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  Subjects -> CHEMISTRY (Total: 765 journals)
    - ANALYTICAL CHEMISTRY (45 journals)
    - CHEMISTRY (530 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (24 journals)
    - INORGANIC CHEMISTRY (40 journals)
    - ORGANIC CHEMISTRY (40 journals)
    - PHYSICAL CHEMISTRY (64 journals)

CHEMISTRY (530 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal  
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: 23)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 13)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 7)
ACS Macro Letters     Full-text available via subscription   (Followers: 17)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 24)
ACS Nano     Full-text available via subscription   (Followers: 234)
ACS Photonics     Full-text available via subscription   (Followers: 2)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 8)
Acta Chemica Iasi     Open Access  
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: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 2)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 4)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 8)
Advanced Functional Materials     Hybrid Journal   (Followers: 32)
Advances in Chemical Engineering and Science     Open Access   (Followers: 21)
Advances in Chemical Science     Open Access   (Followers: 8)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 13)
Advances in Drug Research     Full-text available via subscription   (Followers: 17)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 12)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 12)
Advances in Nanoparticles     Open Access   (Followers: 11)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Polymer Science     Hybrid Journal   (Followers: 38)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 10)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 4)
African Journal of Chemical Education     Open Access   (Followers: 1)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 2)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access  
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alchemy     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 27)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 141)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 17)
American Journal of Plant Physiology     Open Access   (Followers: 9)
American Mineralogist     Full-text available via subscription   (Followers: 2)
Analyst     Full-text available via subscription   (Followers: 34)
Angewandte Chemie     Hybrid Journal   (Followers: 14)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 187)
Annales UMCS, Chemia     Open Access   (Followers: 2)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 1)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 2)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 12)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 12)
Applied Surface Science     Hybrid Journal   (Followers: 14)
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  
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 173)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 4)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 4)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 30)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 24)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 12)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 12)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Carbohydrate Research     Hybrid Journal   (Followers: 10)
Carbon     Hybrid Journal   (Followers: 34)
Catalysis for Sustainable Energy     Open Access   (Followers: 1)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 4)
Catalysis Science and Technology     Free   (Followers: 4)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 6)
Cellulose     Hybrid Journal   (Followers: 4)
Central European Journal of Chemistry     Hybrid Journal   (Followers: 5)
Cereal Chemistry     Full-text available via subscription   (Followers: 3)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Functional Materials
   [34 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  [1603 journals]   [SJR: 4.862]   [H-I: 136]
  • Engineering of Multifunctional Nano‐Micelles for Combined
           Photothermal and Photodynamic Therapy Under the Guidance of Multimodal
           Imaging
    • Authors: Hua Gong; Ziliang Dong, Yumeng Liu, Shengnan Yin, Liang Cheng, Wenyao Xi, Jian Xiang, Kai Liu, Yonggang Li, Zhuang Liu
      Pages: n/a - n/a
      Abstract: The integration of diagnostic and therapeutic functionalities on a single theranostic nano‐system holds great promise to enhance the accuracy of diagnosis and improve the efficacy of therapy. Herein, a multifunctional polymeric nano‐micelle system that contains a photosensitizer chlorin e6 (Ce6) is successfully fabricated, at the same time serving as a chelating agent for Gd3+, together with a near‐infrared (NIR) dye, IR825. With a r1 relativity 7 times higher than that of the commercial agent Magnevist, strong fluorescence offered by Ce6, and high NIR absorbance attributed to IR825, these theranostic micelles can be utilized as a contrast agent for triple modal magnetic resonance (MR), fluorescence, and photoacoustic imaging of tumors in a mouse model. The combined photothermal and photodynamic therapy is then carried out, achieving a synergistic anti‐tumor effect both in vitro and in vivo. Different from single photo treatment modalities which only affect the superficial region of the tumor under mild doses, the combination therapy at the same dose using this agent is able to induce significant damage to both superficial and deep parts of the tumor. Therefore, this work presents a polymer based theranostic platform with great potential in multimodal imaging and combination therapy of cancer. Multifunctional polymeric nano‐micelles containing a photosensitizer, which at the same time serves as a chelating agent for Gd(III), together with a near‐infrared absorbing dye, are fabricated. Utilizing these theranostic nano‐micelles, combined photothermal and photodynamic therapy, which is guided under triple‐modal magnetic resonance, fluorescence, and photoacoustic imaging, is conducted, achieving a synergistic anti‐tumor effect in a mouse model.
      PubDate: 2014-08-15T03:05:35.359341-05:
      DOI: 10.1002/adfm.201401451
       
  • Reversible Switching of Liquid Crystalline Order Permits Synthesis of
           Homogeneous Populations of Dipolar Patchy Microparticles
    • Authors: Xiaoguang Wang; Daniel S. Miller, Juan J. de Pablo, Nicholas L. Abbott
      Pages: n/a - n/a
      Abstract: The spontaneous positioning of colloids on the surfaces of micrometer‐sized liquid crystal (LC) droplets and their subsequent polymerization offers the basis of a general and facile method for the synthesis of patchy microparticles. The existence of multiple local energetic minima, however, can generate kinetic traps for colloids on the surfaces of the LC droplets and result in heterogeneous populations of patchy microparticles. To address this issue, herein it is demonstrated that adsorbate‐driven switching of the internal configurations of LC droplets can be used to sweep colloids to a single location on the LC droplet surfaces, thus resulting in the synthesis of homogeneous populations of patchy microparticles. The surface‐driven switching of the LC can be triggered by addition of surfactant or salts, and permits the synthesis of dipolar microparticles as well as “Janus‐like” microparticles. By using magnetic colloids, the utility of the approach is illustrated by synthesizing magnetically responsive patchy microdroplets of LC with either dipolar or quadrupolar symmetry that exhibit distinct optical responses upon application of an external magnetic field. Switching of the internal configurations of micrometer‐sized droplets of liquid crystal is used to uniformly position colloids on their surfaces, thus enabling formation of homogeneous populations of patchy microdroplets. The method is generalizable and, when combined with photo‐polymerization of the droplets, can be utilized for synthesis of solid “Janus‐like” microparticles or functional patchy microparticles with dipolar symmetry, including magnetically responsive systems.
      PubDate: 2014-08-15T03:05:29.849767-05:
      DOI: 10.1002/adfm.201400911
       
  • Control of Ambipolar and Unipolar Transport in Organic Transistors by
           Selective Inkjet‐Printed Chemical Doping for High Performance
           Complementary Circuits
    • Authors: Dongyoon Khim; Kang‐Jun Baeg, Mario Caironi, Chuan Liu, Yong Xu, Dong‐Yu Kim, Yong‐Young Noh
      Pages: n/a - n/a
      Abstract: The selective tuning of the operational mode from ambipolar to unipolar transport in organic field‐effect transistors (OFETs) by printing molecular dopants is reported. The field‐effect mobility (μFET) and onset voltage (Von) of both for electrons and holes in initially ambipolar methanofullerene [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) OFETs are precisely modulated by incorporating a small amount of cesium fluoride (CsF) n‐type dopant or tetrafluoro‐tetracyanoquinodimethane (F4‐TCNQ) p‐type dopant for n‐channel or p‐channel OFETs either by blending or inkjet printing of the dopant on the pre‐deposited semiconductor. Excess carriers introduced by the chemical doping compensate traps by shifting the Fermi level (EF) toward respective transport energy levels and therefore increase the number of mobile charges electrostatically accumulated in channel at the same gate bias voltage. In particular, n‐doped OFETs with CsF show gate‐voltage independent Ohmic injection. Interestingly, n‐ or p‐doped OFETs show a lower sensitivity to gate‐bias stress and an improved ambient stability with respect to pristine devices. Finally, complementary inverters composed of n‐ and p‐type PCBM OFETs are demonstrated by selective doping of the pre‐deposited semiconductor via inkjet printing of the dopants. Local molecular doping via inkjet printing of dopants on a pre‐coated ambipolar semiconductors is demonstrated to unipolarize and optimize complementary transistors. The mobility and turn‐on voltages both for electrons and holes are precisely modulated by doping. Finally, high performance complementary ambipolar inverters are achieved by the selective inkjet printing of n‐ and p‐type dopant.
      PubDate: 2014-08-15T03:05:26.096071-05:
      DOI: 10.1002/adfm.201400850
       
