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

2D Materials     Hybrid Journal  
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 31)
ACS Catalysis     Full-text available via subscription   (Followers: 23)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 13)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 7)
ACS Macro Letters     Full-text available via subscription   (Followers: 16)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 24)
ACS Nano     Full-text available via subscription   (Followers: 215)
ACS Photonics     Full-text available via subscription   (Followers: 2)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 8)
Acta Chemica Iasi     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 5)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 2)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 4)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 8)
Advanced Functional Materials     Hybrid Journal   (Followers: 31)
Advances in Chemical Engineering and Science     Open Access   (Followers: 21)
Advances in Chemical Science     Open Access   (Followers: 8)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 13)
Advances in Drug Research     Full-text available via subscription   (Followers: 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: 11)
Advances in Nanoparticles     Open Access   (Followers: 10)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Polymer Science     Hybrid Journal   (Followers: 38)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 9)
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: 1)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access  
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alchemy     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Applied Sciences     Open Access   (Followers: 27)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 128)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 17)
American Journal of Plant Physiology     Open Access   (Followers: 9)
American Mineralogist     Full-text available via subscription   (Followers: 2)
Analyst     Full-text available via subscription   (Followers: 34)
Angewandte Chemie     Hybrid Journal   (Followers: 11)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 177)
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: 9)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 11)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 12)
Applied Surface Science     Hybrid Journal   (Followers: 14)
Arabian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 4)
Autophagy     Full-text available via subscription  
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 163)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 4)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 4)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 16)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 30)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 24)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 12)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 11)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Carbohydrate Research     Hybrid Journal   (Followers: 10)
Carbon     Hybrid Journal   (Followers: 34)
Catalysis for Sustainable Energy     Open Access   (Followers: 1)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 4)
Catalysis Science and Technology     Free   (Followers: 4)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 6)
Cellulose     Hybrid Journal   (Followers: 4)
Central European Journal of Chemistry     Hybrid Journal   (Followers: 5)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Functional Materials
   [33 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  [1602 journals]   [SJR: 4.862]   [H-I: 136]
  • Carbon-Interconnected Ge Nanocrystals as an Anode with Ultra-Long-Term
           Cyclability for Lithium Ion Batteries
    • Authors: Duc Tung Ngo; Ramchandra S. Kalubarme, Hang T. T. Le, John G. Fisher, Choong-Nyeon Park, Il-Doo Kim, Chan-Jin Park
      Pages: n/a - n/a
      Abstract: Germanium (Ge) possesses a great potential as a high-capacity anode material for lithium ion batteries but suffers from its poor capacity retention and rate capability due to significant volume expansion by lithiation. Here, a facile synthetic route is introduced for producing nanometer-sized Ge crystallites interconnected by carbon (GEC) via thermal decomposition of a Ge-citrate complex followed by a calcination process in an inert atmosphere. The GEC electrode shows outstanding electrochemical performance, i.e., an almost 98.8% capacity retention of 1232 mAh g−1, even after 1000 cycles at the rate of C/2. Importantly, a high discharge capacity of 880 mAh g−1 is maintained at the very high rate of 10 C. The excellent anode performance of GEC stems from both effective buffering of carbon anchored to the Ge nanocrystals and the high open porosity of the GEC aggregated powder with an average pore diameter of 32 nm. Furthermore, the interfacial layer formed between Ge and carbon plays an essential role in prolonging the cycle life. The GEC electrode can be successfully employed as an anode for next generation lithium ion batteries. A novel, facile synthetic route to produce nanometer-sized Ge interconnected by carbon is proposed. Amorphous GeO2/C composite is synthesized by the decomposition of a germanium-citrate complex at relatively low temperature followed by calcination in an inert atmosphere. Low-temperature reaction prevents the aggregation of Ge observed at high temperatures. Electrodes based on nanometer-sized Ge interconnected by a carbon layer show excellent electrochemical performances and great potential as anode materials for lithium ion batteries.
      PubDate: 2014-06-24T12:09:06.839284-05:
      DOI: 10.1002/adfm.201400888
  • Conjugated Polymers of Intrinsic Microporosity (C-PIMs)
    • Authors: Ge Cheng; Baltasar Bonillo, Reiner S. Sprick, Dave J. Adams, Tom Hasell, Andrew I. Cooper
      Pages: n/a - n/a
      Abstract: Conjugated microporous polymers (CMPs) have shown great potential for energy and environmental issues, however, poor solubility and processability of most of these materials limit their applications. Herein, a range of linear conjugated polymers of intrinsic microporosity (C-PIMs) is reported, combining for the first time the properties of conjugated microporous polymers, such as tunable electronic properties and compositional variation, with those of linear polymers of intrinsic microporosity (PIMs) allowing for solution processability and film formation. These soluble materials have a number of potential applications, for example as components in devices where large, porous interfaces are combined with extended electronic conjugation. A range of linear conjugated polymers of intrinsic microporosity (C-PIMs) is reported, combining for the first time the properties of conjugated microporous polymers (tunable electronic properties, compositional variation) and linear polymers of intrinsic microporosity (PIMs; solution processability and film formation). These soluble materials have a number of potential applications, for example as components in devices where large, porous interfaces are combined with extended electronic conjugation.
      PubDate: 2014-06-24T10:14:44.105626-05:
      DOI: 10.1002/adfm.201401001
  • Bifunctional Separator with a Light-Weight Carbon-Coating for Dynamically
           and Statically Stable Lithium-Sulfur Batteries
    • Authors: Sheng-Heng Chung; Arumugam Manthiram
      Pages: n/a - n/a
      Abstract: Sulfur is appealing as a high-capacity cathode for rechargeable lithium batteries as it offers a high theoretical capacity of 1672 mA h g−1 and is abundant. However, the commercialization of Li-S batteries is hampered by fast capacity fade during both dynamic cell cycling and static cell resting. The poor electrochemical stability is due to polysulfide diffusion, leading to a short cycle life and severe self-discharge. Here, we present the design of a bifunctional separator with a light-weight carbon-coating that integrates the two necessary components already inside the cell: the conductive carbon and the separator. With no extra additives, this bifunctional carbon-coated separator allows the use of pure sulfur cathodes involving no complex composite synthesis process, provides a high initial discharge capacity of 1389 mA h g−1 with excellent dynamic stability, and facilitates a high reversible capacity of 828 mA h g−1 after 200 cycles. In addition, the static stability is evidenced by low self-discharge and excellent capacity retention after a 3 month rest period. A bifunctional separator with a light-weight carbon-coating offers excellent dynamic electrochemical stability with Li-S cells: a high initial discharge capacity of 1389 mA h g−1 and long cycle life. The static electrochemical stability is further evidenced by low self-discharge and excellent capacity retention after a 3 month rest period.
      PubDate: 2014-06-24T10:14:37.590895-05:
      DOI: 10.1002/adfm.201400845
  • Co-deposited Cu(I) Complex for Tri-layered Yellow and White Organic
           Light-Emitting Diodes
    • Authors: Xiaochen Liu; Tao Zhang, Tianchi Ni, Nan Jiang, Zhiwei Liu, Zuqiang Bian, Zhenghong Lu, Chunhui Huang
      Pages: n/a - n/a
      Abstract: Four compounds 4-[3,6-di(carbazol-9-yl)carbazol-9-yl]isoquinoline (TCIQ), 3-[3,6-di(carbazol-9-yl)carbazol-9-yl]pyridine (TCPy), 4-(carbazol-9-yl)isoquinoline (4CIQ), and 3-(carbazol-9-yl)pyridine (CPy) containing pyridyl or isoquinolyl were designed and synthesized to co-deposition with copper iodide (CuI) to form luminescent Cu(I) complex doped film in situ, which could be utilized as the emissive layer in organic light-emitting diodes (OLEDs). It is found that simple tri-layered yellow and white OLEDs can be achieved by co-depositing CuI and TCIQ with tuning ratios. The compound TCIQ serves a dual role as both a ligand for forming the emissive Cu(I) complex and as a host matrix for the formed emitter in yellow OLEDs, and a third role as a blue emitter in white OLEDs. Four pyridyl or isoquinolyl containing compounds are designed and synthesized to co-deposition with copper iodide (CuI) in a vacuum chamber to form luminescent Cu(I) complex doped film, which could be utilized as the emissive layer in organic light-emitting diodes (OLEDs). Consequently, efficient and simplified tri-layered yellow and white OLEDs are achieved by varying the CuI doping concentrations.
      PubDate: 2014-06-24T10:14:29.036992-05:
      DOI: 10.1002/adfm.201400685
  • Nanometric Micelles with Photo‐Triggered Cytotoxicity
    • Authors: Parambath Anilkumar; Edmond Gravel, Ioanna Theodorou, Karine Gombert, Benoit Thézé, Frédéric Ducongé, Eric Doris
      Pages: n/a - n/a
      Abstract: The development of a photo‐responsive micellar system capable of triggering cell death is reported. Precursors of the micelles are synthesized by connecting a lipophilic chain to a hydrophilic polyethylene glycol via a photo‐labile nitrobenzyl group. The resulting amphiphilic units are self‐assembled in water forming 12 nm micelles that are readily internalized into cells. Upon photo‐irradiation, micelles undergo cleavage and yield a cytotoxic nitrosobenzaldehyde derivative, which significantly inhibits the proliferation of MDA‐MB‐231 cells under standard in vitro conditions. The development of a photo‐responsive micellar system capable of triggering cell death is reported. Illumination of the photo‐responsive micelles produces a cytotoxic species that is utilized in the on‐demand inhibition of cellular proliferation.
