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  Subjects -> CHEMISTRY (Total: 795 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (554 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (24 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (43 journals)
    - PHYSICAL CHEMISTRY (64 journals)

CHEMISTRY (554 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 4)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 31)
ACS Catalysis     Full-text available via subscription   (Followers: 25)
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: 18)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 25)
ACS Nano     Full-text available via subscription   (Followers: 306)
ACS Photonics     Full-text available via subscription   (Followers: 6)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 9)
Acta Chemica Iasi     Open Access  
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 6)
Acta Chromatographica     Full-text available via subscription   (Followers: 10)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 4)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 4)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 8)
Advanced Functional Materials     Hybrid Journal   (Followers: 36)
Advances in Chemical Engineering and Science     Open Access   (Followers: 22)
Advances in Chemical Science     Open Access   (Followers: 9)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 14)
Advances in Drug Research     Full-text available via subscription   (Followers: 16)
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: 15)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Science     Hybrid Journal   (Followers: 39)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 10)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 4)
African Journal of Chemical Education     Open Access   (Followers: 1)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 4)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alchemy     Open Access   (Followers: 3)
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: 29)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 188)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 18)
American Journal of Plant Physiology     Open Access   (Followers: 10)
American Mineralogist     Full-text available via subscription   (Followers: 5)
Analyst     Full-text available via subscription   (Followers: 35)
Angewandte Chemie     Hybrid Journal   (Followers: 17)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 243)
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: 19)
Arabian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 4)
Autophagy     Full-text available via subscription   (Followers: 1)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 234)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 4)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 4)
Bioinspired Materials     Open Access  
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 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: 14)
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: 13)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Carbohydrate Research     Hybrid Journal   (Followers: 11)
Carbon     Hybrid Journal   (Followers: 54)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 5)
Catalysis Science and Technology     Free   (Followers: 4)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 5)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Functional Materials
   [38 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]
  • Shear‐Thinning Supramolecular Hydrogels with Secondary Autonomous
           Covalent Crosslinking to Modulate Viscoelastic Properties In Vivo
    • Authors: Christopher B. Rodell; John W. MacArthur, Shauna M. Dorsey, Ryan J. Wade, Leo L. Wang, Y. Joseph Woo, Jason A. Burdick
      Pages: n/a - n/a
      Abstract: Clinical percutaneous delivery of synthetically engineered hydrogels remains limited due to challenges posed by crosslinking kinetics—too fast leads to delivery failure, too slow limits material retention. To overcome this challenge, supramolecular assembly is exploited to localize hydrogels at the injection site and introduce subsequent covalent crosslinking to control final material properties. Supramolecular gels are designed through the separate pendant modifications of hyaluronic acid (HA) by the guest–host pair cyclodextrin and adamantane, enabling shear‐thinning injection and high target site retention (>98%). Secondary covalent crosslinking occurs via addition of thiols and Michael‐acceptors (i.e., methacrylates, acrylates, vinyl sulfones) on HA and increases hydrogel moduli (E = 25.0 ± 4.5 kPa) and stability (>3.5 fold in vivo at 28 d). Application of the dual‐crosslinking hydrogel to a myocardial infarct model shows improved outcomes relative to untreated and supramolecular hydrogel alone controls, demonstrating its potential in a range of applications where the precise delivery of hydrogels with tunable properties is desired. Injectable hyaluronic acid hydrogels with high target site retention, tunable properties, and potential for percutaneous delivery are developed through a tandem crosslinking approach. Supramolecular crosslinking provides initial hydrogel formation and shear‐thinning delivery, while secondary covalent crosslinking stabilizes the hydrogel in situ. Material properties and treatment of myocardial infarct are examined.
      PubDate: 2014-12-12T04:35:06.358554-05:
      DOI: 10.1002/adfm.201403550
       
  • Facile Synthesis of Hematite Quantum‐Dot/Functionalized
           Graphene‐Sheet Composites as Advanced Anode Materials for Asymmetric
           Supercapacitors
    • Authors: Hui Xia; Caiyun Hong, Bo Li, Bin Zhao, Zixia Lin, Mingbo Zheng, Serguei V. Savilov, Serguei M. Aldoshin
      Pages: n/a - n/a
      Abstract: For building high‐energy density asymmetric supercapacitors, developing anode materials with large specific capacitance remains a great challenge. Although Fe2O3 has been considered as a promising anode material for asymmetric supercapacitors, the specific capacitance of the Fe2O3‐based anodes is still low and cannot match that of cathodes in the full cells. In this work, a composite material with well dispersed Fe2O3 quantum dots (QDs, ≈2 nm) decorated on functionalized graphene‐sheets (FGS) is prepared by a facile and scalable method. The Fe2O3 QDs/FGS composites exhibit a large specific capacitance up to 347 F g−1 in 1 m Na2SO4 between –1 and 0 V versus Ag/AgCl. An asymmetric supercapacitor operating at 2 V is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 aqueous electrolyte. The Fe2O3/FGS//MnO2/FGS asymmetric supercapacitor shows a high energy density of 50.7 Wh kg−1 at a power density of 100 W kg−1 as well as excellent cycling stability and power capability. The facile synthesis method and superior supercapacitive performance of the Fe2O3 QDs/FGS composites make them promising as anode materials for high‐performance asymmetric supercapacitors. Hematite quantum‐dot/functionalized graphene‐sheet composites are prepared and the composite electrode can reach a maximum specific capacitance of 347 F g−1, which is much larger than the reported values for the Fe2O3‐based electrodes in neutral aqueous electrolyte. A high‐performance 2 V asymmetrical supercapacitor is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 electrolyte.
      PubDate: 2014-12-12T04:34:47.061797-05:
      DOI: 10.1002/adfm.201403554
       
  • Fabrication of All‐Water‐Based Self‐Repairing
           Superhydrophobic Coatings Based on UV‐Responsive Microcapsules
    • Authors: Kunlin Chen; Shuxue Zhou, Shu Yang, Limin Wu
      Pages: n/a - n/a
      Abstract: Superhydrophobic coatings that are also self‐healing have drawn much attention in recent years for improved durability in practical applications. Typically, the release of the self‐healing agents is triggered by temperature and moisture change. In this study, UV‐responsive microcapsules are successfully synthesized by Pickering emulsion polymerization using titania (TiO2) and silica (SiO2) nanoparticles as the Pickering agents to fabricate all‐water‐based self‐repairing, superhydrophobic coatings. These coatings are environmentally friendly and can be readily coated on various substrates. Compared to conventional superhydrophobic coatings, these coatings can regenerate superhydrophobicity and self‐cleaning ability under UV light, mimicking the outdoor environment, after they are mechanically damaged or contaminated with organics. They can maintain the superhydrophobicity after multiple cycles of accelerated weathering tests. An environmentally benign, all‐water‐based self‐repairing superhydrophobic coating based on UV‐responsive microcapsules is fabricated, which exhibits excellent self‐healing and self‐cleaning ability in an outdoor environment, and after mechanical damage and contamination by organics.
      PubDate: 2014-12-12T04:34:30.560354-05:
      DOI: 10.1002/adfm.201403496
       
  • Masthead: (Adv. Funct. Mater. 47/2014)
    • Pages: n/a - n/a
      PubDate: 2014-12-12T01:14:20.238939-05:
      DOI: 10.1002/adfm.201470306
       
  • A Timely Synthetic Tailoring of Biaxially Extended
           Thienylenevinylene‐Like Polymers for Systematic Investigation on
           Field‐Effect Transistors
    • Authors: Dohyuk Yoo; Benjamin Nketia‐Yawson, Seok‐Ju Kang, Hyungju Ahn, Tae Joo Shin, Yong‐Young Noh, Changduk Yang
      Pages: n/a - n/a
      Abstract: Considering there is growing interest in the superior charge transport in the (E)‐2‐(2‐(thiophen‐2‐yl)‐vinyl)thiophene (TVT)‐based polymer family, an essential step forward is to provide a deep and comprehensive understanding of the structure–property relationships with their polymer analogs. Herein, a carefully chosen set of DPP‐TVT‐n polymers are reported here, involving TVT and diketopyrrolopyrrole (DPP) units that are constructed in combination with varying thiophene content in the repeat units, where n is the number of thiophene spacer units. Their OFET characteristics demonstrate ambipolar behavior; in particular, with DPP‐TVT‐0 a nearly balanced hole and electron transport are observed. Interestingly, the majority of the charge‐transport properties changed from ambipolar to p‐type dominant, together with the enhanced hole mobilities, as the electron‐donating thiophene spacers are introduced. Although both the lamellar d‐spacings and π‐stacking distances of DPP‐TVT‐n decreased with as the number of thiophene spacers increased, DPP‐TVT‐1 clearly shows the highest hole mobility (up to 2.96 cm2 V−1 s−1) owing to the unique structural conformations derived from its smaller paracrystalline distortion parameter and narrower plane distribution relative to the others. These in‐depth studies should uncover the underlying structure–property relationships in a relevant class of TVT‐like semiconductors, shedding light on the future design of top‐performing semiconducting polymers. A tactically chosen set of DPP‐TVT‐n polymers involving biaxially extended thienylenevinylene (TVT) and diketopyrrolopyrrole (DPP) units, by tuning the thiophene‐to‐vinylene ratio in the backbone, is synthesized. This in‐depth study uncovers that the degrees of the paracrystalline nature and the (h00) plane distribution, rather than densely packed organization, play a critical role in facilitating charge transport.
      PubDate: 2014-12-08T11:21:53.449091-05:
      DOI: 10.1002/adfm.201403527
       
  • Effective Photothermal Killing of Pathogenic Bacteria by Using Spatially
           Tunable Colloidal Gels with Nano‐Localized Heating Sources
    • Authors: Chun‐Wen Hsiao; Hsin‐Lung Chen, Zi‐Xian Liao, Radhakrishnan Sureshbabu, Hsu‐Chan Hsiao, Shu‐Jyuan Lin, Yen Chang, Hsing‐Wen Sung
      Pages: n/a - n/a
      Abstract: Alternative approaches to treating subcutaneous abscesses—especially those associated with antibiotic‐resistant pathogenic bacterial strains—that eliminate the need for antibiotics are urgently needed. This work descibes a chitosan (CS) derivative with self‐doped polyaniline (PANI) side chains that can self‐assemble into micelles in an aqueous environment and be transformed into colloidal gels in a process that is driven by a local increase in pH. These self‐doped PANI micelles can be utilized as nano‐localized heat sources, remotely controllable using near‐infrared (NIR) light. To test the in vivo efficacy of the CS derivative as a photothermal agent, an aqueous solution thereof is directly injected at the site of infected abscesses in a mouse model. The injected polymer solution eventually becomes distributed over the acidic abscesses, forming colloidal gels when it meets the boundaries of healthy tissues. After treatment with an 808 nm laser, the colloidal gels convert NIR light into heat, causing the thermal lysis of bacteria and repairing the infected wound without leaving residual implanted materials. This approach has marked potential because it can provide colloidal gels with tunable spatial stability, limiting localized heating to the infected sites, and reducing thermal damage to the surrounding healthy tissues. The injected polymer solution exhibits a rapid nanostructure transformation over a narrow range of pH values and forms a colloidal gel at the site of the abscess, providing tunable spatial stabilization. The formed colloidal gel converts near‐infrared (NIR) light energy into heat and causes thermal lysis of the bacteria, reducing thermal damage to the surrounding tissues.
      PubDate: 2014-12-08T11:20:16.900365-05:
      DOI: 10.1002/adfm.201403478
       
  • Intratumoral Thermal Reading During Photo‐Thermal Therapy by
           Multifunctional Fluorescent Nanoparticles
    • Authors: Elisa Carrasco; Blanca del Rosal, Francisco Sanz‐Rodríguez, Ángeles Juarranz de la Fuente, Patricia Haro Gonzalez, Ueslen Rocha, Kagola Upendra Kumar, Carlos Jacinto, José García Solé, Daniel Jaque
      Pages: n/a - n/a
      Abstract: The tremendous development of nanotechnology is bringing us closer to the dream of clinical application of nanoparticles in photothermal therapies of tumors. This requires the use of specific nanoparticles that must be highly biocompatible, efficient light‐to‐heat converters and fluorescent markers. Temperature reading by the heating nanoparticles during therapy appears of paramount importance to keep at a minimum the collateral damage that could arise from undesirable excessive heating. In this work, this thermally controlled therapy is possible by using Nd3+ ion‐doped LaF3 nanocrystals. Because of the particular optical features of Nd3+ ions at high doping concentrations, these nanoparticles are capable of in vivo photothermal heating, fluorescent tumor localization and intratumoral thermal sensing. The successful photothermal therapy experiments here presented highlight the importance of controlling therapy parameters based on intratumoral temperature measurements instead of on the traditionally used skin temperature measurements. In fact, significant differences between intratumoral and skin temperatures do exist and could lead to the appearance of excessive collateral damage. These results open a new avenue for the real application of nano­particle‐based photothermal therapy at clinical level. The unique ability of Neodymium doped LaF3 nanoparticles for simultaneous heating and temperature sensing is used here for the development of efficient and damage‐free photo‐thermal treatment of cancer tumors with real time intratumoral thermal reading.
      PubDate: 2014-12-06T09:48:24.85848-05:0
      DOI: 10.1002/adfm.201403653
       
  • Enhanced Light‐Harvesting by Integrating Synergetic Microcavity and
           Plasmonic Effects for High‐Performance ITO‐Free Flexible
           Polymer Solar Cells
    • Authors: Kai Yao; Xu‐Kai Xin, Chu‐Chen Chueh, Kung‐Shih Chen, Yun‐Xiang Xu, Alex K.‐Y. Jen
      Pages: n/a - n/a
      Abstract: In this work, a high‐performance ITO‐free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO‐free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well‐manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light‐harvesting with microcavity resonance in the regions of 400–500 nm and 600–700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light‐harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs. Highly efficient ITO‐free, flexible polymer solar cells (PSCs) are successfully demon­strated by integrating the plasmonic effect into microcavity‐based devices. By carefully controlling the embedded Ag nanoprisms sizes, the power conversion efficiency (PCE) of the devices can be significantly enhanced to as high as 9.4% on both glass and flexible (PET) substrates.
      PubDate: 2014-12-06T09:48:20.847223-05:
      DOI: 10.1002/adfm.201403297
       
  • Relating the Physical Structure and Optoelectronic Function of Crystalline
           TIPS‐Pentacene
    • Authors: Sahar Sharifzadeh; Cathy Y. Wong, Hao Wu, Benjamin L. Cotts, Leeor Kronik, Naomi S. Ginsberg, Jeffrey B. Neaton
      Pages: n/a - n/a
      Abstract: Theory and experiment are combined to investigate the nature of low‐energy excitons within ordered domains of 6,13‐bis(triisopropylsilylethynyl)‐pentacene (TIPS‐PEN) polycrystalline thin films. First‐principles density functional theory and many‐body perturbation theory calculations, along with polarization‐dependent optical absorption spectro‐microscopy on ordered domains, show multiple low‐energy absorption peaks that are composed of excitonic states delocalized over several molecules. While the first absorption peak is composed of a single excitonic transition and retains the polarization‐dependent behavior of the molecule, higher energy peaks are composed of multiple transitions with optical properties that can not be described by those of the molecule. The predicted structure‐dependence of polarization‐dependent absorption reveals the exact inter‐grain orientation within the TIPS‐PEN film. Additionally, the degree of exciton delocalization can be significantly tuned by modest changes in the solid‐state structure and the spatial extent of the excitations along a given direction is correlated with the degree of electronic dispersion along the same direction. These findings pave the way for tailoring the singlet fission efficiency of organic crystals by solid‐state structure. A combination of micro‐spectroscopy and many‐body perturbation theory reveals the inter‐grain orientation within polycrystalline TIPS‐pentacene films and the relationship of the physical structure to opto‐electronic properties.
      PubDate: 2014-12-06T09:48:18.729586-05:
      DOI: 10.1002/adfm.201403005
       