  • Microflotronics: A Flexible, Transparent, Pressure‐Sensitive
           Microfluidic Film
    • Authors: Ruya Li; Baoqing Nie, Philip Digiglio, Tingrui Pan
      Pages: n/a - n/a
      Abstract: There is an increasing demand for sensitive, flexible, and low‐cost pressure sensing solutions for health monitoring, wearable sensing, robotic and prosthetic applications. Here, the first flexible and pressure‐sensitive microfluidic film is reported, referred to as a microflotronic, with high transparency and seamless integratability with the state‐of‐the‐art microelectronics. The microflotronic film represents the initial effort to utilize a continuous microfluidic layer as the sensing elements for large‐area dynamic pressure mapping applications, and meanwhile an ultrahigh sensitivity of 0.45 kPa−1 has been achieved in a compact, flexible, and transparent packaging. The response time of the device is in the millisecond range, which is at least an order of magnitude faster than that of its conventional flexible solid‐state counterparts. In addition, the fabrication process of the device is fully compatible with the industrial‐scale manufacturing of capacitive touchscreen devices and liquid‐crystal displays. The overall device packaging can be as thin as 200 μm with an optical transparency greater than 80%. Several practical applications were successfully demonstrated, including surface topology mapping and dynamic blood pressure monitoring. The microflotronic devices offer an alternative approach to the solid‐state pressure sensors, by offering an unprecedented sensitivity and ultrafast response time in a completely transparent, flexible and adaptive platform. A flexible, transparent, and pressure‐sensitive microfluidic film, referred to as a microflotronic, is reported for large‐area dynamic pressure mapping applications. Utilizing a continuous microfluidic layer as the sensing elements, the microflotronic devices offer an alternative approach to the solid‐state pressure sensors, by offering an unprecedented sensitivity and ultrafast response time in a completely transparent, flexible, and adaptive platform.
      PubDate: 2014-08-14T14:17:04.841805-05:
      DOI: 10.1002/adfm.201401527
       
  • Hierarchical Composite Electrodes of Nickel Oxide Nanoflake 3D Graphene
           for High‐Performance Pseudocapacitors
    • Authors: Chundong Wang; Junling Xu, Muk‐Fung Yuen, Jie Zhang, Yangyang Li, Xianfeng Chen, Wenjun Zhang
      Pages: n/a - n/a
      Abstract: NiO nanoflakes are created with a simple hydrothermal method on 3D (three‐dimensional) graphene scaffolds grown on Ni foams by microwave plasma enhanced chemical vapor deposition (MPCVD). Such as‐grown NiO‐3D graphene hierarchical composites are then applied as monolithic electrodes for a pseudo‐supercapacitor application without needing binders or metal‐based current collectors. Electrochemical measurements impart that the hierarchical NiO‐3D graphene composite delivers a high specific capacitance of ≈1829 F g−1 at a current density of 3 A g−1 (the theoretical capacitance of NiO is 2584 F g−1). Furthermore, a full‐cell is realized with an energy density of 138 Wh kg−1 at a power density of 5.25 kW kg−1, which is much superior to commercial ones as well as reported devices in asymmetric capacitors of NiO. More attractively, this asymmetric supercapacitor exhibits capacitance retention of 85% after 5000 cycles relative to the initial value of the 1st cycle. Hierarchical nickel oxide nanoflake 3D graphene electrodes are developed by growing NiO nanoflakes atop 3D architecture of graphene on Ni foam. The optimum structure enables the 3‐electrode pseudocapacitors and 2‐electrode full cells to deliver outstanding electrochemical performance. In a full cell configuration, the achieved power density is much higher than that of commercially available asymmetric capacitors.
      PubDate: 2014-08-14T14:17:01.21004-05:0
      DOI: 10.1002/adfm.201401216
       
  • High Throughput, Polymeric Aqueous Two‐Phase Printing of Tumor
           Spheroids
    • Authors: Ehsan Atefi; Stephanie Lemmo, Darcy Fyffe, Gary D. Luker, Hossein Tavana
      Pages: n/a - n/a
      Abstract: This paper presents a new 3D culture microtechnology for high throughput production of tumor spheroids and validates its utility for screening anti‐cancer drugs. Two immiscible polymeric aqueous solutions are used and a submicroliter drop of the “patterning” phase containing cells is microprinted into a bath of the “immersion” phase. Selecting proper formulations of biphasic systems using a panel of biocompatible polymers results in the formation of a round drop that confines cells to facilitate spontaneous formation of a spheroid without any external stimuli. Adapting this approach to robotic tools enables straightforward generation and maintenance of spheroids of well‐defined size in standard microwell plates and biochemical analysis of spheroids in situ, which is not possible with existing techniques for spheroid culture. To enable high throughput screening, a phase diagram is established to identify minimum cell densities within specific volumes of the patterning drop to result in a single spheroid. Spheroids show normal growth over long‐term incubation and dose‐dependent decrease in cellular viability when treated with drug compounds, but present significant resistance compared to monolayer cultures. The unprecedented ease of implementing this microtechnology and its robust performance will benefit high throughput studies of drug screening against cancer cells with physiologically relevant 3D tumor models. Utilizing polymeric aqueous two‐phase systems, an aqueous drop containing cancer cells within an immiscible, immersion aqueous phase is microprinted to facilitate aggregation of cells into a viable tumor spheroid, and the utility of this approach is demonstrated for high throughput, quantitative drug screening with 3D cultures of cells.
      PubDate: 2014-08-14T14:16:56.786981-05:
      DOI: 10.1002/adfm.201401302
       
  • Light‐modulated TiOx Interlayer Dipole and Contact Activation in
           Organic Solar Cell Cathodes
    • Authors: Antonio Guerrero; Sylvain Chambon, Lionel Hirsch, Germà Garcia‐Belmonte
      Pages: n/a - n/a
      Abstract: Understanding working mechanisms of selective interfacial layers and the underlying energetics of the organic semiconductor/electrode interface is an issue of primary concern for improving organic solar cell technologies. TiO x interlayers are used here to tune the selectivity of the cathode contact to electrons by controlled UV‐light activation. The S‐shaped kink observed for deactivated titania interlayers completely disappears after 2 min of UV‐light exposure yielding high fill factor (≈60%) and adequate efficiencies. UV‐light activation of complete cells alters the work function of the oxide that decreases about 650 mV as observed by Kelvin probe measurements. Capacitive techniques reveals a light‐intensity dependent shift in flat‐band voltage of up to 1.2 V under 1 sun illumination (without UV) in the case of deactivated TiO x interlayers. An increase in the magnitude of the light‐modulated dipole present at the oxide layer accounts for that voltage shift. Although the sign of the interface dipole would favor the extraction of electrons, the concomitant modification of the band bending in the organic semiconductor hinders an efficient extraction of carriers at positive voltages and originates the S‐shaped characteristics. After contact activation, the dipole strength does not change with the light intensity. Light‐modulated dipole (electron accumulation) present at TiO x interlayer accounts for the S‐shaped characteristics of organic solar cells. UV‐light activation tunes the selectivity of the cathode contact to electrons. Activated devices do not exhibit light‐dependent interface dipole. By using capacitance–voltage measurements a complete picture of the contact energetics is drawn.
      PubDate: 2014-08-14T14:15:20.344976-05:
      DOI: 10.1002/adfm.201401233
       
  • Masthead: (Adv. Funct. Mater. 31/2014)
    • Pages: n/a - n/a
      PubDate: 2014-08-14T07:12:35.535684-05:
      DOI: 10.1002/adfm.201470209
       
  • Intracellularly Degradable Hydrogen‐Bonded Polymer Capsules
    • Authors: Kristian Kempe; Sher Leen Ng, Sylvia T. Gunawan, Ka Fung Noi, Frank Caruso
      Pages: n/a - n/a
      Abstract: The assembly of low‐fouling polymer capsules with redox‐responsive behavior and intracellular degradability is reported. Thiol‐containing poly(2‐ethyl‐2‐oxazoline) (PEtOxMASH) brushes are synthesized by atom transfer radical polymerization (ATRP) of oligo(2‐ethyl‐2‐oxazoline)methacrylate and glycidyl methacrylate (GMA) and subsequent ring‐opening reaction of the GMA. Sequential deposition of PEtOxMASH/poly(methacrylic acid) (PMA) multilayers onto silica (SiO2) particle templates and crosslinking through disulfide formation yield stable capsules after the removal of the SiO2 templates by buffered hydrofluoric acid (HF). The redox‐responsive nature of the disulfide crosslinking groups enables the degradation of these capsules under simulated intracellular conditions at pH 5.9 and 5 mm glutathione (GSH). Furthermore, capsule degradation is observed after incubation with dendritic (JAWS II) cells. Even at high capsule‐to‐cell ratios, PEtOxMASH capsules show only negligible cytotoxicity. Quartz crystal microgravimetry (QCM) studies, using 100% human serum, reveal that films prepared from PEtOxMASH exhibit low‐fouling properties. The degradation and low‐fouling properties are promising for application of PEtOxMASH films/capsules for the delivery and triggered release of therapeutics. Low‐fouling, redox‐responsive polymer capsules based on functional poly(2‐oxazoline)s are assembled. These capsules are shown to degrade under simulated intracellular conditions as well as intracellularly. Their low‐fouling properties make them promising for the delivery and triggered release of therapeutics.
      PubDate: 2014-08-13T14:31:10.563704-05:
      DOI: 10.1002/adfm.201401397
       
