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  Subjects -> CHEMISTRY (Total: 843 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (594 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (42 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (594 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 7)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 27)
ACS Catalysis     Full-text available via subscription   (Followers: 28)
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: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 26)
ACS Nano     Full-text available via subscription   (Followers: 179)
ACS Photonics     Full-text available via subscription   (Followers: 5)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 18)
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: 8)
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: 10)
Advanced Functional Materials     Hybrid Journal   (Followers: 48)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 26)
Advances in Chemical Science     Open Access   (Followers: 10)
Advances in Chemistry     Open Access   (Followers: 4)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 14)
Advances in Drug Research     Full-text available via subscription   (Followers: 19)
Advances in Environmental Chemistry     Open Access   (Followers: 1)
Advances in Enzyme Research     Open Access   (Followers: 2)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 13)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 15)
Advances in Nanoparticles     Open Access   (Followers: 11)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 11)
Advances in Polymer Science     Hybrid Journal   (Followers: 38)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 12)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription  
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: 33)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 72)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 25)
American Journal of Plant Physiology     Open Access   (Followers: 11)
American Mineralogist     Full-text available via subscription   (Followers: 7)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 30)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 142)
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: 2)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 7)
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: 13)
Anti-Infective Agents     Hybrid Journal   (Followers: 2)
Antiviral Chemistry and Chemotherapy     Full-text available via subscription   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 5)
Applied Spectroscopy     Full-text available via subscription   (Followers: 16)
Applied Surface Science     Hybrid Journal   (Followers: 23)
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: 5)
Autophagy     Hybrid Journal   (Followers: 3)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 163)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 5)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 6)
Bioinspired Materials     Open Access   (Followers: 2)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 8)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 3)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 32)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 25)
Bioorganic Chemistry     Hybrid Journal   (Followers: 6)
Biopolymers     Hybrid Journal   (Followers: 16)
Biosensors     Open Access   (Followers: 2)
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: 3)
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   (Followers: 1)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 4)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [48 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  [1598 journals]
  • Masthead: (Adv. Funct. Mater. 6/2016)
    • PubDate: 2016-02-08T07:01:11.097511-05:
      DOI: 10.1002/adfm.201670037
       
  • Harnessing Structure–Property Relationshipsfor Poly(alkyl
           thiophene)–Fullerene Derivative Thin Filmsto Optimize Performance in
           Photovoltaic Devices
    • Authors: Nabankur Deb; Bohao Li, Maximilian Skoda, Sarah Rogers, Yan Sun, Xiong Gong, Alamgir Karim, Bobby G. Sumpter, David G. Bucknall
      Abstract: Nanoscale bulk heterojunction (BHJ) systems, consisting of fullerenes dispersed in conjugated polymers have been actively studied in order to produce high performance organic photovoltaics. How the BHJ morphology affects device efficiency, is currently ill‐understood. Neutron reflection together with grazing incidence X‐ray and neutron scattering and X‐ray photoelectron spectroscopy are utilized to gain understanding of the BHJ morphology in functional devices. For nine model systems, based on mixtures of three poly(3‐alkyl thiophenes, P3AT) (A = butyl, hexyl, octyl) blended with three different fullerene derivatives, the BHJ morphology through the film thickness is determined. It is shown that fullerene enrichment occurs at both the electrode interfaces after annealing. The degree of fullerene enrichment is found to strongly correlate with the short circuit current (JSC ) and to a lesser degree with the fill factor. Based on these findings, it is demonstrated that by deliberately adding a fullerene layer at the electron transport layer interface, JSC can be increased by up to 20%, resulting in an overall increase in power conversion efficiency of 5%. The detailed 3D phase morphology of the bulk heterojunction thin films is determined in active organic photovoltaic devices consisting of model poly(alkyl thiophene)–fullerene blends. The observed segregation behavior of the fullerene to the electrodes shows direct correlations with the device performance, in particular the short‐circuit current.
      PubDate: 2016-02-08T06:46:13.180633-05:
      DOI: 10.1002/adfm.201502653
       
  • A Highly Stretchable ZnO@Fiber‐Based Multifunctional Nanosensor for
           Strain/Temperature/UV Detection
    • Authors: Xinqin Liao; Qingliang Liao, Zheng Zhang, Xiaoqin Yan, Qijie Liang, Qinyu Wang, Minghua Li, Yue Zhang
      Abstract: Stretchable and multifunctional sensors can be applied in multifunctional sensing devices, safety forewarning equipment, and multiparametric sensing platforms. However, a stretchable and multifunctional sensor was hard to fabricate until now. Herein, a scalable and efficient fabrication strategy is adopted to yield a sensor consisting of ZnO nanowires and polyurethane fibers. The device integrates high stretchability (tolerable strain up to 150%) with three different sensing capabilities, i.e., strain, temperature, and UV. Typically achieved specifications for strain detection are a fast response time of 38 ms, a gauge factor of 15.2, and a high stability of >10 000 cyclic loading tests. Temperature is detected with a high temperature sensitivity of 39.3% °C−1, while UV monitoring features a large ON/OFF ratio of 158.2. With its fiber geometry, mechanical flexibility, and high stretchability, the sensor holds tremendous prospect for multiparametric sensing platforms, including wearable devices. A stretchable and multifunctional sensor for the application in wearable monitoring devices and multiparametric sensing platforms is developed. Being prepared by a scalable process, the sensor allows rapid and efficient monitoring of strain, temperature, or UV light. With its soft characteristic, light weight, and fiber geometry, it holds prospects to simplify the structure of multifunctional sensing devices.
      PubDate: 2016-02-08T05:57:12.562632-05:
      DOI: 10.1002/adfm.201505223
       
  • Incorporating Graphitic Carbon Nitride (g‐C3N4) Quantum Dots into
           Bulk‐Heterojunction Polymer Solar Cells Leads to Efficiency
           Enhancement
    • Authors: Xiang Chen; Qing Liu, Qiliang Wu, Pingwu Du, Jun Zhu, Songyuan Dai, Shangfeng Yang
      Abstract: Graphitic carbon nitride (g‐C3N4) has been commonly used as photocatalyst with promising applications in visible‐light photocatalytic water‐splitting. Rare studies are reported in applying g‐C3N4 in polymer solar cells. Here g‐C3N4 is applied in bulk heterojunction (BHJ) polymer solar cells (PSCs) for the first time by doping solution‐processable g‐C3N4 quantum dots (C3N4 QDs) in the active layer, leading to a dramatic efficiency enhancement. Upon C3N4 QDs doping, power conversion efficiencies (PCEs) of the inverted BHJ‐PSC devices based on different active layers including poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT:PC61BM), poly(4,8‐bis‐alkyloxybenzo(l,2‐b:4,5‐b′)dithiophene‐2,6‐diylalt‐(alkyl thieno(3,4‐b)thiophene‐2‐carboxylate)‐2,6‐diyl):[6,6]‐phenyl C71‐butyric acid methyl ester (PBDTTT‐C:PC71BM), and poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐co‐3‐fluorothieno [3,4‐b]thiophene‐2‐carboxylate] (PTB7‐Th):PC71BM reach 4.23%, 6.36%, and 9.18%, which are enhanced by ≈17.5%, 11.6%, and 11.8%, respectively, compared to that of the reference (undoped) devices. The PCE enhancement of the C3N4 QDs doped BHJ‐PSC device is found to be primarily attributed to the increase of short‐circuit current (Jsc), and this is confirmed by external quantum efficiency (EQE) measurements. The effects of C3N4 QDs on the surface morphology, optical absorption and photoluminescence (PL) properties of the active layer film as well as the charge transport property of the device are investigated, revealing that the efficiency enhancement of the BHJ‐PSC devices upon C3N4 QDs doping is due to the conjunct effects including the improved interfacial contact between the active layer and the hole transport layer due to the increase of the roughness of the active layer film, the facilitated photoinduced electron transfer from the conducting polymer donor to fullerene acceptor, the improved conductivity of the active layer, and the improved charge (hole and electron) transport. Introducing the “rising star” photocatalyst into polymer solar cells: Graphitic carbon nitride (g‐C3N4) is applied in bulk heterojunction polymer solar cells for the first time by doping g‐C3N4 quantum dots (QDs) in the P3HT:PC61BM, PBDTTT‐C:PC71BM or PTB7‐Th:PC71BM active layer, resulting in obvious efficiency enhancement. Thus, a novel application of g‐C3N4 in energy conversion, beyond the commonly used photocatalyst, is demonstrated.
      PubDate: 2016-02-08T05:56:42.195609-05:
      DOI: 10.1002/adfm.201505321
       
  • Highly Flexible Organic Nanofiber Phototransistors Fabricated on a Textile
           Composite for Wearable Photosensors
    • Authors: Moo Yeol Lee; Jayeon Hong, Eun Kwang Lee, Hojeong Yu, Hyoeun Kim, Jea Uk Lee, Wonoh Lee, Joon Hak Oh
      Abstract: Highly flexible organic nanofiber phototransistors are fabricated on a highly flexible poly(ethylene terephthalate) (PET) textile/poly(dimethylsiloxane) (PDMS) composite substrate. Organic nanofibers are obtained by electrospinning, using a mixture of poly(3,3″′‐didodecylquarterthiophene) (PQT‐12) and poly(ethylene oxide) (PEO) as the semiconducting polymer and processing aid, respectively. PDMS is used as both a buffer layer for flattening the PET textile and a dielectric layer in the bottom‐gate bottom‐contact device configuration. PQT‐12:PEO nanofibers can be well‐aligned on the textile composite substrate by electrospinning onto a rotating drum collector. The nanofiber phototransistors fabricated on the PET/PDMS textile composite substrate show highly stable device performance (on‐current retention up to 82.3 (±6.7)%) under extreme bending conditions, with a bending radius down to 0.75 mm and repeated tests over 1000 cycles, while those prepared on film‐type PET and PDMS‐only substrates exhibit much poorer performances. The photoresponsive behaviors of PQT‐12:PEO nanofiber phototransistors have been investigated under light irradiation with different wavelengths. The maximum photoresponsivity, photocurrent/dark‐current ratio, and external quantum efficiency under blue light illumination were 930 mA W−1, 2.76, and 246%, respectively. Furthermore, highly flexible 10 × 10 photosensor arrays have been fabricated which are able to detect incident photonic signals with high resolution. The flexible photosensors described herein have high potential for applications as wearable photosensors. Highly flexible organic nanofiber phototransistors are prepared using a poly(ethylene terephthalate) textile/poly(dimethylsiloxane) composite and photoresponsive electrospun polymer nano­fibers as flexible substrate and photo­active layers, respectively. The devices show stable electrical performance under extreme bending conditions; and flexible 10 × 10 photosensor arrays exhibit high‐resolution photosignal mapping, which have a high potential for applications as wearable photosensors.
      PubDate: 2016-02-08T05:50:38.110447-05:
      DOI: 10.1002/adfm.201503230
       
