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CHEMISTRY (532 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 1)
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: 8)
ACS Macro Letters     Full-text available via subscription   (Followers: 17)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 25)
ACS Nano     Full-text available via subscription   (Followers: 248)
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: 10)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 4)
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: 28)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 148)
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: 35)
Angewandte Chemie     Hybrid Journal   (Followers: 15)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 201)
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: 186)
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: 13)
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: 37)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
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
   Journal TOC RSS feeds Export to Zotero [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  [1604 journals]   [SJR: 4.862]   [H-I: 136]
  • Pd‐Cu Bimetallic Tripods: A Mechanistic Understanding of the
           Synthesis and Their Enhanced Electrocatalytic Activity for Formic Acid
    • Authors: Lei Zhang; Sang‐Il Choi, Jing Tao, Hsin‐Chieh Peng, Shuifen Xie, Yimei Zhu, Zhaoxiong Xie, Younan Xia
      Pages: n/a - n/a
      Abstract: This article reports a facile synthesis of Pd‐Cu bimetallic tripods with a purity over 90%. Two requirements must be met in order to form tripods: i) formation of triangular, plate‐like seeds during the nucleation step and ii) preferential deposition of atoms onto the three corners of a seed during the growth step. In this synthesis, these requirements are fulfilled by adding CuCl2 and KBr into an aqueous synthesis. Specifically, it is demonstrated that the Cu atoms resulting from underpotential deposition could greatly reduce the energy barrier involved in the formation of triangular seeds with planar defects because of the much lower stacking fault energy (41 mJ·m−2 for Cu vs 220 mJ·m−2 for Pd). The Br− ions could strongly bind to the three {100} side faces of a triangular seed, forcing the Pd atoms to grow from the three corners of a seed to generate a tripod. When compared with commercial Pd black, the Pd‐Cu tripods exhibited substantially enhanced catalytic activity toward the electro‐oxidation of formic acid. This work offers a general strategy for the synthesis of nanocrystals with a tripod structure for catalytic applications. Pd‐Cu bimetallic tripods are prepared by adding CuCl2 and KBr into an aqueous synthesis that involves the reduction of a salt precursor by ascorbic acid. When compared with commercial Pd black, the Pd‐Cu tripods exhibit substantially enhanced (almost eight folds per unit mass of Pd) catalytic activity toward the electro‐oxidation of formic acid.
      PubDate: 2014-09-16T12:25:08.109714-05:
      DOI: 10.1002/adfm.201402350
  • Highly Conductive Microfiber of Graphene Oxide Templated Carbonization of
           Nanofibrillated Cellulose
    • Authors: Yuanyuan Li; Hongli Zhu, Fei Shen, Jiayu Wan, Xiaogang Han, Jiaqi Dai, Hongqi Dai, Liangbing Hu
      Pages: n/a - n/a
      Abstract: Microfibers with conductivity of 649 ± 60 S/cm are introduced through a carbonization of well‐aligned graphene oxide (GO) – nanofibrillated cellulose (NFC) hybrid fibers. GO acts as a template for NFC carbonization, which changes the morphology of carbonized NFC from microspheres to sheets while improving the carbonization of NFC. Meanwhile, the carbonized NFC repairs the defects of reduced GO (rGO) and links rGO sheets together. The GO templated carbonization of NFC as well as the alignment of the building blocks along the fiber direction leads to excellent conductivity. Conductive microfibers are evaluated as lithium ion battery anodes, which can be applied in wearable electronics. This approach to make conductive microfibers and the low cost raw materials used in this work may be applied to other carbon based conductive structures. Highly conductive microfibers are designed and fabricated with graphene oxide (GO) and nanofibrillated cellulose (NFC). The alignment of GO flakes and the templated carbonization of NFC leads to high electrical conductivity of ca. 650 S/cm.
      PubDate: 2014-09-16T01:59:28.797192-05:
      DOI: 10.1002/adfm.201402129
  • Stepped Moduli in Layered Composites
    • Authors: Ju‐Hee So; Alok S. Tayi, Firat Güder, George M. Whitesides
      Pages: n/a - n/a
      Abstract: This paper describes adaptive composites that respond to mechanical stimuli by changing their Young's modulus. These composites are fabricated by combining a shorter layer of elastic material (e.g., latex) and a longer layer of stiffer material (e.g., polyethylene and Kevlar), and fixing them together at their ends. Tension along the layered composite increases its length, and as the strain increases, the composite changes the load‐bearing layer from the elastic to the stiff material. The result is a step in the Young's modulus of the composite. The characteristics of the step (or steps) can be engineered by changing the constituent materials, the number of layers, and their geometries (e.g., sinusoidal, hierarchical, two‐dimensional web‐like, rod‐coil, embedded, and ring structures). For composites with more than two steps in modulus, the materials within the composites can be layered in a hierarchical structure to fit within a smaller volume, without sacrificing performance. These composites can also be used to make structures with tunable, stepped compressive moduli. An adaptation of these principles can generate an electronic sensor that can monitor the applied compressive strain. Increasing or decreasing the strain closes or opens a circuit and reversibly activates a light‐emitting diode. Adaptive Young's moduli of composites are demonstrated by combining different materials and controlling their geometries. As applied strain increases, the critical component that dictates the mechanical strength of the composite shifts from an elastic material to a stiff material, resulting in discrete steps in increasing moduli. The characteristics of the steps can be engineered to accommodate specific requirements of applications.
      PubDate: 2014-09-16T01:59:25.095635-05:
      DOI: 10.1002/adfm.201401548
  • Distinguishing the Importance of Fullerene Phase Separation from Polymer
           Ordering in the Performance of Low Band Gap Polymer:Bis‐Fullerene
    • Authors: Huipeng Chen; Yu‐Che Hsiao, Jihua Chen, Bin Hu, Mark Dadmun
      Pages: n/a - n/a
      Abstract: One way to improve power conversion efficiency (PCE) of polymer based bulk‐heterojunction (BHJ) photovoltaic cells is to increase the open circuit voltage (V oc). Replacing PCBM with bis‐adduct fullerenes significantly improves V oc and the PCE in devices based on the conjugated polymer poly(3‐hexyl thiophene) (P3HT). However, for the most promising low band‐gap polymer (LBP) system, replacing PCBM with ICBA results in poor short‐circuit current (J sc) and PCE although V oc is significantly improved. The optimization of the morphology of as‐cast LBP/bis‐fullerene BHJ photovoltaics is attempted by adding a co‐solvent to the polymer/fullerene solution prior to film deposition. Varying the solubility of polymer and fullerene in the co‐solvent, bulk heterojunctions are fabricated with no change of polymer ordering, but with changes in fullerene phase separation. The morphologies of the as‐cast samples are characterized by small angle neutron scattering and neutron reflectometry. A homogenous dispersion of ICBA in LBP is found in the samples where the co‐solvent is selective to the polymer, giving poor device performance. Aggregates of ICBA are formed in samples where the co‐solvent is selective to ICBA. The resultant morphology improves PCE by up to 246%. A quantitative analysis of the neutron data shows that the interfacial area between ICBA aggregates and its surrounding matrix is improved, facilitating charge transport and improving the PCE. The morphology of low band gap polymer:ICBA mixtures is efficiently controlled during film deposition by adding a co‐solvent. A morphology with ICBA phase separation is formed without a change in polymer ordering when a co‐solvent in which ICBA is selectively soluble is used. The resultant morphology improves power conversion efficiency by up to 246%.
      PubDate: 2014-09-16T01:59:22.463649-05:
      DOI: 10.1002/adfm.201401419
  • Theranostic USPIO‐Loaded Microbubbles for Mediating and Monitoring
           Blood‐Brain Barrier Permeation
    • Authors: Twan Lammers; Patrick Koczera, Stanley Fokong, Felix Gremse, Josef Ehling, Michael Vogt, Andrij Pich, Gert Storm, Marc van Zandvoort, Fabian Kiessling
      Pages: n/a - n/a
      Abstract: Efficient and safe drug delivery across the blood‐brain barrier (BBB) remains one of the major challenges of biomedical and (nano‐) pharmaceutical research. Here, it is demonstrated that poly(butyl cyanoacrylate)‐based microbubbles (MB), carrying ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles within their shell, can be used to mediate and monitor BBB permeation. Upon exposure to transcranial ultrasound pulses, USPIO‐MB are destroyed, resulting in acoustic forces inducing vessel permeability. At the same time, USPIO are released from the MB shell, they extravasate across the permeabilized BBB and they accumulate in extravascular brain tissue, thereby providing non‐invasive R 2*‐based magnetic resonance imaging information on the extent of BBB opening. Quantitative changes in R 2* relaxometry are in good agreement with 2D and 3D microscopy results on the extravascular deposition of the macromolecular model drug fluorescein isothiocyanate (FITC)‐dextran into the brain. Such theranostic materials and methods are considered to be useful for mediating and monitoring drug delivery across the BBB and for enabling safe and efficient treatment of CNS disorders. Polymer‐based microbubbles containing ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles within their shell can be used to simultaneously mediate and monitor blood‐brain barrier (BBB) permeation and to enable efficient macromolecular (model) drug delivery into the central nervous system.
      PubDate: 2014-09-16T01:59:19.945772-05:
      DOI: 10.1002/adfm.201401199
  • Light‐Powered Healing of a Wearable Electrical Conductor
    • Authors: Hong Suk Kang; Hee‐Tak Kim, Jung‐Ki Park, Seungwoo Lee
      Pages: n/a - n/a
      Abstract: Mechanical failure along a conductive pathway can cause unexpected shutdown of an electronic devices, ultimately limiting the device lifetime. To address this problem, various systems to realize healable electrical conductors have been proposed; however, rapid, noninvasive, and on‐demand healing, factors that are all synergistically required, especially for wearable device applications, still remains challenging. Here, a light‐powered healable electrical conductor (conceptualized as photofluidic diffusional system) is proposed for simple‐, fast‐, and easy‐to‐implement wearable devices (e.g., the electronic skin, sensitive to mechanical motion). Contrary to other implementations such as capsules, heat, water, and mechanical forces, green light even with low intensity has potential to provide fast (less than 3 min) and repetitive recovery of a damaged electrical conductor without any direct invasion. Also, the multiple, irregular cracks resulting from vigorous motions of wearable devices can be simultaneously recovered regardless of the light incident angles and crack propagation directions, thus, making light‐powered healing more accessible to wearable devices beyond existing system options. To develop and demonstrate the key concepts of this system, combined studies on materials, integrations, and light‐powering strategy for recovering a damaged wearable electrical conductor are systematically carried out in the present work. Light‐powered delivery of silver nanowires can offer a rapid, noninvasive, repetitive, and on‐demand healing of a wearable electrical conductor. To develop the concept, combined studies on materials, integrations, and light‐powering strategy for recovering a damaged wearable electrical conductor are carried out in the present work.
      PubDate: 2014-09-15T06:57:25.812263-05:
      DOI: 10.1002/adfm.201401666
  • Low‐Noise Multispectral Photodetectors Made from All
           Solution‐Processed Inorganic Semiconductors
    • Authors: Jesse R. Manders; Tzung‐Han Lai, Yanbin An, Weikai Xu, Jaewoong Lee, Do Young Kim, Gijs Bosman, Franky So
      Pages: n/a - n/a
      Abstract: Infrared, visible, and multispectral photodetectors are important components for sensing, security and electronics applications. Current fabrication of these devices is based on inorganic materials grown by epitaxial techniques which are not compatible with low‐cost large‐scale processing. Here, air‐stable multispectral solution‐processed inorganic double heterostructure photodetectors, using PbS quantum dots (QDs) as the photoactive layer, colloidal ZnO nanoparticles as the electron transport/hole blocking layer (ETL/HBL), and solution‐derived NiO as the hole transport/electron blocking layer (HTL/EBL) are reported. The resulting device has low dark current density of 20 nA cm‐2 with a noise equivalent power (NEP) on the order of tens of picowatts across the detection spectra and a specific detectivity (D*) value of 1.2 × 1012 cm Hz1/2 W‐1. These parameters are comparable to commercially available Si, Ge, and InGaAs photodetectors. The devices have a linear dynamic range (LDR) over 65 dB and a bandwidth over 35 kHz, which are sufficient for imaging applications. Finally, these solution‐processed inorganic devices have a long storage lifetime in air, even without encapsulation. Air‐stable, all‐solution processed all‐inorganic multispectral photodetectors using PbS quantum dots as the photoactive layer, colloidal ZnO nanoparticles as the electron transport/hole blocking layer, and solution‐derived NiO as the hole transport/electron blocking layer are reported. The resulting devices have very low dark current density with a noise equivalent power on the order of tens of picowatts across the detection spectra. The performance parameters are comparable to commercially available Si, Ge, and InGaAs photodetectors and the device has a long unencapsulated storage lifetime in air.
      PubDate: 2014-09-15T06:57:22.038908-05:
      DOI: 10.1002/adfm.201402094
  • Nanograined Half‐Heusler Semiconductors as Advanced Thermoelectrics:
           An Ab Initio High‐Throughput Statistical Study
    • Authors: Jesús Carrete; Natalio Mingo, Shidong Wang, Stefano Curtarolo
      Pages: n/a - n/a
      Abstract: Nanostructuring has spurred a revival in the field of direct thermoelectric energy conversion. Nanograined materials can now be synthesized with higher figures of merit (ZT) than the bulk counterparts. This leads to increased conversion efficiencies. Despite considerable effort in optimizing the known and discovering the unknown, technology still relies upon a few limited solutions. Here ab initio modeling of ZT is performed for 75 nanograined compounds—the result of accurate distillation with electronic and thermodynamic filtering techniques from the 79 057 half‐Heusler entries available in the repository. For many of the compounds, the ZTs are markedly above those attainable with nanograined IV and III‐V semiconductors. About 15% of them may even outperform ZT ≈ 2 at high temperatures. This analysis elucidates the origin of the advantageous thermoelectric properties found within this broad material class. Machine learning techniques are used to unveil simple rules determining if a nanograined half‐Heusler compound is likely to be a good thermoelectric given its chemical composition. First‐principles calculations are used to model the thermoelectric properties of 75 nanograined compounds obtained after filtering through the 79 057 half‐Heusler entries available in the repository utilizing electronic and thermodynamic criteria. Many of the figures of merit obtained are markedly above those attainable with nanograined IV and III‐V semiconductors, and competitive with the state of the art.
      PubDate: 2014-09-15T06:57:12.617781-05:
      DOI: 10.1002/adfm.201401201
  • Modulating the Properties of Azulene‐Containing Polymers through
           Controlled Incorporation of Regioisomers
    • Authors: Kazuhiko Tsurui; Masahito Murai, Sung‐Yu Ku, Craig J. Hawker, Maxwell J. Robb
      Pages: n/a - n/a
      Abstract: Two libraries of random conjugated polymers are presented that incorporate varying ratios of regioisomeric azulene units connected via the 5‐membered or 7‐membered ring in combination with bithiophene or fluorene comonomers. It is demonstrated that the optoelectronic and stimuli‐responsive properties of the materials can be systematically modulated by tuning the relative percentage of each azulene building block in the polymer backbone. Significantly, these materials exhibit stimuli‐responsive behavior in the solid state with spin‐coated thin films undergoing rapid and reversible color switching. Ultimately, this work introduces a new design strategy in which the optoelectronic properties of conjugated polymers can be modulated by varying only the regiochemistry of the constituent building blocks along a polymer chain. Tuning the percentage of azulene regioisomers in conjugated polymers leads to systematic variation in optoelectronic properties. A new design strategy is demonstrated in which the properties of conjugated polymers can be modulated by simply varying the regiochemistry of the building blocks along the polymer chain. Significantly, these materials exhibit ­stimuli‐responsive behavior in the solid state with thin films undergoing rapid and reversible color switching.
      PubDate: 2014-09-12T10:02:21.137238-05:
      DOI: 10.1002/adfm.201402554
  • A Tunable, Stable, and Bioactive MOF Catalyst for Generating a Localized
           Therapeutic from Endogenous Sources
    • Authors: Jacqueline L. Harding; Jarid M. Metz, Melissa M. Reynolds
      Pages: n/a - n/a
      Abstract: The versatile chemical and physical properties of metal organic frameworks (MOFs) have made them unique platforms for the design of biomimetic catalysts, but with only limited success to date due to instability of the MOFs employed in physiological environments. Herein, the use of Cu(II)1,3,5‐Benzene‐tris‐triazole (CuBTTri) is demonstrated for the catalytic generation of the bioactive agent nitric oxide (NO) from endogenous sources, S‐nitrosothiols (RSNOs). CuBTTri exhibits structural integrity in aqueous environments, including phosphate buffered saline (76 h, pH 7.4, 37 °C), cell media used for in vitro testing (76 h, pH 7.4, 37 °C), and fresh citrated whole blood (30 min, pH 7.4, 37 °C). The application of CuBTTri for use in polymeric medical devices is explored through the formation of a composite CuBTTri‐poly by blending CuBTTri into biomedical grade polyurethane matrices. Once prepared, the CuBTTri‐poly material retains the catalytic function towards the generation of NO with tunable release kinetics proportional to the total content of CuBTTri embedded into the polymeric material with a surface flux corresponding to the therapeutic range of 1–100 nm cm−2 min−1, which is maintained even following exposure to blood. The use of a physiologically stable metal organic framework for the catalytic generation of nitric oxide represents a new frontier in materials designed as biotherapeutics. The incorporation into polymeric materials subsequently results in the development of biomaterials geared towards possessing antifouling properties by the surface elution of the bioactive agent nitric oxide.