  • Multifunctional Barium Titanate Coated Carbon Fibers
    • Authors: Christopher Bowland; Zhi Zhou, Henry A. Sodano
      Pages: n/a - n/a
      Abstract: Multifunctional materials have received significant research interest due to the potential for performance enhancements over traditional materials through the integration of responsive properties. Composite materials are ideally suited for use as multifunctional materials due to their use of two or more phases and the ease at which their properties can be anisotropically tailored. Here, a methodology for the integration of ferroelectricity into a fiber reinforced polymer composite is presented by synthesizing a barium titanate nanowire film on the surface of carbon fibers using a novel two‐step hydrothermal process. A refined piezoelectric force microscopy method is used to quantify the piezoelectric properties of the core–shell fiber resulting in an average d33 of 31.6 ± 14.5 pm V−1 and an average d31 of −5.4 ± 3.2 pm V−1. The multifunctionality of this piezoelectric coated fiber is demonstrated through excitation of a cantilevered fiber with a 0.5 g sinusoidal base acceleration at the fiber's fundamental resonant frequency, producing a root‐mean‐square voltage of 16.4 mV. This result demonstrates the ferroelectric properties of the multifunctional structural fiber and its application for sensing and energy harvesting. Barium titanate is synthesized on carbon fiber through a two‐step hydrothermal reaction to create a multifunctional fiber. The mechanical strength of the carbon fiber is preserved while adding functionality from the ferroelectric properties of barium titanate. Ferroelectric property characterization and power harvesting tests are performed on these novel multifunctional fibers.
      PubDate: 2014-08-13T02:43:46.236022-05:
      DOI: 10.1002/adfm.201401417
       
  • Pressure Sensitive Adhesion of an Elastomeric Protein Complex Extracted
           From Squid Ring Teeth
    • Authors: Abdon Pena‐Francesch; Bulent Akgun, Ali Miserez, Wenpeng Zhu, Huajian Gao, Melik C. Demirel
      Pages: n/a - n/a
      Abstract: The pressure sensitive adhesion characteristic of a protein complex extracted from squid ring teeth (SRT), which exhibits an unusual and reversible transition from a solid to a melt, is studied. The native SRT is an elastomeric protein complex that has standard amino acids, and it does not function as adhesives in nature. The SRT can be thermally shaped into any 3D geometry (e.g., thin films, ribbons, colloids), and it has a glass transition temperature of 32 °C in water. Underwater adhesion strength of the protein film is approximately 1.5–2.5 MPa. The thermoplastic protein film could potentially be used in an array of fields, including dental resins, bandages for wound healing, and surgical sutures in the body. A protein‐based adhesives extracted from squid ring teeth is introduced. Underwater adhesion strength of the protein film is approximately 1.5–2.5 MPa. This reusable and recyclable bioelastomers could potentially have a wide range of applications in wet bioadhesive development including dental resins, bandages for wound healing, and surgical sutures in the body, all of which require wet adhesion.
      PubDate: 2014-08-11T14:58:38.271051-05:
      DOI: 10.1002/adfm.201401534
       
  • Pulsed Laser Deposition of Photoresponsive Two‐Dimensional GaSe
           Nanosheet Networks
    • Authors: Masoud Mahjouri‐Samani; Ryan Gresback, Mengkun Tian, Kai Wang, Alexander A. Puretzky, Christopher M. Rouleau, Gyula Eres, Ilia N. Ivanov, Kai Xiao, Michael A. McGuire, Gerd Duscher, David B. Geohegan
      Pages: n/a - n/a
      Abstract: Synthesis of functional metal chalcogenide (GaSe) nanosheet networks by stoichiometric transfer of laser‐vaporized material from bulk GaSe targets is presented. Uniform coverage of interconnected, crystalline, and photoresponsive GaSe nanosheets in both in‐plane and out‐of‐plane orientations are achieved under different ablation conditions. The propagation of the laser‐vaporized material is characterized by in situ ICCD‐imaging. High (1 Torr) Ar background gas pressure is found to be crucial for the stoichiometric growth of GaSe nanosheet networks. Individual 1–3 layer GaSe triangular nanosheets of ≈200 nm domain size are formed within 30 laser pulses, coalescing to form nanosheet networks in as few as 100 laser pulses. The thickness of the deposited networks increases linearly with pulse number, adding layers in a two‐dimensional (2D) growth mode. GaSe nanosheet networks show p‐type semiconducting characteristics with mobilities reaching as high as 0.1 cm2V−1s−1. Spectrally‐resolved photoresponsivities and external quantum efficiencies range from 0.4 AW−1 and 100% at 700 nm, to 1.4 AW−1 and 600% at 240 nm, respectively. Pulsed laser deposition under these conditions appears to provide a versatile and rapid approach to stoichiometrically transfer and deposit functional networks of 2D nanosheets with digital thickness control and uniformity for a variety of applications. Novel synthesis techniques to rapidly explore the properties of new 2D layered materials, beyond graphene, are of significant current interest. Here, it is demonstrated that pulsed laser deposition (PLD) can be used to synthesize functional gallium selenide (GaSe) nanosheet networks by spatial confinement of the ablation plume to preserve the stoichiometric transfer of material while providing sufficient kinetic energy for surface diffusion.
      PubDate: 2014-08-11T14:58:30.491325-05:
      DOI: 10.1002/adfm.201401440
       
  • In Situ Study of Nanostructure and Electrical Resistance of Nanocluster
           Films Irradiated with Ion Beams
    • Authors: Weilin Jiang; Jennifer A. Sundararajan, Tamas Varga, Mark E. Bowden, You Qiang, John S. McCloy, Charles. H. Henager, Robert O. Montgomery
      Pages: n/a - n/a
      Abstract: An in situ study is reported on the structural evolution in nanocluster films under He+ ion irradiation using an advanced helium ion microscope. The films consist of loosely interconnected nanoclusters of magnetite or iron‐magnetite (Fe‐Fe3O4) core‐shells. The nanostructure is observed to undergo dramatic changes under ion‐beam irradiation, featuring grain growth, phase transition, particle aggregation, and formation of nanowire‐like network and nanopores. Studies based on ion irradiation, thermal annealing and electron irradiation have indicated that the major structural evolution is activated by elastic nuclear collisions, while both electronic and thermal processes can play a significant role once the evolution starts. The electrical resistance of the Fe‐Fe3O4 films measured in situ exhibits a super‐exponential decay with dose. The behavior suggests that the nanocluster films possess an intrinsic merit for development of an advanced online monitor for fast neutron radiation with both high detection sensitivity and long‐term applicability, which can enhance safety measures in many nuclear operations. An in situ study on the nanostructural evolution and electrical resistance variation of Fe3O4 and Fe‐Fe3O4 core‐shell nanocluster films under ion irradiation is presented. Grain growth, phase transition, particle aggregation, and formation of nanowire‐like network with nanopores are observed. The electrical resistance exhibits a super‐exponential decay with dose. This type of films may have potential as a sensing material for fast neutron monitoring.
      PubDate: 2014-08-11T14:58:23.456906-05:
      DOI: 10.1002/adfm.201400553
       
  • Stress and Damage Mitigation from Oriented Nanostructures within the
           Radular Teeth of Cryptochiton stelleri
    • Authors: Lessa Kay Grunenfelder; Enrique Escobar de Obaldia, Qianqian Wang, Dongsheng Li, Brian Weden, Christopher Salinas, Richard Wuhrer, Pablo Zavattieri, David Kisailus
      Pages: n/a - n/a
      Abstract: Chiton are marine mollusks who use heavily mineralized and ultrahard teeth to feed on epilithic and endolithic algae on intertidal rocks. To fulfill this function, chiton teeth must be tough and wear‐resistant. Impressive mechanical properties are achieved in the chiton tooth through a hierarchically arranged composite structure consisting of a hard shell of organic‐encased and highly oriented nanostructured magnetite rods that surround a soft core of organic‐rich iron phosphate. Microscopic and spectroscopic analyses combined with finite element simulations are used to probe the ultrastructural features and uncover structure–mechanical property relationships in the fully mineralized teeth of the gumboot chiton Cryptochiton stelleri. By understanding the effects of the nanostructured architecture within the chiton tooth, abrasion‐resistant materials can be developed for tooling and machining applications, as well as coatings for equipment and medical implants. The teeth of the chiton are hard and abrasion resistant. Local and global chemical and ultrastructural features of the teeth, as well as chemical and structural gradients which enhance fracture mitigation, are reported. Lessons obtained can be used towards the development of abrasion resistant materials for tooling and machining applications, as well as coatings for equipment and medical implants.
      PubDate: 2014-08-11T14:08:40.41293-05:0
      DOI: 10.1002/adfm.201401091
       
  • Highly Efficient TADF OLEDs: How the Emitter–Host Interaction
           Controls Both the Excited State Species and Electrical Properties of the
           Devices to Achieve Near 100% Triplet Harvesting and High Efficiency
    • Authors: Vygintas Jankus; Przemyslaw Data, David Graves, Callum McGuinness, Jose Santos, Martin R. Bryce, Fernando B. Dias, Andrew P. Monkman
      Pages: n/a - n/a
      Abstract: New emitters that can harvest both singlet and triplet excited states to give 100% internal conversion of charge into light, are required to replace Ir based phosphors in organic light emitting diodes (OLEDs). Molecules that have a charge transfer (CT) excited state can potentially achieve this through the mechanism of thermally activated delayed fluorescence (TADF). Here, it is shown that a D–A charge transfer molecule in the solid state, can emit not only via an intramolecular charge transfer (ICT) excited state, but also from exciplex states, formed between the molecule and the host material. OLEDs based on a previously studied D–A–D molecule in a host TAPC achieves >14% external electroluminescence yield and shows nearly 100% efficient triplet harvesting. In these devices, it is unambiguously established that the triplet states are harvested via TADF, but more interestingly, these results are found to be independent of whether the emitter is the ICT state or the D–A–D/host exciplex. New emitters harvesting triplets to give 100% internal efficiency are required to replace Ir based phosphors in OLEDs. Here, it is shown that a D–A molecule in the solid state emits via an intramolecular charge transfer excited state and via exciplex states, and OLEDs based on thermally activated delayed fluorescence achieve >14% external electroluminescence yield and 100% efficient triplet harvesting.
      PubDate: 2014-08-08T11:09:41.362334-05:
      DOI: 10.1002/adfm.201400948
       
