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  Subjects -> CHEMISTRY (Total: 830 journals)
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    - CHEMISTRY (583 journals)
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CHEMISTRY (583 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 5)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 30)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 16)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 17)
ACS Macro Letters     Full-text available via subscription   (Followers: 20)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 24)
ACS Nano     Full-text available via subscription   (Followers: 210)
ACS Photonics     Full-text available via subscription   (Followers: 5)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 12)
Acta Chemica Iasi     Open Access  
Acta Chimica Sinica     Full-text available via subscription  
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: 7)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 11)
Advanced Functional Materials     Hybrid Journal   (Followers: 42)
Advanced Science Focus     Free   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 24)
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: 17)
Advances in Enzyme Research     Open Access  
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 13)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 14)
Advances in Nanoparticles     Open Access   (Followers: 11)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Science     Hybrid Journal   (Followers: 37)
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: 6)
African Journal of Chemical Education     Open Access   (Followers: 1)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 1)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
AMB Express     Open Access  
Ambix     Hybrid Journal   (Followers: 2)
American Journal of Applied Sciences     Open Access   (Followers: 31)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 95)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 20)
American Journal of Plant Physiology     Open Access   (Followers: 10)
American Mineralogist     Full-text available via subscription   (Followers: 8)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 21)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 151)
Annales UMCS, Chemia     Open Access   (Followers: 2)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
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: 6)
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)
Antiviral Chemistry and Chemotherapy     Full-text available via subscription  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 16)
Applied Surface Science     Hybrid Journal   (Followers: 22)
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     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 164)
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: 5)
Bioinspired Materials     Open Access  
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 31)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 25)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 16)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 3)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 14)
C - Journal of Carbon Research     Open Access  
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 5)
Canadian Mineralogist     Full-text available via subscription   (Followers: 2)
Carbohydrate Research     Hybrid Journal   (Followers: 11)
Carbon     Hybrid Journal   (Followers: 78)

        1 2 3 4 5 6 | Last

Journal Cover   Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [42 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  [1597 journals]
  • Ambient‐Dried Cellulose Nanofibril Aerogel Membranes with High
           Tensile Strength and Their Use for Aerosol Collection and Templates for
           Transparent, Flexible Devices
    • Authors: Matti S. Toivonen; Antti Kaskela, Orlando J. Rojas, Esko I. Kauppinen, Olli Ikkala
      Abstract: The application potential of cellulose nanofibril (CNF) aerogels has been hindered by the slow and costly freeze‐ or supercritical drying methods. Here, CNF aerogel membranes with attractive mechanical, optical, and gas transport properties are prepared in ambient conditions with a facile and scalable process. Aqueous CNF dispersions are vacuum‐filtered and solvent exchanged to 2‐propanol and further to octane, followed by ambient drying. The resulting CNF aerogel membranes are characterized by high transparency (>90% transmittance), stiffness (6 GPa Young's modulus, 10 GPa cm3 g−1 specific modulus), strength (97 MPa tensile strength, 161 MPa m3 kg−1 specific strength), mesoporosity (pore diameter 10–30 nm, 208 m2 g−1 specific surface area), and low density (≈0.6 g cm−3). They are gas permeable thus enabling collection of nanoparticles (for example, single‐walled carbon nanotubes, SWNT) from aerosols under pressure gradients. The membranes with deposited SWNT can be further compacted to transparent, conductive, and flexible conducting films (90% specular transmittance at 550 nm and 300 Ω ◻−1 sheet resistance with AuCl3‐salt doping). Overall, the developed aerogel membranes pave way toward use in gas filtration and transparent, flexible devices. Facile ambient preparation of cellulose nanofibril (CNF) aerogel membranes is presented. Their use in collection of single‐walled carbon nanotubes (SWNT) from a gas stream is demonstrated to prepare flexible, transparent, and conductive films. These results point a direction for scalable preparation of aerogels and demonstrate their potential for applications involving capturing aerosol particles and transparent, flexible electronics.
      PubDate: 2015-09-28T14:36:23.711699-05:
      DOI: 10.1002/adfm.201502566
  • Atomic Disorders Induced by Silver and Magnesium Ion Migrations Favor High
           Thermoelectric Performance in α‐MgAgSb‐Based Materials
    • Authors: Dandan Li; Huaizhou Zhao, Shanming Li, Beipei Wei, Jing Shuai, Chenglong Shi, Xuekui Xi, Peijie Sun, Sheng Meng, Lin Gu, Zhifeng Ren, Xiaolong Chen
      Abstract: Thermoelectric devices can directly convert thermal energy to electricity or vice versa with the efficiency being determined by the materials’ dimensionless figure of merit (ZT). Since the revival of interests in the last decades, substantial achievements have been reached in search of high‐performance thermoelectric materials, especially in the high temperature regime. In the near‐room‐temperature regime, MgAgSb‐based materials are recently obtained with ZT ≈ 0.9 at 300 K and ≈1.4 at 525 K, as well as a record high energy conversion efficiency of 8.5%. However, the underlying mechanism responsible for the performance in this family of materials has been poorly understood. Here, based on structure refinements, scanning transmission electron microscopy (STEM), NMR experiments, and density function theory (DFT) calculations, unique silver and magnesium ion migrations in α‐MgAg0.97Sb0.99 are disclosed. It is revealed that the local atomic disorders induced by concurrent ion migrations are the major origin of the low thermal conductivity and play an important role in the good ZT in MgAgSb‐based materials. The underlying mechanism responsible for the high thermoelectric performance in α‐MgAgSb‐based materials is disclosed. Based on density function theory calculations and experimental characterizations, concurrent silver and magnesium ion migrations are revealed in α‐MgAgSb. This is believed to be the origin of the low thermal conductivity in α‐MgAgSb‐based materials and plays an important role in the good figure of merit of these materials.
      PubDate: 2015-09-28T14:35:02.716164-05:
      DOI: 10.1002/adfm.201503022
  • The Mantis Shrimp Saddle: A Biological Spring Combining Stiffness and
    • Authors: Maryam Tadayon; Shahrouz Amini, Admir Masic, Ali Miserez
      Abstract: Stomatopods are aggressive crustacean predators that use a pair of ultrafast raptorial appendages to strike on prey. This swift movement is driven by a power amplification system comprising components that must be able to repetitively store and release a high amount of elastic energy. An essential component of this system is the saddle structure, in which the elastic energy is stored by bending prior to striking. Here, a comprehensive study that sheds light on the microstructural and chemical designs of the stomatopod's saddle is conducted. MicroCT scans combined with electron microscopy imaging, elemental mapping, high‐resolution confocal Raman microscopy, and nanomechanical mapping show that the saddle is a bilayer structure with sharp changes in chemical composition and mechanical properties between the layers. The outer layer is heavily mineralized whereas the inner layer contains a high content of chitin and proteins, leading to a spatial organization of phases which is optimized for load distribution during saddle bending. The mineralized outer layer sustains compressive stresses, whereas the inner biopolymeric layer provides tensile resistance. These findings reveal that the saddle chemical composition and microstructure have been spatially tuned to generate a stiff, yet flexible structure that is optimized for storage of elastic energy. Mantis shrimps deliver ultrafast strikes using a complex power amplification system, within which the “saddle biospring” is used to store and quickly release the elastic energy. It is demonstrated that the saddle is a bilayer material with distinct degrees of mineralization. One layer is used to maximize elastic energy storage during loading, while the other layer provides flexibility and prevents fracture.
      PubDate: 2015-09-24T10:04:12.865045-05:
      DOI: 10.1002/adfm.201502987
  • Rattle‐Type Fe3O4@CuS Developed to Conduct Magnetically Guided
           Photoinduced Hyperthermia at First and Second NIR Biological Windows
    • Abstract: A therapeutic carrier in the second near‐infrared (NIR) window is created that features magnetic target, magnetic resonance imaging (MRI) diagnosis, and photothermal therapy functions through the manipulation of a magnet and NIR laser. A covellite‐based CuS in the form of rattle‐type Fe3O4@CuS nanoparticles is developed to conduct photoinduced hyperthermia at 808 and 1064 nm of the first and second NIR windows, respectively. The Fe3O4@CuS nanoparticles exhibit broad NIR absorption from 700 to 1300 nm. The in vitro photothermal results show that the laser intensity obtained using 808 nm irradiation required a twofold increase in its magnitude to achieve the same damage in cells as that obtained using 1064 nm irradiation. Because of the favorable magnetic property of Fe3O4, magnetically guided photothermal tumor ablation is performed for assessing both laser exposures. According to the results under the fixed laser intensity and irradiation spot, exposure to 1064 nm completely removed tumors showing no signs of relapse. On the other hand, 808 nm irradiation leads to effective inhibition of growth that remained nearly unchanged for up to 30 d, but the tumors are not completely eliminated. In addition, MRI is performed to monitor rattle‐type Fe3O4@CuS localization in the tumor following magnetic attraction. An effective, near‐infrared (NIR)‐responsive rattle‐type Fe3O4@CuS nanoparticle is developed to conduct magnetically guided photothermal tumor ablation and magnetic resonance imaging diagnosis through magnetic targeting. Based on the broad NIR absorption from 700 to 1300 nm, photothermal tumor ablation is evaluated by radiation at 808 and 1064 nm of the first and second NIR windows, respectively.
      PubDate: 2015-09-24T09:57:43.504501-05:
      DOI: 10.1002/adfm.201503015
  • Electromechanics of Ferroelectric‐Like Behavior of LaAlO3 Thin Films
    • Abstract: Electromechanical coupling in complex oxide heterostructures opens new possibilities for the development of a broad range of novel electronic devices with enhanced functionality. In this article, the switchable hysteretic electro­mechanical behavior of crystalline epitaxial LaAlO3 (LAO) thin films associated with polarization induced by electrical and mechanical stimuli is investigated. The field–time‐dependent testing of the induced polarization states along with transport measurements and theoretical modeling suggests that the ferroelectric‐like response of the LAO thin films is mediated by the field‐induced ion migration in the bulk of the film. Comparative analysis of the dynamics of polarization reversal under the electrical field and mechanical stress applied via a tip of a scanning probe microscope demonstrates that both electrical and mechanical stimulus can be used to effectively control polarization at least at the submillisecond timescale. However, the mechanical writing is more localized than the electrical one. A combined electrical/mechanical approach for tuning the physical properties of oxide hetero­structures may potentially facilitate novel memory and logic devices, in which the data bits are written mechanically and read electrically. Electrically and mechanically induced ferroelectric‐like polar states are investigatedIn the ultrathin LaAlO3 films, using a combination of scanning probe microscope techniques. The ferroelectric‐like behavior is associated with the reorganization of oxygen vacancies between the two stable states, which can be controlled at the submillisecond timescale using either the electrical or the mechanical stimulus.
      PubDate: 2015-09-24T09:56:40.83602-05:0
      DOI: 10.1002/adfm.201502483
  • Zn(II)‐Protoporphyrin IX‐Based Photosensitizer‐Imprinted
           Au‐Nanoparticle‐Modified Electrodes for Photoelectrochemical
    • Abstract: The electropolymerization of thioaniline‐modified Au nanoparticles (NPs) on thioaniline monolayer‐functionalized electrodes in the presence of Zn(II)‐protoporphyrin IX yields bis aniline‐crosslinked Au NPs matrices that include molecular imprinted sites for binding the Zn(II)‐protoporphyrin IX photosensitizer. The binding of the photosensitizer yields photoelectrochemically active electrodes that produce anodic photocurrents in the presence of the electron donor benzohydroquinone. The efficient photocurrents formed in the presence of the imprinted electrode are attributed to the high‐affinity binding of the photosensitizer to the imprinted sites, Ka = 3.2 × 106 m−1, and to the effective transport of the photoejected electrons to the bulk electrode via the bridged Au NPs matrix. Similarly, a N,N′‐dialkyl‐4,4′‐bipyridinium‐modified Zn(II)‐protoporphyrin IX photosensitizer‐electron acceptor dyad is imprinted in the bis aniline‐crosslinked Au NPs matrix. The photocurrent generated by the imprinted matrix is approximately twofold higher as compared to the photocurrent generated by the Zn(II)‐protoporphyrin IX‐imprinted Au NPs matrix. The efficient photocurrents generated in the presence of the bipyridinium‐modified Zn(II)‐protoporphyrin IX‐imprinted matrix are attributed to the effective primary charge separation of the electron–hole species in the dyad structure, followed by the effective transport of the photoejected electrons to the electrode via the bis aniline‐crosslinked Au NPs matrix. The structural features of Zn(II)‐protoporphyrin IX or bipyridinium‐modified Zn(II)‐protoporphyrin IX are imprinted in electropolymerized bis aniline‐crosslinked Au nanoparticle matrices associated with electrodes. The concentration of the photosensitizers at the electrodes by means of the imprinted sites leads to effective charge separation resulting in intensified photocurrents.
      PubDate: 2015-09-24T09:56:00.162978-05:
      DOI: 10.1002/adfm.201502801
  • Bubble‐Decorated Honeycomb‐Like Graphene Film as Ultrahigh
           Sensitivity Pressure Sensors
    • Authors: Lizhi Sheng; Yuan Liang, Lili Jiang, Qian Wang, Tong Wei, Liangti Qu, Zhuangjun Fan
      Abstract: Recently, macroporous graphene monoliths (MGMs), with ultralow density and good electrical conductivity, have been considered as excellent pressure sensors due to their excellent elasticity with a rapid rate of recovery. However, MGMs can only exhibit good sensitivity when the strain is higher than 20%, which is undesirable for touch‐type pressure sensors, such as artificial skin. Here, an innovative method for the fabrication of freestanding flexible graphene film with bubbles decorated on honeycomb‐like network is demonstrated. Due to the switching effect depended on “point‐to‐point” and “point‐to‐face” contact modes, the graphene pressure sensor has an ultrahigh sensitivity of 161.6 kPa−1 at a strain less than 4%, several hundred times higher than most previously reported pressure sensors. Moreover, the graphene pressure sensor can monitor human motions such as finger bending and pulse with a very low operating voltage of 10 mV, which is sufficiently low to allow for powering by energy‐harvesting devices, such as triboelectric generators. Therefore, the high sensitivity, low operating voltage, long cycling life, and large‐scale fabrication of the pressure sensors make it a promising candidate for manufacturing low‐cost artificial skin. A flexible, bubble‐decorated, honeycomb‐like graphene film (BHGF) is fabricated by a low‐temperature heat treatment of graphene oxide film. The as‐prepared BHGF exhibits an ultrahigh sensitivity of 161.6 kPa−1 at a strain less than 4%, due to the switching effect depended on “point‐to‐point” and “point‐to‐face” contact modes.
      PubDate: 2015-09-23T12:53:45.897637-05:
      DOI: 10.1002/adfm.201502960
  • Understanding Polymorph Transformations in Core‐Chlorinated
           Naphthalene Diimides and their Impact on Thin‐Film Transistor
    • Abstract: Though charge transport is sensitive to subtle changes in the packing motifs of molecular semiconductors, research addressing how intermolecular packing influences electrical properties has largely been carried out on single‐crystals, as opposed to the more technologically relevant thin‐film transistors (TFTs). Here, independent and reversible access to the monoclinic and triclinic crystal structures of a core‐chlorinated naphthalene tetracarboxylic diimide (NTCDI‐1) is demonstrated in polycrystalline thin films via post‐deposition annealing. Time‐resolved measurements of these transitions via UV–visible spectroscopy and grazing‐incidence X‐ray diffraction indicate that the polymorphic transformations follow second‐order Avrami kinetics, suggestive of 2D growth after initial nucleation. Thin‐film transistors comprising triclinic NTCDI‐1 consistently outperform those comprising its monoclinic counterpart. This behavior contrasts that of single‐crystal transistors in which devices comprising monoclinic crystals are consistently superior to devices with triclinic crystals. This difference is attributed to more uniform in‐plane charge transport in polycrystalline thin films having the triclinic compared to the monoclinic polymorph. As the mobility of TFTs is a reflection of ensemble‐average charge transport across crystalline grains having different molecular orientations, this study suggests that among different polymorphs of a particular molecular semiconductor, those with smaller in‐plane anisotropy are more beneficial for efficient lateral charge transport in polycrystalline devices. Post‐deposition annealing enables reversible thin‐film structural rearrangement of a core‐chlorinated naphthalene tetracarboxylic diimide between two distinct polymorphs. In situ spectroscopy and grazing‐incidence X‐ray diffraction reveal the transformations to follow second‐order Avrami kinetics. Thin‐film transistor performance indicates in‐plane anisotropy to dominate charge transport, and implicates 2D π‐stacking to be more efficient for lateral charge transport than 1D π‐stacking in polycrystalline thin films.