      PubDate: 2014-09-12T10:02:16.892823-05:
      DOI: 10.1002/adfm.201402529
  • Flexible Solid‐State Supercapacitor Based on Graphene‐based
           Hybrid Films
    • Authors: Meng Li; Zhe Tang, Mei Leng, Junmin Xue
      Pages: n/a - n/a
      Abstract: A flexible solid‐state asymmetric supercapacitor based on bendable film electrodes with 3D expressway‐like architecture of graphenes and “hard nano‐spacer” is fabricated via an extended filtration assisted method. In the designed structure of the positive electrode, graphene sheets are densely packed, and Ni(OH)2 nanoplates are intercalated in between the densely stacked graphenes. The 3D expressway‐like electrodes exhibit superior supercapacitive performance including high gravimetric capacitance (≈573 F g‐1), high volumetric capacitance (≈655 F cm‐3), excellent rate capability, and superior cycling stability. In addition, another hybrid film of graphene and carbon nanotubes (CNT) is fabricated as the negative electrodes for the designed asymmetric device. In the obtained graphene@CNT films, CNTs served as the hard spacer to prevent restacking of graphene sheets but also as a conductive and robust network to facilitate the electrons collection/transport in order to fulfill the demand of high‐rate performance of the asymmetric supercapacitor. Based on these two hybrid electrode films, a solid‐state flexible asymmetric supercapacitor device is assembled, which is able to deliver competitive volumetric capacitance of 58.5 F cm‐3 and good rate capacity. There is no obvious degradation of the supercapacitor performance when the device is in bending configuration, suggesting the excellent flexibility of the device. The fabrication of a flexible solid‐state asymmetric supercapacitor, based on bendable film electrodes with 3D expressway‐like architecture of graphenes and “hard nano‐spacer” via an extended filtration assisted method, is reported. The 3D expressway‐like electrode exhibits superior supercapacitive performance including high gravimetric capacitance (≈573 F g‐1), high volumetric capacitance (≈655 F cm‐3), excellent rate capability, and superior cycling stability.
      PubDate: 2014-09-12T10:00:13.283238-05:
      DOI: 10.1002/adfm.201402442
  • Ultraviolet‐Light‐Induced Reversible and Stable Carrier
           Modulation in MoS2 Field‐Effect Transistors
    • Authors: Arun Kumar Singh; Shaista Andleeb, Jai Singh, Hoang Tien Dung, Yongho Seo, Jonghwa Eom
      Pages: n/a - n/a
      Abstract: The tuning of charge carrier concentrations in semiconductor is necessary in order to approach high performance of the electronic and optoelectronic devices. It is demonstrated that the charge‐carrier density of single‐layer (SL), bilayer (BL), and few‐layer (FL) MoS2 nanosheets can be finely and reversibly tuned with N2 and O2 gas in the presence of deep‐ultraviolet (DUV) light. After exposure to N2 gas in the presence of DUV light, the threshold voltages of SL, BL, and FL MoS2 field‐effect transistors (FETs) shift towards negative gate voltages. The exposure to N2 gas in the presence of DUV light notably improves the drain‐to‐source current, carrier density, and charge‐carrier mobility for SL, BL, and FL MoS2 FETs. Subsequently, the same devices are exposed to O2 gas in the presence of DUV light for different periods and the electrical characteristics are completely recovered after a certain time. The doping by using the combination of N2 and O2 gas with DUV light provides a stable, effective, and facile approach for improving the performance of MoS2 electronic devices. The charge‐carrier density of single‐, bi‐, and few‐layer MoS2 nanosheets can be finely and reversibly tuned with N2 and O2 gas in the presence of deep‐ultraviolet (DUV) light. The exposure to N2 gas in the presence of DUV light significantly improves the drain‐to‐source current, carrier density, and charge‐carrier mobility for MoS2 nanosheets.
      PubDate: 2014-09-12T09:59:57.704159-05:
      DOI: 10.1002/adfm.201402231
  • Self‐Compensated Insulating ZnO‐Based Piezoelectric
    • Authors: Dohwan Kim; Keun Young Lee, Manoj Kumar Gupta, Subrata Majumder, Sang‐Woo Kim
      Pages: n/a - n/a
      Abstract: Remarkable enhancement of piezoelectric power output from a nanogenerator (NG) based on a zinc oxide (ZnO) thin film is achieved via native defect control. A large number of unintentionally induced point defects that act as n‐type carriers in ZnO have a strong influence on screening the piezoelectric potential into a piezoelectric NG. Here, additional oxygen molecules bombarded into ZnO lead to oxygen‐rich conditions, and the n‐type conductivity of ZnO is decreased dramatically. The acceptor‐type point defects such as zinc vacancies created during the deposition process trap n‐type carriers occurring from donor‐type point defects through a self‐compensation mechanism. This unique insulating‐type ZnO thin film‐based NGs (IZ‐NGs) generates output voltage around 1.5 V that is over ten times higher than that of an n‐type ZnO thin film‐based NG (around 0.1 V). In addition, it is found that the power output performance of the IZ‐NG can be further increased by hybridizing with a p‐type polymer (poly(3‐hexylthiophene‐2,5‐diyl):phenyl‐C61‐butyric acid methyl ester) via surface free carrier neutralization. High performance piezoelectric nanogenerators based on self‐compensated insulating ZnO via native defect control are demonstrated. Self‐compensation of donor and acceptor‐type native defects makes ZnO insulating. Without additional passivation agents, dramatic enhancement of the piezoelectric output performance from the insulating ZnO‐based piezoelectric nanogenerator is observed compared to a donor‐defect‐rich ZnO‐based piezoelectric nanogenerator under the same mechanical strain.
      PubDate: 2014-09-12T09:59:52.61376-05:0
      DOI: 10.1002/adfm.201401998
  • Polyoxometalate‐coupled Graphene via Polymeric Ionic Liquid Linker
           for Supercapacitors
    • Authors: MinHo Yang; Bong Gill Choi, Sung Chul Jung, Young‐Kyu Han, Yun Suk Huh, Sang Bok Lee
      Pages: n/a - n/a
      Abstract: The integration of electrical double‐layer capacitive and pseudocapacitive materials into novel hybrid materials is crucial to realize supercapacitors with high energy and power densities. Here, high levels of energy and power densities are demonstrated in supercapacitors based on a new type of nanohybrid electrode consisting of polyoxometalate (POM)‐coupled graphene in which a polymeric ionic liquid (henceforth simply PIL) serves as an interfacial linker. The adoption of PIL in the construction of nanohybrids enables a uniform distribution of discrete POM molecules along with a large surface area of graphene sheets. When testing electrochemical characteristics under a two‐electrode system, as‐prepared supercapacitors exhibit a high specific capacitance (408 F g−1 at 0.5 A g−1), rapid rate capability (92% retention at 10 A g−1), a long cycling life (98% retention during 2000 cycles), and high energy (56 Wh kg−1) and power (52 kW kg−1) densities. First‐principles calculations and impedance spectroscopy analysis reveal that the PILs enhance the redox reactions of POMs by providing efficient ion transfer channels and facilitating the charge transfer in the nanohybrids. A new type of polyoxometalate‐coupled graphene through polymeric ionic liquid linker is synthesized as electrode materials for high‐performance supercapacitors that can combine high power and energy densities, cycling stability, and high rate capability.
      PubDate: 2014-09-11T13:08:22.688038-05:
      DOI: 10.1002/adfm.201401798
  • Polyfluorene Derivatives are High‐Performance Organic
           Hole‐Transporting Materials for Inorganic−Organic Hybrid
           Perovskite Solar Cells
    • Authors: Zonglong Zhu; Yang Bai, Harrison Ka Hin Lee, Cheng Mu, Teng Zhang, Lixia Zhang, Jiannong Wang, He Yan, Shu Kong So, Shihe Yang
      Pages: n/a - n/a
      Abstract: Photovoltaics based on organic−inorganic perovskites offer new promise to address the contemporary energy and environmental issues. These solar cells have so far largely relied on small‐molecule hole transport materials such as spiro‐OMeTAD, which commonly suffer from high cost and low mobility. In principle, polyfluorene copolymers can be an ideal alternative to spiro‐OMeTAD, given their low price, high hole mobility and good processability, but this potential has not been explored. Herein, polyfluorene derived polymers‐TFB and PFB, which contain fluorine and arylamine groups, are demonstrated and can indeed rival or even outperform spiro‐OMeTAD as efficient hole‐conducting materials for perovskite solar cells. In particular, under the one‐step perovskite deposition condition, TFB achieves a 10.92% power conversion efficiency that is considerably higher than that with spiro‐OMeTAD (9.78%), while using the two‐step perovskite deposition method, about 13% efficient solar cells with TFB (12.80%) and spiro‐OMeTAD (13.58%) are delivered. Photo­luminescence reveals the efficient hole extraction and diffusion at the interface between CH3NH3PbI3 and the hole conducting polymer. Impedance spectroscopy uncovers the higher electrical conductivity and lower series resistance than spiro‐OMeTAD, accounting for the significantly higher fill factor, photocurrent and open‐circuit voltage of the TFB‐derived cells than with spiro‐MeOTAD. Polyfluorene derivatives are applied for inorganic−organic hybrid perovskite solar cells, and indeed can rival or outperform spiro‐OMeTAD as efficient hole‐conducting materials for perovskite solar cells. In particular, with the one‐step deposition method, TFB achieves a 10.92% power conversion efficiency, which is considerably higher than that with spiro‐OMeTAD (9.78%).
      PubDate: 2014-09-11T13:08:20.017695-05:
      DOI: 10.1002/adfm.201401557
  • Bio‐Hybrid Tumor Cell‐Templated Capsules: A Generic
           Formulation Strategy for Tumor Associated Antigens in View of Immune
    • Authors: Lien Lybaert; Elly De Vlieghere, Riet De Rycke, Nane Vanparijs, Olivier De Wever, Stefaan De Koker, Bruno G. De Geest
      Pages: n/a - n/a
      Abstract: For the development of effective anti‐cancer vaccines, tumor associated antigens need to be internalized by antigen presenting cells alongside specific co‐stimulatory signals. Interestingly, relative to soluble antigens, nano‐ and micro‐particulate antigens are much better presented to CD8 T cells, a crucial step in the induction of cytotoxic T cells that can eliminate malignant cells. In this regard, a generic strategy to encapsulate cancer cell derived proteins into a particulate delivery system would be of high interest. Here we present a versatile approach to incorporate cancer cell proteins into polymeric capsules using the cells themselves as templates for layer‐by‐layer assembly of complimentary interacting species. After coating, the cells are killed by hypo‐osmotic treatment leading to bio‐hybrid capsules loaded with cell lysate. Particular focus is devoted in this work on choosing the optimal coating components and conditions to maximize cell membrane integrity during the coating process, minimize pre‐mature protein release and achieve optimal encapsulation of cell lysate upon lysis of the cells. To further underline the generic nature of our approach, we demonstrate that heat shock proteins, important immune‐activators, can be induced and encapsulated into the bio‐hybrid capsules. Melanoma cells are coated via layer‐by‐layer deposition of poly(vinylpyrrolidone) and tannic acid followed by lysis through hypo‐osmotic treatment. The coating is optimized to preserve the cellular integrity and optimal retention of the cellular proteins within the cell‐templated capsules. In addition, a proof‐of‐concept study is performed to demonstrate the encapsulation of heat shock proteins as potential immune‐activators.
      PubDate: 2014-09-11T13:08:16.02715-05:0
      DOI: 10.1002/adfm.201402303
  • High‐Performance Flexible Broadband Photodetector Based on
           Organolead Halide Perovskite
    • Authors: Xin Hu; Xiaodong Zhang, Lin Liang, Jian Bao, Shuang Li, Wenlong Yang, Yi Xie
      Pages: n/a - n/a
      Abstract: Organolead halide perovskites have attracted extensive attentions as light harvesting materials for solar cells recently, because of its high charge‐carrier mobilities, high photoconversion efficiencies, low energy cost, ease of deposition, and so on. Herein, with CH3NH3PbI3 film deposited on flexible ITO coated substrate, the first organolead halide perovskite based broadband photodetector is demonstrated. The organolead halide perovskite photodetector is sensitive to a broadband wavelength from the ultraviolet light to entire visible light, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19×103%, 5.84% at 365 nm and 780 nm with a voltage bias of 3 V, respectively. Additionally, the as‐fabricated photodetector exhibit excellent flexibility and robustness with no obvious variation of photocurrent after bending for several times. The organolead halide perovskite photodetector with high sensitivity, high speed and broad spectrum photoresponse is promising for further practical applications. And this platform creates new opportunities for the development of low‐cost, solution‐processed and high‐efficiency photodetectors. Organometal halide perovskites are shown tremendous potential as incident light absorbers for optoelectronic applications. In this work, a broadband photo­detecotor is demonstrated based on the CH3NH3PbI3 film, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19 × 103 %, 5.84% at 365 and 780 nm, respectively. Our results provide new opportunities for the development of high‐efficiency photodetectors.
      PubDate: 2014-09-11T13:02:46.935422-05:
      DOI: 10.1002/adfm.201402020
  • Materials Fabrication from Native and Recombinant Thermoplastic Squid
    • Authors: Abdon Pena‐Francesch; Sergio Florez, Huihun Jung, Aswathy Sebastian, Istvan Albert, Wayne Curtis, Melik C. Demirel
      Pages: n/a - n/a
      Abstract: Natural elastomers made from protein extracts have received significant interest as eco‐friendly functional materials due to their unique mechanical and optical properties emanating from secondary structures. The next generation sequencing approach is used to identify protein sequences in a squid ring teeth complex extracted from Loligo vulgaris and the use of recombinant expression is demonstrated in the fabrication of a new generation of thermoplastic materials. Native and recombinant thermoplastic squid proteins exhibit reversible solid to melt phase transition, enabling them to be thermally shaped into 3D geometries such as fibers, colloids, and thin films. Direct extraction or recombinant expression of protein based thermoplastics opens up new avenues for materials fabrication and synthesis, which will eventually be competitive with the high‐end synthetic oil based plastics. Protein sequences are identified in a squid ring teeth complex extracted from Loligo vulgaris and recombinant expression for its use in the fabrication of thermoplastic materials is demonstrated for the first time. Earlier attempts to create recombinant thermoplastic SRT protein failed due to the choice of larger molecular weight proteins. Reversible solid is demonstrated to melt phase transition of the recombinant protein, which is thermally shaped into any 3D geometries.
      PubDate: 2014-09-11T12:59:59.272311-05:
      DOI: 10.1002/adfm.201401940
  • Masthead: (Adv. Funct. Mater. 35/2014)
    • Pages: n/a - n/a
      PubDate: 2014-09-11T12:57:38.982885-05:
      DOI: 10.1002/adfm.201470235
  • Three‐Dimensional Inkjet‐Printed Interconnects Using
           Functional Metallic Nanoparticle Inks
    • Authors: Jacob A. Sadie; Vivek Subramanian
      Pages: n/a - n/a
      Abstract: Inkjet‐printed gold nanoparticle pillars are investigated as a high‐performance alternative to conventional flip‐chip interconnects for electronic packages, with significant advantages in terms of mechanical/chemical robustness and conductivity. The process parameters critical to pillar fabrication are described and highly uniform pillar arrays are demonstrated. More generally, this work underscores the impact of sintering on the electrical, mechanical, structural, and compositional properties of three‐dimensional nanoparticle‐based structures. Using heat treatments as low as 200 °C, electrical and mechanical performance that outcompetes conventional lead‐tin eutectic solder materials is achieved. With sintering conditions reaching 300 °C it is possible to achieve pillars with properties comparable to bulk gold. This work demonstrates the immense potential for both inkjet printing and metal nanoparticles to become a viable and cost‐saving alternative to both conventional electronic packaging processes and application‐specific integration schemes. Inkjet‐printed 3D nanoparticle pillars are investigated as a novel alternative to semiconductor packaging interconnects. The first detailed study of sintering in such large nanoparticle‐based structures reveals electrical, elastic, and shear properties that outperform conventional materials undergoing similar heat treatments. The results indicate much promise for nanoparticle‐based materials in advanced electronic packages and provide critical insights for further materials optimization.
      PubDate: 2014-09-11T12:55:34.500762-05:
      DOI: 10.1002/adfm.201401312
  • Post‐deposition Activation of Latent Hydrogen‐Bonding: A New
           Paradigm for Enhancing the Performances of Bulk Heterojunction Solar Cells
    • Authors: Francesco Bruni; Mauro Sassi, Marcello Campione, Umberto Giovanella, Riccardo Ruffo, Silvia Luzzati, Francesco Meinardi, Luca Beverina, Sergio Brovelli
      Pages: n/a - n/a
      Abstract: Small conjugated molecules (SM) are gaining momentum as an alternative to semiconducting polymers for the production of solution‐processed bulk heterojunction (BHJ) solar cells. The major issue with SM‐BHJs is the low carrier mobility due to the scarce control on the phase‐segregation process and consequent lack of preferential percolative pathways for electrons and holes to the extraction electrodes. Here, a new paradigm for fine tuning the phase‐segregation in SM‐BHJs, based on the post‐deposition exploitation of latent hydrogen bonding in binary mixtures of PCBM with suitably functionalized electron donor molecules, is demonstrated. The strategy consist in the chemical protection of the H‐bond forming sites of the donor species with a thermo‐labile functionality whose controlled thermal cleavage leads to the formation of stable, crystalline, phase‐separated molecular aggregates. This approach allows the fine tuning of the nanoscale film connectivity and thereby to simultaneously optimize the generation of geminate carriers at the donor–acceptor interfaces and the extraction of free charges via ordered phase‐separated domains. As a result, the PV efficiency undergoes an over twenty‐fold increase with respect to control devices. This strategy, demonstrated here with mixtures of diketopyrrolopyrrole derivatives with PCBM can be extended to other molecular systems for achieving highly efficient SM‐BHJ solar cells. A new paradigm for the fine tuning the phase segregation in SM‐BHJs, based on the post‐deposition exploitation of latent hydrogen bonds in binary molecular blends, is demonstrated. This approach allows fine tuning of the nanoscale film connectivity and to simultaneously optimize charge generation and extraction via ordered phase‐separated domains. As a result, the PV efficiency undergoes a twenty‐fold increase with respect to control devices.