  • Upconversion Luminescent Chemodosimeter Based on NIR Organic Dye for
           Monitoring Methylmercury In Vivo
    • Authors: Huiran Yang; Chunmiao Han, Xingjun Zhu, Yi Liu, Kenneth Yin Zhang, Shujuan Liu, Qiang Zhao, Fuyou Li, Wei Huang
      Abstract: While most luminescent organic dyes display intense Stokes fluorescence, some of them exhibit unique single‐photon frequency upconversion luminescence (FUCL). Compared to conventional anti‐Stokes luminescence of lanthanides and two‐photon excitation, FUCL materials display adjustable spectrum area and require a much lower excitation power. Although this is very beneficial for biological applications in the perspective of reducing photodamage to biological samples and photobleaching of the dyes, the utilization of FUCL for biosensing and bioimaging in vivo has not been reported. In this study, we developed a near‐infrared (NIR) rhodamine derivative (FUC‐1) as a chemodosimeter, which displays weak luminescence but undergoes thiolactone ring‐open process leading to luminescence turn‐on in response to mercury(II) cation or methylmercury with good selectivity and high sensitivity in aqueous solution. Interestingly, FUC‐1 displays particular FUCL, excitation at 808 nm leads to luminescence at 745 nm. Compared to Stokes luminescence resulted from excitation at 630 nm, the use of FUCL lowers the detection limit of Hg2+ to be 0.207 nM. FUC‐1 has been used for FUCL bioimaging of methylmercury in live cells and mice. To the best of our knowledge, this is the first example of FUCL biosensing and bioimaging in vivo using visible and NIR fluorescence of small‐molecular dyes. A new near‐infrared chemodosimeter FUC‐1 exhibits a unique anti‐Stokes frequency luminescence emission property, which means that upon illumination with long wavelength light (808 nm), FUC‐1 can emits short wavelength light at 745 nm. Utilizing this amazing upconversion luminescence property, we successfully realize its application in sensing and bioimaging methylmercury in living cells and in living animals.
      PubDate: 2016-02-08T05:50:33.288433-05:
      DOI: 10.1002/adfm.201504501
       
  • 20.0% Efficiency Si Nano/Microstructures Based Solar Cells with Excellent
           Broadband Spectral Response
    • Authors: Zengguang Huang; Xiaomin Song, Sihua Zhong, Haiyuan Xu, Wenxing Luo, Xudong Zhu, Wenzhong Shen
      Abstract: Spectral response of solar cells determines the output performance of the devices. In this work, a 20.0% efficient silicon (Si) nano/microstructures (N/M‐Strus) based solar cell with a standard solar wafer size of 156 × 156 mm2 (pseudo‐square) has been successfully fabricated, by employing the simultaneous stack SiO2/SiNx passivation for the front N/M‐Strus based n+‐emitter and the rear surface. The key to success lies in the excellent broadband spectral responses combining the improved short‐wavelength response of the stack SiO2/SiNx passivated Si N/M‐Strus based n+‐emitter with the extraordinary long‐wavelength response of the stack SiO2/SiNx passivated rear reflector. Benefiting from the broadband spectral response, the highest open‐circuit voltage (Voc) and short‐circuit current density (Jsc) reach up to 0.653 V and 39.0 mA cm−2, respectively. This high‐performance screen‐printed Si N/M‐Strus based solar cell has shown a very promising way to the commercial mass production of the Si based high‐efficient solar cells. A 20.0%‐efficiency, large‐size silicon nano/microstructure (N/M‐Strus)‐based solar cell with excellent broadband spectral response is successfully fabricated by employing the simultaneous stack SiO2/SiNx passivation for the front N/M‐Strus based n+‐emitter and the rear surface. This high‐performance screen‐printed Si N/M‐Strus based solar cell is a very promising way towards the commercial mass production of Si‐based high‐efficiency solar cells.
      PubDate: 2016-02-08T05:49:16.325179-05:
      DOI: 10.1002/adfm.201503553
       
  • Magnetic‐Nanoparticle‐Based Immunoassays‐on‐Chip:
           
    • Abstract: The unique properties of magnetic nanoparticles (MNPs), coupled with versatile surface engineering techniques, have led to a rising class of screening methods that enable separation of specific cell populations from complex biological samples. The growing sophistication and efficiency of these methods have far reaching implications for both fundamental research and clinical applications. In this study, the synthesis and surface engineering of MNPs is reviewed. Here, a model is introduced to illustrate how MNP morphology and particle–particle interactions influence magnetization, which is a key consideration in designing and selecting MNPs for efficient cell separations. Building upon these themes, immunomagnetic assays for capturing, isolating, and characterizing rare cell types from complex biological mixtures are reviewed. Although the focus of this study is on circulating tumor cells, these same techniques can be applied in screening for other rare cells of interest, such as various stem cell populations. In conclusion, current challenges and future directions for magnetic ‐nanomaterial‐based cell screening systems are discussed. The synthesis and surface engineering of magnetic nanoparticles are reviewed alongside their applications in immunomagnetic assays for rare cancer cell screening. A model is introduced to illustrate how the morphology and interactions of nanoparticles influence magnetization.
      PubDate: 2016-02-08T05:49:11.378088-05:
      DOI: 10.1002/adfm.201504176
       
  • FeSe2‐Decorated Bi2Se3 Nanosheets Fabricated via Cation Exchange for
           Chelator‐Free 64Cu‐Labeling and Multimodal Image‐Guided
           Photothermal‐Radiation Therapy
    • Authors: Liang Cheng; Sida Shen, Sixiang Shi, Yuan Yi, Xiaoyong Wang, Guosheng Song, Kai Yang, Gang Liu, Todd E. Barnhart, Weibo Cai, Zhuang Liu
      Abstract: Multifunctional theranostic agents have become rather attractive to realize image‐guided combination cancer therapy. Herein, a novel method is developed to synthesize Bi2Se3 nanosheets decorated with mono‐dispersed FeSe2 nanoparticles (FeSe2/Bi2Se3) for tetra‐modal image‐guided combined photothermal and radiation tumor therapy. Interestingly, upon addition of Bi(NO3)3, pre‐made FeSe2 nanoparticles via cation exchange would be gradually converted into Bi2Se3 nanosheets, on which remaining FeSe2 nanoparticles are decorated. The yielded FeSe2/Bi2Se3 composite‐nanostructures are then modified with polyethylene glycol (PEG). Taking advantages of the high r 2 relaxivity of FeSe2, the X‐ray attenuation ability of Bi2Se3, the strong near‐infrared optical absorbance of the whole nanostructure, as well as the chelate‐free radiolabeling of 64Cu on FeSe2/Bi2Se3‐PEG, in vivo magnetic resonance/computer tomography/photoacoustic/position emission tomography multimodal imaging is carried out, revealing efficient tumor homing of FeSe2/Bi2Se3‐PEG after intravenous injection. Utilizing the intrinsic physical properties of FeSe2/Bi2Se3‐PEG, in vivo photothermal and radiation therapy to achieve synergistic tumor destruction is then realized, without causing obvious toxicity to the treated animals. This work presents a unique method to synthesize composite‐nanostructures with highly integrated functionalities, promising not only for nano‐biomedicine but also potentially for other different nanotechnology fields. Upon addition of Bi(NO3)3, pre‐made FeSe2 nanoparticles are gradually converted into Bi2Se3 nanosheets via cation exchange, obtaining FeSe2 decorated Bi2Se3 (FeSe2/Bi2Se3) multifunctional nano­structures. Utilizing the intrinsic physical properties of FeSe2/Bi2Se3, in vivo tetra‐modal imaging and photothermal and radiation combination therapy is realized. This work presents a new class of 2D composite‐nanostructure with highly integrated functions interesting in cancer theranostics.
      PubDate: 2016-02-08T05:49:01.969051-05:
      DOI: 10.1002/adfm.201504810
       