      PubDate: 2015-09-23T12:50:40.84681-05:0
      DOI: 10.1002/adfm.201502412
  • Enhanced Intracellular Protein Transduction by Sequence Defined
           Tetra‐Oleoyl Oligoaminoamides Targeted for Cancer Therapy
    • Abstract: Intracellular protein delivery presents a novel promising prospect for cell biology research and cancer therapy. However, inefficient cellular uptake and lysosomal sequestration hinder productive protein delivery into the cytosol. Here, a library of 16 preselected sequence‐defined oligoaminoamide oligomers is evaluated for intracellular protein delivery. All oligomers, containing polyethylene glycol (PEG) for shielding and optionally folic acid as targeting ligand, manifest cellular internalization of disulfide‐conjugated enhanced green fluorescent protein (EGFP). However, only a PEGylated folate‐receptor targeted two‐arm oligomer (729) containing both arms terminally modified with two oleic acids shows persistent intracellular protein survival and nuclear import of nlsEGFP (which contains a nuclear localization sequence) in folate‐receptor‐positive KB carcinoma cells, validating both effective endolysosomal escape and following subcellular transport. Furthermore, using ribonuclease A as a therapeutic cargo protein, among the tested oligomers, the oleic acid modified targeted two‐arm oligomers exert the most significant tumor cell killing of KB tumor cells. An investigation of structure–activity relationship elucidates that the incorporated oleic acids play a vital role in the enhanced intracellular protein delivery, by promoting stable formation of 25–35 nm lipo‐oligomer protein nanoparticles and by membrane‐active characteristics facilitating intracellular cytosolic delivery. A PEGylated folate‐receptor targeted two‐arm oligomer containing both arms terminally modified with two oleic acids potently transduces nlsEGFP or RNase A into the cytosol, where nlsEGFP undergoes efficient delivery into the nucleus, and RNase A elicits most effective killing of folate‐receptor‐positive cancer cells.
      PubDate: 2015-09-23T12:49:35.775093-05:
      DOI: 10.1002/adfm.201503152
  • Self‐Recovering Triboelectric Nanogenerator as Active
           Multifunctional Sensors
    • Authors: Mingyuan Ma; Qingliang Liao, Guangjie Zhang, Zheng Zhang, Qijie Liang, Yue Zhang
      Abstract: A novel self‐recovering triboelectric nanogenerator (STENG) driven by airflow is designed as active multifunctional sensors. A spring is assembled into the STENG and enables the nanogenerator to have self‐recovering characteristic. The maximum output voltage and current of the STENG is about 251 V and 56 μA, respectively, corresponding to an output power of 3.1 mW. The STENG can act as an active multifunctional sensors that includes a humidity sensor, airflow rate sensor, and motion sensor. The STENG‐based humidity sensor has a wide detection range of 20%–100%, rapid response time of 18 ms, and recovery time of 80 ms. Besides, the STENG could be utilized in the application of security monitoring. This work expands practical applications of triboelectric nanogenerators as active sensors with advantages of simple fabrication and low cost. A novel self‐recovering triboelectric nanogenerator (STENG) is developed and serves as a multifunctional sensor. The STENG has self‐recovering and rollable characteristics due to the spring assembled into the nanogenerator. The output performance is extremely high. It can be utilized as self‐powered multifunctional sensors to detect humidity, airflow rate, and motion.
      PubDate: 2015-09-23T12:47:36.042032-05:
      DOI: 10.1002/adfm.201503180
  • Masthead: (Adv. Funct. Mater. 36/2015)
    • PubDate: 2015-09-21T11:09:52.458893-05:
      DOI: 10.1002/adfm.201570240
  • Unveiling the Mechanism of Water‐Triggered Diplex Transformation and
           Correlating the Changes in Structures and Separation Properties
    • Abstract: Recently, great attention has been devoted to the initial and final structures of single‐crystal to single‐crystal (SCSC) transformations and dissolution‐recrystallization structural transformations (DRSTs), whereas the isolation and characterization of crucial intermediates and the unequivocal mechanism of the dynamic conversion process receive comparatively little consideration. Herein, a CuII‐based porous coordination polymer (PCP), which possesses a Kagomé lattice, is solvothermally synthesized. Triggered by water, the 2D Kagomé lattice (PCP‐1) primarily undergoes a reversible SCSC transformation to a distorted Kagomé intermediate (PCP‐2), which is followed by a DRST process to form a 3D NbO framework (PCP‐3) in situ. To the best of our knowledge, this is the first demonstration of a mixed SCSC and DRST transformation process. Notably, the sequential transformations result in the formation of the intermediate and the final product, which could not be obtained by direct synthesis. Regarding the intermediate, we have characterized the transformation separately and propose a plausible mechanism. More interestingly, the adsorption isotherms of water, methanol, and ethanol for the activated materials are distinctly different from one another. PCP‐2′ can uptake all three vapors with different adsorption capacities; however, the 3D transformed material PCP‐3′ only significantly absorbs water, which is concomitant with an amorphous‐to‐crystalline transformation, leading to the selective extraction of water from alcohol. A water‐triggered diplex structural transformation is successfully implemented in porous coordination polymers (PCPs), the mechanism of which is definitely clarified by the isolated and characterized intermediate. More excitingly, thanks to its high‐efficiency separation of water from alcohol the final product has a myriad of potential applications in separation technology.
      PubDate: 2015-09-21T11:08:26.057577-05:
      DOI: 10.1002/adfm.201503154
  • 3D Printed Anatomical Nerve Regeneration Pathways
    • Authors: Blake N. Johnson; Karen Z. Lancaster, Gehua Zhen, Junyun He, Maneesh K. Gupta, Yong Lin Kong, Esteban A. Engel, Kellin D. Krick, Alex Ju, Fanben Meng, Lynn W. Enquist, Xiaofeng Jia, Michael C. McAlpine
      Abstract: A 3D printing methodology for the design, optimization, and fabrication of a custom nerve repair technology for the regeneration of complex peripheral nerve injuries containing bifurcating sensory and motor nerve pathways is introduced. The custom scaffolds are deterministically fabricated via a microextrusion printing principle using 3D models, which are reverse engineered from patient anatomies by 3D scanning. The bifurcating pathways are augmented with 3D printed biomimetic physical cues (microgrooves) and path‐specific biochemical cues (spatially controlled multicomponent gradients). In vitro studies reveal that 3D printed physical and biochemical cues provide axonal guidance and chemotractant/chemokinetic functionality. In vivo studies examining the regeneration of bifurcated injuries across a 10 mm complex nerve gap in rats showed that the 3D printed scaffolds achieved successful regeneration of complex nerve injuries, resulting in enhanced functional return of the regenerated nerve. This approach suggests the potential of 3D printing toward advancing tissue regeneration in terms of: (1) the customization of scaffold geometries to match inherent tissue anatomies; (2) the integration of biomanufacturing approaches with computational modeling for design, analysis, and optimization; and (3) the enhancement of device properties with spatially controlled physical and biochemical functionalities, all enabled by the same 3D printing process. An imaging‐coupled 3D printing methodology for the design, optimization, and fabrication of a customized nerve repair technology for complex injuries is presented. The custom scaffolds are deterministically fabricated via microextrusion printing, which enables the simultaneous incorporation of anatomical geometries, biomimetic physical cues, and spatially‐controlled biochemical gradients in a one‐pot 3D manufacturing approach.
      PubDate: 2015-09-18T06:50:06.866958-05:
      DOI: 10.1002/adfm.201501760
  • Learning from the Harvard Clean Energy Project: The Use of Neural Networks
           to Accelerate Materials Discovery
    • Abstract: Here, the employment of multilayer perceptrons, a type of artificial neural network, is proposed as part of a computational funneling procedure for high‐throughput organic materials design. Through the use of state of the art algorithms and a large amount of data extracted from the Harvard Clean Energy Project, it is demonstrated that these methods allow a great reduction in the fraction of the screening library that is actually calculated. Neural networks can reproduce the results of quantum‐chemical calculations with a large level of accuracy. The proposed approach allows to carry out large‐scale molecular screening projects with less computational time. This, in turn, allows for the exploration of increasingly large and diverse libraries. The utility of including neural networks as a highly accurate screening function is demonstrated for molecules from the Harvard Clean Energy Project. The neural network described can predict power conversion efficiencies of molecules with an error of 0.12%. By using this network as a screen for generated molecules, the scope of high‐throughput virtual screening is expanded by several orders of magnitude.
      PubDate: 2015-09-18T06:46:13.147687-05:
      DOI: 10.1002/adfm.201501919
  • Oriented Growth of Gold Nanowires on MoS2
    • Authors: Daisuke Kiriya; Yuzhi Zhou, Christopher Nelson, Mark Hettick, Surabhi Rao Madhvapathy, Kevin Chen, Peida Zhao, Mahmut Tosun, Andrew M. Minor, Daryl C. Chrzan, Ali Javey
      Abstract: Layered 2D materials serve as a new class of substrates for templated synthesis of various nanomaterials even with highly dissimilar crystal structures; thus overcoming the lattice constraints of conventional epitaxial processes. Here, molybdenum disulfide (MoS2) is used as a prototypical model substrate for oriented growth of in‐plane Au nanowires (NWs) despite the nearly 8% lattice mismatch between MoS2 and Au. Au NWs on the MoS2 surface are oriented along three symmetrically equivalent directions within the substrate arising from the strong Au–S binding that templates the oriented growth. The kinetics of the growth process are explored through experiments and modeling. Strong charge transfer is observed between Au NWs and MoS2, resulting in degenerate p‐doping of MoS2. Au nanowires (NWs) are laterally grown on a 2D material, molybdenum disulfide (MoS2) via treatment with AuCl3 solution. The Au NWs are oriented on the MoS2 surface with C3 symmetry, reflecting the surface of the MoS2 crystal plane. Analysis of the electrical characteristics indicates a surface charge transfer reaction between AuCl3 and MoS2, showing p‐type doping up to the degenerate limit.
      PubDate: 2015-09-16T10:29:47.452839-05:
      DOI: 10.1002/adfm.201502582
  • Electrochemical and Top‐Down 3D Ion‐Carving to Change Magnetic
    • Authors: Jian Zhu; Da Deng
      Abstract: It is challenging to develop new top‐down approaches to tailor particles into subnanometer size structures on a large scale to further reveal their structure‐dependent physicochemical properties. Here, we demonstrate a non‐conventional, electrochemical, 3D ion‐carving process to tailor particles into subscale flower‐like nanostructures at room temperature. The technology is based on the electrochemical insertion/extraction of lithium ions as a carving “knife” to carve the single‐crystalline particle precursor into higher‐order, flower‐like nanostructures with hexagonal nanopetals as the building units. Our study demonstrates that the morphology of the as‐carved, flower‐like nanostructures can be controlled by the electrochemical parameters, such as the current density and the number of cycles. Particularly interesting is that dramatically different magnetic properties can be achieved depending on the morphology through careful tuning by the electrochemical ion‐carving process. The as‐carved, flower‐like particles may find many important applications, including magnetic nanodevices. Our approach, in principle, is applicable to prepare various kinds of 3D‐structured materials with different compositions. Electrochemical ion‐carving is demonstrated as a nanomachining approach for the top‐down creation of highly‐ordered nanostructures from microparticle precursors, using Fe2O3 as a model. The battery‐derived flower‐like Fe2O3 nanostructures show interesting magnetic properties that are significantly different from the precursor Fe2O3 rhombohedra particles.
      PubDate: 2015-09-15T10:48:06.012733-05:
      DOI: 10.1002/adfm.201502916
  • Interconnected Graphene Networks with Uniform Geometry for Flexible
    • Authors: Miao Xiao; Tao Kong, Wei Wang, Qin Song, Dong Zhang, Qinqin Ma, Guosheng Cheng
      Abstract: Controllable construction of graphene into specific architectures at macroscopic scales is crucial for practical applications of graphene. An approach of macroscopic and conductive interconnected graphene networks with controllable patterns, pore, and skeleton sizes via chemical vapor deposition is reported here. Specifically, the pore and skeleton sizes of 3D controllable graphene (3D‐CG) architectures can be tuned from 10 to 50 μm and the orientation angles of building blocks can be designed as 45° and 90°. The electrical conductivity and density of 3D‐CGs are measured at 60–80 S cm−1 and ≈3.6 mg cm−3, respectively. The properties of 3D‐CGs as flexible conductors and supercapacitor electrodes are reported, to explore the potential application in wearable devices and energy store. An approach for the fabrication of macro­scopically interconnected graphene networks with controllable patterns, pore and skeleton sizes, via chemical vapor deposition based on lithographically fabricated Ni template, is reported Because of the well‐defined nature of photolithography, the obtained three dimensional interconnected graphene has great structure and geometry controllability with outstanding performances for flexible conductor and supercapacitor electrode.
      PubDate: 2015-09-15T10:47:52.016755-05:
      DOI: 10.1002/adfm.201502966
  • Large Multipurpose Exceptionally Conductive Polymer Sponges Obtained by
           Efficient Wet‐Chemical Metallization
    • Abstract: Exceptionally conductive (250 S cm−1), very fast electrically heatable, thermally insulating, antimicrobial 3D polymeric sponges with very low density (≈30 mg cm−3), superhydrophobicity, and high porosity, their method of preparation, and manifold examples for applications are presented here. The electrical heatability is reversible, reaching 90 °C with 4.4 W in about 19–20 s and cooling immediately on switching off the voltage. The sponges show high contact angles >150° against water on the sponge surface as well as inside the sponge. Water droplets injected into the sponges are ejected. A facile wet‐chemical method established for macroscopic melamine–formaldehyde sponges is the key for the thorough in‐depth surface metallization of the sponges. The coating thickness and uniformity depend on the metallization formulation, conditions of metallization, and the type of metal used. A scanning electron microscope is used for morphology characterization. A reduced metallization rate in air is highly critical for the in‐depth uniform coating of metals. The resulting metallized sponges could be highly interesting for heating as well as insulation devices in addition to oil/water separation membranes. Electrically heatable metallized 3D polymer sponges of macroscopic dimensions with exceptional conductivity (240 S cm−1), thermally insulating, and superhydrophobic properties are shown. The multipurpose sponges are prepared by in‐depth homogeneous wet metallization of melamine‐formaldehyde sponges.
      PubDate: 2015-09-15T10:45:25.336036-05:
      DOI: 10.1002/adfm.201502636
  • Simultaneous Improvement of Charge Generation and Extraction in Colloidal
           Quantum Dot Photovoltaics Through Optical Management
    • Abstract: Inverted structure heterojunction colloidal quantum dot (CQD) photovoltaic devices with an improved performance are developed using single‐step coated CQD active layers with a thickness of ≈60 nm. This improved performance is achieved by managing the device architecture to simultaneously enhance charge generation and extraction by raising optical absorption within the depletion region. The devices are composed of an ITO/PEDOT:PSS/PbS‐CQD/ZnO/Al structure, in which the p–n heterojunction is placed at the rear (i.e., opposite to the side of illumination) of the devices (denoted as R‐Cell). Sufficient optical generation is achieved at very low CQD layer thicknesses of 45–60 nm because of the constructive interference caused by the insertion of ZnO between the CQD and the Al electrode. The power conversion efficiency (PCE) of R‐Cells containing a thin CQD layers (≈60 nm) is much higher (≈6%) than that of conventional devices containing CQD layers with a thickness of ≈300 nm (PCE ≈4.5%). This optical management strategy provides a general guide to obtain the optimal trade‐off between generation and extraction in planar p–n junction solar cells. In terms of device engineering, all the layers in our R‐Cells are fabricated using single coating, which can lead to compatibility with high‐throughput processes. Rear‐junction colloidal quantum dot (CQD) photovoltaic devices with an improved performance are developed using single‐step coated thin CQD active layers (thickness of ≈60 nm). Charge generation and extraction in CQD photovoltaic devices are simultaneously improved through optical management of thin CQD active layers. Sufficient optical generation and efficient charge extraction afford a power conversion efficiency of ≈6%.