  • Epoxy Toughening with Low Graphene Loading
    • Authors: Yong Tae Park; Yuqiang Qian, Clement Chan, Taewon Suh, Mehrdad Ghasemi Nejhad, Christopher W. Macosko, Andreas Stein
      Pages: n/a - n/a
      Abstract: The toughening effects of graphene and graphene‐derived materials on thermosetting epoxies are investigated. Graphene materials with various structures and surface functional groups are incorporated into an epoxy resin by in situ polymerization. Graphene oxide (GO) and GO modified with amine‐terminated poly(butadiene‐acrylonitrile) (ATBN) are chosen to improve the dispersion of graphene nanosheets in epoxy and increase their interfacial adhesion. An impressive toughening effect is observed with less than 0.1 wt% graphene. A maximum in toughness at loadings as small as 0.02 wt% or 0.04 wt% is observed for all four types of graphene studied. An epoxy nanocomposite with ATBN‐modified GO shows a 1.5‐fold improvement in fracture toughness and a corresponding 2.4‐fold improvement in fracture energy at 0.04 wt% of graphene loading. At such low loadings, these graphene‐type materials become economically feasible components of nanocomposites. A microcrack mechanism is proposed based on microscopy of the fracture surfaces. Due to the stress concentration by graphene nanosheets, microcracks may be formed to absorb the fracture energy. However, above a certain graphene concentration, the coalescence of microcracks appears to facilitate crack propagation, lowering the fracture toughness. Crack deflection and pinning likely contribute to the slow increase in fracture toughness at higher loadings. Epoxy toughening by graphene is demonstrated at graphene loadings as low as 0.02 wt%. Functionalization of graphene can further improve the toughening effect at such a small loading level. A mechanism based on the formation and coalescence of microcracks generated by graphene is proposed to explain the fracture behavior of epoxy/graphene nanocomposites.
      PubDate: 2014-12-06T09:48:16.108792-05:
      DOI: 10.1002/adfm.201402553
       
  • High Performance Three‐Dimensional Chemical Sensor Platform Using
           Reduced Graphene Oxide Formed on High Aspect‐Ratio
           Micro‐Pillars
    • Authors: Le Thai Duy; Duck‐Jin Kim, Tran Quang Trung, Vinh Quang Dang, Bo‐Yeong Kim, Hock Key Moon, Nae‐Eung Lee
      Pages: n/a - n/a
      Abstract: The sensing performance of chemical sensors can be achieved not only by modification or hybridization of sensing materials but also through new design in device geometry. The performance of a chemical sensing device can be enhenced from a simple three‐dimensional (3D) chemiresistor‐based gas sensor platform with an increased surface area by forming networked, self‐assembled reduced graphene oxide (R‐GO) nanosheets on 3D SU8 micro‐pillar arrays. The 3D R‐GO sensor is highly responsive to low concentration of ammonia (NH3) and nitrogen dioxide (NO2) diluted in dry air at room temperature. Compared to the two‐dimensional planar R‐GO sensor structure, as the result of the increase in sensing area and interaction cross‐section of R‐GO on the same device area, the 3D R‐GO gas sensors show improved sensing performance with faster response (about 2%/s exposure), higher sensitivity, and even a possibly lower limit of detection towards NH3 at room temperature. A possibility of sensing enhancement of chemiresistor gas sensors based on reduced graphene oxide (R‐GO) through extension of device channel geometry by using three‐dimensional (3D) SU‐8 micro‐pillar array is discussed. The combination of controllable 3D structure and easily modifiable R‐GO reveals a good premise to maximize the advantages of the multi‐scale hybridization of R‐GO for contemporary and future sensing devices.
      PubDate: 2014-12-05T06:44:42.710615-05:
      DOI: 10.1002/adfm.201401992
       
  • A Bio‐inspired Potassium and pH Responsive Double‐gated
           Nanochannel
    • Authors: Meiying Liu; Huacheng Zhang, Kan Li, Liping Heng, Shutao Wang, Ye Tian, Lei Jiang
      Pages: n/a - n/a
      Abstract: Bio‐inspired nanochannels have emerged as an interface to mimic the functionalities of biological nanochannels. One remaining challenge is to develop double‐gated nanochannels with dual response, which can regulate the ion transport direction by alternately opening and closing the two gates. In this work, a bio‐inspired potassium and pH responsive double‐gated nanosystem is presented, constructed through immobilizing C‐quadruplex and G‐quadruplex DNA molecules onto the top and bottom tip side of a cigar‐shaped nanochannel, respectively. It is demonstrated that the two gates of the nanochannel can be opened and closed alternately/simultaneously. This phenomenon results from the attached DNA conformational transition caused by adjusting the concentrations of potassium ion and proton. This design is believed to be the first example of dual‐responsive double‐gated nanosystem, and paves a new way to investigate more intelligent bio‐inspired nanofluidic system. A dual‐responsive double‐gated nanochannel: A bio‐inspired potassium and pH responsive double‐gated nanosystem is developed by immobilizing C‐quadruplex and G‐quadruplex DNA molecules onto the top and bottom tip side of a cigar‐shaped nanochannel, respectively. This system, as the first example, may open up a new way to build diverse functional double‐gated nanochannel with dual‐response to meet the real‐world application.
      PubDate: 2014-12-03T00:52:38.692531-05:
      DOI: 10.1002/adfm.201401655
       
  • Current Understanding of Van der Waals Effects in Realistic Materials
    • Authors: Alexandre Tkatchenko
      Pages: n/a - n/a
      Abstract: Van der Waals (vdW) interactions arise from correlated electronic fluctuations in matter and are therefore present in all materials. Our understanding of these relatively weak yet ubiquitous quantum mechanical interactions has improved significantly during the past decade. This understanding has been largely driven by the development of efficient methods that now enable the modeling of vdW interactions in many realistic materials of interest for fundamental scientific questions and technological applications. In this work, the physics behind the currently available vdW methods are reviewed, and their applications to a wide variety of materials are highlighted, ranging from molecular assemblies to solids with and without defects, nanostructures of varying size and dimensionality, as well as interfaces between inorganic and organic materials. The origin of collective vdW interactions in materials is discussed using the concept of topological dipole waves. Focus is placed on the important observation that the full many‐body treatment of vdW interactions becomes crucial in the investigation and characterization of materials with increasing complexity, especially when studying their response properties, including vibrational, mechanical, and optical phenomena. Despite significant recent advances, many challenges still remain in the development of accurate and efficient methods for treating vdW interactions that will be broadly applicable to the modeling of functional materials at all relevant length and timescales. Van der Waals interactions arise from correlated electronic fluctuations in matter and are therefore present in all materials. Our current understanding of these ubiquitous quantum‐mechanical forces is summarized, and their effects in a wide variety of realistic materials are highlighted, ranging from molecular assemblies to solids with and without defects, nanostructures of varying size and dimensionality, as well as interfaces between inorganic and organic materials.
      PubDate: 2014-12-02T10:26:36.135329-05:
      DOI: 10.1002/adfm.201403029
       
  • Mechanical Surface Modification of Lithium Metal: Towards Improved Li
           Metal Anode Performance by Directed Li Plating
    • Authors: Myung‐Hyun Ryou; Yong Min Lee, Yunju Lee, Martin Winter, Peter Bieker
      Pages: n/a - n/a
      Abstract: The effect of mechanical surface modification on the performance of lithium (Li) metal foil electrodes is systematically investigated. The applied micro‐needle surface treatment technique for Li metal has various advantages. 1) This economical and efficient technique is able to cover a wide range of surface area with a simple rolling process, which can be easily conducted. 2) This technique achieves improved rate capability and cycling stability, as well as a reduced interfacial resistance. The micro‐needle treatment improves the rate capability by 20% (0.750 mAh at a rate of 7C) and increases the cycling stability by 200% (85% of the initial discharge capacity after 150 cycles) compared to untreated bare Li metal (0.626 mAh at a rate of 7C, 85% of the initial discharge capacity after only 70 cycles). 3) This technique efficiently suppresses Li formation of high surface area Li during the Li deposition process, as preferred sites for controlled Li plating are generated. The simple, scalable, and cost‐efficient surface treatment technique for Li metal is developed. With a simple rolling process, the micro‐needles create inverse micro‐needles pattern over wide area of Li metal surface, which remarkably enhances the power capabilities and cycle retention abilities to those of the bare Li metal.
      PubDate: 2014-12-02T10:26:33.85128-05:0
      DOI: 10.1002/adfm.201402953
       
  • Finite‐Temperature Properties of Rare‐Earth‐Substituted
           BiFeO3 Multiferroic Solid Solutions
    • Authors: Bin Xu; Dawei Wang, Jorge Íñiguez, Laurent Bellaiche
      Pages: n/a - n/a
      Abstract: Rare‐earth substitution in the multiferroic BiFeO3 (BFO) material holds promise for resolving drawbacks inherent to pure BFO, and for enhancing piezoelectric and magneto‐electric properties via a control of structural and magnetic characteristics. Rare‐earth‐doped BFO solid solutions also exhibit unresolved features, such as the precise nature and atomic characteristics of some intermediate phases. Here, an effective Hamiltonian scheme is developed that allows the investigation of finite‐temperature properties of these systems from an atomistic point of view. In addition to reproducing experimental results of Nd‐doped BFO on structural and magnetic transitions with temperature and composition, this scheme also provides an answer (in form of nanotwins) to these intermediate phases. A striking magneto‐electric effect—namely a paramagnetic–to–antiferromagnetic transition that is induced by an applied electric field—is further predicted near critical compositions, with the resulting structural path being dependent on the orientation of the electric field relative to the antiferroelectric vector. Rare‐earth substituted BiFeO3 (BFO) holds great promise as a piezoelectric and magnetoelectric material. A first‐principles based scheme is developed to investigate the structural and magnetic transitions of Nd‐doped BFO at finite temperatures. Thanks to this new method, the nature of the composition‐induced transformations is unveiled, and the possibility to control the magnetic order by an applied electric field is demonstrated.
      PubDate: 2014-12-02T02:55:57.584523-05:
      DOI: 10.1002/adfm.201403811
       
  • Structured Reduced Graphene Oxide/Polymer Composites for
           Ultra‐Efficient Electromagnetic Interference Shielding
    • Authors: Ding‐Xiang Yan; Huan Pang, Bo Li, Robert Vajtai, Ling Xu, Peng‐Gang Ren, Jian‐Hua Wang, Zhong‐Ming Li
      Pages: n/a - n/a
      Abstract: A high‐performance electromagnetic interference shielding composite based on reduced graphene oxide (rGO) and polystyrene (PS) is realized via high‐pressure solid‐phase compression molding. Superior shielding effectiveness of 45.1 dB, the highest value among rGO based polymer composite, is achieved with only 3.47 vol% rGO loading owning to multi‐facet segregated architecture with rGO selectively located on the boundaries among PS multi‐facets. This special architecture not only provides many interfaces to absorb the electromagnetic waves, but also dramatically reduces the loading of rGO by confining the rGO at the interfaces. Moreover, the mechanical strength of the segregated composite is dramatically enhanced using high pressure at 350 MPa, overcoming the major disadvantage of the composite made by conventional‐pressure (5 MPa). The composite prepared by the higher pressure shows 94% and 40% increment in compressive strength and compressive modulus, respectively. These results demonstrate a promising method to fabricate an economical, robust, and highly efficient EMI shielding material. The rGO/PS composite with segregated architecture is realized via high‐pressure solid‐phase compression molding for efficient EMI shielding. The highest EMI SE of 45.1 dB among rGO based polymer composites is achieved with only 3.47 vol% rGO loading. The high‐pressure molded composite shows 94% and 40% enhancement in compressive strength and modulus compared to conventional‐pressure molded composite.
      PubDate: 2014-12-02T02:55:55.280079-05:
      DOI: 10.1002/adfm.201403809
       
  • Simultaneous Control of Light Polarization and Phase Distributions Using
           Plasmonic Metasurfaces
    • Authors: Jianxiong Li; Shuqi Chen, Haifang Yang, Junjie Li, Ping Yu, Hua Cheng, Changzhi Gu, Hou‐Tong Chen, Jianguo Tian
      Pages: n/a - n/a
      Abstract: Harnessing light for modern photonic applications often involves the control and manipulation of light polarization and phase. Traditional methods require a combination of multiple discrete optical components, each of which contributes to a specific functionality. Here, plasmonic metasurfaces are proposed that accomplish the simultaneous manipulation of polarization and phase of the transmitted light. Arbitrary spatial field distribution of the optical phase and polarization direction can be obtained. The multifunctional metasurfaces are validated by demonstrating a broadband near‐perfect anomalous refraction with controllable linear polarization through introducing a constant phase gradient along the interface. Furthermore, the power of the proposed metasurfaces is demonstrated by generating a radially polarized beam. The new degrees of freedom of metasurfaces facilitate arbitrary manipulation of light and will profoundly affect a wide range of photonic applications. A radially polarized beam is generated based on proposed plasmonic metasurfaces that allow simultaneous manipulation of the polarization and phase of the transmitted light. Arbitrary spatial field distribution of the optical phase and polarization direction are obtained by accordingly designed plasmonic metasurfaces. The multifunctional metasurfaces are also validated by demonstrating a broadband near‐perfect anomalous refraction with controllable linear polarization.
      PubDate: 2014-12-02T02:55:52.923607-05:
      DOI: 10.1002/adfm.201403669
       
  • Ultrathin Iron Oxide Nanowhiskers as Positive Contrast Agents for Magnetic
           Resonance Imaging
    • Authors: Thomas Macher; John Totenhagen, Jennifer Sherwood, Ying Qin, Demet Gurler, Mark S. Bolding, Yuping Bao
      Pages: n/a - n/a
      Abstract: In this paper, a highly innovative concept of using ultrathin iron oxide nanowhiskers as a positive (T1) contrast agent for magnetic resonance imaging (MRI) is demonstrated. Iron oxide nanowhiskers with dimensions of approximately 2 nm × 20 nm are synthesized by heating an iron oleate/oleylamine complex under 150 °C. These nanostructures have very high surface‐to‐volume ratios, leading to strong paramagnetic signal, a property suitable for T1 contrast in MRI. The positive contrast enhancement of these nanowhiskers is demonstrated in vitro and in vivo in a rat model. Successful development of this technology has substantial commercial value in biomedical imaging, potentially leading to the advancement of human healthcare technologies. A new type of positive (T1) contrast agent for magnetic resonance imaging (MRI) is reported based on ultrathin iron oxide nanowhiskers. The key innovation is to alter the magnetic properties of nanoparticles through shape control. The positive MRI contrast enhancement of these nanowhiskers is demonstrated using the T1‐weighted image scans.
      PubDate: 2014-12-01T14:21:36.070774-05:
      DOI: 10.1002/adfm.201403436
       
  • Controlling the Dominant Length Scale of Liquid–Liquid Phase
           Separation in Spin‐coated Organic Semiconductor Films
    • Authors: Jacobus J. van Franeker; Daniel Westhoff, Mathieu Turbiez, Martijn M. Wienk, Volker Schmidt, René A. J. Janssen
      Pages: n/a - n/a
      Abstract: Organic electronic devices are often made by solution processing a multi‐component ink. During solution processing, for example, via spin coating, the solvent evaporates and the solid components deposit on the substrate. The morphology of this layer can range from well‐mixed to extensively phase separated. To optimize device performance, it is essential to control the degree and dominant length scale of phase separation. Currently, the mechanism of phase separation induced by solvent evaporation is poorly understood. It has been shown that length scales are influenced by spin speed, drying time, final layer thickness and the ratio between the solid components, but a complete experimental dataset and consistent theoretical understanding are lacking. In this contribution, in situ measurements during spin coating and a simple numerical model are used to understand the drying process. In addition, an advanced image analysis of transmission electron micrographs of films processed under a wide range of processing conditions is carried out. A normalized drying rate is proposed as the key parameter that controls the dominant length scale of phase separation. Droplet formation occurs in many solution‐processed organic semiconductor blends due to liquid–liquid phase separation. The combination of in situ measurements, a simple numerical spin coating model, and advanced image analysis on transmission electron micrographs show that the dominant length scale scales with a normalized drying rate, which is defined as the solvent evaporation rate divided by the dry layer thickness.
      PubDate: 2014-12-01T14:21:33.811976-05:
      DOI: 10.1002/adfm.201403392
       