  • Measuring Reduced C60 Diffusion in Crosslinked Polymer Films by Optical
           Spectroscopy
    • Authors: Florian Fischer; Tobias Hahn, Heinz Bässler, Irene Bauer, Peter Strohriegl, Anna Köhler
      Pages: n/a - n/a
      Abstract: The diffusion of fullerenes such as C60 and PCBM in organic semiconductors is a key factor in controlling the efficiency of organic solar cells, though it is challenging to measure and to control. A simple optical method based on photoluminescence quenching is developed to assess the diffusion of a quencher molecule such as C60 through a semiconducting polymer film, in this case made with the polymer polyfluorene. When the mobility of the polymer chains is reduced by chemical crosslinking, the diffusion coefficient of C60 can be reduced by up to three orders of magnitude. The diffusion of fullerenes such as C60 and PCBM in organic semiconductors can be measured using a novel simple optical method based on photoluminescence quenching. When the mobility of the polymer chains is reduced by chemical crosslinking, the diffusion coefficient of C60 can be reduced by up to three orders of magnitude.
      PubDate: 2014-08-08T11:09:38.538179-05:
      DOI: 10.1002/adfm.201401153
       
  • Helicity Control of π‐Stacked Assemblies of
           Oligo(para‐phenylene) Derivatives Using Photoresponsive Chiral
           Moieties at Terminal Sites
    • Authors: Benedict A. San Jose; Tomoki Ashibe, Naoki Tada, Shinichi Yorozuya, Kazuo Akagi
      Pages: n/a - n/a
      Abstract: Oligo(para‐phenylene) (OPP) derivatives bearing photoresponsive chiral dithienylethene (DE*) terminal moieties that induce chirality in the OPP main chain are synthesized. In the assembled state, the photoisomerization of the chiral DE* terminal moieties prior to assembly, from the open to the closed form, leads to a change in the helicity of the π‐stacked structures. The circular dichroism spectra of mixed solvent solutions and cast films of the OPP assemblies exhibit bisignate Cotton effects in the absorption region associated with the oligomer main chain: these features indicate the presence of helically π‐stacked structures. Furthermore, the chiral transcription of racemic poly(bithiophenethiophene) (PBTT) by chiral OPP in the assembled state is demonstrated. The chirally transcribed PBTT shows a change in helicity upon the photoisomerization of the chiral DE* terminal moieties of OPP. To the best of our knowledge, this is the first report of helicity control of a helically π‐stacked conjugated oligomer through the photoisomerization of a chiral photoresponsive moiety. Such assemblies could be attractive for use in optoelectronic devices and optical memory systems. Oligo(para‐phenylene) (OPP) derivatives bearing photoresponsive chiral dithienyl­ethene (DE*) terminal moieties are synthesized. Photoisomerization of the chiral DE* terminal moieties prior to assembly, from the open to closed form, changes the handedness of the helically π‐stacked structures in the assembled state. Furthermore, the chiral transcription of racemic poly(bithiophenethiophene) by the assembled chiral OPP is demonstrated.
      PubDate: 2014-08-08T00:24:00.772554-05:
      DOI: 10.1002/adfm.201401453
       
  • Creation of Superhydrophobic Electrospun Nonwovens Fabricated from
           Naturally Occurring Poly(Amino Acid) Derivatives
    • Authors: Hiroaki Yoshida; Doris Klee, Martin Möller, Mitsuru Akashi
      Pages: n/a - n/a
      Abstract: Creation of superhydrophobic materials bio‐inspired by nature fascinates many scientists. One of the most intriguing challenges in this field is the fabrication of these materials using biopolymers from the viewpoint of green chemistry and environmental chemistry. Here, superhydrophobic and biodegradable nonwovens are constructed by electrospinning from a naturally occurring poly(amino acid), poly(γ‐glutamic acid) (γ‐PGA), modified with a hydrophobic α‐amino acid, l‐phenylalanine. The contact angle of a water droplet on the materials is 154°, and the droplet remains stuck to the material surface even if it is inverted, clearly indicating a petal‐type superhydrophobic property. Biodegradability and post‐functionalization of the nonwovens as well as cell adhesion on the superhydrophobic materials are also evaluated. As far as we know, this is the first report on biodegradable materials exhibiting a petal‐type superhydrophobicity. The material design and processing shown here can be applied to various bioresources and such functional materials will become a new class of functional materials satisfying some of the requirements in green science. Superhydrophobic, biodegradable nonwovens are fabricated by electrospinning from a naturally occurring poly(amino acid). The nonwovens exhibit a petal‐type superhydrophobicity and water droplet sticks to the surface even after it is turned over. The material design and processing is applicable to different biopolymers, and such functional materials can be useful for biomedical and environmental applications.
      PubDate: 2014-08-07T01:26:24.47764-05:0
      DOI: 10.1002/adfm.201401423
       
  • Fermi Level Pinning and Orbital Polarization Effects in Molecular
           Junctions: The Role of Metal Induced Gap States
    • Authors: Colin Van Dyck; Victor Geskin, Jérôme Cornil
      Pages: n/a - n/a
      Abstract: Understanding the alignment of molecular orbitals and corresponding transmission peaks with respect to the Fermi level of the electrodes is a major challenge in the field of molecular electronics. In order to design functional devices, it is of utmost importance to assess whether controlled changes in the electronic structure of isolated compounds are preserved once they are inserted in the molecular junctions. Here, light is shed on this central issue by performing density functional theory calculations on junctions including diarylethene‐based molecules. It is demonstrated that the chemical potential equalization principle allows to rationalize the existence or not of a Fermi level pinning (i.e., same alignment in spite of a varying ionization potential in the isolated compounds), pointing to the essential role played by metal induced gap states (MIGS). It is further evidenced that the degree of level pinning is intimately linked to the degree of orbital polarization when a bias is applied between the two electrodes. The Fermi level alignment in molecular junctions can be either affected (S = 1) or unaffected (S = 0) by the modification of the ionization potential of the contacted molecule. Here, it is shown that a transition between these two behaviors is achievable by a simple substitution, while the key role of metal induced gap states (MIGS) in the alignment and orbital polarization processes is further highlighted.
      PubDate: 2014-08-05T10:25:28.005988-05:
      DOI: 10.1002/adfm.201400809
       
  • Back to Basics: Exploiting the Innate Physico‐chemical
           Characteristics of Nanomaterials for Biomedical Applications
    • Authors: Chor Yong Tay; Magdiel Inggrid Setyawati, Jianping Xie, Wolfgang J. Parak, David Tai Leong
      Pages: n/a - n/a
      Abstract: In nanomedicine design, emphasis is centered on the engineered impacts of the nanomaterials (NMs). However, failure to understand the unintended effects of nanomaterials on the cell biology can affect the overall performance, approval, and adoption in the clinic. Much of these unintended effects arise from unique physico‐chemical properties of the NMs. This feature article discusses some of the key physico‐chemical parameters of NMs and highlights how they could cause unexpected and novel biological responses, with some insights into their underlying mechanisms. Physicochemical properties of nanomaterials dictate how cells “feel” and respond to nanomaterials by eliciting distinct nanospecific bio‐interactions that can be exploited for nanomedicine. Myriad cellular responses can be invoked for medicinal applications via precise tailoring of the size, shape, surface charge, and protein corona formation on the nanomaterial surface.
      PubDate: 2014-08-01T10:32:05.195919-05:
      DOI: 10.1002/adfm.201401664
       
  • Aptamer‐Functionalized Multidimensional Conducting‐Polymer
           Nanoparticles for an Ultrasensitive and Selective
           Field‐Effect‐Transistor Endocrine‐Disruptor Sensors
    • Authors: Jun Seop Lee; Sung Gun Kim, Jaemoon Jun, Dong Hoon Shin, Jyongsik Jang
      Pages: n/a - n/a
      Abstract: An endocrine disruptor (ED) is a type of xenobiotic compound that can cause serious diseases related to the estrous cycle, as well as various types of cancer. At low ED concentrations, estrogen receptors may respond as they would under physiological conditions. In this work, aptamer‐functionalized multidimensional conducting‐polymer (3‐carboxylate polypyrrole) nanoparticles (A_M_CPPyNPs) are fabricated for use in an FET sensor to detect bisphenol A (BPA). The multidimensional system, M_CPPyNPs, is first produced by means of dual‐nozzle electrospray of pristine CPPyNPs and vapor deposition polymerization of additional conducting polymer. The M_CPPyNPs are then immobilized on an amine‐functionalized (–NH2) interdigitated‐array electrode substrate, through the formation of covalent bonds with amide groups (–CONH). The amine‐functionalized BPA‐binding aptamer is then introduced in the same way as that for M_CPPyNP immobilization. The resulting A_M_CPPyNP‐based FET sensors exhibit ultrasensitivity and selectivity towards BPA at unprecedentedly low concentrations (1 fm) and among molecules with similar structures. Additionally, due to the covalent bonding involved in the immobilization processes, a longer lifetime is expected for the FET sensor. A multidimensional system comprising conjugated‐polymer nanoparticles, whose surfaces are decorated to increase surface area and allow further polymerization, is fabricated and functionalized with an aptamer. The resulting multidimensional nanoparticles are used in field‐effect transistors (FETs) that can act as sensors of the endocrine disruptor bisphenol A (BPA). The aptamer FET sensors exhibit ultrahigh sensitivity and selectivity toward BPA, and their lifetime is expected to exceed that of other FET biosensors.
      PubDate: 2014-07-31T07:53:37.622953-05:
      DOI: 10.1002/adfm.201401166
       
