peptide sequences are used as tectons to assemble organic semiconducting molecules. An 8‐mer peptide derived from inspection of protein–protein interfaces in the peroxiredoxin family is attached in various modes to perylene imides. Self‐assembling hybrid materials with strong electronic coupling and long‐range order are created, culminating with the fabrication of a bio‐organic field‐effect transistor device.
      PubDate: 2015-08-04T06:02:06.376304-05:
      DOI: 10.1002/adfm.201502255
       
  • Perfluorinated Ionomer‐Modified Hole‐Injection Layers:
           Ultrahigh‐Workfunction but Nonohmic Contacts
    • Abstract: Recently it has been reported that Nafion oligomers, i.e., 2‐(2‐sulfonatotetrafluoroethoxy)‐2‐trifluoromethyltrifluoroethoxyfunctionalized oligotetrafluoroethylenes, also called perfluorinated ionomers (PFIs), can be blended into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDT:PSSH) films to increase their workfunctions beyond 5.2 eV. These PFI‐modified films are useful for energy‐level alignment studies, and have been proposed as hole‐injection layers (HILs). It is shown here however that these HILs do not provide sufficiently fast hole transfer into adjacent polymer semiconductor layers with ionization potentials deeper than ≈5.2 eV. X‐ray and ultraviolet photoemission spectroscopies reveal that these HILs exhibit a molecularly‐thin PFI overlayer that sets up a surface dipole that provides the ultrahigh workfunction. This dipolar layer persists even when the subsequent organic semiconductor layer is deposited, as evidenced by measurements of the diode built‐in potentials. As a consequence, the PFI‐modified HILs produce a higher contact resistance, and a lower equilibrium density of holes at the semiconductor contact than might have been expected from simple thermodynamic considerations of the reduction in hole‐injection barrier. Thus the use of insulating dipolar surface layers at the charge‐injection contact to tune its workfunction to match the relevant transport level of the semiconductor is of limited utility to achieve ohmic contact in these devices. The ultrahigh workfunctions of PEDT:PSSH:PFI blends result from a dipolar surface layer associated with surface segregation of PFI chains. Despite their higher workfunctions, their hole contacts to organic semiconductors with ionization potentials deeper than 5.2 eV remain nonohmic. Workfunction matching through the use of an insulating dipolar layer is not efficient for providing ohmic contacts.
      PubDate: 2015-08-04T06:01:56.190455-05:
      DOI: 10.1002/adfm.201500784
       
  • Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in
           an Orthogonal Pentacene Dimer
    • Authors: Steven Lukman; Andrew J. Musser, Kai Chen, Stavros Athanasopoulos, Chaw K. Yong, Zebing Zeng, Qun Ye, Chunyan Chi, Justin M. Hodgkiss, Jishan Wu, Richard H. Friend, Neil C. Greenham
      Abstract: Fast and highly efficient intramolecular singlet exciton fission in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units is reported. Fission to triplet excitons from this ground state geometry occurs within 1 ps in isolated molecules in solution and dispersed solid matrices. The process exhibits a sensitivity to environmental polarity and competes with geometric relaxation in the singlet state, while subsequent triplet decay is strongly dependent on conformational freedom. The near orthogonal arrangement of the pentacene units is unlike any structure currently proposed for efficient singlet exciton fission and may lead to new molecular design rules. An orthogonal covalently bonded pentacene dimer (DP‐Mes) shows nearly quantitative singlet exciton fission in sub‐ps within the nuclear relxation time scale. By applying geometrical constraints, the fate of triplet–triplet annihilation is altered. These properties closely depend on molecular geometry and suggest a role for nuclear relaxation in controlling singlet exciton fission and triplet–triplet annihilation.
      PubDate: 2015-08-04T06:01:52.240741-05:
      DOI: 10.1002/adfm.201501537
       
  • Fully Printed Foldable Integrated Logic Gates with Tunable Performance
           Using Semiconducting Carbon Nanotubes
    • Authors: Le Cai; Suoming Zhang, Jinshui Miao, Zhibin Yu, Chuan Wang
      Abstract: The realization of large‐area and low‐cost flexible macroelectronics relies on both the advancements in materials science and the innovations in manufacturing techniques. In this study, extremely bendable and foldable carbon nanotube thin film transistors and integrated logic gates are fabricated on a piece of ultrathin polyimide substrate through an ink‐jet‐like printing process. The adoption of a hybrid gate dielectric layer consisting of barium titanate nanoparticles and poly(methyl methacrylate) has led to not only excellent gating effect but also superior mechanical compliance. The device characteristics show negligible amount of change after up to 1000 cycles of bending tests with curvature radii down to 1 mm, as well as very aggressive folding tests. Additionally, the electrical characteristics of each integrated logic gate can be tuned and optimized individually by using different numbers of carbon nanotube printing passes for different devices, manifesting the unique adaptability of ink‐jet printing as a digital, additive, and maskless method. This report on fully printed and foldable integrated logic gates represents an inspiring advancement toward the practical applications of carbon nanotubes for high‐performance and low‐cost ubiquitous flexible electronics. Carbon nanotube thin film transistors and integrated logic gates with tunable performance are fabricated on an ultrathin polyimide substrate by an inkjet‐like printing process. Thanks to the excellent flexibility of the hybrid dielectric layer, the devices can survive thousands of bending cycles with curvature radii down to 1 mm and very aggressive folding tests.
      PubDate: 2015-08-04T06:00:52.578049-05:
      DOI: 10.1002/adfm.201502367
       
