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CHEMISTRY (553 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: 17)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 25)
ACS Nano     Full-text available via subscription   (Followers: 289)
ACS Photonics     Full-text available via subscription   (Followers: 5)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 8)
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: 35)
Advances in Chemical Engineering and Science     Open Access   (Followers: 23)
Advances in Chemical Science     Open Access   (Followers: 9)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 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: 180)
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: 3)
Analyst     Full-text available via subscription   (Followers: 35)
Angewandte Chemie     Hybrid Journal   (Followers: 17)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 232)
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: 222)
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: 10)
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
   [37 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]
  • Few‐Layered SnS2 on Few‐Layered Reduced Graphene Oxide as
           Na‐Ion Battery Anode with Ultralong Cycle Life and Superior Rate
    • 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
    • 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
    • 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
    • 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
  • Masthead: (Adv. Funct. Mater. 44/2014)
    • Pages: n/a - n/a
      PubDate: 2014-11-20T08:27:58.222506-05:
      DOI: 10.1002/adfm.201470289
  • 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
    • 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
    • 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
    • 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
  • Surface Directed Phase Separation of Semiconductor Ferroelectric Polymer
           Blends and their use in Non‐Volatile Memories
    • Authors: Albert van Breemen; Tomasz Zaba, Vsevolod Khikhlovskyi, Jasper Michels, Rene Janssen, Martijn Kemerink, Gerwin Gelinck
      Pages: n/a - n/a
      Abstract: The polymer phase separation of P(VDF‐TrFE):F8BT blends is studied in detail. Its morphology is key to the operation and performance of memory diodes. In this study, it is demonstrated that it is possible to direct the semiconducting domains of a phase‐separating mixture of P(VDF‐TrFE) and F8BT in a thin film into a highly ordered 2D lattice by means of surface directed phase separation. Numerical simulation of the surface‐controlled de‐mixing process provides insight in the ability of the substrate pattern to direct the phase separation, and hence the regularity of the domain pattern in the final dry blend layer. By optimizing the ratio of the blend components, the number of electrically active semiconductor domains is maximized. Pattern replication on a cm‐scale is achieved, and improved functional device performance is demonstrated in the form of a 10‐fold increase of the ON‐current and a sixfold increase in current modulation. This approach therefore provides a simple and scalable means to higher density integration, the ultimate target being a single semiconducting domain per memory cell. 3D morphology control in polymer resistive memories by surface directed phase separation of semiconductor ferroelectric blends is presented. Full 3D numerical simulation of the surface‐controlled de‐mixing process provides insight in the ability of the substrate pattern to direct the phase separation. Pattern replication on a cm‐scale is achieved leading to enhanced functional device performance.
      PubDate: 2014-10-29T12:44:41.382176-05:
      DOI: 10.1002/adfm.201401896
  • Comparison of Two D−A Type Polymers with Each Being Fluorinated
           on D and A Unit for High Performance Solar Cells
    • Authors: Jea Woong Jo; Seunghwan Bae, Feng Liu, Thomas P. Russell, Won Ho Jo
      Pages: n/a - n/a
      Abstract: For the purpose of investigating the effect of fluorination position on D−A type conjugated polymer on photophysical and photovoltaic properties, two types of fluorinated polymere are synthesized, HF with fluorination on electron‐donating unit and FH with fluorination on electron‐accepting unit. Compared to non‐fluorinated polymer, fluorinated polymers exhibit deeper HOMO energy levels without change of bandgap and stronger vibronic shoulder in UV−visible absorption, indicating that fluorination enhances intermolecular interaction. HF with fluorinated D unit exhibits well‐developed fibril network, low bimolecular recombination and high hole mobility, which lead a high PCE of 7.10% in conventional single‐junction solar cells, which is higher than the PCE (6.41%) of FH with fluorinated A unit. Therefore, this result demonstrates that fluorination on electron‐donating unit in D−A polymers could be a promising strategy for achieving high performance polymer solar cells. Two types of fluorinated D−A polymers with each being fluorinated on D and A unit are designed and synthesized. The D−A polymer with fluorinated D unit exhibits well‐developed fibril network, low bimolecular recombination and high hole mobility, leading to a high PCE of 7.10%, which is higher than the PCE (6.41%) of the polymer with fluorinated A unit.
      PubDate: 2014-10-27T16:23:01.125744-05:
      DOI: 10.1002/adfm.201402210
  • Graphene‐Directed Supramolecular Assembly of Multifunctional Polymer
           Hydrogel Membranes
    • Authors: Yufei Wang; Sheng Chen, Ling Qiu, Kun Wang, Huanting Wang, George P. Simon, Dan Li
      Pages: n/a - n/a
      Abstract: Polymer‐based nanoporous hydrogel membranes hold great potential for a range of applications including molecular filtration/separation, controlled drug release, and as sensors and actuators. However, to be of practical utility, polymer membranes generally need to be fabricated as ultrathin yet mechanically robust, have a large‐area yet be defect‐free and in some cases, their structure needs the capability to adapt to certain stimuli. These stringent and sometimes self‐conflicting requirements make it very challenging to manufacture such bulk nanostructures in a controllable, scalable and cost‐effective manner. Here, a versatile approach to the fabrication of multifunctional polymer‐based hydrogel membranes is demonstrated by a single step involving filtration of an aqueous dispersion containing chemically converted graphene (CCG) and a polymer. With CCG uniquely serving as a membrane‐ and pore‐forming directing agent and as a physical cross‐linker, a range of water soluble polymers can be readily processed into nanoporous hydrogel membranes through supramolecular interactions. With the interconnected CCG network as a robust and porous scaffold, the membrane nanostructure can easily be fine‐tuned to suit different applications simply by controlling the chemistry and concentration of the incorporated polymer. This work provides a simple and versatile platform for the design and fabrication of new adaptive supramolecular membranes for a variety of applications. A versatile approach to the fabrication of multifunctional polymer hydrogel membranes is demonstrated by exploiting the unique micro‐corrugated 2D configuration of chemically converted graphene, its self‐assembly behavior and rich supramolecular interactions. A range of water soluble polymers can be readily processed into such membranes with tunable nanostructures to suit a variety of potential applications.
      PubDate: 2014-10-27T05:39:18.300738-05:
      DOI: 10.1002/adfm.201402952
  • Highly Thermal Stable and Efficient Organic Photovoltaic Cells with
           Crosslinked Networks Appending Open‐Cage Fullerenes as Additives
    • Authors: Chih‐Ping Chen; Chien‐Yu Huang, Shih‐Ching Chuang
      Pages: n/a - n/a
      Abstract: Highly thermal stable organic bulk heterojunction (OBHJ) photovoltaic cells are demonstrated with crosslinkable open‐cage fullerenes (COF) as additives in the active layer. Partial incorporation of COF, ≈10–15 wt% with weight ratio of P3HT:PC61BM = 1:0.9, builds up three‐dimensional local borders upon heating treatment at 150 °C for 10 min. This process induces crosslinking chemical reaction through activating the styryl moiety in COF and reduces phase aggregation rates of fullerenes materials. Supported by statistics of devices degradation data analysis and optical microscopy study, the devices with COF show longer lifetime with keeping their efficiency (t = 144 h) under accelerated heating test at 150 °C, while PCE of normal devices without COF drop dramatically. These results demonstrate that the thermally crosslinkable COF is an excellent additive for highly thermal stable and durable OPVs applications. Highly thermal stable and durable organic bulk heterojunction photovoltaic cells are demonstrated with the incorporation of ≈10–15 wt% crosslinkable open‐cage fullerenes (COF) as additives in the active layer (weight ratio of P3HT:PC61BM = 1:0.9), through building up three‐dimensional local borders upon thermal treatment at 150 °C.
      PubDate: 2014-10-27T05:39:06.120973-05:
      DOI: 10.1002/adfm.201401735
  • Ultrasmall Sn Nanoparticles Embedded in Carbon as High‐Performance
           Anode for Sodium‐Ion Batteries
    • Authors: Yongchang Liu; Ning Zhang, Lifang Jiao, Zhanliang Tao, Jun Chen
      Pages: n/a - n/a
      Abstract: Designed as a high‐capacity, high‐rate, and long‐cycle life anode for sodium‐ion batteries, ultrasmall Sn nanoparticles (≈8 nm) homogeneously embedded in spherical carbon network (denoted as 8‐Sn@C) is prepared using an aerosol spray pyrolysis method. Instrumental analyses show that 8‐Sn@C nanocomposite with 46 wt% Sn and a BET surface area of 150.43 m2 g−1 delivers an initial reversible capacity of ≈493.6 mA h g−1 at the current density of 200 mA g−1, a high‐rate capacity of 349 mA h g−1 even at 4000 mA g−1, and a stable capacity of ≈415 mA h g−1 after 500 cycles at 1000 mA g−1. The remarkable electrochemical performance of 8‐Sn@C is owing to the synergetic effects between the well‐dispersed ultrasmall Sn nanoparticles and the conductive carbon network. This unique structure of very‐fine Sn nanoparticles embedded in the porous carbon network can effectively suppress the volume fluctuation and particle aggregation of tin during prolonged sodiation/desodiation process, thus solving the major problems of pulverization, loss of electrical contact and low utilization rate facing Sn anode. Sn@C composite with ultrasmall Sn nano­particles (≈8 nm) homogeneously embedded in spherical carbon network is prepared by aerosol spray pyrolysis and further evaluated as anode material for rechargeable Na‐ion batteries. The nanocomposite exhibits excellent electrochemical performance with high reversible capacity, high‐rate capability, and long cycling stability.