  • Printed Electronics: Room‐Temperature Printing of Organic
           Thin‐Film Transistors with π‐Junction Gold Nanoparticles
           (Adv. Funct. Mater. 31/2014)
    • Authors: Takeo Minari; Yuki Kanehara, Chuan Liu, Kenji Sakamoto, Takeshi Yasuda, Asuka Yaguchi, Shigemi Tsukada, Kei Kashizaki, Masayuki Kanehara
      Pages: 4869 - 4869
      Abstract: T. Minari, M. Kanehara, and co‐workers report a method for the room‐temperature printing of electronics using gold nanoparticles, enabling semiconductor devices to be printed without the application of heat. On page 4886, organic thinfilm transistors are formed on plastic and paper through room‐temperature printing, producing devices with mobilities of 7.9 and 2.5 cm2 V−1 s−1, respectively. The proposed approach permits the printing of devices on any heat‐sensitive substrate, such as plastic, paper, or biomaterials.
      PubDate: 2014-08-14T07:12:34.844781-05:
      DOI: 10.1002/adfm.201470204
       
  • Ionene Hydrogels: Synergistic Computational‐Experimental Approach to
           Improve Ionene Polymer‐Based Functional Hydrogels (Adv. Funct.
           Mater. 31/2014)
    • Authors: Jürgen Bachl; David Zanuy, Daniel E. López‐Pérez, Guillermo Revilla‐López, Carlos Cativiela, Carlos Alemán, David Díaz Díaz
      Pages: 4870 - 4870
      Abstract: The topological constraints necessary to enhance hydrogel gelation efficiency are explored by C. Alemán, D. D. Díaz, and co‐workers. On page 4893, the performance of hydrogels made from DABCO‐containing ionene polymers is studied and compared based on the critical gelation concentration, gelation kinetics, thermal and mechanical stability, optical properties, and dispersion ability for single‐walled carbon nanotubes.
      PubDate: 2014-08-14T07:12:33.394876-05:
      DOI: 10.1002/adfm.201470205
       
  • Contents: (Adv. Funct. Mater. 31/2014)
    • Pages: 4871 - 4876
      PubDate: 2014-08-14T07:12:35.415476-05:
      DOI: 10.1002/adfm.201470206
       
  • Graphene: Oxygen‐Free Highly Conductive Graphene Papers (Adv. Funct.
           Mater. 31/2014)
    • Authors: Petr Šimek; Zdeněk Sofer, Ondřej Jankovský, David Sedmidubský, Martin Pumera
      Pages: 4877 - 4877
      Abstract: Oxygen‐free graphene storms over the desert of the Canyonlands National Park in the USA. On page 4878, a unique process for the preparation of highly conductive, thin graphene paper is demonstrated by Z. Sofer, M. Pumera, and co‐workers. They irradiate graphene oxide (GO) papers with Ar+ ion, reducing the carbon/oxygen ratio to 100:1. Such highly conductive graphene papers have great potential to be used in applications for the construction of microelectronic and sensor devices.
      PubDate: 2014-08-14T07:12:28.444553-05:
      DOI: 10.1002/adfm.201470207
       
  • Oxygen‐Free Highly Conductive Graphene Papers
    • Authors: Petr Šimek; Zdeněk Sofer, Ondřej Jankovský, David Sedmidubský, Martin Pumera
      Pages: 4878 - 4885
      Abstract: Graphene papers have a potential to overcome the gap from nanoscale graphene to real macroscale applications of graphene. A unique process for preparation of highly conductive graphene thin paper by means of Ar+ ion irradiation of graphene oxide (GO) papers, with carbon/oxygen ratio reduced to 100:1, is presented. The composition of graphene paper in terms of carbon/oxygen ratio and in terms of types of individual oxygen‐containing groups is monitored throughout the process. Angle‐resolved high resolution X‐ray photoelectron spectroscopy helps to investigate the depth profile of carbon and oxygen within reduced GO paper. C/O ratios over 100 on the surface and 40 in bulk material are observed. In order to bring insight to the processes of oxygen removal from GO paper by low energy Ar+ ion bombardment, the gases released during the irradiation are analyzed by mass spectroscopy. It is proven that Ar+ ion beam can be applied as a technique for fabrication of highly reduced graphene papers with high conductivities. Such highly conductive graphene papers have great potential to be used in application for construction of microelectronic and sensor devices. Graphene papers are prepared by irradiation of graphene oxide papers with Ar+ ion beam. Surface of the paper is chemically reduced and C/O ratios over 100 are achieved. The resulting surface is highly conductive and electrical Ohmic behavior is observed. Gases evolved during irradiation process are also analyzed.
      PubDate: 2014-04-29T06:37:50.647438-05:
      DOI: 10.1002/adfm.201304284
       
  • Room‐Temperature Printing of Organic Thin‐Film Transistors
           with π‐Junction Gold Nanoparticles
    • Authors: Takeo Minari; Yuki Kanehara, Chuan Liu, Kenji Sakamoto, Takeshi Yasuda, Asuka Yaguchi, Shigemi Tsukada, Kei Kashizaki, Masayuki Kanehara
      Pages: 4886 - 4892
      Abstract: Printing semiconductor devices under ambient atmospheric conditions is a promising method for the large‐area, low‐cost fabrication of flexible electronic products. However, processes conducted at temperatures greater than 150 °C are typically used for printed electronics, which prevents the use of common flexible substrates because of the distortion caused by heat. The present report describes a method for the room‐temperature printing of electronics, which allows thin‐film electronic devices to be printed at room temperature without the application of heat. The development of π‐junction gold nanoparticles as the electrode material permits the room‐temperature deposition of a conductive metal layer. Room‐temperature patterning methods are also developed for the Au ink electrodes and an active organic semiconductor layer, which enables the fabrication of organic thin‐film transistors through room‐temperature printing. The transistor devices printed at room temperature exhibit average field‐effect mobilities of 7.9 and 2.5 cm2 V−1 s−1 on plastic and paper substrates, respectively. These results suggest that this fabrication method is very promising as a core technology for low‐cost and high‐performance printed electronics. Room‐temperature printed electronics are realized as a low‐cost, large‐area fabrication method for flexible electronic devices. Development of a π‐junction gold nanoparticle ink enables the formation of fully printed organic thin‐film transistors under atmospheric conditions at room temperature. The printed transistor devices exhibit average field‐effect mobilities of 7.9 and 2.5 cm2 V−1 s−1 on plastic and paper substrates, respectively.
      PubDate: 2014-05-09T02:58:53.205681-05:
      DOI: 10.1002/adfm.201400169
       
  • Synergistic Computational‐Experimental Approach to Improve Ionene
           Polymer‐Based Functional Hydrogels
    • Authors: Jürgen Bachl; David Zanuy, Daniel E. López‐Pérez, Guillermo Revilla‐López, Carlos Cativiela, Carlos Alemán, David Díaz Díaz
      Pages: 4893 - 4904
      Abstract: The manifold applications of ionene‐based materials such as hydrogels in daily life, biomedical sciences, and industrial processes are a consequence of their unique physical and chemical properties, which are governed by a judicious balance between multiple non‐covalent interactions. However, one of the most critical aspects identified for a broader use of different polyelectrolytes is the need of raising their gelation efficiency. This work focuses on surfactant‐free ionene polymers 1−3 containing DABCO and N,N′‐(x‐phenylene)dibenzamide (x = ortho‐/meta‐/para‐) linkages as model systems to develop a combined computational‐experimental approach to improve the hydrogelation through a better understanding of the gelation mechanism. Molecular dynamics simulations of isomeric ionenes 1–3 with explicit water molecules point out remarkable differences in the assembly of the polymeric chains in each case. Interchain regions with high degree of hydration (i.e., polymer···water interactions) and zones dominated by polymer···polymer interactions are evident in the case of ortho‐ (1) and meta‐ (2) isomeric ionenes, whereas domains controlled by polymer···polymer interactions are practically inexistent in 3. In excellent agreement, ortho‐ionene 1 provides experimentally the best hydrogels with unique features such as thixotropic behavior and dispersion ability for single‐walles carbon nanotubes. A combined computational‐experimental approach identifies the topological constraints necessary to enhance gelation efficiency and achieve superior properties of hydrogels made from DABCO‐containing ionene polymers. The best performance of studied ionenes is established based on the critical gelation concentration, gelation kinetics, thermal and mechanical stability, optical properties, and dispersion ability for single‐walled carbon nanotubes.
      PubDate: 2014-04-28T00:48:57.044966-05:
      DOI: 10.1002/adfm.201304230
       