      PubDate: 2014-09-11T12:55:28.646271-05:
      DOI: 10.1002/adfm.201400896
  • Atomistic Origin of the Enhanced Crystallization Speed and n‐Type
           Conductivity in Bi‐doped Ge‐Sb‐Te Phase‐Change
    • Authors: Jonathan M. Skelton; Anuradha R. Pallipurath, Tae‐Hoon Lee, Stephen R. Elliott
      Pages: n/a - n/a
      Abstract: Phase‐change alloys are the functional materials at the heart of an emerging digital‐storage technology. The GeTe‐Sb2Te3 pseudo‐binary systems, in particular the composition Ge2Sb2Te5 (GST), are one of a handful of materials which meet the unique requirements of a stable amorphous phase, rapid amorphous‐to‐crystalline phase transition, and significant contrasts in optical and electrical properties between material states. The properties of GST can be optimized by doping with p‐block elements, of which Bi has interesting effects on the crystallization kinetics and electrical properties. A comprehensive simulational study of Bi‐doped GST is carried out, looking at trends in behavior and properties as a function of dopant concentration. The results reveal how Bi integrates into the host matrix, and provide insight into its enhancement of the crystallization speed. A straightforward explanation is proposed for the reversal of the charge‐carrier sign beyond a critical doping threshold. The effect of Bi on the optical properties of GST is also investigated. The microscopic insight from this study may assist in the future selection of dopants to optimize the phase‐change properties of GST, and also of other PCMs, and the general methods employed in this work should be applicable to the study of related materials, for example, doped chalcogenide glasses. First‐principles atomistic modelling reveals how doping with Bi changes the crystallization dynamics and electrical properties of chalcogenide phase‐change materials. In this work, a comprehensive molecular‐dynamics study of Bi‐doped Ge2Sb2Te5 is presented, investigating the microscopic origin of the experimentally reported enhancement in crystallization speed, and reversal of the charge‐carrier sign from p‐ to n‐type, on doping.
      PubDate: 2014-09-11T12:47:02.209647-05:
      DOI: 10.1002/adfm.201401202
  • Phase Transitions and Anisotropic Thermal Expansion in High Mobility
           Core‐expanded Naphthalene Diimide Thin Film Transistors
    • Authors: Eliot Gann; Xike Gao, Chong‐an Di, Christopher R. McNeill
      Pages: n/a - n/a
      Abstract: In situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) is used to study the in situ thermal behavior of solution‐processed, high mobility core‐expanded naphthalene diimide thin films. A series of three different molecules is studied where the side‐chain branching position is systematically varied through the use of 2‐, 3‐ and 4‐branched N‐alkyl chains. For all molecules, a number of different phases and their associated phase transitions are observed with heating up to 200 °C. In situ GIWAXS measurements allow following significant variations of packing in each phase including crystalline coherence length, orientation, d‐spacing, and paracrystallinity, as well as, for the first time, thin film thermal expansion coefficients in both the in‐plane and out‐of‐plane direction. Relating these parameters with device measurements of quenched films, a striking correlation is found between high field‐effect mobilities and low in‐plane thermal expansion coefficients. This relationship indicates that high in‐plane thermal expansion coefficients are detrimental to in‐plane charge transport due to the formation of nanoscale defects in the critical first few monolayers upon quenching. In situ grazing incidence wide angle X‐ray scattering monitors the crystallinity and phase behavior of thin film organic systems during heating. In the case of solution‐processed core expanded naphthalene diimide small molecules, the branching location of alkyl side chains tunes in‐plane thermal expansion coefficients which in turn correlate with mobility of the quenched film.
      PubDate: 2014-09-11T12:46:59.907325-05:
      DOI: 10.1002/adfm.201401228
  • Over 1.1 eV Workfunction Tuning of Cesium Intercalated Metal Oxides for
           Functioning as Both Electron and Hole Transport Layers in Organic
           Optoelectronic Devices
    • Authors: Xinchen Li; Fengxian Xie, Shaoqing Zhang, Jianhui Hou, Wallace C. H. Choy
      Pages: n/a - n/a
      Abstract: In this paper, over 1.1 eV continuous tuning of metal oxides workfunction is realized by cesium intercalation, making the metal oxide function as both electron transport layer and hole transport layer in organic optoelectronic devices. The demonstrated metal oxides are commonly used molybdenum oxide and vanadium oxide. The proposed approach of synthesizing cesium intercalated metal oxides has interesting properties of room‐temperature, ambient atmosphere, water free and solution process, favoring the formation of metal oxides as carrier transport layers at different regions in multilayered devices and large scale fabrication of organic optoelectronics at low cost. Besides the wide range of controllable workfunction adjustment, band structures, and electrical properties are investigated in detail, to understand the effects of cesium intercalation on metal oxides. The device results show that, using the proposed cesium intercalation approach, each of the two investigated metal oxides can function as both ETL and HTL in organic solar cells and organic light emitting diodes with very good device performances. Consequently, with the interesting properties in film synthesis, the proposed cesium intercalated metal oxides can achieve continuously workfunction tuning over a large range and contribute to evolution of the simple route for fabricating high performance organic optoelectronic devices. Cesium intercalated metal oxides with continuously large workfunction tuning ability function as both electron and hole transport layers in organic optoelectronic devices. This approach has the features of room temperature, water free and solution process. Analyses indicate that energy band structures of metal oxides can be modified to adjust electron and hole transport properties by the Cs intercalation process.
      PubDate: 2014-09-11T12:35:34.048653-05:
      DOI: 10.1002/adfm.201401969
  • Pyrolysed 3D‐Carbon Scaffolds Induce Spontaneous Differentiation of
    • Authors: Letizia Amato; Arto Heiskanen, Claudia Caviglia, Fozia Shah, Kinga Zór, Maciej Skolimowski, Marc Madou, Lauge Gammelgaard, Rasmus Hansen, Emma G. Seiz, Milagros Ramos, Tania Ramos Moreno, Alberto Martínez‐Serrano, Stephan S. Keller, Jenny Emnéus
      Pages: n/a - n/a
      Abstract: Structurally patterned pyrolysed three‐dimensional carbon scaffolds (p3D‐carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine‐producing neurons and the 3D‐topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to‐date unseen efficiency in both two‐dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D‐carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differentiation to dopaminergic phenotype combined with real‐time in situ confirmation of the fate of the hNSC‐derived neurons. Pyrolysed 3D carbon scaffolds dimensionally reaching the limit of UV‐lithography are for the first time presented and applied for differentiation of human neural stem cells (hNSCs), demonstrating the uniqueness of pyrolysed carbon as a material that induces spontaneous differentiation in 80% of hNSCs into dopaminergic neurons. The scaffold simultaneously serves as a mechanical and biocompatible support and 3D electrochemical sensor for dopamine detection.
      PubDate: 2014-09-11T12:35:31.681525-05:
      DOI: 10.1002/adfm.201400812
  • Comparative Study of the N‐Type Doping Efficiency in
           Solution‐processed Fullerenes and Fullerene Derivatives
    • Authors: Stephan Rossbauer; Christian Müller, Thomas D. Anthopoulos
      Pages: n/a - n/a
      Abstract: Molecular doping of organic semiconductors and devices represents an enabling technology for a range of emerging optoelectronic applications. Although p‐type doping has been demonstrated in a number of organic semiconductors, efficient n‐type doping has proven to be particularly challenging. Here, n‐type doping of solution‐processed C60, C70, [60]PCBM, [70]PCBM and indene‐C60 bis‐adduct by 1H‐benzimidazole (N‐DMBI) is reported. The doping efficiency for each system is assessed using field‐effect measurements performed under inert atmosphere at room temperature in combination with optical absorption spectroscopy and atomic force microscopy. The highest doping efficiency is observed for C60 and C70 and electron mobilities up to ≈2 cm2/Vs are obtained. Unlike in substituted fullerenes‐based transistors where the electron mobility is found to be inversely proportional to N‐DMBI concentration, C60 and C70 devices exhibit a characteristic mobility increase by approximately an order of magnitude with increasing dopant concentration up to 1 mol%. Doping also appears to significantly affect the bias stability of the transistors. The work contributes towards understanding of the molecular doping mechanism in fullerene‐based semiconductors and outlines a simple and highly efficient approach that enables significant improvement in device performance through facile chemical doping. Doping of organic semiconductors is a key technology for tuning their charge transport properties. Here a systematic comparison of n‐type doping of solution‐processed un/substituted fullerenes with regard to optical, electrical, and morphological properties, is presented. In case of C60 and C70, n‐doping is found to both increase the electron mobility and improve the bias stress stability of the transistors.
      PubDate: 2014-09-10T09:10:53.443286-05:
      DOI: 10.1002/adfm.201401842
  • Profile Control in Block Copolymer Nanostructures using Bilayer Thin Films
           for Enhanced Pattern Transfer Processes
    • Authors: Chunlin He; Mark P. Stoykovich
      Pages: n/a - n/a
      Abstract: Although control over the domain orientation and long‐range order of block copolymer nanostructures self‐assembled in thin films has been achieved using various directed self‐assembly techniques, more challenging but equally important for many lithographic applications is the ability to precisely control the shape of the interface between domains. Here, a novel layer‐by‐layer approach is reported for controlling the interface profile of block copolymer nanostructures and the application of an undercut sidewall profile for an enhanced metal lift‐off process for pattern transfer is demonstrated. Bilayer films of lamellar‐forming poly(styrene‐block‐methyl methacrylate) are assembled and thermally cross‐linked on wafer substrates in a layer‐by‐layer process. The top layer, while being directed to self‐assemble on the lamellae of the underlying layer, has a tunable composition and polystyrene domain width independent of that of the bottom layer. Undercut or negative sidewall profiles in the PS nanostructures are proven to provide better templates for the lift‐off of Au nanowires by achieving complete and defect‐free pattern transfer more than three times faster than comparable systems with vertical sidewall profiles. More broadly, the layer‐by‐layer approach presented here provides a pathway to achieving sophisticated interface profiles and user‐defined 3D block copolymer nanostructures in thin films. Bilayer thin films of lamellar‐forming poly(styrene‐block‐methyl methacrylate) are self‐assembled and thermally cross‐linked on wafer substrates in a layer‐by‐layer process. This layer‐by‐layer approach can provide novel control over the interface profile of block copolymer nanostructures and enables an undercut sidewall profile that enhances metal lift‐off processes for pattern transfer.
      PubDate: 2014-09-10T09:10:50.284294-05:
      DOI: 10.1002/adfm.201401810
  • Fabrication and Characterization of Organic Single Crystal‐Based
           Light‐Emitting Devices with Improved Contact Between the Metallic
           Electrodes and Crystal
    • Authors: Ran Ding; Jing Feng, Xu‐Lin Zhang, Wei Zhou, Hong‐Hua Fang, Yue‐Feng Liu, Qi‐Dai Chen, Hai‐Yu Wang, Hong‐Bo Sun
      Pages: n/a - n/a
      Abstract: Organic single crystals have attracted great attention because of their advantages of high charge‐carrier mobility, high chemical purity, and potential for flexible optoelectronic devices. However, their intrinsic properties of sensitive to organic solvent and fragile result in a difficulty in the fabrication of the organic crystal‐based devices. In this work, a simple and non‐destructive technique of template stripping is employed to fabricate single‐crystal‐based organic light‐emitting devices (OLEDs). Efficient and uniform carrier injection induced by an improved contact between crystals and both top and bottom electrodes is realized, so that a homogeneous and bright electroluminescence (EL) are obtained. Highly polarized EL and even white emission is also observed. Moreover, the crystal‐based OLEDs exhibit good flexibility, and keep stable EL under a small bending radius and after repeated bending. It is expectable that this technique would support broad applications of the organic single crystals in the crystal‐based optoelectronic devices. Organic single‐crystal‐based LEDs with bright and homogeneous luminescence are realized due to an improved contact between the crystals and both top and bottom electrodes by employing the template stripping technique. Both surface and edge emission have been realized by using two kinds of crystals. Highly polarized EL and white emission are also observed from the crystal‐based OLEDs. Moreover, the crystal‐based OLEDs exhibit high flexibility and mechanical robustness.
      PubDate: 2014-09-10T09:10:44.910365-05:
      DOI: 10.1002/adfm.201400832
  • Covalent Functionalization of Multi‐walled Carbon Nanotubes with a
           Gadolinium Chelate for Efficient T1‐Weighted Magnetic Resonance
    • Authors: Iris Marangon; Cécilia Ménard‐Moyon, Jelena Kolosnjaj‐Tabi, Marie Lys Béoutis, Lénaic Lartigue, Damien Alloyeau, Elzbieta Pach, Belén Ballesteros, Gwennhael Autret, Tsedev Ninjbadgar, Dermot F. Brougham, Alberto Bianco, Florence Gazeau
      Pages: n/a - n/a
      Abstract: Given the promise of carbon nanotubes (CNTs) for photothermal therapy, drug delivery, tissue engineering, and gene therapy, there is a need for non‐invasive imaging methods to monitor CNT distribution and fate in the body. In this study, non‐ionizing whole‐body high field magnetic resonance imaging (MRI) is used to follow the distribution of water‐dispersible non‐toxic functionalized CNTs administrated intravenously to mice. Oxidized CNTs are endowed with positive MRI contrast properties by covalent functionalization with the chelating ligand diethylenetriaminepentaacetic dianhydride (DTPA), followed by chelation to Gd3+. The structural and magnetic properties, MR relaxivities, cellular uptake, and application for MRI cell imaging of Gd‐CNTs in comparison to the precursor oxidized CNTs are evaluated. Despite the intrinsic T2 contrast of oxidized CNTs internalized in macrophages, the anchoring of paramagnetic gadolinium onto the nanotube sidewall allows efficient T1 contrast and MR signal enhancement, which is preserved after CNT internalization by cells. Hence, due to their high dispersibility, Gd‐CNTs have the potential to produce positive contrast in vivo following injection into the bloodstream. The uptake of Gd‐CNTs in the liver and spleen is assessed using MRI, while rapid renal clearance of extracellular Gd‐CNTs is observed, confirming the evidences of other studies using different imaging modalities. Oxidized multi‐walled carbon nanotubes are provided with positive MRI contrast properties by covalent functionalization with the chelating ligand DTPA followed by chelation to Gd3+. Despite the intrinsic T2 contrast of oxidized CNTs, the covalent anchoring of paramagnetic gadolinium ions on CNT sidewall allows high dispersibility and efficient positive MR contrast both in vitro in labeled cells and in vivo after intravenous injection of CNTs in mice.
      PubDate: 2014-09-10T00:57:10.896122-05:
      DOI: 10.1002/adfm.201402234
  • Heavily Doped poly(3,4‐ethylenedioxythiophene) Thin Films with High
           Carrier Mobility Deposited Using Oxidative CVD: Conductivity Stability and
           Carrier Transport
    • Authors: Sunghwan Lee; David C. Paine, Karen K. Gleason
      Pages: n/a - n/a
      Abstract: The transparent conductingpoly(3,4‐ethylenedioxythiophene) (PEDOT) is of interest for various optoelectronic device applications. Here, the conductivity stability of PEDOT processed using oxidative chemical‐vapor‐deposition (oCVD) with FeCl3 as an oxidant is primarily dominated by the change in carrier density when aged in air. To establish the mechanism for the conductivity decrease, the changes in carrier density and carrier mobility of PEDOT films are separately monitored using an AC Hall Effect measurement system. The measured electrical properties reveal that a decrease in carrier density dominates the conductivity decrease during annealing. X‐ray diffraction analysis made on the HBr‐ and MeOH‐rinsed PEDOT samples identifies the Fe‐related dedoping phase of Fe(OH)2 and provides the dedoping mechanism. The carrier transport study demonstrates heavily doped oCVD PEDOT with the carrier density higher than ~1020 cm–3, and in this regime, an increase in carrier density yields lower carrier mobility which shows that the carrier transport is governed by the ionized impurity scattering mechanism due to increased dopant counter‐anions. These findings of the mechanisms for PEDOT conductivity decrease and carrier transport behavior may be important to organic optoelectronic device applications that show a strong effect of air‐exposure and low‐temperature annealing on the device stability and performance. Heavily‐doped poly(3,4‐ethylenedioxy­thiophene)(PEDOT) films with carrier density higher than ~1020 cm‐3 are produced using oxidative chemical‐vapor‐deposition. The mechanisms for the conductivity decrease and carrier transport behavior in heavily‐doped PEDOT, which are important to organic optoelectronic device applications that show a strong effect of air‐exposure and low temperature annealing on the device stability and performance, are suggested.