      PubDate: 2014-10-27T05:39:02.530134-05:
      DOI: 10.1002/adfm.201402943
  • The Effect of Large Compositional Inhomogeneities on the Performance of
           Organic Solar Cells: A Numerical Study
    • Authors: Davide Bartesaghi; L. Jan Anton Koster
      Pages: n/a - n/a
      Abstract: The power conversion efficiency of solar cells based on a conjugated polymer (donor) and a fullerene derivative (acceptor) is very sensitive to the morphology of the active layer. One detrimental feature, which is often encountered in non‐optimal morphologies, is the occurrence of fullerene blobs in a finely mixed matrix containing both donor and acceptor material. Here, the effects of such fullerene blobs are studied in detail with a three‐dimensional drift‐diffusion model. It includes the effects of exciton diffusion and quenching; space‐charge; recombination, generation, drift and diffusion of charge carriers; and the injection/extraction of carriers at the contacts. The influence of blob size and shape, and matrix composition are quantified. The latter has the strongest effect on the overall efficiency, as most of the current is transported through the mixed phase. The total current flowing out of the solar cell can be split up in a part which comes from the interfacial region between the acceptor phase and the mixed phase, and a part that stems from the mixed phase itself. Depending on the bias voltage and the morphology, one or the other contribution is dominant. Finally, it is shown how both contributions can be computed with a simple one‐dimensional drift–diffusion simulator. A three‐dimensional model is presented to relate the efficiency of bulk heterojunction solar cells to the morphology of the active layer. With this, the effect of the occurrence of large acceptor domains dispersed in a mixed phase is quantified. The total current is split up in two contributions, both of which are calculated also with a one‐dimensional drift–diffusion model.
      PubDate: 2014-10-27T05:38:33.886352-05:
      DOI: 10.1002/adfm.201402260
  • Dipole‐field Sums, Lorentz Factors, and Dielectric Properties of
           Organic Molecular Films Modeled as Crystalline Arrays of Polarizable
    • Authors: Davide Vanzo; Benjamin J. Topham, Zoltán G. Soos
      Pages: n/a - n/a
      Abstract: The relative permittivity κ = ε/ε0 of thin films used in organic electronic devices is directly related to the structure and the molecular polarizability α when intermolecular overlap is small. Monolayer and multilayer films are modeled as lattices of polarizable points with induced dipoles μ = αF where the internal electric field F includes contributions from all induced dipoles. The polarization per unit volume is P = nμ for number density n. Dipole‐field sums are evaluated directly for atomic and molecular crystals and films through stacking of infinite layers. Lorentz factors in uniformly polarized crystals of less than cubic symmetry resolve completely the conditional convergence of dipole‐field sums in three dimensions. Thin films have equal P within layers but not at or near the surface. Surface effects are shown to increase with αn and sometimes to extend into films even though dipole fields are mainly due to adjacent layers. Simple and body‐centered tetragonal lattices illustrate polarizing or depolarizing interactions between layers that mimic molecules or oligomers tilted at angle Φ from normal to the surface in films or SAMs. Uniform P in molecular films refers to unit cells rather than to atoms and there are multiple ways to partition anisotropic molecular α among polarizable points. An illustrative analytical model based on polarizable points and dipole fields of adjacent layers is applied to oligophenyl films and to conjugated molecules in acene films. The relative permittivity κ = ε/ε0 of crystalline thin films is obtained in the limit of zero intermolecular overlap. Dipole‐field sums over polarizable points in applied field E are evaluated directly and combined with Lorentz factors to compute κ from monolayers to crystals, deviations from uniform polarization in surface layers, and dielectric properties in systems of lower than cubic symmetry.
      PubDate: 2014-10-22T12:11:03.916828-05:
      DOI: 10.1002/adfm.201402405
  • An Exciplex Forming Host for Highly Efficient Blue Organic Light Emitting
           Diodes with Low Driving Voltage
    • Authors: Jeong‐Hwan Lee; Shuo‐Hsien Cheng, Seung‐Jun Yoo, Hyun Shin, Jung‐Hung Chang, Chih‐I Wu, Ken‐Tsung Wong, Jang‐Joo Kim
      Pages: n/a - n/a
      Abstract: The exciplex forming co‐host with phosphorescent dopant system has potential to realize highly efficient phosphorescent organic light emitting didoes (PhOLEDs). However, the exciplex forming co‐host for blue phosphorescent OLEDs has been rarely introduced because of higher triplet level of the blue dopant than green and red dopants. In this work, a novel exciplex forming co‐host with high triplet energy level is developed by mixing a phosphine oxide based electron transporting material, PO‐T2T, and a hole transporting material, N,N′‐dicarbazolyl‐3,5‐benzene (mCP). Photo‐physical analysis shows that the exciplexes are formed efficiently in the host and the energy transfer from the exciplex to blue phosphorescent dopant (iridium(III)bis[(4,6‐difluorophenyl)‐pyridinato‐N,C2′]picolinate; FIrpic) is also efficient, enabling the triplet harvest without energy loss. As a result, an unprecedented high performance blue PhOLED with the exciplex forming co‐host is demonstrated, showing a maximum external quantum efficiency (EQE) of 30.3%, a maximum power efficiency of 66 lm W−1, and low driving voltage of 2.75 at 100 cd m−2, 3.29 V at 1000 cd m−2, and 4.65 V at 10 000 cd m−2, respectively. The importance of the exciton confinement in the exciplex forming co‐host is further investigated which is directly related to the performance of PhOLEDs. A novel exciplex forming host, composed of mCP and PO‐T2T, is realized. Using the host and efficient energy transfer to FIrpic, unprecedented high performance blue phosphorescent OLED is demonstrated, showing a maximum EQE of 30.3%, power efficiency of 66 lm W−1, and extremely low operating voltages of 2.75 at 100 cd m−2, and 4.65 V at 10 000 cd m−2.
      PubDate: 2014-10-22T12:10:11.933815-05:
      DOI: 10.1002/adfm.201402707
  • Nanoconfined LiBH4 as a Fast Lithium Ion Conductor
    • Authors: Didier Blanchard; Angeloclaudio Nale, Dadi Sveinbjörnsson, Tamara M. Eggenhuisen, Margriet H. W. Verkuijlen, Suwarno, Tejs Vegge, Arno P. M. Kentgens, Petra E. de Jongh
      Pages: n/a - n/a
      Abstract: Designing new functional materials is crucial for the development of efficient energy storage and conversion devices such as all solid‐state batteries. LiBH4 is a promising solid electrolyte for Li‐ion batteries. It displays high lithium mobility, although only above 110 °C at which a transition to a high temperature hexagonal structure occurs. Herein, it is shown that confining LiBH4 in the pores of ordered mesoporous silica scaffolds leads to high Li+ conductivity (0.1 mS cm−1) at room temperature. This is a surprisingly high value, especially given that the nanocomposites comprise 42 vol% of SiO2. Solid state 7Li NMR confirmed that the high conductivity can be attributed to a very high Li+ mobility in the solid phase at room temperature. Confinement of LiBH4 in the pores leads also to a lower solid‐solid phase transition temperature than for bulk LiBH4. However, the high ionic mobility is associated with a fraction of the confined borohydride that shows no phase transition, and most likely located close to the interface with the SiO2 pore walls. These results point to a new strategy to design low‐temperature ion conducting solids for application in all solid‐state lithium ion batteries, which could enable safe use of Li‐metal anodes. Confining LiBH 4 inside nanopores of mesoporous silica results in stable and high Li+ mobilities persisting to room temperature. The mobility is associated with a LiBH4 phase that does not undergo a structural phase transition, a phase probably located within 1.0 nanometer of the pore walls. This presents a new strategy to design efficient electrolytes for all solid‐state rechargeable lithium batteries.