  • Magnetic Liquid Marbles: Toward “Lab in a Droplet”
    • Authors: Yan Zhao; Zhiguang Xu, Haitao Niu, Xungai Wang, Tong Lin
      Pages: n/a - n/a
      Abstract: Liquid marbles exhibit great potential for use as miniature labs for small‐scale laboratory operations, such as experiment and measurement. While important progress has been made recently in exploring their applications as microreactions, “on‐line” measurement of the components inside the liquid still remains a challenge. Herein, it is demonstrated that “on‐line” detection can be realized on magnetic liquid marbles by taking advantage of their unique magnetic opening feature. By partially opening the particle shell, electrochemical measurement is carried out with a miniaturized three‐electrode probe and the application of this technique for quantitative measurement of dopamine is demonstrated. Fully opened magnetic liquid marble makes it feasible to detect the optical absorbance of the liquid in a transmission mode. With this optical method, a glucose assay is demonstrated. Moreover, when magnetic particle shell contains low melting point material, e.g., wax, the liquid marble shows a unique encapsulation ability to form a rigid shell after heating, which facilitates the storage of the non‐volatile ingredients. These unique features, together with the versatile use as microreactors, enable magnetic liquid marbles to function as a miniature lab (or called “lab in a droplet”), which may find applications in clinical diagnostics, biotechnology, chemical synthesis, and analytical chemistry. “On‐line” quantitative detection of liquid ingridents and biological assays is demonstratred in magnetic liquid marbles using electrochemical and optical approaches. The particle shell of magnetic liquid marbles can be hardened to preserve the samples/reagents when a low melting‐point material is present in the powder shell. These novel features, with the actuation and microreactor characteristics, make magnetic liquid marbles a promising candidate for “lab in a droplet”.
      PubDate: 2014-12-01T14:21:29.756184-05:
      DOI: 10.1002/adfm.201403051
       
  • Enhanced Electrochromism with Rapid Growth Layer‐by‐Layer
           Assembly of Polyelectrolyte Complexes
    • Authors: Mengqi Cui; Wee Siang Ng, Xu Wang, Peter Darmawan, Pooi See Lee
      Pages: n/a - n/a
      Abstract: In this work, a facile method to deposit fast growing electrochromic multilayer films with enhanced electrochemical properties using layer‐by‐layer (LbL) self‐assembly of complex polyelectrolyte is demonstrated. Two linear polymers, poly(acrylic acid) (PAA) and polyethylenimine (PEI), are used to formulate stable complexes under specific pH to prepare polyaniline (PANI)/PAA‐PEI multilayer films via LbL deposition. By introducing polymeric complexes as building blocks, [PANI/PAA‐PEI]n films grow much faster compared with [PANI/PAA]n films, which are deposited under the same condition. Unlike the compact [PANI/PAA]n films, [PANI/PAA‐PEI]n films exhibit porous structure that is beneficial to the electrochemical process and leads to improved electrochromic properties. An enhanced optical modulation of 30% is achieved with [PANI/PAA‐PEI]30 films at 630 nm compared with the lower optical modulation of 11% measured from [PANI/PAA]30 films. The switching time of [PANI/PAA‐PEI]30 films is only half of that of [PANI/PAA]30 films, which indicates a faster redox process. Utilizing polyelectrolyte complexes as building blocks is a promising approach to prepare fast growing LbL films for high performance electrochemical device applications. A fast growing film is fabricated via layer‐by‐layer (LbL) deposition by using polyelectrolyte complexes PAA‐PEI and PANI as building blocks. The film exhibits porous structure and enhanced electrochromism compared to PAA/PANI films under the same condition. The use of polyelectrolyte complexes is demonstrated to be beneficial for high performance electrochemically active LbL films.
      PubDate: 2014-12-01T14:21:25.149166-05:
      DOI: 10.1002/adfm.201402100
       
  • Plasticization of PEDOT:PSS by Common Additives for Mechanically Robust
           Organic Solar Cells and Wearable Sensors
    • Authors: Suchol Savagatrup; Esther Chan, Sandro M. Renteria‐Garcia, Adam D. Printz, Aliaksandr V. Zaretski, Timothy F. O'Connor, Daniel Rodriquez, Eduardo Valle, Darren J. Lipomi
      Pages: n/a - n/a
      Abstract: Despite the ubiquity of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in applications demanding mechanical flexibility, the effect on the mechanical properties of common additives—i.e., dimethylsulfoxide (DMSO), Zonyl fluorosurfactant (Zonyl), and poly(ethyleneimine) (PEI)—has not been reported. This paper describes these effects and uses plasticized films in solar cells and mechanical sensors for the detection of human motion. The tensile moduli of films spin‐coated from solutions containing 0%, 5%, and 10% DMSO and 0.1%, 1%, and 10% Zonyl (nine samples total) are measured using the buckling technique, and the ductility is inferred from measurements of the strain at which cracks form on elastic substrates. Elasticity and ductility are maximized in films deposited from solutions containing 5% DMSO and 10% Zonyl, but the conductivity is greatest for samples containing 0.1% Zonyl. These experiments reveal enlargement of presumably PEDOT‐rich grains, visible by atomic force microscopy, when the amount of DMSO is increased from 0% to 5%. PEI—which is used to lower the work function of PEDOT:PSS—has a detrimental effect on the mechanical properties of the PEDOT:PSS/PEI bilayer films. Wearable electronic sensors employing PEDOT:PSS films containing 5% DMSO and 10% Zonyl are ­fabricated, which exhibit detectable responses at 20% strain and high mechanical robustness through elastic deformation. This paper describes the effects of common additives on the mechanical properties (stiffness and ductility) of the transparent conductive polymer, PEDOT:PSS. In particular, 10% Zonyl fluorosurfactant decreases the tensile modulus by a factor of 100. Plasticized films are used for wearable sensors of human motion and have the potential to increase the mechanical robustness of organic solar cells.
      PubDate: 2014-11-29T05:41:21.342525-05:
      DOI: 10.1002/adfm.201401758
       
  • Few‐Layered SnS2 on Few‐Layered Reduced Graphene Oxide as
           Na‐Ion Battery Anode with Ultralong Cycle Life and Superior Rate
           Capability
    • Authors: Yandong Zhang; Peiyi Zhu, Liliang Huang, Jian Xie, Shichao Zhang, Gaoshao Cao, Xinbing Zhao
      Pages: n/a - n/a
      Abstract: Na‐ion Batteries have been considered as promising alternatives to Li‐ion batteries due to the natural abundance of sodium resources. Searching for high‐performance anode materials currently becomes a hot topic and also a great challenge for developing Na‐ion batteries. In this work, a novel hybrid anode is synthesized consisting of ultrafine, few‐layered SnS2 anchored on few‐layered reduced graphene oxide (rGO) by a facile solvothermal route. The SnS2/rGO hybrid exhibits a high capacity, ultralong cycle life, and superior rate capability. The hybrid can deliver a high charge capacity of 649 mAh g−1 at 100 mA g−1. At 800 mA g−1 (1.8 C), it can yield an initial charge capacity of 469 mAh g−1, which can be maintained at 89% and 61%, respectively, after 400 and 1000 cycles. The hybrid can also sustain a current density up to 12.8 A g−1 (≈28 C) where the charge process can be completed in only 1.3 min while still delivering a charge capacity of 337 mAh g−1. The fast and stable Na‐storage ability of SnS2/rGO makes it a promising anode for Na‐ion batteries. A SnS2/rGO hybrid with a plate‐on‐sheet architecture exhibits a high capacity, superior cycling stability and excellent rate capability. The hybrid delivers an initial capacity of 469 mAh g−1 at 800 mA g−1 and keeps at 61% after 1000 cycles. At 12.8 A g−1 (28 C), it still yields a charge capacity of 337 mAh g−1.
      PubDate: 2014-11-26T07:30:49.179529-05:
      DOI: 10.1002/adfm.201402833
       
  • Polymer/Nanocrystal Hybrid Solar Cells: Influence of Molecular Precursor
           Design on Film Nanomorphology, Charge Generation and Device Performance
    • Authors: Andrew J. MacLachlan; Thomas Rath, Ute B. Cappel, Simon A. Dowland, Heinz Amenitsch, Astrid‐Caroline Knall, Christine Buchmaier, Gregor Trimmel, Jenny Nelson, Saif A. Haque
      Pages: n/a - n/a
      Abstract: In this work, molecular tuning of metal xanthate precursors is shown to have a marked effect on the heterojunction morphology of hybrid poly(3‐hexylthiophene‐2,5‐diyl) (P3HT)/CdS blends and, as a result, the photochemical processes and overall performance of in situ fabricated hybrid solar cells. A series of cadmium xanthate complexes is synthesized for use as in situ precursors to cadmium sulfide nanoparticles in hybrid P3HT/CdS solar cells. The formation of CdS domains is studied by simultaneous GIWAXS (grazing incidence wide‐angle X‐ray scattering) and GISAXS (grazing incidence small‐angle X‐ray scattering), revealing knowledge about crystal growth and the formation of different morphologies observed using TEM (transmission electron microscopy). These measurements show that there is a strong relationship between precursor structure and heterojunction nanomorphology. A combination of TAS (transient absorption spectroscopy) and photovoltaic device performance measurements is used to show the intricate balance required between charge photogeneration and percolated domains in order to effectively extract charges to maximize device power conversion efficiencies. This study presents a strong case for xanthate complexes as a useful route to designing optimal heterojunction morphologies for use in the emerging field of hybrid organic/inorganic solar cells, due to the fact that the nanomorphology can be tuned via careful design of these precursor materials. Molecular tuning of metal xanthate precursors is shown to be a valuable tool to optimize absorber layer morphologies in ligand‐free prepared polymer/nanoparticle hybrid solar cells. Additionally to investigating the formation of the different nanomorphologies, their influences on optoelectronic properties are studied by transient absorption spectroscopy and a remarkable effect on device performance is revealed.
      PubDate: 2014-11-25T10:47:36.011413-05:
      DOI: 10.1002/adfm.201403108
       
  • Rational Design of a Printable, Highly Conductive Silicone‐based
           Electrically Conductive Adhesive for Stretchable Radio‐Frequency
           Antennas
    • Authors: Zhuo Li; Taoran Le, Zhenkun Wu, Yagang Yao, Liyi Li, Manos Tentzeris, Kyoung‐Sik Moon, C. P. Wong
      Pages: n/a - n/a
      Abstract: Stretchable radio‐frequency electronics are gaining popularity as a result of the increased functionality they gain through their flexible nature, impossible within the confines of rigid and planar substrates. One approach to fabricating stretchable antennas is to embed stretchable or flowable conductive materials, such as conductive polymers, conductive polymer composites, and liquid metal alloys as stretchable conduction lines. However, these conductive materials face many challenges, such as low electrical conductivity under mechanical deformation and delamination from substrates. In the present study, a silicone‐based electrically conductive adhesive (silo‐ECA) is developed that have a conductivity of 1.51 × 104 S cm−1 and can maintain conductivity above 1.11 × 103 S cm−1, even at a large stain of 240%. By using the stretchable silo‐ECAs as a conductor pattern and pure silicone elastomers as a base substrate, stretchable antennas can be fabricated by stencil printing or soft‐lithography. The resulting antenna's resonant frequency is tunable over a wide range by mechanical modulation. This fabrication method is low‐cost, can support large‐scale production, has high reliability over a wide temperature range, and eliminates the concerns of leaking or delamination between conductor and substrate experienced in previously reported micro‐fluidic antennas. Silicone‐based electrically conductive adhesives (silo‐ECAs) with an electrical conductivity of 1.51 × 104 S cm−1 at static state and 1.11 × 103 S cm−1 at a large stain of 240% is developed. By using the stretchable silo‐ECAs as the conductor and pure silicone elastomers as the substrate, stretchable antennas can be fabricated by stencil printing or soft‐lithography.
      PubDate: 2014-11-25T03:45:36.946221-05:
      DOI: 10.1002/adfm.201403275
       
  • Highly Porous Materials as Tunable Electrocatalysts for the Hydrogen and
           Oxygen Evolution Reaction
    • Authors: Marc Ledendecker; Guylhaine Clavel, Markus Antonietti, Menny Shalom
      Pages: n/a - n/a
      Abstract: The facile preparation of highly porous, manganese doped, sponge‐like nickel materials by salt melt synthesis embedded into nitrogen doped carbon for electrocatalytic applications is shown. The incorporation of manganese into the porous structure enhances the nickel catalyst's activity for the hydrogen evolution reaction in alkaline solution. The best catalyst demonstrates low onset overpotential (0.15 V) for the hydrogen evolution reaction along with high current densities at higher potentials. In addition, the possibility to alter the electrocatalytic properties of the materials from the hydrogen to oxygen evolution reaction by simple surface oxidation is shown. The surface area increases up to 1200 m2g−1 after mild oxidation accompanied by the formation of nickel oxide on the surface. A detailed analysis shows a synergetic effect of the oxide formation and the material's surface area on the catalytic performance in the oxygen evolution reaction. In addition, the synthesis of cobalt doped sponge‐like nickel materials is also delineated, demonstrating the generality of the synthesis. The facile salt melt synthesis of such highly porous metal based materials opens new possibilities for the fabrication of diverse electrode nanostructures for electrochemical applications. A facile synthesis of highly porous manganese doped sponge‐like nickel materials embedded in a carbon and nitrogen matrix is presented. The new materials demonstrate high electrocatalytic activity towards the water splitting reaction both in the hydrogen and oxygen evolution reaction. The use of these materials for both reactions results in a 70% voltage efficiency in the overall water splitting reaction.
      PubDate: 2014-11-22T02:45:31.233817-05:
      DOI: 10.1002/adfm.201402078
       
  • Mesoporous Silica Coated Single‐Walled Carbon Nanotubes as a
           Multifunctional Light‐Responsive Platform for Cancer Combination
           Therapy
    • Authors: Jingjing Liu; Chao Wang, Xiaojing Wang, Xin Wang, Liang Cheng, Yonggang Li, Zhuang Liu
      Pages: n/a - n/a
      Abstract: The development of cancer combination therapies, many of which rely on nanoscale theranostic agents, has received increasing attention in recent years. In this work, polyethylene glycol (PEG) modified mesoporous silica (MS) coated single‐walled carbon nanotubes (SWNTs) are fabricated and utilized as a multifunctional platform for imaging guided combination therapy of cancer. A model chemotherapy drug, doxorubicin (DOX), could be loaded into the mesoporous structure of the obtained SWNT@MS‐PEG nano‐carriers with high efficiency. Upon stimulation under near‐infrared (NIR) light, photothermally triggered drug release from DOX loaded SWNT@MS‐PEG is observed inside cells, resulting in a synergistic cancer cell killing effect. As revealed by both photoacoustic (PA) and magnetic resonance (MR) imaging, we further uncover efficient tumor accumulation of SWNT@MS‐PEG/DOX after intravenous injection into mice. In vivo combination therapy using this agent is further demonstrated in a mouse tumor model, achieving a remarkable synergistic anti‐tumor effect superior to that obtained by mono‐therapy. Our work presents a new type of theranostic nano‐platform, which could load therapeutic molecules with high efficiency, be responsive to external NIR stimulation, and at the same time serve as a diagnostic imaging agent. Mesoporous silica coated single‐wall carbon nanotubes with polyethylene glycol functionalization and anti‐cancer drug loading are developed as a multi­functional theranostic platform. Upon systemic administration of such nano‐agent, combined photothermal and chemotherapy, which is under the guidance of multimodal magnetic resonance and photoacoustic imaging, is conducted on an animal tumor model, achieving a great synergistic therapeutic effect.
      PubDate: 2014-11-20T11:34:15.7244-05:00
      DOI: 10.1002/adfm.201403079
       