  • Three‐Dimensional Printing of Elastomeric, Cellular Architectures
           with Negative Stiffness
    • Authors: Eric B. Duoss; Todd H. Weisgraber, Keith Hearon, Cheng Zhu, Ward Small, Thomas R. Metz, John J. Vericella, Holly D. Barth, Joshua D. Kuntz, Robert S. Maxwell, Christopher M. Spadaccini, Thomas S. Wilson
      Pages: 4905 - 4913
      Abstract: Three‐dimensional printing of viscoelastic inks to create porous, elastomeric architectures with mechanical properties governed by the ordered arrangement of their sub‐millimeter struts is reported. Two layouts are patterned, one resembling a “simple cubic” (SC)‐like structure and another akin to a “face‐centered tetragonal” (FCT) configuration. These structures exhibit markedly distinct load response with directionally dependent behavior, including negative stiffness. More broadly, these findings suggest the ability to independently tailor mechanical response in cellular solids via micro‐architected design. Such ordered materials may one day replace random foams in mechanical energy absorption applications. Three‐dimensional printing of viscoelastic inks to create porous, elastomeric architectures with mechanical properties governed by the ordered arrangement of their sub‐millimeter struts, is reported. Two layouts are patterned, one resembling a “simple cubic”‐like structure and another akin to a “face‐centered tetragonal” configuration. These mechanical metamaterials exhibit markedly distinct load response with directionally dependent behavior, including negative shear stiffness.
      PubDate: 2014-05-02T01:36:03.48644-05:0
      DOI: 10.1002/adfm.201400451
       
  • Graphene Oxide: Ultrafast Fabrication of Covalently Cross‐linked
           Multifunctional Graphene Oxide Monoliths (Adv. Funct. Mater. 31/2014)
    • Authors: Wubo Wan; Lingli Li, Zongbin Zhao, Han Hu, Xiaojuan Hao, David A. Winkler, Lingcong Xi, Timothy C. Hughes, Jieshan Qiu
      Pages: 4914 - 4914
      Abstract: A rapid and facile technique to fabricate 3D graphene oxide monoliths (GOMs) by covalently cross‐linking GO sheets with a poly(oxypropylene) diamine is demonstrated on page 4915 by T. C. Hughes, J. S. Qiu, and co‐workers in a collaboration between Dalian University of Technology, China, and CSIRO, Australia. The GOMs behave like an elastic hydrogel and can be molded into functional materials with many desired shapes for diverse applications, for example, for water treatment and for biomedical uses.
      PubDate: 2014-08-14T07:12:33.338429-05:
      DOI: 10.1002/adfm.201470208
       
  • Ultrafast Fabrication of Covalently Cross‐linked Multifunctional
           Graphene Oxide Monoliths
    • Authors: Wubo Wan; Lingli Li, Zongbin Zhao, Han Hu, Xiaojuan Hao, David A. Winkler, Lingcong Xi, Timothy C. Hughes, Jieshan Qiu
      Pages: 4915 - 4921
      Abstract: Stable graphene oxide monoliths (GOMs) have been fabricated by exploiting epoxy groups on the surface of graphene oxide (GO) in a ring opening reaction with amine groups of poly(oxypropylene) diamines (D400). This method can rapidly form covalently bonded GOM with D400 within 60 s. FTIR and XPS analyses confirm the formation of covalent C‐N bonds. Investigation of the GOM formation mechanism reveals that the interaction of GO with a diamine cross‐linker can result in 3 different GO assemblies depending on the ratio of D400 to GO, which have been proven both by experiment and molecular dynamics calculations. Moreover, XRD results indicate that the interspacial distance between GO sheets can be tuned by varying the diamine chain length and concentration. We demonstrate that the resulting GOM can be moulded into various shapes and behaves like an elastic hydrogel. The fabricated GOM is non‐cyctotoxic to L929 cell lines indicating a potential for biomedical applications. It could also be readily converted to graphene monolith upon thermal treatment. This new rapid and facile method to prepare covalently cross‐linked GOM may open the door to the synthesis and application of next generation multifunctional 3D graphene structures. An ultrafast cross‐linking method for the fabrication of graphene oxide monoliths (GOM) with poly(oxypropylene) diamines as a cross‐linker is reported. This method can form self‐assembled 3D GO structures with controllable interlayer spacing. The covalently bonded GOM structure demonstrates high cell viability, could be molded into various shapes, and when hydrated behaves like an elastic hydrogel.
      PubDate: 2014-04-23T05:54:26.2225-05:00
      DOI: 10.1002/adfm.201303815
       
  • Digital Plasmonic Patterning for Localized Tuning of Hydrogel Stiffness
    • Authors: Kolin C. Hribar; Yu Suk Choi, Matthew Ondeck, Adam J. Engler, Shaochen Chen
      Pages: 4922 - 4926
      Abstract: The mechanical properties of the extracellular matrix (ECM) can dictate cell fate in biological systems. In tissue engineering, varying the stiffness of hydrogels—water‐swollen polymeric networks that act as ECM substrates—has previously been demonstrated to control cell migration, proliferation, and differentiation. Here, “digital plasmonic patterning” (DPP) is developed to mechanically alter a hydrogel encapsulated with gold nanorods using a near‐infrared laser, according to a digital (computer‐generated) pattern. DPP can provide orders of magnitude changes in stiffness, and can be tuned by laser intensity and speed of writing. In vitro cellular experiments using A7R5 smooth muscle cells confirm cell migration and alignment according to these patterns, making DPP a useful technique for mechanically patterning hydrogels for various biomedical applications. Digital plasmonic patterning (DPP) is developed to mechanically pattern a hydrogel encapsulated with gold nanorods in a digital fashion. DPP can provide orders of magnitude changes in the hydrogel stiffness, and can be tuned by laser intensity and writing speed, in addition to any digital pattern, making it a potentially useful technique for patterning hydrogels for various biomedical applications.
      PubDate: 2014-04-28T06:27:34.530119-05:
      DOI: 10.1002/adfm.201400274
       
  • High Precision, Electrochemical Detection of Reversible Binding of
           Recombinant Proteins on Wide Bandgap GaN Electrodes Functionalized with
           Biomembrane Models
    • Authors: Nataliya Frenkel; Jens Wallys, Sara Lippert, Jörg Teubert, Stefan Kaufmann, Aparna Das, Eva Monroy, Martin Eickhoff, Motomu Tanaka
      Pages: 4927 - 4934
      Abstract: We report a novel hybrid charge sensor realized by the deposition of phospholipid monolayers on highly doped n‐GaN electrodes. To detect the binding of recombinant proteins with histidine‐tags, lipid vesicles containing chelator lipids were deposited on GaN electrodes pre‐coated with octadecyltrimethoxysilane monolayers. Owing to its optical transparency, GaN allows the confirmation of the fluidity of supported membranes by fluorescence recovery after photo‐bleaching (FRAP). The electrolyte‐(organic) insulator‐semiconductor (EIS) setup enables one to transduce variations in the surface charge density ΔQ into a change in the interface capacitance ΔC p and, thus, the flat‐band potential ΔU FB. The obtained results demonstrate that the membrane‐based charge sensor can reach a high sensitivity to detect reversible changes in the surface charge density on the membranes by the formation of chelator complexes, docking of eGFP with histidine tags, and cancellation by EDTA. The achievable resolution of ΔQ ≥ 0.1 μC/cm2 is better than that obtained for membrane‐functionalized p‐GaAs, 0.9 μC/cm2, and for ITO coated with a polymer supported lipid monolayer, 2.2 μC/cm2. Moreover, we examined the potential application of optically active InGaN/GaN quantum dot structures, for the detection of changes in the surface potential from the photoluminescence signals measured at room temperature. Hybrid materials based on wide bandgap GaN and cell membrane models can be operated as an electrochemical charge sensor, which sensitively detects changes in the surface potentials caused by the reversible docking of recombinant proteins to the lipid anchors. By transferring such constructs on quantum dot structures, the potential changes can also be detected by their photoluminescence intensity.
      PubDate: 2014-05-13T09:44:08.069119-05:
      DOI: 10.1002/adfm.201400388
       
  • Harnessing Multiple Folding Mechanisms in Soft Periodic Structures for
           Tunable Control of Elastic Waves
    • Authors: Sicong Shan; Sung H. Kang, Pai Wang, Cangyu Qu, Samuel Shian, Elizabeth R. Chen, Katia Bertoldi
      Pages: 4935 - 4942
      Abstract: Mechanical instabilities in periodic porous elastic structures may lead to the formation of homogeneous patterns, opening avenues for a wide range of applications that are related to the geometry of the system. This study focuses on an elastomeric porous structure comprising a triangular array of circular holes, and shows that by controlling the loading direction, multiple pattern transformations can be induced by buckling. Interestingly, these different pattern transformations can be exploited to design materials with highly tunable properties. In particular, these results indicate that they can be effectively used to tune the propagation of elastic waves in phononic crystals, enhancing the tunability of the dynamic response of the system. Using a combination of finite element simulations and experiments, a proof‐of‐concept of the novel material is demonstrated. Since the proposed mechanism is induced by elastic instability, it is reversible, repeatable, and scale‐independent, opening avenues for the design of highly tunable materials and devices over a wide range of length scales. By controlling the loading direction, multiple pattern transformations can be induced by buckling in a triangular array of circular holes embedded in an elastic material. Interestingly, these different pattern transformations can be exploited to tune the propagation of elastic waves in the system, enhancing the tunability of its dynamic response.
      PubDate: 2014-05-19T01:35:06.307597-05:
      DOI: 10.1002/adfm.201400665
       