      PubDate: 2014-06-24T01:32:53.253308-05:
      DOI: 10.1002/adfm.201400840
  • An All‐Ceramic Solid‐State Rechargeable Na+‐Battery
           Operated at Intermediate Temperatures
    • Authors: Tao Wei; Yunhui Gong, Xuan Zhao, Kevin Huang
      Pages: n/a - n/a
      Abstract: A major challenge to the development of the next‐generation all‐solid‐state rechargeable battery technology is the inferior performance caused by insufficient ionic conductivity in the electrolyte and poor mixed ionic‐electronic conductivity in the electrodes. Here we demonstrate the utility of elevated temperature as an advantageous means of enhancing the conductivity in the electrolyte and promoting the catalytic activity at electrodes in an all‐ceramic rechargeable Na+‐battery. The new Na+‐battery consists of a 154‐μm thick Na‐β′′‐Al2O3 electrolyte membrane, a 22‐μm thick P2‐Na2/3[Fe1/2Mn1/2]O2 cathode and 52‐μm thick Na2Ti3O7‐La0.8Sr0.2MnO3 composite anode. The battery is shown to be capable of producing a reversible and stable capacity of 152 mAhg−1 at 350 °C. While the battery's achievable capacity is limited by the electrode materials employed, it does exhibit unique low self‐discharge rate, high tolerance to thermal cycling and an outstanding safety feature. A ceramic based solid state rechargeable Na+‐battery is demonstrated with good reversible and stable capacity when operated at 250–350 °C, extremely low self‐discharge rate, and excellent tolerance to thermal cycling.
      PubDate: 2014-06-24T01:30:28.723302-05:
      DOI: 10.1002/adfm.201400773
  • Large, Temperature‐Tunable Low‐Field Magnetoresistance in
           La0.7Sr0.3MnO3:NiO Nanocomposite Films Modulated by Microstructures
    • Authors: Xingkun Ning; Zhanjie Wang, Zhidong Zhang
      Pages: n/a - n/a
      Abstract: Magnetic properties and low‐field magnetoresistance (LFMR) in La0.7Sr0.3MnO3 (LSMO):NiO nanocomposite films grown on SrTiO3 (001) substrates have been investigated, which are shown to be tunable with different microstructures. The LSMO:NiO nanocomposite films with NiO volume ratio of 50% have a checkerboard‐like structure and show a large LFMR in a temperature range from 200 to 300 K (≈17% at 250 K with a magnetic field of 1 T). As the NiO volume ratio is increased to 70%, a nano‐columnar structure formed in the films. Their LFMR is significantly enhanced at a wide temperature range of 10–210 K. The highest value of LFMR with 41% was achieved at 10 K in a magnetic field of 1 T. The enhanced LFMR can be considered to result from the electron scattering at the ferromagnetic LSMO/NiO interfaces and magnetic tunnel junctions (MTJs) of LSMO/NiO/LSMO at the nanometer scale. Our results demonstrate that large and tunable LFMR from low temperature to room temperature can be realized by controlling the microstructures in the epitaxial La0.7Sr0.3MnO3:NiO nano­composite thin films, which will be expected to be applied in the devices using for a wide temperature range. (LSMO)5:(NiO)5 nanocomposite films have a checkerboard‐like structure and show a large LFMR in a temperature range from 200 to 300 K (≈17% at 250 K with a magnetic field of 1T). By contrast, the (LSMO)3:(NiO)7 nanocomposite films have anano‐columnar structure with a large LFMR of 41% at 10 K and1 T.
      PubDate: 2014-06-24T01:28:59.689746-05:
      DOI: 10.1002/adfm.201400735
  • Construction of White‐Light‐Emitting Silk Protein Hybrid Films
           by Molecular Recognized Assembly among Hierarchical Structures
    • Authors: Naibo Lin; Fan Hu, Yilin Sun, Chenxu Wu, Hongyao Xu, Xiang Yang Liu
      Pages: n/a - n/a
      Abstract: The fabrication of bio‐hybrid functional films is demonstrated by applying a materials assembly technique. Based on the hierarchical structures of silk fibroin materials, functional molecular/materials, ie., quantum dots (QDs), can be fixed to amino acid groups in silk fibroin films. It follows that white‐light‐emitting QD silk hybrid films are obtained by hydrogen bond molecular recognition to the –COO– groups functionalized to blue luminescent ZnSe (5.2 nm) and yellow luminescent CdTe (4.1 nm) QDs in a molar ratio of 30:1 of ZnSe to CdTe QDs. Simultaneously, a systematic blue shift in the emission peak is observed from the QD solution to QDs silk fibroin films. The significant blue shift hints the appearance of the strong interaction between QDs and silk fibroins, which causes strong white‐light‐emitting uniform silk films. The molecular recognized interactions are confirmed by high resolution transmission electron microscopy, field scanning electron microscope, and attenuated total internal reflectance fourier transform infrared spectroscopy. The QD silk films show unique advantages, including simple preparation, tunable white‐light emission, easy manipulation, and low fabrication costs, which make it a promising candidate for multicomponent optodevices. White‐light‐emitting silk protein/quantum dot hybrid films are successfully prepared by controlling the molar ratio of blue luminescent ZnSe and yellow luminescent CdTe quantum dots via an assembly method based on hydrogen bonding. The silk films with uniform quantum dot dispersion show unique advantages, and are a promising candidate for application in optical devices.
      PubDate: 2014-06-24T01:27:44.834543-05:
      DOI: 10.1002/adfm.201400249
  • Precise Tuning of (YBa2Cu3O7‐δ)1‐x:(BaZrO3)x Thin Film
           Nanocomposite Structures
    • Authors: Run Zhao; Weiwei Li, Joon Hwan Lee, Eun Mi Choi, Yan Liang, Wei Zhang, Rujun Tang, Haiyan Wang, Quanxi Jia, Judith L. MacManus‐Driscoll, Hao Yang
      Pages: n/a - n/a
      Abstract: Self‐assembled nanocomposite films and coatings have huge potential for many functional and structural applications. However, control and manipulation of the nanostructures is still at very early stage. Here, guidelines are established for manipulating the types of composite structures that can be achieved. In order to do this, a well studied (YBa2Cu3O7‐δ)1‐x:(BaZrO3)x ‘model’ system is used. A switch from BaZrO3 nanorods in YBa2Cu3O7‐δ matrix to planar, horizontal layered plates is found with increasing x, with a transitional cross‐ply structure forming between these states at x = 0.4. The switch is related to a release in strain energy which builds up in the YBa2Cu3O7‐δ with increasing x. At x = 0.5, an unusually low strain state is observed in the planar composite structure, which is postulated to arise from a pseudo‐spinodal mechanism. The precise tuning of inorganic nanocomposite thin films is realized using (YBa2Cu3O7‐δ)1‐x:(BaZrO3)x as a model system. A nanostructure switch from a vertical columnar structure to a horizontal multilayered structure is found with a transition, cross‐ply structure at x = 0.4. Energetic considerations are used to explain the observed structures.
      PubDate: 2014-06-23T02:44:11.407333-05:
      DOI: 10.1002/adfm.201304302
  • A Lithium‐Sulfur Battery with a High Areal Energy Density
    • Authors: Joo‐Seong Kim; Tae Hoon Hwang, Byung Gon Kim, Jaeyun Min, Jang Wook Choi
      Pages: n/a - n/a
      Abstract: The battery community has recently witnessed a considerable progress in the cycle lives of lithium‐sulfur (Li‐S) batteries, mostly by developing the electrode structures that mitigate fatal dissolution of lithium polysulfides. Nonetheless, most of the previous successful demonstrations have been based on limited areal capacities. For realistic battery applications, however, the chronic issues from both the anode (lithium dendrite growth) and the cathode (lithium polysulfide dissolution) need to be readdressed under much higher loading of sulfur active material. To this end, the current study integrates the following three approaches in a systematic manner: 1) the sulfur electrode material with diminished lithium polysulfide dissolution by the covalently bonded sulfur‐carbon microstructure, 2) mussel‐inspired polydopamine coating onto the separator that suppresses lithium dendrite growth by wet‐adhesion between the separator and Li metal, and 3) addition of cesium ions (Cs+) to the electrolyte to repel incoming Li ions and thus prevent Li dendrite growth. This combined strategy resolves the long‐standing problems from both electrodes even under the very large sulfur‐carbon composite loading of 17 mg cm−2 in the sulfur electrode, enabling the highest areal capacity (9 mAh cm−2) to date while preserving stable cycling performance. The highest areal energy density to date of a lithium‐sulfur battery is demonstrated by the combined smart engineering of the key cell components (electrode, electrolyte, and separator). The integrated strategy suppresses both lithium polysulfide dissolution from the sulfur cathode and lithium dendrite growth from the lithium anode, leading to the highest areal capacity of 9 mAh cm−2 while preserving stable cyclability.
      PubDate: 2014-06-23T02:36:49.342833-05:
      DOI: 10.1002/adfm.201400935
  • Multi‐Alternating Organic Semiconducting Films with High Electric
    • Authors: Hin‐Wai Mo; Ming‐Fai Lo, Qing‐Dan Yang, Tsz‐Wai Ng, Chun‐Sing Lee
      Pages: n/a - n/a
      Abstract: High electric conductivity is observed in multilayer stack of m‐MTDATA/F16CuPc. Impedance data shows that the circuit resistance is significantly dropped by three orders of magnitude from ∼0.2 MΩ to ∼0.4 kΩ when the number of alternating units is increased from one to six, keeping a total thickness of 300 nm. Impedance results show that as the number of alternating units increases, the organic stack shows an increasing capacitance and a decreasing resistance. This result suggests the increasing charges accumulate at the heterojunctions, leading to reduction in overall film resistance. The application of the high conductive units in OLED device results in stability enhancement. High conductivity in a thick organic multi­layer stack (up to 4 × 102 S cm‐1) is reported. It is shown that the high conductivity comes from the charge‐transfer complex interface between m‐MTDATA and F16CuPc.