  • Protein Fragment Reconstitution as a Driving Force for
           Self‐Assembling Reversible Protein Hydrogels
    • Authors: Na Kong; Hongbin Li
      Abstract: Due to their potential biomedical applications, protein‐based hydrogels have attracted considerable interest. Although various methods have been developed to engineer self‐assembling, physically‐crosslinked protein hydrogels, exploring novel driving forces to engineer such hydrogels remains challenging. Protein fragment reconstitution, also known as fragment complementation, is a self‐assembling mechanism by which protein fragments can reconstitute the folded conformation of the native protein when split into two halves. Although it has been used in biophysical studies and bioassays, fragment reconstitution has not been explored for hydrogel construction. Using a small protein GL5 as a model, which is capable of fragment reconstitution to reconstitute the folded GL5 spontaneously when split into two halves, GN and GC, we demonstrate that protein fragment reconstitution is a novel driving force for engineering self‐assembling reversible protein hydrogels. Fragment reconstitution between GN and GC crosslinks GN and GC‐containing proteins into self‐assembling reversible protein hydrogels. These novel hydrogels show temperature‐dependent reversible sol‐gel transition, and excellent property against erosion in water. Since many proteins can undergo fragment reconstitution, we anticipate that such fragment reconstitution may offer a general driving force for engineering protein hydrogels from a variety of proteins, and thus significantly expanding the ‘toolbox’ currently available in the field of biomaterials. Reversible self‐assembling protein hydrogels from protein fragment reconstitution: using protein fragment reconstitution as a novel driving force for crosslinking, reversible self‐assembling protein hydrogels are engineered. These novel protein hydrogels are responsive to temperature and exhibit superb stability against erosion in excess buffer.
      PubDate: 2015-08-04T05:59:40.112433-05:
      DOI: 10.1002/adfm.201502277
       
  • Large‐Area, Periodic, Hexagonal Wrinkles on Nanocrystalline
           Graphitic Film
    • Authors: Yanpeng Liu; Kenry, Yufeng Guo, Surabhi Sonam, Seul Ki Hong, Mui Hoon Nai, Chang Tai Nai, Libo Gao, Jianyi Chen, Byung Jin Cho, Chwee Teck Lim, Wanlin Guo, Kian Ping Loh
      Abstract: Sinusoidal wrinkles develop in compressively stressed film as a means to release stored elastic energy. Here, a simple way to fabricate large‐area, periodic, hexagonal wrinkled pattern on nanocrystalline graphitic films grown on c‐plane sapphire (
      PubDate: 2015-08-03T06:35:07.050912-05:
      DOI: 10.1002/adfm.201502010
       
  • Thin‐Sheet Carbon Nanomesh with an Excellent Electrocapacitive
           Performance
    • Authors: Huanjing Wang; Lei Zhi, Kaiqiang Liu, Liqin Dang, Zonghuai Liu, Zhibin Lei, Chang Yu, Jieshan Qiu
      Abstract: A facile yet effective chemical vapor deposition (CVD) method to prepare carbon nanomesh (CNM) with MgAl‐layered double oxides (LDO) as sacrificial template and ferrocene as carbon precursor is reported. Due to the combined effect of the LDO template and organometallic precursor, the as‐made hexagonal thin‐sheet CNM features a hierarchical pore system consisting of micropores and small mesopores with a size range of 1–6 nm, and a great number of random large mesopores with a pore size of 10–50 nm. The density, geometry, and size of the pores are strongly dependent on the CVD time and the annealing conditions. As supercapacitor electrode, the CNM exhibits an enhanced capacitance, high rate capability, and outstanding cycling performance with a much‐shortened time constant. The excellent capacitive performance is due to the presence of the large mesopores in the 2D CNM, which not only offer additional ion channels to accelerate the diffusion rate across the thin sheets but also help to make efficient use of the oxygen functional groups at the edges of large mesopores to increase the pseudocapacitance contribution. Growth of thin‐sheet carbon nanomesh (CNM) on MgAl‐layered double oxides, with controllable in‐plane pore structure, is reported. The large mesopores with pore size varying from 10 to 50 nm offer additional ion channels that greatly promote ion kinetics across the 2D CNM plane, leading to an improved capacitive performance with much shortened relaxation time constant.
      PubDate: 2015-08-03T06:34:49.689432-05:
      DOI: 10.1002/adfm.201502025
       
  • Large Upconversion Enhancement in the “Islands” Au–Ag
           Alloy/NaYF4: Yb3+, Tm3+/Er3+ Composite Films, and Fingerprint
           Identification
    • Abstract: The surface plasmon (SP) modulation is a promised way to highly improve the strength of upconversion luminescence (UCL) and expand its applications. In this work, the “islands” Au–Ag alloy film is prepared by an organic removal template method and explored to improve the UCL of NaYF4: Yb3+, Tm3+/Er3+. After the optimization of Au–Ag molar ratio (Au1.25–Ag0.625) and the size of NaYF4 nanoparticles (NPs, ≈7 nm), an optimum enhancement as high as 180 folds is obtained (by reflection measurement) for the overall UCL intensity of Tm3+. Systematic studies indicate that the UCL enhancement factor (EF) increases with the increased size of metal NPs and the increase of diffuse reflection, with the decreased size of NaYF4 NPs, with the decreased power density of excitation light and with improving order of multiphoton populating. The total decay rate varies only ranging of about 20% while EF changes significantly. All the facts above indicate that the UCL enhancement mainly originates from coupling of SP with the excitation electromagnetic field. Furthermore, the fingerprint identification based on SP‐enhanced UCL is realized in the metal/UC system, which provides a novel insight for the application of the metal/UC device. The “islands” Au–Ag/NaYF4: Yb3+, Tm3+ composite film is prepared by an organic self‐assembly and removal template method. The Au–Ag alloy not only has the stable and repeatable properties but exhibits super‐broad surface plasmon resonance band extending to 1100 nm, and obtained ≈180‐fold enhancement of upconversion luminescence for fingerprint identification.
      PubDate: 2015-08-03T06:34:39.400764-05:
      DOI: 10.1002/adfm.201502419
       