  • A Free‐Standing and Ultralong‐Life Lithium‐Selenium
           Battery Cathode Enabled by 3D Mesoporous Carbon/Graphene Hierarchical
           Architecture
    • Authors: Kai Han; Zhao Liu, Jingmei Shen, Yuyuan Lin, Fang Dai, Hongqi Ye
      Pages: n/a - n/a
      Abstract: High capacity cathode materials for long‐life rechargeable lithium batteries are urgently needed. Selenium cathode has recently attracted great research attention due to its comparable volumetric capacity to but much better electrical conductivity than widely studied sulfur cathode. However, selenium cathode faces similar issues as sulfur (i.e., shuttling of polyselenides, volumetric expansion) and high performance lithium‐selenium batteries (Li–Se) have not yet been demonstrated at selenium loading >60% in the electrode. In this work, a 3D mesoporous carbon nanoparticles and graphene hierarchical architecture to storage selenium as binder‐free cathode material (Se/MCN‐RGO) for high energy and long life Li–Se batteries is presented. Such architecture not only provides the electrode with excellent electrical and ionic conductivity, but also efficiently suppresses polyselenides shuttling and accommodates volume change during charge/discharge. At selenium content of 62% in the entire cathode, the free‐standing Se/MCN‐RGO exhibits high discharge capacity of 655 mAh g−1 at 0.1 C (97% of theoretical capacity) and long cycling stability with a very small capacity decay of 0.008% per cycle over 1300 cycles at 1 C. The present report demonstrates significant progress in the development of high capacity cathode materials for long‐life Li batteries and flexible energy storage device. Free‐standing selenium cathode for lithium‐selenium batteries are developed by embedding selenium‐impreganated mesoporous carbon nanoparticles in graphene sheets (Se/MCN‐RGO). The 3D hierarchical architecture provides excellent electrical and ionic conductivity, and also suppresses polyselenides shuttling and accommodates volume change. The Se/MCN‐RGO exhibits ultra‐long cycle life with capacity retention of 89% after 1300 cycles at 1 C.
      PubDate: 2014-11-20T11:27:15.995855-05:
      DOI: 10.1002/adfm.201402815
       
  • Gadolinium‐Doped Persistent Nanophosphors as Versatile Tool for
           Multimodal In Vivo Imaging
    • Authors: Thomas Maldiney; Bich‐Thuy Doan, Damien Alloyeau, Michel Bessodes, Daniel Scherman, Cyrille Richard
      Pages: n/a - n/a
      Abstract: Recent breakthroughs in the rational development of multifunctional nanocarriers have highlightened the advantage of combining the complementary forces of several imaging modalities into one single nanotool fully dedicated to the biomedical field and diagnosis applications. A novel multimodal optical‐magnetic resonance imaging nanoprobe is introduced. Designed on the basis of a spinel zinc gallate structure doped with trivalent chromium and gadolinium, this nanocrystal bears the ability to serve as both a highly sensitive persistent luminescence nanoprobe for optical imaging, and a negative contrast agent for highly resolved magnetic resonance imaging (MRI). Additional proof is given that surface coverage can be modified in order to obtain stealth nanoparticles highly suitable for real‐time in vivo application in mice, showing delayed reticulo‐endothelial uptake and longer circulation time after systemic injection. An optical‐magnetic resonance imaging nanoprobe is designed on the basis of a spinel zinc gallate structure doped with trivalent chromium and gadolinium. This nanocrystal bears the ability to serve as both a highly sensitive persistent luminescence nanoprobe for optical imaging, and a negative contrast agent for magnetic resonance imaging. Surface coverage can be modified in order to obtain stealth nanoparticles suitable for real‐time in vivo application.
      PubDate: 2014-11-20T08:10:50.644879-05:
      DOI: 10.1002/adfm.201401612
       
  • Dipole–Dipole and H‐Bonding Interactions Significantly Enhance
           the Multifaceted Mechanical Properties of Thermoresponsive Shape Memory
           Hydrogels
    • Authors: Yinyu Zhang; Yongmao Li, Wenguang Liu
      Pages: n/a - n/a
      Abstract: High strength hydrogels were previously constructed based on dipole–dipole and hydrogen bonding reinforcement. In spite of the high tensile and compressive strengths achieved, the fracture energy of the hydrogels strengthened with sole noncovalent bondings was rather low due to the lack in energy dissipating mechanism. In this study, combined dipole–dipole and hydrogen bonding interactions reinforced (DHIR) hydrogels are synthesized by one‐step copolymerization of three feature monomers, namely acrylonitrile (AN, dipole monomer), acrylamide (AAm, H‐bonding monomer), and 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS, anionic monomer) in the presence of PEGDA575, a hydrophilic crosslinker. The electrostatic repulsion from PAMPS allows the gel network to absorb water readily, and meanwhile the synergistic effect of dipole–dipole and H‐bonding interactions enable the DHIR hydrogel to withstand up to 8.3 MPa tensile stress, 4.8 MPa compressive stress and 140–716% elongation at break with the fracture energy reaching as high as 5500 J/m2. In addition, this DHIR hydrogel exhibits reversible mechanical properties after undergoing cyclic loading and unloading. Interestingly, the DHIR hydrogels with appropriate compositions demonstrate temperature‐tunable mechanical properties as well as accompanied shape memory effect. The dual noncovalent bonding strengthening mechanism reported here offers a universal strategy for significantly enhancing the comprehensive mechanical properties of hydrogels. Combining dipole–dipole and hydrogen bonding interactions in one single network enhances the tensile/compressive strengths and toughness of hydrogels significantly. The rapid destruction and reconstruction of dual physical interactions contribute to the reversible mechanical properties and thermoresponsive shape memory effect. This dipole–dipole and H‐bonding reinforcement strategy offers a universal approach to design high performance hydrogels for practical load‐bearing applications.
      PubDate: 2014-11-20T03:59:22.917117-05:
      DOI: 10.1002/adfm.201401989
       
  • Plasmonic Particles that Hit Hypoxic Cells
    • Authors: Fulvio Ratto; Ewa Witort, Francesca Tatini, Sonia Centi, Lorenza Lazzeri, Fabrizio Carta, Matteo Lulli, Daniela Vullo, Franco Fusi, Claudiu T. Supuran, Andrea Scozzafava, Sergio Capaccioli, Roberto Pini
      Pages: n/a - n/a
      Abstract: The use of gold nanorods as contrast agents for the optical hyperthermia of cancer is receiving ever more attention. However, their selective delivery to tumors still remains an outstanding problem. In most cases, the identification of suitable molecular targets is complicated by the lack of qualitative differences between healthy and cancer cells. The focus of prior work has mainly been on the cancer cells per se. Instead, here, the aim is moved to secondary fingerprints that arise in response to the cancer microenvironment. One common feature of tumors is a combination of poor oxygenation and high oxygen consumption, which generates hypoxia. Hypoxic cells need to switch to an anaerobic metabolism, which is accompanied by a multitude of molecular processes, including the expression of transmembrane isoforms of carbonic anhydrases. Here, gold nanorods are conjugated with selective inhibitors of these enzymes, in order to recognize and hit hypoxic cells. The cellular uptake, cytostatic activity and capacity to impart an optical sensitization of these particles is shown to display a strong dependence on environmental oxygenation. Hybrid particles are engineered to target hypoxic cells, inhibit their proliferation, and mediate their optical sensitization. These particles comprise gold nanorods and inhibitors of carbonic anhydrases, which become accessible under hypoxia. Hypoxic cells are damaged both by compromising their metabolism and overheating with a laser. Since hypoxia occurs in most aggressive tumors, this construct represents a versatile anticancer agent.
      PubDate: 2014-11-20T03:59:20.180297-05:
      DOI: 10.1002/adfm.201402118
       
  • Soft Processing of Graphene Nanosheets by Glycine‐Bisulfate
           Ionic‐Complex‐Assisted Electrochemical Exfoliation of Graphite
           for Reduction Catalysis
    • Authors: Kodepelly Sanjeeva Rao; Jaganathan Sentilnathan, Hsun‐Wei Cho, Jih‐Jen Wu, Masahiro Yoshimura
      Pages: n/a - n/a
      Abstract: This study demonstrates a mild, environmentally friendly, and cost‐effective soft processing approach for the continuous synthesis of high‐quality, few‐layer graphene nanosheets. This has been achieved via electrochemical exfoliation of graphite, using an environmentally friendly glycine‐bisulfate ionic complex and was performed under ambient reaction conditions. Graphene nanosheets with 2–5 layers were obtained under optimized exfoliation conditions using a 15 wt% glycine‐bisulfate (aqueous) solution, with working biases of +1 V and +3 V applied for 5 min. The role of the glycine‐bisulfate ionic complex in the electrochemical exfoliation process was confirmed through comparison with a control experiment using only sulfuric acid as the electrolyte. A plausible electrochemical exfoliation mechanism that involves the formation of surface molecule nuclei via the polymerization of intercalated monomeric HSO4− and SO42− ions is proposed. The ionic complex plays a key role in the anodic graphite exfoliation via electrochemical‐potential‐induced intercalation, leading to an efficient expansion of graphite sheets via the insertion of oxygen functional groups. A mild, environmentally friendly, and cost‐effective soft processing approach for the continuous synthesis of high‐quality, few‐layer graphene nanosheets (GNSs) via the electrochemical exfoliation of graphite using an atomically economical (100%), low‐cost glycine‐bisulfate ionic complex is presented. The high‐quality and suitability of these GNSs to catalytic applications is demonstrated through the efficient reduction of benzoate, utilizing a GNS‐AuNCs hybrid.
      PubDate: 2014-11-20T03:59:11.707273-05:
      DOI: 10.1002/adfm.201402621
       
  • ε‐Branched Flexible Side Chain Substituted
           Diketopyrrolopyrrole‐Containing Polymers Designed for High Hole and
           Electron Mobilities
    • Authors: A‐Reum Han; Gitish K. Dutta, Junghoon Lee, Hae Rang Lee, Sang Myeon Lee, Hyungju Ahn, Tae Joo Shin, Joon Hak Oh, Changduk Yang
      Pages: n/a - n/a
      Abstract: Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π−π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm2 V−1 s−1), ultra‐high hole mobilities (up to 12.25 cm2 V−1 s−1) with an on/off ratio (Ion/Ioff) of at least 106 are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon. The novel ε‐branched side chains are incorporated into diketopyrrolopyrrole (DPP)‐based backbone to facilitate the charge transport by modulating π‐stacking and lamellar distance. A systematic investigation of the highly π‐extended systems with electron‐rich groups are also performed to achieve synergetic effects of the extended branching point of alkyl chains. These polymers effectively build up 3‐D charge transport pathways and exhibit ultra‐high mobilities.
      PubDate: 2014-11-20T03:13:10.663742-05:
      DOI: 10.1002/adfm.201403020
       
  • Enzyme‐Responsive Release of Doxorubicin from Monodisperse
           Dipeptide‐Based Nanocarriers for Highly Efficient Cancer Treatment
           In Vitro
    • Authors: He Zhang; Jinbo Fei, Xuehai Yan, Anhe Wang, Junbai Li
      Pages: n/a - n/a
      Abstract: Small aldehyde molecule are demonstrated to induce cationic diphenylalanine to assemble into monodisperse enzyme‐responsive nanocarriers with high biocompatibility and excellent biodegradability. The formation of Schiff base covalent bond and accompanying π–π interaction of aromatic rings are found to be the mainly driving forces for the assembly of the nanocarriers. Interestingly, the nanocarriers show autofluorescence due to the n‐π* transitions of C = N bonds, which lends them visually traceable property in living cells. Importantly, the nanocarriers can be taken in by cells and biodegraded in the cells. In addition, doxorubicin is easily loaded into the nanocarriers with high encapsulation amount, and its release can be triggered by tyrisin under physiological conditions. Noticeably, even at a very low drug concentration, the doxorubicin‐loaded nanocarriers still exhibit a much higher killing capacity of HeLa cells in vitro, compared to the equivalent‐dose free doxorubicin, indicating they have a great potential biomedical application. Cationic diphenylalanine (CDP) can assemble into biocompatible and biodegradable nanocarriers through cross‐linkage of glutaraldehyde (GA). The nanocarriers can be biodegraded under the action of tyrisin. Importantly, after loaded with doxorubicin (DOX) the nanocarriers also show a desired enzyme‐responsive property and the release of DOX can be easily achieved in PBS (pH 7.2) with tyrisin.
      PubDate: 2014-11-20T03:11:04.840331-05:
      DOI: 10.1002/adfm.201403119
       
  • FeO0.7F1.3/C Nanocomposite as a High‐Capacity Cathode Material for
           Sodium‐Ion Batteries
    • Authors: Yong‐Ning Zhou; Mahsa Sina, Nathalie Pereira, Xiqian Yu, Glenn G. Amatucci, Xiao‐Qing Yang, Frederic Cosandey, Kyung‐Wan Nam
      Pages: n/a - n/a
      Abstract: Searching high capacity cathode materials is one of the most important fields of the research and development of sodium‐ion batteries (SIBs). Here, we report a FeO0.7F1.3/C nanocomposite synthesized via a solution process as a new cathode material for SIBs. This material exhibits a high initial discharge capacity of 496 mAh g−1 in a sodium cell at 50 °C. From the 3rd to 50th cycle, the capacity fading is only 0.14% per cycle (from 388 mAh g−1 at 3rd the cycle to 360 mAh g−1 at the 50th cycle), demonstrating superior cyclability. A high energy density of 650 Wh kg−1 is obtained at the material level. The reaction mechanism studies of FeO0.7F1.3/C with sodium show a hybridized mechanism of both intercalation and conversion reaction. A high‐capacity cathode for a sodium battery is presented. FeO0.7F1.3/C nanocomposite exhibits a high initial discharge capacity of 496 mAh g−1 in a sodium cell at 50 °C. A reversible capacity of 360 mAh g−1 is retained at the 50th cycle, demonstrating superior cycleability. Both intercalation and conversion reactions are revealed during the discharge‐charge process of the FeO0.7F1.3/C – Na cell.
      PubDate: 2014-11-20T03:10:59.92263-05:0
      DOI: 10.1002/adfm.201403241
       
  • Sodium Storage Behavior in Natural Graphite using Ether‐based
           Electrolyte Systems
    • Authors: Haegyeom Kim; Jihyun Hong, Young‐Uk Park, Jinsoo Kim, Insang Hwang, Kisuk Kang
      Pages: n/a - n/a
      Abstract: This work reports that natural graphite is capable of Na insertion and extraction with a remarkable reversibility using ether‐based electrolytes. Natural graphite (the most well‐known anode material for Li–ion batteries) has been barely studied as a suitable anode for Na rechargeable batteries due to the lack of Na intercalation capability. Herein, graphite is not only capable of Na intercalation but also exhibits outstanding performance as an anode for Na ion batteries. The graphite anode delivers a reversible capacity of ≈150 mAh g−1 with a cycle stability for 2500 cycles, and more than 75 mAh g−1 at 10 A g−1 despite its micrometer‐size (≈100 μm). An Na storage mechanism in graphite, where Na+‐solvent co‐intercalation occurs combined with partial pseudocapacitive behaviors, is revealed in detail. It is demonstrated that the electrolyte solvent species significantly affect the electrochemical properties, not only rate capability but also redox potential. The feasibility of graphite in a Na full cell is also confirmed in conjunction with the Na1.5VPO4.8F0.7 cathode, delivering an energy of ≈120 Wh kg−1 while maintaining ≈70% of the initial capacity after 250 cycles. This exceptional behavior of natural graphite promises new avenues for the development of cost‐effective and reliable Na ion batteries. This study reports unusual Na storage behavior in natural graphite through Na+‐solvent co‐intercalation combined with pseudocapacitive behaviors using ether‐based electrolytes which was confirmed by electrochemical and ex situ analyses. This work can be used as a foundation for further studies on graphite as a promising anode for NIBs in conjunction with its straightforward advantages, such as low costs, earth abundance, environmental friendliness, and non‐toxicity.
      PubDate: 2014-11-20T03:10:35.691029-05:
      DOI: 10.1002/adfm.201402984
       
  • Building Three‐Dimensional Graphene Frameworks for Energy Storage
           and Catalysis
    • Authors: Minghao Yu; Yongchao Huang, Cheng Li, Yinxiang Zeng, Wang Wang, Yao Li, Pingping Fang, Xihong Lu, Yexiang Tong
      Pages: n/a - n/a
      Abstract: Due to their unique architectures and outstanding electrical properties, three dimensional graphene‐based frameworks (3DGFs) have attracted extensive attention in wide fields. However, recently reported techniques always require complex processes and high cost, which severely limit their large‐scale application. In this study, the massive preparation of macroscopically porous 3DGFs from the inherently inexpensive graphite paper is for the first time realized by simply combining the modified Hummer's method with freezing technique. The as‐prepared 3DGFs that consist of well exfoliated, high‐quality reduced graphene oxide (RGO) exhibit a mesoporous structure and superior conductivity. Such unique features enable the 3DGFs to be directly used as a supercapacitor electrode and as ideal 3D scaffolds to create PANI@3DGFs, Pd@3DGFs, and Pt@3DGFs composites, which hold great potential applications in supercapacitors and catalysts. The massive fabrication of high‐quality three dimensional graphene‐based frameworks (3DGFs) is reported here. The as‐fabricated 3DGFs exhibit a superior conductivity and large surface area. Meanwhile the application of 3DGFs as versatile 3D scaffolds to create PANI@3DGFs, Pd@3DGFs, and Pt@3DGFs composites is demonstrated, which should find applications in 3D electrode materials for supercapacitors and catalyst.
      PubDate: 2014-11-20T03:10:02.266653-05:
      DOI: 10.1002/adfm.201402964
       