  • CoFe2O4 and CoFe2O4‐SiO2 Nanoparticle Thin Films with Perpendicular
           Magnetic Anisotropy for Magnetic and Magneto‐Optical Applications
    • Authors: Derya Erdem; Nicholas S. Bingham, Florian J. Heiligtag, Nicolas Pilet, Peter Warnicke, Laura J. Heyderman, Markus Niederberger
      Abstract: This paper presents an efficient colloidal approach to process CoFe2O4 and SiO2 nanoparticles into thin films for magnetic and magneto‐optical applications. Thin films of varying CoFe2O4‐to‐SiO2 ratios (from 0 to 90 wt%) are obtained by sequential spin coating‐calcination cycles from the corresponding nanoparticle dispersions. Scanning electron microscopy analysis reveals a crack free and nanoparticulate structure of the sintered films with thicknesses of 480–1200 nm. Results from the optical characterization indicate a direct band gap ranging from 2.6 to 3.9 eV depending on the SiO2 content. Similarly, the refractive indices and absorption coefficients are tunable upon SiO2 incorporation. In‐plane measurements of the magnetic properties of the CoFe2O4 films reveal a superparamagnetic behavior with both Co2+ and Fe3+ contributing to the magnetism. Polar Kerr measurements show the presence of a spontaneous magnetization in the CoFe2O4 and CoFe2O4‐SiO2 (with SiO2 < 50 wt%) films, pointing to magnetic anisotropy perpendicular to the substrate. The origin of this effect is attributed to the constrained sintering conditions of the nano­particulate film and the negative magnetostriction of CoFe2O4. Thin films for magnetic and magneto‐optical applications are prepared from CoFe2O4 and SiO2 nanoparticle dispersions. Variation of the CoFe2O4‐to‐SiO2 ratio enabled the fine‐tuning of the optical and magneto‐optical properties. In‐plane tensile stresses associated with constrained sintering conditions resulted in perpendicular magnetic anisotropy.
      PubDate: 2016-02-08T05:48:01.453665-05:
      DOI: 10.1002/adfm.201504538
       
  • Understanding the Stability for Li‐Rich Layered Oxide Li2RuO3
           Cathode
    • Authors: Biao Li; Ruiwen Shao, Huijun Yan, Li An, Bin Zhang, Hang Wei, Jin Ma, Dingguo Xia, Xiaodong Han
      Abstract: Lithium‐rich layered oxides are considered as promising cathode materials for Li‐ion batteries with high energy density due to their higher capacity as compared with the conventional LiMO2 (e.g., LiCoO2, LiNiO2, and LiNi1/3Co1/3Mn1/3O2) layered oxides. However, why lithium‐rich layered oxides exhibit high capacities without undergoing a structural collapse for a certain number of cycles has attracted limited attention. Here, based on the model of Li2RuO3, it is uncovered that the mechanism responsible for the structural integrity shown by lithium‐rich layered oxides is realized by the flexible local structure due to the presence of lithium atoms in the transition metal layer, which favors the formation of O22−‐like species, with the aid of in situ extended X‐ray absorption fine structure (EXAFS), in situ energy loss spectroscopy (EELS), and density functional theory (DFT) calculation. This finding will open new scope for the development of high‐capacity layered electrodes. For lithium‐rich materials, the additional lithium atoms in the transition metal layer result in a flexible structure. This allows the formation of O22−‐like species, which cannot be realized in conventional layered oxides without lithium ions in the metal layer.
      PubDate: 2016-02-08T05:47:52.999624-05:
      DOI: 10.1002/adfm.201504836
       
  • Emerging Parallel Dual 2D Composites: Natural Clay Mineral Hybridizing
           MoS2 and Interfacial Structure
    • Authors: Kang Peng; Liangjie Fu, Jing Ouyang, Huaming Yang
      Abstract: MoS2/montmorillonite (MoS2/MMT) composite nanosheets have been successfully synthesized by a facile hydrothermal method, and the catalytic activities of composites are evaluated by reduction reaction of methyl orange in aqueous phase. A preparation strategy demonstrates that MoS2 can be in situ formed on the surface of MMT from Na2MoO4· and H2NCSNH2. The microstructures and morphologies characterization indicates that few‐layered MoS2 nanosheets are uniformly grown on the surface of montmorillonite, and the hydrogen bonds are formed at the interfaces. The catalytic activity of MoS2/MMT is enhanced by support of montmorillonite, which can be attribu­ted to the large surface area, more reactive sites, dispersibility of MoS2/MMT, and the synergistic adsorption property of montmorillonite. Based on density functional theory calculations, the preferred adsorption configurations of MoS2 cluster on MMT are studied. The supporting effect of MMT on MoS2 nanoparticles will lead to the anchoring of these reactive MoS2 nanoparticles on clay surface and enhance the absorption ability of MoS2 to the organics and meanwhile improving the catalytic properties of the MoS2/MMT composite. The MoS2/MMT composite nanosheets show prospective application to treat effectively wastewater of dyes. MoS2/montmorillonite (MoS2/MMT) composite nanosheets have been successfully synthesized with MoS2 in situ formed on the surface of MMT via hydrogen bonds. The enhanced catalytic activi­ty of MoS2/MMT can be attributed to the large surface area, more reactive sites, dispersibility, and the synergistic adsorption property of MMT. Further DFT calculations indicate the preferred adsorption configurations of MoS2 cluster on MMT.
      PubDate: 2016-02-08T05:47:43.01104-05:0
      DOI: 10.1002/adfm.201504942
       
  • Dragonfly‐Eye‐Inspired Artificial Compound Eyes with
           Sophisticated Imaging
    • Authors: Zefang Deng; Feng Chen, Qing Yang, Hao Bian, Guangqing Du, Jiale Yong, Chao Shan, Xun Hou
      Abstract: The natural compound eye is a striking imaging device with a wealth of fascinating optical features such as a wide field of view (FOV), low aberration, and high sensitivity. Dragonflies in particular possess large, sophisticated compound eyes that exhibit high resolving power and information‐processing capacity. Here, a large‐scale artificial compound eye inspired by the unique designs of natural counterparts is presented. The artificial compound eye is created by a high‐efficiency strategy that combines single‐pulse femtosecond laser wet etching with thermal embossing. These eyes have a macrobase diameter of 5 mm and ≈30 000 close‐packed ommatidia with an average diameter of 24.5 μm. Moreover, the optical properties of the artificial compound eyes are investigated; the results confirm that the eye demonstrates advanced imaging quality, an exceptionally wide FOV of up to 140°, and low aberration. A large‐scale artificial compound eye, with a total of 30 000 ommatidia, is successfully fabricated by a high‐efficiency strategy that combines single‐pulse femtosecond laser wet etching with thermal embossing. The optical properties of the artificial compound eyes are investigated; the results confirm that the eye demonstrates comparable imaging quality, an exceptionally wide FOV of up to 140°, and low aberration.
      PubDate: 2016-02-08T05:47:33.636584-05:
      DOI: 10.1002/adfm.201504941
       
  • Tribotronic Phototransistor for Enhanced Photodetection and Hybrid Energy
           Harvesting
    • Authors: Chi Zhang; Zhao Hua Zhang, Xiang Yang, Tao Zhou, Chang Bao Han, Zhong Lin Wang
      Abstract: Tribotronics is a new field developed by coupling triboelectricity and semiconductor, which can drive triboelectric‐charge‐controlled optoelectronic devices by further introducing optoelectronics. In this paper, a tribotronic phototransistor (TPT) is proposed by coupling a field‐effect phototransistor and a triboelectric nanogenerator (TENG), in which the contact‐induced inner gate voltage by the mobile frictional layer is used for modulating the photodetection characteristics of the TPT. Based on the TPT, alternatively, a coupled energy‐harvester (CEH) is fabricated for simultaneously scavenging solar and wind energies, in which the output voltage on the external resistance from the wind driven TENG is used as the gate voltage of the TPT for enhancing the solar energy conversion. As the wind speed increases, the photovoltaic characteristics of the CEH including the short‐circuit current, open‐circuit voltage, and maximal output power have been greatly enhanced. This work has greatly expanded the functionality of tribotronics in photodetection and energy harvesting, and provided a potential solution for highly efficient harvesting and utilizing multitype energy. A tribotronic phototransistor is proposed by coupling a field‐effect phototransistor and a triboelectric nanogenerator, for ­enhancing the photodetection characte­ristics. As an alternative design, a ­coupled energy‐harvester is fabricated for enhancing the solar energy conversion by simultaneously scavenging the wind ­energy. This work has greatly expanded the ­functionality of tribotronics in photodetection and hybrid energy harvesting.
      PubDate: 2016-02-08T05:47:25.434896-05:
      DOI: 10.1002/adfm.201504919
       
  • Hexagonal Boron Nitride Thin Film for Flexible Resistive Memory
           Applications
    • Authors: Kai Qian; Roland Yingjie Tay, Viet Cuong Nguyen, Jiangxin Wang, Guofa Cai, Tupei Chen, Edwin Hang Tong Teo, Pooi See Lee
      Abstract: Hexagonal boron nitride (hBN), which is a 2D layered dielectric material, sometimes referred as “white graphene” due to its structural similarity with graphene, has attracted much attention due to its fascinating physical properties. Here, for the first time the use of chemical vapor deposition ‐grown hBN films to fabricate ultrathin (≈3 nm) flexible hBN‐based resistive switching memory device is reported, and the switching mechanism through conductive atomic force microscopy and ex situ transmission electron microscopy is studied. The hBN‐based resistive memory exhibits reproducible switching endurance, long retention time, and the capability to operate under extreme bending conditions. Contrary to the conventional electrochemical metallization theory, the conductive filament is found to commence its growth from the anode to cathode. This work provides an important step for broadening and deepening the understanding on the switching mechanism in filament‐based resistive memories and propels the 2D material application in the resistive memory in future computing systems. Ultrathin hexagonal boron nitride (hBN) film (≈3 nm) is fabricated via chemical vapor deposition for flexible resistive memory applications. The as‐fabricated Ag TE/hBN/Cu foil memory device shows excellent performances, and, contrary to the conventional electrochemical metallization theory, physical evidence is provided to show that the filament growth commences from the anode to cathode.
      PubDate: 2016-02-08T02:59:36.695546-05:
      DOI: 10.1002/adfm.201504771
       