  • Polymorphism in Crystalline Microfibers of Achiral Octithiophene: The
           Effect on Charge Transport, Supramolecular Chirality and Optical
           Properties
    • Authors: Francesca Di Maria; Eduardo Fabiano, Denis Gentili, Mariano Biasiucci, Tommaso Salzillo, Giacomo Bergamini, Massimo Gazzano, Alberto Zanelli, Aldo Brillante, Massimiliano Cavallini, Fabio Della Sala, Giuseppe Gigli, Giovanna Barbarella
      Pages: 4943 - 4951
      Abstract: Polymorphic crystalline microfibers from an achiral octithiophene with one S‐hexyl substituent per ring are separately and reproducibly grown with the same characteristics on various solid surfaces, including the interdigitated electrodes/SiO2 surface of a bottomcontact field‐effect transistor. The arrangement of the same molecule in two diverse supramolecular structures leads to markedly different electronic, optical, and charge mobility properties. The microfibers—straight and yellow emitting or helical and red emitting—exhibit p‐type charge transport characteristics, with the yellow ones showing a charge mobility and on/off current ratio of one and three orders of magnitude, respectively, greater than the red ones. Both forms show circular dichroism signals with significant differences from one form to the other. DFT calculations show that the octithiophene exists in two different quasi‐equienergetic conformations aggregating with diverse orientations of the substituents. This result suggests that the observed polymorphism is conformational in nature. The self‐assembly, driven by sulfur–sulfur non‐bonding interactions, amplifies the small property differences between conformers, leading to quite different bulk properties. A sulfur overrich octithiophene forms stable polymorfic crystalline microfibers separately and reproducibly grown on glass, ITO, and an interdigitated electrode/SiO2 surface of a bottom‐contact field‐effect transistor. The effects of polymorphism on functional properties are reported. DFT calculations suggest the polymorphism to be conformational in nature.
      PubDate: 2014-05-22T03:20:25.187765-05:
      DOI: 10.1002/adfm.201400534
       
  • In Situ Electrical Characterization of Anatase TiO2 Quantum Dots
    • Authors: Johanna Engel; Sean R. Bishop, Lionel Vayssieres, Harry L. Tuller
      Pages: 4952 - 4958
      Abstract: A novel method for performing in situ characterization of the electrical properties of pristine, ultrafine nanopowders is reported. A modified dilatometer, with a spring‐loaded push rod and electrodes, allows for the simultaneous monitoring of the packed nanopowder's lateral displacement as well as its complex impedance spectroscopy as a function of temperature within a controlled environment. Anatase TiO2 quantum dots of 2 nm diameter, on average, are examined and found to simultaneously shrink and become more resistive upon initial heating. The resistance changes by approximately 3 orders of magnitude upon heating, associated with the desorption of adsorbed water, demonstrating the need for sample preconditioning. Subsequent electrical resistivity measurements, as a function of oxygen partial pressure, over approximately 40 orders of magnitude, at temperatures between 300 °C and 400 °C, exhibit nearly 9 orders of magnitude change in conductivity. The data are consistent with a Frenkel‐based defect disorder model characterized by an enthalpy of reduction of 5.5 ± 0.5 eV. Anatase TiO2 quantum dots exhibit a Frenkel defect disorder when characterized as loose powder in a modified dilatometer setup, which allows electrical impedance spectroscopy measurements. In addition, lateral expansion indicates necessity of preconditioning to attain equilibrium electronic parameters by eliminating protonic conduction on the surface of the quantum dots.
      PubDate: 2014-05-23T05:59:36.102007-05:
      DOI: 10.1002/adfm.201400203
       
  • Aligned Polythiophene and its Blend Film by Direct‐Writing for
           Anisotropic Charge Transport
    • Authors: Guanghao Lu; Jiayue Chen, Wentao Xu, Sijun Li, Xiaoniu Yang
      Pages: 4959 - 4968
      Abstract: A combination of patterning and film alignment techniques helps to build multi‐order polymer architecture for application in flexible electronics. A direct‐writing method is employed using microcapillary arrays to prepare semiconducting polymer films with both optical and electrical anisotropy. Not only aligned poly(3‐butylthiophene) (P3BT) nanowires in neat P3BT films, but also aligned P3BT nanowires within a polystyrene (PS) matrix are obtained, which yields an aligned semiconductor/insulator polymer blend with anisotropic charge transport. The field‐effect transistor (FET) mobilities/threshold voltages from both vertical and parallel to alignment directions as well as their dependence on blending ratio are studied. The increased mobility of P3BT/PS blends, as compared with neat P3BT, is observed in both vertical and parallel directions. Using this alignment method, FET mobility and threshold voltage of the semiconductor/insulator polymer blends are comprehensively tuned, from which a digital inverter with gain up to 80 is realized. Therefore, this work not only helps understanding the charge transport mechanism in semiconducting/insulating polymer blends, but also provides an effective approach towards high‐performance field‐effect transistors with tunable mobility and threshold voltage. A direct‐writing method is used to prepare aligned semiconducting poly(3‐butylthiophene) (P3BT) and its blend films with both optical and electrical anisotropy. An increased field‐effect mobility of aligned P3BT/polystyrene blends, as compared with neat P3BT, is observed in both vertical and parallel directions. The mobility and threshold voltage are comprehensively tuned, from which a digital inverter with gain up to 80 is realized.
      PubDate: 2014-05-22T03:20:33.071122-05:
      DOI: 10.1002/adfm.201400699
       
  • Macroscopic Properties of Restacked, Redox‐Liquid Exfoliated
           Graphite and Graphite Mimics Produced in Bulk Quantities
    • Authors: Vikram K. Srivastava; Ronald A. Quinlan, Alexander L. Agapov, John R. Dunlap, Kimberly M. Nelson, Edward Duranty, Alexei P. Sokolov, Gajanan S. Bhat, Jimmy W. Mays
      Pages: 4969 - 4977
      Abstract: The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox‐liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfide, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS2 sonicated with the antioxidant sodium bisulfite, results from Raman spectroscopy, X‐ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS2, upon thermal treatment up to 900 °C. The addition of the ionic antioxidant decreased dispersion stability in non‐polar solvent, suggesting decreased compatibility with non‐polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium–ion capacitors, and chemical sensing. Restacked, layered compounds of graphite, molybdenum disulfide, and boron nitride are ideal materials for electronic devices, censors, and reinforced materials. A high‐yielding process using sonochemical fragmentation of precursor powders with antioxidants is performed to generate modified restacked materials. The restacked powders demonstrate unique chemical, thermal, dispersive, and electrical properties that are desirable for polymer composites and other hybrid materials.
      PubDate: 2014-05-23T06:05:44.793045-05:
      DOI: 10.1002/adfm.201400484
       
  • Defect‐Minimized PEDOT:PSS/Planar‐Si Solar Cell with Very High
           Efficiency
    • Authors: Joseph Palathinkal Thomas; Kam Tong Leung
      Pages: 4978 - 4985
      Abstract: Hybrid solar cells made of a p‐type conducting polymer, poly(3,4‐ethyl thiophene):polystyrenesulfonate (PEDOT:PSS), on Si have gained considerable interest in the fabrication of cost‐effective high‐efficiency devices. However, most of the high power conversion efficiency (PCE) performances have been obtained from solar cells fabricated on surface‐structured Si substrates. High‐performance planar single‐junction solar cells have considerable advantages in terms of processing and cost, because they do not require the complex surface texturing processes. The interface of single‐junction solar cells can critically influence the performance. Here, we demonstrate the effect of adding different surfactants in a co‐solvent‐optimized PEDOT:PSS polymer, which, in addition to acting as a p‐layer and as an anti‐reflective coating, also enhances the device performance of a hybrid planar‐Si solar cell. Using time‐of‐flight secondary ion mass spectrometry, we conduct three‐dimensional chemical imaging of the interface, which enables us to characterize the micropore defects found to limit the PCE. Upon minimizing these micropore defects with the addition of optimized amounts of fluorosurfactant and co‐solvent, we achieve a PEDOT:PSS/planar‐Si cell with a record high PCE of 13.3% for the first time. Our present approach of micropore defect reduction can also be used to improve the performance of other organic electronic devices based on PEDOT:PSS. Interface properties of planar hybrid solar cells, PEDOT:PSS/SiOx/Si, are influenced by the amount of surfactant and co‐solvent in PEDOT:PSS. The three‐dimensional time‐of‐flight secondary ion mass spectrometry chemical images reveal a minimal‐defect interface for the high efficiency cells, in comparison with more micropore defects at the interface for low efficiency devices. A very high PCE of 13.3% is achieved under optimized conditions.
      PubDate: 2014-05-26T03:05:36.457099-05:
      DOI: 10.1002/adfm.201400380
       