      PubDate: 2014-10-22T04:54:11.288869-05:
      DOI: 10.1002/adfm.201402538
  • A Complete Separation of Hexane Isomers by a Functionalized Flexible Metal
           Organic Framework
    • Authors: Patricia A. P. Mendes; Patricia Horcajada, Sébastien Rives, Hong Ren, Alírio E. Rodrigues, Thomas Devic, Emmanuel Magnier, Philippe Trens, Hervé Jobic, Jacques Ollivier, Guillaume Maurin, Christian Serre, José A. C. Silva
      Pages: n/a - n/a
      Abstract: The separation ability of branched alkane isomers (nHEX, 3MP, 22DMB) of the flexible and functionalized microporous iron(III) dicarboxylate MIL‐53(Fe)‐(CF3)2 solid is evaluated through a combination of breakthrough experiments (binary or ternary mixtures), adsorption isotherms, X‐ray diffraction temperature analysis, quasi‐elastic neutron scattering measurements and molecular dynamics simulations. A kinetically controlled molecular sieve separation between the di‐branched isomer of hexane 22DMB from a mixture of paraffins is achieved. The reported total separation between mono‐ and di‐branched alkanes which was neither predicted nor observed so far in any class of porous solids is spectacular and paves the way towards a potential unprecedented upgrading of the RON of gasoline. A kinetically controlled molecular sieve separation between the 2,2‐Dimethyl‐Butane (22DMB) branched alkane isomer from a mixture of paraffins was achieved for the first time using the flexible and functionalized MIL‐53(Fe)‐(CF3)2 metal‐organic‐framework.
      PubDate: 2014-10-21T14:33:21.088049-05:
      DOI: 10.1002/adfm.201401974
  • Molecular‐Level Switching of Polymer/Nanocrystal Non‐Covalent
           Interactions and Application in Hybrid Solar Cells
    • Authors: Carlo Giansante; Rosanna Mastria, Giovanni Lerario, Luca Moretti, Ilka Kriegel, Francesco Scotognella, Guglielmo Lanzani, Sonia Carallo, Marco Esposito, Mariano Biasiucci, Aurora Rizzo, Giuseppe Gigli
      Pages: n/a - n/a
      Abstract: Hybrid composites obtained upon blending conjugated polymers and colloidal semiconductor nanocrystals are regarded as attractive photo­active materials for optoelectronic applications. Here it is demonstrated that tailoring nanocrystal surface chemistry permits to control non‐covalent and electronic interactions between organic and inorganic components. The pending moieties of organic ligands at the nanocrystal surface are shown to not merely confer colloidal stability while hindering charge separation and transport, but drastically impact morphology of hybrid composites during formation from blend solutions. The relevance of this approach to photovoltaic applications is demonstrated for composites based on poly(3‐hexylthiophene) and lead sulfide nanocrystals, considered as inadequate until this report, which enable the fabrication of hybrid solar cells displaying a power conversion efficiency that reaches 3%. By investigating (quasi)steady‐state and time‐resolved photo‐induced processes in the nanocomposites and their constituents, it is ascertained that electron transfer occurs at the hybrid interface yielding long‐lived separated charge carriers, whereas interfacial hole transfer appears hindered. Here a reliable alternative aiming to gain control over macroscopic optoelectronic properties of polymer/nanocrystal composites by mediating their non‐covalent interactions via ligands' pending moieties is provided, thus opening new possibilities towards efficient solution‐processed hybrid solar cells. Hybrid nanocomposites with switched morphology are obtained by mediating non‐covalent interactions between conjugated polymers and semiconductor nanocrystals via the pending moiety of organic ligands at the nanocrystal surface. Morphology switching deeply impacts the optoelectronic properties of polythiophene/PbS nanocrystal composites, as demonstrated by achieving unprecedented photovoltaic device performances for this blend material. Photo‐induced processes at the hybrid interface are investigated and discussed.
      PubDate: 2014-10-21T14:33:08.937597-05:
      DOI: 10.1002/adfm.201401841
  • Enhanced Optical Property with Tunable Band Gap of Cross‐linked
           PEDOT Copolymers via Oxidative Chemical Vapor Deposition
    • Authors: Sunghwan Lee; Karen K. Gleason
      Pages: n/a - n/a
      Abstract: Highoptical transmittance conjugated‐polymers with electrical conductivity are garnering much attention for the applications in organic optoelectronic devices including organic field‐effect‐transistors and solar cells. Polymers based on PEDOT are particularly promising candidates with high conductivity, uniform surface planarity and excellent ductility. In this work, homopolymer PEDOT deposited using oxidative chemical‐vapor‐deposition(oCVD) show the maximum conductivity of ≈3500 S/cm. However, their utility is limited due to the relatively low transmittance and abrupt decrease near the red edge in the visible regime. Here, the significantly improved optical properties achieved via tuning the bandgap of cross‐linked PEDOT copolymers using oCVD, offering a single‐step process for the synthesis and deposition of copolymer films, is reported. The cross‐linking monomers of biphenyl or anthracene are simultaneously evaporated with EDOT monomer and an oxidant(FeCl3) during the deposition. Poly(anthracene‐co‐EDOT)[p(ANTH‐co‐EDOT)] shows the superior transmittance (≈93%) to homopolymer PEDOT (≈80%) and poly(biphenyl‐co‐EDOT)[p(BPH‐co‐EDOT)] (≈88%). Additionally, copolymers show no transmission decay in the red edge regime unlike homopolymer PEDOT that presents an abrupt transmission falloff. An improvement in optical transmittance is in agreement with an increase in bandgap of materials (p(ANTH‐co‐EDOT), ≈2.3eV vs PEDOT, ≈1.8 eV). oCVD‐processed bandgap‐tunable PEDOT copolymers with enhanced transmittance may, therefore, have applications in organic optoelectronic devices that require high optical transparency. Band gap‐tuned PEDOT copolymers are successfully demonstrated using oCVD with the incorporation of cross‐linking monomers of anthracene or biphenyl. oCVD offers single‐step synthesis, deposition and doping of copolymers. oCVD copolymers show significantly improved visible‐regime transparency compared to homopolymer PEDOT, which is promising for many organic optoelectronic devices that require high optical transmittance with electrical conductivity.
      PubDate: 2014-10-20T10:44:56.928614-05:
      DOI: 10.1002/adfm.201402924
  • Blood Ties: Co3O4 Decorated Blood Derived Carbon as a Superior
           Bifunctional Electrocatalyst
    • Authors: Chao Zhang; Markus Antonietti, Tim‐Patrick Fellinger
      Pages: n/a - n/a
      Abstract: A simple, versatile and cheap synthetic route is demonstrated for the preparation of Co3O4 decorated blood powder derived heteroatom doped porous carbon (BDHC). The inorganic hybrid performs well as an advanced bifunctional non‐precious metal electrocatalyst. The hybridization of Co3O4 with the blood‐derived carbon results in improved activities not only towards the oxygen reduction reaction (ORR), but also in the reverse oxygen evolution reaction (OER). An improved ORR activity and a tuned four electron transfer selectivity can be assigned to a synergistic catalytic effect due the intimate contact between Co3O­4 particles and the highly conductive heteroatom doped carbon support, mediated by cobalt‐nitrogen or cobalt‐phosphorous coordination sites. This heterojunction may facilitate the electron transfer by preventing an accumulation of electron density within the Co3O­4 particles. The straight‐forward and cheap synthesis of the highly active and durable electrocatalyst make it a promising candidate for a next‐generation bifunctional electrocatalyst for applications such as reversible fuel cells/electrolyzers or metal air batteries. A simple, versatile and cheap synthetic route is developed for the preparation of Co3O4 decorated blood powder derived foam‐like heteroatom doped porous carbon (BDHC). The hybrid performs well as an advanced bifunctional non‐precious metal electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the alkaline medium.
      PubDate: 2014-10-18T05:20:17.650469-05:
      DOI: 10.1002/adfm.201402770
  • Multi‐Site Functionalization of Protein Scaffolds for Bimetallic
           Nanoparticle Templating
    • Authors: Kelly N. L. Huggins; Alia P. Schoen, Manickam Adhimoolam Arunagirinathan, Sarah C. Heilshorn
      Pages: n/a - n/a
      Abstract: The use of biological scaffolds to template inorganic material offers a strategy to synthesize precise composite nanostructures of different sizes and shapes. Proteins are unique biological scaffolds that consist of multiple binding regions or epitope sites that site‐specifically associate with conserved amino acid sequences within protein‐binding partners. These binding regions can be exploited as synthesis sites for multiple inorganic species within the same protein scaffold, resulting in bimetallic inorganic nanostructures. This strategy is demonstrated with the scaffold protein clathrin, which self‐assembles into spherical cages. Specifically, tether peptides that noncovalently associate with distinct clathrin epitope sites, while initiating simultaneous synthesis of two inorganic species within the assembled clathrin protein cage, are designed. The flexibility and diversity of this unique biotemplating strategy is demonstrated by synthesizing two types of composite structures (silver–gold mixed bimetallic and silver–gold core–shell nanostructures) from a single clathrin template. This noncovalent, Template Engineering Through Epitope Recognition, or TEThER, strategy can be readily applied to any protein system with known epitope sites to template a variety of bimetallic structures without the need for chemical or genetic mutations. A unique noncovalent biotemplating method is used to localize multiple inorganic species at specific nucleation sites on a single clathrin protein template. The data illustrate that this templating strategy facilitates the synthesis of two types of composite nanostructures based on the location of the nucleation sites: silver–gold mixed bimetallic and silver–gold core–shell nanostructures.