  • Stiff and Transparent Multilayer Thin Films Prepared Through
           Hydrogen‐Bonding Layer‐by‐Layer Assembly of Graphene and
           Polymer
    • Authors: Fangming Xiang; Dorsa Parviz, Tara M. Givens, Ping Tzeng, Eric M. Davis, Christopher M. Stafford, Micah J. Green, Jaime C. Grunlan
      Abstract: Due to their exceptional orientation of 2D nanofillers, layer‐by‐layer (LbL) assembled polymer/graphene oxide thin films exhibit unmatched mechanical performance relative to any conventionally produced counterparts with similar composition. Unprecedented mechanical property improvement, by replacing graphene oxide with pristine graphene, is demonstrated in this work. Polyvinylpyrrolidone‐stabilized graphene platelets are alternately deposited with poly(acrylic acid) using hydrogen bonding assisted LbL assembly. Transmission electron microscopy imaging and the Halpin‐Tsai model are used to demonstrate, for the first time, that intact graphene can be processed from water to generate polymer nanocomposite thin films with simultaneous parallel‐alignment, high packing density, and exfoliation. A multilayer thin film with only 3.9 vol% of highly exfoliated, and structurally intact graphene, increases the elastic modulus (E) of a polymer multilayer thin film by 322% (from 1.41 to 4.81 GPa), while maintaining visible light transmittance of ≈90%. This is one of the greatest improvements in elastic modulus ever reported for a graphene‐filled polymer nanocomposite with a glassy (E > 1 GPa) matrix. The technique described here provides a powerful new tool to improve nanocomposite properties (mechanical, gas transport, etc.) that can be universally applied to a variety of polymer matrices and 2D nanoplatelets. Polymer/graphene nanocomposites are produced using hydrogen‐bonding assisted layer‐by‐layer assembly. A multilayer thin film with 3.9 vol% of highly exfoliated, parallel aligned, and structurally intact graphene exhibits a 322% increase in elastic modulus (from 1.41 to 4.81 GPa), while maintaining high visible light transmittance.
      PubDate: 2016-02-08T02:59:32.725751-05:
      DOI: 10.1002/adfm.201504758
       
  • Achieving Above 60% External Quantum Efficiency in Organic
           Light‐Emitting Devices Using ITO‐Free Low‐Index
           Transparent Electrode and Emitters with Preferential Horizontal Emitting
           Dipoles
    • Abstract: Comprehensive theoretical and experimental studies are reported on organic light‐emitting devices (OLEDs) adopting either the conventional high‐index indium tin oxide (ITO) electrode or the low‐index conducting polymer electrode, either isotropic emitters or emitters having preferentially horizontal emitting dipoles, and different layer structures. Intriguingly, with the use of low‐index electrode in the device, in addition to the known suppression of waveguided modes, the surface plasmon modes can also be effectively suppressed with larger emitter‐to‐metal distances yet with better immunity to accompanied increase of the competing waveguided modes (induced by thicker organic layers) as in the ITO device. As a result, overall coupling efficiencies of OLED internal radiation into substrates can be significantly enhanced over those with ITO electrodes. Through effective extraction of radiation within substrates, green phosphorescent OLEDs adopting both the low‐index ITO‐free electrode and the preferentially horizontal dipole emitter (with a horizontal dipole ratio of 76%) achieve a high external quantum efficiency (EQE) of up to ≈64%. The simulation also predicts that very high EQEs of ≥80% are possible with highly horizontal dipole emitters for all red/green/blue/white OLEDs, clearly revealing the potential of combining low‐index transparent electrodes and horizontal dipole emitters for high‐efficiency OLEDs. A combination of low‐index transparent electrodes and preferentially horizontal dipole emitters realizes organic light‐emitting devices with ≈64% external quantum efficiency (EQE). In addition to suppressing waveguided modes, low‐index electrodes also effectively suppress surface plasmon modes with larger emitter‐to‐metal distances yet with better immunity to accompanied increase of competing waveguided modes, resulting in enhanced coupling efficiencies into substrates and EQEs.
      PubDate: 2016-02-08T02:59:28.155905-05:
      DOI: 10.1002/adfm.201505312
       
  • High‐Throughput Topographic, Mechanical, and Biological Screening of
           Multilayer Films Containing Mussel‐Inspired Biopolymers
    • Abstract: A high‐content screening method to characterize multifunctional multilayer films that combine mechanical adhesion and favorable biological response is reported. Distinct combinations of nanostructured films are produced using layer‐by‐layer methodology and their morphological, physicochemical, and biological properties are analyzed in a single microarray chip. Inspired by the composition of the adhesive proteins in mussels, thin films containing dopamine‐modified hyaluronic acid are studied. Flat biomimetic superhydrophobic patterned chips produced by a bench‐top methodology are used for the build‐up of arrays of multilayer films. The wettability contrasts imprinted onto the chips are allowed to produce individual, position controlled, multilayer films in the wettable regions. The flat configuration of the chip permits to perform a series of nondestructive measurements directly on the individual spots. In situ adhesion properties are directly measured in each spot, showing that nanostructured films richer in dopamine promote the adhesion. In vitro tests show an enhanced cell adhesion for the films with more catechol groups. The advantages presented by this platform include ability to control the uniformity and size of the multilayers films, its suitability to be used as a new low cost toolbox and for high‐content cellular screening, and capability for monitoring in situ a variety of distinct material properties. Inspired by the structure of mussel adhesive proteins, layer‐by‐layer coatings are developed. Many combinations of multilayers films are individually disposed on isolated transparent spots, patterned onto biomimetic superhydrophobic substrates. The adhesion properties of the coatings are analyzed in a high‐throughput way. In vitro tests are carried out to evaluate the biological performance of the multilayer films that can be useful in distinct biomedical applications.
      PubDate: 2016-02-08T02:59:21.638906-05:
      DOI: 10.1002/adfm.201505047
       
  • Microwave‐Assisted Preparation of White Fluorescent Graphene Quantum
           Dots as a Novel Phosphor for Enhanced White‐Light‐Emitting
           Diodes
    • Authors: Zhimin Luo; Guangqin Qi, Keyu Chen, Min Zou, Lihui Yuwen, Xinwen Zhang, Wei Huang, Lianhui Wang
      Abstract: Graphene quantum dots (GQDs) with white fluorescence are synthesized by a microwave‐assisted hydrothermal method using graphite as the precursor. A solution‐processed white‐light‐emitting diode (WLED) is fabricated using the as‐prepared white fluorescent GQDs (white‐light‐emitting graphene quantum dots, WGQDs) doped 4,4‐bis(carbazol‐9‐yl)biphenyl as the emissive layer. White‐light emission is obtained from the WLED with 10 wt% doping concentration of WGQDs, which shows a luminance of 200 cd m−2 at the applied voltage of 11–14 V. Importantly, an external quantum efficiency of 0.2% is achieved, which is the highest among all the reported WLED based on GQDs or carbon dots. The results demonstrate that WGQDs as a novel phosphor may open up a new avenue to develop the environmentally friendly WLEDs for practical application in solid‐state lighting. Graphene quantum dots with white fluorescence are synthesized by microwave‐assisted hydrothermal method. A solution‐processed white‐light‐emitting diode (WLED) is developed using white‐light‐emitting graphene quantum dots as a single‐phase phosphor, which may open up a new avenue to develop the environmentally friendly WLEDs toward their practical application in solid‐state lighting.
      PubDate: 2016-02-08T02:59:11.040291-05:
      DOI: 10.1002/adfm.201505044
       
  • Architecture of Conjugated Donor–Acceptor (D–A)‐Type
           Polymer Films with Cross‐Linked Structures
    • Authors: Jin Huang; Bangan Peng, Weina Wang, Hanxu Ji, Linling Li, Kai Xi, Wenyong Lai, Xinwen Zhang, Xudong Jia
      Abstract: A series of new donor–acceptor (D–A)‐type semiconducting conjugated polymers (SCPs), which can form cross‐linked structural and supramolecular assembly films by hydrogen‐bonding, is successfully synthesized. The microstructures of supramolecular assembly films are further investigated by X‐ray diffraction (XRD), high‐ resolution transmission electron microscopy (HRTEM), and variable‐temperature Fourier transform infrared (FT‐IR) absorption spectra. As electronic transmission (ET) materials, the SCPs demonstrate superior properties by means of fabricating electron‐only devices with the configuration of ITO/ET (SCPs)/Ca/Al. According to space‐charge‐limited current (SCLC) measurements, fluorine‐containing SCPs exhibit much smaller threshold voltages and much higher electron mobilities than Alq3. Meanwhile, a significant enhancement for their luminescence properties is verified by the photoluminescence (PL) and electroluminescent (EL) spectra of cross‐linked‐type SCPs, compared to non‐cross‐linked‐type SCPs. The fabricated polymer light‐emitting diodes (PLEDs) with the configuration of ITO/PEDOT:PSS/EML (SCPs)/BCP/LiF/Al are able to emit the color from green to red with moderately low turn‐on voltages. These results suggested that cross‐linked D–A‐type SCP can become a potential candidate as a kind of multifunctional materials applied in the field of optoelectronic devices. A series of new donor–acceptor‐type semiconducting conjugated polymers with hydrogen bonding cross‐linked structure is reported. They are a potential candidate as multifunctional materials applied in the field of optoelectronic devices because of their excellent electronic transmission, photoluminescence, and electroluminescent properties.
      PubDate: 2016-02-05T10:27:17.61782-05:0
      DOI: 10.1002/adfm.201503379
       