  • Dynamic Fluoroalkyl Polyethylene Glycol Co‐Polymers: A New Strategy
           for Reducing Protein Adhesion in Lab‐on‐a‐Chip Devices
    • Authors: Mahesh K. Sarvothaman; Kris S. Kim, Brendon Seale, Peter M. Brodersen, Gilbert C. Walker, Aaron R. Wheeler
      Pages: n/a - n/a
      Abstract: Non‐specific adsorption of biomolecules (or “biofouling”) is a major problem in microfluidics and many other applications. The problem is particularly pernicious in digital microfluidics (DMF, a technique in which droplets are manipulated electrodynamically on an array of electrodes coated with a hydrophobic insulator), as local increases in surface energy that arise from fouling can cause droplet movement to fail. We report a new solution to this problem: a device coating bearing a combination of fluorinated poly(ethylene glycol) functionalities (FPEG) and perfluorinated methacrylate (FA) moieties. A range of different FPEG‐FA copolymers were synthesized containing varying amounts of FPEG relative to the fluorinated backbone. Coatings with low%FPEG were found to result in significant reductions in protein adsorption and improvements in device lifetime (up to 5.5‐fold) relative to the state of the art. An analysis of surface topology and chemistry suggests that FPEG‐FA surfaces undergo a dynamic reconstruction upon activation by applying DMF driving potentials, with FPEG groups forming vertical protrusions out of the plane of the device surface. An analysis of changes in surface wettability and adhesion as a function of activation supports this hypothesis. This innovation represents an advance for digital microfluidics, and may also find use in other applications that are currently limited by biofouling. An antifouling coating is described that improves digital microfluidic device lifetime up to 5.5‐fold relative to the state of the art. The material is dynamic: under standard conditions, the surface is flat and fluorinated; upon applying an electrical potential, the surface becomes activated, forming nanometer‐sized fluoropegylated structures.
      PubDate: 2014-11-20T03:09:58.008631-05:
      DOI: 10.1002/adfm.201402218
       
  • Recapillarity: Electrochemically Controlled Capillary Withdrawal of a
           Liquid Metal Alloy from Microchannels
    • Authors: Mohammad R. Khan; Chris Trlica, Michael D. Dickey
      Pages: n/a - n/a
      Abstract: This paper describes the mechanistic details of an electrochemical method to control the withdrawal of a liquid metal alloy, eutectic gallium indium (EGaIn), from microfluidic channels. EGaIn is one of several alloys of gallium that are liquid at room temperature and form a thin (nm scale) surface oxide that stabilizes the shape of the metal in microchannels. Applying a reductive potential to the metal removes the oxide in the presence of electrolyte and induces capillary behavior; we call this behavior “recapillarity” because of the importance of electrochemical reduction to the process. Recapillarity can repeatably toggle on and off capillary behavior by applying voltage, which is useful for controlling the withdrawal of metal from microchannels. This paper explores the mechanism of withdrawal and identifies the applied current as the key factor dictating the withdrawal velocity. Experimental observations suggest that this current may be necessary to reduce the oxide on the leading interface of the metal as well as the oxide sandwiched between the wall of the microchannel and the bulk liquid metal. The ability to control the shape and position of a metal using an applied voltage may prove useful for shape reconfigurable electronics, optics, transient circuits, and microfluidic components. The mechanistic details of a method to control the withdrawal of a liquid metal alloy, eutectic gallium indium (EGaIn), from microfluidic channels, are described. Recapillarity is a technique to repeatably toggle on and off the capillary behavior of a liquid metal by electrochemically reducing its surface oxide. It can control the shape of liquid metal in microchannels for reconfigurable circuits.
      PubDate: 2014-11-19T08:01:01.978048-05:
      DOI: 10.1002/adfm.201403042
       
  • An Interface‐Induced Co‐Assembly Approach Towards Ordered
           Mesoporous Carbon/Graphene Aerogel for High‐Performance
           Supercapacitors
    • Authors: Ruili Liu; Li Wan, Shaoqing Liu, Lixia Pan, Dongqing Wu, Dongyuan Zhao
      Pages: n/a - n/a
      Abstract: Hierarchically porous composites with mesoporous carbon wrapping around the macroporous graphene aerogel can combine the advantages of both components and are expected to show excellent performance in electrochemical energy devices. However, the fabrication of such composites is challenging due to the lack of an effective strategy to control the porosity of the mesostructured carbon layers. Here an interface‐induced co‐assembly approach towards hierarchically mesoporous carbon/graphene aerogel composites, possessing interconnected macroporous graphene networks covered by highly ordered mesoporous carbon with a diameter of ≈9.6 nm, is reported. And the orientation of the mesopores (vertical or horizontal to the surface of the composites) can be tuned by the ratio of the components. As the electrodes in supercapacitors, the resulting composites demonstrate outstanding electrochemical performances. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications. When ordered mesoporous carbons meet graphene areogel, the resulting hierarchically porous composites conglomerating the advantages of both components are obtained and exhibit excellent performance in electrochemical energy devices. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications.
      PubDate: 2014-11-19T06:56:37.464703-05:
      DOI: 10.1002/adfm.201403280
       
  • Self‐Sacrifice Template Fabrication of Hierarchical Mesoporous
           Bi‐Component‐Active ZnO/ZnFe2O4 Sub‐Microcubes as
           Superior Anode Towards High‐Performance Lithium‐Ion Battery
    • Authors: Linrui Hou; Lin Lian, Longhai Zhang, Gang Pang, Changzhou Yuan, Xiaogang Zhang
      Pages: n/a - n/a
      Abstract: In the work, a facile yet efficient self‐sacrifice strategy is smartly developed to scalably fabricate hierarchical mesoporous bi‐component‐active ZnO/ZnFe2O4 (ZZFO) sub‐microcubes (SMCs) by calcination of single‐resource Prussian blue analogue of Zn3[Fe(CN)6]2 cubes. The hybrid ZZFO SCMs are homogeneously constructed from well‐dispersed nanocrstalline ZnO and ZnFe2O4 (ZFO) subunites at the nanoscale. After selectively etching of ZnO nanodomains from the hybrid, porously assembled ZFO SMCs with integrate architecture are obtained accordingly. When evaluated as anodes for LIBs, both hybrid ZZFO and ZFO samples exhibit appealing electrochemical performance. However, the as‐synthesized ZZFO SMCs demonstrate even better electrochemical Li‐storage performance, including even larger initial discharge capacity and reversible capacity, higher rate behavior and better cycling performance, particularly at high rates, compared with the single ZFO, which should be attributed to its unique microstructure characteristics and striking synergistic effect between the bi‐component‐active, well‐dispersed ZnO and ZFO nanophases. Of great significance, light is shed upon the insights into the correlation between the electrochemical Li‐storage property and the structure/component of the hybrid ZZFO SMCs, thus, it is strongly envisioned that the elegant design concept of the hybrid holds great promise for the efficient synthesis of advanced yet low‐cost anodes for next‐generation rechargeable Li‐ion batteries. Hierarchical mesoporous ZnO/ZnFe2O4 sub‐microcubes are rationally fabricated via an efficiently scalable self‐sacrifice strategy and exhibit excellent electrochemical Li‐storage performance, benefiting from their unique structural characteristics and striking synergistic effect between the bi‐component‐active, well‐dispersed ZnO and ZFO nanophases at the nanoscale.
      PubDate: 2014-11-19T06:56:31.17624-05:0
      DOI: 10.1002/adfm.201402827
       
  • ZnO Hard Templating for Synthesis of Hierarchical Porous Carbons with
           Tailored Porosity and High Performance in Lithium‐Sulfur Battery
    • Authors: Patrick Strubel; Sören Thieme, Tim Biemelt, Alexandra Helmer, Martin Oschatz, Jan Brückner, Holger Althues, Stefan Kaskel
      Pages: n/a - n/a
      Abstract: Hierarchical porous carbon (HPC, DUT‐106) with tailored pore structure is synthesized using a versatile approach based on ZnO nanoparticles avoiding limitations present in conventional silica hard templating approaches. The benefit of the process presented here is the removal of all pore building components by pyrolysis of the ZnO/carbon composite without any need for either toxic/reactive gases or purification of the as‐prepared hierarchical porous carbon. The carbothermal reduction process is accompanied by an advantageous growing of distinctive micropores within the thin carbon walls. The resulting materials show not only high internal porosity (total pore volume up to 3.9 cm3 g−1) but also a large number of electrochemical reaction sites due to their remarkably high specific surface area (up to 3060 m2 g−1), which renders them particularly suitable for the application as sulfur host material. Applied in the lithium‐sulfur battery, the HPC/sulfur composite exhibits a capacity of >1200 mAh g−1‐sulfur (>750 mAh g−1 electrode) at a high sulfur loading of ≥ 3 mg cm−2 as well as outstanding rate capability. In fact, this impressive performance is achieved even using a low amount of electrolyte (6.8 μl mg−1 sulfur) allowing for further weight reduction and maintenance of high energy density on cell level. Hierarchical porous carbon (HPC) prepared by a ZnO nanoparticle hard templating approach enables in situ template removal accompanied by a controllable growth of micropores within the carbon walls. Due to tailored porosity, the HPC/S composite delivers a high discharge capacity at high sulfur content and loading as well as moderate amount of electrolyte. This triggers high energy densities on cell level.
      PubDate: 2014-11-19T06:56:28.01869-05:0
      DOI: 10.1002/adfm.201402768
       
  • Eliminating the Trade‐Off between the Throughput and Pattern Quality
           of Sub‐15 nm Directed Self‐Assembly via Warm Solvent Annealing
           
    • Authors: Jong Min Kim; YongJoo Kim, Woon Ik Park, Yoon Hyung Hur, Jae Won Jeong, Dong Min Sim, Kwang Min Baek, Jung Hye Lee, Mi‐Jeong Kim, Yeon Sik Jung
      Pages: n/a - n/a
      Abstract: The directed self‐assembly (DSA) of block copolymers (BCPs) has been suggested as a promising nanofabrication solution. However, further improvements of both the pattern quality and manufacturability remain as critical challenges. Although the use of BCPs with a high Flory‐Huggins interaction parameter (χ) has been suggested as a potential solution, this practical self‐assembly route has yet to be developed due to their extremely slow self‐assembly kinetics. In this study, it is reported that warm solvent annealing (WSA) in a controlled environment can markedly improve both the self‐assembly kinetics and pattern quality. A means of avoiding the undesirable trade‐off between the quality and formation throughput of the self‐assembled patterns, which is a dilemma which arises when using the conventional solvent vapor treatment, is suggested. As a demonstration, the formation of well‐defined 13‐nm‐wide self‐assembled patterns (3σ line edge roughness of ≈2.50 nm) in treatment times of 0.5 min (for 360‐nm‐wide templates) is shown. Self‐consistent field theory (SCFT) simulation results are provided to elucidate the mechanism of the pattern quality improvement realized by WSA. The formation of high‐resolution, high‐throughput, and high‐quality patterns is accomplished using a warm solvent‐vapor annealing (WSA) treatment for the self‐assembly of block copolymers (BCPs) with an extremely high segregation strength. A means of avoiding the undesirable trade‐off between the quality and formation throughput of the self‐assembled patterns is suggested. The significant improvement of pattern quality realized by WSA is attributed to the reduced degree of interfacial deformation during final solvent evaporation.
      PubDate: 2014-11-19T06:56:23.259152-05:
      DOI: 10.1002/adfm.201401529
       
  • Submicrometer‐Sized ZIF‐71 Filled Organophilic Membranes for
           Improved Bioethanol Recovery: Mechanistic In‐Sights by Monte Carlo
           Simulation and FTIR Spectroscopy
    • Authors: Lik H. Wee; Yanbo Li, Kang Zhang, Patrizia Davit, Silvia Bordiga, Jianwen Jiang, Ivo F. J. Vankelecom, Johan A. Martens
      Pages: n/a - n/a
      Abstract: Template‐free self‐assembly synthesis of nano‐sized metal‐organic frameworks (MOFs) is of particular interest in MOF research since organized nanostructures possessing distinctive properties are useful for many advanced applications. In this work, the facile room temperature synthesis of robust submicrometer‐sized ZIF‐71 crystals with different particle sizes (140, 290, or 430 nm), having a high permanent microporosity (SBET = 827 cm2 g−1) and synthesis yield up to 80% based on Zn on a gram‐scale, is reported. These small ZIF‐71 particles are ideal filler for the fabrication of thinner and homogeneous polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) with excellent filler dispersion and filler‐polymer adhesion at high loading up to 40 wt%, as confirmed by scanning electron microscopy. Pervaporation tests using these submicrometer‐sized ZIF‐71 filled MMMs show significant improvement for bioethanol recovery. Interesting phenomena of i) reversible ethanol‐ethanol hydrogen interaction in the ethanol liquid‐phase and ii) irreversible hydrogen interaction of ethanol and –Cl functional group in the α‐cages and octagonal prismatic cages of ZIF‐71 in ethanol vapor‐phase are discovered for the first time by a Fourier transform infrared spectroscopy (FTIR) study. In full agreement with molecular simulation results, these explain fundamentally the ZIF‐71 filled MMMs pervaporation performance. Gram scale synthesis of submicrometer‐sized ZIF‐71 crystal is demonstrated via a simple mixed solvent approach for improving mixed matrix membrane pervaporation separation of bioethanol. The host–guest chemistry at its molecular level is unravelled by grand canonical Monte Carlo simulation and FTIR spectroscopy. The results reveal a strong hydrogen interaction between the cages of ZIF‐71 and ethanol, well explaining the pervaporation performance.
      PubDate: 2014-11-19T06:56:18.223768-05:
      DOI: 10.1002/adfm.201402972
       
  • Transparent and Stretchable Interactive Human Machine Interface Based on
           Patterned Graphene Heterostructures
    • Authors: Sumin Lim; Donghee Son, Jaemin Kim, Young Bum Lee, Jun‐Kyul Song, Suji Choi, Dong Jun Lee, Ji Hoon Kim, Minbaek Lee, Taeghwan Hyeon, Dae‐Hyeong Kim
      Pages: n/a - n/a
      Abstract: An interactive human‐machine interface (iHMI) enables humans to control hardware and collect feedback information. In particular, wearable iHMI systems have attracted tremendous attention owing to their potential for use in personal mobile electronics and the Internet of Things. Although significant progress has been made in the development of iHMI systems, those based on rigid electronics have constraints in terms of wearability, comfortability, signal‐to‐noise ratio (SNR), and aesthetics. Herein the fabrication of a transparent and stretchable iHMI system composed of wearable mechanical sensors and stimulators is reported. The ultrathin and lightweight design of the system allows superior wearability and high SNR. The use of conductive/piezoelectric graphene heterostructures, which consist of poly(l‐lactic acid), single‐walled carbon nanotubes, and silver nanowires, results in high transparency, excellent performance, and low power consumption as well as mechanical deformability. The control of a robot arm for various motions and the feedback stimulation upon successful executions of commands are demonstrated using the wearable iHMI system. A transparent and stretchable interactive human machine interface (iHMI) based on patterned graphene (GP) heterostructures is developed. The conductive/piezoelectric GP heterostructures enable the iHMI to have high transparency, excellent performance, low power consumption, and superb mechanical deformability. The control of a robot arm for various motions and feedback stimulation upon successful executions of commands are demonstrated using the wearable iHMI system.
      PubDate: 2014-11-14T06:46:26.105916-05:
      DOI: 10.1002/adfm.201402987
       