      PubDate: 2014-06-23T02:34:14.360878-05:
      DOI: 10.1002/adfm.201400468
  • Optical Gain in the Near Infrared by Light‐Emitting Electrospun
    • Authors: Giovanni Morello; Maria Moffa, Salvatore Girardo, Andrea Camposeo, Dario Pisignano
      Pages: n/a - n/a
      Abstract: The potential integration of polymer nanofibers in photonic devices and circuits is a major driver for research on their waveguiding and optical gain properties. Emission in the near‐infrared is especially important in this framework in view of the realization of nanofiber‐based optical amplifiers. Here, the optical gain properties of electrospun fibers embedding near‐infrared light‐emitting molecules are investigated. Upon pulsed optical pumping, line narrowing typical of amplified spontaneous emission is observed, with gain of 5.5 cm−1 and threshold fluence down to 0.25 mJ cm−2. Importantly, the stimulated emission characteristics are strongly dependent on individual fiber characteristics and on the mutual alignment of nanofibers in arrays, thus being tailorable through the fiber architecture and assembling. These results open interesting perspectives for the exploitation of electrospun fibers as active components in the near‐infrared range. Optical gain in the near infrared spectral range is demonstrated in electrospun fibers. The fibers can be aligned in free‐standing arrays and show amplified spontaneous emission as well as self‐waveguiding properties. The infrared optical gain opens the way for the embedding of electrospun materials in fiber amplifiers and nanolasers.
      PubDate: 2014-06-23T01:37:26.975826-05:
      DOI: 10.1002/adfm.201400395
  • Masthead: (Adv. Funct. Mater. 24/2014)
    • Pages: n/a - n/a
      PubDate: 2014-06-20T02:10:39.296539-05:
      DOI: 10.1002/adfm.201470160
  • Synergistic Enhancement of Lung Cancer Therapy Through
           Nanocarrier‐Mediated Sequential Delivery of Superantigen and Tyrosin
           Kinase Inhibitor
    • Authors: Da Li; Yongbin Li, Haibo Xing, Junling Guo, Yuan Ping, Guping Tang
      Pages: n/a - n/a
      Abstract: Gefitinib (GFT) and other tyrosine kinase inhibitors (TKIs) have been widely used for the treatment of advanced or metastatic lung cancer due to their reduced side effects when compared to classic cytotoxic chemotherapeutic agents. However, both intrinsic and acquired resistance often hinders the effectiveness of TKIs. Based on recent findings that the outcome of chemotherapy can be influenced by the host immune system at multiple levels, an exploration of whether activating antitumor immunity improves the efficacy of the targeted cancer therapy of TKIs is undertaken. To this end, a cationic carrier is used to deliver superantigen and GFT in a simultaneous or sequential manner. The sequential delivery of superantigen and GFT can significantly enhance T cell immunity, promote cytokine production, inhibit tumor growth, and prolong survival time in tumor models with lung carcinoma xenografts. Most importantly, dual sequential treatment reveals a synergistic effect on tumor inhibition, which is much more effective than the monotherapy of either GFT or pTSA, as well as the combined treatment through simultaneous codelivery of pTSA and GFT together. This study demonstrates the important contribution of immunotherapy to targeted molecular therapy and opens up new possibilities for treating a wide spectrum of cancers. Sequential delivery of superantigen and tryrosin kinase inhibitor by nanocarriers is proven to synergistically promote lung cancer therapy. The new therapeutic modality combines the advantages of superantigens to activate antitumor immunity with the specificity feature of tyrosine kinase inhibitors to selectively induce tumor cell apoptosis. This proof‐of‐concept study defines a unique strategy of effective lung cancer therapy for future clinical translation.
      PubDate: 2014-06-20T02:01:56.498956-05:
      DOI: 10.1002/adfm.201400456
  • Understanding Lattice Strain‐Controlled Charge Transport in Organic
           Semiconductors: A Computational Study
    • Authors: Xiaoyan Zheng; Hua Geng, Yuanping Yi, Qikai Li, Yuqian Jiang, Dong Wang, Zhigang Shuai
      Pages: n/a - n/a
      Abstract: The softness and anisotropy of organic semiconductors offer unique properties. Recently, solution‐sheared thin‐films of 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐P) with nonequilibrium single‐crystal domains have shown much higher charge mobilities than unstrained ones (Nature2011, 480, 504). However, to achieve efficient and targeted modulation of charge transport in organic semiconductors, a detailed microscopic understanding of the structure–property relationship is needed. In this work, motivated by the experimental studies, the relationship between lattice strain, molecular packing, and charge carrier mobility of TIPS‐P crystals is elucidated. By employing a multiscale theoretical approach combining nonequilibrium molecular dynamics, first‐principles calculations, and kinetic Monte Carlo simulations using charge‐transfer rates based on the tunneling enabled hopping model, charge‐transport properties of TIPS‐P under various lattice strains are investigated. Shear‐strained TIPS‐P indeed exhibits one‐dimensional charge transport, which agrees with the experiments. Furthermore, either shear or tensile strain lead to mobility enhancement, but with strong charge‐transport anisotropy. In addition, a combination of shear and tensile strains could not only enhance mobility, but also decrease anisotropy. By combining the shear and tensile strains, almost isotropic charge transport could be realized in TIPS‐P crystal with the hole mobility improved by at least one order of magnitude. This approach enables a deep understanding of the effect of lattice strain on charge carrier transport properties in organic semiconductors. Motivated by recent solution‐shearing experiments, a multiscale theoretical approach is employed to investigate charge‐transport properties of 6,13‐bis(triisopropylsilylethynyl) pentacene under various lattice strains, enabling a deep understanding of the lattice strain–molecular packing–charge carrier mobility relationship. The elucidated structure–property relationship is a prerequisite to efficient and targeted control of charge transport in organic semiconductors.
      PubDate: 2014-06-20T02:01:51.795344-05:
      DOI: 10.1002/adfm.201400261
  • Luminescent Graphene Oxide with a Peptide‐Quencher Complex for
           Optical Detection of Cell‐Secreted Proteases by a Turn‐On
    • Authors: Seon‐Yeong Kwak; Jin‐Kyoung Yang, Su‐Ji Jeon, Hye‐In Kim, Joonhyuk Yim, Homan Kang, San Kyeong, Yoon‐Sik Lee, Jong‐Ho Kim
      Pages: n/a - n/a
      Abstract: Graphene oxide (GO) is an emerging luminescent nanomaterial with photostable and unique photoluminescence (PL) in the visible and near‐infrared region. Herein, a GO PL‐based optical biosensor consisting of a luminescent GO donor covalently linked with a peptide‐quencher complex is reported for the simple, rapid, and sensitive detection of proteases. To this end, the quenching efficiency of various candidate quenchers of GO fluorescence, such as metalloprotoporphyrins and QXL570, are examined and their quenching mechanisms investigated. A fluorescence resonance energy transfer‐based quencher, QXL570, is found to be much more effective for quenching the intrinsic fluorescence of GO than other charge transfer‐based quenchers. The designed GO–peptide–QXL system is then able to sensitively detect specific proteases—chymotrypsin and matrix metalloproteinase‐2—via a “turn‐on” response of quenched GO fluorescence after proteolytic cleavage of the quencher. Finally, the GO–peptide–QXL hybrid successfully detects MMP‐2 secreted from living cells—human hepatocytes HepG2—with high sensitivity. A graphene oxide (GO) fluorescence‐based protease sensor consisting of a luminescent GO donor conjugated with a peptide‐quencher complex detects cell‐secreted proteases. The most effective quencher for GO fluorescence creates a GO–peptide–QXL optical sensor for protease detection. The quenched fluorescence of GO is restored by the proteolytic cleavage of a peptide quencher moiety from the sensor. This “turn‐on” optical sensor detects MMP‐2 secreted from live cells with high sensitivity.
      PubDate: 2014-06-20T02:01:47.079516-05:
      DOI: 10.1002/adfm.201400001
  • Trilevel‐Structured Superhydrophobic Pillar Arrays with Tunable
           Optical Functions
    • Authors: Sanghyuk Wooh; Jai Hyun Koh, Soojin Lee, Hyunsik Yoon, Kookheon Char
      Pages: n/a - n/a
      Abstract: Water‐repelling surfaces inspired by lotus leaves have been developed for their commercial needs in superhydrophobic and self‐cleaning coatings on glasses and windows. The extraordinary properties originate from their multiscale structures with waxy materials. To obtain high transparency as well as superhydrophobicity, microhair arrays are designed with large spacing to reduce optical scattering effects caused by microstructures, but with a trilevel hierarchical structure to compensate for the loss of superhydrophobicity. In this study, a soft molding technique on wet pastes consisting of nanoparticles (NPs) is proposed to create a multilevel hierarchical structure of sub‐100 nm nanoparticles, which demonstrates excellent water repellency. Additionally, full advantage is taken of the TiO2 NP mesoporous structure for UV protection and for its ability to attach to various kinds of functional (for example, photoresponsive) dyes. Furthermore, the stability of fluorinated surfaces against UV light is enhanced by the passivation of the TiO2 surface with a thin silica coating. A highly transparent multilevel structure consisting of sub‐100 nm nanoparticles with excellent water repellency is deve­loped using a soft molding technique. Suppressing Mie scattering, high transparency is achieved in the structure with a low density of micro‐features. Moreover, a thin silica film and photoresponsive dyes attached to TiO2 nanoparticles are further introduced to realize multifunctional surfaces with high stability against UV light.