      PubDate: 2014-10-18T04:59:05.730423-05:
      DOI: 10.1002/adfm.201402049
  • Materials Meets Concepts in Molecule‐based Electronics
    • Authors: Frank Ortmann; K. Sebastian Radke, Alrun Günther, Daniel Kasemann, Karl Leo, Gianaurelio Cuniberti
      Pages: n/a - n/a
      Abstract: In this contribution, molecular materials are highlighted as an important topic in the diverse field of condensed matter physics, with focus on their particular electronic and transport properties. A better understanding of their performance in various applications and devices demands for an extension of basic theoretical approaches to describe charge transport in molecular materials, including the accurate description of electron–phonon coupling. Starting with the simplest case of a molecular junction and moving on to larger aggregates of bulk organic semiconductors, charge‐transport regimes from ballistic motion to incoherent hopping, which are frequently encountered in molecular systems under respective conditions, are discussed. Transport features of specific materials are described through ab initio material parameters whose determination is addressed. Molecular semiconductors are intriguing materials with applications in flexible electronics due to their potential low‐cost processing ability and chemical tunability. In addition, they are utile in fundamental studies of decoherence effects in single‐molecular junctions. Concepts of transport modeling for such systems are presented in this Feature Article, highlighting the unique transport properties of organic and molecular semiconductors.
      PubDate: 2014-10-14T11:32:31.870027-05:
      DOI: 10.1002/adfm.201402334
  • Effects of Delocalized Charge Carriers in Organic Solar Cells: Predicting
           Nanoscale Device Performance from Morphology
    • Authors: Adam G. Gagorik; Jacob W. Mohin, Tomasz Kowalewski, Geoffrey R. Hutchison
      Pages: n/a - n/a
      Abstract: Monte Carlo simulations of charge transport in organic solar cells are performed for ideal and isotropic bulk heterojunction morphologies while altering the delocalization length of charge carriers. Previous device simulations have either treated carriers as point charges or with a highly delocalized mean‐field treatment. This new model of charge delocalization leads to weakening of Coulomb interactions and more realistic predicted current and fill factors at moderate delocalization, relative to point charges. It is found that charge delocalization leads to significantly increased likelihood of escaping interface traps. In isotopic two‐phase morphologies, increasing the domain sizes leads to slight decreases in predicted device efficiencies. It was previously shown that tortuous pathways in systems with small domain sizes can decrease device performance in thin film systems. However, the diminishing effects of Coulomb interactions with delocalization and efficient separations of excitons by small domains make morphological effects less pronounced. The importance of delocalization, which has largely been ignored in past simulations, as a parameter to consider and optimize when choosing materials for organic solar cells is emphasized. The effects of charge delocalization on device efficiency is probed using mesoscale Monte Carlo simulations of charge transport in idealized and isotropic two‐phase morphologies. Interfacial charge trapping is drastically reduced when Coulomb interactions are weakened through moderate delocalization (1.0–2.0 nm). Morphological differences become less dominant as charges delocalize.
      PubDate: 2014-10-14T11:32:19.097764-05:
      DOI: 10.1002/adfm.201402332
  • Temperature‐Dependent Electrical Transport in Polymer‐Sorted
           Semiconducting Carbon Nanotube Networks
    • Authors: Jia Gao; Yueh‐Lin (Lynn) Loo
      Pages: n/a - n/a
      Abstract: The temperature dependence of the electrical characteristics of field‐effect transistors (FETs) based on polymer‐sorted, large‐diameter semiconducting carbon nanotube networks is investigated. The temperature dependences of both the carrier mobility and the source‐drain current in the range of 78 K to 293 K indicate thermally activated, but non‐Arrhenius, charge transport. The hysteresis in the transfer characteristics of FETs shows a simultaneous reduction with decreasing temperature. The hysteresis appears to stem from screening of charges that are transferred from the carbon nanotubes to traps at the surface of the gate dielectric. The temperature dependence of sheet resistance of the carbon nanotube networks, extracted from FET characteristics at constant carrier concentration, specifies fluctuation‐induced tunneling as the mechanism responsible for charge transport, with an activation energy that is dependent on film thickness. Our study indicates inter‐tube tunneling to be the bottleneck and implicates the role of the polymer coating in influencing charge transport in polymer‐sorted carbon nanotube networks. The temperature‐dependent electrical transport in polymer‐sorted semiconducting carbon nanotube networks is elucidated in this work. The source‐drain current and mobility in polymer‐sorted carbon nanotube network‐based field‐effect transistors decrease with decreasing temperature attributable to fluctuation‐induced tunneling. The barrier for charge transport inversely correlates with carbon nanotube network thickness, for the probability to sample conductive pathways with fewer inter‐tube junctions increases with increasing thickness.
      PubDate: 2014-10-14T11:31:33.854493-05:
      DOI: 10.1002/adfm.201402407
  • 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, Yong‐Min Kim, Albina Y. Borisevich, Ian MacLaren, Quentin M. Ramasse, Mark G. Blamire, Quanxi Jia, Judith L. MacManus‐Driscoll
      Pages: n/a - n/a
      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
  • From Chiral Islands to Smectic Layers: A Computational Journey Across
           Sexithiophene Morphologies on C60
    • Authors: Gabriele D'Avino; Luca Muccioli, Claudio Zannoni
      Pages: n/a - n/a
      Abstract: A theoretical investigation of the molecular organization at a sexithiophene (T6)‐C60 fullerene planar heterojunction, based on atomistic molecular dynamics, is presented, in which the effect of two different sample preparation processes on the resulting interface morphology is explored. First, the landing of T6 on C60(001) substrate is considered, which leads to crystalline layers of standing and tilted molecules, in accordance with experiments. The observation and the quantitative characterization of the nucleation and growth provide detailed insights on this out‐of‐equilibrium process, including the establishment of an epitaxial relationship between the substrate and the interfacial T6 layer, and the spontaneous formation of defective islands, characterized by chiral edges, during the growth of the second and third layers. It is then shown that molecular orientations can be radically changed upon annealing at 600 K, at which T6 forms a smectic phase with planar alignment, whose layers are perpendicular to the interface. The interfacial T6 morphologies are then analyzed in detail at room temperature and compared to the known bulk polymorphs. The morphology of sexithiophene thin films deposited over a C60 fullerene crystalline slab is investigated with an atomistic molecular dynamics technique. Simulations show that the nucleation and growth of vapor‐deposited sexithiophene leads to the formation of weakly correlated crystalline layers of standing molecules, while the orientation of sexithiophene molecules can be radically changed to planar upon thermal annealing.
      PubDate: 2014-10-14T11:30:58.115475-05:
      DOI: 10.1002/adfm.201402609
  • Strategy for Enhancing the Dielectric Constant of Organic Semiconductors
           Without Sacrificing Charge Carrier Mobility and Solubility
    • Authors: Solmaz Torabi; Fatemeh Jahani, Ineke Van Severen, Catherine Kanimozhi, Satish Patil, Remco W. A. Havenith, Ryan C. Chiechi, Laurence Lutsen, Dirk J. M. Vanderzande, Thomas J. Cleij, Jan C. Hummelen, L. Jan Anton Koster
      Pages: n/a - n/a
      Abstract: Current organic semiconductors for organic photovoltaics (OPV) have relative dielectric constants (relative permittivities, ε r) in the range of 2–4. As a consequence, Coulombically bound electron‐hole pairs (excitons) are produced upon absorption of light, giving rise to limited power conversion efficiencies. We introduce a strategy to enhance ε r of well‐known donors and acceptors without breaking conjugation, degrading charge carrier mobility or altering the transport gap. The ability of ethylene glycol (EG) repeating units to rapidly reorient their dipoles with the charge redistributions in the environment was proven via density functional theory (DFT) calculations. Fullerene derivatives functionalized with triethylene glycol side chains were studied for the enhancement of ε r together with poly(p‐phenylene vinylene) and diketopyrrolopyrrole based polymers functionalized with similar side chains. The polymers showed a doubling of ε r with respect to their reference polymers in identical backbone. Fullerene derivatives presented enhancements up to 6 compared with phenyl‐C61‐butyric acid methyl ester (PCBM) as the reference. Importantly, the applied modifications did not affect the mobility of electrons and holes and provided excellent solubility in common organic solvents. A synthetic strategy is presented for the dielectric constant enhancement of organic semiconductors. It is demonstrated that fullerene derivatives, DPP‐ and PPV‐based polymers show a marked increase of the relative dielectric constant when being functionalized with TEG side chains. Density functional theory calculations attribute such enhancements to the rapid reorientations of ethylene glycol ­dipoles on the side chains.