  • Mesostructured Intermetallic Compounds of Platinum and
           Non‐Transition Metals for Enhanced Electrocatalysis of Oxygen
           Reduction Reaction
    • Authors: Xing‐You Lang; Gao‐Feng Han, Bei‐Bei Xiao, Lin Gu, Zhen‐Zhong Yang, Zi Wen, Yong‐Fu Zhu, Ming Zhao, Jian‐Chen Li, Qing Jiang
      Pages: n/a - n/a
      Abstract: Alloying techniques show genuine potential to develop more effective catalysts than Pt for oxygen reduction reaction (ORR), which is the key challenge in many important electrochemical energy conversion and storage devices, such as fuel cells and metal‐air batteries. Tremendous efforts have been made to improve ORR activity by designing bimetallic nanocatalysts, which have been limited to only alloys of platinum and transition metals (TMs). The Pt‐TM alloys suffer from critical durability in acid‐media fuel cells. Here a new class of mesostructured Pt–Al catalysts is reported, consisting of atomic‐layer‐thick Pt skin and Pt3Al or Pt5Al intermetallic compound skeletons for the enhanced ORR performance. As a result of strong Pt–Al bonds that inhibit the evolution of Pt skin and produce ligand and compressive strain effects, the Pt3Al and Pt5Al mesoporous catalysts are exceptionally durable and ≈6.3‐ and ≈5.0‐fold more active than the state‐of‐the‐art Pt/C catalyst at 0.90 V, respectively. The high performance makes them promising candidates as cathode nanocatalysts in next‐generation fuel cells. A mesostructured ordered intermetallic of PtAl is developed by a facilely and cost‐effectively alloying/dealloying approach for the high‐performance ORR. The extremely strong covalent bonds between Pt and Al not only give rise to excellent kinetic stability, but also result in remarkable catalytic activity duo to the downshift of d‐band center.
      PubDate: 2014-11-14T06:46:18.180543-05:
      DOI: 10.1002/adfm.201401868
       
  • Response to Comment on Sponge‐Templated Preparation of High Surface
           Area Graphene with Ultrahigh Capacitive Deionization Performance
    • Authors: Zhi‐Yu Yang; Lin‐Jian Jin, Guo‐Qian Lu, Qing‐Qing Xiao, Yu‐Xia Zhang, Lin Jing, Xiao‐Xue Zhang, Yi‐Ming Yan, Ke‐Ning Sun
      Pages: n/a - n/a
      PubDate: 2014-11-14T06:41:24.363228-05:
      DOI: 10.1002/adfm.201403534
       
  • Comment on Sponge‐Templated Preparation of High Surface Area
           Graphene with Ultrahigh Capacitive Deionization Performance
    • Authors: Slawomir Porada; P. M. Biesheuvel, Volker Presser
      Pages: n/a - n/a
      PubDate: 2014-11-14T06:41:23.080532-05:
      DOI: 10.1002/adfm.201401101
       
  • Graphite Oxide and Aromatic Amines: Size Matters
    • Authors: Konstantinos Spyrou; Matteo Calvaresi, Evmorfia K. Diamanti, Theodoros Tsoufis, Dimitrios Gournis, Petra Rudolf, Francesco Zerbetto
      Pages: n/a - n/a
      Abstract: Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”. Experimental and theoretical approaches are combined to demonstrate the successful intercalation of common organic polycyclic aromatic compounds between the layers of graphite oxide, and to examine in detail the mechanism by which each molecule interacts with the graphene oxide surface. It is proved that the type of interaction for aniline and naphthalene amine with the graphene oxide layers differs according to the size of the aromatic molecules.
      PubDate: 2014-11-12T14:11:30.972886-05:
      DOI: 10.1002/adfm.201402622
       
  • Controlled Growth from ZnS Nanoparticles to ZnS–CdS Nanoparticle
           Hybrids with Enhanced Photoactivity
    • Authors: Xiaojie Xu; Linfeng Hu, Nan Gao, Shaoxiong Liu, Swelm Wageh, Ahmed A. Al‐Ghamdi, Ahmed Alshahrie, Xiaosheng Fang
      Pages: n/a - n/a
      Abstract: Chalcogenide nanostructures and nanocomposites have been the focus of semiconductor nanomaterial research due to their remarkable optoelectronic and photocatalytic properties and potential application in photodegrading enviromental pollutions. However, currently available synthesizing methods tend to be costly and inefficient. In this paper, we propose a facile two‐step solution‐phase method to synthesize well‐defined monodisperse ZnS–CdS nanocomposites. The morphology and size of ZnS nanoparticles can be easily controlled by adjusting the amount of the source of sulfur. After surface modification with tiny CdS nanoparticles through natural electrostatic attraction, uniform ZnS–CdS nanocomposites are obtained, which has been further confirmed by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The photocatalytic activities of various ZnS samples and ZnS–CdS nanocomposites have been investigated by degrading Rhodamine B under UV‐light. Compared with pure ZnS nanoparticles and ZnS powders, the as‐obtained ZnS–CdS nanocomposites exhibit excellent photocatalytic performances due to the effective charge separation and increased specific surface area by the attachment of CdS. Moreover, resulting from the effective passivation of surface electronic states, the photoluminescence intensity of the ZnS–CdS nanocomposites is also significantly improved relative to plain ZnS. Chalcogenide nanostructure has attracted world‐wide attention due to the great potential of applications in photocatalysis and optoelectronics. Well‐defined heterostructures, which often exhibit superior properties, are of extreme importance. In this paper, a facile method to synthesize monodisperse ZnS nanoparticles (NPs) and ZnS–CdS nanocomposites (NCs) is proposed. The ZnS–CdS heterostructure not only shows obvious advantage in photoactivities, but also offers exciting opportunities for the development of new dual‐semiconductor nanostructures.
      PubDate: 2014-11-11T14:08:47.286709-05:
      DOI: 10.1002/adfm.201403065
       
  • Nanofragmentation of Ferroelectric Domains During Polarization Fatigue
    • Authors: Hanzheng Guo; Xiaoming Liu, Jürgen Rödel, Xiaoli Tan
      Pages: n/a - n/a
      Abstract: The microscopic mechanism for polarization fatigue in ferroelectric oxides has remained an open issue for several decades in the condensed matter physics community. Even though numerous models are proposed, a consensus has yet to be reached. Since polarization reversal is realized through ferroelectric domains, their behavior during electric cycling is critical to elucidating the microstructural origin for the deteriorating performance. In this study, electric field in situ transmission electron microscopy is employed for the first time to reveal the domain dynamics at the nanoscale through more than 103 cycles of bipolar fields. A novel mechanism of domain fragmentation is directly visualized in polycrystalline [(Bi1/2Na1/2)0.95Ba0.05]0.98La0.02TiO3. Fragmented domains break the long‐range polar order and, together with domain wall pinning, contribute to the reduction of switchable polarization. Complimentary investigations into crystal structure and properties of this material corroborate our microscopic findings. A novel mechanism of polarization fatigue is visualized in situ in polycrystalline [(Bi1/2Na1/2)0.95Ba0.05]0.98La0.02TiO3 by using transimission electron microscopy. Complementary to domain wall pinning, nanoscale domain fragmentation is found to take place during bipolar electric cycling. The broken long range polar order in the nanofragments is primarily responsible for the fatigue behavior measured from bulk specimens.
      PubDate: 2014-11-11T14:08:24.696935-05:
      DOI: 10.1002/adfm.201402740
       
  • Charge Separation Dynamics and Opto‐Electronic Properties of a
           Diaminoterephthalate‐C60 Dyad
    • Authors: Stefano Pittalis; Alain Delgado, Jörg Robin, Lena Freimuth, Jens Christoffers, Christoph Lienau, Carlo Andrea Rozzi
      Pages: n/a - n/a
      Abstract: A novel dyad composed of a diaminoterephthalate scaffold, covalently linked to a fullerene derivative, is explored as a nanosized charge separation unit powered by solar energy. Its opto‐electronic properties are studied and the charge separation rate is determined. Simulations of the coupled electronic and nuclear dynamics in the Ehrenfest approximation are carried out on a sub 100 fs time scale after photoexcitation in order to gain insights about the mechanisms driving the charge separation. In particular, the role of vibronic coupling and of the detailed morphology are highlighted. Photoinduced charge separation occurs on a 100 fs time scale in a diaminoterephthalate‐C60 dyad. Quantum simulations are performed to study the excited state dynamics of a new dyad. The chemical flexibility and optical properties of the chromophore moiety make this system a particularly useful model to study the early steps in the photovoltaic energy conversion. The simulations clarify the influence of electron‐nuclei coupling and molecular conformation on the charge separation efficiency of the molecule.
      PubDate: 2014-11-10T09:44:16.257492-05:
      DOI: 10.1002/adfm.201402316
       
  • High‐Mobility ZnO Thin Film Transistors Based on
           Solution‐processed Hafnium Oxide Gate Dielectrics
    • Authors: Mazran Esro; George Vourlias, Christopher Somerton, William I. Milne, George Adamopoulos
      Pages: n/a - n/a
      Abstract: The properties of metal oxides with high dielectric constant (k) are being extensively studied for use as gate dielectric alternatives to silicon dioxide (SiO2). Despite their attractive properties, these high‐k dielectrics are usually manufactured using costly vacuum‐based techniques. In that respect, recent research has been focused on the development of alternative deposition methods based on solution‐processable metal oxides. Here, the application of the spray pyrolysis (SP) technique for processing high‐quality hafnium oxide (HfO2) gate dielectrics and their implementation in thin film transistors employing spray‐coated zinc oxide (ZnO) semiconducting channels are reported. The films are studied by means of admittance spectroscopy, atomic force microscopy, X‐ray diffraction, UV–Visible absorption spectroscopy, FTIR, spectroscopic ellipsometry, and field‐effect measurements. Analyses reveal polycrystalline HfO2 layers of monoclinic structure that exhibit wide band gap (≈5.7 eV), low roughness (≈0.8 nm), high dielectric constant (k ≈ 18.8), and high breakdown voltage (≈2.7 MV/cm). Thin film transistors based on HfO2/ZnO stacks exhibit excellent electron transport characteristics with low operating voltages (≈6 V), high on/off current modulation ratio (∼107) and electron mobility in excess of 40 cm2 V−1 s−1. Solution‐processed metal oxide thin film transistors (TFTs) employing sequential spray coated antimony‐doped tin oxide (SnO2:Sb) gate electrodes, hafnium oxide (HfO2) gate dielectrics and zinc oxide (ZnO) semiconducting channels are demonstrated. The transistors show excellent characteristics in terms of high transparency, hysteresis‐free operation, low operation voltage, high electron mobility and On/Off current modulation ratio.
      PubDate: 2014-11-10T09:22:22.546066-05:
      DOI: 10.1002/adfm.201402684
       
  • Silicon‐Based Current‐Controlled Reconfigurable
           Magnetoresistance Logic Combined with Non‐Volatile Memory
    • Authors: Zhaochu Luo; Xiaozhong Zhang, Chengyue Xiong, Jiaojiao Chen
      Pages: n/a - n/a
      Abstract: Silicon‐based complementary metal‐oxide‐semiconductor (CMOS) transistors have achieved great success. However, the traditional development pathway is approaching its fundamental limits. Magnetoelectronics logic, especially magnetic‐field‐based logic, shows promise for surpassing the development limits of CMOS logic and arouses profound attentions. Existing proposals of magnetic‐field‐based logic are based on exotic semiconductors and difficult for further technological implementation. Here, a kind of diode‐assisted geometry‐enhanced low‐magnetic‐field magnetoresistance (MR) mechanism is proposed. It couples p‐n junction's nonlinear transport characteristic and Lorentz force by geometry, and shows extremely large low‐magnetic‐field MR (>120% at 0.15 T). Further, it is applied to experimentally demonstrate current‐controlled reconfigurable magnetoresistance logic on the silicon platform at room temperature. This logic device could perform all four basic Boolean logic including AND, OR, NAND and NOR in one device. Combined with non‐volatile magnetic memory, this logic architecture with unique magnetoelectric properties has the advantages of current‐controlled reconfiguration, zero refresh consumption, instant‐on performance and would bridge the processor‐memory gap. Our findings would pave the way in silicon‐based magnetoelectronics and offer a route to make a new kind of microprocessor with potential of high performance. Magnetoelectronics logic shows promise for surpassing the development limits of CMOS logic and arouses profound attentions. Here, silicon‐based current‐controlled reconfigurable magnetoresistance logic is experimentally demonstrated. This logic device performs four basic Boolean logic (AND, OR, NAND, and NOR) in one device. It has the advantages of reconfiguration, ultralow consumption, instant‐on performance and would bridge the processor‐memory gap.
      PubDate: 2014-11-10T09:21:44.433721-05:
      DOI: 10.1002/adfm.201402955
       
  • Integration of 2D and 3D Thin Film Glassy Carbon Electrode Arrays for
           Electrochemical Dopamine Sensing in Flexible Neuroelectronic Implants
    • Authors: Jules J. VanDersarl; André Mercanzini, Philippe Renaud
      Pages: n/a - n/a
      Abstract: Here we present the development and characterization of a flexible implantable neural probe with glassy carbon electrode arrays. The use of carbon electrodes allows for these devices to be used as chemical sensors, in addition to their typical use as electrical sensors and stimulators. The devices are fabricated out of polyimide, platinum, titanium, and carbon with standard microfabrication techniques on carrier wafers. The devices are released from the substrate through either chemical or electrochemical dissolution of the underlying substrate material. The glassy carbon electrode arrays are produced through the pyrolysis of SU‐8 pillars at 900 °C as the first process step, as this temperature is incompatible with the other device materials. The process demonstrated here is generally applicable, allowing for the integration of various high temperature materials into flexible devices. Incorporating glassy carbon electrodes into flexible neural probes allows for implants to be used as chemical sensors as well as electrical sensors and stimulators. The devices are microfabricated on carrier wafers out of polyimide, platinum, titanium, and glassy carbon. The process demonstrated here is generally applicable for the integration of various high temperature materials into flexible devices.
      PubDate: 2014-11-06T06:13:25.222504-05:
      DOI: 10.1002/adfm.201402934
       
  • Controlling the Self‐Assembly of Periodic Defect Patterns in Smectic
           Liquid Crystal Films with Electric Fields
    • Authors: Iryna Gryn; Emmanuelle Lacaze, Roberto Bartolino, Bruno Zappone
      Pages: n/a - n/a
      Abstract: Large‐area periodic defect patterns are produced in smectic A liquid crystals confined between rigid plate electrodes that impose conflicting parallel and normal anchoring conditions, inducing the formation of topological defects. Highly oriented stripe patterns are created in samples thinner than 2 μm due to self‐assembly of linear defect domains with period smaller than 4 μm, whereas hexagonal lattices of focal conic domains appear for thicker samples. The pattern type (1d/2d) and period can be controlled at the nematic–smectic phase transition by applying an electric field, which confines the defect domains to a thin surface layer with thickness comparable to the nematic coherence length. The pattern morphology persists in the smectic phase even after varying the field or switching it off. Bistable, non‐equilibrium patterns are stabilized by topological constraints of the smectic phase that hinder the rearrangement of defects in response to field variations. Rapid formation of periodic defect patterns can be induced and controlled in smectic liquid crystal films by applying electric fields and varying the film thickness at the smectic‐nematic phase transition. The pattern type (1d/2d) and period persist in the smectic phase in a non‐equilibrium state, stabilized by large topological barriers, even after switching the field off.
      PubDate: 2014-11-06T06:13:21.301893-05:
      DOI: 10.1002/adfm.201402875
       
  • Enhanced Vertical Charge Transport in a Semiconducting P3HT Thin Film on
           Single Layer Graphene
    • Authors: Vasyl Skrypnychuk; Nicolas Boulanger, Victor Yu, Michael Hilke, Stefan C. B. Mannsfeld, Michael F. Toney, David R. Barbero
      Pages: n/a - n/a
      Abstract: The crystallization and electrical characterization of the semiconducting polymer poly(3‐hexylthiophene) (P3HT) on a single layer graphene sheet is reported. Grazing incidence X‐ray diffraction revealed that P3HT crystallizes with a mixture of face‐on and edge‐on lamellar orientations on graphene compared to mainly edge‐on on a silicon substrate. Moreover, whereas ultrathin (10 nm) P3HT films form well oriented face‐on and edge‐on lamellae, thicker (50 nm) films form a mosaic of lamellae oriented at different angles from the graphene substrate. This mosaic of crystallites with π–π stacking oriented homogeneously at various angles inside the film favors the creation of a continuous pathway of interconnected crystallites, and results in a strong enhancement in vertical charge transport and charge carrier mobility in the thicker P3HT film. These results provide a better understanding of polythiophene crystallization on graphene, and should help the design of more efficient graphene based organic devices by control of the crystallinity of the semiconducting film. The crystallinity and the electrical properties of thin films of the semiconducting polymer poly‐3‐hexylthiophene are investigated on a single layer of graphene. Enhanced vertical charge transport and a much higher charge carrier mobility are measured in thicker films due to the face‐on orientation induced by the graphene substrate and the formation of an interconnected path of crystallites.
      PubDate: 2014-11-06T06:13:17.562732-05:
      DOI: 10.1002/adfm.201403418
       