      PubDate: 2015-09-15T10:45:08.098081-05:
      DOI: 10.1002/adfm.201502664
  • Temperature‐Dependent Charge‐Carrier Dynamics in CH3NH3PbI3
           Perovskite Thin Films
    • Authors: Rebecca L. Milot; Giles E. Eperon, Henry J. Snaith, Michael B. Johnston, Laura M. Herz
      Abstract: The photoluminescence, transmittance, charge‐carrier recombination dynamics, mobility, and diffusion length of CH3NH3PbI3 are investigated in the temperature range from 8 to 370 K. Profound changes in the optoelectronic properties of this prototypical photovoltaic material are observed across the two structural phase transitions occurring at 160 and 310 K. Drude‐like terahertz photoconductivity spectra at all temperatures above 80 K suggest that charge localization effects are absent in this range. The monomolecular charge‐carrier recombination rate generally increases with rising temperature, indicating a mechanism dominated by ionized impurity mediated recombination. Deduced activation energies Ea associated with ionization are found to increase markedly from the room‐temperature tetragonal (Ea ≈ 20 meV) to the higher‐temperature cubic (Ea ≈ 200 meV) phase adopted above 310 K. Conversely, the bimolecular rate constant decreases with rising temperature as charge‐carrier mobility declines, while the Auger rate constant is highly phase specific, suggesting a strong dependence on electronic band structure. The charge‐carrier diffusion length gradually decreases with rising temperature from about 3 μm at −93 °C to 1.2 μm at 67 °C but remains well above the optical absorption depth in the visible spectrum. These results demonstrate that there are no fundamental obstacles to the operation of cells based on CH3NH3PbI3 under typical field conditions. The photoconductivity in CH3NH3PbI3 thin films is investigated from 8 to 370 K across three structural phases. Analysis of the charge‐carrier recombination dynamics reveals a variety of starkly differing recombination mechanisms. Evidence of charge‐carrier localization is observed only at low temperature. High charge mobility and diffusion length are maintained at high temperature beyond the tetragonal‐to‐cubic phase transition at ≈310 K.
      PubDate: 2015-09-15T10:44:56.670071-05:
      DOI: 10.1002/adfm.201502340
  • Angular‐Shaped 4,9‐Dialkyl α‐ and
           β‐Naphthodithiophene‐Based Donor–Acceptor
           Copolymers: Investigation of Isomeric Structural Effects on Molecular
           Properties and Performance of Field‐Effect Transistors and
    • Abstract: Two angular‐shaped 4,9‐didodecyl α‐aNDT and 4,9‐didodecyl β‐aNDT isomeric structures have been regiospecifically designed and synthesized. The distannylated α‐aNDT and β‐aNDT monomers are copolymerized with the Br‐DTNT monomer by the Stille coupling to furnish two isomeric copolymers, PαNDTDTNT and PβNDTDTNT, respectively. The geometric shape and coplanarity of the isomeric α‐aNDT and β‐aNDT segments in the polymers play a decisive role in determining their macroscopic device performance. Theoretical calculations show that PαNDTDTNT possesses more linear polymeric backbone and higher coplanarity than PβNDTDTNT. The less curved conjugated main chain facilitates stronger intermolecular π–π interactions, resulting in more redshifted absorption spectra of PαNDTDTNT in both solution and thin film compared to the PβNDTDTNT counterpart. 2D wide‐angle X‐ray diffraction analysis reveals that PαNDTDTNT has more ordered π‐stacking and lamellar stacking than PβNDTDTNT as a result of the lesser curvature of the PαNDTDTNT backbone. Consistently, PαNDTDTNT exhibits a greater field effect transistor hole mobility of 0.214 cm2 V−1 s−1 than PβNDTDTNT with a mobility of 0.038 cm2 V−1 s−1. More significantly, the solar cell device incorporating the PαNDTDTNT:PC71BM blend delivers a superior power conversion efficiency (PCE) of 8.01% that outperforms the PβNDTDTNT:PC71BM‐based device with a moderate PCE of 3.6%. Two new 4,9‐dialkyl α‐ and β‐naphthodithiophene‐based D‐A copolymers, PαNDTDTNT and PβNDTDTNT, are presented. With the better ordered structures in the solid state, PαNDTDTNT exhibits a greater field‐effect transistor hole mobility of 0.214 cm2 V−1 s−1 and a superior solar cell efficiency of 8.01% than PβNDTDTNT with a mobility of 0.038 cm2 V−1 s−1 and a PCE of 3.6%.
      PubDate: 2015-09-14T12:47:08.613096-05:
      DOI: 10.1002/adfm.201502338
  • Morphology Controlled Poly(aminophenylboronic acid) Nanostructures as
           Smart Substrates for Enhanced Capture and Release of Circulating Tumor
    • Abstract: A strategy is proposed to achieve an enhanced capture efficiency of and low damage to human leukemic lymphoblasts (CCRF‐CEM) by the synergistic effect of topographical interactions and phenylboronic acid functional groups on nanostructures. To realize this purpose, a simple and template free method to synthesize boronic acid derivative polyaniline bioinspired nanostructures with controlled morphology is established. Different nanostructured morphologies such as nanotexture, nanofibers, nanoparticles, microsphere, and 3D porous network have been prepared by controlling the nucleation and growth rate for polymerization. The phenylboronic acid functional groups on the surface of the nanostructures during poly­merization are used as artificial lectins to reversibly capture and release circulating tumor cells (CTCs) with little damage to the cells. The method presented here is simple, rapid, and highly efficient for CTC capture and release with low cost in materials and instruments. A synergistic effect of topographical interactions and surface chemistry of phenylboronic acid functional groups on nanostructures is proposed to achieve an enhanced capture efficiency of human leukemic lymphoblasts with reduced damage. Boronic acid derivative polyaniline bioinspired nanostructures with controlled morphology are prepared. The phenylboronic acid is used to reversibly capture and release circulating tumor cells.
      PubDate: 2015-09-14T12:46:51.983808-05:
      DOI: 10.1002/adfm.201502420
  • Hydrophobic Nanoreactor Soft‐Templating: A Supramolecular Approach
           to Yolk@Shell Materials
    • Abstract: Due to their unique morphology‐related properties, yolk@shell materials are promising materials for catalysis, drug delivery, energy conversion, and storage. Despite their proven potential, large‐scale applications are however limited due to demanding synthesis protocols. Overcoming these limitations, a simple soft‐templated approach for the one‐pot synthesis of yolk@shell nanocomposites and in particular of multicore metal nanoparticle@metal oxide nanostructures (MNP@MOx) is introduced. The approach here, as demonstrated for AuNP@ITOTR (ITOTR standing for tin‐rich ITO), relies on polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) inverse micelles as two compartment nanoreactor templates. While the hydrophilic P4VP core incorporates the hydrophilic metal precursor, the hydrophobic PS corona takes up the hydrophobic metal oxide precursor. As a result, interfacial reactions between the precursors can take place, leading to the formation of yolk@shell structures in solution. Once calcined these micelles yield AuNP@ITOTR nanostructures, composed of multiple 6 nm sized Au NPs strongly anchored onto the inner surface of porous 35 nm sized ITOTR hollow spheres. Although of multicore nature, only limited sintering of the metal nanoparticles is observed at high temperatures (700 °C). In addition, the as‐synthesized yolk@shell structures exhibit high and stable activity toward CO electrooxidation, thus demonstrating the applicability of our approach for the design of functional yolk@shell nanocatalysts. A facile strategy for the one‐pot synthesis of metal@metal oxide yolk@shell nanomaterials (M@MOx) is presented. As exemplified for gold nanoparticle@tin‐rich ITO yolk@shell nanostructures (Au@ITOTR), our approach takes advantage of gold precursor loaded inverse micelles as two compartment nanoreactor templates. Simple calcination of the precursor micelles yields highly defined Au@ITOTR nanostuctures in line with the micellar size and compositon featuring high activity and stability for electrocatalytic CO oxidation.
      PubDate: 2015-09-11T06:44:28.609061-05:
      DOI: 10.1002/adfm.201502388
  • Vertically Aligned WS2 Nanosheets for Water Splitting
    • Authors: Yang Yang; Huilong Fei, Gedeng Ruan, Yilun Li, James M. Tour
      Abstract: Vertically aligned WS2 (VAWS2) nanosheet films are prepared using a lithium based anodization electrolyte to fabricate WO3 films followed by sulfurization. The VAWS2 synthesized here is self‐organized as a conformal structure to expose active edge sites for water splitting. These vertically aligned nanosheets are composed of exfoliated WS2 to provide abundant active edges for catalytic reactions. Hydrogen evolution activity of the VAWS2 is demonstrated to show high catalytic current, low onset overpotential and small Tafel slope. By certain measures, this VAWS2 nanosheet film outperforms some of the state‐of‐the‐art hydrogen evolution reaction (HER) catalysts, which opens up a new pathway to simply and scalably fabricate high‐performance water electrolysis catalysts. Vertically aligned WS2 nanosheet films are fabricated in a simple process. The well‐exposed WS2 edges and interconnected porous structure give these materials excellent hydrogen evolution reaction activity and long‐term durability. The proposed fabrication technique also indicates that nanoengineering can be used to tailor the catalytic activity of layered transition‐metal dichalcogenides, which will open a new direction in designing efficient catalysts.
      PubDate: 2015-09-11T06:43:42.643018-05:
      DOI: 10.1002/adfm.201502479
  • Tuning Hydrogel Mechanics Using the Hofmeister Effect
    • Authors: Maarten Jaspers; Alan E. Rowan, Paul H. J. Kouwer
      Abstract: The mechanical properties of hydrogels are commonly modified by changing the concentration of the molecular components. This approach, however, does not only change hydrogel mechanics, but also the microstructure, which in turn alters the macroscopic properties of the gel. Here, the Hofmeister effect is used to change the thermoresponsiveness of polyisocyanide hydrogels. In contrast to previous Hofmeister studies, the effect is used to change the phase transition temperatures and to tailor the mechanics of the thermoresponsive (semiflexible) polymer gels. It is demonstrated that the gel stiffness can be manipulated over more than two orders of magnitude by the addition of salts. Surprisingly, the microstructure of the gels does not change upon salt addition, demonstrating that the Hofmeister effect provides an excellent route to change the mechanical properties without distorting other influential parameters of the gel. Salts are known to change the inter­actions between water and polymers and consequently change transition temperatures, an effect known as the Hofmeister effect. It is shown that beyond phase transition temperatures, ions can be used to tailor the linear and nonlinear mechanical behavior of hydrogels. A hundredfold stiffness increase is realized with gels of identical morphology.
      PubDate: 2015-09-11T06:42:12.62356-05:0
      DOI: 10.1002/adfm.201502241
  • Solid‐State Approach for Fabrication of Photostable,
           Oxygen‐Doped Carbon Nanotubes
    • Authors: Xuedan Ma; Jon K. S. Baldwin, Nicolai F. Hartmann, Stephen K. Doorn, Han Htoon
      Abstract: A novel procedure for effective fabrication of photostable oxygen‐doped single‐walled carbon nanotubes (SWCNTs) in solid‐state matrices has been developed. SWCNTs drop‐cast on various types of substrates are coated with oxide dielectric thin films by electron‐beam evaporation. Single tube photoluminescence spectroscopy studies performed at room and cryogenic temperatures reveal that such thin film‐coated tubes exhibit characteristic spectral features of oxygen‐doped SWCNTs, indicating the oxide thin film coating process leads to oxygen doping of the tubes. It is also found that the doping efficiency can be effectively controlled by the thin film deposition time and by the types of surfactants wrapping the SWCNTs. Moreover, aside from being the doping agent, the oxide thin film also serves as a passivation layer protecting the SWCNTs from the external environment. Comparing the thin film coated SWCNTs with oxygen‐doped tubes prepared via ozonolysis, the former exhibit significantly higher photostability and photoluminescence on‐time. Therefore, this one‐step deposition/oxygen‐doping procedure provides a possible route toward scalable, versatile incorporation of highly photostable oxygen‐doped SWCNTs in novel optical and optoelectronic devices. A novel procedure for effective fabrication of photostable oxygen‐doped single‐walled carbon nanotubes (SWCNTs) in solid‐state matrices by electron beam evaporation has been developed. The thin film doping efficiency can be effectively controlled by the deposition time and types of surfactants wrapping the SWCNTs. Oxygen‐doped tubes prepared by this procedure exhibit significantly higher photostability than those prepared via ozonolysis in aqueous phase.
      PubDate: 2015-09-11T06:40:22.967202-05:
      DOI: 10.1002/adfm.201502580
  • Supramolecular Chemistry in Molten Sulfur: Preorganization Effects Leading
           to Marked Enhancement of Carbon Nitride Photoelectrochemistry
    • Authors: Jingsan Xu; Shaowen Cao, Thomas Brenner, Xiaofei Yang, Jiaguo Yu, Markus Antonietti, Menny Shalom
      Abstract: Here, a new method for enhancing the photoelectrochemical properties of carbon nitride thin films by in situ supramolecular‐driven preorganization of phenyl‐contained monomers in molten sulfur is reported. A detailed analysis of the chemical and photophysical properties suggests that the molten sulfur can texture the growth and induce more effective integration of phenyl groups into the carbon nitride electrodes, resulting in extended light absorption alongside with improved conductivity and better charge transfer. Furthermore, photophysical measurements indicate the formation of sub‐bands in the optical bandgap which is beneficial for exciton splitting. Moreover, the new bands can mediate hole transfer to the electrolyte, thus improving the photooxidation activity. The utilization of high temperature solvent as the polymerization medium opens new opportunities for the significant improvement of carbon nitride films toward an efficient photoactive material for various applications. Enhanced photoelectrochemical activity of carbon nitride thin films is achieved by in situ supramolecular‐driven preorganization of phenyl‐contained monomers in molten sulfur. Textured growth and more effective integration of phenyl groups in the carbon nitride frameworks lead to extended light absorption alongside with increased conductivity and better charge transfer, and as a result remarkably improved photoelectrochemical currents are obtained.
      PubDate: 2015-09-11T06:39:58.823535-05:
      DOI: 10.1002/adfm.201502843
  • BN–Graphene Composites Generated by Covalent Cross‐Linking
           with Organic Linkers
    • Authors: Ram Kumar; K. Gopalakrishnan, Irshad Ahmad, C. N. R. Rao
      Abstract: Composites of boron nitride (BN) and carboxylated graphene are prepared for the first time using covalent cross‐linking employing the carbodiimide reaction. The BN1–xGx (x ≈ 0.25, 0.5, and 0.75) obtained are characterized using a variety of spectroscopic techniques and thermogravimetric analysis. The composites show composition‐dependent electrical resistivity, the resistivity decreasing with increase in graphene content. The composites exhibit microporosity and the x ≈ 0.75 composite especially exhibits satisfactory performance with high stability as an electrode in supercapacitors. The x ≈ 0.75 composite is also found to be a good electrocatalyst for the oxygen reduction reaction in fuel cells. Covalently cross‐linked composites of BN and graphene prepared using amide bond chemistry are characterized and their functional properties are investigated. BN1–xGx (x ≈ 0.25, 0.5, and 0.75) composites show tunable resistivity that is dependent on the composition. The composites are microporous and show satisfactory performance as supercapacitor electrodes and as catalysts in the oxygen reduction reaction.
      PubDate: 2015-09-10T12:48:35.728083-05:
      DOI: 10.1002/adfm.201502166
  • A Universal and Facile Approach for the Formation of a Protein Hydrogel
           for 3D Cell Encapsulation
    • Abstract: A universal and facile approach to modifying proteins so that they can rapidly form hydrogel upon mixing with crosslinkers is presented. The concept of it is to introduce maleimide, which is highly reactive with dithiol‐containing crosslinkers via thiol‐ene click chemistry, onto proteins. Bovine serum albumin (BSA) is used as a model protein due to its good stability and low cost. The results here show that a protein hydrogel can be readily formed by blending modified BSA and resilin‐related peptide crosslinker solutions at a proper ratio. The hydrogel exhibits good elasticity and tunable mechanical as well as biochemical properties. Moreover, it allows convenient 3D cell encapsulation and shows good biocompatibility. Muscle cells embedded in the hydrogel are promoted to spread by incorporating arginyl‐glycyl‐aspartic acid (RGD)‐containing peptide into the system, thus warranting a bright future of it in regenerative medicine. A universal and facile approach for the formation of a protein hydrogel is presented. The concept is to introduce maleimide, which is highly reactive with dithiol‐containing crosslinkers, onto proteins. Bovine serum albumin is used as a model protein and a resilin‐related peptide is used as the crosslinker. The fabricated hydrogel shows good biocompatibility and can promote cell spreading and growth by incorporating an RGD ligand.