  • Transient Electronics: Wireless Microfluidic Systems for Programmed,
           Functional Transformation of Transient Electronic Devices (Adv. Funct.
           Mater. 32/2015)
    • Pages: 5077 - 5077
      Abstract: The functions and characteristics of electronic devices are modified on‐demand by wirelessly triggered etching via the use of wireless microfluidic devices. J. A. Rogers and co‐workers show, on page 5100, that functional transformations of target constituent components are achieved by dissolving the strategy point of circuit with etching solution injected through microfluidic channels on demand.
      PubDate: 2015-08-25T04:04:34.602552-05:
      DOI: 10.1002/adfm.201570214
       
  • Biomimetic Sensors: Vectorially Imprinted Hybrid Nanofilm for
           Acetylcholinesterase Recognition (Adv. Funct. Mater. 32/2015)
    • Pages: 5078 - 5078
      Abstract: On page 5178, R. E. Gyurcsányi, F. W. Scheller, and co‐workers demonstrate specific recognition of acetylcholinesterase, a potential marker of Alzheimer's disease, by a hybrid material which shows threefold selectivity gain by the “shape‐specific” electrosynthesized molecularly imprinted polymer, oriented binding to the propidium layer and signal generation exclusively by the enzyme bound to the nanofilm. Acetylcholinesterase is detected in the nanomolar range, whilst interfering proteins are effectively suppressed.
      PubDate: 2015-08-25T04:04:31.698575-05:
      DOI: 10.1002/adfm.201570215
       
  • Contents: (Adv. Funct. Mater. 32/2015)
    • Pages: 5079 - 5085
      PubDate: 2015-08-25T04:04:37.725806-05:
      DOI: 10.1002/adfm.201570216
       
  • Two‐Dimensional Transition Metal Dichalcogenides in Biosystems
    • Pages: 5086 - 5099
      Abstract: The intriguing properties of two‐dimensional transition metal dichalcogenides (2D TMDCs) have led to a significant body of fundamental research and rapid uptake of these materials in many applications. Specifically, 2D TMDCs have shown great potential in biological systems due to their tunable electronic characteristics, unique optical properties, stability in aqueous environments, large surface area that can be manipulated and functionalized as well as an intercalatable layered structure, and low levels of toxicity. Here, the characteristics and use of 2D TMDCs for biological applications are reviewed and future possibilities for these materials in biological systems are outlined. Two‐dimensional transition metal dichalcogenides demonstrate a plethora of unique properties, including tunable electronic and optical characteristics, stability in aqueous environments, large surface areas that can be manipulated and functionalized, and intercalatable layered structures. Relatively low levels of toxicity and facile synthesis routes make these materials suitable for future biological systems.
      PubDate: 2015-07-14T08:21:32.898274-05:
      DOI: 10.1002/adfm.201500891
       
  • Wireless Microfluidic Systems for Programmed, Functional Transformation of
           Transient Electronic Devices
    • Pages: 5100 - 5106
      Abstract: Electronic systems that enable programmable transformation of functional behaviors by remote control or by autonomous responses to user‐defined circumstances create unusual engineering opportunities, where physical changes in the hardware induce desired changes in operation. This paper presents materials and device architectures for technologies of this type, in which localized microfluidic chemical etching of targeted constituent components in the electronics occurs in a sequential, selective manner. Custom circuits that include reconfigurable radio‐powered thermal actuators with analog amplifiers and square waveform generators illustrate the concepts. Unusual materials and designs for electronics enable systems with the ability for on‐demand, triggered functional transformations via the use of wireless microfluidic devices that initiate dissolution of targeted constituent components in a sequential, selective manner. Demonstration examples involve reconfigurable circuits for signal processing and data encryption.
      PubDate: 2015-07-14T10:13:33.181826-05:
      DOI: 10.1002/adfm.201502192
       
  • Luminescent Silicon Diatom Replicas: Self‐Reporting and Degradable
           Drug Carriers with Biologically Derived Shape for Sustained Delivery of
           Therapeutics
    • Authors: Shaheer Maher; Mohammed Alsawat, Tushar Kumeria, Dina Fathalla, Gihan Fetih, Abel Santos, Fawzia Habib, Dusan Losic
      Pages: 5107 - 5116
      Abstract: Current development of drug microcarriers is mainly based on spherical shapes, which are not biologically favorable geometries for complex interactions with biological systems. Scalable synthesis of drug carriers with nonspherical and anisotropic shapes featuring sustained drug‐releasing performances, biocompatibility, degradability, and sensing capabilities is challenging. These challenges are addressed in this work by employing Nature's optimized designs obtained from low‐cost diatomaceous earth mineral derived from single‐cell algae diatoms. Silica diatoms with unique shapes and 3D microcapsule morphology are converted into silicon diatom replicas with identical structure by a magnesiothermic reduction process. The results reveal that prepared silicon diatoms have a set of unique properties including favorable microcapsule structure with high surface area and micro/mesoporosity providing high drug loading, fast biodegradability, and intrinsic luminescence, which make them highly suitable for low‐cost production of advanced drug microcarriers. Their sustained drug release >30 days combined with self‐reporting function based on silicon luminescence properties using nonluminescent and luminescent drugs for intravitreal drug therapy is successfully demonstrated. These silicon diatoms offer promising potential toward scalable production of low‐cost and advanced microcarriers for broad medical therapies, including theranostics and microrobotic guided drug delivery devices. Toward the development of advanced self‐reporting microcarriers with biologically derived shapes for sustained drug delivery. Luminescent silicon diatoms replicas prepared from silica diatoms by a simple magnesiothermic reduction process feature outstanding drug delivery capacity, biodegradability, and self‐reporting capabilities, which make them outstanding candidates for advanced microcarriers for intravitreal and other medical therapies.
      PubDate: 2015-07-14T10:07:39.139248-05:
      DOI: 10.1002/adfm.201501249
       