  • Beyond Creation of Mesoporosity: The Advantages of Polymer‐Based
           Dual‐Function Templates for Fabricating Hierarchical Zeolites
    • Abstract: Direct synthesis of hierarchical zeolites currently relies on the use of surfactant‐based templates to produce mesoporosity by the random stacking of 2D zeolite sheets or the agglomeration of tiny zeolite grains. The benefits of using nonsurfactant polymers as dual‐function templates in the fabrication of hierarchical zeolites are demonstrated. First, the minimal intermolecular interactions of nonsurfactant polymers impose little interference on the crystallization of zeolites, favoring the formation of 3D continuous zeolite frameworks with a long‐range order. Second, the mutual interpenetration of the polymer and the zeolite networks renders disordered but highly interconnected mesopores in zeolite crystals. These two factors allow for the synthesis of single‐crystalline, mesoporous zeolites of varied compositions and framework types. A representative example, hierarchial aluminosilicate (meso‐ZSM‐5), has been carefully characterized. It has a unique branched fibrous structure, and far outperforms bulk aluminosilicate (ZSM‐5) as a catalyst in two model reactions: conversion of methanol to aromatics and catalytic cracking of canola oil. Third, extra functional groups in the polymer template can be utilized to incorporate desired functionalities into hierarchical zeolites. Last and most importantly, polymer‐based templates permit heterogeneous nucleation and growth of mesoporous zeolites on existing surfaces, forming a continuous zeolitic layer. In a proof‐of‐concept experiment, unprecedented core–shell‐structured hierarchical zeolites are synthesized by coating mesoporous zeolites on the surfaces of bulk zeolites. Hierarchical zeolites with varied framework types and compositions are fabricated, among which 1D fibrous zeolite structures and hierarchical zeolite‐coated bulk zeolite structures are reported for the first time. Furthermore, the advantages of nonsurfactant polymers over conventional surfactant‐based templates in fabricating hierarchical zeolites are systematically demonstrated.
      PubDate: 2016-02-05T10:04:11.481297-05:
      DOI: 10.1002/adfm.201504888
       
  • Fine Tuned Nanolayered Metal/Metal Oxide Electrode for Semitransparent
           Colloidal Quantum Dot Solar Cells
    • Abstract: Semitransparent photovoltaics have great potential, for example, in building‐integration or in portable electronics. However, the front and back contact electrodes significantly affect the light transmission and photovoltaic performance of the complete device. Herein, the use of a semitransparent nanolayered metal/metal oxide electrode for a semitransparent PbS colloidal quantum dot solar cell to increase the light transmission and power conversion efficiency is reported. The effect of the nanolayered electrode on the optical properties within the solar cells is studied and compared to a theoretically model to identify the origin of optical losses that lower the device transmission. The results show that the light transmission in the visible region and the photovoltaic performance are significantly enhanced with the nanolayered electrode. The solar cell shows an efficiency of 5.4% and average visible transmittance of 24.1%, which is an increase by 28.6% and 59.6%, respectively, compared to the device with a standard Au film as the electrode. These results demonstrate that the optical and electrical modification of transparent electrode is possible and essential for reducing the light reflection and absorption of the electrode in semitransparent photovoltaics, and, meanwhile the demonstrated nanolayered materials may provide an avenue for enhancing the device transparency and efficiency. A semitransparent nanolayered metal/metal oxide electrode is presented for a semitransparent PbS colloidal quantum dot solar cell to increase the light transmission and power conversion efficiency. The solar cell shows an efficiency of 5.4% and average visible transmittance of 24.1%, increased by 28.6% and 59.6%, respectively, compared to the device with a standard Au film as the electrode.
      PubDate: 2016-02-05T10:04:03.573579-05:
      DOI: 10.1002/adfm.201504038
       
  • Template‐Based Engineering of Carbon‐Doped Co3O4 Hollow
           Nanofibers as Anode Materials for Lithium‐Ion Batteries
    • Authors: Chunshuang Yan; Gang Chen, Xin Zhou, Jingxue Sun, Chade Lv
      Abstract: Co3O4 anode materials exhibit poor conductivity and a large volume change, rendering controlling of their nanostructure essential to optimize their lithium storage performance. Carbon‐doped Co3O4 hollow nanofibers (C‐doped Co3O4 HNFs), for the first time are synthesized using bifunctional polymeric nanofibers as template and carbon source. Compared with undoped Co3O4 HNFs and solid Co3O4 NFs, C‐doped Co3O4 HNFs feature a remarkably high specific capacity, excellent cycling stability, and superior rate capacity as anode materials for lithium‐ion batteries. The superior performance of C‐doped Co3O4 HNFs electrodes can be attributed to their structural features, which confer enhanced electron transportation and Li+ ion diffusion due to C‐doping, and tolerance for volume change due to the 1D hollow structure. Density functional theory calculations provide a good explanation of the observed enhanced conductivity in C‐doped Co3O4 HNFs. Carbon‐doped Co3O4 hollow nanofibers are synthesized, displaying excellent Li+ ion storage properties including high specific capacity, long‐term cycling stability, and outstanding rate capacity. Density functional theory calculations reveal a larger delocalization of the band structure as being responsible for the enhanced conductivity observed.
      PubDate: 2016-02-05T10:03:55.705767-05:
      DOI: 10.1002/adfm.201504695
       
  • Light and Strong SiC Networks
    • Abstract: The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions. Ultralight SiC networks are assembled through the directional freezing of microfiber suspensions. The networks are stable at high temperature and have a unique hierarchical architecture that promotes high specific strengths and stiffness. They are thermally insulating but electrically conductive. The approach opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions.
      PubDate: 2016-02-05T10:03:49.705055-05:
      DOI: 10.1002/adfm.201504051
       
  • Controlling Phase Assemblage in a Complex Multi‐Cation System:
           Phase‐Pure Room Temperature Multiferroic
           (1−x)BiTi(1−y)/2FeyMg(1−y)/2O3–xCaTiO3
    • Authors: Pranab Mandal; Michael J. Pitcher, Jonathan Alaria, Hongjun Niu, Marco Zanella, John B. Claridge, Matthew J. Rosseinsky
      Abstract: A room temperature magnetoelectric multiferroic is of interest as, e.g., magnetoelectric random access memory. Bulk samples of the perovskite (1−x)BiTi(1−y)/2FeyMg(1−y)/2O3–xCaTiO3 (BTFM–CTO) are simultaneously ferroelectric, weakly ferromagnetic, and magnetoelectric at room temperature. In BTFM–CTO, the volatility of bismuth oxide, and the complex subsolidus reaction kinetics, cause the formation of a microscopic amount of ferrimagnetic spinel impurity, which complicates the quantitative characterization of their intrinsic magnetic and magnetoelectric properties. Here, a controlled synthesis route to single‐phase bulk samples of BTFM–CTO is devised and their intrinsic properties are determined. For example, the composition x = 0.15, y = 0.75 shows a saturated magnetization of 0.0097μB per Fe, a linear magnetoelectric susceptibility of 0.19(1) ps m−1, and a polarization of 66 μC cm−2 at room temperature. The onset of weak ferromagnetism and linear magnetoelectric coupling are shown to coincide with the onset of bulk long‐range magnetic order by neutron diffraction. The synthesis strategy developed here will be invaluable as the phase diagram of BTFM–CTO is explored further, and as an example for the synthesis of other compositionally complex BiFeO3‐related materials. Phase‐pure bulk samples of the room temperature magnetoelectric multiferroic (1−x)BiTi(1−y)/2FeyMg(1−y)/2O3–xCaTiO3 are prepared by a synthetic route that balances reaction pathway, starting material reactivity and the loss of volatile Bi2O3.
      PubDate: 2016-02-05T10:03:43.875746-05:
      DOI: 10.1002/adfm.201504911
       
  • Hyperbranched Polymers with High Transparency and Inherent High Refractive
           Index for Application in Organic Light‐Emitting Diodes
    • Abstract: Hyperbranched polyvinylsulfides have been prepared through a facile, metal‐free, radical induced “A2+B3” thiol‐yne polymerization of 1,3,5‐tris(naphthalylethynyl) benzene and 1,4‐dithiolbenzene with three different input ratios. The resulting polymers exhibit excellent optical properties like high transparency and very high refractive index (RI) of up to 1.7839, combined with high thermal stability (Td5% up to 420 °C) and excellent solution processability. These properties make them ideal candidates as high RI polymeric materials (HRIP) in connection with light out‐coupling schemes for organic light‐emitting diodes (OLEDs). A series of hyperbranched HRIPs with varying monomer compositions have been compared in their optical properties. Finally, phosphorescent monochrome OLEDs are fabricated on top of HRIP layers to test the compatibility of HRIPs with state‐of‐the‐art OLEDs. The results show that the HRIPs do not deteriorate the performance of the OLEDs while maintaining external quantum efficiencies of over 20% for phosphorescent red OLEDs. These results open a pathway toward alternative, low‐cost, and scalable out‐coupling concepts through refractive index matching of the OLED materials and the HRIPs presented. Hyperbranched polyvinylsulfides with high refractive indices (up to 1.7839) are used as light out‐coupling layer in phosphorescent monochrome OLEDs, allowing external quantum efficiencies >20%. Refractive index matching of polymers and OLED materials opens a pathway toward alternative, low‐cost, and scalable out‐coupling concepts.
      PubDate: 2016-02-05T10:03:39.486183-05:
      DOI: 10.1002/adfm.201504914
       
  • Nanoparticle‐Based Antivirulence Vaccine for the Management of
           Methicillin‐Resistant Staphylococcus aureus Skin Infection
    • Abstract: With the rising threat of antibiotic‐resistant bacteria, vaccination is becoming an increasingly important strategy to prevent and manage bacterial infections. Made from deactivated bacterial toxins, toxoid vaccines are widely used in the clinic as they help to combat the virulence mechanisms employed by different pathogens. Here, the efficacy of a biomimetic nanoparticle‐based antivirulence vaccine is examined in a mouse model of methicillin‐resistant Staphylococcus aureus (MRSA) skin infection. Vaccination with nanoparticle‐detained staphylococcal α‐hemolysin (Hla) effectively triggers the formation of germinal centers and induces high anti‐Hla titers. Compared to mice vaccinated with control samples, those vaccinated with the nanoparticle toxoid show superior protective immunity against MRSA skin infection. The vaccination not only inhibits lesion formation at the site of bacterial challenge but also reduces the invasiveness of MRSA, preventing dissemination into other organs. Overall, this biomimetic nanoparticle‐based toxin detainment strategy is a promising method for the design of potent antivirulence vaccines for managing bacterial infections. A nanoparticle‐based strategy is employed to effectively neutralize and retain bacterial toxins, enabling safe delivery in vivo for antivirulence vaccination. The ability of this approach to elicit potent antitoxin immune responses and protect against live bacterial infection is studied using a murine model of methicillin‐resistant Staphylococcus aureus (MRSA) skin infection with α‐hemolysin as the toxin of interest.
      PubDate: 2016-02-05T10:03:36.061297-05:
      DOI: 10.1002/adfm.201505231
       