  • Self‐Healing Reduced Graphene Oxide Films by Supersonic Kinetic
           Spraying
    • Authors: Do‐Yeon Kim; Suman Sinha‐Ray, Jung‐Jae Park, Jong‐Gun Lee, You‐Hong Cha, Sang‐Hoon Bae, Jong‐Hyun Ahn, Yong Chae Jung, Soo Min Kim, Alexander L. Yarin, Sam S. Yoon
      Pages: 4986 - 4995
      Abstract: The industrial scale application of graphene and other functional materials in the field of electronics has been limited by inherent defects, and the lack of simple deposition methods. A simple spray deposition method is developed that uses a supersonic air jet for a commercially available reduced graphene oxide (r‐GO) suspension. The r‐GO flakes are used as received, which are pre‐annealed and pre‐hydrazine‐treated, and do not undergo any post‐treatment. A part of the considerable kinetic energy of the r‐GO flakes entrained by the supersonic jet is used in stretching the flakes upon impact with the substrate. The resulting “frozen elastic strains” heal the defects (topological defects, namely Stone‐Wales defect and C2 vacancies) in the r‐GO flakes, which is reflected in the reduced ratio of the intensities of the D and G bands in the deposited film. The defects can also be regenerated by annealing. Deposition of r‐graphene oxide (r‐GO) onto a glass slide. r‐GO sheets stretch upon impact. Pentagonal and heptagonal r‐GO sheets undergo bond translation. The resulting “frozen elastic strains” heal the defects (topological defects, namely Stone‐Wales and C2 vacancies) in the r‐GO flakes, which is reflected in the reduced ratio of the intensities of the D and G bands in the deposited film.
      PubDate: 2014-05-26T12:30:26.947749-05:
      DOI: 10.1002/adfm.201400732
       
  • A Catalytic and Shape‐Memory Polymer Reactor
    • Authors: Yanli Han; Xinhua Yuan, Maiyong Zhu, Songjun Li, Michael J. Whitcombe, Sergey A. Piletsky
      Pages: 4996 - 5001
      Abstract: An originally designed catalytic and shape‐memory polymer reactor is reported. This reactor is made of a unique shape‐switchable polymer composed of a thermosensitive control layer and an inert substrate layer. With the inert substrate layer made of poly(acrylamide), the thermosensitive control layer consists of nickel nanoparticles and a smart polymer composite of poly(1‐vinylimidazole) (PVIm) and poly(acrylic acid) (PAAc) that exhibit switchable domains. The self‐healing and dissociation between PVIm and PAAc induce convex/concave‐switchable shapes in the resulting reactor, which cause tunable access to the encapsulated metal nanoparticles. In this way, this reactor demonstrates tunable catalytic ability. Unlike reported smart polymer reactors exhibiting tunable catalysis usually due to the thermal phase transition of poly(N‐isopropylacrylamide) (PNIPAm), this novel reactor adopts the shape‐switchable strategy for tunable catalysis. This novel design suggests a new protocol for the development of smart catalytic reactors, which opens new opportunities for controlled chemical processes. An originally designed polymer reactor composed of a thermosensitive control layer and an inert substrate layer is reported. With the inert substrate layer made of poly(acrylamide), the thermosensitive control layer consists of nickel nanoparticles and a unique polymer composite of poly(1‐vinylimidazole) and poly(acrylic acid) that exhibit thermosensitive interactions. The self‐healing and dissociation of the thermosensitive interactions induce convex/concave‐switchable shapes in the resulting reactor, which cause tunable access to the encapsulated metal nanoparticles. In this way, this reactor demonstrates tunable catalytic ability.
      PubDate: 2014-05-23T05:59:41.590715-05:
      DOI: 10.1002/adfm.201400768
       
  • Efficient Directed Energy Transfer through Size‐Gradient Nanocrystal
           Layers into Silicon Substrates
    • Authors: William J. I. De Benedetti; Michael T. Nimmo, Sara M. Rupich, Louis M. Caillard, Yuri N. Gartstein, Yves J. Chabal, Anton V. Malko
      Pages: 5002 - 5010
      Abstract: Spectroscopic evidence of directed excitonic energy transfer (ET) is presented through size‐gradient CdSe/ZnS nanocrystal quantum dot (NQD) layers into an underlying Si substrate. NQD monolayers are chemically grafted on hydrogen‐terminated Si surfaces via a self‐assembled monolayer of amine modified carboxy‐alkyl chains. Subsequent NQD monolayers are linked with short alkyldiamines. The linking approach enables accurate positioning and enhanced passivation of the layers. Two different sizes of NQDs (energy donors emitting at 545 nm, and energy acceptors emitting at 585 nm) are used in comparing different monolayer and bilayer samples grafted on SiO2 and oxide‐free Si surfaces via time‐resolved photoluminescence measurements. The overall efficiency of ET from the top‐layer donor NQDs into Si is estimated to approach ≈90% through a combination of different energy relaxation pathways. These include sequential ET through the intermediate acceptor layer realized mainly via the non‐radiative mechanism and direct ET into the Si substrate realized by means of the radiative coupling. The experimental observations are quantitatively rationalized by the theoretical modeling without introducing any extraneous energy scavenging processes. This indicates that the linker‐assisted fabrication enables the construction of defect‐free, bandgap‐gradient multilayer NQD/Si hybrid structures suitable for thin‐film photovoltaic applications. Size‐gradient CdSe/ZnS nanocrystal bilayer structures are fabricated on Si substrates in a layer‐by‐layer architecture with assistance of chemical linkers. Efficient energy transfer is demonstrated from photoexcited nanocrystals into the substrate as achieved via cascaded non‐radiative and direct radiative couplings. This supports the concept of excitonic sensitization of ultrathin Si layers from the adjacent nanocrystal assemblies for photovoltaic applications.
      PubDate: 2014-05-26T03:05:40.550762-05:
      DOI: 10.1002/adfm.201400667
       
  • Bio‐Inspired Preparation of Fibrin‐Boned Bionanocomposites of
           Biomacromolecules and Nanomaterials for Biosensing
    • Authors: Fangfang Han; Xin Qi, Lingyan Li, Lijuan Bu, Yingchun Fu, Qingji Xie, Manli Guo, Yanbin Li, Yibin Ying, Shouzhuo Yao
      Pages: 5011 - 5018
      Abstract: Learning from nature is one of the most promising ways to develop advanced functional materials. Here, inspired by blood coagulation, novel fibrin‐boned bionanocomposites are reported as efficient immobilization matrices of biomacromolecules and nanomaterials for biosensing. Glucose oxidase (GOx), Au nanoparticles (AuNPs), and Fe3O4 magnetic nanoparticles (MNPs) are adopted as the model biomacromolecules and nanomaterials. By integrating the thrombin‐triggered coagulation of fibrin with advanced surficial modification techniques, four kinds of immobilization strategies are developed and evaluated. Digital imaging, UV‐vis spectroscopy, scanning/transmission electron microscopy, electrochemical methods, and N2 adsorption‐desorption isotherms are used to investigate the formation, immobilization efficiency, and performance of various bionanocomposites. The fibrin‐boned networks show inherent biocompatibility, excellent adsorbability, porosity, and functionalization ability, endowing the bionanocomposites with high efficiencies in capturing AuNPs, MNPs and GOx (99%, 98%, and 57% captured under the given conditions, respectively), as well as significant mass‐transfer and biocatalysis efficiencies. Therefore, the fibrin‐boned bionanocomposites show great potential for biosensing, for example, a fibrin‐AuNPs‐GOx‐glutaraldehyde bionanocomposites modified Au electrode is highly sensitive to glucose (145 μA cm−2 mM−1) allowing for a limit of detection down to 25 nM, being much superior to those of the reported analogues. The presented experimental platform/strategy may find wide applications in the development of other bio/nano‐materials/devices. Inspired by blood coagulation, fibrin‐boned bionanocomposites are presented as efficient matrices of biomacromolecules and nanomaterials for biosensing applications. The fibrin‐boned networks show promising properties, endowing the bionanocomposites with high efficiency in capturing Au nanoparticles, magnetic nanoparticles, and glucose oxidase, even at 99%, 98%, and 57%, respectively, as well as significant mass‐transfer and biocatalysis efficiencies.
      PubDate: 2014-05-26T03:05:38.655155-05:
      DOI: 10.1002/adfm.201400458
       
  • Cellular Solids: Three‐Dimensional Printing of Elastomeric, Cellular
           Architectures with Negative Stiffness (Adv. Funct. Mater. 31/2014)
    • Authors: Eric B. Duoss; Todd H. Weisgraber, Keith Hearon, Cheng Zhu, Ward Small, Thomas R. Metz, John J. Vericella, Holly D. Barth, Joshua D. Kuntz, Robert S. Maxwell, Christopher M. Spadaccini, Thomas S. Wilson
      Pages: 5020 - 5020
      Abstract: Three‐dimensional printing of viscoelastic inks is demonstrated by E. B. Duoss, C. M. Spadaccini, T. S. Wilson, and co‐workers on page 4905. This technique is shown to create porous, elastomeric architectures with highly controlled mechanical properties, exhibiting markedly distinct load responses with directionally dependent behavior, including negative shear stiffness.
      PubDate: 2014-08-14T07:12:35.621947-05:
      DOI: 10.1002/adfm.201470210
       
 
 
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