      PubDate: 2014-09-10T00:57:02.113152-05:
      DOI: 10.1002/adfm.201401282
  • Thieno[3,2‐b]thiophene Flanked Isoindigo Polymers for High
           Performance Ambipolar OFET Applications
    • Authors: Iain Meager; Mark Nikolka, Bob C. Schroeder, Christian B. Nielsen, Miquel Planells, Hugo Bronstein, Joseph W. Rumer, David Ian James, Raja Shahid Ashraf, Aditya Sadhanala, Pascal Hayoz, Jean‐Charles Flores, Henning Sirringhaus, Iain McCulloch
      Pages: n/a - n/a
      Abstract: The synthesis of a new thieno[3,2‐b]thiophene isoindigo (iITT) based monomer unit, and its subsequent incorporation into a series of alternating copolymers is reported. Copolymerisation with benzothiadiazole, bithiophene and thiophene comonomer units by palladium catalysed cross coupling gives three new narrow band gap semiconducting polymers for OFET applications. Extending the fused nature of the isoindigo core serves to further enhance molecular orbital overlap along the polymer backbones and facilitate good charge transport characteristics thus demonstrating the potential of extending the fused ring system that is attached to the isoindigo core. When used as the semiconducting channel in top‐gate/bottom‐contact OFET devices, good ambipolar properties are observed, with hole and electron mobilities up to 0.4 cm2/Vs and 0.7 cm2/Vs respectively. The three new polymers show good stability, with high temperature annealing showing an increase in the crystallinity of the polymers which corresponds directly to charge carrier mobility improvement as shown by X‐ray diffraction, atomic force microscopy and photothermal deflection spectroscopy. A series of new isoindigo semiconducting polymers with thieno[3,2‐b]thiophene as the donor moiety are synthesized. By fusing an extra aromatic ring to the isoindigo core absorption profiles are shifted into the near‐IR with optical band gaps as narrow as 1.05 eV. Organic top‐gate bottom‐contact transistor devices were fabricated demonstrating good ambipolar mobilities.
      PubDate: 2014-09-09T23:53:37.891834-05:
      DOI: 10.1002/adfm.201402307
  • Precious‐Metal‐Free Nanocatalysts for Highly Efficient
           Hydrogen Production from Hydrous Hydrazine
    • Authors: Jun Wang; Yang Li, Yu Zhang
      Pages: n/a - n/a
      Abstract: Hydrous hydrazine (H2NNH2·H2O) has generally been considered a promising hydrogen storage carrier because of inherent advantages such as its high hydrogen content and easy recharging as a liquid. Unfortunately, the decomposition of hydrous hydrazine to H2 is terribly sluggish and/or not entirely favored—a competing decomposition to ammonia may be preferred. This has been the case using noble‐metal catalysts and using non‐precious‐metal‐based catalysts, even at elevated temperatures. To overcome this challenge, non‐precious‐metal‐based Cu@Fe5Ni5 core@shell nanocatalysts are prepared using an in situ seeding‐growth approach. Unexpectedly, the catalyst exerts 100% H2 selectivity and excellent activity and stability toward the complete decomposition of hydrous hydrazine, which is due to the synergistic effect of the core@shell structure. These promising results will certainly promote the effective application of hydrous hydrazine as a potential hydrogen storage material. Hydrous hydrazine has great potential as a suitable liquid‐hydrogen storage material, provided that a low‐cost and high‐performance dehydrogenation catalyst is developed. The core@shell nanocatalyst Cu@Fe5Ni5 enables hydrazine decomposition such that the H2‐producing reaction is completely favored over the ammonia‐producing reaction, making hydrous hydrazine a promising hydrogen storage material.
      PubDate: 2014-09-09T23:53:33.881503-05:
      DOI: 10.1002/adfm.201401731
  • A Photoresponsive Red‐Hair‐Inspired Polydopamine‐Based
           Copolymer for Hybrid Photocapacitive Sensors
    • Authors: Marianna Ambrico; Nicola Fyodor Della Vecchia, Paolo F. Ambrico, Antonio Cardone, Stefania R. Cicco, Teresa Ligonzo, Roberto Avolio, Alessandra Napolitano, Marco d’Ischia
      Pages: n/a - n/a
      Abstract: Inspired by the powerful photosensitizing properties of the red hair pigments pheomelanins, a photoresponsive cysteine‐containing variant of the adhesive biopolymer polydopamine (pDA) is developed via oxidative copolymerization of dopamine (DA) and 5‐S‐cysteinyldopamine (CDA) in variable ratios. Chemical and spectral analysis indicate the presence of benzothiazole/benzothiazine units akin to those of pheomelanins. p(DA/CDA) copolymers display ­impedance properties similar to those of biological materials and a marked photoimpedance response to light stimuli. The use of the p(DA/CDA) copolymer to implement a solution‐processed hybrid photocapacitive/resistive metal‐insulator‐semiconductor (MIS) device disclosed herein is the first example of technological exploitation of photoactive, red‐hair‐inspired biomaterials as soft enhancement layer for silicon in an optoelectronic device. The bio‐inspired materials described herein may provide the active component of new hybrid photocapacitive sensors with a chemically tunable response to visible light. Incorporation of cysteinyldopamine(CDA)‐derived units into polydopamine (pDA) leads to an innovative bioinspired material combining the photosensitizing properties of red human hair pigments with the electrical properties of melanins. The resulting mixed‐type biopolymers exhibit a markedly enhanced response to UV light and open the doorway to unprecedented bio‐inspired metal‐insulator‐semiconductor photo‐capacitor hybrid devices with tunable optical response for light sensing applications.
      PubDate: 2014-09-08T10:44:38.457141-05:
      DOI: 10.1002/adfm.201401377
  • Water‐Soluble and Lowly Toxic Sulphur Quantum Dots
    • Authors: Shunxing Li; Dejian Chen, Fengying Zheng, Haifeng Zhou, Shaoxiong Jiang, Yijin Wu
      Pages: n/a - n/a
      Abstract: Here, a new class of quantum dots, that is, sulphur quantum dots (SQDs), which are synthesized by the phase interfacial reaction, is reported. The prepared SQDs are monodisperse with a narrow size distribution (average 1.6 nm in size), excellent aqueous dispersibility, ultrahigh photostability, and lowly toxicity. Because of abundant oxidized sulphur species on the surface of SQDs, the incorporation of TiO2 with SQDs results in a synergistic effect for the TiO2‐based photocatalysts offering more effective environmental applications. It is demonstrated that SQDs‐TiO2 nanocomposite can enhance the photocatalytic activity of producing hydrogen (enhancement factor for 191) in methanol‐water system. The SQDs also can used as fluorescent probe for highly selective quantitative detection Fe3+ in an aqueous solution contained various metal ions. Sulphur quantum dots are first synthesized by a ox‐red reaction at the water–oil interface. The sulphur quantum dots show good water solubility, excellent stability, and lowly toxicity. Sulphur quantum dots sensitized TiO2 photocatalyze the generation of H2 from a water/methanol mixture upon irradiation with UV. A Fe3+ ions fluorescence sensor demonstrates good linearity and high selectiveness.
      PubDate: 2014-09-08T10:40:23.561097-05:
      DOI: 10.1002/adfm.201402087
  • Very High Efficiency Orange‐Red Light‐Emitting Devices with
           Low Roll‐Off at High Luminance Based on an Ideal Host‐Guest
           System Consisting of Two Novel Phosphorescent Iridium Complexes with
           Bipolar Transport
    • Authors: Guomeng Li; Dongxia Zhu, Tai Peng, Yu Liu, Yue Wang, Martin R. Bryce
      Pages: n/a - n/a
      Abstract: Two phosphorescent iridium complexes with bipolar transporting ability, namely FPPCA (500 nm) and BZQPG (600 nm), are synthesized and employed as an ideal host‐guest system for phosphorescent organic light emitting diodes (PHOLEDs).The devices give very high‐efficiency orange‐red emission from BZQPG with maximum external quantum efficiency (EQE or ηext) of >27% and maximum power efficiency (PE or ηp) of >75 lm/W, and maintain high levels of 26% and 55 lm/W, 25% and 40 lm/W at high luminance of 1000 and 5000 cd m−2, respectively, within a range of 8–15 wt% of BZQPG. The realization of such high and stable EL performance results from the coexistence of two parallel paths: i) effective energy transfer from host (FPPCA) to guest (BZQPG) and ii) direct exciton formation on the BZQPG emitter, which can alternately dominate the electrophosphorescent emission. This all‐phosphor doping system removes the charge‐injection barrier from the charge‐transport process to the emissive layer (EML) due to the inherent narrow Eg of both phosphors. Therefore, this ideal host–guest system represents a new design to produce PHOLEDs with high efficiency and low efficiency roll‐off using a simple device configuration. An all‐phosphor host–guest doping system based on two novel Ir complexes possessing bipolar transporting ability realizes very‐high efficiency orange‐red phosphorescent organic light‐emitting devices, which exhibit constant peak electroluminescent efficiency of >75 lm W‐1 for power efficiency and 26% for external quantum efficiency as well as extremely low efficiency roll‐off within a range of 8 and 15 wt%.
      PubDate: 2014-09-08T10:40:04.72261-05:0
      DOI: 10.1002/adfm.201402177
  • Extremely Efficient White Organic Light‐Emitting Diodes for General
    • Authors: Qing‐Dong Ou; Lei Zhou, Yan‐Qing Li, Su Shen, Jing‐De Chen, Chi Li, Qian‐Kun Wang, Shuit‐Tong Lee, Jian‐Xin Tang
      Pages: n/a - n/a
      Abstract: Highly power‐efficient white organic light‐emitting diodes (OLEDs) are still challenging to make for applications in high‐quality displays and general lighting due to optical confinement and energy loss during electron‐photon conversion. Here, an efficient white OLED structure is shown that combines deterministic aperiodic nanostructures for broadband quasi‐omnidirectional light extraction and a multilayer energy cascade structure for energy‐efficient photon generation. The external quantum efficiency and power efficiency are raised to 54.6% and 123.4 lm W−1 at 1000 cd m−2. An extremely small roll‐off in efficiency at high luminance is also obtained, yielding a striking value of 106.5 lm W−1 at 5000 cd m−2. In addition to a substantial increase in efficiency, this device structure simultaneously offers the superiority of angular color stability over the visible wavelength range compared to conventional OLEDs. It is anticipated that these findings could open up new opportunities to promote white OLEDs for commercial applications. Highly efficient, white, organic light‐emitting diodes are achieved by combining deterministic aperiodic nanostructures for broadband light extraction with a multilayer energy cascade structure for energy‐efficient photon generation. This results in light‐emitting diodes with a record power efficiency of 123.4 lm W−1 at 1000 cd m−2 with superior color stability and extremely small efficiency roll‐off.
      PubDate: 2014-09-08T10:34:48.113976-05:
      DOI: 10.1002/adfm.201402026
  • Reversible Ferromagnetic Phase Transition in Electrode‐Gated
    • Authors: Bin Cui; Cheng Song, Guangyue Wang, Yinuo Yan, Jingjing Peng, Jinghui Miao, Haijun Mao, Fan Li, Chao Chen, Fei Zeng, Feng Pan
      Pages: n/a - n/a
      Abstract: The electronic phase transition has been considered as a dominant factor in the phenomena of colossal magnetoresistance, metal‐insulator transition, and exchange bias in correlated electron systems. However, the effective manipulation of the electronic phase transition has remained a challenging issue. Here, the reversible control of ferromagnetic phase transition in manganite films through ionic liquid gating is reported. Under different gate voltages, the formation and annihilation of an insulating and magnetically hard phase in the magnetically soft matrix, which randomly nucleates and grows across the film instead of initiating at the surface and spreading to the bottom, is directly observed. This discovery provides a conceptually novel vision for the electric‐field tuning of phase transition in correlated oxides. In addition to its fundamental significance, the realization of a reversible metal‐insulator transition in colossal magnetoresistance materials will also further the development of four‐state memories, which can be manipulated by a combination of electrode gating and the application of a magnetic field. The formation and annihilation of an insulating and magnetically hard phase in the soft magnetic matrix, which randomly nucleates and grows across the film instead of spreading from the surface to the bottom, is directly observed in manganite through ionic liquid gating. The realization of reversible metal‐insulator transition in colossal magnetoresistance materials can lead to the development of four‐state memories.
      PubDate: 2014-09-08T10:33:56.905635-05:
      DOI: 10.1002/adfm.201402007
  • A Highly Sensitive Graphene‐Organic Hybrid Photodetector with a
           Piezoelectric Substrate
    • Authors: Wei‐Chun Tan; Wei‐Heng Shih, Yang Fang Chen
      Pages: n/a - n/a
      Abstract: To create a sensitive photodetector, the transparent and conductive properties of graphene and the optical and photovoltaic properties of poly(3‐hexylthiophene) (P3HT) are combined as a hybrid composite. Based on the inherent nature of the band alignment between graphene and P3HT, the photogenerated holes are able to transfer to the graphene layer and improve the photoresponse to be much better than the traditional layer by layer organic system. Additionally, the graphene is deposited on a piezoelectric Pb(Zr0.2Ti0.8)O3 (PZT) substrate, and the photoresponse of such composite photodetectors is found to be ten times larger than on SiO2 base. It is demonstrated that the electric field of the polarization of piezoelectric substrate helps the spatial separation of photogenerated electrons and holes and promotes the hole doping of graphene to enhance the photoconduction. A detailed investigation of graphene layers, thickness of P3HT and time evolution shows that the composite of graphene and P3HT on PZT can be used as a sensitive photodetector and has potential as an effective solar cell. Moreover, with the replacement of P3HT by a thin layer of bulk heterojunction of polymer and fullerene, the photosensitivity can be further increased by more than one order of magnitude. The application of a piezoelectric substrate (PZT) to enhance (down polarized, D‐PZT) or decrease (up polarized, U‐PZT) the graphene‐organic semiconductor (P3HT) hybrid photodetector compared to that of a silica substrate is reported. The permanent polarization in PZT generates an electric field promoting or decreasing charge transfer behavior of the device.
      PubDate: 2014-09-08T10:31:00.094867-05:
      DOI: 10.1002/adfm.201401421
  • Hybrid White Light Emitting Diode Based on Silicon Nanocrystals
    • Authors: Batu Ghosh; Yoshitake Masuda, Yutaka Wakayama, Yasutaka Imanaka, Jun‐ichi Inoue, Kenjiro Hashi, Kenzo Deguchi, Hideto Yamada, Yoshio Sakka, Shinobu Ohki, Tadashi Shimizu, Naoto Shirahata
      Pages: n/a - n/a
      Abstract: A novel design of white light emitting diodes (WLEDs) emerges to meet the growing global demand for resource sustainability while preserving health and environment. To achieve this goal, a facile method is developed for the chemical synthesis of a luminescent silicon nanocrystal (ncSi) with a large Stokes shift between absorption and emission. The WLED is prepared by a simple spin‐coating method, and contains a hybrid‐bilayer of the ncSi and luminescent polymer in its device active region. Interestingly, a well‐controlled ultrathin ncSi layer on the polymer makes possible to recombine electrons and holes in both layers, respectively. Combining red and blue‐green lights, emitted from the ncSi and the polymer layers, respectively, produces the emission of white electroluminescence. Herein, a hybrid‐WLED with a sufficiently low turn‐on voltage (3.5 V), produced by taking advantages of the large Stokes shift inherent in ncSi, is demonstrated. A novel design of white light emitting diodes emerges to meet the growing global demand for resource sustainability while preserving health and environment. The proposed WLED contains a hybrid bilayer of silicon nanocrystals (ncSi) and luminescent polymer in its device active region, and works at sufficiently low turn‐on voltage (3.5 V) by taking advantages of the large Stokes shift inherent to ncSi.
      PubDate: 2014-09-08T10:30:18.642638-05:
      DOI: 10.1002/adfm.201401795
  • Flexible Cellulose Paper‐based Asymmetrical Thin Film
           Supercapacitors with High‐Performance for Electrochemical Energy
    • Authors: Jin‐Xian Feng; Sheng‐Hua Ye, An‐Liang Wang, Xue‐Feng Lu, Ye‐Xiang Tong, Gao‐Ren Li
      Pages: n/a - n/a
      Abstract: Cellulose paper (CP)‐based asymmetrical thin film supercapacitors (ATFSCs) have been considered to be a novel platform for inexpensive and portable devices as the CP is low‐cost, lightweight, and can be rolled or folded into 3D configurations. However, the low energy density and poor cycle stability are serious bottlenecks for the development of CP‐based ATFSCs. Here, sandwich‐structured graphite/Ni/Co2NiO4‐CP is developed as positive electrode and the graphite/Ni/AC‐CP as negative electrode for flexible and high‐performance ATFSCs. The fabricated graphite/Ni/Co2NiO4‐CP positive electrode shows a superior areal capacitance (734 mF/cm2 at 5 mV/s) and excellent cycling performance with ≈97.6% Csp retention after 15 000 cycles. The fabricated graphite/Ni/AC‐CP negative electrode also exhibits large areal capacitance (180 mF/cm2 at 5 mV/s) and excellent cycling performance with ≈98% Csp retention after 15 000 cycles. The assembled ATFSCs based on the sandwich‐structured graphite/Ni/Co2NiO4‐CP as positive electrode and graphite/Ni/AC‐CP as negative electrode exhibit large volumetric Csp (7.6 F/cm3 at 5 mV/s), high volumetric energy density (2.48 mWh/cm3, 80 Wh/kg), high volumetric power density (0.79 W/cm3, 25.6 kW/kg) and excellent cycle stability (less 4% Csp loss after 20 000 cycles). This study shows an important breakthrough in the design and fabrication of high‐performance and flexible CP‐based electrodes and ATFSCs. Cellulose paper (CP)‐based asymmetrical thin film supercapacitors are assembed by using sandwich‐structured graphite/Ni/Co2NiO4‐CP as positive electrode and graphite/Ni/AC‐CP as negative electrode. The assembed devices exhibit large Csp (7.6 F/cm3 at 5 mV/s), high volumetric energy density (2.48 mWh/cm3, 80 Wh/kg), high volumetric power density (0.79 W/cm3, 25.6 kW/kg), and excellent cycle stability (less 4% Csp loss after 20 000 cycles).