  • How Does Moisture Affect the Physical Property of Memristance for
           Anionic–Electronic Resistive Switching Memories?
    • Authors: Felix Messerschmitt; Markus Kubicek, Jennifer L. M. Rupp
      Pages: 5117 - 5125
      Abstract: Memristors based on anionic–electronic resistive switches represent a promising alternative to transistor‐based memories because of their scalability and low power consumption. To date, studies on resistive switching have focused on oxygen anionic or electronic defects leaving protonic charge‐carrier contributions out of the picture despite the fact that many resistive switching oxides are well‐established materials in resistive humidity sensors. Here, the way memristance is affected by moisture for the model material strontium titanate is studied. First, characterize own‐processed Pt SrTiO3‐δ Pt bits via cyclic voltammetry under ambient conditions are thoroughly characterized. Based on the high stability of a non‐volatile device structures the impact of relative humidity to the current–voltage profiles is then investigated. It is found that Pt SrTiO3‐δ Pt strongly modifies the resistance states by up to 4 orders of magnitude as well as the device's current–voltage profile shape, number of crossings, and switching capability with the level of moisture exposure. Furthermore, a reversible transition from classic memristive behavior at ambient humidity to a capacitively dominated one in dry atmosphere for which the resistive switching completely vanishes is demonstrated for the first time. The results are discussed in relation to the changed Schottky barrier by adsorbed surface water molecules and its interplay with the charge transfer in the oxide. The memristive response in anionic‐electronic resistive switching devices is incontestably related to the humidity level of the surrounding air. Water molecules present in the air are incorporated into the oxide thin film and interfere strongly with the space‐charge region at the metal oxide interface, thus affecting the resistive switching of the device operating under high local electric fields.
      PubDate: 2015-07-14T08:07:26.352491-05:
      DOI: 10.1002/adfm.201501517
       
  • Effective Controlling of Film Texture and Carrier Transport of a
           High‐Performance Polymeric Semiconductor by Magnetic Alignment
    • Authors: Guoxing Pan; Fei Chen, Lin Hu, Kejun Zhang, Jianming Dai, Fapei Zhang
      Pages: 5126 - 5133
      Abstract: The controlling of molecular orientation and structural ordering of organic semiconductors is crucial to achieve high performance electronic devices. In this work, large‐area highly oriented and ordered films of an excellent electron transporter Poly{[N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)) are achieved by improved solution‐cast in high magnetic field. Microstructural characterizations reveal that the chain backbones of P(NDI2OD‐T2) are highly aligned along the applied magnetic field in the films. Based on the synchrotron‐based X‐ray diffraction analysis of the polymer films cast from different solvents, a mechanism which controls the alignment process is proposed, which emphasizes that molecular aggregates of P(NDI2OD‐T2) preformed in the solution initiate magnetic alignment and finally determine the degree of film texture. Furthermore, the time‐modulated magnetic field technique is utilized to effectively control the orientation of π‐conjugated plane of the backbones, thus the degree of face‐on molecular packing of P(NDI2OD‐T2) is enhanced significantly. Thin film transistors based on the magnetic‐aligned P(NDI2OD‐T2) films exhibit an enhancement of electron mobility by a factor of four compared to the unaligned devices, as well as a large mobility anisotropy of seven. Molecular orientation and film texture of n‐type semicrystalline polymer P(NDI2OD‐T2) at both in‐plane and out‐of‐plane directions is controlled effectively via the improved solution‐processings under high magnetic field. The mechanism on magnetically induced film growth is also elucidated. The magnetically aligned P(NDI2OD‐T2) films exhibit remarkably enhanced electron mobility and high mobility anisotropy.
      PubDate: 2015-07-14T09:08:16.079156-05:
      DOI: 10.1002/adfm.201500643
       
  • Internal Biasing in Relaxor Ferroelectric Polymer to Enhance the
           Electrocaloric Effect
    • Pages: 5134 - 5139
      Abstract: The relaxor ferroelectric materials, because of their large and reversible electric field induced polarization, have been demonstrated to possess giant electrocaloric effect (ECE) over a broad temperature range, which are attractive for refrigeration with high energy efficiency and environmental friendliness. However, high electric fields are required to generate the giant ECE in these materials, posing challenge for these materials in practical cooling devices which also require high reliability and low cost. Here, a general approach is reported, for example, establishing an internal bias field in these relaxor ferroelectric polymers, to significantly improve ECE which can be induced at low electric fields. It is demonstrated that in a polymer blend (nanocomposite) with a properly controlled normal ferroelectric in nanophase dispersion in the relaxor polymer matrix, the charge neutrality in the blends can cause an internal biasing field, leading to more than 45% enhancement in the ECE at low electric field (≈50 MV m−1). This internal biasing approach provides a universal strategy to enhance other low field responses such as the electromechanical response in relaxor ferroelectrics. By internal biasing a relaxor ferroelectric polymer, it is demonstrated numerically and experimentally that both electrocaloric effect and electrocaloric coefficient can be enhanced. This approach provides a general route to enhance low‐field electrical performances of such square‐rule materials and thus pave the way to develop smart electroactive devices with better electrical reliability and safety.
      PubDate: 2015-07-14T10:07:31.617883-05:
      DOI: 10.1002/adfm.201501840
       