      PubDate: 2014-06-18T06:42:20.352096-05:
      DOI: 10.1002/adfm.201400228
  • Organic Field Effect Transistors Based on Graphene and Hexagonal Boron
           Nitride Heterostructures
    • Authors: Seok Ju Kang; Gwan‐Hyoung Lee, Young‐Jun Yu, Yue Zhao, Bumjung Kim, Kenji Watanabe, Takashi Taniguchi, James Hone, Philip Kim, Colin Nuckolls
      Pages: n/a - n/a
      Abstract: Enhancing the device performance of single crystal organic field effect transistors (OFETs) requires both optimized engineering of efficient injection of the carriers through the contact and improvement of the dielectric interface for reduction of traps and scattering centers. Since the accumulation and flow of charge carriers in operating organic FETs takes place in the first few layers of the semiconductor next to the dielectric, the mobility can be easily degraded by surface roughness, charge traps, and foreign molecules at the interface. Here, a novel structure for high‐performance rubrene OFETs is demonstrated that uses graphene and hexagonal boron nitride (hBN) as the contacting electrodes and gate dielectric layer, respectively. These hetero‐stacked OFETs were fabricated by lithography‐free dry‐transfer method that allows us to transfer graphene and hBN on top of an organic single crystal, forming atomically sharp interfaces and efficient charge carrier‐injection electrodes without damage or contamination. The resulting heterostructured OFETs exhibit both high mobility and low operating gate voltage, opening up new strategy to make high‐performance OFETs and great potential for flexible electronics. Organic field effect transistors (OFETs) based on 2D graphene and hexagonal boron nitride heterostructures are fabricated by a dry‐transfer method. The resulting heterostructured OFETs exhibit both high mobility and low operating voltage due to the atomically sharp interfaces of hBN flake and efficient charge carrier‐injection from graphene electrodes.
      PubDate: 2014-06-16T07:51:54.377501-05:
      DOI: 10.1002/adfm.201400348
  • Flipping the Switch on Clathrin‐Mediated Endocytosis using Thermally
           Responsive Protein Microdomains
    • Authors: Martha K. Pastuszka; Curtis T. Okamoto, Sarah F. Hamm‐Alvarez, J. Andrew MacKay
      Pages: n/a - n/a
      Abstract: A ubiquitous approach to studying protein function is to knock down activity (gene deletions, siRNA, small molecule inhibitors, etc.) and to study the cellular effects. Using a new methodology, this article describes how to rapidly and specifically switch off cellular pathways using thermally responsive protein polymers. A small increase in temperature stimulates cytosolic elastin‐like polypeptides (ELPs) to assemble microdomains. It is hypothesized that ELPs fused to a key effector in a target macromolecular complex will sequester the complex within these microdomains, which will bring the pathway to a halt. To test this hypothesis, ELPs are fused to clathrin‐light chain (CLC), a protein associated with clathrin‐mediated endocytosis. Prior to thermal stimulation, the ELP fusion is soluble and clathrin‐mediated endocytosis remains “on”. Increasing the temperature induces the assembly of ELP fusion proteins into organelle‐sized microdomains that switches clathrin‐mediated endocytosis “off”. These microdomains can be thermally activated and inactivated within minutes, are reversible, do not require exogenous chemical stimulation, and are specific for components trafficked within the clathrin‐mediated endocytosis pathway. This temperature‐triggered cell switch system represents a new platform for the temporal manipulation of trafficking mechanisms in normal and disease cell models and has applications for manipulating other intracellular pathways. A rapid, reversible approach for the selective knock‐down of clathrin‐mediated internalization is developed by attaching a thermally responsive elastin‐like polypeptide to clathrin light‐chain, a known marker of receptor mediated endocytosis. The resulting system is active when the ELP is soluble. When raised above the ELP's transition temperature, the ELPs assemble microdomains that sequester the machinery of clathrin‐mediated endocytosis and specifically inhibit receptor internalization.
      PubDate: 2014-06-16T00:44:50.306621-05:
      DOI: 10.1002/adfm.201400715
  • Enzyme Prodrug Therapy Engineered into Biomaterials
    • Authors: Ana C. Mendes; Alexander N. Zelikin
      Pages: n/a - n/a
      Abstract: In this work, enzyme‐prodrug therapy (EPT) is engineered into hydrogel biomaterials to achieve localized synthesis of the drugs and their delivery to the adhering cells. The use of EPT in the context of drug delivery mediated by biomaterials significantly empowers the latter in that the same hydrogel is used to successfully synthesize several drugs with dissimilar structures and therapeutic effects. The concentration of the synthesized drugs is conveniently controlled by the concentration of the administered prodrugs. Using prodrugs for two therapeutic agents allows their synthesis and delivery with independent control over the concentration and the time of administration of each of the drugs. Using these tools, sequential delivery of drugs for anti‐inflammatory and anti‐proliferative activity is accomplished whereby the synthesis of drugs is mediated by the same enzyme‐functionalized hydrogel. The use of EPT to perform combination therapy mediated by an implantable biomaterial is also reported. Taken together, these results contribute significantly to the development of flexible and highly powerful tools of substrate‐mediated drug delivery with applications in the design of therapeutic implants and tissue engineering. Hydrogel biomaterials are equipped with the tools of biocatalysis to achieve in situ synthesis of drugs – locally, at the time point desired, and a dose to suit a particular application. It is demonstrated that biocatalytic hydrogels synthesize multiple, dissimilar therapeutic molecules: individually, sequentially, or in combination.
      PubDate: 2014-06-16T00:37:11.0128-05:00
      DOI: 10.1002/adfm.201304312
  • Efficiency Enhancement of Organic Light-Emitting Diodes Incorporating a
           Highly Oriented Thermally Activated Delayed Fluorescence Emitter
    • Authors: Christian Mayr; Sae Youn Lee, Tobias D. Schmidt, Takuma Yasuda, Chihaya Adachi, Wolfgang Brütting
      Abstract: An organic light-emitting diode (OLED) with the blue emitter CC2TA showing thermally activated delayed fluorescence (TADF) is presented exhibiting an external quantum efficiency (ηEQE) of 11% ± 1%, which clearly exceeds the classical limit for fluorescent OLEDs. The analysis of the emission layer by angular dependent photoluminescence (PL) measurements shows a very high degree of 92% horizontally oriented transition dipole moments. Excited states lifetime measurements of the prompt fluorescent component under PL excitation yield a radiative quantum efficiency of 55% of the emitting species. Thus, the radiative exciton fraction has to be significantly higher than 25% due to TADF. Performing a simulation based efficiency analysis for the OLED under investigation allows for a quantification of individual contributions to the efficiency increase originating from horizontal emitter orientation and TADF. Remarkably, the strong horizontal emitter orientation leads to a light-outcoupling efficiency of more than 30%. The thermally activated delayed fluorescence (TADF) emitter CC2TA shows a high degree of horizontal orientation. Using excited states lifetime measurements of the prompt fluorescence, its radiative quantum efficiency can be determined. This is the basis for a comprehensive analysis of the efficiency boost of organic light-emitting diodes beyond the classical limit due to emitter orientation and TADF.
      PubDate: 2014-06-11T04:23:24.663661-05:
      DOI: 10.1002/adfm.201400495
  • Interfaces: Structure and Disorder in Squaraine–C60 Organic Solar
           Cells: A Theoretical Description of Molecular Packing and Electronic
           Coupling at the Donor–Acceptor Interface (Adv. Funct. Mater.
    • Authors: Yao‐Tsung Fu; Demetrio A. da Silva Filho, Gjergji Sini, Abdullah M. Asiri, Saadullah Gary Aziz, Chad Risko, Jean‐Luc Brédas
      Pages: 3653 - 3653
      Abstract: Theoretical models of the squaraine‐C60 donor–acceptor interface reported on page 3790 by C. Risko, J.‐L. Brédas, and co‐workers probe how molecules pack, mix, and move and the subsequent impact on interfacial electronic properties of organic solar cells. The 3D molecular shape, disordered packing, and thermal motion at room temperature render electronic couplings small, regardless of the orientation of the underlying squaraine layers. Such insight is vital to develop a more robust understanding of the photoconversion process and offers principles for materials design.
      PubDate: 2014-06-20T02:10:40.349077-05:
      DOI: 10.1002/adfm.201470155
  • Crystallization: Nanoparticle Growth via Concentration Gradients Generated
           by Enzyme Nanopatterns (Adv. Funct. Mater. 24/2014)
    • Authors: Roberto de la Rica; Erhan Bat, Karla L. Herpoldt, Hai‐nan Xie, Sergio Bertazzo, Heather D. Maynard, Molly M. Stevens
      Pages: 3654 - 3654
      Abstract: Top‐down e‐beam lithography is combined with bottom‐up bioinspired crystal growth by R. de la Rica, M. M. Stevens, and co‐workers to grow nanoparticle clusters of controlled dimensions at desired locations on a chip. On page 3692, the key enabling factor to recreate biomineralization conditions is the patterning of enzyme nanoreactors as lines separated by nanometric distances such that the gradient of crystallization precursors generated by the enzymes is affected by the nanoscale organization of biocatalysts. Image Credit: Miguel Spuch‐Calvar.