      PubDate: 2014-10-14T11:30:36.51344-05:0
      DOI: 10.1002/adfm.201402244
  • Plasmonic Janus‐Composite Photocatalyst Comprising Au and
           C–TiO2 for Enhanced Aerobic Oxidation over a Broad
           Visible‐Light Range
    • Authors: Lequan Liu; Thang Duy Dao, Rajesh Kodiyath, Qing Kang, Hideki Abe, Tadaaki Nagao, Jinhua Ye
      Pages: n/a - n/a
      Abstract: Asymmetric Janus nanostructures containing a gold nanocage (NC) and a carbon–titania hybrid nanocrystal (AuNC/(C–TiO2)) are prepared using a novel and facile microemulsion‐based approach that involves the assistance of ethanol. The localized surface plasmon resonance of the Au NC with a hollow interior and porous walls induce broadband visible‐light harvesting in the Janus AuNC/(C–TiO2). An acetone evolution rate of 6.3 μmol h−1 g−1 is obtained when the Janus nanostructure is used for the photocatalytic aerobic oxidation of iso‐propanol under visible light (λ = 480–910 nm); the rate is 3.2 times the value of that obtained with C–TiO2, and in photo‐electrochemical investigations an approximately fivefold enhancement is obtained. Moreover, when compared with the core–shell structure (AuNC@(C–TiO2) and a gold–carbon–titania system where Au sphere nanoparticles act as light‐harvesting antenna, Janus AuNC/(C–TiO2) exhibit superior plasmonic enhancement. Electromagnetic field simulation and electron paramagnetic resonance results suggest that the plasmon–photon coupling effect is dramatically amplified at the interface between the Au NC and C–TiO2, leading to enhanced generation of energetic hot electrons for photocatalysis. A novel and facile approach is developed for preparing asymmetric Janus nanostructures comprising a gold nanocage and carbon–titania hybrid nanoparticles. The microemulsion‐based preparation, results in composites with increased plasmon–photon coupling at the interface of the AuNC and C–TiO2 particle. The amplification of the plasmon–photon coupling leads to enhanced generation of energetic hot electrons for visible‐light photocatalysis.
      PubDate: 2014-10-14T11:28:39.121274-05:
      DOI: 10.1002/adfm.201402088
  • DNA Mutation: Ultrasensitive Detection of Mitochondrial DNA Mutation by
           Graphene Oxide/DNA Hydrogel Electrode (Adv. Funct. Mater. 44/2014)
    • Authors: Liping Sun; Nan Hu, Jian Peng, Liyu Chen, Jian Weng
      Pages: 6897 - 6897
      Abstract: On page 6905, J. Weng and team prepare a hydrogel electrode with ultrasensitive detection from graphene oxide and fish sperm DNA. The linear range for mitochondrial DNA detection is from 1.0 × 10−9 to 1.0 × 10−20 m with a detection limit of 1.0 × 10−20 m. The result is ascribed to the bionic interface and tuneable conductivity of the hydrogel electrode.
      PubDate: 2014-11-20T08:27:59.952644-05:
      DOI: 10.1002/adfm.201470285
  • Sensors: Flexible Inorganic Piezoelectric Acoustic Nanosensors for
           Biomimetic Artificial Hair Cells (Adv. Funct. Mater. 44/2014)
    • Authors: Hyun Soo Lee; Juyong Chung, Geon‐Tae Hwang, Chang Kyu Jeong, Youngdo Jung, Jun‐Hyuk Kwak, Hanmi Kang, Myunghwan Byun, Wan Doo Kim, Shin Hur, Seung‐Ha Oh, Keon Jae Lee
      Pages: 6898 - 6898
      Abstract: A flexible inorganic piezoelectric acoustic nanosensor is demonstrated using high performance PZT thin films. As reported by S. Hur, S.‐H. Oh, K. J. Lee, and colleagues on page 6914, the acoustic nanosensor can utilize artificial hair cell with transducing electric signals to the sensory nerves.
      PubDate: 2014-11-20T08:27:56.174992-05:
      DOI: 10.1002/adfm.201470286
  • Contents: (Adv. Funct. Mater. 44/2014)
    • Pages: 6899 - 6904
      PubDate: 2014-11-20T08:27:55.627396-05:
      DOI: 10.1002/adfm.201470287
  • Ultrasensitive Detection of Mitochondrial DNA Mutation by Graphene
           Oxide/DNA Hydrogel Electrode
    • Authors: Liping Sun; Nan Hu, Jian Peng, Liyu Chen, Jian Weng
      Pages: 6905 - 6913
      Abstract: Ultrasensitive detection of nucleic acid has attracted considerable attention recently in academic research and clinic diagnostics. Current approaches for DNA analysis involve complicated or expensive processes for labeling and often yield a high detection limit. In this study, a hydrogel electrode prepared from graphene oxide and fish sperm DNA is used for label−free mitochondrial DNA detection by impedimetric approach. The hydrogel has a bionic structure containing rich water and natural biomolecule fish sperm DNA that would benefit the adsorption and hybridization of DNA. Graphene oxide is a semiconductor and its conductivity can be improved by doping negatively charged DNA molecules. The result shows that the conductivity and impedance change of hydrogel electrode could be tuned by its length and component. The linear range for DNA detection by the optimized hydrogel is from 1.0 × 10−9 to 1.0 × 10−20 M with a detection limit of 1.0 × 10−20 M. The result is ascribed to the bionic structure and tunable conductivity of hydrogel electrode. The hydrogel electrode has been used to detect the real DNA samples from patients of ovarian cancer with satisfactory results. A hydrogel electrode with ultrasensitive detection is prepared from graphene oxide and fish sperm DNA, and the linear range for mitochondrial DNA detection is from 1.0 × 10−9 to 1.0 × 10−20m with a detection limit of 1.0 × 10−20m. The result is ascribed to the bionic interface and tuneable conductivity of the hydrogel electrode.
      PubDate: 2014-08-26T12:55:30.795535-05:
      DOI: 10.1002/adfm.201402191
  • Flexible Inorganic Piezoelectric Acoustic Nanosensors for Biomimetic
           Artificial Hair Cells
    • Authors: Hyun Soo Lee; Juyong Chung, Geon‐Tae Hwang, Chang Kyu Jeong, Youngdo Jung, Jun‐Hyuk Kwak, Hanmi Kang, Myunghwan Byun, Wan Doo Kim, Shin Hur, Seung‐Ha Oh, Keon Jae Lee
      Pages: 6914 - 6921
      Abstract: For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic‐based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone‐based membrane (SM) mimics the function of the natural basilar membrane for frequency selectivity, and a flexible iPANS is fabricated on the SM utilizing a laser lift‐off technology to overcome the brittle characteristics of inorganic piezoelectric materials. The vibration amplitude vs piezoelectric sensing signals are theoretically examined based on the experimental conditions by finite element analysis. The SM is successful at separating the audible frequency range of incoming sound, vibrating distinctively according to varying locations of different sound frequencies, thus allowing iPANS to convert tiny vibration displacement of ≈15 nm into an electrical sensing output of ≈55 μV, which is close to the simulation results presented. This conceptual iPANS of flexible inorganic piezoelectric materials sheds light on the new fields of nature‐inspired biomimetic systems using inherently high piezoelectric charge constants. The new concept of a biomimetic artificial hair cell using a flexible inorganic piezoelectric acoustic nanosensor (iPANS) is presented. A highly sensitive flexible piezoelectric sensor that responds to sound‐driven vibrations of a thin silicone membrane is fabricated using a laser lift‐off process. The iPANS shows remarkable capability to sense tiny vibrations caused by an external sound wave.
      PubDate: 2014-09-02T12:53:56.870503-05:
      DOI: 10.1002/adfm.201402270
  • Inhibition of Cancer Cell Migration by Gold Nanorods: Molecular Mechanisms
           and Implications for Cancer Therapy
    • Authors: Teng Zhou; Meifang Yu, Bo Zhang, Liming Wang, Xiaochun Wu, Hejiang Zhou, Yipeng Du, Junfeng Hao, Yaping Tu, Chunying Chen, Taotao Wei
      Pages: 6922 - 6932
      Abstract: Gold nanorods have received much attention because of their distinct physicochemical properties and promising applications in bioimaging, biosensing, drug delivery, photothermal therapy, and optoelectronic devices. However, little is known regarding their effect on tumor metastasis. In the present investigation, serum protein‐coated gold nanorods (AuNRs) at low concentrations is shown to exhibit no apparent effects on the viability and proliferation of three different metastatic cancer cell lines, that is, MDA‐MB‐231 human breast cancer cells, PC3 human prostate cancer cells, and B16F10 mouse melanoma cells, but effectively inhibit their migration and invasion in vitro. Quantitative proteomics and real‐time PCR array analyses indicate that exposure of cells to AuNRs can down‐regulate the expression of diverse energy generation‐related genes, which accounts for their inhibition of mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis. The impairment of OXPHOS and glycolysis results in a distinctive reduction of ATP production and subsequent inhibition of F‐actin cytoskeletal assembly, which is crucial for the migration and invasion of cancer cells. The inhibitory effect of AuNRs on cancer cell migration is also confirmed in vivo. Taken together, the unique mechanism in inhibiting cancer cell migration by AuNRs might provide a new approach to specific cancer therapeutic treatment. Inhibitory effects of gold nanorods on cancer cell migration and the underlying mechanisms are revealed. After endocytosed by cancer cells, gold nanorods down‐regulate the expression of energy generation‐related genes, decrease mitochondrial oxidative phosphorylation and glycolysis, reduce ATP synthesis, impair F‐actin cytoskeletal assembly and lamellipodia formation, and finally inhibit cancer cell migration.