      PubDate: 2014-09-05T15:22:04.532462-05:
      DOI: 10.1002/adfm.201401876
  • The Role of Chlorine in the Formation Process of
           “CH3NH3PbI3‐xClx” Perovskite
    • Authors: Hui Yu; Feng Wang, Fangyan Xie, Wenwu Li, Jian Chen, Ni Zhao
      Pages: n/a - n/a
      Abstract: CH3NH3PbI3‐xClx is a commonly used chemical formula to represent the methylammonium lead halide perovskite fabricated from mixed chlorine‐ and iodine‐containing salt precursors. Despite the rapid progress in improving its photovoltaic efficiency, fundamental questions remain regarding the atomic ratio of Cl in the perovskite as well as the reaction mechanism that leads to its formation and crystallization. In this work we investigated these questions through a combination of chemical, morphological, structural and thermal characterizations. The elemental analyses reveal unambiguously the negligible amount of Cl atoms in the CH3NH3PbI3‐xClx perovskite. By studying the thermal characteristics of methylammonium halides as well as the annealing process in a polymer/perovskite/FTO glass structure, we show that the formation of the CH3NH3PbI3‐xClx perovskite is likely driven by release of gaseous CH3NH3Cl (or other organic chlorides) through an intermediate organometal mixed halide phase. Furthermore, the comparative study on CH3NH3I/PbCl2 and CH3NH3I/PbI2 precursor combinations with different molar ratios suggest that the initial introduction of a CH3NH3+ rich environment is critical to slow down the perovskite formation process and thus improve the growth of the crystal domains during annealing; accordingly, the function of Cl− is to facilitate the release of excess CH3NH3+ at a relatively low annealing temperatures. To understand theformation mechanism of CH3NH3PbI3–xClx perovskite, two testing structures, perovskite (precursor mixture)/FTO and PMMA (polymethyl methacrylate)/perovskite (precursor mixture)/FTO, are designed. The different annealing results of these two structures suggest that the formation of CH3NH3PbI3–xClx perovskite is likely driven by the release of gaseous CH3NH3Clthrough an intermediate organolead mixed halide phase.
      PubDate: 2014-09-05T15:21:25.775277-05:
      DOI: 10.1002/adfm.201401872
  • Dual Bioresponsive Mesoporous Silica Nanocarrier as an “AND”
           Logic Gate for Targeted Drug Delivery Cancer Cells
    • Authors: Xin Chen; Alexander H. Soeriyadi, Xun Lu, Sharon M. Sagnella, Maria Kavallaris, J. Justin Gooding
      Pages: n/a - n/a
      Abstract: Despite the rapid development of drug delivery vehicles that react to a specific biological environment, the complexity of triggering drug release in a particular target area remains an enduring challenge. Here, the engineering of bioresponsive polymer‐mesoporous silica nanoparticles (MSNs) with function akin to an AND logic gate is described. Polycaprolactone (esterase degradable) is immobilized into the core of MSNs while polyacrylic acid (PAA), which is pH responsive, covered the outside of the MSNs to create a PAA‐PCL‐MSNs construct. Fluorescence spectroscopy indicates that the construct releases the payload (doxorubicin, cancer drugs) in the presence of, and only in the presence of, both low pH AND esterase. Confocal microscopy and fluorescence lifetime microscopy (FLIM) demonstrate uptake of the intact construct and subsequent intracellular doxorubicin (DOX) delivery into the nucleus. Further in vitro IC50 studies demonstrate the AND logic gate delivery system results in more than an eightfold efficacy against neuroblastoma (SK‐N‐BE(2)) cells in comparison with normal fibroblasts (MRC‐5). These results demonstrate the utility of MSN‐polymer construct to create an AND gate capable of selectively delivering a drug payload. Logic “AND” gate drug release: Mesoporous silica nanoparticle (MSNs) with an “AND” logic gated provided by dual bioresponsive polymeric system polyacrylic acid (pH responsive) and polycaprolactone (enzyme degradable) for tumor targeting drug delivery nanocarrier. DOX‐loaded PAA‐PCL‐MSNs system is shown to selectively release DOX only with low pH and enzyme presence and results in an eightfold efficacy towards cancer cells compare to healthy cells.
      PubDate: 2014-09-05T03:28:31.550365-05:
      DOI: 10.1002/adfm.201402339
  • Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified
           Phosphonic Acid Self‐Assembled Monolayers
    • Authors: Ilja Lange; Sina Reiter, Michael Pätzel, Anton Zykov, Alexei Nefedov, Jana Hildebrandt, Stefan Hecht, Stefan Kowarik, Christof Wöll, Georg Heimel, Dieter Neher
      Pages: n/a - n/a
      Abstract: Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow for tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers. The tuning of the ZnO work function from 4.1 to 5.7 eV is realized by the application of a variety of phosphonic acid based self‐assembled monolayers (SAMs). This enables the use of ZnO as both the electron‐ and hole‐injecting contact. The homogenous dense packing of the SAMs is thoroughly characterized using a range of complementary techniques.
      PubDate: 2014-09-05T03:28:26.856081-05:
      DOI: 10.1002/adfm.201401493
  • Polar Cation Ordering: A Route to Introducing >10% Bond Strain Into
           Layered Oxide Films
    • Authors: Brittany B. Nelson‐Cheeseman; Hua Zhou, Prasanna V. Balachandran, Gilberto Fabbris, Jason Hoffman, Daniel Haskel, James M. Rondinelli, Anand Bhattacharya
      Pages: n/a - n/a
      Abstract: The 3d transition metal (M) perovskite oxides exhibit a remarkable array of properties, including novel forms of superconductivity, magnetism and multiferroicity. Strain can have a profound effect on many of these properties. This is due to the localized nature of the M 3d orbitals, where even small changes in the M–O bond lengths and M–O–M bond angles produced by strain can be used to tune the 3d– O 2p hybridization, creating large changes in electronic structure. A new route is presented to strain the M–O bonds in epitaxial two‐dimensional perovskite films by tailoring local electrostatic dipolar interactions within every formula unit via atomic layer‐by‐layer synthesis. The response of the O anions to the resulting dipole electric fields distorts the M–O bonds by more than 10%, without changing substrate strain or chemical composition. This distortion is largest for the apical oxygen atoms (Oap), and alters the transition metal valence state via self‐doping without chemical substitution. The cations of a well‐known layered oxide, LaSrNiO4, are re‐arranged in a “polar” structure using molecular beam epitaxy. X‐ray probes reveal that the resulting electrostatic dipoles act on the Ni–O bonds, creating large distortions and changes to hybridization. This “electrostatic bond strain” approach has potential to tailor electronic properties in layered oxides by altering the local bonding without epitaxy or doping.
      PubDate: 2014-09-05T03:28:21.150505-05:
      DOI: 10.1002/adfm.201401077
  • Regular Metal Sulfide Microstructure Arrays Contributed by
           Ambient‐Connected Gas Matrix Trapped on Superhydrophobic Surface
    • Authors: Shasha Wang; Yuchen Wu, Xiaonan Kan, Bin Su, Lei Jiang
      Pages: n/a - n/a
      Abstract: Controlling the position of metal sulfide architectures is prerequisite and facilitates their device applications in solar cells, light‐emitting diodes, and many other optoelectronic fields. Thanks to ambient‐connected gas network trapped upon superhydrophobic surfaces, H2S gas can be continuously transported and reacted with metal ions along solid/liquid/gas triphase contact interface. Therefore, precisely positioning metal sulfide microstructure arrays are generated accordingly. The growth mechanisms as well as influencing factors are investigated to tailor the morphology, structure, and chemical composition of these metal sulfide materials. This interface‐mediated strategy can be widely applied to many other metal sulfides, such as PbS, MnS, Ag2S, and CuS. In particular, heterostructured metal sulfide architectures, such as PbS/CdS concentric microflower arrays, can be generated by stepwise replacement of metal ions inside liquid, exhibiting the advanced applications of this interface‐mediated growth strategy. Owing to ambient‐connected gas network trapped upon superhydrophobic surfaces, H2S gas can be continuously transported and react with metal ions along solid/liquid/gas triphase contact interface, forming precisely positioning metal sulfide microstructure arrays. This strategy can be widely applied to many metal sulfides and heterostructured metal sulfide architectures, such as PbS/CdS concentric microflower arrays, exhibiting the advanced applications of this interface‐mediated growth strategy.
      PubDate: 2014-09-05T03:27:45.080883-05:
      DOI: 10.1002/adfm.201401975
  • A Novel MoSe2–Reduced Graphene Oxide/Polyimide Composite Film for
           Applications in Electrocatalysis and Photoelectrocatalysis Hydrogen
    • Authors: Lingpu Jia; Xiao Sun, Yimin Jiang, Shenjiao Yu, Chunming Wang
      Pages: n/a - n/a
      Abstract: Promising catalytic activity of MoSe2 in the hydrogen evolution reaction (HER) is synthesized on a new reduced graphene oxide/polyimide (rGO/PI) substrate by a simple electrochemical method. The MoSe2 nanoparticles have excellent photo‐responsive properties; the potential difference could reach 0.45 V with the photo‐responsive time just 0.6 s. Furthermore, MoSe2 thin film exhibits superior catalytic activity in the hydrogen evolution reaction (HER). It has a greater cathode current at more positive potential compared to other MoSe2 and MoS2, and the efficiency of H2 evolution is strongly influenced by illumination; this suggests that MoSe2 composite film has good photoelectrocatalysis properties for hydrogen evolution. Besides, both dark and illumination MoSe2 films exhibit extremely high stability in acidic solution as the HER catalytic activity shows no degradation after 100 cycles for two hours. All results indicate that MoSe2–rGO/PI composite film has potential to be a better catalyst for HER. The cathodic current of the MoSe2–rGO/PI composite film hardly decreases at −0.6 V compared to SCE by current density versus time curves, both illuminated and dark, illustrating how it possesses high stability and sufficient cathodic current density. These properties its potential as a better catalyst for hydrogen evolution reaction, and even solar‐driven hydrogen evolution.
      PubDate: 2014-09-05T03:27:39.036407-05:
      DOI: 10.1002/adfm.201401814
  • Novel and Enhanced Optoelectronic Performances of Multilayer
           MoS2–WS2 Heterostructure Transistors
    • Authors: Nengjie Huo; Jun Kang, Zhongming Wei, Shu‐Shen Li, Jingbo Li, Su‐Huai Wei
      Pages: n/a - n/a
      Abstract: Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS2–WS2 heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS2 or WS2. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 103. The planar device also exhibits high field‐effect ON/OFF ratio (>105), high electron mobility of 65 cm2/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS2 or WS2 nanoflake transistors. The results suggest that formation of MoS2–WS2 heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications. Newly designed MoS 2 –WS 2 heterostructures perform novel and enhanced optoelectronic performances. Vertical transistors possess new functionalities such as rectifying, bipolarity, photovoltaic effect, and self‐driven photodetection. Planar devices exhibit superior optoelectronic properties with high field‐effect ON/OFF ratio (>105), electron mobility of 65 cm2/Vs, and photoresponsivity of 1.42 A/W that far exceed the one for their constituents MoS2 or WS2.
      PubDate: 2014-09-05T03:27:33.662463-05:
      DOI: 10.1002/adfm.201401504
  • In Situ Fabrication of Three‐Dimensional Graphene Films on Gold
           Substrates with Controllable Pore Structures for High‐Performance
           Electrochemical Sensing
    • Authors: Lei Shi; Zhenyu Chu, Yu Liu, Wanqin Jin, Nanping Xu
      Pages: n/a - n/a
      Abstract: In this work, novel three‐dimensional graphene films (3D GFs) with controllable pore structures are directly fabricated on gold substrates through the hydrothermal reduction. An interfacial technique of the self‐assembled monolayer is successfully introduced to address the binding issue between the graphene film and substrate. Adscititious silica spheres, serving as new connection centers, effectively regulate the dimensions of framework in graphene films, and secondary pore structures are produced once removing the spheres. Based on hierarchically porous 3D GFs with large surface area, excellent binding strength, high conductivity, and distinct interfacial micro‐environments, selected examples of electrochemical aptasensors are constructed for the assay of adenosine triphosphate (ATP) and thrombin (Tob) respectively. Sensitive ATP and Tob aptasensors, with high selectivity, excellent stability, and promising potential in real serum sample analysis, are established on 3D GFs with different structures. The results demonstrate that the surface area, as well as interfacial micro‐environments, plays a critical role in the molecular recognition. The developed reliable and scalable protocol is envisaged to become a general path for in situ fabrication of more graphene films and the as‐synthesized 3D GFs would open up a wide horizon for potential applications in electronic and energy‐related systems. Three dimensional graphene film s (GFs) with controllable pore structures are directly fabricated on the gold substrate through a facile and reliable approach. The resulting GFs exhibit large surface area, excellent binding strength and high conductivity, which will enable many advanced applications in electronic and energy‐related systems. As examples, novel electrochemical aptasensors with high performance are constructed in this work.
      PubDate: 2014-09-05T03:27:12.581202-05:
      DOI: 10.1002/adfm.201402095
  • Inhibition of Cancer Cell Migration by Gold Nanorods: Molecular Mechanisms
           and Implications for Cancer Therapy
    • Authors: Teng Zhou; Meifang Yu, Bo Zhang, Liming Wang, Xiaochun Wu, Hejiang Zhou, Yipeng Du, Junfeng Hao, Yaping Tu, Chunying Chen, Taotao Wei
      Pages: n/a - n/a
      Abstract: Gold nanorods have received much attention because of their distinct physicochemical properties and promising applications in bioimaging, biosensing, drug delivery, photothermal therapy, and optoelectronic devices. However, little is known regarding their effect on tumor metastasis. In the present investigation, serum protein‐coated gold nanorods (AuNRs) at low concentrations is shown to exhibit no apparent effects on the viability and proliferation of three different metastatic cancer cell lines, that is, MDA‐MB‐231 human breast cancer cells, PC3 human prostate cancer cells, and B16F10 mouse melanoma cells, but effectively inhibit their migration and invasion in vitro. Quantitative proteomics and real‐time PCR array analyses indicate that exposure of cells to AuNRs can down‐regulate the expression of diverse energy generation‐related genes, which accounts for their inhibition of mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis. The impairment of OXPHOS and glycolysis results in a distinctive reduction of ATP production and subsequent inhibition of F‐actin cytoskeletal assembly, which is crucial for the migration and invasion of cancer cells. The inhibitory effect of AuNRs on cancer cell migration is also confirmed in vivo. Taken together, the unique mechanism in inhibiting cancer cell migration by AuNRs might provide a new approach to specific cancer therapeutic treatment. Inhibitory effects of gold nanorods on cancer cell migration and the underlying mechanisms are revealed. After endocytosed by cancer cells, gold nanorods down‐regulate the expression of energy generation‐related genes, decrease mitochondrial oxidative phosphorylation and glycolysis, reduce ATP synthesis, impair F‐actin cytoskeletal assembly and lamellipodia formation, and finally inhibit cancer cell migration.
      PubDate: 2014-09-05T03:15:30.607037-05:
      DOI: 10.1002/adfm.201401642
  • Delivery of iPS‐NPCs to the Stroke Cavity within a Hyaluronic Acid
           Matrix Promotes the Differentiation of Transplanted Cells
    • Authors: Jonathan Lam; William E. Lowry, S. Thomas Carmichael, Tatiana Segura
      Pages: n/a - n/a
      Abstract: Stroke is the leading cause of adult disability with ≈80% being ischemic. Stem cell transplantation has been shown to improve functional recovery. However, the overall survival and differentiation of these cells is still low. The infarct cavity is an ideal location for transplantation as it is directly adjacent to the highly plastic peri‐infarct region. Direct transplantation of cells near the infarct cavity has resulted in low cell viability. Here, neural progenitor cells derived from induce pluripotent stem cells (iPS‐NPC) are delivered to the infarct cavity of stroked mice encapsulated in a hyaluronic acid hydrogel matrix to protect the cells. To improve the overall viability of transplanted cells, each step of the transplantation process is optimized. Hydrogel mechanics and cell injection parameters are investigated to determine their effects on the inflammatory response of the brain and cell viability, respectively. Using parameters that balanced the desire to keep surgery invasiveness minimal and cell viability high, iPS‐NPCs are transplanted to the stroke cavity of mice encapsulated in buffer or the hydrogel. While the hydrogel does not promote stem cell survival one week post‐transplantation, it does promote differentiation of the neural progenitor cells to neuroblasts. Hydrogels can be used to deliver neural progenitor cells to the brain post‐stroke. Comprehensively studying the parameters involved in the transplantation process allows to keep cells viable in the infarct cavity post‐transplantation. Further, delivering induced pluripotent cell derived neural progenitors encapsulated in the hydrogel promotes differentiation to a neuronal phenotype compared to a cell only condition.