  • Epitaxy on Demand
    • Authors: Maarten Nijland; Sean Thomas, Mark A. Smithers, Nirupam Banerjee, Dave H. A. Blank, Guus Rijnders, Jing Xia, Gertjan Koster, Johan E. ten Elshof
      Pages: 5140 - 5148
      Abstract: Perovskite oxide heteroepitaxy is realized on the top of inorganic nanosheets that are covering the amorphous oxide surfaces of Si substrates. Utilizing pulsed laser deposition, thin films of SrRuO3 in a (001)pc and (110)pc orientation on nanosheets of Ca2Nb3O10 and Ti0.87O2 are grown, respectively. The two types of nanosheets are patterned to locally tailor the crystallographic orientation and properties of SrRuO3. The success of our approach is demonstrated by electron backscatter diffraction and spatial magnetization maps. An unprecedented control of perovskite film growth on arbitrary substrates is illustrated in this work, and the methods that are developed to deposit SrRuO3 thin films are a viable starting point for growth of artificial heteroepitaxial thin films that require a bottom electrode. Control is not just reached in the direction of film growth, as the crystal orientation and film properties are regulated laterally on the surface of micropatterned nanosheets. Local control of magnetic properties is illustrated, which holds out prospects for the fabrication of next‐generation devices like noncollinear magnetic random access memories. Perovskite thin films are deposited on Si substrates covered with inorganic nano­sheets of Ca2Nb3O10 or Ti0.87O2. These nanosheets are used to control the nucleation of films that consist of a SrTiO3 buffer layer and a SrRuO3 top layer. The two types of nanosheets are micropatterned to locally tailor the crystallographic orientation, allowing lateral control of the magnetic properties of SrRuO3.
      PubDate: 2015-07-14T08:21:17.977642-05:
      DOI: 10.1002/adfm.201501483
       
  • Core–Shell Nanoparticles: Characterizing Multifunctional Materials
           beyond Imaging—Distinguishing and Quantifying Perfect and Broken
           Shells
    • Authors: Kristina Tschulik; Kamonwad Ngamchuea, Christoph Ziegler, Max Gregor Beier, Christine Damm, Alexander Eychmueller, Richard G. Compton
      Pages: 5149 - 5158
      Abstract: Core–shell nanoparticles (NPs) are amongst the most promising candidates in the development of new functional materials. Their fabrication and characterization are challenging, in particular when thin and intact shells are needed. To date no technique has been available that differentiates between intact and broken or cracked shells. Here a method is presented to distinguish and quantify these types of shells in a single cyclic voltammetry experiment by using the different electrochemical reactivities of the core and the shell material. A simple comparison of the charge measured during the stripping of the core material before and after the removal of the shell makes it possible to determine the quality of the shells and to estimate their thickness. As a proof‐of‐concept two multifunctional examples of core–shell NPs, Fe3O4@Au and Au@SnO2, are used. This general and original method can be applied whenever core and shell materials show different redox properties. Because billions of NPs are probed simultaneously and at a low cost, this method is a convenient new screening tool for the development of new multifunctional core–shell materials and is hence a powerful complementary technique or even an alternative to the state‐of‐the‐art characterization of core–shell NPs by TEM. A method of characterizing multifunctional materials beyond imaging is presented, distinguishing and quantifying intact and broken or cracked core–shell nanoparticles by using the different redox reactivities of the core and the shell material. Fe3O4@Au and Au@SnO2 samples are studied as two proof‐of‐concept systems.
      PubDate: 2015-07-14T09:49:48.425492-05:
      DOI: 10.1002/adfm.201501556
       
  • Catalase Nanocapsules Protected by Polymer Shells for Scavenging Free
           Radicals of Tobacco Smoke
    • Authors: Lizhi Liu; Wei Yu, Dan Luo, Zhenjie Xue, Xiaoyun Qin, Xiaohua Sun, Jincai Zhao, Jianlong Wang, Tie Wang
      Pages: 5159 - 5165
      Abstract: Free radicals in tobacco smoke trigger numerous lung diseases, which are worldwide health considerations. The ideal free‐radical, tobacco‐smoke scavenger must be highly reactive and temperature resistant. Catalases (CATs) show attractive potential to scavenge free radicals in tobacco smoke, because of their higher reaction rate compared to that of non‐catalyzed reactions. Their fragile nature, however, diminishes their catalytic activity in hot tobacco smoke. Therefore, it is essential to enhance the structural integrity and catalytic stability of these enzymes under severe environmental conditions. In order to improve the thermal stability of CATs, we have developed a facile approach to produce CAT nanocapsules (nCATs) by encapsulating a single enzyme in a polyacrylamide (PAAM) shell. The rigid polymer shells on the CATs surface prevents their free deformation. The secondary structure of the enzyme is retained and their dissociation is almost nil even under high operational temperatures. As a result, the structural stability and thermal resistance of the enzyme are significantly enhanced. The nCATs are covalently bound on cellulose acetate fibers to enable the enzyme sticking to the cigarette filters.The electron paramagnetic resonance (EPR) and Saltzman procedure reveal that the nCATs are able to efficiently scavenge 90% of the free radicals in tobacco smoke. The use of such nCATs with improved enzyme thermal stability opens up new opportunities for future application in cigarette filters. The catalytic activity of catalases can be retained by encapsulating the enzymes in rigid polymer shells. The covalent bonding with the polymer shells protects the catalases from dissociating into subunits under high operational temperature. As‐prepared catalase nanocapsules can be incorporated in cigarette filters as scavengers to clean free radicals from tobacco smoke.
      PubDate: 2015-07-14T14:00:15.664063-05:
      DOI: 10.1002/adfm.201501850
       