      PubDate: 2015-09-10T12:48:26.513288-05:
      DOI: 10.1002/adfm.201502942
  • Hetero‐Nanonet Rechargeable Paper Batteries: Toward Ultrahigh Energy
           Density and Origami Foldability
    • Abstract: Forthcoming smart energy era is in strong pursuit of full‐fledged rechargeable power sources with reliable electrochemical performances and shape versatility. Here, as a naturally abundant/environmentally friendly cellulose‐mediated cell architecture strategy to address this challenging issue, a new class of hetero‐nanonet (HN) paper batteries based on 1D building blocks of cellulose nanofibrils (CNFs)/multiwall carbon nanotubes (MWNTs) is demonstrated. The HN paper batteries consist of CNF/MWNT‐intermingled heteronets embracing electrode active powders (CM electrodes) and microporous CNF separator membranes. The CNF/MWNT heteronet‐mediated material/structural uniqueness enables the construction of 3D bicontinuous electron/ion transport pathways in the CM electrodes, thus facilitating electrochemical reaction kinetics. Furthermore, the metallic current collectors‐free, CNF/MWNT heteronet architecture allows multiple stacking of CM electrodes in series, eventually leading to user‐tailored, ultrathick (i.e., high‐mass loading) electrodes far beyond those accessible with conventional battery technologies. Notably, the HN battery (multistacked LiNi0.5Mn1.5O4 (cathode)/multistacked graphite (anode)) provides exceptionally high‐energy density (=226 Wh kg−1 per cell at 400 W kg−1 per cell), which surpasses the target value (=200 Wh kg−1 at 400 W kg−1) of long‐range (=300 miles) electric vehicle batteries. In addition, the heteronet‐enabled mechanical compliance of CM electrodes, in combination with readily deformable CNF separators, allows the fabrication of paper crane batteries via origami folding technique. CNFs/CNTs‐based hetero‐nanonet paper batteries are presented as a 1D material‐mediated cell architecture strategy to enable ultrahigh energy density and shape versatility far beyond those achievable with conventional battery technologies. Owing to the 3D bicontinuous electron/ion transport pathways and exceptional mechanical compliance, the hetero‐nanonet paper batteries provide unprecedented improvements in the electrochemical reaction kinetics, energy density, and origami foldability.
      PubDate: 2015-09-10T06:32:04.276676-05:
      DOI: 10.1002/adfm.201502833
  • Liquid Crystal Enabled Early Stage Detection of Beta Amyloid Formation on
           Lipid Monolayers
    • Abstract: Liquid crystals (LCs) can serve as sensitive reporters of interfacial events, and this property has been used for sensing of synthetic or biological toxins. Here it is demonstrated that LCs can distinguish distinct molecular motifs and exhibit a specific response to beta‐sheet structures. That property is used to detect the formation of highly toxic protofibrils involved in neurodegenerative diseases, where it is crucial to develop methods that probe the early‐stage aggregation of amyloidogenic peptides in the vicinity of biological membranes. In the proposed method, the amyloid fibrils formed at the lipid–decorated LC interface can change the orientation of LCs and form elongated and branched structures that are amplified by the mesogenic medium; however, nonamyloidogenic peptides form ellipsoidal domains of tilted LCs. Moreover, a theoretical and computational analysis is used to reveal the underlying structure of the LC, thereby providing a detailed molecular‐level view of the interactions and mechanisms responsible for such motifs. The corresponding signatures can be detected at nanomolar concentrations of peptide by polarized light microscopy and much earlier than the ones that can be identified by fluorescence‐based techniques. As such, it offers the potential for early diagnoses of neurodegenerative diseases and for facile testing of inhibitors of amyloid formation. Liquid‐crystal‐based sensors exhibit unique responses to peptides that aggregate at membrane interfaces. β‐sheet forming peptides, such as human islet amyloid poly­peptide, aggregate into fibrils at lipid–decorated liquid crystal interfaces, giving rise to branch‐like structures. By contrast, rat islet amyloid polypeptide molecules, which possess α‐helical character, exhibit weak protein–lipid interactions and form circular domains.
      PubDate: 2015-09-09T02:58:26.755048-05:
      DOI: 10.1002/adfm.201502830
  • Trifunctional TiO2 Nanoparticles with Exposed {001} Facets as Additives in
           Cobalt‐Based Porphyrin‐Sensitized Solar Cells
    • Abstract: In this study, highly mesoporous TiO2 composite photoanodes composed of functional {001}‐faceted TiO2 nanoparticles (NPs) and commercially available 20 nm TiO2 NPs are employed in efficient porphyrin‐sensitized solar cells together with cobalt polypyridyl‐based mediators. Large TiO2 NPs (approximately 50 nm) with exposed {001} facets are prepared using a fast microwave‐assisted hydrothermal (FMAH) method. These unique composite photoanodes favorably mitigate the aggregation of porphyrin on the surface of TiO2 NPs and strongly facilitate the mass transport of cobalt‐polypyridyl‐based electrolytes in the mesoporous structure. Linear sweep voltammetry reveals that the transportation of Co(polypyridyl) redox is a diffusion‐controlled process, which is highly dependent on the porosity of TiO2 films. Electrochemical impedance spectroscopy confirms that the FMAH TiO2 NPs effectively suppress the interfacial charge recombination toward [Co(bpy)3]3+ because of their oxidative {001} facets. In an optimal condition of 40 wt% addition of FMAH TiO2 NPs in the final formula, the power conversion efficiency of the dye‐sensitized cells improves from 8.28% to 9.53% under AM1.5 (1 sun) conditions. A cost‐efficient TiO2 composite photoanode for YD2‐oC8 dye‐sensitized cells (DSCs) with a Co(polypyridyl) mediator is fabricated by blending exposed {001}‐faceted TiO2 nanoparticles (approximately 50 nm) with commercial 20 nm TiO2. This photoanode simultaneously overcomes sensitizer aggregation, interfacial recombination, and ionic diffusion in cobalt‐mediated, porphyrin‐sensitized DSCs.
      PubDate: 2015-09-09T02:47:45.471168-05:
      DOI: 10.1002/adfm.201501982
  • Magnetically Modulated Pot‐Like MnFe2O4 Micromotors: Nanoparticle
           Assembly Fabrication and their Capability for Direct Oil Removal
    • Authors: Fangzhi Mou; Deng Pan, Chuanrui Chen, Yirong Gao, Leilei Xu, Jianguo Guan
      Abstract: This work demonstrates a simple‐structured, low‐cost magnetically modulated micromotor of MnFe2O4 pot‐like hollow microparticles as well as its facile, versatile, and large‐scale growing‐bubble‐templated nanoparticle (NP) assembly fabrication approach. In this approach, the hydrophobic MnFe2O4@oleic acid NPs in an oil droplet of chloroform and hexane assembled into a dense NP shell layer due to the hydrophobic interactions between the NP surfaces. With the encapsulated oil continuously vaporizing into high‐pressured gas bubbles, the dense MnFe2O4 NP shell layer then bursts, forming an asymmetric pot‐like MnFe2O4 micromotor by creating a single hole in it. For the as‐developed simple pot‐like MnFe2O4 micromotor, the catalytically generated O2 molecules nucleate and grow into bubbles preferentially on the inner concave surface rather than on the outer convex surface, resulting in continuous ejection of O2 bubbles from the open hole to propel it. Dexterously integrating the high catalytic activity for H2O2 decomposition to produce O2 bubbles, excellent magnetic property with the instinctive surface hydrophobicity, the MnFe2O4 pot‐like micromotor not only can autonomously move in water media with both velocity and direction modulated by external magnetic field but also can directly serve for environmental oil removal without any further surface modification. The results here may inspire novel practical micromotors. Pot‐like MnFe2O4 micromotors are fabricated by a simple growing‐bubble‐templated nanoparticle assembly approach. These micromotors can be directly used for environmental oil remediation without any further surface modification besides the magnetically modulated self‐propulsion in aqueous media.
      PubDate: 2015-09-09T02:47:28.531762-05:
      DOI: 10.1002/adfm.201502835
  • Enhanced Electrochemical H2 Evolution by Few‐Layered Metallic
           WS2(1−x)Se2x Nanoribbons
    • Authors: Fengmei Wang; Jinshan Li, Feng Wang, Tofik Ahmed Shifa, Zhongzhou Cheng, Zhenxing Wang, Kai Xu, Xueying Zhan, Qisheng Wang, Yun Huang, Chao Jiang, Jun He
      Abstract: As an effective alternative to noble platinum electrocatalyst, earth abundant and inexpensive layered transition metal dichalcogenides (TMDs) are investigated for the hydrogen evolution reaction (HER). Compared with binary TMDs, the tunably composed ternary TMDs have hitherto received relatively little attention. Here, few‐layered ternary WS2(1−x)Se2x nanoribbons (NRs) with metallic 1T phases, much more catalytically active in HER, are prepared for the first time. The favorable ΔGHo introduced by the tensile region on the surface, along with the presence of local lattice distortions of the WS2(1−x)Se2x nanoribbons with metallic 1T phases, greatly promotes the HER process. These ternary NRs achieve the lowest overpotential of ≈0.17 V at 10 mA cm−2 and a Tafel slope of ≈68 mV dec−1 at a low catalyst loading (≈0.30 ± 0.02 mg cm−2). Notably, the long‐term durability suggests the potential of practical applications in acid electrolytes. The results here suggest that the ternary WS2(1−x)Se2x NRs with 1T phases are prominent alternatives to platinum‐based HER electrocatalysts. Few‐layered ternary WS2(1–x)Se2x nanoribbons (NRs) with metallic 1T phases are prepared. The favorable Gibbs free energy for hydrogen absorption (ΔGHo) of the WS2(1–x)Se2x NRs, introduced by the tensile region and local lattice distortions, greatly promotes the hydrogen evolution reaction (HER). The results suggest that the metallic WS2(1–x)Se2x NRs are potential alternatives for HER electrocatalysts.
      PubDate: 2015-09-09T02:47:15.353368-05:
      DOI: 10.1002/adfm.201502680
  • Gadolinium‐Doped Iron Oxide Nanoprobe as Multifunctional Bioimaging
           Agent and Drug Delivery System
    • Authors: Guilong Zhang; Ruohong Du, Lele Zhang, Dongqing Cai, Xiao Sun, Yong Zhou, Jian Zhou, Junchao Qian, Kai Zhong, Kang Zheng, Darnell Kaigler, Wenqing Liu, Xin Zhang, Duohong Zou, Zhengyan Wu
      Abstract: In this study, a high‐performance T1–T2 dual‐model contrast agent by gadolinium‐doped iron oxide nanoparticle (GION) is developed. Following its development, the application of this agent in vivo by combining doxorubicin (DOX) and folic acid (FA) (FA–GION–DOX) for targeted drug delivery to monitor cancer treatment is explored. GION showed transverse and longitudinal relaxivities up to 182.7 × 10−3 and 7.87 × 10−3m−1 s−1, respectively, upon Gd/Fe ratio in GION at 1/4. DOX released from FA–GION–DOX is pH dependent and only kills cancer cell after FA receptor‐mediated internalization into the acidic environment of endosomes and lysosomes. Systemic delivery of FA–GION–DOX significantly inhibits the growth of tumors and shows good magnetic resonance enhancement in a human cervical cancer xenograft model. Thus, FA–GION–DOX has a potential application for the targeted and magnetic resonance imaging guided therapy of cervical cancer. FA–GION–DOX is designed as high specific bioimaging agent and targeted drug delivery system. Systemic delivery of the FA–GION–DOX significantly inhibits the growth of tumors and shows good magnetic resonance enhancement in a human cervical cancer xenograft model, which makes FA–GION–DOX a good candidate for the targeted and MRI‐guided therapy of cervical cancer.
      PubDate: 2015-09-09T02:47:10.414341-05:
      DOI: 10.1002/adfm.201502868
  • On‐the‐Spot Immobilization of Quantum Dots, Graphene Oxide,
           and Proteins via Hydrophobins
    • Abstract: Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. Immobilization of optically active nanomaterials and proteins (particularly, cadmium telluride quantum dots, graphene oxide, antibodies, and bovine serum albumin) on glass is achieved using a Janus‐faced fungal protein, hydrophobin Vmh2, which is extracted from Pleurotus ostreatus. The proposed glass nanobiofunctionalization is fast, easily scalable, and environmental friendly, which is appealing for new bioanalytical and nanobioenabled applications.
      PubDate: 2015-09-09T02:46:28.724948-05:
      DOI: 10.1002/adfm.201502837
  • Direct Patterning of Self‐Assembled Monolayers by Stamp Printing
           Method and Applications in High Performance Organic Field‐Effect
           Transistors and Complementary Inverters
    • Authors: Zhichao Zhang; Xiaochen Ren, Boyu Peng, Zongrong Wang, Xinyu Wang, Ke Pei, Bowen Shan, Qian Miao, Paddy K. L. Chan
      Abstract: Self‐assembled monolayer (SAM) is usually applied to tune the interface between dielectric and active layer of organic field‐effect transistors (OFETs) and other organic electronics, a time‐saving, direct patterning approach of depositing well‐ordered SAMs is highly desired. Here, a new direct patterning method of SAMs by stamp printing or roller printing with special designed stamps is introduced. The chemical structures of the paraffin hydrocarbon molecules and the tail groups of SAMs have allowed to use their attractive van der Waals force for the direct patterning of SAMs. Different SAMs including alkyl and fluoroalkyl silanes or phosphonic acids are used to stamp onto different dielectric surfaces and are characterized by water contact angle, atomic force microscopy, X‐ray diffraction, and attenuated total reflectance Fourier transform infrared. The p‐type dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (DNTT) and n‐type F16CuPc OFETs show competitive mobility as high as 3 and 0.018 cm2 V−1 s−1, respectively. This stamp printing method also allows to deposit different SAMs on certain regions of same substrate, and the complementary inverter consists of both p‐type and n‐type transistors whose threshold voltages are tuned by stamp printing SAMs and shows a gain higher than 100. The proposed stamp or roller printing method can significantly reduce the deposition time and compatible with the roll‐to‐roll fabrication. A novel printing method to deposit self‐assembled monolayers (SAMs) on different substrates is introduced with the assistance of hydrocarbon molecules. By using this method, a crystallized SAM layer is formed and characterized, organic field‐effect transistors based on dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (DNTT) with mobility as high as 3.02 cm2 V−1 s−1 and complementary inverter with gain of 102 are fabricated.
      PubDate: 2015-09-09T02:45:49.142262-05:
      DOI: 10.1002/adfm.201503245
  • Probing Local Electronic Transitions in Organic Semiconductors through
           Energy‐Loss Spectrum Imaging in the Transmission Electron Microscope
    • Authors: Changhe Guo; Frances I. Allen, Youngmin Lee, Thinh P. Le, Chengyu Song, Jim Ciston, Andrew M. Minor, Enrique D. Gomez
      Abstract: Improving the performance of organic electronic devices depends on exploiting the complex nanostructures formed in the active layer. Current imaging methods based on transmission electron microscopy provide limited chemical sensitivity, and thus the application to materials with compositionally similar phases or complicated multicomponent systems is challenging. Here, it is demonstrated that monochromated transmission electron microscopes can generate contrast in organic thin films based on differences in the valence electronic structure at energy losses below 10 eV. In this energy range, electronic fingerprints corresponding to interband excitations in organic semiconductors can be utilized to generate significant spectral contrast between phases. Based on differences in chemical bonding of organic materials, high‐contrast images are thus obtained revealing the phase separation in polymer/fullerene mixtures. By applying principal component analysis to the spectroscopic image series, further details about phase compositions and local electronic transitions in the active layer of organic semiconductor mixtures can be explored. Monochromated transmission electron microscopes can generate contrast in organic thin films based on differences in the valence electronic structure at energy losses below 10 eV. By applying principal component analysis to the spectroscopic image series, further details about phase compositions and local electronic transitions in the active layer of organic semiconductor mixtures can be explored.