      PubDate: 2014-09-05T00:00:00-05:00
      DOI: 10.1002/adfm.201401483
  • Competitive Absorption and Inefficient Exciton Harvesting: Lessons Learned
           from Bulk Heterojunction Organic Photovoltaics Utilizing the Polymer
           Acceptor P(NDI2OD‐T2)
    • Authors: Zhi Li; Jason D. A. Lin, Hung Phan, Alexander Sharenko, Christopher M. Proctor, Peter Zalar, Zhihua Chen, Antonio Facchetti, Thuc‐Quyen Nguyen
      Pages: n/a - n/a
      Abstract: Organic solar cells utilizing the small molecule donor 7,7′‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(6‐fluoro‐4‐(5′‐hexyl‐[2,2′‐bithiophen]‐5‐yl)benzo[c][1,2,5] thiadiazole) (p‐DTS(FBTTh2)2 and the polymer acceptor poly{[N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)}(P(NDI2OD‐T2)) are investigated and a power conversion efficiency of 2.1% is achieved. By systematic study of bulk heterojunction (BHJ) organic photovoltaic (OPV) quantum efficiency, film morphology, charge transport and extraction and exciton diffusion, the loss processes in this blend is revealed compared to the blend of [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) and the same donor. An exciton diffussion study using Förster resonant energy transfer (FRET) shows the upper limit of the P(NDI2OD‐T2) exciton diffusion length to be only 1.1 nm. The extremely low exciton diffusion length of P(NDI2OD‐T2), in combination with the overlap in donor and acceptor absorption, is then found to significantly limit device performance. These results suggest that BHJ OPV devices utilizing P(NDI2OD‐T2) as an acceptor material will likely be limited by its low exciton diffusion length compared to devices utilizing functionalized fullerene acceptors, especially when P(NDI2OD‐T2) significantly competes with the donor molecule for photon absorption. Organic solar cells based on a small molecule donor and the polymer acceptor P(NDI2OD‐T2) are fabricated and investigated. Through a comprehensive study of the optical and electronic properties of the blend films, the poor exciton diffusion length of P(NDI2OD‐T2) is identified as the primary cause of the poor performance. In order to make non‐fullerene acceptors competitive, the exciton diffusion length must be considered.
      PubDate: 2014-09-02T12:55:06.713715-05:
      DOI: 10.1002/adfm.201401367
  • Flexible Inorganic Piezoelectric Acoustic Nanosensors for Biomimetic
           Artificial Hair Cells
    • Authors: Hyun Soo Lee; Juyong Chung, Geon‐Tae Hwang, Chang Kyu Jeong, Youngdo Jung, Jun‐Hyuk Kwak, Hanmi Kang, Myunghwan Byun, Wan Doo Kim, Shin Hur, Seung‐Ha Oh, Keon Jae Lee
      Pages: n/a - n/a
      Abstract: For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic‐based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone‐based membrane (SM) mimics the function of the natural basilar membrane for frequency selectivity, and a flexible iPANS is fabricated on the SM utilizing a laser lift‐off technology to overcome the brittle characteristics of inorganic piezoelectric materials. The vibration amplitude vs piezoelectric sensing signals are theoretically examined based on the experimental conditions by finite element analysis. The SM is successful at separating the audible frequency range of incoming sound, vibrating distinctively according to varying locations of different sound frequencies, thus allowing iPANS to convert tiny vibration displacement of ≈15 nm into an electrical sensing output of ≈55 μV, which is close to the simulation results presented. This conceptual iPANS of flexible inorganic piezoelectric materials sheds light on the new fields of nature‐inspired biomimetic systems using inherently high piezoelectric charge constants. The new concept of a biomimetic artificial hair cell using a flexible inorganic piezoelectric acoustic nanosensor (iPANS) is presented. A highly sensitive flexible piezoelectric sensor that responds to sound‐driven vibrations of a thin silicone membrane is fabricated using a laser lift‐off process. The iPANS shows remarkable capability to sense tiny vibrations caused by an external sound wave.
      PubDate: 2014-09-02T12:53:56.870503-05:
      DOI: 10.1002/adfm.201402270
  • Spectroscopic Evaluation of Mixing and Crystallinity of Fullerenes in Bulk
    • Authors: Anne A. Y. Guilbert; Malte Schmidt, Annalisa Bruno, Jizhong Yao, Simon King, Sachetan M. Tuladhar, Thomas Kirchartz, M. Isabel Alonso, Alejandro R. Goñi, Natalie Stingelin, Saif A. Haque, Mariano Campoy‐Quiles, Jenny Nelson
      Pages: n/a - n/a
      Abstract: The microstructure of blend films of conjugated polymer and fullerene, especially the degree of mixing and crystallization, impacts the performance of organic photovoltaic devices considerably. Mixing and crystallization affect device performance in different ways. These phenomena are not easy to screen using traditional methods such as imaging. In this paper, the amorphous regiorandom poly(3‐hexylthiophene) is blended with the potentially crystalline fullerene [6,6]‐phenyl‐C61‐butyric acid methyl ester PCBM and the amorphous bis‐adduct. First, the degree of mixing of polymer: fullerene blends is evaluated using UV–Vis absorption, steady‐state and ultra‐fast photoluminescence spectroscopy. The blue‐shift of the polymer emission and absorption onset are used in combination with the saturation of the polymer emission decay time upon fullerene addition in order to infer the onset of aggregation of the blends. Second, the crystallinity of the fullerene is probed using variable angle spectroscopic ellipsometry (VASE), electroluminescence and photoluminescence spectroscopy. It is shown that the red‐shift of charge transfer emission in the case of PCBM based blends cannot be explained solely by a variation of optical dielectric constant as probed by VASE. A combination of optical spectroscopy techniques, therefore, allows to probe the degree of mixing and can also distinguish between aggregation and crystallization of fullerenes. It is demonstrated that a combination of optical spectroscopy techniques such as UV–Vis absorption, steady‐state and ultra‐fast photoluminescence, electro­luminescence, and variable angle spectroscopic ellipsometry can be used to probe the degree of mixing of polymer:fullerene blends but also distinguishes between aggregation and crystallization of fullerenes. Both degree of mixing and crystallization have a huge impact on organic photo­voltaic device performance.
      PubDate: 2014-09-02T12:53:53.884309-05:
      DOI: 10.1002/adfm.201401626
  • Hierarchical Ordering of Quantum Dots and Liquid with Tunable
           Super‐Periodicity into High Aspect Ratio Moiré Superlattice
    • Authors: Soo‐Yeon Cho; Hwan‐Jin Jeon, Jong‐Seon Kim, Jong Min Ok, Hee‐Tae Jung
      Pages: n/a - n/a
      Abstract: In this work, a new approach for construction of high aspect ratio complex moiré superlattice structure with versatile super‐periodicity is developed using the moiré fringe and secondary sputtering lithography. Wide assortments of high aspect ratio complex superstructures having different features on a 10 nm scaled wall are easily fabricated from simple starting components. More important is the finding of a new microscale phenomenon, consisting in trapping fluids in the centres of the moiré hexagonal fringes, as the consequence of the modulation of local hydrophilicty of the pattern. Using this phenomenon, target materials can be selectively and hierarchically confined within the moiré superlattice. Hierarchical nanoparticles (QDs) ordering with tunable super‐periodicity into selective area of moiré superlattice are successfully demonstrated by just solution‐casting of toluene based QD solution on patterned surfaces. This observation is expected to elucidate the key morphological factors that govern the physics of liquid behavior on a complex patterned substrate. Accordingly, in the near future, this facile approach for complex superlattice structure could be used as optical substrate for imaging applications and open interesting perspectives in the assembly processes and the handling of the nano‐microsized particles. A powerful new method is reported for fabricating complex lateral superlattice structures with 10 nm resolution, using the moiré fringe and secondary sputtering lithography. A large assortment of moiré superstructures can be easily fabricated by a simple rotation of the periodic layer. These superlattice structures widen the range of application of moiré patterns to not only the fields of photonics or optical characterization tools, but also to functional nano‐materials trapping and ordering.
      PubDate: 2014-09-01T09:35:57.472943-05:
      DOI: 10.1002/adfm.201401981
  • Ultra‐Thin Self‐Assembled Protein‐Polymer Membranes: A
           New Pore Forming Strategy
    • Authors: Patrick van Rijn; Murat Tutus, Christine Kathrein, Nathalie C. Mougin, Hyunji Park, Christopher Hein, Marco P. Schürings, Alexander Böker
      Pages: n/a - n/a
      Abstract: Self‐assembled membranes offer a promising alternative for conventional membrane fabrication, especially in the field of ultrafiltration. Here, a new pore‐making strategy is introduced involving stimuli responsive protein‐polymer conjugates self‐assembled across a large surface area using drying‐mediated interfacial self‐assembly. The membrane is flexible and assembled on porous supports. The protein used is the cage protein ferritin and resides within the polymer matrix. Upon denaturation of ferritin, a pore is formed which intrinsically is determined by the size of the protein and how it resides in the matrix. Due to the self‐assembly at interfaces, the membrane constitutes of only one layer resulting in a membrane thickness of 7 nm on average in the dry state. The membrane is stable up to at least 50 mbar transmembrane pressure, operating at a flux of about 21 000–25 000 L m−2 h−1 bar−1 and displayed a preferred size selectivity of particles below 20 nm. This approach diversifies membrane technology generating a platform for “smart” self‐assembled membranes. Self‐assembled membranes offer a promising alternative for conventional membrane fabrication, especially in the field of ultrafiltration. Here a new pore‐making strategy is introduced involving stimuli responsive protein‐polymer conjugates self‐assembled across a large surface area using drying‐mediated interfacial self‐assembly. The membrane is flexible and assembled on porous supports. This approach diversifies membrane technology generating a platform for “smart” self‐assembled membranes.
      PubDate: 2014-09-01T09:35:06.33507-05:0
      DOI: 10.1002/adfm.201401825
  • Nanostructured Pseudocapacitors Based on Atomic Layer Deposition of V2O5
           onto Conductive Nanocrystal‐based Mesoporous ITO Scaffolds
    • Authors: Iris E. Rauda; Veronica Augustyn, Laura C. Saldarriaga‐Lopez, Xinyi Chen, Laura T. Schelhas, Gary W. Rubloff, Bruce Dunn, Sarah H. Tolbert
      Pages: n/a - n/a
      Abstract: Solution processing of colloidal nanocrystals into porous architectures using block co‐polymer templating offers a simple yet robust route to construct materials with open porosity and high surface area. These features, when realized in materials that show efficient redox activity and good conductivity, should be ideal for electrochemical energy storage because they allow for efficient electrolyte diffusion and ample surface and near‐surface redox reactions. Here, a route to synthesize nanoporous pseudocapacitors is presented using preformed ITO nanocrystals to make a conductive scaffold, coated with a conformal layer of vanadia deposited using atomic layer deposition (ALD). Two vanadia thicknesses are deposited, 2 and 7 nm, to examine the kinetics of Li+ diffusion into vanadia in a system where all other chemical and structural parameters are fixed. Porosity measurements show that the internal surface area of 2 nm vanadia samples is fully accessible; whereas for the 7 nm vanadia, there is some pore blockage that limits electrolyte diffusion. Despite this fact, composites with both thick and thin vanadia layers show high levels of pseudocapacitance, indicating fast diffusion of Li+ through even the 7 nm thick vanadia. This work thus sets a minimum accessible length‐scale of 7 nm for intercalation pseudocapacitance in orthorhombic V2O5. Nanostructured pseudocapacitors are created by coating a conductive scaffold, made through solution‐phase templating of ITO nanocrystals, with a conformal layer of vanadium oxide. The materials combine intrinsic electrical conductivity, porosity for solvent diffusion, and short solid‐state Li+ diffusion distance. By tuning the vanadia thickness, redox reactions are dominantly pseudocapacitive for vanadia layers up to 7 nm thickness.
      PubDate: 2014-09-01T09:34:25.39991-05:0
      DOI: 10.1002/adfm.201401284
  • Functional Selenium Nanoparticles Enhanced Stem Cell Osteoblastic
           Differentiation through BMP Signaling Pathways
    • Authors: Chuping Zheng; Jinsheng Wang, Yanan Liu, Qianqian Yu, Ying Liu, Ning Deng, Jie Liu
      Pages: n/a - n/a
      Abstract: Stem cells have generated a great deal of excitement in tissue engineering and regenerative medicine, and it is important to understand the interaction mechanisms between nanomaterials and mesenchymal stem cells (MSCs) for biomedical applications. In this study, ruthenium (II) functional selenium nanoparticles (Ru@Se) are used for stem cell research. Specifically, Ru@Se are compared with citric acid selenium nanoparticles (Cit@Se)to identify their effects on MSCs differentiation and associated molecular mechanism. These data suggest that the effective adsorbing abilities of Ru@Se and Cit@Se allow them to act as preconcentration materials for osteogenic chemical inducers, which accelerates MSCs differentiation into osteoblasts. Further results suggest that selenium nanoparticles enhance the differentiation of MSCs toward osteogenic lineage over adipocytes by promoting osteogenic transcription and attenuating adipogenic transcription. Ru@Se and Cit@Se exert these effects by activating Smad‐dependent BMP signaling pathway, which regulates the expression of relevant genes to induce osteogenic differentiation. Ru@Se, a good biocompatible nanoparticle, can be uptaken by human umbilical cord mesenchymal stem cells and can enhance the osteogenic differentiation of HUMSCs through the Smad‐dependent BMP signaling pathway. The activation of BMP pathway induces the Smad1/5 protein phosphorylation. p‐Smad1/5 combines with Smad 4 and translocates into the nucleus to promote the expression of the osteogenesis specific genes, such as BMP, OCN, OPN, thus driving HUCMSCs to differentiate into osteoblasts.
      PubDate: 2014-09-01T09:34:21.235163-05:
      DOI: 10.1002/adfm.201401263
  • Ultrasmall Graphene Oxide Supported Gold Nanoparticles as Adjuvants
           Improve Humoral and Cellular Immunity in Mice
    • Authors: Yuhua Cao; Yufei Ma, Mengxin Zhang, Haiming Wang, Xiaolong Tu, He Shen, Jianwu Dai, Huichen Guo, Zhijun Zhang
      Pages: n/a - n/a
      Abstract: Adjuvants play an important role in vaccines. Alum and MF59 are two dominant kinds of adjuvants used in humans. Both of them, however, have limited capacity to generate the cellular immune response required for vaccines against cancers and viral diseases. It is desirable to develop new and efficient adjuvants with the aim of improving the cellular immune response against the antigen. Here, the feasibility and efficiency of ultrasmall graphene oxide supported gold nanoparticles (usGO‐Au) as a new immune adjuvant to improve immune responses are explored. usGO‐Au is obtained from reduction of chloroauric acid using usGO and then decorated with ovalbumin (OVA, a model antigen) through physical adsorption to construct usGO‐Au@OVA. As the results show, the as‐synthesized usGO‐Au@OVA can efficiently stimulate RAW264.7 cells to secrete tumor necrosis factor‐α (TNF‐α), a mediator for cellular immune response. In vivo studies demonstrate that usGO‐Au@OVA can also promote robust OVA specific antibody response, CD8+ T cells proliferation, and different cytokines secretion. The results indicate that using usGO‐Au as an adjuvant can stimulate potent humoral and cellular immune responses against antigens, which may promote better understanding of cellular immune response and facilitate potential applications for cancer and viral vaccines. Gold nanoparticles in situ grown on ultra­small graphene oxide (usGO) are decorated with antigen ovalbumin (OVA) through physically adsorbing and Au‐S bonding. The usGO‐Au@OVA composites can efficiently stimulate RAW264.7 cells to secrete tumor necrosis factor‐α and promote an OVA‐specific antibody response, CD8+ T cells proliferation, and different cytokines secretion, thus demonstrating the capability to promote potent humoral and cellular immune responses.
      PubDate: 2014-09-01T09:30:57.438514-05:
      DOI: 10.1002/adfm.201401358
  • Cactus Stem Inspired Cone‐Arrayed Surfaces for Efficient Fog
    • Authors: Jie Ju; Xi Yao, Shuai Yang, Lin Wang, Ruize Sun, Yaxu He, Lei Jiang
      Pages: n/a - n/a
      Abstract: With the increasing world population and the rapid development of the global industry, clean water is becoming scarcer and scarcer. Means of translating latent water in fog to dominant available water, i.e., fog collection, therefore becomes highly desirable. Previously, it was demonstrated that the cactus O. Microdasys has an integrated fog collection system arising from the evenly distributed clusters of spines and trichomes on the cactus stem. Here, it is reported that the intersite of the clusters on the cactus stem is densely covered with cones, which are also capable of collecting water from fog efficiently. Inspired by these cones, using a simple method combining mechanical perforating and template replica technology, polydimethylsiloxane (PDMS) cone arrays are fabricated with different arrangements and the one in hexagonal arrangement proves to be more efficient due to the more turbulent flow filed around the staggered cones and the rapid directional movement of water drops along each cone. This investigation opens up new avenue to collect water efficiently and may also provide clues to research about dust filtering and smog removal, which is attracting increasing attention worldwide. The intersite of clusters of spines on a cactus stem is found to be densely covered with cones, which can collect fog efficiently. Inspired by this, artificial cones are fabricated with different arrangements using mechanical perforation followed by template replication. The as‐prepared surface, which has hexagonally arranged cones, is proven to be efficient at collecting fog arising from the turbulent fog flow around the cones and the directional drop movement along the cones.