  • Graphene Doping Improved Device Performance of ZnMgO/PbS Colloidal Quantum
           Dot Photovoltaics
    • Abstract: Lead sulfide (PbS) colloidal quantum dots (CQDs) solar cells possess the advantages of absorption into the infrared, solution processing, and multiple exciton generation, making them very competitive as a low‐cost photovoltaic alternative. Employing an n‐i‐p ZnO/tetrabutylammonium (TBAI)–PbS/ethanedithiol (EDT)–PbS device configuration, the present study reports a 9.0% photovoltaic device through ZnMgO electrode engineering and graphene doping. Sol–gel‐derived Zn0.9Mg0.1O buffer layer shows better transparency and higher conduction band maximum than ZnO, and incorporation of graphene and chlorinated graphene oxide into the TBAI–PbS and EDT–PbS layer respectively boosts carrier collection, leading to device with significantly enhanced open circuit voltage and short‐circuit current density. It is believed that incorporation of graphene into PbS CQD film as proposed here, and more generally nanosheets of other materials, would potentially open a simple and powerful avenue to overcome the carrier transport bottleneck of CQD optoelectronic device, thus pushing device performance to a new level. ZnMgO/PbS colloidal quantum dot (CQD) photovotaics are constructed through incorporating graphene into the lead sulfide (PbS) CQD layer to improve the open circuit voltage and short circuit current of the device, resulting in a 9.0 ± 0.1% improvement. These devices also possess the advantages of ambient processing and high stability. The incorporation of 2D materials into PbS CQD film opens a new avenue for efficiency improvement of CQD photovoltaics.
      PubDate: 2016-02-05T10:03:30.795916-05:
      DOI: 10.1002/adfm.201505043
       
  • Efficiency and Stability Enhancement in Perovskite Solar Cells by
           Inserting Lithium‐Neutralized Graphene Oxide as Electron
           Transporting Layer
    • Abstract: This work proposes a new perovskite solar cell structure by including lithium‐neutralized graphene oxide (GO‐Li) as the electron transporting layer (ETL) on top of the mesoporous TiO2 (m‐TiO2) substrate. The modified work‐function of GO after the intercalation of Li atoms (4.3 eV) exhibits a good energy matching with the TiO2 conduction band, leading to a significant enhancement of the electron injection from the perovskite to the m‐TiO2. The resulting devices exhibit an improved short circuit current and fill factor and a reduced hysteresis. Furthermore, the GO‐Li ETL partially passivates the oxygen vacancies/defects of m‐TiO2 by resulting in an enhanced stability under prolonged 1 SUN irradiation. Lithium‐neutralized graphene oxide (GO‐Li) as electron transporting layer in perovskite solar cells is reported. The proposed device conjugates the extraordinary conduction properties of graphene based materials with the exceptional harvesting behavior of organoleadtrihalide compounds and shows enhanced power conversion efficiency and improved long term stability under operative conditions.
      PubDate: 2016-02-05T10:02:24.2797-05:00
      DOI: 10.1002/adfm.201504949
       
  • Novel Strategy to Develop Exciplex Emitters for High‐Performance
           OLEDs by Employing Thermally Activated Delayed Fluorescence Materials
    • Abstract: To develop high‐performance thermally activated delayed fluorescence (TADF) exciplex emitters, a novel strategy of introducing a single‐molecule TADF emitter as one of the constituting materials has been presented. Such a new type of exciplex TADF emitter will have two reverse intersystem crossing (RISC) routes on both the pristine TADF molecules and the exciplex emitters, benefiting the utilization of triplet excitons. Based on a newly designed and synthesized single‐molecule TADF emitter MAC, a highly efficient exciplex emitter MAC:PO‐T2T has been obtained. The device based on MAC:PO‐T2T with a weight ratio of 7:3 exhibits a low turn‐on voltage of 2.4 V, high maximum efficiency of 52.1 cd A−1 (current efficiency), 45.5 lm W−1 (power efficiency), and 17.8% (external quantum efficiency, EQE), as well as a high EQE of 12.3% at a luminance of 1000 cd m−2. The device shows the best performance among reported organic light‐emitting devices based on exciplex emitters. Such high‐efficiency and low‐efficiency roll‐off should be ascribed to the additional reverse intersystem crossing process on the MAC molecules, showing the advantages of the strategy described in this study. A new type of high‐performance exciplex thermally activated delayed fluorescence TADF emitter is demonstrated by introducing single‐molecule TADF emitter as one of the constituting materials. The OLED based on the novel emitter shows a low turn‐on voltage of 2.4 V and a maximum external quantum efficiency of 17.8% with mild efficiency roll‐off, which offers a new strategy for designing efficient exciplex emitters.
      PubDate: 2016-02-05T10:02:01.429555-05:
      DOI: 10.1002/adfm.201505014
       
  • Magnetic Nanoparticle Facilitated Drug Delivery for Cancer Therapy with
           Targeted and Image‐Guided Approaches
    • Authors: Jing Huang; Yuancheng Li, Anamaria Orza, Qiong Lu, Peng Guo, Liya Wang, Lily Yang, Hui Mao
      Abstract: With rapid advances in nanomedicine, magnetic nanoparticles (MNPs) have emerged as a promising theranostic tool in biomedical applications, including diagnostic imaging, drug delivery and novel therapeutics. Significant preclinical and clinical research has explored their functionalization, targeted delivery, controllable drug release and image‐guided capabilities. To further develop MNPs for theranostic applications and clinical translation in the future, we attempt to provide an overview of the recent advances in the development and application of MNPs for drug delivery, specifically focusing on the topics concerning the importance of biomarker targeting for personalized therapy and the unique magnetic and contrast‐enhancing properties of theranostic MNPs that enable image‐guided delivery. The common strategies and considerations to produce theranostic MNPs and incorporate payload drugs into MNP carriers are described. The notable examples are presented to demonstrate the advantages of MNPs in specific targeting and delivering under image guidance. Furthermore, current understanding of delivery mechanisms and challenges to achieve efficient therapeutic efficacy or diagnostic capability using MNP‐based nanomedicine are discussed. Magnetic nanoparticles (MNPs) have emerged as a promising theranostic tool in biomedical applications, including diagnostic imaging, drug delivery and novel therapeutics. An overview of recent advances in development and application of MNPs for drug delivery is provided with a focus on strategies for targeted and image‐guided drug delivery. MNP carrier fabrication, delivery mechanisms, active targeting approaches, and image‐guided drug deliveries are reviewed. Concluding remarks and future perspectives for MNP drug delivery are presented.
      PubDate: 2016-02-05T05:17:54.207837-05:
      DOI: 10.1002/adfm.201504185
       
  • Smart Ferrofluid with Quick Gel Transformation in Tumors for
           MRI‐Guided Local Magnetic Thermochemotherapy
    • Authors: Koichiro Hayashi; Wataru Sakamoto, Toshinobu Yogo
      Abstract: Improved techniques for local administration of anticancer drugs are needed to reduce the side effects of chemotherapy owing to leakage of anticancer drugs from tumors and to enhance therapeutic efficacy. This study presents the development of smart ferrofluid that transforms immediately into a gel in tumors and generates heat in response to an alternating magnetic field (AMF), simultaneously releasing the anticancer drug. The smart ferrofluid, which is synthesized using less toxic magnetic materials (Fe3O4 nanoparticles), natural polysaccharides (alginate), and amino acids (cysteine), can also act as a contrast agent for magnetic resonance imaging (MRI). The ferrofluid also incorporates an anticancer drug (i.e., doxorubicin, DOX) via hydrogen bonds. AMF causes heating of gels prepared from the DOX‐containing ferrofluid, resulting in gel shrinkage and DOX release. In vivo experiments demonstrated that the ferrofluid transforms into a gel in the tumor, with the gel remaining in the tumor. Furthermore, magnetic thermochemotherapy using this ferrofluid inhibited tumor growth, while magnetic hyperthermia alone had only a marginal effect. Thus, the combination of magnetic hyperthermia and chemotherapy may be important for suppressing tumor growth. In summary, the ferrofluid presented here has the potential to facilitate MRI‐guided magnetic thermochemotherapy through a combination of endoscopic technologies in the future. A biocompatible smart ferrofluid that transforms into a gel immediately after injection into tumors has the potential to facilitate a combination of magnetic hyperthermia and chemotherapy, under the guidance of magnetic resonance imaging. Magnetic thermochemotherapy using the smart ferrofluid shows significantly greater therapeutic efficacy than chemotherapy alone or magnetic hyperthermia alone.
      PubDate: 2016-02-05T05:17:22.225044-05:
      DOI: 10.1002/adfm.201504215
       