      PubDate: 2014-09-05T03:15:30.607037-05:
      DOI: 10.1002/adfm.201401642
  • Cactus Stem Inspired Cone‐Arrayed Surfaces for Efficient Fog
    • Authors: Jie Ju; Xi Yao, Shuai Yang, Lin Wang, Ruize Sun, Yaxu He, Lei Jiang
      Pages: 6933 - 6938
      Abstract: With the increasing world population and the rapid development of the global industry, clean water is becoming scarcer and scarcer. Means of translating latent water in fog to dominant available water, i.e., fog collection, therefore becomes highly desirable. Previously, it was demonstrated that the cactus O. Microdasys has an integrated fog collection system arising from the evenly distributed clusters of spines and trichomes on the cactus stem. Here, it is reported that the intersite of the clusters on the cactus stem is densely covered with cones, which are also capable of collecting water from fog efficiently. Inspired by these cones, using a simple method combining mechanical perforating and template replica technology, polydimethylsiloxane (PDMS) cone arrays are fabricated with different arrangements and the one in hexagonal arrangement proves to be more efficient due to the more turbulent flow filed around the staggered cones and the rapid directional movement of water drops along each cone. This investigation opens up new avenue to collect water efficiently and may also provide clues to research about dust filtering and smog removal, which is attracting increasing attention worldwide. The intersite of clusters of spines on a cactus stem is found to be densely covered with cones, which can collect fog efficiently. Inspired by this, artificial cones are fabricated with different arrangements using mechanical perforation followed by template replication. The as‐prepared surface, which has hexagonally arranged cones, is proven to be efficient at collecting fog arising from the turbulent fog flow around the cones and the directional drop movement along the cones.
      PubDate: 2014-09-01T09:29:38.169707-05:
      DOI: 10.1002/adfm.201402229
  • Hierarchical Ordering of Quantum Dots and Liquid with Tunable
           Super‐Periodicity into High Aspect Ratio Moiré Superlattice
    • Authors: Soo‐Yeon Cho; Hwan‐Jin Jeon, Jong‐Seon Kim, Jong Min Ok, Hee‐Tae Jung
      Pages: 6939 - 6947
      Abstract: In this work, a new approach for construction of high aspect ratio complex moiré superlattice structure with versatile super‐periodicity is developed using the moiré fringe and secondary sputtering lithography. Wide assortments of high aspect ratio complex superstructures having different features on a 10 nm scaled wall are easily fabricated from simple starting components. More important is the finding of a new microscale phenomenon, consisting in trapping fluids in the centres of the moiré hexagonal fringes, as the consequence of the modulation of local hydrophilicty of the pattern. Using this phenomenon, target materials can be selectively and hierarchically confined within the moiré superlattice. Hierarchical nanoparticles (QDs) ordering with tunable super‐periodicity into selective area of moiré superlattice are successfully demonstrated by just solution‐casting of toluene based QD solution on patterned surfaces. This observation is expected to elucidate the key morphological factors that govern the physics of liquid behavior on a complex patterned substrate. Accordingly, in the near future, this facile approach for complex superlattice structure could be used as optical substrate for imaging applications and open interesting perspectives in the assembly processes and the handling of the nano‐microsized particles. A powerful new method is reported for fabricating complex lateral superlattice structures with 10 nm resolution, using the moiré fringe and secondary sputtering lithography. A large assortment of moiré superstructures can be easily fabricated by a simple rotation of the periodic layer. These superlattice structures widen the range of application of moiré patterns to not only the fields of photonics or optical characterization tools, but also to functional nano materials trapping and ordering.
      PubDate: 2014-09-01T09:35:57.472943-05:
      DOI: 10.1002/adfm.201401981
  • Nanotubes: Self‐Compensated Insulating ZnO‐Based Piezoelectric
           Nanogenerators (Adv. Funct. Mater. 44/2014)
    • Authors: Dohwan Kim; Keun Young Lee, Manoj Kumar Gupta, Subrata Majumder, Sang‐Woo Kim
      Pages: 6948 - 6948
      Abstract: High performance piezoelectric nanogenerators based on self‐compensated insulating ZnO via native defect control are demonstrated by S.‐W. Kim and co‐workers on page 6949. Self‐compensation of donor and acceptor type native defects makes ZnO insulating. Without additional passivation agents, dramatic enhancement of the piezoelectric output performance is observed compared to a donor defect rich ZnO NG under same mechanical strain.
      PubDate: 2014-11-20T08:28:01.117054-05:
      DOI: 10.1002/adfm.201470288
  • Self‐Compensated Insulating ZnO‐Based Piezoelectric
    • Authors: Dohwan Kim; Keun Young Lee, Manoj Kumar Gupta, Subrata Majumder, Sang‐Woo Kim
      Pages: 6949 - 6955
      Abstract: Remarkable enhancement of piezoelectric power output from a nanogenerator (NG) based on a zinc oxide (ZnO) thin film is achieved via native defect control. A large number of unintentionally induced point defects that act as n‐type carriers in ZnO have a strong influence on screening the piezoelectric potential into a piezoelectric NG. Here, additional oxygen molecules bombarded into ZnO lead to oxygen‐rich conditions, and the n‐type conductivity of ZnO is decreased dramatically. The acceptor‐type point defects such as zinc vacancies created during the deposition process trap n‐type carriers occurring from donor‐type point defects through a self‐compensation mechanism. This unique insulating‐type ZnO thin film‐based NGs (IZ‐NGs) generates output voltage around 1.5 V that is over ten times higher than that of an n‐type ZnO thin film‐based NG (around 0.1 V). In addition, it is found that the power output performance of the IZ‐NG can be further increased by hybridizing with a p‐type polymer (poly(3‐hexylthiophene‐2,5‐diyl):phenyl‐C61‐butyric acid methyl ester) via surface free carrier neutralization. High performance piezoelectric nanogenerators based on self‐compensated insulating ZnO via native defect control are demonstrated. Self‐compensation of donor and acceptor‐type native defects makes ZnO insulating. Without additional passivation agents, dramatic enhancement of the piezoelectric output performance from the insulating ZnO‐based piezoelectric nanogenerator is observed compared to a donor‐defect‐rich ZnO‐based piezoelectric nanogenerator under the same mechanical strain.
      PubDate: 2014-09-12T09:59:52.61376-05:0
      DOI: 10.1002/adfm.201401998
  • Directed Self‐Assembly as a Route to Ferromagnetic and
           Superparamagnetic Nanoparticle Arrays
    • Authors: Laura T. Schelhas; Richard A. Farrell, Udayabagya Halim, Sarah H. Tolbert
      Pages: 6956 - 6962
      Abstract: Block co‐polymer patterns are attractive candidates for nanoparticle assemblies. Directed self‐assembly of block co‐polymers in particular allows for long range ordering of the patterns, making them interesting scaffolds for the organization of magnetic particles. Here, a method to tune the channel width of polymer‐derived trenches via atomic layer deposition (ALD) of alumina is reported. The alumnia coating provides a much more thermally robust pattern that is stable up to 250 °C. Using these patterns, magnetic coupling in both ferromagnetic and superparamagnetic nanocrystal chains is achieved. Self‐assembled alumina coated block co‐polymer patterned substrates are used to organize ferromagnetic and superparamagnetic nanoparticles into arrays. The alumina coating creates a patterned substrate with tuneability of the trench width, while at the same time making the material robust to both heating and solvent‐based deposition.
      PubDate: 2014-09-01T09:18:58.868745-05:
      DOI: 10.1002/adfm.201401921
  • Ultrasmall Graphene Oxide Supported Gold Nanoparticles as Adjuvants
           Improve Humoral and Cellular Immunity in Mice
    • Authors: Yuhua Cao; Yufei Ma, Mengxin Zhang, Haiming Wang, Xiaolong Tu, He Shen, Jianwu Dai, Huichen Guo, Zhijun Zhang
      Pages: 6963 - 6971
      Abstract: Adjuvants play an important role in vaccines. Alum and MF59 are two dominant kinds of adjuvants used in humans. Both of them, however, have limited capacity to generate the cellular immune response required for vaccines against cancers and viral diseases. It is desirable to develop new and efficient adjuvants with the aim of improving the cellular immune response against the antigen. Here, the feasibility and efficiency of ultrasmall graphene oxide supported gold nanoparticles (usGO‐Au) as a new immune adjuvant to improve immune responses are explored. usGO‐Au is obtained from reduction of chloroauric acid using usGO and then decorated with ovalbumin (OVA, a model antigen) through physical adsorption to construct usGO‐Au@OVA. As the results show, the as‐synthesized usGO‐Au@OVA can efficiently stimulate RAW264.7 cells to secrete tumor necrosis factor‐α (TNF‐α), a mediator for cellular immune response. In vivo studies demonstrate that usGO‐Au@OVA can also promote robust OVA specific antibody response, CD8+ T cells proliferation, and different cytokines secretion. The results indicate that using usGO‐Au as an adjuvant can stimulate potent humoral and cellular immune responses against antigens, which may promote better understanding of cellular immune response and facilitate potential applications for cancer and viral vaccines. Gold nanoparticles grown in situ on ultra­small graphene oxide (usGO) are decorated with antigen ovalbumin (OVA) through physically adsorbing and Au‐S bonding. The usGO‐Au@OVA composites can efficiently stimulate RAW264.7 cells to secrete tumor necrosis factor‐α and promote an OVA‐specific antibody response, CD8+ T cells proliferation, and different cytokines secretion, thus demonstrating the capability to promote potent humoral and cellular immune responses.