  • Enhancement in Organic Photovoltaic Efficiency through the Synergistic
           Interplay of Molecular Donor Hydrogen Bonding and π‐Stacking
    • Authors: Nathan T. Shewmon; Davita L. Watkins, Johan F. Galindo, Raghida Bou Zerdan, Jihua Chen, Jong Keum, Adrian E. Roitberg, Jiangeng Xue, Ronald K. Castellano
      Pages: 5166 - 5177
      Abstract: For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom‐up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H‐bonding) interactions between π‐conjugated electron donor molecules encourage formation of vertically aligned donor π‐stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groups that are either capable or incapable of self‐complementary H‐bonding. When applied to OPVs, the H‐bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H‐bond promoted assembly results in redshifted absorption (in neat films and donor:C60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X‐ray scattering reveals a synergistic interplay of lateral H‐bonding interactions and vertical π‐stacking for directing the favorable morphology of the BHJ. Tailored hydrogen‐bonding interactions between molecular donors in blends with C60 result in vertically aligned π‐stacks, shorter π‐stacking distances, higher charge collection efficiency, and redshifted absorption relative to non‐H‐bonding comparator molecules. For two quaterthiophene families, the benefits result in a twofold enhancement in power conversion efficiency and a maximum external quantum efficiency of 64% in photovoltaic devices.
      PubDate: 2015-07-20T05:08:59.72704-05:0
      DOI: 10.1002/adfm.201501815
       
  • Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition
    • Pages: 5178 - 5183
      Abstract: Effective recognition of enzymatically active tetrameric acetylcholinesterase (AChE) is accomplished by a hybrid nanofilm composed of a propidium‐terminated self‐assembled monolayer (Prop‐SAM) which binds AChE via its peripheral anionic site (PAS) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer of a novel carboxylate‐modified derivative of 3,4‐propylenedioxythiophene. The rebinding of the AChE to the MIP/Prop‐SAM nanofilm covered electrode is detected by measuring in situ the enzymatic activity. The oxidative current of the released thiocholine is dependent on the AChE concentration from ≈0.04 × 10−6 to 0.4 × 10−6m. An imprinting factor of 9.9 is obtained for the hybrid MIP, which is among the best values reported for protein imprinting. The dissociation constant characterizing the strength of the MIP‐AChE binding is 4.2 × 10−7m indicating the dominant role of the PAS‐Prop‐SAM interaction, while the benefit of the MIP nanofilm covering the Prop‐SAM layer is the effective suppression of the cross‐reactivity toward competing proteins as compared with the Prop‐SAM. The threefold selectivity gain provided by i) the “shape‐specific” MIP filter, ii) the propidium‐SAM, iii) signal generation only by the AChE bound to the nanofilm shows promise for assessing AChE activity levels in cerebrospinal fluid. Recognition of tetrameric acetylcholinesterase (AChE), a potential marker of Alzheimer's disease, is accomplished by a hybrid nanofilm consisting of a propidium‐terminated self‐assembled monolayer (SAM) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer. A threefold selectivity gain is provided by i) the “shape‐specific” MIP filter, ii) the propidium‐SAM, and iii) signal generation only by the AChE bound to the nanofilm.
      PubDate: 2015-07-14T10:06:49.506618-05:
      DOI: 10.1002/adfm.201501900
       
  • Hierarchical Tubular Structures Composed of Mn‐Based Mixed Metal
           Oxide Nanoflakes with Enhanced Electrochemical Properties
    • Pages: 5184 - 5189
      Abstract: In this work, a simple strategy is developed to synthesize hierarchical tubular structures (HTS) of Mn‐based (Co‐Mn, Ni‐Mn, Cu‐Mn, Zn‐Mn) mixed metal oxides. The first step in the synthesis involves redox reaction mediated growth of nanoflakes on carbon nanofibers under hydrothermal conditions. After calcination in air, carbon nanofibers are removed and HTS of mixed metal oxides can be obtained with little structural deterioration. The resultant HTS are advantageous as electrodes for electrochemical energy storage. As an example, it is shown that the Co‐Mn‐HTS sample exhibits outstanding electrochemical performance as electrode materials for hybrid supercapacitors and lithium ion batteries. A general strategy is developed for the synthesis of hierarchical tubular structures of Mn‐based mixed metal oxides. The derived Co‐Mn mixed oxide hierarchical tubular structures manifest enhanced electrochemical properties as electrodes for both hybrid supercapacitors and lithium ion batteries.
      PubDate: 2015-07-14T09:07:57.563174-05:
      DOI: 10.1002/adfm.201501974
       