      PubDate: 2014-06-20T02:10:40.831672-05:
      DOI: 10.1002/adfm.201470156
  • Contents: (Adv. Funct. Mater. 24/2014)
    • Pages: 3655 - 3660
      PubDate: 2014-06-20T02:10:43.618675-05:
      DOI: 10.1002/adfm.201470157
  • Electrical Properties of Carbon Nanotube Based Fibers and Their Future Use
           in Electrical Wiring
    • Authors: Agnieszka Lekawa‐Raus; Jeff Patmore, Lukasz Kurzepa, John Bulmer, Krzysztof Koziol
      Pages: 3661 - 3682
      Abstract: The production of continuous fibers made purely of carbon nanotubes has paved the way for new macro‐scale applications which utilize the superior properties of individual carbon nanotubes. These wire‐like macroscopic assemblies of carbon nanotubes were recognized to have a potential to be used in electrical wiring. Carbon nanotube wiring may be extremely light and mechanically stronger and more efficient in transferring high frequency signals than any conventional conducting material, being cost‐effective simultaneously. However, transfer of the unique properties of individual CNTs to the macro‐scale proves to be quite challenging. This Feature Article gives an overview of the potential of using carbon nanotube fibers as next generation wiring, state of the art developments in this field, and goals to be achieved before carbon nanotubes may be transformed into competitive products. Carbon nanotubes, with their unique properties, could make electrical conductors of unprecedented performance, which could revolutionize energy transport globally. Is it feasible to produce macroscopic conductors from nanoscale structures' This Feature Article presents both the most recent results of a highly promising research program in this area and the key challenges that need to be overcome.
      PubDate: 2014-03-17T02:24:28.007286-05:
      DOI: 10.1002/adfm.201303716
  • Optical Waveguiding: Remote Biosensing with Polychromatic Optical
           Waveguide Using Blue Light‐Emitting Organic Nanowires Hybridized
           with Quantum Dots (Adv. Funct. Mater. 24/2014)
    • Authors: Eun Hei Cho; Bong‐Gi Kim, Sumin Jun, Jubok Lee, Dong Hyuk Park, Kwang‐Sup Lee, Jeongyong Kim, Jinsang Kim, Jinsoo Joo
      Pages: 3683 - 3683
      Abstract: Polychromatic optical waveguiding is achieved for organic nanowires (NWs) hybridized with light‐emitting quantum dots (QDs). Remote biosensing using dye‐attached biomaterials is presented by J. Kim, J. Kim, J. Joo, and co‐workers by adapting the transportation of QD‐emitted light through the organic NWs. The cover image shows white‐color waveguiding and remote biosensing using blue light‐emitting organic NWs hybridized with QDs.
      PubDate: 2014-06-20T02:10:39.150255-05:
      DOI: 10.1002/adfm.201470158
  • Remote Biosensing with Polychromatic Optical Waveguide Using Blue
           Light‐Emitting Organic Nanowires Hybridized with Quantum Dots
    • Authors: Eun Hei Cho; Bong‐Gi Kim, Sumin Jun, Jubok Lee, Dong Hyuk Park, Kwang‐Sup Lee, Jeongyong Kim, Jinsang Kim, Jinsoo Joo
      Pages: 3684 - 3691
      Abstract: Nanometer‐scale optical waveguides are attractive due to their potential applicability in photonic integration, optoelectronic communication, and optical sensors. Nanoscale white light‐emitting and/or polychromatic optical waveguides are desired for miniature white‐light generators in microphotonic circuits. Here, polychromatic (i.e., blue, green, and red) optical waveguiding characteristics are presented using a novel hybrid composite of highly crystalline blue light‐emitting organic nanowires (NWs) combined with blue, green, and red CdSe/ZnS quantum dots (QDs). Near white‐color waveguiding is achieved for organic NWs hybridized with green and red QDs. Light, emitted from QDs, can be transferred to the organic NW and then optically waveguided through highly packed π‐conjugated organic molecules in the NW with different decay characteristics. Remote biosensing using dye‐attached biomaterials is presented by adapting the transportation of QD‐emitted light through the organic NW. Nanoscale polychromatic optical waveguides are demonstrated using a novel hybrid composite of highly crystalline blue light‐emitting organic nanowires (NWs) combined with blue, green, and red CdSe/ZnS quantum dots (QDs). The transportation of QD‐emission through the highly packed π‐conjugated organic NW enhanced the remote biosensing signal.
      PubDate: 2014-02-27T02:20:27.216726-05:
      DOI: 10.1002/adfm.201304039
  • Nanoparticle Growth via Concentration Gradients Generated by Enzyme
    • Authors: Roberto de la Rica; Erhan Bat, Karla L. Herpoldt, Hai‐nan Xie, Sergio Bertazzo, Heather D. Maynard, Molly M. Stevens
      Pages: 3692 - 3698
      Abstract: Biomineralizing organisms can grow nanomaterials with unexpected morphologies in an organic matrix where temporal and vectorial gradients of crystal growth precursors are established. Here, concentration gradients for the crystallization of gold nanoparticles are generated and applied on silicon substrates. Gradients of crystal growth precursors are generated by enzymes patterned as lines that are separated by distances ranging from the micro‐ to the nanoscale. The concentration of crystallization precursors around the lines separated by nanometric distances is not only determined by mass transport and enzyme activity but also by the nanoscale organization of biocatalysts. This nanoscale organization favors non‐classical crystal growth conditions that lead to the formation of nanoparticle clusters containing nanocrystals that are highly crystallographically aligned. The combination of bottom‐up crystal growth with top‐down electron beam lithography enables the fabrication of micrometric patterns containing gold nanoparticles of different size, shape, and surface density. These are all critical parameters that determine the physical properties of these nanomaterials. Concentrations gradients generated by enzyme patterns guide the growth of gold nanostructures with programmable size, shape, and state of aggregation. When the patterns are separated by nanometric distances, clusters of highly crystallographically aligned gold nanoscrystals are obtained, which suggests that the nanoparticles grow via biomimetic non‐classical crystal growth conditions.
      PubDate: 2014-02-26T09:42:03.260386-05:
      DOI: 10.1002/adfm.201304047
  • Construction and Molecular Understanding of an Unprecedented, Reversibly
           Thermochromic Bis‐Polydiacetylene
    • Authors: Songyi Lee; Joonseong Lee, Minji Lee, Yu Kyung Cho, Junwoo Baek, Jinwook Kim, Sungnam Park, Myung Hwa Kim, Rakwoo Chang, Juyoung Yoon
      Pages: 3699 - 3705
      Abstract: A new type of bis‐PDA, in which two PDAs are linked via an intervening p‐phenylene group, is developed. The Bis‐PDA‐Ph displays exceptional thermochromic reversibility owing to the presence of unique hydrophobic interactions between alkyl chains as well as aryl moieties. The Bis‐PDA‐Ph has a well‐packed structure that causes it to display a clear blue to red colorimetric transition at elevated temperatures. To elucidate the molecular origin of the thermochromic response, a theoretical simulation of the new PDA, the results of which successfully explain the thermochromic reversibility phenomenon, is conducted. Furthermore, Bis‐PDA‐Ph‐embedded polymer fibers are used as a thermochromic sensor material. It displays excellent reversibility between 20–120 °C, which is the largest temperature range reported thus far for PDA based sensors. Finally, transient absorption spectroscopy is employed for the first time to analyze the temperature‐dependent fluorescence change of the new PDA. The Bis‐PDA‐Ph (two PDAs are linked via an intervening p‐phenylene group) displays exceptional thermochromic reversibility with a blue to red colorimetric transition at elevated temperatures. To elucidate the molecular origin of the thermochromic response, a theoretical simulation of the new PDA which explains the reversibility phenomenon, is conducted. Furthermore, Bis‐PDA‐Ph‐embedded fibers display excellent reversibility between 20–120 °C.
      PubDate: 2014-02-26T09:42:19.980307-05:
      DOI: 10.1002/adfm.201304147
  • Localized Collection of Airborne Analytes: A Transport Driven Approach to
           Improve the Response Time of Existing Gas Sensor Designs
    • Authors: Jun Fang; Se‐Chul Park, Leslie Schlag, Thomas Stauden, Jörg Pezoldt, Heiko O. Jacobs
      Pages: 3706 - 3714
      Abstract: The detection of single binding has been a recent trend in sensor research introducing various sensor designs where the active sensing elements are nanoscopic in size. Currently, transport and collection of airborne analytes for gas sensors is either diffusion based or non‐localized and it becomes increasingly unlikely for analytes to interact with sensing structures where the active area is shrunk, trading an increased sensitivity with a slow response time. This report introduces a corona discharge based analyte charging method and an electrodynamic nanolens based analyte concentration concept to effectively transport airborne analytes to sensing points to improve the response time of existing gas sensor designs. Localized collection of analytes over a wide range, including microscopic particles, nanoparticles, and small molecules, is demonstrated. In all cases, the collection rate is several orders of magnitudes higher than in the case where the collection is driven by diffusion. The collection scheme is integrated on an existing SERS (surface‐enhanced Raman spectroscopy) based sensor. In terms of response time, the process is able to detect analytes at 9 ppm (parts per million) within 1 s. As a comparison, 1 h is required to reach the same signal level when diffusion‐only‐transport is used. In the field of sensors that target the detection of airborne analytes, the corona/lens‐based‐collection provide a new path to achieve high sensitivity which impacts the researches ranging from environmental monitoring systems to the detection of chemical/biological warfare agents. Specifically, it provides a route to transport, concentrate, and collect the airborn species to precise sensing points to improve the collection efficiency.