      PubDate: 2014-09-01T09:30:57.438514-05:
      DOI: 10.1002/adfm.201401358
  • Spectroscopic Evaluation of Mixing and Crystallinity of Fullerenes in Bulk
    • Authors: Anne A. Y. Guilbert; Malte Schmidt, Annalisa Bruno, Jizhong Yao, Simon King, Sachetan M. Tuladhar, Thomas Kirchartz, M. Isabel Alonso, Alejandro R. Goñi, Natalie Stingelin, Saif A. Haque, Mariano Campoy‐Quiles, Jenny Nelson
      Pages: 6972 - 6980
      Abstract: The microstructure of blend films of conjugated polymer and fullerene, especially the degree of mixing and crystallization, impacts the performance of organic photovoltaic devices considerably. Mixing and crystallization affect device performance in different ways. These phenomena are not easy to screen using traditional methods such as imaging. In this paper, the amorphous regiorandom poly(3‐hexylthiophene) is blended with the potentially crystalline fullerene [6,6]‐phenyl‐C61‐butyric acid methyl ester PCBM and the amorphous bis‐adduct. First, the degree of mixing of polymer: fullerene blends is evaluated using UV–Vis absorption, steady‐state and ultra‐fast photoluminescence spectroscopy. The blue‐shift of the polymer emission and absorption onset are used in combination with the saturation of the polymer emission decay time upon fullerene addition in order to infer the onset of aggregation of the blends. Second, the crystallinity of the fullerene is probed using variable angle spectroscopic ellipsometry (VASE), electroluminescence and photoluminescence spectroscopy. It is shown that the red‐shift of charge transfer emission in the case of PCBM based blends cannot be explained solely by a variation of optical dielectric constant as probed by VASE. A combination of optical spectroscopy techniques, therefore, allows to probe the degree of mixing and can also distinguish between aggregation and crystallization of fullerenes. It is demonstrated that a combination of optical spectroscopy techniques such as UV–Vis absorption, steady‐state and ultra‐fast photoluminescence, electro­luminescence, and variable angle spectroscopic ellipsometry can be used to probe the degree of mixing of polymer:fullerene blends but also distinguishes between aggregation and crystallization of fullerenes. Both degree of mixing and crystallization have a huge impact on the organic photo­voltaic device performance.
      PubDate: 2014-09-02T12:53:53.884309-05:
      DOI: 10.1002/adfm.201401626
  • A Top Coat with Solvent Annealing Enables Perpendicular Orientation of
           Sub‐10 nm Microdomains in Si‐Containing Block Copolymer Thin
    • Authors: Eunjin Kim; Wonjung Kim, Kwang Hee Lee, Caroline A. Ross, Jeong Gon Son
      Pages: 6981 - 6988
      Abstract: Achieving sub‐10 nm high‐aspect‐ratio patterns from diblock copolymer self‐assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high‐χ copolymer typically have very different surface energies, favoring in‐plane microdomain orientations. A fully perpendicular orientation of a high‐χ block copolymer, poly(styrene‐block‐dimethylsiloxane) (PS‐b‐PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through‐thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of micro­domains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film. A top coat layer in the solvent annealing system can be a general approach for perpendicular orientation of microdomains in high‐interaction parameter (χ) block copolymer microdomains. They simultaneously employ top surface neutrality and sufficient film thickness for the control of the solvent concentration gradient and evaporation rate.
      PubDate: 2014-09-01T09:29:31.172637-05:
      DOI: 10.1002/adfm.201401678
  • Competitive Absorption and Inefficient Exciton Harvesting: Lessons Learned
           from Bulk Heterojunction Organic Photovoltaics Utilizing the Polymer
           Acceptor P(NDI2OD‐T2)
    • Authors: Zhi Li; Jason D. A. Lin, Hung Phan, Alexander Sharenko, Christopher M. Proctor, Peter Zalar, Zhihua Chen, Antonio Facchetti, Thuc‐Quyen Nguyen
      Pages: 6989 - 6998
      Abstract: Organic solar cells utilizing the small molecule donor 7,7′‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(6‐fluoro‐4‐(5′‐hexyl‐[2,2′‐bithiophen]‐5‐yl)benzo[c][1,2,5] thiadiazole) (p‐DTS(FBTTh2)2 and the polymer acceptor poly{[N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)}(P(NDI2OD‐T2)) are investigated and a power conversion efficiency of 2.1% is achieved. By systematic study of bulk heterojunction (BHJ) organic photovoltaic (OPV) quantum efficiency, film morphology, charge transport and extraction and exciton diffusion, the loss processes in this blend is revealed compared to the blend of [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) and the same donor. An exciton diffussion study using Förster resonant energy transfer (FRET) shows the upper limit of the P(NDI2OD‐T2) exciton diffusion length to be only 1.1 nm. The extremely low exciton diffusion length of P(NDI2OD‐T2), in combination with the overlap in donor and acceptor absorption, is then found to significantly limit device performance. These results suggest that BHJ OPV devices utilizing P(NDI2OD‐T2) as an acceptor material will likely be limited by its low exciton diffusion length compared to devices utilizing functionalized fullerene acceptors, especially when P(NDI2OD‐T2) significantly competes with the donor molecule for photon absorption. Organic solar cells based on a small molecule donor and the polymer acceptor P(NDI2OD‐T2) are fabricated and investigated. Through a comprehensive study of the optical and electronic properties of the blend films, the poor exciton diffusion length of P(NDI2OD‐T2) is identified as the primary cause of the poor performance. In order to make non‐fullerene acceptors competitive, the exciton diffusion length must be considered.
      PubDate: 2014-09-02T12:55:06.713715-05:
      DOI: 10.1002/adfm.201401367
  • Dual Bioresponsive Mesoporous Silica Nanocarrier as an “AND”
           Logic Gate for Targeted Drug Delivery Cancer Cells
    • Authors: Xin Chen; Alexander H. Soeriyadi, Xun Lu, Sharon M. Sagnella, Maria Kavallaris, J. Justin Gooding
      Pages: 6999 - 7006
      Abstract: Despite the rapid development of drug delivery vehicles that react to a specific biological environment, the complexity of triggering drug release in a particular target area remains an enduring challenge. Here, the engineering of bioresponsive polymer‐mesoporous silica nanoparticles (MSNs) with function akin to an AND logic gate is described. Polycaprolactone (esterase degradable) is immobilized into the core of MSNs while polyacrylic acid (PAA), which is pH responsive, covered the outside of the MSNs to create a PAA‐PCL‐MSNs construct. Fluorescence spectroscopy indicates that the construct releases the payload (doxorubicin, cancer drugs) in the presence of, and only in the presence of, both low pH AND esterase. Confocal microscopy and fluorescence lifetime microscopy (FLIM) demonstrate uptake of the intact construct and subsequent intracellular doxorubicin (DOX) delivery into the nucleus. Further in vitro IC50 studies demonstrate the AND logic gate delivery system results in more than an eightfold efficacy against neuroblastoma (SK‐N‐BE(2)) cells in comparison with normal fibroblasts (MRC‐5). These results demonstrate the utility of MSN‐polymer construct to create an AND gate capable of selectively delivering a drug payload. Logic “AND” gate drug release: Mesoporous silica nanoparticle (MSNs) with an “AND” logic gated provided by dual bioresponsive polymeric system polyacrylic acid (pH responsive) and polycaprolactone (enzyme degradable) for tumor targeting drug delivery nanocarrier. DOX‐loaded PAA‐PCL‐MSNs system is shown to selectively release DOX only with low pH and enzyme presence and results in an eightfold efficacy towards cancer cells compare to healthy cells.