  • Study of Configuration Differentia and Highly Efficient, Deep‐Blue,
           Organic Light‐Emitting Diodes Based on Novel
           Naphtho[1,2‐d]imidazole Derivatives
    • Pages: 5190 - 5198
      Abstract: Two novel naphtho[1,2‐d]imidazole derivatives are developed as deep‐blue, light‐emitting materials for organic light‐emitting diodes (OLEDs). The 1H‐naphtho[1,2‐d]imidazole based compounds exhibit a significantly superior performance than the 3H‐naphtho[1,2‐d]imidazole analogues in the single‐layer devices. This is because they have a much higher capacity for direct electron‐injection from the cathode compared to their isomeric counterparts resulting in a ground‐breaking EQE (external quantum efficiency) of 4.37% and a low turn‐on voltage of 2.7 V, and this is hitherto the best performance for a non‐doped single‐layer fluorescent OLED. Multi‐layer devices consisting of both hole‐ and electron‐transporting layers, result in identically excellent performances with EQE values of 4.12–6.08% and deep‐blue light emission (Commission Internationale de l'Eclairage (CIE) y values of 0.077–0.115) is obtained for both isomers due to the improved carrier injection and confinement within the emissive layer. In addition, they showed a significantly better blue‐color purity than analogous molecules based on benzimidazole or phenanthro[9,10‐d]imidazole segments. Novel naphtho[1,2‐d]imidazole derivatives are developed as light‐emitting materials for OLEDs. 1H‐naphtho[1,2‐d]imidazole based compounds exhibit a significantly superior performance than their isomeric counterparts in the single‐layer devices owing to the much higher electron injection ability directly from the cathode. However, in the multi‐layer devices, uniformly high efficiencies are obtained with a desirable bluecolor that is more pure than that of their benzimidazole and phenanthro[9,10‐d]imidazole analogues.
      PubDate: 2015-07-14T09:07:42.29903-05:0
      DOI: 10.1002/adfm.201502163
       
  • Functionalized Graphene Superlattice as a Single‐Sheet Solar Cell
    • Authors: Huashan Li; David A. Strubbe, Jeffrey C. Grossman
      Pages: 5199 - 5205
      Abstract: In‐plane heterostructure engineering provides unique opportunities to control device properties. Here, a single‐sheet solar cell made of a graphene sheet functionalized into 1D channels is explored. Compared to vertical heterostructure architectures based on 2D materials, the single‐sheet solar cell shows potential for improved robustness against defects, enhancement of polaron dissociation, extra freedom for functionalization, and coverage of the entire solar spectrum. The partition width, device length, and functionalizations can be tuned independently to optimize the key optoelectronic properties for photovoltaic performance. The device performance of a single‐sheet solar cell made of graphene sheet functionalized into 1D stripes is analyzed using a combination of ab initio simulation and scaling analysis, as a prototype system of in‐plane heterostructure engineering. The results suggests highly correlated optoelectronic properties can be optimized simultaneously via independent tuning of the partition width, device length, and functionalizations.
      PubDate: 2015-07-14T08:20:13.054307-05:
      DOI: 10.1002/adfm.201501906
       
  • Bioinspired Blood Compatible Surface Having Combined Fibrinolytic and
           Vascular Endothelium‐Like Properties via a Sequential
           Coimmobilization Strategy
    • Authors: Wenjun Zhan; Xiujuan Shi, Qian Yu, Zhonglin Lyu, Limin Cao, Hui Du, Qi Liu, Xin Wang, Gaojian Chen, Dan Li, John L. Brash, Hong Chen
      Pages: 5206 - 5213
      Abstract: Developing surfaces with antithrombotic properties is of great interest for the applications of blood‐contacting biomaterials and medical devices. It is promising to coimmobilize two or more biomolecules with different and complementary functions to improve blood compatibility. However, the general one‐pot strategy usually adopted by previous studies suffers the problems of inevitable competition between diverse biomolecules and uncontrollability of the relative quantities of the immobilized biomolecules. To solve these problems, a new sequential coimmobilization strategy is proposed and applied to fabricate a blood compatible surface. Polyurethane surface is modified with a copolymer, poly(2‐hydroxyethyl methacrylate‐co‐1‐adamantan‐1‐ylmethyl methacrylate), which serves as a linker‐spacer for sequential attachment of two functional molecules, a hexapeptide containing REDV (Arg‐Glu‐Asp‐Val) sequence, and a modified cyclodextrin bearing 7 lysine ligands, through covalent bonding and host–guest interaction, respectively. The resulting surface combines the antithrombogenic properties of the vascular endothelium and the clot lysing properties of the fibrinolytic system. Importantly, neither of the two functions of REDV peptide and lysine is compromised by the presence of the other, suggesting the enhanced blood compatibility. These results suggest a new strategy to engineer multifunctional surfaces by coimmobilization of bioactive molecules having unique functionalities. A bioinspired, blood compatible surface is developed with the capability to both lyse nascent clots and promote endothelialization. The surface is fabricated by sequential coimmobilization of two biomolecules with respective properties via host–guest interaction and covalent bonding, respectively. Neither function of the two biomolecules is compromised by the presence of the other.
      PubDate: 2015-07-14T08:21:04.697035-05:
      DOI: 10.1002/adfm.201501642
       