      PubDate: 2015-09-02T08:52:39.070969-05:
      DOI: 10.1002/adfm.201502090
  • In Situ Scanning Electron Microscopy Observation of Growth Kinetics and
           Catalyst Splitting in Vapor–Liquid–Solid Growth of Nanowires
    • Abstract: In situ observations during vapor–liquid–solid (VLS) growth of semiconductor nanowires in the chamber of an environmental scanning electron microscope (ESEM) are reported. For nanowire growth, a powder mixture of CdS and ZnS is used as a source material and silver nanoparticles as a metal catalyst. Through tracing growth kinetics of nanowires, it is found that nanowires with a relatively bigger catalyst droplet on the tip grow faster. Intriguingly, it is also found that the growth of nanowires can involve catalyst splitting: while the majority of catalyst remains at the nanowire tip and continues facilitating the growth, a portion of it is removed from the tip due to the splitting. It remains attached to the nanowire at the position where the splitting occurred and subsequently induces the growth of a nanowire branch. As far as it is known, this is the first time that catalyst splitting is revealed experimentally in situ. It is proposed that the instability of catalyst droplet caused by the volume increase is the main reason for the splitting. It is believed that in situ growth inside the ESEM can largely enrich our understanding on the metal‐catalyzed VLS growth kinetics, which may open up more opportunities for morphology‐controlled synthesis of 1D semiconductor nanowires in future study. Catalyst splitting in vapor–liquid–solid growth kinetics is observed during in situ growth of nanowires inside the chamber of a scanning electron microscope. The splitting occurs with the majority of catalyst remaining at the nanowire tip, further enabling nanowire growth, while the other portion remains attached to the nanowire and subsequently induces the growth of a nanowire branch.
      PubDate: 2015-09-01T14:32:13.706276-05:
      DOI: 10.1002/adfm.201502619
  • Inorganic Micelles (Hydrophilic Core@Amphiprotic Shell) for Multiple
    • Abstract: A facile approach for synthesizing superhydrophobic hollow silica micelles (SHSMs) with hydrophilic cores and amphiprotic (superhydrophobic/hydrophilic) shell structures that act as “all‐in‐one” smart nanomaterials is presented. The particles possess hydrophilic cores consisting of silica and a polyelectrolyte (PE) network and an amphiprotic shell consisting of superhydrophobic long‐chained hydrocarbons and hydrophilic PEs. Due to the unique hydrophilic cores and amphiprotic shells, the particles exhibit extraordinary performance in terms of amphiprotic catalytic reactions in organic and aqueous solutions, oil/water separation and pollutant purification, and an ultrahigh loading capacity of enzymes with significant stability and efficient recyclability. The amphiprotic functionalities of the SHSMs have the potential to allow for a rich range of applications to be explored. Superhydrophobic hollow SiO2 micelles (SHSMs) with hydrophilic cores and amphiprotic (superhydrophobic/hydrophilic) shells are prepared and their multiple applications are demonstrated. The unique amphiprotic functionality makes the SHSMs suitable as smart nanomaterials for multiple applications, such as amphiprotic catalytic reactions in aqueous or organic solutions, oil/water separation and pollutant purification, and enzyme immobilization, with great stability and efficient recyclability.
      PubDate: 2015-09-01T14:31:26.082078-05:
      DOI: 10.1002/adfm.201502693
  • Single Crystal‐Like Performance in Solution‐Coated
           Thin‐Film Organic Field‐Effect Transistors
    • Abstract: In electronics, the field‐effect transistor (FET) is a crucial cornerstone and successful integration of this semiconductor device into circuit applications requires stable and ideal electrical characteristics over a wide range of temperatures and environments. Solution processing, using printing or coating techniques, has been explored to manufacture organic field‐effect transistors (OFET) on flexible carriers, enabling radically novel electronics applications. Ideal electrical characteristics, in organic materials, are typically only found in single crystals. Tiresome growth and manipulation of these hamper practical production of flexible OFETs circuits. To date, neither devices nor any circuits, based on solution‐processed OFETs, has exhibited an ideal set of characteristics similar or better than today's FET technology based on amorphous silicon. Here, bar‐assisted meniscus shearing of dibenzo‐tetrathiafulvalene to coat‐process self‐organized crystalline organic semiconducting domains with high reproducibility is reported. Including these coatings as the channel in OFETs, electric field and temperature‐independent charge carrier mobility and no bias stress effects are observed. Furthermore, record‐high gain in OFET inverters and exceptional operational stability in both air and water are measured. Bar‐assisted meniscus shearing of dibenzo‐tetrathiafulvalene is used to coat‐process self‐organized crystalline organic semiconducting domains with high reproducibility for organic field‐effect transistors (OFETs). Electric field and temperature‐independent charge carrier mobility as well as no bias stress effects are observed in these devices. A record‐high gain in OFET inverters and exceptional operational stability in both air and water is demonstrated.
      PubDate: 2015-09-01T14:30:37.166498-05:
      DOI: 10.1002/adfm.201502274
  • Long Range Self‐Assembly of Polythiophene Breath Figures: Optical
           and Morphological Characterization
    • Authors: Prahlad K. Routh; Dmytro Nykypanchuk, T. A. Venkatesh, Mircea Cotlet
      Abstract: Large‐area, device relevant sized microporous thin films are formed with commercially available polythiophenes by the breath figure technique, a water‐assisted micropatterning method, with such semitransparent thin films exhibiting periodicity and uniformity dictated by the length of the polymer side chain. Compared to drop‐casted thin films, the microporous thin films exhibit increased crystallinity due to stronger packing of the polymer inside the honeycomb frame. Ordered microporous thin films of centimeter sized large area are successfully prepared from commercially available polythiophenes by using a breath figure technique. Structural and optical characterization of these thin films reveals increased crystallinity and ordered aggregates in the frame.
      PubDate: 2015-09-01T02:46:20.151223-05:
      DOI: 10.1002/adfm.201502463
  • Metal–Organic Polyhedra Cages Immobilized on a Plasmonic Substrate
           for Sensitive Detection of Trace Explosives
    • Abstract: A novel strategy for highly sensitive detection and discrimination of explosives is developed based on the metal–organic polyhedra (MOP)‐decorated plasmonic substrate. It is found that the careful selection of the geometric and electronic characteristics of the assembly units (organic ligands and unsaturated metals sites) embedded within the MOP cage allows for the integration of multiple weak molecular interactions in a controllable fashion and thus the MOP cage can serve as an excellent receptor for selective uptake and binding of explosives. By further grafting of the MOP cage onto a plasmonic substrate with good surface‐enhanced Raman scattering enhancement factor, the resulting sensor shows a good sensing capability to various groups of ultratrace explosives, especially the challenging aliphatic nitro‐organics. A novel strategy for highly sensitive detection and discrimination of explosives is developed based on a metal–organic polyhedra (MOP)‐decorated plasmonic substrate. MOP can serve as a receptor for selective uptake and binding of explosives. Grafting of the MOP onto a plasmonic substrate with good surface‐enhanced Raman scattering enhancement factor, the sensor shows excellent discrimination power toward explosives.
      PubDate: 2015-08-31T06:54:03.882075-05:
      DOI: 10.1002/adfm.201503071
  • Identification of Multiple Dityrosine Bonds in Materials Composed of the
           Drosophila Protein Ultrabithorax
    • Abstract: The recombinant protein Ultrabithorax (Ubx), a Drosophila melanogaster Hox transcription factor, self‐assembles in vitro into biocompatible materials that are remarkably extensible and strong. Here, it is demonstrated that the strength of Ubx materials is due to intermolecular dityrosine bonds. Ubx materials autofluoresce blue, a characteristic of dityrosine, and bind dityrosine‐specific antibodies. Monitoring the fluorescence of reduced Ubx fibers upon oxygen exposure reveals biphasic bond formation kinetics. Two dityrosine bonds in Ubx are identified by site‐directed mutagenesis followed by measurements of fiber fluorescence intensity. One bond is located between the N‐terminus and the homeodomain (Y4/Y296 or Y12/Y293), and another bond is formed by Y167 and Y240. Fiber fluorescence closely correlates with fiber strength, demonstrating that these bonds are intermolecular. This is the first identification of specific residues that participate in dityrosine bonds in protein‐based materials. The percentage of Ubx molecules harboring both bonds can be decreased or increased by mutagenesis, providing an additional mechanism to control the mechanical properties of Ubx materials. Duplication of tyrosine‐containing motifs in Ubx increases dityrosine content in Ubx fibers, suggesting these motifs could be inserted in other self‐assembling proteins to strengthen the corresponding materials. Amino acids that form dityrosine bonds in Ultrabithorax protein‐based materials are identified. Dityrosine content can be increased or decreased by mutagenesis, controlling the strength of the materials. These tyrosine‐containing motifs, inserted in other proteins, should increase the strength of the corresponding materials.
      PubDate: 2015-08-31T05:30:57.399011-05:
      DOI: 10.1002/adfm.201502852
  • Rapid and Controllable Digital Microfluidic Heating by Surface Acoustic
    • Authors: Richie J. Shilton; Virgilio Mattoli, Marco Travagliati, Matteo Agostini, Andrea Desii, Fabio Beltram, Marco Cecchini
      Abstract: Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Within typical operating conditions, the direct acoustic heating effect is shown to lead to a maximum temperature increase of about 10 °C in microliter water droplets. The importance of decoupling droplets from other on‐chip heating sources is demonstrated. Acoustic‐heating‐driven temperature changes reach a highly stable steady‐state value in ≈3 s, which is an order of magnitude faster than previously published. This rise time can even be reduced to ≈150 ms by suitably tailoring the applied SAW‐power excitation profile. Moreover, this fast heating mechanism can lead to significantly higher temperature changes (over 40 °C) with higher viscosity fluids and can be of much interest for on‐chip control of biological and/or chemical reactions. Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Small temperature changes in typical SAW microfluidic conditions and the possibility for rapid and controllable high temperature changes, for use with lab‐on‐a‐chip devices, are shown.
      PubDate: 2015-08-28T05:39:09.845137-05:
      DOI: 10.1002/adfm.201501130
  • Nucleus‐Targeting Gold Nanoclusters for Simultaneous In Vivo
           Fluorescence Imaging, Gene Delivery, and NIR‐Light Activated
           Photodynamic Therapy
    • Abstract: The nucleus is one of the most important cellular organelles and molecular anticancer drugs, such as cisplatin and doxorubicin, that target DNA inside the nucleus, are proving to be more effective at killing cancer cells than those targeting at cytoplasm. Nucleus‐targeting nanomaterials are very rare. It is a grand challenge to design highly efficient nucleus‐targeting multifunctional nanomaterials that are able to perform simultaneous bioimaging and therapy for the destruction of cancer cells. Here, unique nucleus‐targeting gold nanoclusters (TAT peptide–Au NCs) are designed to perform simultaneous in vitro and in vivo fluorescence imaging, gene delivery, and near‐infrared (NIR) light activated photodynamic therapy for effective cancer cell killing. Confocal laser scanning microscopy observations reveal that TAT peptide–Au NCs are distributed throughout the cytoplasm region with a significant fraction entering into the nucleus. The TAT peptide–Au NCs can also act as DNA nanocargoes to achieve very high gene transfection efficiencies (≈81%) in HeLa cells and in zebrafish. Furthermore, TAT peptide–Au NCs are also able to sensitize formation of singlet oxygen (1O2) without the co‐presence of organic photosensitizers for the destruction of cancer cells upon NIR light photoexcitation. A unique nucleus‐targeting gold nanocluster(TAT peptide–Au NC)‐based multifunctional theranostic platform is designed to perform simultaneous in vitro and in vivo cellular fluorescence imaging, gene delivery, and intrinsic near infrared light‐activated photodynamic therapy. This is done without the co‐presence of organic photosensitizers for the effective cancer cell killing.
      PubDate: 2015-08-28T05:38:59.80469-05:0
      DOI: 10.1002/adfm.201502650
  • Spiro Linkage as an Alternative Strategy for Promising Nonfullerene
           Acceptors in Organic Solar Cells
    • Abstract: This work focuses on developing diketopyrrolopyrrole (DPP)‐based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF‐DPPs, have an X‐shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro‐dimer of DPP‐fluorene‐DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2‐ethylhexyl (EH), linear n‐octyl (C8), and n‐dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N,N‐positions of the DPP moiety to tune molecular interactions. SF‐DPPEH, the best candidate in SF‐DPPs family, when blended with poly(3‐hexylthiophene) (P3HT) showed a moderate crystallinity and gives a Jsc of 6.96 mA cm−2, Voc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF‐DPPC8 and SF‐DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced Jsc. Coupling DPP units with SF using an acetylene bridge yields SF‐A‐DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors. A series of spiro‐diketopyrrolopyrroles‐based nonfullerene acceptors with X‐shape is developed. The substituted alkyl side chains on the acceptors can significantly tailor their crystallinity and bulk heterojunction film morphology. When paring these acceptors with poly(3‐hexylthiophene), a dramatic variation of power conversion efficiency from 1.42% to 3.63% is observed.
      PubDate: 2015-08-27T12:11:46.881222-05:
      DOI: 10.1002/adfm.201502413
  • A Fully Transparent and Flexible Ultraviolet–Visible Photodetector
           Based on Controlled Electrospun ZnO‐CdO Heterojunction Nanofiber
    • Authors: Zhi Zheng; Lin Gan, Huiqiao Li, Ying Ma, Yoshio Bando, Dmitri Golberg, Tianyou Zhai
      Abstract: It is essential for novel photodetectors to show good photoresponses, high stability, and have facile fabrication methods. Herein, an optimized electrospinning method to fabricate a photodetector based on nanowire arrays that has a wide spectral response range is demonstrated. Arrays of ZnO‐CdO hybrid nanowires are carefully fabricated fusing ZnO and CdO portions into the same nanowires and subsequently assembling those nanowires into a regular structure. Compared to pure ZnO or CdO nanowire arrays, the hybrid arrays show comparable photocurrent/dark current ratios and response speeds, but they possess a much wider spectral response range from ultraviolet to visible light. The optoelectronic and electronic properties of the ZnO‐CdO hybrid nanowire arrays are systematically explored. Based on this, a transparent and flexible photodetector made of ZnO‐CdO hybrid nanowire arrays is fabricated. It shows a high transparency of around 95% in the spectral range of 400–800 nm and maintains its properties even after 200 bending cycles. Importantly, the developed, simple method can be directly applied to many types of substrates and a transfer of the nanowires becomes unnecessary, which guarantees a high quality of the devices. A photodetector based on ZnO‐CdO heterojunctions with a large photoresponse range and a fast response speed is fabricated. Its comprehensive photoelectric and carrier transport properties at different wavelengths, light intensities, and pressures are investigated. The detector is highly transparent at 400–800 nm and maintains its properties even after 200 bending cycles. This photodetector has a high potential to be used in multicolor optoelectronic devices.
      PubDate: 2015-08-27T12:11:26.566722-05:
      DOI: 10.1002/adfm.201502499
  • Elastoplastic Inverse Opals as Power‐Free Mechanochromic Sensors for
           Force Recording
    • Authors: Younghyun Cho; Su Yeon Lee, Lindsay Ellerthorpe, Gang Feng, Gaojian Lin, Gaoxiang Wu, Jie Yin, Shu Yang
      Abstract: Light‐weight, power‐free mechanochromic sensors that can change and record the reflective color depending on the magnitude and rate of the applied force are fabricated from inverse opals by infiltrating the colloidal crystals of silica particles with uncrosslinked SU‐8, followed by removal of the colloidal templates. The mechanical sensing range of the materials is high, 17.6–20.4 MPa. Due to elastoplastic deformation of the SU‐8 films, the deformed structures and thus colors can be locked after the removal of the load, therefore establishing a quantitative relationship between the mechanical force and optical responses. In comparison, mechanochromic photonic gels reported in the literature typically detect force in the range of 10–100 kPa; once the load is removed, the structure and color return back to the original ones. The mechanochromic sensors are highly sensitive: the ratio of shift in the stopband wavelength to the change in applied strain is up to 5.7 nm per percent, the highest among literature. Comparison of finite element simulations with experiments confirms the elastoplastic deformation of the films and highlights that reconfiguration of pore shape under compression plays a key role in the mechanochromic response. Power‐free and highly sensitive mechanochromic sensors that can quantitatively measure the magnitude of mechanical force are prepared from uncrosslinked SU‐8 inverse opals. They can record impact forces by exhibiting different visible colors depending on the amount and rate of the applied forces. Experiments and finite element simulations attribute this to the elastoplastic deformation of the crystals.