      PubDate: 2014-02-28T02:20:25.874253-05:
      DOI: 10.1002/adfm.201303829
  • Arrayed rGOSH/PMASH Microcapsule Platform Integrating Surface Topography,
           Chemical Cues, and Electrical Stimulation for Three‐Dimensional
           Neuron‐Like Cell Growth and Neurite Sprouting
    • Authors: Heng‐Wen Liu; Wei‐Chen Huang, Chih‐Sheng Chiang, Shang‐Hsiu Hu, Chia‐Hsin Liao, You‐Yin Chen, San‐Yuan Chen
      Pages: 3715 - 3724
      Abstract: The biocompatible thiol‐functionalized rGOSH/PMASH microcapsules encapsulating nerve growth factor (NGF) are arrayed onto a transparent and conductive substrate, i.e., indium tin oxide (ITO), to integrate electrically stimulated cellular differentiation, electrically controlled NGF release, and topographically rough nano‐surfaces into a 3‐D platform for nerve regeneration. The rGOSH/PMASH microcapsules with microscale topography function not only as an adhesive coating to promote the adhesion of PC12 cells but also as electroactive NGF‐releasing electrodes that stimulate NGF release and accelerate the differentiation of PC12 cells during electrical stimulation. Once electrical treatment is applied, NGF release and electrically enhanced cellular differentiation lead to an obvious increase both in the percentage of cells with neurites and in the neurite length. This length can reach nearly 90 μm within 2 days of cell culture. The average neurite length is significantly increased (four‐fold) after culture on the rGOSH/PMASH microcapsule substrate for 2 days compared with culture on a substrate without an rGOSH/PMASH coating. These multifunctional rGOSH/PMASH microcapsules may be used as potential 3‐D patterned substrates for neural regeneration and neural prosthetics in tissue engineering applications. The stimulus‐responsive, well‐ordered rGOSH/PMASH microcapsules are arrayed into a 3‐D ECM‐mimic flexible substrate to accelerate the proliferation and differentiation of PC12 cells by controlling NGF release and manipulating rGOSH/PMASH microcapsule interfaces. A combination of surface topography, chemical cues, and electrical stimulation not only has positive effects on cell viability but also strongly enhances the neurite outgrowth of PC12 cells.
      PubDate: 2014-03-04T04:45:21.341188-05:
      DOI: 10.1002/adfm.201303853
  • Efficient Self‐Assembly Synthesis of Uniform CdS Spherical
           Nanoparticles‐Au Nanoparticles Hybrids with Enhanced Photoactivity
    • Authors: Sancan Han; Linfeng Hu, Nan Gao, Ahmed A. Al‐Ghamdi, Xiaosheng Fang
      Pages: 3725 - 3733
      Abstract: The treatment of environmental pollution has become one of the most critical issues in the world. Despite the progress made in the study of semiconductor photocatalysis, it is still a challenge to obtain photocatalysts with high activity through relatively simple fabrication processes. In this work, monodisperse CdS spherical nanoparticles (SNPs) of various sizes and good crystallinity are obtained by only adjusting the starting ratio of reactants and the reaction temperature, exhibiting high photocatalytic performances. The photocatalytic rate constant of the ≈ 100 nm CdS SNPs, especially, is more than double that of P25. Furthermore, 3‐mercaptopropyltrimethoxysilane is used to assist the interaction between ≈ 200 nm CdS SNPs and citrate‐stabilized Au nanoparticles (NPs). The significant increase of photocatalytic activity is confirmed by the degradation of Rodamine B (RhB) under Xe light irradiation. At the optimal Au concentration (0.5 wt%), the prepared nanohybrids show the highest photocatalytic activity, exceeding that of pure CdS two times. The superior photocatalytic performances of the CdS SNPs‐Au nanohybrids can be attributed to the intimate interfacial contact between CdS SNPs and Au NPs, which is a contributing factor to the improvement of transfer and the fate of photogenerated charge carriers from CdS SNPs to Au NPs. The CdS SNPs‐Au NPs hybrids are firstly fabricated through gold‐sulfur bonding interaction, which meets the needs for reliable interfacial contact between the semiconductor and Au NPs. This facile strategy can be extended to the synthesis of other binary semiconductor hybrids. The as‐fabricated CdS SNPs‐Au NPs hybrids are very promising for application in degradation of organic pollutants.
      PubDate: 2014-03-06T07:37:06.721133-05:
      DOI: 10.1002/adfm.201400012
  • Enhancing Field‐Effect Mobility of Conjugated Polymers Through
           Rational Design of Branched Side Chains
    • Authors: Boyi Fu; Jose Baltazar, Ashwin Ravi Sankar, Ping‐Hsun Chu, Siyuan Zhang, David M. Collard, Elsa Reichmanis
      Pages: 3734 - 3744
      Abstract: The design of polymer semiconductors possessing effective π–π intermolecular interactions coupled with good solution processability remains a challenge. Structure‐property relationships associated with side chain structure, π–π intermolecular interactions, polymer solubility, and charge carrier transport are reported for a donor–acceptor(1)‐donor–acceptor(2) polymer: 5‐Decylheptadecyl (5‐DH), 2‐tetradecyl (2‐DT), and linear n‐octadecyl (OD) chains are substituted onto a polymer backbone consisting of terthiophene units (T) between two different electron acceptors, benzothiadiazole (B), and diketopyrrolopyrrole (D), pTBTD, to afford pTBTD‐5DH, pTBTD‐2DT, and pTBTD‐OD, respectively. In the 5‐DH side chain, the branching position is remote from the polymer backbone, whereas it is proximal in 2‐DT. This study demonstrates that incorporation of branched side chains where the branching position is remote from the polymer backbone merges the advantages of improved solubility from branched units with effective π–π intermolecular interactions normally associated with linear chains on conjugated polymers. pTBTD‐5DH exhibits superior qualities with respect to the degree of polymerization, solution processability, π–π interchain stacking, and charge carrier transport relative to the other analogs. pTBTD‐5DH exhibits a field‐effect hole mobility of up to 2.95 cm2 V–1 s–1, a factor of 3–7 times that achieved with pBDT6‐DT and pBDT6‐OD. 5‐Decylheptadecyl (5‐DH), 2‐tetradecyl (2‐DT), and n ‐octadecyl (OD) side chains are substituted into pTBTD polymer backbone. The branching position is remote or close to pTBTD in 5‐DH and 2‐DT. 5‐DH merges advantages of branched units (2‐DT) for improving solubility with those of linear chains (OD) in providing effective π–π intermolecular interactions. 5‐DH substituted pTBTD exhibits a field‐effect hole mobility reaching 2.95 cm2 V−1 s−1.
      PubDate: 2014-03-19T08:35:47.582708-05:
      DOI: 10.1002/adfm.201304231
  • Direct‐Current Triboelectric Generator
    • Authors: Ya Yang; Hulin Zhang, Zhong Lin Wang
      Pages: 3745 - 3750
      Abstract: The first direct‐current triboelectric generator (DC‐TEG) based on sliding electrification for harvesting mechanical energy from rotational motion is reported. The DC‐TEG consists of two rotating wheels and one belt for connecting them, which are made of distinctly different triboelectric materials with a specific requirement. During the rotation, the contact‐induced electrification and the relative sliding between the two wheels and the belt can induce a continuous increase of the accumulated positive and negative triboelectric charges at the two rotating wheels, respectively, resulting in a Corona discharge and producing the observed current through an external load. The DC‐TEG can deliver an open‐circuit voltage of larger than 3200 V and a maximum power of 100 μW under an external load of 60 MΩ at a rotational speed of 1000 r min–1. By designing a point metal discharge electrode near the accumulated positive charges on the metal wheel, the instantaneous short‐circuit current can be up to 0.37 mA. The DC‐TEG can be utilized as a direct power source to light up 1020 serially connected commercial light‐emitting diodes (LEDs) and the produced energy can also be stored in a capacitor for other uses. This work presents a DC‐TEG technology to harvest mechanical energy from rotational motion for self‐powered electronics. The first direct‐current triboelectric generator (DC‐TEG) for harvesting mechanical energy from rotational motion is reported. The DC‐TEG consists of two rotating wheels and one belt for connecting them, which are made of different triboelectric materials. The DC‐TEG can be utilized to light up 1020 commercial LEDs and the produced energy can also be stored in a capacitor for other uses.