  • Liquid‐Exfoliated Black Phosphorous Nanosheet Thin Films for
           Flexible Resistive Random Access Memory Applications
    • Authors: Chunxue Hao; Fusheng Wen, Jianyong Xiang, Shijun Yuan, Bingchao Yang, Lei Li, Wenhong Wang, Zhongming Zeng, Limin Wang, Zhongyuan Liu, Yongjun Tian
      Abstract: Black phosphorous (BP) is a unique layered p‐type semiconducting material. The successful use of BP nanosheets in field‐effect transistors fueled research on BP atomic layers that focuses on, e.g., the exploration of their optical and electronic properties, and promising applications in (opto)electronics. However, BP films are prone to degradation in ambient conditions, which prevents their commercial application. Here, a route to the application of BP films as an environmental stable nonvolatile resistive random access memory is presented. The BP films, which are prepared from exfoliated BP nanosheets in selected solvents, show solvent‐dependent degradation upon ambient exposure, inducing the formation of an amorphous top degraded layer (TDL). The TDL acts as an insulating barrier just below the Al electrode. This property that was only obtained by degradation, confers a bipolar resistive switching behavior with a high ON/OFF current ratio up to ~3 × 105 and excellent retention ability over 105 s to the flexible BP memory devices. The TDL also prevents propagation of degradation further into the film, ensuring excellent memory performance even after three month of ambient exposure. Environmental stable nonvolatile resistive random access memory devices are fabricated with liquid‐exfoliated black phosphorous (BP) nanosheets. Exposure to ambient conditions induces an amorphous top degraded layer with insulating properties in BP‐nanosheet‐based film. Resulting BP memory devices exhibit a bipolar resistive switching behavior with a high ON/OFF current ratio up to ~3 × 105 and an excellent retention ability over 105 s.
      PubDate: 2016-02-05T05:17:14.100426-05:
      DOI: 10.1002/adfm.201504187
       
  • Engineering of Spin Injection and Spin Transport in Organic Spin Valves
           Using π‐Conjugated Polymer Brushes
    • Authors: Rugang Geng; Anandi Roy, Wenbo Zhao, Ram Chandra Subedi, Xiaoguang Li, Jason Locklin, Tho Duc Nguyen
      Abstract: Charge transport in amorphous organic semiconductors is governed by carriers hopping between localized states with small spin diffusion length. Furthermore, the interfacial resistance of organic spin valves (OSVs) is poorly controlled resulting in controversial reports of the magnetoresistance (MR) response. Here, surface‐initiated Kumada transfer polycondensation is used to covalently graft π‐conjugated poly(3‐methylthiophene) brushes from the La0.67Sr0.33MnO3 (LSMO) bottom electrode. The covalent attachment along with the brush morphology allows control over the LSMO/brush interfacial resistance and large spacer mobility. Remarkably, with 15 nm brush spacer layer, an optimum MR effect of 70% at cryogenic temperatures and a MR of 2.7% at 280 K are observed. The temperature dependence of the MR is nearly an order of magnitude weaker than that found in control OSVs made from spin‐coated poly(3‐hexylthiophene). Using a variety of different brush layer thicknesses, the thickness‐dependent MR at 20 K is investigated. A spin diffusion length of 17 nm at −5 mV junction voltage rapidly increased to 48.4 nm at −260 mV. A large magnetoresistance (MR) of 70% at 20 K is reported in an organic spin valve device fabricated using surface grafted π‐conjugated poly‐3‐methylthiophene brushes from La0.67Sr0.33MnO3 (LSMO) bottom electrode. Surface‐initiated Kumada catalyst‐transfer polycondensation generates covalently attached polymer brushes. Covalent attachment and the brush morphology provide a unique spinterface allowing control over LSMO/brush interfacial resistance and spacer mobility, enhancing the MR response.
      PubDate: 2016-02-05T05:16:23.341122-05:
      DOI: 10.1002/adfm.201504201
       
  • High Responsivity Phototransistors Based on Few‐Layer ReS2 for Weak
           Signal Detection
    • Authors: Erfu Liu; Mingsheng Long, Junwen Zeng, Wei Luo, Yaojia Wang, Yiming Pan, Wei Zhou, Baigeng Wang, Weida Hu, Zhenhua Ni, Yumeng You, Xueao Zhang, Shiqiao Qin, Yi Shi, Kenji Watanabe, Takashi Taniguchi, Hongtao Yuan, Harold Y. Hwang, Yi Cui, Feng Miao, Dingyu Xing
      Abstract: 2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few‐layer rhenium disulfide (ReS2) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few‐layer ReS2 flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications. High responsivity phototransistors based on few‐layer rhenium disulfide (ReS2) are presented. The maximum attainable photoresponsivity can reach as high as 88 600 A W−1. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement. It further enables the detection of weak signals. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications.
      PubDate: 2016-02-05T05:16:19.235926-05:
      DOI: 10.1002/adfm.201504408
       
  • A Dendrimer‐Based Electropolymerized Microporous Film:
           Multifunctional, Reversible, and Highly Sensitive Fluorescent Probe
    • Abstract: A dendrimer PYTPAG2 composed of a central pyrene “core” and four exterior “arms” capped with electroactive triphenylamine is developed as an electroactive precursor to prepare fluorescent films through electropolymerization (EP). The fluorescence emission comes from the central pyrene “core” and the steric hindrance of the exterior “arms” is beneficial for the formation of microporous morphology. The stable and highly cross‐linked fluorescent EP films can be obtained even as free‐standing films. Further, these dendrimer EP films are first studied as the multifunctional fluorescent probe: the emission of EP films exposed to trinitrotoluene vapor is quenched by 82% in 120 s; while the fluorescence is increased to nearly 400% in 120 s upon exposure to benzene vapor, EP films also act as the fluorescent sensor to Fe3+ in solution and the limit of detection is obtained to be 8.5 × 10−8 m. All the above detection processes exhibit remarkable reversibility. These excellent performances are attributed to both the specific molecular features of PYTPAG2 and the intrinsic properties of EP films. A dendrimer PYTPAG2 is studied as an electroactive precursor to prepare microporous fluorescent films upon electropolymerization (EP), which could be obtained not only on substrates but also as free‐standing films. Further, these fluorescent EP films are studied as the multifunctional fluorescent probe to trinitrotoluene vapor, iron (III) (Fe3+) ion, and benzene vapor with rapid response, high sensitivity and selectivity, and excellent reusability.
      PubDate: 2016-02-05T05:16:15.132105-05:
      DOI: 10.1002/adfm.201504692
       
  • Lithium–Iron Fluoride Battery with In Situ Surface Protection
    • Abstract: Lithium–metal fluoride (MF) batteries offer the highest theoretical energy density, exceeding that of the sulfur–lithium cells. However, conversion‐type MF cathodes suffer from high resistance, small capacity utilization at room temperature, irreversible structural changes, and rapid capacity fading with cycling. In this study, the successful application of the approach to overcome such limitations and dramatically enhance electrochemical performance of Li–MF cells is reported. By using iron fluoride (FeF2) as an example, Li–MF cells capable of achieving near‐theoretical capacity utilization are shown when MF is infiltrated into the carbon mesopores. Most importantly, the ability of electrolytes based on the lithium bis(fluorosulfonyl)imide (LiFSI) salt is presented to successfully prevent the cathode dissolution and leaching via in situ formation of a Li ion permeable protective surface layer. This layer forms as a result of electrolyte reduction/oxidation reactions during the first cycle of the conversion reaction, thus minimizing the capacity losses during cycling. Postmortem analysis shows the absence of Li dendrites, which is important for safer use of Li metal anodes. As a result, Li–FeF2 cells demonstrate over 1000 stable cycles. Quantum chemistry calculations and postmortem analysis provide insights into the mechanisms of the passivation layer formation and the performance boost. In situ formation of an effective protective surface layer on iron fluoride (FeF2)‐based composite cathodes prevents the cathode dissolution and allows for 1000 stable cycles in high energy density Li–FeF2 cells. Quantum chemistry calculations and postmortem analyses provide insights into the mechanisms of the protective layer formation and the performance boost.
      PubDate: 2016-02-05T05:16:10.306681-05:
      DOI: 10.1002/adfm.201504848
       
  • Chloride and Indium‐Chloride‐Complex Inorganic Ligands for
           Efficient Stabilization of Nanocrystals in Solution and Doping of
           Nanocrystal Solids
    • Abstract: Here, the surface functionalization of CdSe and CdSe/CdS core/shell nanocrystals (NCs) with compact chloride and indium‐chloride‐complex ligands is reported. The ligands provide not only short interparticle distances but additionally control doping and passivation of surface trap states, leading to enhanced electronic coupling in NC‐based arrays. The solids based on these NCs show an excellent electronic transport behavior after heat treatment at the relatively low temperature of 190 °C. Indeed, the indium‐chlorido‐capped 4.5 nm CdSe NC based thin‐film field‐effect transistor reaches a saturation mobility of μ = 4.1 cm2 (V s)−1 accompanied by a low hysteresis, while retaining the typical features of strongly quantum confined semiconductor NCs. The capping with chloride ions preserves the high photoluminescence quantum yield (≈66%) of CdSe/CdS core/shell NCs even when the CdS shell is relatively thin (six monolayers). The simplicity of the chemical incorporation of chlorine and indium species via solution ligand exchange, the efficient electronic passivation of the NC surface, as well as their high stability as dispersions make these materials especially attractive for wide‐area solution‐processable fabrication of NC‐based devices. The chemical incorporation of chlorine and indium species into nanocrystal solids via solution ligand exchange is demonstrated. The nanocrystals formed by this method possess efficient electronic surface passivation and form stable dispersions. Moreover, strong control over the charge carrier density in the nanocrystal arrays is achieved, an attractive characteristic for solution‐processable cutting‐edge electronics.
      PubDate: 2016-02-05T05:16:03.414294-05:
      DOI: 10.1002/adfm.201504767
       