      PubDate: 2015-08-26T09:36:19.264936-05:
      DOI: 10.1002/adfm.201502774
  • TiO2 Microspheres with Controllable Surface Area and Porosity for Enhanced
           Light Harvesting and Electrolyte Diffusion in Dye‐Sensitized Solar
    • Authors: Yong Ding; Li Zhou, Li'e Mo, Ling Jiang, Linhua Hu, Zhaoqian Li, Shuanghong Chen, Songyuan Dai
      Abstract: An optimized configuration of TiO2 microspheres in photoanodes is of great importance to prepare highly efficient dye‐sensitized solar cells (DSSCs). In this work, TiO2 microspheres with tunable diameter, pore size, and porosity are synthesized by subtly adjusting the synthesizing conditions, including ratios of deionized water, ammonia, and ethanol, respectively. TiO2 microspheres are obtained with large pore sizes and a high porosity without sacrificing specific surface areas. In addition, the effect of their porosity and pore size on the performance of DSSCs is investigated. As confirmed by the dye‐loading ability and electrolyte diffusion resistance, the large mesopores and the high porosity of the TiO2 microspheres can improve dye adsorption and facilitate electrolyte diffusion, giving rise to a high light‐harvesting and electron collection efficiency. Consequently, the highest photocurrent of 19.21 mA cm−2 and a power conversion efficiency of 9.98% are obtained by using the TiO2 microspheres with the highest porosity, compared with a 9.29% efficiency demonstrated by the lowest porosity (an improvement of 7.4%). By modifying the interconnection and the external pores of the microspheres photoanode, a high efficiency of 11.67% is achieved for a DSSC based on the most potent TiO2 microspheres. Mesoporous TiO2 microspheres with controllable diameter, pore size, and porosity are synthesized. The porosity of the microspheres can be easily tuned without sacrificing the specific surface area by adjusting the content of ethanol. The large porosity of microspheres shows an abundant dye adsorption, rapid dye regeneration, and sufficient electrolyte diffusion, resulting in a higher efficiency of 11.67%.
      PubDate: 2015-08-26T02:41:38.525776-05:
      DOI: 10.1002/adfm.201502224
  • Living Cells Directly Growing on a DNA/Mn3(PO4)2‐Immobilized and
           Vertically Aligned CNT Array as a Free‐Standing Hybrid Film for
           Highly Sensitive In Situ Detection of Released Superoxide Anions
    • Authors: Fang Xin Hu; Yue Jun Kang, Feng Du, Lin Zhu, Yu Hua Xue, Tao Chen, Li Ming Dai, Chang Ming Li
      Abstract: It is important to detect reactive oxygen species (ROS) in situ for investigation of various critical biological processes, and this is however very challenging because of the limited sensitivity or/and selectivity of existing methods that are mainly based on sensing ROS released by cells with short lifetimes and low concentrations in a culture medium. Here, a new approach is reported to directly grow living cells on DNA/Mn3(PO4)2‐immobilized and vertically aligned carbon nanotube (VACNT) array nanostructure as a smart free‐standing hybrid film, of which the DNA/Mn3(PO4)2 and VACNT provide high electroactivity and excellent electron transport, respectively, while the directly grown cell on the nanostructure offers short diffusion distance to reaction sites, thus constructing a highly sensitive in situ method for detection of cancer‐cell‐released ROS under drug stimulations. Compared to the measured ROS released by cells in a culture medium, the detection sensitivity with this constructed hybrid film increases by more than six times, which implies that ROS molecules (superoxide anions) secreted from living cells are immediately captured by this smart structure without diffusion process or with extremely short diffusion distance. This design considerably reduces the time from release to detection of the target molecules, minimizing the potential molecular decay due to the short lifetime or high reactivity. A DNA/Mn3(PO4)2‐immobilized and vertically aligned carbon nanotube (VACNT) array nanostructure is applied as a smart free‐standing hybrid film for directly growing living cells and investigating their electrochemical behaviors in response to drug stimulation. This holds a great promise for the fabrication of next‐generation biomedical devices for living cell assays, drug screening, and monitoring cell activity in situ.
      PubDate: 2015-08-25T08:37:52.127952-05:
      DOI: 10.1002/adfm.201502341
  • Recent Advances in Electrospun Nanofibrous Scaffolds for Cardiac Tissue
    • Authors: Guoxu Zhao; Xiaohui Zhang, Tian Jian Lu, Feng Xu
      Abstract: Cardiovascular diseases remain the leading cause of human mortality worldwide. Some severe symptoms, including myocardial infarction and heart failure, are difficult to heal spontaneously or under systematic treatment due to the limited regenerative capacity of the native myocardium. Cardiac tissue engineering has emerged as a practical strategy to culture functional cardiac tissues and relieve the disorder in myocardium when implanted. In cardiac tissue engineering, the design of a scaffold is closely relevant to the function of the regenerated cardiac tissues. Nanofibrous materials fabricated by electrospinning have been developed as desirable scaffolds for tissue engineering applications because of the biomimicking structure of protein fibers in native extra cellular matrix. The versatilities of electrospinning on the polymer component, the fiber structure, and the functionalization with bioactive molecules have made the fabrication of nanofibrous scaffolds with suitable mechanical strength and biological properties for cardiac tissue engineering feasible. Here, an overview of recent advances in various electrospun scaffolds for engineering cardiac tissues, including the design of advanced electrospun scaffolds and the performance of the scaffolds in functional cardiac tissue regeneration, is provided with the aim to offer guidance in the innovation of novel electrospun scaffolds and methods for improving their potential for cardiac tissue engineering applications. Electrospinning has shown great potential for cardiac tissue engineering applications, as a controllable and versatile technique for fabricating nanofibrous scaffolds. An overview of recent advances in various electrospun scaffolds for engineering functional cardiac tissues is provided, with emphasis on the fabrication of advanced electrospun scaffolds and design strategies to improve performance in cardiac tissue engineering applications.
      PubDate: 2015-08-21T07:06:09.381847-05:
      DOI: 10.1002/adfm.201502142
  • A Graphene‐Based Vacuum Transistor with a High ON/OFF Current Ratio
    • Authors: Gongtao Wu; Xianlong Wei, Zhiyong Zhang, Qing Chen, Lianmao Peng
      Abstract: A graphene‐based vacuum transistor (GVT) with a high ON/OFF current ratio is proposed and experimentally realized by employing electrically biased graphene as the electron emitter. The states of a GVT are switched by tuning the bias voltage applied to the graphene emitter with an ON/OFF current ratio up to 106, a subthreshold slope of 120 mV dec−1 and low working voltages of
      PubDate: 2015-08-21T07:03:57.30286-05:0
      DOI: 10.1002/adfm.201502034
  • Reversible Switching Phenomenon in Diarylethene Molecular Devices with
           Reduced Graphene Oxide Electrodes on Flexible Substrates
    • Abstract: Photoswitching molecular electronic devices with reduced graphene oxide (rGO) top electrodes on flexible substrates are fabricated and characterized. It has been reported previously that diarylethene molecular devices with poly‐(3,4‐ethylenedioxythiophene) stabilized with poly‐(4‐styrenesulfonic acid)/Au top electrodes can hold two stable electrical conductance states when the devices are exposed to UV or visible light during device fabrication. However, those devices fail to show the reversible switching phenomenon in response to illumination after device fabrication. By employing conducting and transparent rGO top electrodes, it is demonstrated that the diarylethene molecular devices show a reversible switching phenomenon, i.e., the fabricated devices change their conductance state in response to the alternating illumination with UV and visible light. Furthermore, the molecular devices with rGO top electrodes also exhibit good longtime stability and reliable electrical characteristics when subjected to various mechanical stresses (bending radius down to 5 mm and bending cycle over 104). The photoswitching characteristics of diarylethene molecular devices with reduced graphene oxide (rGO) electrodes on flexible substrates are studied. The diarylethene molecular devices with rGO electrodes can be converted from the open state to the closed state or vice versa with UV or visible light. The reversible photoswitching of these devices is successfully demonstrated with UV or visible light illumination.
      PubDate: 2015-08-21T07:03:48.952419-05:
      DOI: 10.1002/adfm.201502312
  • Magnetically Induced Fog Harvesting via Flexible Conical Arrays
    • Authors: Yun Peng; Yaxu He, Shuai Yang, Shuang Ben, Moyuan Cao, Kan Li, Kesong Liu, Lei Jiang
      Abstract: Water is the driving force of all nature. Securing freshwater has been one of the most important issues throughout human history, and will be important in the future, especially in the next decade. Fog is ubiquitous in nature and is therefore considered as an alternative and sustainable freshwater resource. Nature has long served as a source of inspiration to develop new fog‐harvesting technologies. However, the collection of freshwater from static fog is still a challenge for the existing bio‐inspired fog‐harvesting systems. Herein, magnetically induced fog harvesting under windless conditions through the integration of cactus‐inspired spine structures and magnetically responsive flexible conical arrays is reported. Under an external magnetic field, static fog can be spontaneously and continuously captured and transported from the tip to the base of the spine due to the Laplace pressure difference. This work demonstrates the advantage of collecting fog water, especially in windless regions, which provides a new avenue for fog harvesting and can serve as a source of inspiration to further optimizations of existing fog‐water‐harvesting strategies. A magnetically induced fog collector is fabricated through the integration of cactus‐inspired spine structures and magnetically responsive flexible conical arrays. Quasistatic fog water can be spontaneously and continuously captured and directionally transported, driven by the external magnetic field and the Laplace pressure difference. This work opens a new avenue for fog‐harvesting systems under windless conditions.
      PubDate: 2015-08-21T07:03:11.448167-05:
      DOI: 10.1002/adfm.201502745
  • High‐Efficiency Water‐Transport Channels using the Synergistic
           Effect of a Hydrophilic Polymer and Graphene Oxide Laminates
    • Authors: Kang Huang; Gongping Liu, Jie Shen, Zhenyu Chu, Haoli Zhou, Xuehong Gu, Wanqin Jin, Nanping Xu
      Abstract: Graphene oxide (GO) laminates possess unprecedented fast water‐transport channels. However, how to fully utilize these unique channels in order to maximize the separation properties of GO laminates remains a challenge. Here, a bio‐inspired membrane that couples an ultrathin surface water‐capturing polymeric layer (
      PubDate: 2015-08-19T10:07:17.944363-05:
      DOI: 10.1002/adfm.201502205
  • Unusual Circularly Polarized Photocatalytic Activity in Nanogapped
           Gold–Silver Chiroplasmonic Nanostructures
    • Authors: Changlong Hao; Liguang Xu, Wei Ma, Xiaoling Wu, Libing Wang, Hua Kuang, Chuanlai Xu
      Abstract: Gold‐gap‐silver nanostructures (GGS NSs) with interior nanobridged gaps are enantioselectively fabricated. Guided by l/d‐cysteine, the GGS‐L/D (L/D represents l/d‐cysteine) NSs show reversed plasmon‐induced circular dichroism (CD) signals in the visible region. It is found that the nanogap plays a key role in the plasmonic CD of GGS NSs and the chiroptical response can be tailored by adjusting the amount of cysteine. The anisotropy factor of GGS‐L/D NSs with a 0.5 nm interior gap at 430 nm is as high as ≈0.01. The circularly polarized photocatalytic activity of GGS NSs is examined. It is shown that upon irradiation with left‐circularly polarized light, the catalytic efficiency of GGS‐L NSs is 73‐fold and 17‐fold higher than that of Au nanoparticles (NPs) and Au@Ag core–shell NPs, respectively. Upon irradiation with right‐circularly polarized light, the catalytic activity of GGS‐D NSs is about 71 times and 17 times higher than that of Au NPs and Au@Ag core–shell NPs, respectively. These unique chiral NSs with high plasmonic response can be applied to enantioselective catalysis. Guided by l/d‐cysteine, gold‐gap‐silver nanostructures (GGS NSs) with interior nanogaps, which display exceptionally strong chiroptical activity in the visible light region, are prepared. Based on the fabricated GGS NSs, unexpected circularly polarized photocatalytic activity is discovered under the irradiation with circularly polarized light.
      PubDate: 2015-08-18T06:27:32.86164-05:0
      DOI: 10.1002/adfm.201502429
  • Rapid and Facile Formation of P3HT Organogels via Spin Coating: Tuning
           Functional Properties of Organic Electronic Thin Films
    • Authors: Cameron S. Lee; Wen Yin, Adam P. Holt, Joshua R. Sangoro, Alexei P. Sokolov, Mark D. Dadmun
      Abstract: Poly(3‐hexyl thiophene) (P3HT) is widely regarded as the benchmark polymer when studying the physics of conjugated polymers used in organic electronic devices. P3HT can self‐assemble via π–π stacking of its backbone, leading to an assembly and growth of P3HT fibrils into 3D percolating organogels. These structures are capable of bridging the electrodes, providing multiple pathways for charge transport throughout the active layer. Here, a novel set of conditions is identified and discussed for P3HT organogel network formation via spin coating by monitoring the spin‐coating process from various solvents. The development of organogel formation is detected by in situ static light scattering, which measures both the thinning rate by reflectance and structural development in the film via off‐specular scattering during film formation. Optical microscopy and thermal annealing experiments provide ex situ confirmation of organogel fabrication. The role of solution characteristics, including solvent boiling point, P3HT solubility, and initial P3HT solution concentration on organogel formation, is examined to correlate these parameters to the rate of film formation, organogel‐onset concentration, and overall network size. The correlation of film properties to the fabrication parameters is also analyzed within the context of the hole mobility and density‐of‐states measured by impedance spectroscopy. Poly(3‐hexylthiophene) organogels offer exploitable electronic properties. These gels agglomerate into 3D percolating networks that span the active layer of a thin‐film device. Novel spin‐coating conditions that produce organogels in a rapid deposition process are discussed, including the interplay of kinetics and solution thermodynamics in organogel formation, control of the network size, and the correlation of structure to electronic properties.
      PubDate: 2015-08-18T06:27:15.581639-05:
      DOI: 10.1002/adfm.201501707
  • Van der Waals p–n Junction Based on an Organic–Inorganic
    • Authors: Fucai Liu; Wai Leong Chow, Xuexia He, Peng Hu, Shoujun Zheng, Xingli Wang, Jiadong Zhou, Qundong Fu, Wei Fu, Peng Yu, Qingsheng Zeng, Hong Jin Fan, Beng Kang Tay, Christian Kloc, Zheng Liu
      Abstract: Organic–inorganic heterostructures are an emerging topic that is very interesting for optoelectronics. Here, non‐conventional p–n junctions are investigated using organic rubrene single crystal and 2D MoS2 as the p‐ and n‐type semiconducting materials, respectively. The current‐rectifying behavior is clearly observed in the junction device. The rectification ratio can be electrically tuned by the gate voltage due to the 2D nature of the heterostructure. The devices also show good photoresponse properties with a photoresponsivity of ≈500 mA W−1 and a fast response time. These findings suggest a new route to facilitate the design of nanoelectronic and optoelectronic devices based on layered inorganics and organics. Through the marriage of MoS2 and rubrene, a novel organic–inorganic van der Waals heterostructure is demonstrated with a gate‐tunable rectifying behavior. Good photoresponse properties are also obtained from the heterojunction with a photoresponsitivity of 500 A mW–1 and a fast response time.
      PubDate: 2015-08-18T06:26:12.276601-05:
      DOI: 10.1002/adfm.201502316
  • Modular and Versatile Spatial Functionalization of Tissue Engineering
    • Authors: Rachael H. Harrison; Joseph A. M. Steele, Robert Chapman, Adam J. Gormley, Lesley W. Chow, Muzamir M. Mahat, Lucia Podhorska, Robert G. Palgrave, David J. Payne, Shehan P. Hettiaratchy, Iain E. Dunlop, Molly M. Stevens
      Abstract: Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end‐functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly‐ε‐caprolactone is end functionalized with either a polymerization‐initiating group or a cell‐binding peptide motif cyclic Arg‐Gly‐Asp‐Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization‐initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin‐coupled moieties. These combined processing techniques result in an effective bilayered and dual‐functionality scaffold with a cell‐adhesive surface and an opposing antifouling non‐cell‐adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine. Cell‐adhesive and opposing antifouling surfaces are produced within a single construct for use in tissue engineering of biological interfaces. Different functional groups are zonally organized within a continuously electrospun scaffold before postprocessing modification with a versatile, surface‐initiated controlled radical polymerization production of an effective antifouling polymer bottlebrush in a predetermined, specific location.