  • Kinetic Monte Carlo Study of the Sensitivity of OLED Efficiency and
           Lifetime to Materials Parameters
    • Authors: Reinder Coehoorn; Harm van Eersel, Peter Bobbert, René Janssen
      Pages: n/a - n/a
      Abstract: The performance of organic light‐emitting diodes (OLEDs) is determined by a complex interplay of the optoelectronic processes in the active layer stack. In order to enable simulation‐assisted layer stack development, a three‐dimensional kinetic Monte Carlo OLED simulation method which includes the charge transport and all excitonic processes is developed. In this paper, the results are presented of simulations including degradation processes in idealized but realizable phosphorescent OLEDs. Degradation is treated as a result of the conversion of emitter molecules to non‐emissive sites upon a triplet‐polaron quenching (TPQ) process. Under the assumptions made, TPQ provides the dominant contribution to the roll‐off. There is therefore a strong relationship between the roll‐off and the lifetime. This is quantified using a “uniform density model”, within which the charge carrier and exciton densities are assumed to be uniform across the emissive layer. The simulations give rise to design rules regarding the energy levels, and are used to study the sensitivity of the roll‐off and lifetime to various other materials parameters, including the mobility, the phosphorescent dye concentration, the triplet exciton emissive lifetime and binding energy, and the type of TPQ process. Kinetic Monte Carlo simulations are used to mechanistically analyze the influence of the organic semiconductor materials properties on the luminance decay due to degradation processes in phosphorescent organic light emitting diodes. A relationship is established between the lifetime and the efficiency roll‐off with increasing current density, assuming triplet‐polaron quenching processes as the root‐cause of the degradation, and design rules regarding the energy levels are developed.
      PubDate: 2014-11-04T02:54:04.945979-05:
      DOI: 10.1002/adfm.201402532
       
  • All‐Metallic Vertical Transistors Based on Stacked Dirac Materials
    • Authors: Yangyang Wang; Zeyuan Ni, Qihang Liu, Ruge Quhe, Jiaxin Zheng, Meng Ye, Dapeng Yu, Junjie Shi, Jinbo Yang, Ju Li, Jing Lu
      Pages: n/a - n/a
      Abstract: It is an ongoing pursuit to use metal as a channel material in a field effect transistor. All metallic transistor can be fabricated from pristine semimetallic Dirac materials (such as graphene, silicene, and germanene), but the on/off current ratio is very low. In a vertical heterostructure composed by two Dirac materials, the Dirac cones of the two materials survive the weak interlayer van der Waals interaction based on density functional theory method, and electron transport from the Dirac cone of one material to the one of the other material is therefore forbidden without assistance of phonon because of momentum mismatch. First‐principles quantum transport simulations of the all‐metallic vertical Dirac material heterostructure devices confirm the existence of a transport gap of over 0.4 eV, accompanied by a switching ratio of over 104. Such a striking behavior is robust against the relative rotation between the two Dirac materials and can be extended to twisted bilayer graphene. Therefore, all‐metallic junction can be a semiconductor and novel avenue is opened up for Dirac material vertical structures in high‐performance devices without opening their band gaps. Electron transport from one Dirac material to the other near E f is forbidden by momentum mismatch if the two Dirac cones of different layers are well separated. All‐metallic field effect transistor can be designed out of Dirac materials with a large transport gap and a high on/off current ratio of over 104 based on ab initio quantum transport simulations.
      PubDate: 2014-11-03T13:19:46.262995-05:
      DOI: 10.1002/adfm.201402904
       
  • Unraveling the Sinuous Grain Boundaries in Graphene
    • Authors: Zhuhua Zhang; Yang Yang, Fangbo Xu, Luqing Wang, Boris I. Yakobson
      Pages: n/a - n/a
      Abstract: Grain boundaries (GBs) in graphene are stable strings of pentagon‐heptagon dislocations. The GBs have been believed to favor an alignment of dislocations, but increasing number of experiments reveal diversely sinuous GB structures whose origins have long been elusive. Based on dislocation theory and first‐principles calculations, an extensive analysis of the graphene GBs is conducted and it is revealed that the sinuous GB structures, albeit being longer than the straight forms, can be energetically optimal once the global GB line cannot bisect the tilt angle. The unusually favorable sinuous GBs can actually decompose into a series of well‐defined bisector segments that effectively relieve the in‐plane stress of edge dislocations, and the established atomic structures closely resemble recent experimental images of typical GBs. In contrast to previously used models, the sinuous GBs show improved mechanical properties and are distinguished by a sizable electronic transport gap, which may open potential applications of polycrystalline graphene in functional devices. Grain boundaries are intrinsic to polycrystalline graphene and often exhibit diversely sinuous structures. Here, it is revealed that the sinuous grain boundaries are energetically preferred over the straight forms when the grain division is asymmetric, and their well‐defined configurations agree well with experimental observations. Importantly, such grain boundaries show improved strength as well as uniformly semiconducting electronic transport behavior.
      PubDate: 2014-10-31T11:31:16.244176-05:
      DOI: 10.1002/adfm.201403024
       
  • Using Polymer Electrolyte Gates to Set‐and‐Freeze Threshold
           Voltage and Local Potential in Nanowire‐based Devices and
           Thermoelectrics
    • Authors: Sofia Fahlvik Svensson; Adam M. Burke, Damon J. Carrad, Martin Leijnse, Heiner Linke, Adam P. Micolich
      Pages: n/a - n/a
      Abstract: The strongly temperature‐dependent ionic mobility in polymer electrolytes is used to “freeze in” specific ionic charge environments around a nanowire using a local wrap‐gate geometry. This makes it possible to set both the threshold voltage for a conventional doped substrate gate and the local disorder potential at temperatures below 220 K. These are characterized in detail by combining conductance and thermovoltage measurements with modeling. The results demonstrate that local polymer electrolyte gates are compatible with nanowire thermoelectrics, where they offer the advantage of a very low thermal conductivity, and hold great potential towards setting the optimal operating point for solid‐state cooling applications. A nanoscale patterned polymer electrolyte gate is used to “freeze in” ionic charge environments at low temperatures around an indium arsenide nanowire. The low thermal conductivity of the local wrap‐gate allows side‐by‐side investigations of the conductance and thermoelectric properties of the gated nanowire segment over a series of biases applied to the polymer electrolyte.
      PubDate: 2014-10-31T11:26:27.136249-05:
      DOI: 10.1002/adfm.201402921
       
  • Proteins: Materials Fabrication from Native and Recombinant Thermoplastic
           Squid Proteins (Adv. Funct. Mater. 47/2014)
    • Authors: Abdon Pena‐Francesch; Sergio Florez, Huihun Jung, Aswathy Sebastian, Istvan Albert, Wayne Curtis, Melik C. Demirel
      Pages: 7393 - 7393
      Abstract: Squid ring teeth complex extracted from Loligo vulgaris shows reversible solid to melt phase transition on page 7401. M. C. Demirel and team show how the 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.
      PubDate: 2014-12-12T01:14:22.95661-05:0
      DOI: 10.1002/adfm.201470302
       
  • Photovoltaics: Post‐Deposition Activation of Latent
           Hydrogen‐Bonding: A New Paradigm for Enhancing the Performances of
           Bulk Heterojunction Solar Cells (Adv. Funct. Mater. 47/2014)
    • Authors: Francesco Bruni; Mauro Sassi, Marcello Campione, Umberto Giovanella, Riccardo Ruffo, Silvia Luzzati, Francesco Meinardi, Luca Beverina, Sergio Brovelli
      Pages: 7394 - 7394
      Abstract: On page 7410, L. Beverina, S. Brovelli, and co‐workers demonstrate a new paradigm for fine tuning the phase segregation in small‐molecule solar cells based on the post‐deposition exploitation of latent hydrogen bonding. Thermally activating latent conjugated pigments fine‐tunes and stabilizes the nanoscale film connectivity, thereby simultaneously optimizing charge generation and transport processes, resulting in over 20‐fold increase of the photovoltaic efficiency.
      PubDate: 2014-12-12T01:14:24.044019-05:
      DOI: 10.1002/adfm.201470303
       
  • Contents: (Adv. Funct. Mater. 47/2014)
    • Pages: 7395 - 7400
      PubDate: 2014-12-12T01:14:23.44094-05:0
      DOI: 10.1002/adfm.201470304
       
  • Materials Fabrication from Native and Recombinant Thermoplastic Squid
           Proteins
    • Authors: Abdon Pena‐Francesch; Sergio Florez, Huihun Jung, Aswathy Sebastian, Istvan Albert, Wayne Curtis, Melik C. Demirel
      Pages: 7401 - 7409
      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
       
  • 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: 7410 - 7419
      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 20‐fold increase with respect to control devices.
      PubDate: 2014-09-11T12:55:28.646271-05:
      DOI: 10.1002/adfm.201400896
       
  • 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: 7420 - 7426
      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
       
  • Nanograined Half‐Heusler Semiconductors as Advanced Thermoelectrics:
           An Ab Initio High‐Throughput Statistical Study
    • Authors: Jesús Carrete; Natalio Mingo, Shidong Wang, Stefano Curtarolo
      Pages: 7427 - 7432
      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 AFLOWLIB.org 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 AFLOWLIB.org 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
       
  • High‐Performance Hybrid Supercapacitor Enabled by a High‐Rate
           Si‐based Anode
    • Authors: Ran Yi; Shuru Chen, Jiangxuan Song, Mikhail L. Gordin, Ayyakkannu Manivannan, Donghai Wang
      Pages: 7433 - 7439
      Abstract: A hybrid supercapacitor constructed of a Si‐based anode and a porous carbon cathode is demonstrated with both high power and energy densities. Boron‐doping is employed to improve the rate capability of the Si‐based anode (B‐Si/SiO2/C). At a high current density of 6.4 A/g, B‐Si/SiO2/C delivers a capacity of 685 mAh/g, 2.4 times that of the undoped Si/SiO2/C. Benefiting from the high rate performance along with low working voltage, high capacity, and good cycling stability of B‐Si/SiO2/C, the hybrid supercapacitor exhibits a high energy density of 128 Wh/kg at 1229 W/kg. Even when power density increases to the level of a conventional supercapacitor (9704 W/kg), 89 Wh/kg can be obtained, the highest values of any hybrid supercapacitor to date. Long cycling life (capacity retention of 70% after 6000 cycles) and low self‐discharge rate (voltage retention of 82% after 50 hours) are also achieved. This work opens an avenue for development of high‐performance hybrid supercapacitors using high‐performance Si‐based anodes. A hybrid supercapacitor is constructed with a high‐rate Si‐based anode and a porous carbon cathode. The hybrid supercapacitor exhibits a high energy density of 128 Wh/kg at 1229 W/kg. Even when power density increases to the level of a conventional supercapacitor (9704 W/kg), 89 Wh/kg can be obtained. Long cycling life and low self‐discharge rate are also achieved.
      PubDate: 2014-09-22T07:20:47.522239-05:
      DOI: 10.1002/adfm.201402398
       
  • General Formation of MS (M = Ni, Cu, Mn) Box‐in‐Box Hollow
           Structures with Enhanced Pseudocapacitive Properties
    • Authors: Xin‐Yao Yu; Le Yu, Laifa Shen, Xiaohui Song, Hongyu Chen, Xiong Wen (David) Lou
      Pages: 7440 - 7446
      Abstract: Complex hollow structures of metal sulfides could be promising materials for energy storage devices such as supercapacitors and lithium‐ion batteries. However, it is still a great challenge to fabricate well‐defined metal sulfides hollow structures with multi‐shells, hierarchical architectures, and non‐spherical shape. In this work, a template‐engaged strategy is developed to synthesize hierarchical NiS box‐in‐box hollow structures with double‐shells. The NiS box‐in‐box hollow structures constructed by ultrathin nanosheets are evaluated as electrode materials for supercapacitors. As expected, the NiS box‐in‐box hollow structures exhibit excellent rate performance and impressive cycling stability due to their unique nano‐architecture. More importantly, the synthetic method can be easily extended to synthesize other transition metal sulfides box‐in‐box hollow structures. For example, we have also successfully synthesized similar CuS and MnS box‐in‐box hollow structures. The present work makes a significant contribution to the design and synthesis of transition metal sulfides hollow structures with non‐spherical shape and complex architecture, as well as their potential applications in electrochemical energy storage. Box in box: A template‐engaged method is successfully developed to synthesize hierarchical metal sulfide (NiS, CuS, MnS) box‐in‐box hollow structures with double‐shells. As an example, it is demonstrated that the NiS box‐in‐box hollow structure exhibits excellent pseudocapacitive performance with remarkable rate performance and cycling stability.
      PubDate: 2014-09-22T07:17:13.039836-05:
      DOI: 10.1002/adfm.201402560
       
  • Memristors: Memristor Kinetics and Diffusion Characteristics for Mixed
           Anionic‐Electronic SrTiO3‐δ Bits: The
           Memristor‐Based Cottrell Analysis Connecting Material to Device
           Performance (Adv. Funct. Mater. 47/2014)
    • Authors: Felix Messerschmitt; Markus Kubicek, Sebastian Schweiger, Jennifer L.M. Rupp
      Pages: 7447 - 7447
      Abstract: The Memristor‐based Cottrell analysis to derive material‐dependent diffusion characteristics is demonstrated on page 7448 by J. L. M. Rupp and co‐workers for mixed anionic‐electronic conducting resistive switches. The integrated strategy is for the first time exemplified for stable switching bits based on the model material SrTiO3−δ. Involved defects and their kinetics play a key role to define material selection strategies and lead the way to enhanced performance metal oxide‐based memristors in the future.
      PubDate: 2014-12-12T01:14:21.544414-05:
      DOI: 10.1002/adfm.201470305
       
  • Memristor Kinetics and Diffusion Characteristics for Mixed
           Anionic‐Electronic SrTiO3‐δ Bits: The
           Memristor‐Based Cottrell Analysis Connecting Material to Device
           Performance
    • Authors: Felix Messerschmitt; Markus Kubicek, Sebastian Schweiger, Jennifer L.M. Rupp
      Pages: 7448 - 7460
      Abstract: Memristors based on mixed anionic‐electronic conducting oxides are promising devices for future data storage and information technology with applications such as non‐volatile memory or neuromorphic computing. Unlike transistors solely operating on electronic carriers, these memristors rely, in their switch characteristics, on defect kinetics of both oxygen vacancies and electronic carriers through a valence change mechanism. Here, Pt SrTiO3‐δ Pt structures are fabricated as a model material in terms of its mixed defects which show stable resistive switching. To date, experimental proof for memristance is characterized in hysteretic current–voltage profiles; however, the mixed anionic‐electronic defect kinetics that can describe the material characteristics in the dynamic resistive switching are still missing. It is shown that chronoamperometry and bias‐dependent resistive measurements are powerful methods to gain complimentary insights into material‐dependent diffusion characteristics of memristors. For example, capacitive, memristive and limiting currents towards the equilibrium state can successfully be separated. The memristor‐based Cottrell analysis is proposed to study diffusion kinetics for mixed conducting memristor materials. It is found that oxygen diffusion coefficients increase up to 3 × 10–15 m2s–1 for applied bias up to 3.8 V for SrTiO3‐δ memristors. These newly accessible diffusion characteristics allow for improving materials and implicate field strength requirements to optimize operation towards enhanced performance metrics for valence change memristors. The strategy for studying material‐dependent diffusion characteristics for mixed conducting memristors is extended by applying chronoamperometry and bias‐dependent resistive measurements. The memristor‐based Cottrell analysis and equation is proposed to derive oxygen diffusion coefficients of 3 × 10−15 m2s−1 for bias increase up to 3.8 V for SrTiO3‐δ memristors at room temperature.
      PubDate: 2014-09-25T06:34:05.601165-05:
      DOI: 10.1002/adfm.201402286
       