      PubDate: 2014-03-04T08:32:42.693534-05:
      DOI: 10.1002/adfm.201304295
  • Nanopatterned Polymer Brushes for Triggered Detachment of
           Anchorage‐Dependent Cells
    • Authors: Qian Yu; Leah M. Johnson, Gabriel P. López
      Pages: 3751 - 3759
      Abstract: Surfaces modified with thermoresponsive poly(N‐isopropylacrylamide) (PNIPAAm) support mild and efficient harvesting of anchorage‐dependent cells. To enable cellular detachment, however, the surfaces must exhibit a narrow range of PNIPAAm thicknesses. In this work, this limitation is circumvented by introducing nanopatterns to grafted PNIPAAm brushes, eliminating the critical thickness requirement for cell‐culturing applications. Nanopatterned PNIPAAm surfaces are prepared using a combination of interferometric lithography (IL) and surface‐initiated polymerization. Above the lower critical solution temperature (LCST) of PNIPAAm (∼32 °C), these surfaces support the attachment and proliferation of mammalian cells (e.g., fibroblasts and endothelial cells). Below the LCST of PNIPAAm, cells readily detach from the nanopatterned PNIPAAm surfaces without influence from the period of nanopatterns, which vary between 157 ± 9 nm to 1021 ± 17 nm. Cells selectively attach and proliferate on PNIPAAm nanopatterns as compared to thick unpatterned PNIPAAm, which is further exploited to spatially direct cellular growth to generate cellular micropatterns. Nanopatterned PNIPAAm surfaces provide a unique solution to the critical thickness issue for cell harvesting and facilitate spatial control of cellular growth on surfaces. Thermoresponsive poly(N‐isopropylacrylamide) (PNIPAAm) brushes are nanopatterned via interferometric lithography and surface‐initiated polymerization to support mammalian cell harvesting. Above the lower critical solution temperature (LCST), collapsed PNIPAAm brushes expose extracellular matrix proteins on the underlying substrate to support cellular attachment. As the temperature decreases below the LCST, swollen, extended PNIPAAm nanopatterned brushes readily release attached cells.
      PubDate: 2014-03-13T01:29:25.911172-05:
      DOI: 10.1002/adfm.201304274
  • Turning ZnO into an Efficient Energy Upconversion Material by Defect
    • Authors: Jan E. Stehr; Shula L. Chen, Nandanapalli Koteeswara Reddy, Charles W. Tu, Weimin M. Chen, Irina A. Buyanova
      Pages: 3760 - 3764
      Abstract: Photon upconversion materials are attractive for a wide range of applications from medicine, biology, to photonics. Among them, ZnO is of particular interest owing to its outstanding combination of materials and physical properties. Though energy upconversion has been demonstrated in ZnO, the exact physical mechanism is still unknown, preventing control of the processes. Here, defects formed in bulk and nanostructured ZnO synthesized using standard growth techniques play a key role in promoting efficient energy upconversion via two‐step two‐photon absorption (TS‐TPA). From photoluminescence excitation of the anti‐Stokes emissions, the threshold energy of the TS‐TPA process is determined as being 2.10–2.14 eV in all studied ZnO materials irrespective of the employed growth techniques. This photo‐electron paramagnetic resonance studies show that this threshold closely matches the ionization energy of the zinc vacancy (a common grown‐in intrinsic defect in ZnO), thereby identifying the zinc vacancy as being the dominant defect responsible for the observed efficient energy upconversion. The upconversion is found to persist even at a low excitation density, making it attractive for photonic and photovoltaic applications. ZnO can be engineered via a common intrinsic defect into an efficient energy upconversion material. This finding paves the way for designing ZnO devices in which the energy upconversion can be exploited for improved and new photonic and photovoltaic applications.
      PubDate: 2014-03-31T01:10:09.175935-05:
      DOI: 10.1002/adfm.201400220
  • In situ Characterization of SiO2 Nanoparticle Biointeractions Using
    • Authors: Daniela Drescher; Ingrid Zeise, Heike Traub, Peter Guttmann, Stephan Seifert, Tina Büchner, Norbert Jakubowski, Gerd Schneider, Janina Kneipp
      Pages: 3765 - 3775
      Abstract: By adding a gold core to silica nanoparticles (BrightSilica), silica‐like nanoparticles are generated that, unlike unmodified silica nanoparticles, provide three types of complementary information to investigate the silica nano‐biointeraction inside eukaryotic cells in situ. Firstly, organic molecules in proximity of and penetrating into the silica shell in live cells are monitored by surface‐enhanced Raman scattering (SERS). The SERS data show interaction of the hybrid silica particles with tyrosine, cysteine and phenylalanine side chains of adsorbed proteins. Composition of the biomolecular corona of BrightSilica nanoparticles differs in fibroblast and macrophage cells. Secondly, quantification of the BrightSilica nanoparticles using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) micromapping indicates a different interaction of silica nanoparticles compared to gold nanoparticles under the same experimental conditions. Thirdly, the metal cores allow the investigation of particle distribution and interaction in the cellular ultrastructure by cryo nanoscale X‐ray tomography (cryo‐XT). In 3D reconstructions the assumption is confirmed that BrightSilica nanoparticles enter cells by an endocytotic mechanism. The high SERS intensities are explained by the beneficial plasmonic properties due to agglomeration of BrightSilica. The results have implications for the development of multi‐modal qualitative and quantitative characterization in comparative nanotoxicology and bionanotechnology. BrightSilica nanoparticles have a silica surface and a gold core. They provide information about their interaction with biological cells via three different approaches: 1) surface‐enhanced Raman scattering for characterization of the biomolecular species interacting with the silica sub‐/surface; 2) quantification of the uptake of silica‐like nanostructures by mass spectrometric micromapping, and; 3) understanding the 3D subcellular interaction using synchrotron X‐ray nanotomography.
      PubDate: 2014-03-20T02:53:31.277038-05:
      DOI: 10.1002/adfm.201304126
  • High Performance Mg2(Si,Sn) Solid Solutions: a Point Defect Chemistry
           Approach to Enhancing Thermoelectric Properties
    • Authors: Guangyu Jiang; Jian He, Tiejun Zhu, Chenguang Fu, Xiaohua Liu, Lipeng Hu, Xinbing Zhao
      Pages: 3776 - 3781
      Abstract: A point defect chemistry approach to improving thermoelectric (TE) properties is introduced, and its effectiveness in the emerging mid‐temperature TE material Mg2(Si,Sn) is demonstrated. The TE properties of Mg2(Si,Sn) are enhanced via the synergistical implementation of three types of point defects, that is, Sb dopants, Mg vacancies, and Mg interstitials in Mg2Si0.4Sn0.6‐xSbx with high Sb content (x> 0.1), and it is found that i) Sb doping at low ratios tunes the carrier concentration while it facilitates the formation of Mg vacancies at high doping ratios (x> 0.1). Mg vacancies act as acceptors and phonon scatters; ii) the concentration of Mg vacancies is effectively controlled by the Sb doping ratio; iii) excess Mg facilitates the formation of Mg interstitials that also tunes the carrier concentration; vi) at the optimal Sb‐doping ratio near x ≈ 0.10 the lattice thermal conductivity is significantly reduced, and a state‐of‐the‐art figure of merit ZT> 1.1 is attained at 750 K in 2 at% Zn doped Mg2Si0.4Sn0.5Sb0.1 specimen. These results demonstrate the significance of point defects in thermoelectrics, and the promise of point defect chemistry as a new approach in optimizing TE properties. A new point defect chemistry approach is proposed for enhancing thermoelectric properties, and demonstrated in typical Mg2(Si,Sn) based thermoelectric materials via synergistically implementing the point defects of Sb dopants, Mg vacancies, and Mg interstitials. High doping ratio of Sb facilitates the formation of Mg vacancies, which act as both acceptors and phonon scatters, and significantly reduce the lattice thermal conductivity.
      PubDate: 2014-04-01T07:06:09.584086-05:
      DOI: 10.1002/adfm.201400123
  • Organic Electronics: “Regioselective Deposition” Method to
           Pattern Silver Electrodes Facilely and Efficiently with High Resolution:
           Towards All‐Solution‐Processed, High‐Performance,
           Bottom‐Contacted, Flexible, Polymer‐Based Electronics (Adv.
           Funct. Mater. 24/2014)
    • Authors: Deyang Ji; Lang Jiang, Yunlong Guo, Huanli Dong, Jianpu Wang, Huajie Chen, Qing Meng, Xiaolong Fu, Guofeng Tian, Dezhen Wu, Gui Yu, Yunqi Liu, Wenping Hu
      Pages: 3782 - 3782
      Abstract: Small reaction, big application! The silver mirror reaction is a straightforward way to produce silver films, and can be performed using cheap reactants in aqueous solutions. Here, it is successfully introduced into organic electronics by L. Jiang, H. Dong, G. Yu, W. Hu, and co‐workers, and applied to the process of fabricating flexible, high‐performance, large‐area, all‐solution‐processable organic fieldeffect transistors at room temperature with high resolution.
      PubDate: 2014-06-20T02:10:39.085658-05:
      DOI: 10.1002/adfm.201470159
  • “Regioselective Deposition” Method to Pattern Silver
           Electrodes Facilely and Efficiently with High Resolution: Towards
           All‐Solution‐Processed, High‐Performance,
           Bottom‐Contacted, Flexible, Polymer‐Based Electronics
    • Authors: Deyang Ji; Lang Jiang, Yunlong Guo, Huanli Dong, Jianpu Wang, Huajie Chen, Qing Meng, Xiaolong Fu, Guofeng Tian, Dezhen Wu, Gui Yu, Yunqi Liu, Wenping Hu
      Pages: 3783 - 3789
      Abstract: “Regioselectivity deposition” method is developed to pattern silver electrodes facilely and efficiently by solution‐process with high resolution (down to 2 μm) on different substrates in A4 paper size. With the help of this method, large‐area, flexible, high‐performance polymer field‐effect transistors based on the silver electrodes and polyimide insulator are fabricated with bottom‐contact configuration by all‐solution processes. The polymer devices exhibit high performance with average field‐effect mobility over 1.0 cm2 V−1 s−1 (the highest mobility up to 1.5 cm2 V−1 s−1) and excellent environmental stability and flexibility, indicating the cost effectiveness of this method for practical applications in organic electronics. Large‐area, flexible, high‐performance all‐solution‐processed polymer field‐effect transistors are fabricated with bottom‐contact configuration with the help of “regioselectivity deposition” method. The polymer devices exhibit high performance (the highest mobility up to 1.5 cm2 V−1 s−1) and excellent environmental stability and flexibility, indicating the cost effectiveness of this method for practical applications in organic electronics.