      PubDate: 2015-08-17T11:12:05.924333-05:
      DOI: 10.1002/adfm.201501277
  • Peptide Length and Dopa Determine Iron‐Mediated Cohesion of Mussel
           Foot Proteins
    • Authors: Saurabh Das; Nadine R. Martinez Rodriguez, Wei Wei, J. Herbert Waite, Jacob N. Israelachvili
      Abstract: Mussel adhesion to mineral surfaces is widely attributed to 3,4‐dihydroxyphenylalanine (Dopa) functionalities in the mussel foot proteins (mfps). Several mfps, however, show a broad range (30%–100%) of tyrosine (Tyr) to Dopa conversion suggesting that Dopa is not the only desirable outcome for adhesion. Here, a partial recombinant construct of mussel foot protein‐1 (rmfp‐1) and short decapeptide dimers with and without Dopa are used and both their cohesive and adhesive properties on mica are assessed using a surface forces apparatus. Our results demonstrate that at low pH, both the unmodified and Dopa‐containing rmfp‐1s show similar energies for adhesion to mica and self–self‐interaction. Cohesion between two Dopa‐containing rmfp‐1 surfaces can be doubled by Fe3+ chelation, but remains unchanged with unmodified rmfp‐1. At the same low pH, the Dopa‐modified short decapeptide dimer did not show any change in cohesive interactions even with Fe3+. The results suggest that the most probable intermolecular interactions are those arising from electrostatic (i.e., cation–π) and hydrophobic interactions. It is also shown that Dopa in a peptide sequence does not by itself mediate Fe3+ bridging interactions between peptide films: peptide length is a crucial enabling factor. Fe3+‐mediated bridging of the mussel foot proteins (mfps) is attributed to two equally influential parameters: peptide architecture and 3,4‐dihydroxyphenyl­alanine (Dopa) residues in the protein. In addition, serial “hydrogen bonding” and cation–π interactions between the aromatic residues in the protein and a mineral surface are more probable than bidentate H‐bonding interactions in adhering mfps to the surface.
      PubDate: 2015-08-17T11:11:52.250315-05:
      DOI: 10.1002/adfm.201502256
  • A High‐Reliability Kevlar Fiber‐ZnO Nanowires Hybrid
           Nanogenerator and its Application on Self‐Powered UV Detection
    • Authors: Lu Zhang; Suo Bai, Chen Su, Youbin Zheng, Yong Qin, Chen Xu, Zhong Lin Wang
      Abstract: A microfiber‐nanowire hybrid structure is the fundamental component for a wearable piezoelectric nanogenerator (PENG) for harvesting body motion energy. Here, a novel approach combining surface coating and plasma etching techniques is reported to enhance the mechanical reliability of Kevlar microfiber‐ZnO nanowires (NWs) hybrid structure that is used for PENG. After treatment, the hybrid structure has dramatically improved high flexibility, robustness, and durability. On the basis of the coupled piezoelectric and semiconducting properties of ZnO, the processed Kevlar fibers covered with ZnO NWs are utilized to fabricate a 2D nanogenerator (2DNG). The open‐circuit voltage and short‐circuit current of the 2DNG are 1.8 mV and 4.8 pA, respectively. Furthermore, the 2DNG is successfully employed to quantitatively detect UV intensity from 0.2 to 1 mW cm−2 as a self‐powered system. A novel approach to combining surface coating and plasma etching techniques is introduced to enhance the mechanical reliability of Kevlar microfiber‐ZnO nano­wires hybrid structure. This is successfully applied to fabricate a high‐reliability Kevlar fiber‐ZnO nanowire hybrid nanogenerator. The nanogenerator can act as a self‐powered system to detect the UV intensity quantitatively.
      PubDate: 2015-08-17T11:08:20.593913-05:
      DOI: 10.1002/adfm.201502646
  • Polyazines and Polyazomethines with Didodecylthiophene Units for Selective
           Dispersion of Semiconducting Single‐Walled Carbon Nanotubes
    • Authors: Widianta Gomulya; Vladimir Derenskyi, Erika Kozma, Mariacecilia Pasini, Maria Antonietta Loi
      Abstract: Polymer wrapped single‐walled carbon nanotubes (SWNTs) have been demonstrated to be a very efficient technique to obtain high purity semiconducting SWNT solutions. However, the extraction yield of this technique is low compared to other techniques. Poly‐alkyl‐thiophenes have been reported to show higher extraction yield compare to polyfluorene derivatives. Here, the affinity for semiconducting SWNTs of two polymers with a backbone containing didodecylthiophene units interspersed with N atoms is reported. It is demonstrated that one of the polymers, namely, poly(2,5‐dimethylidynenitrilo‐3,4‐didodecylthienylene) (PAMDD), has very high semiconducting SWNT extraction yield compared to the poly(3,4‐didodecylthienylene)azine (PAZDD). The dissimilar wrapping efficiency of these two polymers for semiconducting SWNTs is attributed to the interplay between the affinity for the nitrogen atoms of the highly polarizable walls of SWNTs and the mechanical flexibility of the polymer backbones. Photoluminescence (PL) measurements demonstrate the presence of metallic tubes and SWNT bundles in the sample selected with PAZDD and higher purity of SWNT‐PAMDD samples. The high purity of the semiconducting SWNTs selected by PAMDD is further demonstrated by the high performance of the solution‐processed field‐effect transistors (FETs) fabricated using a blade coating technique, which exhibit hole mobilities up to 33.3 cm2 V−1 s−1 with on/off ratios of 106. A single‐wall carbon nanotube (SWNT) selective dispersion is obtained using polyazines and polyazomethines. Both polymers have didodecylthiophene units with direct nitrogen atoms in their backbone. The additional benzene ring in polyazomethines, which results in a stiffer polymer backbone, triggers different interaction with SWNTs. The high extraction yield of the SWNT dispersion by polyazomethines is essential for large‐scale separation of SWNT.
      PubDate: 2015-08-17T10:59:16.251924-05:
      DOI: 10.1002/adfm.201502912
  • Revisiting Metal Sulfide Semiconductors: A Solution‐Based General
           Protocol for Thin Film Formation, Hall Effect Measurement, and Application
    • Abstract: Nanostructured thin films of metal sulfides (MS) are highly desirable materials for various optoelectronic device applications. However, a general low‐temperature protocol that describes deposition of varieties of MS structures, especially in their film form is still not available in literatures. Here, a simple and highly effective general solution‐based deposition protocol for highly crystalline and well‐defined nanostructured MS thin films from ethanol on variety of conducting and non‐conducting substrates is presented. The films display remarkable electronic properties such as high carrier mobility and high conductivity. When NiS thin film deposited on a flexible polyethylene terephthalate (PET) substrate is used as a fluorine doped tin oxide (FTO)‐free counter electrode in dye‐sensitized solar cells, it exhibits a solar‐to‐electric power conversion efficiency of 9.27 ± 0.26% with the highest conversion efficiency as high as 9.50% (vs 8.97 ± 0.07% exhibited by Pt‐electrode). In addition, the NiS film deposited on a Ti‐foil has demonstrated an outstanding catalytic activity for the hydrogen and oxygen evolution reactions from water. A solution‐based general protocol for the deposition of large varieties of metal sulfide thin films from an ethanol bath on a variety of conducting and non‐conducting substrates is presented. As a proof‐of‐concept for application, a NiS film is investigated as an example, and it is demonstrated to be an outstanding electrocatalytic counter electrode for triiodide reduction in dye‐sensitized solar cells. It also exhibits potentially good electrocatalyst activity for the hydrogen evolution reaction and oxygen evolution reaction from water.
      PubDate: 2015-08-14T08:28:04.800969-05:
      DOI: 10.1002/adfm.201500964
  • Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches:
           Synthesis and Application for Efficient Oxygen Reduction
    • Authors: Jing Wei; Yaoxin Hu, Yan Liang, Biao Kong, Jin Zhang, Jingchao Song, Qiaoliang Bao, George P. Simon, San Ping Jiang, Huanting Wang
      Abstract: A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m2 g−1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm−2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐Nx/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐Nx/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media. A zeolitic‐imidazolate‐framework nanocrystal layer‐protected carbonization route is developed to prepare N‐doped carbon/graphene nano‐sandwiches. These act as a highly active and stable nonprecious metal catalyst for oxygen reduction.
      PubDate: 2015-08-13T13:36:32.631755-05:
      DOI: 10.1002/adfm.201502311
  • Induction of Potent Antitumor Immunity by Sustained Release of Cationic
           Antigen from a DNA‐Based Hydrogel with Adjuvant Activity
    • Authors: Yuka Umeki; Kohta Mohri, Yohji Kawasaki, Hiroshi Watanabe, Rei Takahashi, Yuki Takahashi, Yoshinobu Takakura, Makiya Nishikawa
      Abstract: Previous studies indicate that immunostimulatory DNA‐based injectable hydrogels harboring unmethylated cytosine‐phosphate‐guanine (CpG) dinucleotides meet the requirements of an effective antigen delivery system, including safety, biodegradability, ease of administration, and stimulation of the innate immune system. However, rapid release of the model antigen ovalbumin (OVA) from the hydrogel limits its potential. Here, the aim is to achieve sustained OVA release from a DNA hydrogel through cationization of the antigen. Ethylenediamine (ED)‐conjugated cationized OVA (ED‐OVA), but not OVA, forms a complex with hexapod‐like structured DNA, a component of the DNA hydrogel. The release of ED‐OVA from the hydrogel is significantly slower than that of OVA. ED‐OVA mixed with CpG DNA hydrogel efficiently binds to mouse dendritic DC2.4 cells and results in high antigen presentation. Intratumoral injections of ED‐OVA/CpG DNA hydrogel significantly delays tumor growth of OVA‐expressing EG7‐OVA cells in mice. Then, a cationic OVA peptide antigen (R8‐L2‐pepI) consisting of an OVA MHC class I epitope, octaarginine, and a linker is designed. Intratumoral injections of R8‐L2‐pepI/CpG DNA hydrogel eradicate tumors in five out of six mice. Thus, it is concluded that a vaccine consisting of immunostimulatory CpG DNA hydrogel and cationized antigens can be effective for cancer immunotherapy. An immunostimulatory DNA hydrogel‐based sustained release system using cationized antigen that can electrostatically interact with DNA is developed. This system can induce antigen‐specific immune responses, which leads to effective inhibition of antigen‐positive tumor growth in mice. This provides experimental evidence for future clinical applications of this system to induce potent antitumor immunity.
      PubDate: 2015-08-13T13:36:26.131562-05:
      DOI: 10.1002/adfm.201502139
  • Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as
           Multifunctional Electrocatalysts
    • Authors: Xien Liu; Wen Liu, Minseong Ko, Minjoon Park, Min Gyu Kim, Pilgun Oh, Sujong Chae, Suhyeon Park, Anix Casimir, Gang Wu, Jaephil Cho
      Abstract: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) along with hydrogen evolution reaction (HER) have been considered critical processes for electrochemical energy conversion and storage through metal‐air battery, fuel cell, and water electrolyzer technologies. Here, a new class of multifunctional electrocatalysts consisting of dominant metallic Ni or Co with small fraction of their oxides anchored onto nitrogen‐doped reduced graphene oxide (rGO) including Co‐CoO/N‐rGO and Ni‐NiO/N‐rGO are prepared via a pyrolysis of graphene oxide and cobalt or nickel salts. Ni‐NiO/N‐rGO shows the higher electrocatalytic activity for the OER in 0.1 m KOH with a low overpotential of 0.24 V at a current density of 10 mA cm−2, which is superior to that of the commercial IrO2. In addition, it exhibits remarkable activity for the HER, demonstrating a low overpotential of 0.16 V at a current density of 20 mA cm−2 in 1.0 m KOH. Apart from similar HER activity to the Ni‐based catalyst, Co‐CoO/N‐rGO displays the higher activity for the ORR, comparable to Pt/C in zinc‐air batteries. This work provides a new avenue for the development of multifunctional electrocatalysts with optimal catalytic activity by varying transition metals (Ni or Co) for these highly demanded electrochemical energy technologies. A new class of multifunctional electrocatalysts composed of Co‐CoO/N‐rGO and Ni‐NiO/N‐rGO, via a pyrolysis of graphene oxide and cobalt or nickel salts is synthesized. The two catalysts show excellent activities for oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), or oxygen evolution reaction (OER). In particularly, Co‐CoO/N‐rGO shows comparable performance to Pt/C in zinc‐air batteries.
      PubDate: 2015-08-13T13:36:19.105644-05:
      DOI: 10.1002/adfm.201502217
  • A High‐Power Symmetric Na‐Ion Pseudocapacitor
    • Abstract: Batteries and supercapacitors are critical devices for electrical energy storage with wide applications from portable electronics to transportation and grid. However, rechargeable batteries are typically limited in power density, while supercapacitors suffer low energy density. Here, a novel symmetric Na‐ion pseudocapacitor with a power density exceeding 5.4 kW kg−1 at 11.7 A g−1, a cycling life retention of 64.5% after 10 000 cycles at 1.17 A g−1, and an energy density of 26 Wh kg−1 at 0.585 A g−1 is reported. Such a device operates on redox reactions occurring on both electrodes with an identical active material, viz., Na3V2(PO4)3 encapsulated inside nanoporous carbon. This device, in a full‐cell scale utilizing highly reversible and high‐rate Na‐ion intercalational pseudocapacitance, can bridge the performance gap between batteries and supercapacitors. The characteristics of the device and the potentially low‐cost production make it attractive for hybrid electric vehicles and low‐maintenance energy storage systems. A novel symmetric Na‐ion pseudocapacitor that operates on oxidation–reduction reactions occurring on both electrodes with an identical active material, viz., Na3V2(PO4)3 encapsulated inside nano­porous carbon, is designed. When used in a full‐cell utilizing highly reversible, high‐rate, and cost‐effective Na‐ion intercalational pseudocapacitance, this device can bridge the performance gap between batteries and supercapacitors.
      PubDate: 2015-08-13T13:36:13.843856-05:
      DOI: 10.1002/adfm.201502433
  • pH‐Responsive Round‐Way Motions of a Smart Device through
           Integrating Two Types of Chemical Actuators in One Smart System
    • Authors: Lingling Yu; Mengjiao Cheng, Mengmeng Song, Dequn Zhang, Meng Xiao, Feng Shi
      Abstract: Smart motions of objects from the submicrometer to millimeter scale through chemical control with stimulus‐responsive way are significant to achieve various applications. However, the intelligence of the current devices with chemical responding system remains to be improved; especially, achieving a round‐way motion is still a challenge. Therefore, two types of actuators are simultaneously integrated into single smart device at the opposite ends to achieve cooperated functions in an orderly manner. One actuator is the pH‐responsive power supply of hydrogen bubbles produced from the reaction between magnesium and HCl. The smart device undergoes on–off–on locomotion through control over the solution pH values by using the pH‐responsive actuator of magnesium–HCl system. The other actuator is the hydrogen peroxide‐responsive system of oxygen bubbles generated through the decomposition of hydrogen peroxide catalyzed by platinum aggregates. When introducing hydrogen peroxide solution into the system, the generated oxygen bubbles at the opposite end of the device to push the device backward for round‐way motions. For the first time, two different types of actuators are simultaneously integrated into single smart device without disturbing each other, which realize pH‐responsive round‐way motions of the smart device and improve the system intelligence for further applications. To improve the intelligence of smart devices and realize round‐way smart motions, a smart device is fabricated with two types of actuators of magnesium–acid system and platinum‐hydrogen‐peroxide system at the opposite ends. Under acidic conditions, the magnesium reacts with acid to propel the device forward; changing to alkaline, the device stops motion; adding hydrogen peroxide, it moves back.
      PubDate: 2015-08-13T13:35:18.531003-05:
      DOI: 10.1002/adfm.201502447
  • A Multiple‐Functional Ag/SiO2/Organic Based Biomimetic Nanocomposite
           Membrane for High‐Stability Protein Recognition and Cell
    • Authors: Yilin Wu; Ming Yan, Jiuyun Cui, Yongsheng Yan, Chunxiang Li
      Abstract: Biomimetic multilevel structured membrane materials have great potential for energy‐efficient chemical separations and biomedical applications. The current study represents a simple, yet efficient, method to obtain the biomimetic protein separation membrane and controllable cell culture substrate with high stability, selectivity, and antibacterial property. Here, a molecular imprinting methodology is reported to introduce the high‐biocompatible protein ovalbumin (Ova) to a multilevel Ag/SiO2/organic based molecularly imprinted membranes (ASO‐MIMs), which have made significant achievements in protein identification and controllable growth of liver cells in vitro platform. Interestingly, the relative morphological observations of the adhered cells and in vitro viability tests show no significant difference between the ASO‐MIMs binding with 13.6 mg g−1 Ova (13.6‐ASO‐MIMs) and bare glass, indicating the excellent biocompatibility of the 13.6‐ASO‐MIMs. Here, the results on largely enhanced adsorption capacity, perm‐selectivity (β values are more than 2.2), regeneration ability (still maintained 90% of the maximum adsorption capacity after 10 cycling operation), and high‐performance cell adhesion system (controlled by the binding amount of template protein) are shown, which clearly demonstrates the potential value of this method in smart biomaterials and biosensors. Multiple‐functional Ag/SiO2/organic based molecularly imprinted membranes (ASO‐MIMs) are prepared for high‐stability protein recognition and cell adhesion/detachment. Because of the high affinity of ASO‐MIMs (comparable to that of the natural receptor) and the innocuity to bioprotein (compared to covalent interactions), the approach reported is a promising candidate for large‐scale applications in protein recognition and cell‐based regenerative medicine.