  • Wafer Scale Synthesis and High Resolution Structural Characterization of
           Atomically Thin MoS2 Layers
    • Authors: Aaron S. George; Zafer Mutlu, Robert Ionescu, Ryan J. Wu, Jong S. Jeong, Hamed H. Bay, Yu Chai, K. Andre Mkhoyan, Mihrimah Ozkan, Cengiz S. Ozkan
      Pages: 7461 - 7466
      Abstract: Synthesis of atomically thin MoS2 layers and its derivatives with large‐area uniformity is an essential step to exploit the advanced properties of MoS2 for their possible applications in electronic and optoelectronic devices. In this work, a facile method is reported for the continuous synthesis of atomically thin MoS2 layers at wafer scale through thermolysis of a spin coated‐ammonium tetrathiomolybdate film. The thickness and surface morphology of the sheets are characterized by atomic force microscopy. The optical properties are studied by UV–Visible absorption, Raman and photoluminescence spectroscopies. The compositional analysis of the layers is done by X‐ray photo­emission spectroscopy. The atomic structure and morphology of the grains in the polycrystalline MoS2 atomic layers are examined by high‐angle annular dark‐field scanning transmission electron microscopy. The electron mobilities of the sheets are evaluated using back‐gate field‐effect transistor configuration. The results indicate that this facile method is a promising approach to synthesize MoS2 thin films at the wafer scale and can also be applied to synthesis of WS2 and hybrid MoS2‐WS2 thin layers. Wafer scale synthesis of atomically thin MoS2 layers via thermolysis of spin coated films is presented. High resolution characterization of atomically thin layers is performed by HAADF‐STEM image analysis. This approach could be applied to a variety of substrates and provides a promising route towards wafer scale production of other TMD and doped materials for applications in electronics and optoelectronics.
      PubDate: 2014-09-30T13:44:12.124433-05:
      DOI: 10.1002/adfm.201402519
       
  • Photosystem I‐based Biophotovoltaics on Nanostructured Hematite
    • Authors: Kasim Ocakoglu; Tomasz Krupnik, Bart van den Bosch, Ersan Harputlu, Maria Pia Gullo, Julian David Janna Olmos, Saadet Yildirimcan, Ram K. Gupta, Fahrettin Yakuphanoglu, Andrea Barbieri, Joost N. H. Reek, Joanna Kargul
      Pages: 7467 - 7477
      Abstract: The electronic coupling between a robust red algal photosystem I (PSI) associated with its light harvesting antenna (LHCI) and nanocrystalline n‐type semiconductors, TiO2 and hematite (α‐Fe2O3) is utilized for fabrication of the biohybrid dye‐sensitized solar cells (DSSC). PSI‐LHCI is immobilized as a structured multilayer over both semiconductors organized as highly ordered nanocrystalline arrays, as evidenced by FE‐SEM and XRD spectroscopy. Of all the biohybrid DSSCs examined, α‐Fe2O3/PSI‐LHCI biophotoanode operates at a highest quantum efficiency and generates the largest open circuit photo­current compared to the tandem system based on TiO2/PSI‐LHCI material. This is accomplished by immobilization of the PSI‐LHCI complex with its reducing side towards the hematite surface and nanostructuring of the PSI‐LHCI multilayer in which the subsequent layers of this complex are organized in the head‐to‐tail orientation. The biohybrid PSI‐LHCI‐DSSC is capable of sustained photoelectrochemical H2 production upon illumination with visible light above 590 nm. Although the solar conversion efficiency of the PSI‐LHCI/hematite DSSC is currently below a practical use, the system provides a blueprint for a genuinely green solar cell that can be used for molecular hydrogen production at a rate of 744 μmoles H2 mg Chl−1 h−1, placing it amongst the best performing biohybrid solar‐to‐fuel nanodevices. A fully integrated, stable, and functional photosystem I‐based biohybrid dye‐sensitized solar cell is constructed with an improved solar‐to‐electric quantum efficiency over previously reported biohybrid devices. A highly robust oriented Cyanidioschyzon merolae PSI‐LHCI complex is used as a natural photosensitizer of the nanostructured hematite substrate for the sustained photodriven H2 production.
      PubDate: 2014-10-02T02:05:46.842898-05:
      DOI: 10.1002/adfm.201401399
       
  • Room Temperature Ferrimagnetism and Ferroelectricity in Strained, Thin
           Films of BiFe0.5Mn0.5O3
    • Authors: Eun‐Mi Choi; Thomas Fix, Ahmed Kursumovic, Christy J. Kinane, Darío Arena, Suman‐Lata Sahonta, Zhenxing Bi, Jie Xiong, Li Yan, Jun‐Sik Lee, Haiyan Wang, Sean Langridge, Young‐Min Kim, Albina Y. Borisevich, Ian MacLaren, Quentin M. Ramasse, Mark G. Blamire, Quanxi Jia, Judith L. MacManus‐Driscoll
      Pages: 7478 - 7487
      Abstract: Highly strained films of BiFe0.5Mn0.5O3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ∼ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (∼ 0.58 μB/f.u) on high quality (001) SrTiO3. X‐ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe3+ and Mn3+. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above. A new window for designing multiferroic materials through epitaxial strain control: For the first time, coexistent ferrimagnetism and ferroelectricity is demonstrated at RT in BiFe0.5Mn0.5O3 (BFMO) by strain engineering. The most highly strained and crystalline films have a ferrimagnetic transition temperature of ≈600 K, which is 500 K higher than bulk BMO and a piezoresponse amplitude of 45 pm/V.
      PubDate: 2014-10-14T11:31:03.495917-05:
      DOI: 10.1002/adfm.201401464
       
  • Self‐Powered Trajectory, Velocity, and Acceleration Tracking of a
           Moving Object/Body using a Triboelectric Sensor
    • Authors: Fang Yi; Long Lin, Simiao Niu, Jin Yang, Wenzhuo Wu, Sihong Wang, Qingliang Liao, Yue Zhang, Zhong Lin Wang
      Pages: 7488 - 7494
      Abstract: Motion tracking is of great importance in a wide range of fields such as automation, robotics, security, sports and entertainment. Here, a self‐powered, single‐electrode‐based triboelectric sensor (TES) is reported to accurately detect the movement of a moving object/body in two dimensions. Based on the coupling of triboelectric effect and electrostatic induction, the movement of an object on the top surface of a polytetrafluoroethylene (PTFE) layer induces changes in the electrical potential of the patterned aluminum electrodes underneath. From the measurements of the output performance (open‐circuit voltage and short‐circuit current), the motion information about the object, such as trajectory, velocity, and acceleration is derived in conformity with the preset values. Moreover, the TES can detect motions of more than one objects moving at the same time. In addition, applications of the TES are demonstrated by using LED illuminations as real‐time indicators to visualize the movement of a sliding object and the walking steps of a person. A self‐powered, single‐electrode‐based triboelectric sensor is reported to accurately detect the movement of an object/body in two dimensions. Based on the coupling of triboelectric effect and electrostatic induction, the motion information about the object, such as trajectory, velocity, and acceleration, is derived in conformity with the preset values.
      PubDate: 2014-10-06T23:57:42.538047-05:
      DOI: 10.1002/adfm.201402703
       
  • Flexible Solid‐State Supercapacitor Based on Graphene‐based
           Hybrid Films
    • Authors: Meng Li; Zhe Tang, Mei Leng, Junmin Xue
      Pages: 7495 - 7502
      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
       
  • 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: 7503 - 7509
      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
       
  • Dendrimer‐Encapsulated Ruthenium Oxide Nanoparticles as Catalysts in
           Lithium‐Oxygen Batteries
    • Authors: Priyanka Bhattacharya; Eduard N. Nasybulin, Mark H. Engelhard, Libor Kovarik, Mark E. Bowden, Xiaohong S. Li, Daniel J. Gaspar, Wu Xu, Ji‐Guang Zhang
      Pages: 7510 - 7519
      Abstract: Dendrimer‐encapsulated ruthenium oxide nanoparticles (DEN‐RuO2) have been used as catalysts in lithium‐oxygen (Li‐O2) batteries for the first time. The results obtained from ultraviolet‐visible spectroscopy, electron microscopy and X‐ray photoelectron spectroscopy show that the nanoparticles synthesized by the dendrimer template method are ruthenium oxide, not metallic ruthenium as reported by other groups. The DEN‐RuO2 significantly improves the cycling stability of Li‐O2 batteries with carbon electrodes and decreases the charging potential even at ten times less catalyst loading than those reported previously. The monodispersity, porosity, and large number of surface functionalities of the dendrimer template prevent the aggregation of the RuO2 nanoparticles, making their entire surface area available for catalysis. The potential of using DEN‐RuO2 as a standalone cathode material for Li‐O2 batteries is also explored. Dendrimer‐encapsulated ruthenium nano­particles are readily oxidized to RuO2 when exposed to ambient conditions. These nanoparticles are used as catalysts in Li‐O2 batteries, which exhibited improved cycling thus suggesting that porous dendrimer‐encapsulated nanoparticles can be used to achieve superior performance in energy storage systems.
      PubDate: 2014-09-17T07:27:25.718797-05:
      DOI: 10.1002/adfm.201402701
       
  • Pd–Cu Bimetallic Tripods: A Mechanistic Understanding of the
           Synthesis and Their Enhanced Electrocatalytic Activity for Formic Acid
           Oxidation
    • Authors: Lei Zhang; Sang‐Il Choi, Jing Tao, Hsin‐Chieh Peng, Shuifen Xie, Yimei Zhu, Zhaoxiong Xie, Younan Xia
      Pages: 7520 - 7529
      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 eightfold 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
       
  • Ortho‐ vs Bay‐Functionalization: A Comparative Study on
           Tetracyano‐Terrylenediimides
    • Authors: Glauco Battagliarin; Sreenivasa Reddy Puniredd, Sebastian Stappert, Wojciech Zajaczkowski, Suhao Wang, Chen Li, Wojciech Pisula, Klaus Müllen
      Pages: 7530 - 7537
      Abstract: In this paper n‐type semiconductors synthesized via selective fourfold cyanation of the ortho‐ and bay‐positions (2,5,10,13‐ and 1,6,9,14‐positions respectively) of teyrrylenediimides are reported. A detailed study about the impact of the diverse functionalization topologies on the optoelectronic properties, self‐organization from solution, solid‐state packing, and charge carrier transport in field‐effect transistors is presented. The ortho‐substitution preserves the planarity of the core and favors high order in solution processed films. However, the strong intermolecular interactions lead to a microstructure with large aggregates and pronounced grain boundaries which lower the charge carrier transport in transistors. In contrast, the well‐soluble bay‐functionalized terrylenediimide forms only disordered films which surprisingly result in n‐type average mobilities of 0.17 cm2/Vs after drop‐casting with similar values in air. Processing by solvent vapor diffusion enhances the transport to 0.65 cm2/Vs by slight improvement of the order and surface arrangement of the molecules. This mobility is comparable to highest n‐type conductivities measured for solution processed PDI derivatives demonstrating the high potential of TDI‐based semiconductors. Ortho‐ or bay‐tetracyanation? A comparative study on terrylenediimide reveals that the two functionalizations have similar impact on the optoelectronic properties, but remarkably different effects on self‐assembling from solution, with striking consequences on the n‐type behavior in field‐effect transistors. The pronounced electron mobilities here reported for the bay‐tetracyano derivative demonstrate the high potential of terrylenediimide as scaffold for n‐type semiconductors.
      PubDate: 2014-09-29T02:48:56.64124-05:0
      DOI: 10.1002/adfm.201401573
       
  • Chain Length Dependence of the Photovoltaic Properties of Monodisperse
           Donor–Acceptor Oligomers as Model Compounds of Polydisperse Low Band
           Gap Polymers
    • Authors: Cheng Zhou; Yamin Liang, Feng Liu, Chen Sun, Xuelong Huang, Zengqi Xie, Fei Huang, Jean Roncali, Thomas P. Russell, Yong Cao
      Pages: 7538 - 7547
      Abstract: Well‐defined conjugated oligomers (Sn) containing from 1 to 8 units of a tricyclic building block involving a dioctyloxybenzothiadiazole unit with two thienyl side rings (S1) are synthesized by a bottom‐up approach. UV–Vis absorption data of solutions show that chain extension produces a narrowing of the HOMO–LUMO gap (ΔE) to values slightly smaller than that of the parent polymer (P1). Plots of ΔE and of the band gap of films (E g) versus the reciprocal chain length show that ΔE and E g converge towards a limit corresponding to an effective conjugation length (ECL) of 7–8 S1 units. UV–Vis absorption and photoluminescence data of solutions and solid films show that chain extension enhances the propensity to inter‐chain aggregation. This conclusion is confirmed by GIXD analyses which reveal that the edge‐on orientation of short‐chain systems evolves toward a face‐on orientation as chain length increases while the π‐stacking distance decreases beyond 7 units. The results obtained on solution‐processed BHJ solar cells show a progressive improvement of power conversion efficiency (PCE) with chain extension; however, the convergence limit of PCE remains inferior to that obtained with the polymer. These results are discussed with regard to the role of mono/polydispersity and chain aggregation. A series of donor–acceptor monodisperse oligomers (S1 –S8) and two analogous polydisperse polymers (P1, P2) are synthesized successfully. These materials serve as a model system to understand the relationship between conjugation length and the photophysical, morphological, and photovoltaic properties in donor–acceptor polymer solar cell materials, and provide a bridge between small molecules and the polymers.
      PubDate: 2014-10-06T05:56:21.120346-05:
      DOI: 10.1002/adfm.201401945
       
  • Highly Stretchable Conductors Integrated with a Conductive Carbon
           Nanotube/Graphene Network and 3D Porous Poly(dimethylsiloxane)
    • Authors: Mengting Chen; Ling Zhang, Shasha Duan, Shilong Jing, Hao Jiang, Chunzhong Li
      Pages: 7548 - 7556
      Abstract: Here, a novel and facile method is reported for manufacturing a new stretchable conductive material that integrates a hybrid three dimensional (3D) carbon nanotube (CNT)/reduced graphene oxide (rGO) network with a porous poly(dimethylsiloxane) (p‐PDMS) elastomer (pPCG). This reciprocal architecture not only alleviates the aggregation of carbon nanofillers but also significantly improves the conductivity of pPCG under large strains. Consequently, the pPCG exhibits high electrical conductivity with a low nanofiller loading (27 S m−1 with 2 wt% CNTs/graphene) and a notable retention capability after bending and stretching. The simulation of the mechanical properties of the p‐PDMS model demonstrates that an extremely large applied strain (εappl) can be accommodated through local rotations and bending of cell walls. Thus, after a slight decrease, the conductivity of pPCG can continue to remain constant even as the strain increases to 50%. In general, this architecture of pPCG with a combination of a porous polymer substrate and 3D carbon nanofiller network possesses considerable potential for numerous applications in next‐generation stretchable electronics. A highly stretchable conductor is manufactured by integrating porous poly(dimethylsiloxane) (p‐PDMS) with a CNT/graphene network (pPCG). Mechanical simulation of p‐PDMS demonstrates that large strains are accommodated through strut rotations and bending. After a slight decrease, the high conductivity (27 S m−1 with 2 wt% CNTs/graphene) remained constant, even as the strain was increased to 50%.
      PubDate: 2014-10-01T11:40:45.705075-05:
      DOI: 10.1002/adfm.201401886
       
  • Electrophosphorescence: 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 (Adv. Funct.
           Mater. 47/2014)
    • Authors: Guomeng Li; Dongxia Zhu, Tai Peng, Yu Liu, Yue Wang, Martin R. Bryce
      Pages: 7560 - 7560
      Abstract: An all‐phosphor host‐guest doping system is presented by Y. Liu, Y. Wang, M. R. Bryce, and colleagues on page 7420. It is based on two novel Ir complexes possessing bipolar transporting ability and realizes ultra‐high efficiency orange‐red phosphorescent organic light‐emitting devices, which exhibit constant peak power efficiency of >75 lm W−1 and external quantum efficiency of >26% as well as extremely low efficiency roll‐off within a certain range of 8 and 15 wt%.
      PubDate: 2014-12-12T01:14:22.901667-05:
      DOI: 10.1002/adfm.201470307
       
 
 
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