      PubDate: 2014-02-20T17:19:45.496148-05:
      DOI: 10.1002/adfm.201304117
  • Structure and Disorder in Squaraine–C60 Organic Solar Cells: A
           Theoretical Description of Molecular Packing and Electronic Coupling at
           the Donor–Acceptor Interface
    • Authors: Yao‐Tsung Fu; Demetrio A. da Silva Filho, Gjergji Sini, Abdullah M. Asiri, Saadullah Gary Aziz, Chad Risko, Jean‐Luc Brédas
      Pages: 3790 - 3798
      Abstract: Organic solar cells based on the combination of squaraine dyes (as electron donors) and fullerenes (as electron acceptors) have recently garnered much attention. Here, molecular dynamics simulations are carried out to investigate the evolution of a squaraine–C60 bilayer interface as a function of the orientation and order of the underlying squaraine layer. Electronic couplings between the main electronic states involved in exciton dissociation and charge (polaron pair) recombination are derived for donor–acceptor complexes extracted from the simulations. The results of the combined molecular‐dynamics−quantum‐mechanics approach provide insight into how the degree of molecular order and the dynamics at the interface impact the key processes involved in the photovoltaic effect. A combined molecular dynamics–quantum mechanics approach reveals the complex landscape of the intermolecular electronic couplings at the squaraine–C60 (donor–acceptor) bilayer interface as a function of the interfacial molecular packing and dynamics. Such aspects are of importance when considering the operation of organic solar cells.
      PubDate: 2014-02-27T02:20:31.844798-05:
      DOI: 10.1002/adfm.201303941
  • Liquid Metal/Metal Oxide Frameworks
    • Authors: Wei Zhang; Jian Zhen Ou, Shi‐Yang Tang, Vijay Sivan, David D. Yao, Kay Latham, Khashayar Khoshmanesh, Arnan Mitchell, Anthony P. O'Mullane, Kourosh Kalantar‐zadeh
      Pages: 3799 - 3807
      Abstract: A new platform described as the liquid metal/metal oxide (LM/MO) framework is introduced. The constituent spherical structures of these frameworks are made of micro‐ to nanosized liquid metal spheres and nanosized metal oxides, combining the advantages of both materials. It is shown that the diameters of the spheres and the stoichiometry of the structures can be actively controlled. Additionally, the liquid suspension of these spheres demonstrates tuneable plasmon resonances. These spherical structures are assembled to form LM/MO frameworks which are capable of demonstrating high sensitivity towards low concentrations of heavy metal ions, and enhanced solar light driven photocalalytic activities. These demonstrations imply that the LM/MO frameworks are a suitable candidate for the development of future high performance electronic and optical devices. A new platform described as the liquid metal/metal oxide (LM/MO) framework is introduced. The constituent spherical structures of these frameworks are made of micro‐ to nanosized liquid metal spheres and nanosized metal oxides. These LM/MO frameworks demonstrate high sensitivity towards low concentrations of heavy metal ions and enhanced solar light driven photocalalytic activities.
      PubDate: 2014-03-10T05:05:36.756657-05:
      DOI: 10.1002/adfm.201304064
  • Polyethylene Imine as an Ideal Interlayer for Highly Efficient Inverted
           Polymer Light‐Emitting Diodes
    • Authors: Young‐Hoon Kim; Tae‐Hee Han, Himchan Cho, Sung‐Yong Min, Chang‐Lyoul Lee, Tae‐Woo Lee
      Pages: 3808 - 3814
      Abstract: Electron‐injecting interlayers (ILs) which are stable in air, inject electrons efficiently, block holes, and block quenching of excitons, are very important to realize efficient inverted polymer light‐emitting diodes (IPLEDs). Two air‐stable polymer electron‐injecting interlayers (ILs), branched polyethyleneimine (PEI) and polyethyleneimine ethoxylated (PEIE) for use in IPLEDs are introduced, and the roles of the ILs in IPLEDs comparing these with a conventional Cs2CO3 IL are elucidated. These polymer ILs can reduce the electron injection barrier between ZnO and emitting layer by decreasing the work function (WF) of underlying ZnO, thereby effectively facilitating electron injection into the emitting layer. WF of ZnO covered by PEI is found to be lower than that covered by PEIE due to higher [N+]/[C] ratio of PEI. Furthermore, they can block the quenching of excitons and increase the luminous efficiency of devices. Thus, IPLEDs with PEI IL of optimum thickness (8 nm) show current efficiency (13.5 cd A–1), which is dramatically higher than that of IPLEDs with a Cs2CO3 IL (8 cd A‐1). Efficient and air‐stable inverted polymer‐light emitting diodes (IPLEDs) can be realized by using insulating polymer electron‐injecting interlayers (ILs), branched polyethyleneimine (PEI), and polyethyleneimine ethoxylated (PEIE), giving highest current efficiencies of 13.5 cd A‐1 and 12 cd A‐1, respectively. Polymer ILs can facilitate electron injection into emitting layer as well as block the exciton quenching.
      PubDate: 2014-03-10T05:05:38.95856-05:0
      DOI: 10.1002/adfm.201304163
  • Three‐Dimensional Co3O4@MnO2 Hierarchical Nanoneedle Arrays:
           Morphology Control and Electrochemical Energy Storage
    • Authors: Dezhi Kong; Jingshan Luo, Yanlong Wang, Weina Ren, Ting Yu, Yongsong Luo, Yaping Yang, Chuanwei Cheng
      Pages: 3815 - 3826
      Abstract: In this paper, a highly ordered three‐dimensional Co3O4@MnO2 hierarchical porous nanoneedle array on nickel foam is fabricated by a facile, stepwise hydrothermal approach. The morphologies evolution of Co3O4 and Co3O4@MnO2 nanostructures upon reaction times and growth temperature are investigated in detail. Moreover, the as‐prepared Co3O4@MnO2 hierarchical structures are investigated as anodes for both supercapacitors and Li‐ion batteries. When used for supercapacitors, excellent electrochemical performances such as high specific capacitances of 932.8 F g−1 at a scan rate of 10 mV s−1 and 1693.2 F g−1 at a current density of 1 A g−1 as well as long‐term cycling stability and high energy density (66.2 W h kg−1 at a power density of 0.25 kW kg−1), which are better than that of the individual component of Co3O4 nanoneedles and MnO2 nanosheets, are obtained. The Co3O4@MnO2 NAs are also tested as anode material for LIBs for the first time, which presents an improved performance with high reversible capacity of 1060 mA h g−1 at a rate of 120 mA g−1, good cycling stability, and rate capability. Highly ordered Co3O4@MnO2 hierachical core–shell arrays on Ni foam are fabricated by a facile, stepwise hydrothermal approach and further investigated as anodes for both supercapacitors and Li‐ion batteries (LIBs), which present greatly improved performance.
      PubDate: 2014-03-14T01:20:25.77478-05:0
      DOI: 10.1002/adfm.201304206
  • Vapor Phase Metal‐Assisted Chemical Etching of Silicon
    • Authors: Owen J. Hildreth; Daniel R. Schmidt
      Pages: 3827 - 3833
      Abstract: This work introduces and explores vapor phase metal‐assisted chemical etching (VP‐MaCE) of silicon as a method to bypass some of the challenges found in traditional liquid phase metal‐assisted chemical etching (LP‐MaCE). Average etch rates for Ag, Au, and Pd/Au catalysts are established at 31, 70, and 96 nm/min respectively, and the relationship between etch rate and substrate temperature is examined experimentally. Just as with LP‐MaCE, 3D catalyst motion is maintained and three‐dimensional structures are fabricated with nanoparticle‐ and lithography‐patterned catalysts. VP‐MaCE produces less microporous silicon compared with LP‐MaCE and the diffusion/reduction distance of Ag+ ions is significantly reduced. This process sacrifices etch rate for increased etch uniformity and lower stiction for applications in micro‐electromechanical systems (MEMS) processing. To overcome non‐uniformity and microporous silicon generation seen in traditional liquid‐phase metal‐assisted chemical etching, vapor‐phase metal‐assisted chemical etching (VP‐MaCE) is used instead. The etch rate is evaluated as a function of catalyst, time, and substrate temperature.
      PubDate: 2014-03-14T08:18:43.708281-05:
      DOI: 10.1002/adfm.201304129
  • Thermochromic Sensors: Construction and Molecular Understanding of an
           Unprecedented, Reversibly Thermochromic Bis‐Polydiacetylene (Adv.
           Funct. Mater. 24/2014)
    • Authors: Songyi Lee; Joonseong Lee, Minji Lee, Yu Kyung Cho, Junwoo Baek, Jinwook Kim, Sungnam Park, Myung Hwa Kim, Rakwoo Chang, Juyoung Yoon
      Pages: 3836 - 3836
      Abstract: A new type of bis‐polydiacetylene (PDA), in which two PDAs are linked via an intervening p‐phenylene group, displays excellent thermochromic reversibility. Clear blue‐to‐red and red‐to‐blue colorimetric transitions are observed by R. Chang, J. Yoon, and co‐workers between 20 and 120 °C. The first theoretical simulation of the new PDA is reported on page 3699, the results of which successfully explain the thermochromic reversibility phenomenon.
      PubDate: 2014-06-20T02:10:37.537225-05:
      DOI: 10.1002/adfm.201470161
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