      PubDate: 2015-08-13T13:35:11.436181-05:
      DOI: 10.1002/adfm.201502465
  • Unconventional Aluminum Ion Intercalation/Deintercalation for Fast
           Switching and Highly Stable Electrochromism
    • Authors: Yuyu Tian; Weikun Zhang, Shan Cong, Yuanchuan Zheng, Fengxia Geng, Zhigang Zhao
      Abstract: Electrochromic devices have many important commercial applications ranging from electronic paper like displays, antiglare rear‐view mirrors in cars, to energy‐saving smart windows in buildings. Monovalent ions such as H+, Li+, and Na+ are widely used as insertion ions in electrochromic devices but have serious limitations such as instability, high‐cost, and hard handling. The utilization of trivalent ions as insertion ions has been largely overlooked probably because of the strong electrostatic interactions between ions and intercalation framework and the resulted difficulties of intercalation. It is demonstrated that the trivalent ion, Al3+, can be used as efficient insertion ion by using metal oxide hosts in nanostructured form, which brings the desired fast‐switch, high‐contrast, and high‐stability as well to electrochromic devices. Differing from the usual structure degradation by repeated guest intercalation/deintercalation, the Al3+ insertion introduces strong electrostatic forces, which on some degree stabilize the crystal structure and consequently yield much enhanced performances. Using Al3+ as insertion ions in electrochromic applications allows for fast switching, high‐contrast, and highly stable electrochromic behavior. It also makes it possible to overcome the existing problems encountered by the conventional insertion ions. The new, low‐cost insertion ion is beneficial for the fabrication of more stable and economical electrochromic devices.
      PubDate: 2015-08-13T13:34:35.650671-05:
      DOI: 10.1002/adfm.201502638
  • Chinese‐Noodle‐Inspired Muscle Myofiber Fabrication
    • Abstract: Much effort has been made to engineer artificial fiber‐shaped cellular constructs that can be potentially used as muscle fibers or blood vessels. However, existing microfiber‐based approaches for culturing cells are still limited to 2D systems, compatible with a restricted number of polymers (e.g., alginate) and always lacking in situ mechanical stimulation. Here, a simple, facile, and high‐throughput technique is reported to fabricate 3D cell‐laden hydrogel microfibers (named hydrogel noodles), inspired by the fabrication approach for Chinese Hele noodle. A magnetically actuated and noncontact method to apply tensile stretch on hydrogel noodles has also been developed. With this method, it is found that cellular strain‐threshold and saturation behaviors in hydrogel noodles differ substantially from their 2D analogs, including proliferation, spreading, and alignment. Moreover, it is shown that these cell‐laden microfibers can induce muscle myofiber formation by tensile stretching alone. This easily adaptable platform holds great potential for the creation of functional tissue constructs and probing mechanobiology in three dimensions. C2C12 muscle myofibers within hydrogel fibers are successfully generated using a simple, facile, and high‐throughput method that is inspired by the fabrication process of Chinese noodles. The effect of mechanical tensile strain on cell viability, spreading, and proliferation is also investigated. Such an approach holds potential to create functional tissue constructs and provides insight into the mechanobiological responses of cells in three dimensions.
      PubDate: 2015-08-12T05:41:54.134648-05:
      DOI: 10.1002/adfm.201502018
  • Oxygen Diffusion in SrTiO3 and Related Perovskite Oxides
    • Authors: R. A. De Souza
      Abstract: The transport of oxygen ions plays a central role in determining the performance or the degradation of perovskite‐type oxides in applications as diverse as ceramic capacitors, solid electrolytes, memristive devices and all‐oxide electronics. In this Feature Article, experimental data reported in the literature for oxygen diffusion in SrTiO3 and in related titanate, zirconate and cerate perovskite oxides [CaTiO3, BaTiO3, (Na,Bi)TiO3, Pb(Ti,Zr)O3, CaZrO3, SrZrO3, BaZrO3, SrCeO3, BaCeO3] are reviewed. The two related aims are to draw attention to discrepancies and to identify reliable diffusion data. The physical limit to the diffusivity of oxygen vacancies in a perovskite oxide is also considered. Methods of studying diffusion in oxides are reviewed. Oxygen diffusion coefficients extracted from the literature for SrTiO3 and related titanate, zirconate and cerate perovskites are compared.
      PubDate: 2015-08-06T07:04:49.37961-05:0
      DOI: 10.1002/adfm.201500827
  • Resistive Switching in Mott Insulators and Correlated Systems
    • Abstract: Resistive random access memories (ReRAM) form an emerging type of non‐volatile memories, based on an electrically driven resistive switching (RS) of an active material. This Feature Article focuses on a broad class of ReRAM where the active material is a Mott insulator or a correlated system. These materials can indeed undergo various insulator‐to‐metal transitions (IMT) in response to external perturbations such as electronic doping or temperature. These IMT explain most of resistive switching observed in correlated insulators as, for example, the Joule heating induced RS in VO2. The main part of this Feature Article is dedicated to a new mechanism of resistive switching recently unveiled in canonical Mott insulators such as (V1‐xCrx)2O3, NiS2‐xSex and AM4Q8 (A = Ga, Ge; M = V, Nb, Ta, Mo; Q = S, Se, Te). In these narrow gap Mott insulators, an electronic avalanche breakdown induces a resistive switching, first volatile above a threshold electric field of a few kV/cm and then non‐volatile at higher field. The low resistance state is related to the creation of granular conductive filaments, which, in the non‐volatile case, can be erased by means of Joule heating. ReRAM devices based on this new type of out of equilibrium Mott insulator‐to‐metal transition display promising performances. The different types of resistive switching encountered in Mott insulators or correlated systems are discussed. Resistive switching that is well explained by insulator‐to‐metal transitions driven by doping or temperature is first described. The new mechanism of resistive switching driven by electric field recently unveiled in canonical Mott insulators is also addressed.
      PubDate: 2015-07-14T08:45:18.116173-05:
      DOI: 10.1002/adfm.201500823
  • Physics of the Switching Kinetics in Resistive Memories
    • Abstract: Memristive cells based on different physical effects, that is, phase change, valence change, and electrochemical processes, are discussed with respect to their potential to overcome the voltage–time dilemma that is crucial for an application in storage devices. Strongly non‐linear switching kinetics are required, spanning more than 15 orders of magnitude in time. Temperature‐driven and field‐driven crystallization, threshold switching, ion migration, as well as redox reactions at interfaces are identified as relevant mechanisms. In phase change materials the combination of a reversible threshold switching and extremely large crystal growth velocities at high voltages enables ultra‐fast resistive switching whereas lower voltages will not be sufficient to overcome the energy barrier for crystallization. In electrochemical cells it depends on the voltage regime, which mechanism is the rate‐determining one for switching. While electro‐crystallization dominates at low voltages, electron transfer in the medium voltage range and a mixture of electron transfer and ion migration at high voltages. In valence change materials, ion migration is found to be accelerated by a combined effect of electric field and local temperature increase due to Joule heating. All discussed types of resistive switches can provide sufficient non‐linearity of switching kinetics for overcoming the voltage time dilemma. Highly non‐linear switching kinetics can overcome the voltage‐time dilemma in resistive switching memory devices: while information can be written very fast using high voltages, data retention is excellent over long times under application of lower read voltages. The two time scales can be up to 15 orders of magnitude apart for voltages spanning only around one order of magnitude.
      PubDate: 2015-06-18T12:27:46.030652-05:
      DOI: 10.1002/adfm.201500825
  • Realization of Boolean Logic Functionality Using Redox‐Based
           Memristive Devices
    • Abstract: Emerging resistively switching devices are thought to enable ultradense passive nanocrossbar arrays for use as random access memories (ReRAM) by the end of the decade, both for embedded and mass storage applications. Moreover, ReRAMs offer inherent logic‐in‐memory (LIM) capabilities due to the nonvolatility of the devices and therefore great potential to reduce the communication between memory and calculation unit by alleviating the so‐called von Neumann bottleneck. A single bipolar resistive switching device is capable of performing 14 of 16 two input logic functions in the logic concept presented by Linn et al. (“CRS‐logic”). In this paper, five types of selectorless devices are considered to validate this CRS‐logic concept is experimentally by means of the IMP and AND logic operations. As reference device a TaO x ‐based ReRAM cell is considered, which is compared to three more advanced device configurations consisting either of a threshold supported resistive switch (TS‐ReRAM), a complementary switching device (CS), or a complementary resistive switch (CRS). It is shown that all of these devices offer the desired LIM behavior. Moreover, the feasibility of XOR and XNOR operations using a modified logic concept is applied for both CS and CRS devices and the pros and cons are discussed. Resistive switching devices enable sequential logic‐in‐memory operations. The feasibility of 14 of 16 two input Boolean logic functions is proven experimentally for: redox‐based resistive switching cells (ReRAMs), ReRAMs offering inherent threshold switching, ReRAMs offering complementary switching (CS), and complementary resistive switching (CRS) cells. Moreover, it is shown that CS and CRS cells also enable the two remaining functions, XOR and XNOR.
      PubDate: 2015-06-18T12:24:28.589609-05:
      DOI: 10.1002/adfm.201500865
  • Microscopic Complexity in Phase‐Change Materials and its Role for
    • Authors: Volker L. Deringer; Richard Dronskowski, Matthias Wuttig
      Abstract: Phase‐change materials (PCMs) are widely used for data storage and in other functional devices. Despite their seemingly simple compositions, these materials exhibit intriguing microscopic complexity and a portfolio of interesting properties. In this Feature Article, it is shown that structural and electronic peculiarities on the atomic scale are key determinants for the technological success of PCMs. Particular emphasis is put on the interplay of different experimental and theoretical methods, on the bonding nature of crystalline and amorphous PCMs, and on the role of surfaces and nanostructures. Then, unconventional transport properties of the crystalline phases are highlighted, both with regard to electrical and heat conduction. Finally, perspectives and future directions are drawn: for finding new PCMs based on microscopic understanding, and also for new applications of these materials in emerging fields. The property contrast of phase‐change materials (PCMs), used to encode “ones” and “zeroes” in digital memories, originates on the atomic scale. This Feature Article reviews unconventional structural, bonding, and transport properties of seemingly simple PCMs. This intriguing microscopic complexity can be exploited for new applications in data storage and beyond.
      PubDate: 2015-06-10T22:57:44.734837-05:
      DOI: 10.1002/adfm.201500826
  • Low‐Temperature Transport in Crystalline Ge1Sb2Te4
    • Authors: Hanno Volker; Peter Jost, Matthias Wuttig
      Abstract: Disorder and its reduction upon annealing play a crucial role in understanding the electrical transport in the crystalline phase‐change material Ge1Sb2Te4. Previous studies focus either on the impact of disorder at moderate temperatures or on the low‐temperature properties of crystalline films with a low degree of disorder. The present investigation describes and discusses the impact of pronounced disorder on charge transport at low temperatures. The present data reveal the existence of a metal‐to‐insulator transition (MIT), where upon increasing order the zero‐temperature limit of conductivity changes from zero (insulator) to nonzero values (metal). The position of the MIT is determined with respect to the control parameter, i.e., the disorder, which is modified through the annealing conditions. Disorder is shown to localize carriers for an exceptionally large density of states. In the most disordered films, variable range hopping is observed, enabling the determination of the localization length. At the lowest temperatures studied, deviations from Mott variable range hopping are observed, which can be explained by a transition to Efros–Shklovskii hopping due to the presence of a soft Coulomb gap. The phase‐change material Ge1Sb2Te4 displays a strong annealing effect in its electronic properties. It is shown that even an insulator‐to‐metal transition in the zero‐temperature limit takes place. The low‐temperature transport on the insulating side can be described by Mott's hopping law. A crossover to a different transport mechanism at even lower temperatures is investigated.
      PubDate: 2015-06-10T22:57:31.763706-05:
      DOI: 10.1002/adfm.201500830
  • Photocatalysis: Unusual Circularly Polarized Photocatalytic Activity in
           Nanogapped Gold–Silver Chiroplasmonic Nanostructures (Adv. Funct.
           Mater. 36/2015)
    • Authors: Changlong Hao; Liguang Xu, Wei Ma, Xiaoling Wu, Libing Wang, Hua Kuang, Chuanlai Xu
      Pages: 5717 - 5717
      Abstract: On page 5816, Hua Kuang and co‐workers report the fabrication of gold‐gap‐silver nanostructures (GGS NSs) with distinctive plasmon‐induced chiroptical performance in the visible region. The nanogap size of the GGS NSs can be tailored by altering the amount of chiral cysteine. The chiral GGS NSs show unusual circularly polarized photocatalytic activity when irradiated with circularly polarized light.
      PubDate: 2015-09-21T11:09:51.275284-05:
      DOI: 10.1002/adfm.201570237
  • Controlled Polymerization: Modular and Versatile Spatial Functionalization
           of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled
           Radical Polymerization (Adv. Funct. Mater. 36/2015)
    • Authors: Rachael H. Harrison; Joseph A. M. Steele, Robert Chapman, Adam J. Gormley, Lesley W. Chow, Muzamir M. Mahat, Lucia Podhorska, Robert G. Palgrave, David J. Payne, Shehan P. Hettiaratchy, Iain E. Dunlop, Molly M. Stevens
      Pages: 5718 - 5718
      Abstract: The development of a high performance bi‐functional scaffold for use at gliding tissue interfaces is reported by Molly M. Stevens and co‐workers on page 5748. By using controlled radical polymerization to grow dense polymer brushes from the surface of electrospun fibers, robust scaffolds with opposing cell adhesive and antifouling surfaces are prepared with excellent spatial control.
      PubDate: 2015-09-21T11:09:52.213931-05:
      DOI: 10.1002/adfm.201570238
  • Contents: (Adv. Funct. Mater. 36/2015)
    • Pages: 5719 - 5725
      PubDate: 2015-09-21T11:09:45.948592-05:
      DOI: 10.1002/adfm.201570239
  • Tissue Engineering: Recent Advances in Electrospun Nanofibrous Scaffolds
           for Cardiac Tissue Engineering (Adv. Funct. Mater. 36/2015)
    • Authors: Guoxu Zhao; Xiaohui Zhang, Tian Jian Lu, Feng Xu
      Pages: 5875 - 5875
      Abstract: Electrospun nanofibrous materials have been developed for use as scaffolds for regenerating engineered cardiac tissues. On page 5726, Xiaohui Zhang, Feng Xu, and co‐workers present an overview of the design strategies for controlling the chemical, structural, and biological properties of electrospun scaffolds, and the performance of advanced electrospun scaffolds for promoting the functionalities of cardiac tissues. Electrospun scaffolds are demonstrated to hold great potential for cardiac tissue engineering applications.
      PubDate: 2015-09-21T11:09:52.4085-05:00
      DOI: 10.1002/adfm.201570241
  • Electrocatalysts: Nitrogen‐Doped Nanoporous Carbon/Graphene
           Nano‐Sandwiches: Synthesis and Application for Efficient Oxygen
           Reduction (Adv. Funct. Mater. 36/2015)
    • Authors: Jing Wei; Yaoxin Hu, Yan Liang, Biao Kong, Jin Zhang, Jingchao Song, Qiaoliang Bao, George P. Simon, San Ping Jiang, Huanting Wang
      Pages: 5876 - 5876
      Abstract: On page 5768, Huanting Wang and co‐workers report the synthesis of zeolitic‐imidazolate‐framework (ZIF)/graphene oxide (GO) sandwich‐like composites with ultrasmall ZIF nanocrystals (≈20 nm in size) that fully cover the GO via a homogenous nucleation followed by uniform deposition and confined growth process. The ZIF/GO composites are further converted to N‐doped nanoporous carbon/graphene nano‐sandwiches, which act as non‐precious metal catalysts with excellent performance for electrochemical oxygen reduction reaction.
      PubDate: 2015-09-21T11:09:54.985936-05:
      DOI: 10.1002/adfm.201570242
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