      PubDate: 2014-09-01T09:29:38.169707-05:
      DOI: 10.1002/adfm.201402229
  • Multimodal Magneto‐Plasmonic Nanoclusters for Biomedical
    • Authors: Chun‐Hsien Wu; Jason Cook, Stanislav Emelianov, Konstantin Sokolov
      Pages: n/a - n/a
      Abstract: Multimodal nanostructures can help solve many problems in the biomedical field including sensitive molecular imaging, highly specific therapy, and early cancer detection. However, the synthesis of densely packed, multicomponent nanostructures with multimodal functionality represents a significant challenge. Here, a new type of hybrid magneto‐plasmonic nanoparticles is developed using an oil‐in‐water microemulsion method. The nanostructures are synthetized by self‐assembly of primary 6 nm iron oxide core‐gold shell particles resulting into densely packed spherical nanoclusters. The dense packing of primary particles does not change their superparamagnetic behavior; however, the close proximity of the constituent particles in the nanocluster leads to strong near‐infrared (NIR) plasmon resonances. The synthesis is optimized to eliminate nanocluster cytotoxicity. Immunotargeted nanoclusters are also developed using directional conjugation chemistry through the Fc antibody moiety, leaving the Fab antigen recognizing region available for targeting. Cancer cells labeled with immunotargeted nanoclusters produce a strong photoacoustic signal in the NIR that is optimum for tissue imaging. Furthermore, the labeled cells can be efficiently captured using an external magnetic field. The biocompatible magneto‐plasmonic nanoparticles can make a significant impact in development of point‐of‐care assays for detection of circulating tumor cells, as well as in cell therapy with magnetic cell guidance and imaging monitoring. A new generation of hybrid magneto‐plasmonic nanoparticles is developed by utilizing an oil‐in‐water microemulsion method. The nanoparticles combine a high density of magnetic and plasmonic functionalities together with biocompatibility and molecular targeting capability that provide a promising tool for sensitive and selective cancer detection and other biomedical applications.
      PubDate: 2014-09-01T09:29:36.172488-05:
      DOI: 10.1002/adfm.201401806
  • A Top Coat with Solvent Annealing Enables Perpendicular Orientation of
           Sub‐10 nm Microdomains in Si‐Containing Block Copolymer Thin
    • Authors: Eunjin Kim; Wonjung Kim, Kwang Hee Lee, Caroline A. Ross, Jeong Gon Son
      Pages: n/a - n/a
      Abstract: Achieving sub‐10 nm high‐aspect‐ratio patterns from diblock copolymer self‐assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high‐χ copolymer typically have very different surface energies, favoring in‐plane microdomain orientations. A fully perpendicular orientation of a high‐χ block copolymer, poly(styrene‐block‐dimethylsiloxane) (PS‐b‐PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through‐thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of micro­domains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film. A top coat layer in the solvent annealing system can be a general approach for perpendicular orientation of microdomains in high‐interaction parameter (χ) block copolymer microdomains. They simultaneously employ top surface neutrality and sufficient film thickness for the control of the solvent concentration gradient and evaporation rate.
      PubDate: 2014-09-01T09:29:31.172637-05:
      DOI: 10.1002/adfm.201401678
  • Drug Delivery: Synergistic Enhancement of Lung Cancer Therapy Through
           Nanocarrier‐Mediated Sequential Delivery of Superantigen and Tyrosin
           Kinase Inhibitor (Adv. Funct. Mater. 35/2014)
    • Authors: Da Li; Yongbin Li, Haibo Xing, Junling Guo, Yuan Ping, Guping Tang
      Pages: 5457 - 5457
      Abstract: Supramolecular cationic polymers, developed by Y. Ping, G. Tang, and co‐workers on page 5482, are designed for the sequential delivery of immunotherapeutic agents and molecular targeted drugs to fight lung cancer. This new therapeutic modality combines the advantages of superantigens to activate antitumor immunity and the specificity feature of tyrosine kinase inhibitors to selectively induce tumor cell apoptosis, and reveals a synergistic effect on tumor inhibition over mouse models with lung carcinoma xenografts. The supramolecular cationic polymers can potentially be used for treating a wide spectrum of cancers.
      PubDate: 2014-09-11T12:57:48.826653-05:
      DOI: 10.1002/adfm.201470230
  • Hydrophobic Surfaces: Trilevel‐Structured Superhydrophobic Pillar
           Arrays with Tunable Optical Functions (Adv. Funct. Mater. 35/2014)
    • Authors: Sanghyuk Wooh; Jai Hyun Koh, Soojin Lee, Hyunsik Yoon, Kookheon Char
      Pages: 5458 - 5458
      Abstract: On page 5550, H. Yoon, K. Char, and colleagues demonstrate a superhydrophobic surface with various optical functions. The trilevel mesoporous structures fabricated by soft imprinting method show outstanding water repelling properties with high transparency in visible. In addition, various optical functions such as photochromism are realized by incorporating different dyes inside the mesoporous structure.
      PubDate: 2014-09-11T12:57:48.681696-05:
      DOI: 10.1002/adfm.201470231
  • Contents: (Adv. Funct. Mater. 35/2014)
    • Pages: 5459 - 5463
      PubDate: 2014-09-11T12:57:49.673332-05:
      DOI: 10.1002/adfm.201470232
  • Functionalized TiO2 Based Nanomaterials for Biomedical Applications
    • Authors: Shuilin Wu; Zhengyang Weng, Xiangmei Liu, K.W. K. Yeung, Paul. K. Chu
      Pages: 5464 - 5481
      Abstract: As baby boomers age, diabetes mellitus, cancer, osteoarthritis, cardiovascular diseases, and orthopedic disorders are more widespread and the demand for better biomedical devices and functional biomaterials is increasing rapidly. Owing to the good biocompatibility, chemical stability, catalytic efficiency, plasticity, mechanical properties, as well as strength‐to‐weight ratio, titanium dioxide (TiO2) based nanostructured materials are playing important roles in tissue reconstruction and diagnosis of these diseases. Here, recent advance in the research of nanostructured TiO2 based biomaterials pertaining to bone tissue engineering, intravascular stents, drug delivery systems, and biosensors is described. TiO2 based nanomaterials with various structures have been widely used for a variety of biomedical applications ranging from tissue engineering to diseases diagnosis systems. Here, recent advances pertaining to nanostructured TiO2 in four important areas are reviewed, namely bone scaffolds, intravascular stents, drug delivery systems, and biosensors.
      PubDate: 2014-07-09T10:52:58.458703-05:
      DOI: 10.1002/adfm.201400706
  • Synergistic Enhancement of Lung Cancer Therapy Through
           Nanocarrier‐Mediated Sequential Delivery of Superantigen and Tyrosin
           Kinase Inhibitor
    • Authors: Da Li; Yongbin Li, Haibo Xing, Junling Guo, Yuan Ping, Guping Tang
      Pages: 5482 - 5492
      Abstract: Gefitinib (GFT) and other tyrosine kinase inhibitors (TKIs) have been widely used for the treatment of advanced or metastatic lung cancer due to their reduced side effects when compared to classic cytotoxic chemotherapeutic agents. However, both intrinsic and acquired resistance often hinders the effectiveness of TKIs. Based on recent findings that the outcome of chemotherapy can be influenced by the host immune system at multiple levels, an exploration of whether activating antitumor immunity improves the efficacy of the targeted cancer therapy of TKIs is undertaken. To this end, a cationic carrier is used to deliver superantigen and GFT in a simultaneous or sequential manner. The sequential delivery of superantigen and GFT can significantly enhance T cell immunity, promote cytokine production, inhibit tumor growth, and prolong survival time in tumor models with lung carcinoma xenografts. Most importantly, dual sequential treatment reveals a synergistic effect on tumor inhibition, which is much more effective than the monotherapy of either GFT or pTSA, as well as the combined treatment through simultaneous codelivery of pTSA and GFT together. This study demonstrates the important contribution of immunotherapy to targeted molecular therapy and opens up new possibilities for treating a wide spectrum of cancers. Sequential delivery of superantigen and tryrosin kinase inhibitor by nanocarriers is proven to synergistically promote lung cancer therapy. The new therapeutic modality combines the advantages of superantigens to activate antitumor immunity with the specificity feature of tyrosine kinase inhibitors to selectively induce tumor cell apoptosis. This proof‐of‐concept study defines a unique strategy of effective lung cancer therapy for future clinical translation.
      PubDate: 2014-06-20T02:01:56.498956-05:
      DOI: 10.1002/adfm.201400456
  • Quartz Films: Water‐Induced Phase Separation Forming Macrostructured
           Epitaxial Quartz Films on Silicon (Adv. Funct. Mater. 35/2014)
    • Authors: Glenna L. Drisko; Adrian Carretero‐Genevrier, Martí Gich, Jaume Gàzquez, Djawhar Ferrah, David Grosso, Cédric Boissière, Juan Rodriguez‐Carvajal, Clément Sanchez
      Pages: 5493 - 5493
      Abstract: The combination of sol‐gel chemistry and epitaxial growth provides direct access to the integration of piezoelectric macroporous quartz, epitaxially grown on (100)‐silicon substrates. A. Carretero‐Genevrier and co‐workers demonstrate on page 5494 that the interplay between temperature, humidity, catalyst content, and epitaxial growth plays a key role for the bottom‐up fabrication of macroporous quartz on silicon substrates.
      PubDate: 2014-09-11T12:57:49.573463-05:
      DOI: 10.1002/adfm.201470233
  • Water‐Induced Phase Separation Forming Macrostructured Epitaxial
           Quartz Films on Silicon
    • Authors: Glenna L. Drisko; Adrian Carretero‐Genevrier, Martí Gich, Jaume Gàzquez, Djawhar Ferrah, David Grosso, Cédric Boissière, Juan Rodriguez‐Carvajal, Clément Sanchez
      Pages: 5494 - 5502
      Abstract: Quartz has been widely used as a bulk material in optics, the microelectronic industry, and sensors. The nanostructuring and direct integration of oriented quartz crystals onto a semiconductor platform has proven to be challenging. However, here, a new approach is presented to integrate epitaxial quartz films with macroperforations within the range of 500 nm and 1 μm using chemical solution deposition. This method constitutes an appealing approach to develop piezoelectric mass sensors with enhanced resonance frequencies due to the thickness reduction. Perforated quartz films on (100)‐silicon are prepared from amorphous silica films deposited via dip‐coating and doped with metal cations that catalyze quartz crystallization. The metal cations are also active in the formation of the macroperforations, which arise due to a phase separation mechanism. Cationic surfactant–anion–metal cation assemblies stabilize droplets of water, creating an indentation in the hydrophilic silica matrix which remains after solvent evaporation. Many cations induce phase separation, including Li+, Na+, Sr2+, Mn2+, Fe2+/Fe3+, Ca2+, Ce3+ and La3+ but only the Sr2+ and Ca2+ cations in this series induce the epitaxial growth of α‐quartz films under the conditions studied. The combination of sol–gel chemistry and epitaxial growth opens new opportunities for the integration of patterned quartz on silicon. Macroporous piezoelectric epitaxial quartz films on (100)‐silicon are directly obtained from amorphous silica films deposited through dip‐coating and doped with metal cations to catalyze quartz crystallization. This process involves a novel silica phase separation, allowing the structuring of quartz. The piezoelectric functionality of films is preserved within the macroporosity, providing large scope for nanosized quartz piezoelectrics.
      PubDate: 2014-07-16T16:43:30.41851-05:0
      DOI: 10.1002/adfm.201401066
  • Enhancing the Charge Transport in Solution‐Processed Perylene
           Di‐imide Transistors via Thermal Annealing of Metastable Disordered
    • Authors: Laura Ferlauto; Fabiola Liscio, Emanuele Orgiu, Norberto Masciocchi, Antonietta Guagliardi, Fabio Biscarini, Paolo Samorì, Silvia Milita
      Pages: 5503 - 5510
      Abstract: The introduction of side chains in π‐conjugated molecules is a design strategy widely exploited to increase molecular solubility thus improving the processability, while directly influencing the self‐assembly and consequently the electrical properties of thin films. Here, a multiscale structural analysis performed by X‐ray diffraction, X‐ray reflectivity, and atomic force microscopy on thin films of dicyanoperylene molecules decorated with either linear or branched side chains is reported. The substitution with asymmetric branched alkyl chains allows obtaining, upon thermal annealing, field‐effect transistors with enhanced transport properties with respect to linear alkyl chains. Branched chains induce molecular disorder during the film growth from solution, effectively favouring 2D morphology. Post‐deposition thermal annealing leads to a structural transition towards the bulk‐phase for molecules with branched chains, still preserving the 2D morphology and allowing efficient charge transport between crystalline domains. Conversely, molecules with linear chains self‐assemble into 3D islands exhibiting the bulk‐phase structure. Upon thermal annealing, these 3D islands keep their size constant and no major changes are observed in the organic field effect transistor characteristics. These findings demonstrate that the disorder generated by the asymmetric branched chains when the molecule is physisorbed in thin film can be instrumental for enhancing charge transport via thermal annealing. Substituting a dicyanoperylene molecule with asymmetric branched alkyl chains is revealed to be an effective strategy for obtaining, upon thermal annealing, field‐effect transistors with enhanced transport properties with respect to linear alkyl chains.
      PubDate: 2014-07-08T13:15:28.624835-05:
      DOI: 10.1002/adfm.201400789
  • B‐doped Carbon Coating Improves the Electrochemical Performance of
           Electrode Materials for Li‐ion Batteries
    • Authors: Cong Wang; Ziyang Guo, Wei Shen, Qunjie Xu, Haimei Liu, Yonggang Wang
      Pages: 5511 - 5521
      Abstract: An evolutionary modification approach, boron doped carbon coating, is initially used to improve the electrochemical properties of electrode materials of lithium‐ion batteries, such as Li3V2(PO4)3, and demonstrates apparent and significant modification effects. Based on the precise analysis of X‐ray photoemission spectroscopy results, Raman spectra, and electrochemical impedance spectroscopy results for various B‐doped carbon coated Li3V2(PO4)3 samples, it is found that, among various B‐doping types (B4C, BC3, BC2O and BCO2), the graphite‐like BC3 dopant species plays a huge role on improving the electronic conductivity and electrochemical activity of the carbon coated layer on Li3V2(PO4)3 surface. As a result, when compared with the bare carbon coated Li3V2(PO4)3, the electrochemical performances of the B‐doped carbon coated Li3V2(PO4)3 electrode with a moderate doping amount are greatly improved. For example, when cycled under 1 C and 20 C in the potential range of 3.0–4.3 V, this sample shows an initial capacity of 122.5 and 118.4 mAh g−1, respectively; after 200 cycles, nearly 100% of the initial capacity is retained. Moreover, the modification effects of B‐doped carbon coating approach are further validated on Li4Ti5O12 anode material. An evolutionary modification approach, B‐doped carbon coating, is initially used to improve the electrochemical performance of Li3V2(PO4)3 cathode material and exhibits obvious and significant modification effects. Furthermore, the immediate causes and powerful evidences for this modification effect are given, analyzed, and verified in detail.
      PubDate: 2014-07-03T14:45:30.464494-05:
      DOI: 10.1002/adfm.201401006
  • Electronic Instabilities Leading to Electroformation of Binary Metal
           Oxide‐based Resistive Switches
    • Authors: Abhishek A. Sharma; Mohammad Noman, Mohamed Abdelmoula, Marek Skowronski, James A. Bain
      Pages: 5522 - 5529
      Abstract: Oxide‐based resistive switching devices are a leading contender for the next generation memories. Before use, each device has to go through a conditioning process called electroformation which has been suggested to be initiated by the accumulation of oxygen vacancies. Here, experimental evidence is presented which shows that both Ta2O5‐x‐ and TiO2‐x‐based crossbar devices, exhibit characteristic electronic instability leading to a reversible constriction of the current flow to a narrow filament prior to permanent change. Thus, it is asserted, electroformation is initiated through purely electronic and reversible events, to be followed later by structural changes in the material, like oxygen vacancy redistribution. Furthermore, the electronic instability responsible for electroformation also gives rise to negative differential resistance (NDR) and that this characteristics appears to involve two distinct mechanisms: a thermal one in which Joule heating causes resistance to decrease as current increases and a second electronic mechanism that appears not to require Joule heating for NDR. Using a combination of thermometry and thermal modeling, a self‐consistent temperature and filament radius as a function of power are found for the 5 μm cross‐bar devices. In the thermal NDR regime, the filament appears to be ∼500 nm in diameter and has a peak temperature of ∼300 °C, while in the adiabatic regime, the estimated filament diameter is much smaller (
      PubDate: 2014-07-09T10:51:49.569014-05:
      DOI: 10.1002/adfm.201400461
  • Charge Transport: Understanding Lattice Strain‐Controlled Charge
           Transport in Organic Semiconductors: A Computational Study (Adv. Funct.