  • Low‐Temperature Processable High‐Performance Electrochemically
           Deposited p‐Type Cuprous Oxides Achieved by Incorporating a Small
           Amount of Antimony
    • Authors: Seung Ki Baek; Yong Hun Kwon, Jae Hui Shin, Ho Seong Lee, Hyung Koun Cho
      Pages: 5214 - 5221
      Abstract: The development of an electrochemically robust method for the low‐temperature deposition of cuprous oxide (Cu2O) thin films with reliable and conductive p‐type characteristics could yield breakthroughs in earth abundant and ecofriendly all oxide‐based photoelectronic devices. The incorporation of the group‐V element antimony (Sb) in the solution‐based electrodeposition process has been investigated. A small amount of Sb (1.2 at%) in the Cu2O resulted in rapid nucleation and coalescence at the initial stage of electrochemical reaction, and finally made the surface morphology smooth in 2D. The growth behavior changed due to Sb addition and produced a strong diffraction intensity, single‐domain‐like diffraction patterns, and low angle tilt boundaries in the Cu2O:Sb film, implying extremely improved crystallinity. As a result, these films exhibited extraordinary optical transmittance and band‐to‐band photoluminescence emission as well as higher electrical conductivity. The Cu/Cu2O:Sb Schottky diode showed good rectifying characteristics and more sensible photoresponsibility. Highly stable p‐type cuprous oxide films with extremely improved optical performance are achieved by simple low‐temperature electrochemical deposition in the presence of antimony dopants. The Cu2O:Sb films demonstrate single‐domain‐like crystallinity with low angle tilted boundaries and exhibit semitransparent properties.
      PubDate: 2015-07-14T09:51:59.145884-05:
      DOI: 10.1002/adfm.201501323
       
  • Ultrafine Amorphous SnOx Embedded in Carbon Nanofiber/Carbon Nanotube
           Composites for Li‐Ion and Na‐Ion Batteries
    • Pages: 5222 - 5228
      Abstract: Core–shell‐structured, ultrafine SnOx/carbon nanofiber (CNF)/carbon nanotube composite films are in situ synthesized by electrospinning through a dual nozzle. The carbon shell layer functions as a buffer to prevent the separation of SnOx particles from the CNF core, allowing full utilization of high‐capacity SnOx in both Li‐ion and Na‐ion batteries. The composite electrodes reveal an anomalous Li‐ and Na‐ion storage mechanism where all the intermediate phases, like LixSn and NaxSn alloys, maintain amorphous states during the entire charge/discharge process. The uniform dispersion on an atomic scale and the amorphous state of the SnOx particles remain intact in the carbon matrix without growth or crystallization even after 300 cycles, which is responsible for sustaining excellent capacity retention of the electrodes. These discoveries not only shed new insights into fundamental understanding of the electrochemical behavior of SnOx electrodes but also offer a potential strategy to improve the cyclic stability of other types of alloy anodes that suffer from rapid capacity decays due to large volume changes. Li‐ion and Na‐ion storage behaviors of ultrafine amorphous SnOx particles embedded in carbon nanofiber/carbon nanotube composites are investigated. They reveal an anomalous electrochemical mechanism with all intermediate phases maintaining an amorphous state during the entire charge/discharge process, which gives rise to excellent reversibility of the electrodes.
      PubDate: 2015-07-14T14:00:44.80087-05:0
      DOI: 10.1002/adfm.201501498
       
  • A New Salt‐Baked Approach for Confining Selenium in Metal
           Complex‐Derived Porous Carbon with Superior Lithium Storage
           Properties
    • Authors: Xiaona Li; Jianwen Liang, Zhiguo Hou, Wanqun Zhang, Yan Wang, Yongchun Zhu, Yitai Qian
      Pages: 5229 - 5238
      Abstract: For lithium‐selenium batteries, commercial applications are hindered by the inferior electrical conductivity of selenium and the low utilization ratio of the active selenium. Here, we report a new baked‐in‐salt approach to enable Se to better infiltrate into metal‐complex‐derived porous carbon (Se/MnMC‐B). The approach uses the confined, narrow space that is sandwiched between two compact NaCl solid disks, thus avoiding the need for protection with argon or a vacuum environment during processing. The electrochemical properties for both lithium and sodium storage of our Se/MnMC‐B cathode were found to be outstanding. For lithium storage, the Se/MnMC‐B cathode (with 72% selenium loading) exhibited a capacity of 580 mA h g−1 after 1000 cycles at 1 C, and an excellent rate capability was achieved at 20 C and 510 mA h g−1. For sodium storage, a specific capacity of 535 mA h g−1 was achieved at 0.1 C after 150 cycles. These results demonstrate the potential of this approach as a new effective general synthesis method for confining other low melting point materials into a porous carbon matrix. A new baked‐in‐salt approach to let Se infiltrate into porous carbon is proposed, without the need for a protective argon or vacuum environment. The use of NaCl, which has a higher specific heat capacity than Se, assures an almost constant fabrication temperature, by reducing temperature fluctuations in the system. The Se/C sample exhibits excellent electrochemical performance both in Li–Se and Na–Se batteries. Furthermore, this approach should also be effective for confining other low melting point materials into porous carbon.
      PubDate: 2015-07-16T06:06:12.347197-05:
      DOI: 10.1002/adfm.201501956
       
  • Microcarriers: Luminescent Silicon Diatom Replicas: Self‐Reporting
           and Degradable Drug Carriers with Biologically Derived Shape for Sustained
           Delivery of Therapeutics (Adv. Funct. Mater. 32/2015)
    • Authors: Shaheer Maher; Mohammed Alsawat, Tushar Kumeria, Dina Fathalla, Gihan Fetih, Abel Santos, Fawzia Habib, Dusan Losic
      Pages: 5240 - 5240
      Abstract: A. Santos, D. Losic, and co‐workers demonstrate on page 5107 the preparation of luminescent silicon diatom replicas with unique porous microcapsule structures, by conversion from silica diatoms using a reduction process. These silicon diatoms are biodegradable and have intrinsic luminescence, sensing and drug‐releasing properties which make them outstanding candidates for low‐cost micro‐carriers for drug delivery, theranostics, and guided micro‐robotic devices.
      PubDate: 2015-08-25T04:04:37.877833-05:
      DOI: 10.1002/adfm.201570218
       
 
 
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