      PubDate: 2014-09-05T03:28:31.550365-05:
      DOI: 10.1002/adfm.201402339
  • Regular Metal Sulfide Microstructure Arrays Contributed by
           Ambient‐Connected Gas Matrix Trapped on Superhydrophobic Surface
    • Authors: Shasha Wang; Yuchen Wu, Xiaonan Kan, Bin Su, Lei Jiang
      Pages: 7007 - 7013
      Abstract: Controlling the position of metal sulfide architectures is prerequisite and facilitates their device applications in solar cells, light‐emitting diodes, and many other optoelectronic fields. Thanks to ambient‐connected gas network trapped upon superhydrophobic surfaces, H2S gas can be continuously transported and reacted with metal ions along solid/liquid/gas triphase contact interface. Therefore, precisely positioning metal sulfide microstructure arrays are generated accordingly. The growth mechanisms as well as influencing factors are investigated to tailor the morphology, structure, and chemical composition of these metal sulfide materials. This interface‐mediated strategy can be widely applied to many other metal sulfides, such as PbS, MnS, Ag2S, and CuS. In particular, heterostructured metal sulfide architectures, such as PbS/CdS concentric microflower arrays, can be generated by stepwise replacement of metal ions inside liquid, exhibiting the advanced applications of this interface‐mediated growth strategy. Owing to ambient‐connected gas network trapped upon superhydrophobic surfaces, H2S gas can be continuously transported and react with metal ions along solid/liquid/gas triphase contact interface, forming precisely positioning metal sulfide microstructure arrays. This strategy can be widely applied to many metal sulfides and heterostructured metal sulfide architectures, such as PbS/CdS concentric microflower arrays, exhibiting the advanced applications of this interface‐mediated growth strategy.
      PubDate: 2014-09-05T03:27:45.080883-05:
      DOI: 10.1002/adfm.201401975
  • Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified
           Phosphonic Acid Self‐Assembled Monolayers
    • Authors: Ilja Lange; Sina Reiter, Michael Pätzel, Anton Zykov, Alexei Nefedov, Jana Hildebrandt, Stefan Hecht, Stefan Kowarik, Christof Wöll, Georg Heimel, Dieter Neher
      Pages: 7014 - 7024
      Abstract: Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers. The tuning of the ZnO work function from 4.1 to 5.7 eV is realized by the application of a variety of phosphonic acid based self‐assembled monolayers (SAMs). This enables the use of ZnO as both the electron‐ and hole‐injecting contact. The homogenous dense packing of the SAMs is thoroughly characterized using a range of complementary techniques.
      PubDate: 2014-09-05T03:28:26.856081-05:
      DOI: 10.1002/adfm.201401493
  • Novel and Enhanced Optoelectronic Performances of Multilayer
           MoS2–WS2 Heterostructure Transistors
    • Authors: Nengjie Huo; Jun Kang, Zhongming Wei, Shu‐Shen Li, Jingbo Li, Su‐Huai Wei
      Pages: 7025 - 7031
      Abstract: Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS2–WS2 heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS2 or WS2. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 103. The planar device also exhibits high field‐effect ON/OFF ratio (>105), high electron mobility of 65 cm2/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS2 or WS2 nanoflake transistors. The results suggest that formation of MoS2–WS2 heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications. Newly designed MoS 2 –WS 2 heterostructures perform novel and enhanced optoelectronic performances. Vertical transistors possess new functionalities such as rectifying, bipolarity, photovoltaic effect, and self‐driven photodetection. Planar devices exhibit superior optoelectronic properties with high field‐effect ON/OFF ratio (>105), electron mobility of 65 cm2/Vs, and photoresponsivity of 1.42 A/W that far exceed the one for their constituents MoS2 or WS2.
      PubDate: 2014-09-05T03:27:33.662463-05:
      DOI: 10.1002/adfm.201401504
  • In Situ Fabrication of Three‐Dimensional Graphene Films on Gold
           Substrates with Controllable Pore Structures for High‐Performance
           Electrochemical Sensing
    • Authors: Lei Shi; Zhenyu Chu, Yu Liu, Wanqin Jin, Nanping Xu
      Pages: 7032 - 7041
      Abstract: In this work, novel three‐dimensional graphene films (3D GFs) with controllable pore structures are directly fabricated on gold substrates through the hydrothermal reduction. An interfacial technique of the self‐assembled monolayer is successfully introduced to address the binding issue between the graphene film and substrate. Adscititious silica spheres, serving as new connection centers, effectively regulate the dimensions of framework in graphene films, and secondary pore structures are produced once removing the spheres. Based on hierarchically porous 3D GFs with large surface area, excellent binding strength, high conductivity, and distinct interfacial micro‐environments, selected examples of electrochemical aptasensors are constructed for the assay of adenosine triphosphate (ATP) and thrombin (Tob) respectively. Sensitive ATP and Tob aptasensors, with high selectivity, excellent stability, and promising potential in real serum sample analysis, are established on 3D GFs with different structures. The results demonstrate that the surface area, as well as interfacial micro‐environments, plays a critical role in the molecular recognition. The developed reliable and scalable protocol is envisaged to become a general path for in situ fabrication of more graphene films and the as‐synthesized 3D GFs would open up a wide horizon for potential applications in electronic and energy‐related systems. Three dimensional graphene film s (GFs) with controllable pore structures are directly fabricated on the gold substrate through a facile and reliable approach. The resulting GFs exhibit large surface area, excellent binding strength and high conductivity, which will enable many advanced applications in electronic and energy‐related systems. As examples, novel electrochemical aptasensors with high performance are constructed in this work.
      PubDate: 2014-09-05T03:27:12.581202-05:
      DOI: 10.1002/adfm.201402095
  • Pyrolysed 3D‐Carbon Scaffolds Induce Spontaneous Differentiation of
    • Authors: Letizia Amato; Arto Heiskanen, Claudia Caviglia, Fozia Shah, Kinga Zór, Maciej Skolimowski, Marc Madou, Lauge Gammelgaard, Rasmus Hansen, Emma G. Seiz, Milagros Ramos, Tania Ramos Moreno, Alberto Martínez‐Serrano, Stephan S. Keller, Jenny Emnéus
      Pages: 7042 - 7052
      Abstract: Structurally patterned pyrolysed three‐dimensional carbon scaffolds (p3D‐carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine‐producing neurons and the 3D‐topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to‐date unseen efficiency in both two‐dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D‐carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differentiation to dopaminergic phenotype combined with real‐time in situ confirmation of the fate of the hNSC‐derived neurons. Pyrolysed 3D carbon scaffolds dimensionally reaching the limit of UV‐lithography are for the first time presented and applied for differentiation of human neural stem cells (hNSCs), demonstrating the uniqueness of pyrolysed carbon as a material that induces spontaneous differentiation in 80% of hNSCs into dopaminergic neurons. The scaffold simultaneously serves as a mechanical and biocompatible support and 3D electrochemical sensor for dopamine detection.
      PubDate: 2014-09-11T12:35:31.681525-05:
      DOI: 10.1002/adfm.201400812
  • Delivery of iPS‐NPCs to the Stroke Cavity within a Hyaluronic Acid
           Matrix Promotes the Differentiation of Transplanted Cells
    • Authors: Jonathan Lam; William E. Lowry, S. Thomas Carmichael, Tatiana Segura
      Pages: 7053 - 7062
      Abstract: Stroke is the leading cause of adult disability with ≈80% being ischemic. Stem cell transplantation has been shown to improve functional recovery. However, the overall survival and differentiation of these cells is still low. The infarct cavity is an ideal location for transplantation as it is directly adjacent to the highly plastic peri‐infarct region. Direct transplantation of cells near the infarct cavity has resulted in low cell viability. Here, neural progenitor cells derived from induce pluripotent stem cells (iPS‐NPC) are delivered to the infarct cavity of stroked mice encapsulated in a hyaluronic acid hydrogel matrix to protect the cells. To improve the overall viability of transplanted cells, each step of the transplantation process is optimized. Hydrogel mechanics and cell injection parameters are investigated to determine their effects on the inflammatory response of the brain and cell viability, respectively. Using parameters that balanced the desire to keep surgery invasiveness minimal and cell viability high, iPS‐NPCs are transplanted to the stroke cavity of mice encapsulated in buffer or the hydrogel. While the hydrogel does not promote stem cell survival one week post‐transplantation, it does promote differentiation of the neural progenitor cells to neuroblasts. Hydrogels can be used to deliver neural progenitor cells to the brain post‐stroke. Comprehensively studying the parameters involved in the transplantation process allows to keep cells viable in the infarct cavity post‐transplantation. Further, delivering induced pluripotent cell‐derived neural progenitors encapsulated in the hydrogel promotes differentiation to a neuronal phenotype compared to a cell only condition.
      PubDate: 2014-09-05T00:00:00-05:00
      DOI: 10.1002/adfm.201401483
  • Cancer Treatment: Inhibition of Cancer Cell Migration by Gold Nanorods:
           Molecular Mechanisms and Implications for Cancer Therapy (Adv. Funct.
           Mater. 44/2014)
    • Authors: Teng Zhou; Meifang Yu, Bo Zhang, Liming Wang, Xiaochun Wu, Hejiang Zhou, Yipeng Du, Junfeng Hao, Yaping Tu, Chunying Chen, Taotao Wei
      Pages: 7064 - 7064
      Abstract: A quantitative proteomic analysis by C. Chen, T. Wei, and co‐workers on page 6922 shows that gold nanorods (AuNRs) effectively inhibit the metastatic phenotype of cancer cells by modulating the expression of energy metabolism‐related genes, which might provide a new direction for future investigations of functionalized AuNRs as a nano‐platform for cancer therapy.
      PubDate: 2014-11-20T08:27:55.576819-05:
      DOI: 10.1002/adfm.201470290
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