           Mater. 35/2014)
    • Authors: Xiaoyan Zheng; Hua Geng, Yuanping Yi, Qikai Li, Yuqian Jiang, Dong Wang, Zhigang Shuai
      Pages: 5530 - 5530
      Abstract: The softness and anisotropy of organic semiconductors offer the opportunity to tune charge transport using lattice strain. On page 5531, D. Wang, Z. G. Shuai, and co‐workers elucidate through a multi‐scale theoretical approach, the relationship between lattice strain, molecular packing, and charge carrier mobility of TIPS‐pentacene, which enables an efficient and targeted control of charge transport.
      PubDate: 2014-09-11T12:57:41.728134-05:
      DOI: 10.1002/adfm.201470234
  • Understanding Lattice Strain‐Controlled Charge Transport in Organic
           Semiconductors: A Computational Study
    • Authors: Xiaoyan Zheng; Hua Geng, Yuanping Yi, Qikai Li, Yuqian Jiang, Dong Wang, Zhigang Shuai
      Pages: 5531 - 5540
      Abstract: The softness and anisotropy of organic semiconductors offer unique properties. Recently, solution‐sheared thin‐films of 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐P) with nonequilibrium single‐crystal domains have shown much higher charge mobilities than unstrained ones (Nature2011, 480, 504). However, to achieve efficient and targeted modulation of charge transport in organic semiconductors, a detailed microscopic understanding of the structure–property relationship is needed. In this work, motivated by the experimental studies, the relationship between lattice strain, molecular packing, and charge carrier mobility of TIPS‐P crystals is elucidated. By employing a multiscale theoretical approach combining nonequilibrium molecular dynamics, first‐principles calculations, and kinetic Monte Carlo simulations using charge‐transfer rates based on the tunneling enabled hopping model, charge‐transport properties of TIPS‐P under various lattice strains are investigated. Shear‐strained TIPS‐P indeed exhibits one‐dimensional charge transport, which agrees with the experiments. Furthermore, either shear or tensile strain lead to mobility enhancement, but with strong charge‐transport anisotropy. In addition, a combination of shear and tensile strains could not only enhance mobility, but also decrease anisotropy. By combining the shear and tensile strains, almost isotropic charge transport could be realized in TIPS‐P crystal with the hole mobility improved by at least one order of magnitude. This approach enables a deep understanding of the effect of lattice strain on charge carrier transport properties in organic semiconductors. Motivated by recent solution‐shearing experiments, a multiscale theoretical approach is employed to investigate charge‐transport properties of 6,13‐bis(triisopropylsilylethynyl) pentacene under various lattice strains, enabling a deep understanding of the lattice strain–molecular packing–charge carrier mobility relationship. The elucidated structure–property relationship is a prerequisite to efficient and targeted control of charge transport in organic semiconductors.
      PubDate: 2014-06-20T02:01:51.795344-05:
      DOI: 10.1002/adfm.201400261
  • Elastomeric Tiles for the Fabrication of Inflatable Structures
    • Authors: Stephen A. Morin; Sen Wai Kwok, Joshua Lessing, Jason Ting, Robert F. Shepherd, Adam A. Stokes, George M. Whitesides
      Pages: 5541 - 5549
      Abstract: This paper describes the fabrication of 3D soft, inflatable structures from thin, 2D tiles fabricated from elastomeric polymers. The tiles are connected using soft joints that increase the surface area available for gluing them together, and mechanically reinforce the structures to withstand the tensile forces associated with pneumatic actuation. The ability of the elastomeric polymer to withstand large deformations without failure makes it possible to explore and implement new joint designs, for example “double‐taper dovetail joints,” that cannot be used with hard materials. This approach simplifies the fabrication of soft structures comprising materials with different physical properties (e.g., stiffness, electrical conductivity, optical transparency), and provides the methods required to “program” the response of these structures to mechanical (e.g., pneumatic pressurization) and other physical (e.g., electrical) stimuli. The flexibility and modularity of this approach is demonstrated in a set of soft structures that expanded or buckled into distinct, predictable shapes when inflated or deflated. These structures combine easily to form extended systems with motions dependent on the configurations of the selected components, and, when fabricated with electrically conductive tiles, electronic circuits with pneumatically active elements. This approach to the fabrication of hollow, 3D structures provides routes to new soft actuators. 3D structures fabricated from elastomeric tiles change shape when inflated or deflated. The pneumatic expansion or contraction of these structures is “programmed” by selecting tiles with different mechanical properties. Connecting these structures together provides a method to explore soft machines with 3D architectures. Structures including electrically conductive tiles increase the designs and functions possible in soft machines.
      PubDate: 2014-07-09T10:50:57.940205-05:
      DOI: 10.1002/adfm.201401339
  • Trilevel‐Structured Superhydrophobic Pillar Arrays with Tunable
           Optical Functions
    • Authors: Sanghyuk Wooh; Jai Hyun Koh, Soojin Lee, Hyunsik Yoon, Kookheon Char
      Pages: 5550 - 5556
      Abstract: Water‐repelling surfaces inspired by lotus leaves have been developed for their commercial needs in superhydrophobic and self‐cleaning coatings on glasses and windows. The extraordinary properties originate from their multiscale structures with waxy materials. To obtain high transparency as well as superhydrophobicity, microhair arrays are designed with large spacing to reduce optical scattering effects caused by microstructures, but with a trilevel hierarchical structure to compensate for the loss of superhydrophobicity. In this study, a soft molding technique on wet pastes consisting of nanoparticles (NPs) is proposed to create a multilevel hierarchical structure of sub‐100 nm nanoparticles, which demonstrates excellent water repellency. Additionally, full advantage is taken of the TiO2 NP mesoporous structure for UV protection and for its ability to attach to various kinds of functional (for example, photoresponsive) dyes. Furthermore, the stability of fluorinated surfaces against UV light is enhanced by the passivation of the TiO2 surface with a thin silica coating. A highly transparent multilevel structure consisting of sub‐100 nm nanoparticles with excellent water repellency is deve­loped using a soft molding technique. Suppressing Mie scattering, high transparency is achieved in the structure with a low density of micro‐features. Moreover, a thin silica film and photoresponsive dyes attached to TiO2 nanoparticles are further introduced to realize multifunctional surfaces with high stability against UV light.
      PubDate: 2014-06-18T06:42:20.352096-05:
      DOI: 10.1002/adfm.201400228
  • Remarkably Improved Electrode Performance of Bulk MnS by Forming a Solid
           Solution with FeS – Understanding the Li Storage Mechanism
    • Authors: Liang Zhao; Xiqian Yu, Juezhi Yu, Yongning Zhou, Steven. N. Ehrlich, Yong‐Sheng Hu, Dong Su, Hong Li, Xiao‐Qing Yang, Liquan Chen
      Pages: 5557 - 5566
      Abstract: Transition metal compounds based on conversion reactions are promising electrode materials for lithium‐ion batteries due to their higher lithium storage capacity compared with currently available commercial battery electrodes. Most of the studies on these materials in the literature focus on transition metal oxides and fluorides, and not much work on transition metal sulphides has been reported, partially due to their relatively poor electrochemical performance. Here, synthesis and characterization of a series of solid solution FexMn1‐xS (x = 0.2, 0.5, 0.8) monosulphide compounds is reported. Interestingly, hexagonal FeS and cubic MnS can form a solid solution of FexMn1‐xS (x < 0.57). It is demonstrated that the lithium storage voltage can be tuned by changing the Fe concentration in the FexMn1‐xS matrix; meanwhile, the discharge‐charge coulombic efficiency and cycle stability of FexMn1‐xS are greatly enhanced in comparison with that of pure MnS. A half cell using Fe0.5Mn0.5S as electrode material achieves a high first cycle coulombic efficiency of 78.0% and a high reversible capacity of ca. 477 mAh g−1 after 35 cycles, while for pure MnS the first cycle coulombic efficiency is only 45.9% and the capacity rapidly fades to ≈200 mAh g−1 after 15 cycles. Although the solid solution state of Fe0.5Mn0.5S cannot be retained during conversion reaction as indicated by X‐ray diffraction (XRD), X‐ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM), the initial discharge “polarization”, which has been considered as one of the major hurdles for conversion reaction, can be significantly reduced by this type of material design. In addition, the size and distribution of the nucleated nanophases might also be altered by the initial solid solution state of Fe0.5Mn0.5S, contributing to the improved electrochemical performance reported here. A series of FexMn1‐xS (x = 0.2, 0.5, 0.8) monosulphide compounds is synthesized using a simple solid state reaction method. The lithium storage voltage can be tuned by the content of Fe in FexMn1‐xS, while the electrochemical performance of electrodes based on FexMn1‐xS is greatly enhanced in comparison with that of MnS. The lithium storage mechanism of Fe0.5Mn0.5S is investigated in detail.
      PubDate: 2014-07-14T02:40:25.442957-05:
      DOI: 10.1002/adfm.201400934
  • Nano‐Domain Pinning in Ferroelastic‐Ferroelectrics by Extended
           Structural Defects
    • Authors: Yachin Ivry; Colm Durkan, Daping Chu, James F. Scott
      Pages: 5567 - 5574
      Abstract: Most ferroelectrics are also ferroelastics (hysteretic stress‐strain relationship and response to mechanical stresses). The interactions between ferroelastic twin walls and ferroelectric domain walls are complex and only partly understood, hindering the technological potential of these materials. Here we study via atomic force microscopy the pinning of 180‐degree ferroelectric domain walls in lead zirconate titanate (PZT). Our observations satisfy all three categories of ferroelectric‐ferroelastic domain interaction proposed by Bornarel, Lajzerowicz, and Legrand. The structure, energy and topology of ferroelectric domains pinning as a result of extended structural defect are studied. Enhanced piezoresponse force microscopy is used to study the statics and dynamics of pinned domains. The pinning is analyzed in terms of Bornarel's theory, and Srolovitz and Scott's model, while a quantitative method to evaluate the energy of a pinned or distorted domain using the Landauer framework is presented.
      PubDate: 2014-07-14T06:11:34.899444-05:
      DOI: 10.1002/adfm.201304268
  • Autonomous Self‐Healing of Epoxy Thermosets with
           Thiol‐Isocyanate Chemistry
    • Authors: Xander K. D. Hillewaere; Roberto F. A. Teixeira, Le‐Thu T. Nguyen, José A. Ramos, Hubert Rahier, Filip E. Du Prez
      Pages: 5575 - 5583
      Abstract: Thiol‐isocyanate chemistry, combined with a dual capsule strategy, is used for the development of extrinsic self‐healing epoxy materials. It is shown that the amine groups present in the matrix both serve as a catalyst for the addition reaction between a thiol and an isocyanate and as a way to covalently link the healed network structure to the surrounding resin. The tapered double cantilever beam (TDCB) geometry is used for evaluating the recovery of the fracture toughness at room temperature after different healing times. Using manual injection of the healing agents into the crack, a healing efficiency up to 130% is obtained for the EPIKOTE 828/DETA epoxy material. On the other hand, when two types of microcapsules, one containing a tetrathiol reagent and the other a low toxic isocyanate reagent, are incorporated into this epoxy thermoset (20 wt%), a recovery of more than 50% is reached. The influence of parameters such as the amount and core content of the microcapsules on the healing efficiency is investigated. Furthermore, the thiol‐isocyanate chemistry is also tested for an industrial cold‐curing epoxy resin (RIM 135/RIMH 137). Thiol‐isocyanate chemistry is applied for the development of extrinsic self‐healing epoxy materials. The self‐healing ability is obtained by embedding both thiol‐ and isocyanate‐containing microcapsules into an epoxy thermoset. Tertiary amines present in the epoxy matrix are shown to catalyze the formation of the healed network. The stringent demands of industry concerning toxicity, thermal stability, and costs are approached.
      PubDate: 2014-07-10T04:42:23.756785-05:
      DOI: 10.1002/adfm.201400580
  • Nature of Charge Carriers in a High Electron Mobility Naphthalenediimide
           Based Semiconducting Copolymer
    • Authors: Valerio D'Innocenzo; Alessandro Luzio, Annamaria Petrozza, Daniele Fazzi, Mario Caironi
      Pages: 5584 - 5593
      Abstract: The nature of charge carriers in recently developed high mobility semiconducting donor‐acceptor polymers is debated. Here, localization due to charge relaxation is investigated in a prototypal system, a good electron transporting naphthalenediimide based copolymer, by means of current‐voltage I‐V electrical characteristics and charge modulation spectroscopy (CMS) in top‐gate field‐effect transistors (FETs), combined with density functional theory (DFT) and time dependent DFT (TDDFT) calculations. In particular, pristine copolymer films are compared with films that underwent a melt‐annealing process, the latter leading to a drastic change of the microstructure. Despite the packing modification, which involves also the channel region, both the electron mobility and the energy of polaronic transitions are substantially unchanged upon melt‐annealing. The polaron absorption features can be rationalized and reproduced by TDDFT calculations for isolated charged oligomers. Therefore, it is concluded that in such a high electron mobility copolymer the charge transport process involves polaronic species which are intramolecular in nature and, from a more general point of view, that interchain delocalization of the polaron is not necessary to sustain charge mobilities in the 0.1 to 1 cm2 V– 1 s–1 range. These findings contribute to the rationalization of the charge transport process in the recently developed class of donor‐acceptor π‐conjugated copolymers featuring high charge mobilities and complex morphologies. The degree of localization of polaronic charge carriers in a high mobility naphthalenediimide based semiconducting copolymer is revealed. By combining charge modulation spectroscopy and current–voltage characterization of field‐effect transistors with density functional theory calculations, it is demonstrated that the charge transport process involves only intramolecular polaronic species. This finding evidences that intermolecular hopping favored by strong electronic coupling is sufficient to sustain a charge carrier mobility in the 0.1 to 1 cm2 V–1s–1 range in a semiconducting polymer film.
      PubDate: 2014-07-10T04:59:03.94758-05:0
      DOI: 10.1002/adfm.201400394
  • Enhancing Photovoltaic Performance Using an All‐Conjugated Random
           Copolymer to Tailor Bulk and Interfacial Morphology of the P3HT:ICBA
           Active Layer
    • Authors: Anton Li; Jojo Amonoo, Bingyuan Huang, Peter K. Goldberg, Anne J. McNeil, Peter F. Green
      Pages: 5594 - 5602
      Abstract: Bulk heterojunction (BHJ) solar cells are fabricated using active material blends of poly(3‐hexylthiophene) (P3HT) donor, indene‐C60 bisadduct (ICBA) acceptor, and an all‐conjugated random copolymer (RCP) additive. By optimizing RCP loading, power conversion efficiencies (PCEs) up to 20% higher than those of a binary P3HT:ICBA mixture are achieved. The improved device characteristics are rationalized in terms of the differences between the photoactive thin film morphologies. Energy‐filtered transmission electron micro­scopy reveals that incorporation of the RCP improves the degree of structural order of the BHJ fibrillar network and increases the extent of microphase separation between P3HT and ICBA. Additionally, a combination of atomic force microscopy and X‐ray photoelectron spectroscopy analysis indicates segregation of the RCP at the free interface, leading to a shift in the surface potentials measured by Kelvin probe force microscopy. These changes, both in the bulk morphology and in the interfacial composition/energetics, are correlated to improved carrier collection efficiency due to a reduction of non‐geminate recombination, which is measured by charge extraction of photo­generated carriers by linearly increasing voltage. Power conversion efficiencies are enhanced by up to 20% when an all‐conjugated copolymer is incorporated into the P3HT:ICBA bulk heterojunction solar cells. The copolymer additive influences the internal active layer morphology as well as the interfacial composition, both of which can be correlated to a reduction of non‐geminate carrier recombination.
      PubDate: 2014-07-14T02:49:26.499897-05:
      DOI: 10.1002/adfm.201401058
  • Interface Functionalities in Multilayer Stack Organic Light Emitting
           Transistors (OLETs)
    • Authors: Raffaella Capelli; Franco Dinelli, Massimo Gazzano, Riccardo D'Alpaos, Andrea Stefani, Gianluca Generali, Mauro Riva, Monica Montecchi, Angelo Giglia, Luca Pasquali
      Pages: 5603 - 5613
      Abstract: Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field‐effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X‐ray diffraction and near edge X‐ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non‐ordered domains. Moreover, chemical reactivity at the interfaces is measured by X‐ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal‐organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties. An amorphous conjugated thin film, even though ideally flat, is not always an inert substrate for the growth of highly ordered molecular domains. Indeed it can induce an increase in the amount of non‐ordered domains in the upper layer. This effect needs to be carefully taken into account when designing multilayered devices based on a transistor architecture for high‐performance applications.
      PubDate: 2014-07-14T13:19:47.621373-05:
      DOI: 10.1002/adfm.201400877
  • Nanomaterials: Functionalized TiO2 Based Nanomaterials for Biomedical
           Applications (Adv. Funct. Mater. 35/2014)
    • Authors: Shuilin Wu; Zhengyang Weng, Xiangmei Liu, K.W. K. Yeung, Paul. K. Chu
      Pages: 5616 - 5616
      Abstract: Functionalized biomaterials are playing important roles in healthcare research as well as disease diagnosis and therapy. Recent advances in the biomedical application of functionalized TiO2‐based nanomaterials in the areas of bone reconstruction, intravascular stents, drug delivery systems, and biosensors are reviewed by S. L. Wu, P. K. Chu, and team on page 5464.
      PubDate: 2014-09-11T12:57:50.517415-05:
      DOI: 10.1002/adfm.201470236
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