  • Graphene Reinforced Carbon Nanotube Networks for Wearable Strain Sensors
    • Authors: Jidong Shi; Xinming Li, Huanyu Cheng, Zhuangjian Liu, Lingyu Zhao, Tingting Yang, Zhaohe Dai, Zengguang Cheng, Enzheng Shi, Long Yang, Zhong Zhang, Anyuan Cao, Hongwei Zhu, Ying Fang
      Abstract: Transparent, stretchable films of carbon nanotubes (CNTs) have attracted significant attention for applications in flexible electronics, while the lack of structural strength in CNT networks leads to deformation and failure under high mechanical load. In this work, enhancement of the strength and load transfer capabilities of CNT networks by chemical vapor deposition of graphene in the nanotube voids is proposed. The graphene hybridization significantly strengthens the CNT networks, especially at nanotube joints, and enhances their resistance to buckling and bundling under large cyclic strain up to 20%. The hybridized films show linear and reproducible responses to tensile strains, which have been applied in strain sensors to detect human motions with fast response, high sensitivity, and durability. In‐situ graphene hybridization is applied to enhance the structural strength in carbon nanotube (CNT) networks under high mechanical load. The CNT–graphene hybrids effectively resist the buckling deformation of CNT network due to strong interaction and effective load transfer within the hybridized films, and could be applied in wearable and implantable electronics.
      PubDate: 2016-02-05T05:15:56.450294-05:
      DOI: 10.1002/adfm.201504804
       
  • Optimization and Analysis of Conjugated Polymer Side Chains for
           High‐Performance Organic Photovoltaic Cells
    • Abstract: Optimization and analysis of conjugated polymer side chains for high‐performance organic photovoltaic cells (OPVs) reveal a critical relationship between the chemical structure of the side chains and photovoltaic properties of polymer‐based bulk heterojunction OPVs. In particular, the impact of the alkyl side chain length on the π‐bridging (thienothiophene, TT) unit is considered by designing and synthesizing a series of benzodithiophene derivatives (BDT(T)) and thieno[3,2‐b]thiophene‐π‐bridged thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (ttTPD) alternating copolymers, PBDT(T)‐(R2)ttTPD, with alkyl chains of varying length on the TT unit. Using a combination of 2D X‐ray diffraction, Raman spectroscopy, and electrical device characterization, it is elucidated in detail how these subtle changes to the chemical structure affect the molecular conformation, thin film molecular packing, blend film morphology, optoelectronic properties, and hence overall photovoltaic performance. For copolymers employing both the alkoxy or alkylthienyl‐substituted BDT motifs, it is found that octyl side chains on TT unit yield the maximum degree of molecular backbone coplanarity and result in the highest quality of molecular packing and optimized hole mobility. Inverted devices fabricated using this PBDTT‐8ttTPD: polymer/[6,6]‐phenyl‐C71‐butylic acid methyl ester active layer show a maximum power conversion efficiency (PCE) of 8.7% with large area cells (0.64 cm2) maintaining a PCE of 7.5%. Optimization and analysis of conjugated polymer side chains for high‐performance organic photovoltaic cells (OPVs) reveals a critical relationship between the chemical structure of the side chains and the photovoltaic properties of bulk heterojunction OPVs. In particular, the impact of the alkyl side chain length on the π‐bridging thienothiophene (TT) unit is considered, by designing and synthesizing a series of copolymers, PBDT(T)‐(R2)ttTPD.
      PubDate: 2016-02-05T04:54:53.977608-05:
      DOI: 10.1002/adfm.201504093
       
  • Emergent Noncentrosymmetry and Piezoelectricity Driven by Oxygen
           
    • Authors: Megan E. Strayer; Arnab Sen Gupta, Hirofumi Akamatsu, Shiming Lei, Nicole A. Benedek, Venkatraman Gopalan, Thomas E. Mallouk
      Abstract: The loss of centrosymmetry via oxygen octahedral rotations is demonstrated in the n = 2 Dion–Jacobson family of layered oxide perovskites, A′LaB2O7 (A′ = Rb, Cs; B = Nb, Ta). Ab initio density functional theory calculations predict that all four materials should adopt polar space groups, in contrast to the results of previous experimental studies that have assigned these materials to the centrosymmetric P4/mmm space group. Optical second harmonic generation experiments confirm the presence of a noncentrosymmetric phase at ambient temperature. Piezoresponse force microscopy experiments also show that this phase is piezoelectric. To elucidate the symmetry‐breaking and assign the appropriate space groups, the crystal structure of CsLaNb2O7 is refined as a function of temperature from synchrotron X‐ray diffraction data. Above 550 K, CsLaNb2O7 adopts the previously determined centrosymmetric P4/mmm space group. Between 550 and 350 K, the symmetry is lowered to the noncentrosymmetric space group Amm2. Below 350 K, additional symmetry lowering is observed as peak splitting, but the space group cannot be unambiguously identified. Oxygen octahedral rotations lower the symmetry in the Dion–Jacobson family of layered oxide perovskites, A′LaB2O7 (A′ = Rb, Cs; B = Nb, Ta). Loss of centrosymmetry below a critical temperature is evidenced by optical second harmonic generation and by the appearance of superlattice reflections in X‐ray diffraction patterns.
      PubDate: 2016-02-05T04:54:06.627092-05:
      DOI: 10.1002/adfm.201504046
       
  • A Moisture‐ and Oxygen‐Impermeable Separator for Aprotic
           Li‐O2 Batteries
    • Abstract: Despite the unparalleled theoretical gravimetric energy, Li‐O2 batteries are still under a research stage because of their insufficient cycle lives. While the reversibility in air‐cathodes has been lately improved significantly by the deepened understanding on the electrode–electrolyte reaction and the integration of diverse catalysts, the stability of the Li metal interface has received relatively much less attention. The destabilization of the Li metal interface by crossover of water and oxygen from the air‐cathode side can indeed cause as fatal degradation for the cycle life as the irreversibility of the air‐cathodes. Here, it is reported that cheap poreless polyurethane separator can effectively suppress this crossover while allowing Li ions to diffuse through selectively. The polyurethane separator also protects Li metal anodes from redox mediators used for enhancing the reversibility of the air‐cathode reaction. Based on the Li metal protection, a persistent capacity of 600 mAh g−1 is preserved for more than 200 cycles. The current approach can be readily applicable to many other rechargeable batteries that suffer from similar interfacial degradation by side products from the other electrode. A poreless polyurethane (PU) separator is implemented in Li–O2 batteries to protect Li metal anodes from continuous oxygen and water crossover from air‐cathodes. The PU separator allows decent Li ion conductivity via interchain wetting of electrolyte. This approach is applicable to many upcoming high‐energy rechargeable batteries using metal anodes with vulnerable interfaces.
      PubDate: 2016-02-03T11:35:29.798994-05:
      DOI: 10.1002/adfm.201504437
       
  • Mechanically Drawable Thermochromic and Mechanothermochromic
           Polydiacetylene Sensors
    • Abstract: Recently, the development of directly writable techniques for depositing functional materials on solid substrates has received great attention. These pen‐on‐paper approaches enable generation of diverse patterned images on solid substrates in a flexible, easy handling, and inexpensive manner. Herein, the development of a directly writable conjugated polymer is described. Mechanically, drawable colorimetric polydiacetylene (PDA)–wax composites are readily fabricated by using a simple mixing‐molding method. Images are mechanically drawn on a paper substrate using the PDA–wax composites, display thermochromism, and mechanothermochromism. The thermochromic transition temperature is dependent on the melting point of the wax and, as a result, can be precisely controlled by the type of wax used. Optical microscopic analysis shows that formation of the DA–wax composite involves movement of wax molecules into a single diacetylene (DA) crystal. This process results in growth of the crystal. Importantly, the PDA crystal, obtained after UV light irradiation, undergoes significant shrinkage upon heating because of the release of monomers and the embedded wax molecules from the crystal. The release of these molecules creates void in the PDA supramolecules, allowing the PDA chains to undergo C–C bond rotation and hence the blue‐to‐red color transition. Hand‐writable colorimetric polydiacetylene (PDA)–wax composite sensors are readily fabricated by using a simple mixing‐molding polymerization method. Images, mechanically drawn using these PDA–wax composites on a paper substrate, display thermochromism and mechnothermochromism. The thermochromic transition temperature can be precisely controlled by the melting point of the wax used.
      PubDate: 2016-02-03T11:31:23.425593-05:
      DOI: 10.1002/adfm.201504845
       
  • Vertical Phase Separation in Small Molecule:Polymer Blend Organic Thin
           Film Transistors Can Be Dynamically Controlled
    • Authors: Kui Zhao; Olga Wodo, Dingding Ren, Hadayat Ullah Khan, Muhammad Rizwan Niazi, Hanlin Hu, Maged Abdelsamie, Ruipeng Li, Er. Qiang Li, Liyang Yu, Buyi Yan, Marcia M. Payne, Jeremy Smith, John E. Anthony, Thomas D. Anthopoulos, Sigurdur T. Thoroddsen, Baskar Ganapathysubramanian, Aram Amassian
      Abstract: Blending of small‐molecule organic semiconductors (OSCs) with amorphous polymers is known to yield high performance organic thin film transistors (OTFTs). Vertical stratification of the OSC and polymer binder into well‐defined layers is crucial in such systems and their vertical order determines whether the coating is compatible with a top and/or a bottom gate OTFT configuration. Here, we investigate the formation of blends prepared via spin‐coating in conditions which yield bilayer and trilayer stratifications. We use a combination of in situ experimental and computational tools to study the competing effects of formulation thermodynamics and process kinetics in mediating the final vertical stratification. It is shown that trilayer stratification (OSC/polymer/OSC) is the thermodynamically favored configuration and that formation of the buried OSC layer can be kinetically inhibited in certain conditions of spin‐coating, resulting in a bilayer stack instead. The analysis reveals here that preferential loss of the OSC, combined with early aggregation of the polymer phase due to rapid drying, inhibit the formation of the buried OSC layer. The fluid dynamics and drying kinetics are then moderated during spin‐coating to promote trilayer stratification with a high quality buried OSC layer which yields unusually high mobility >2 cm2 V−1 s−1 in the bottom‐gate top‐contact configuration. Trilayer stratification (organic semiconductor/polymer/organic semiconductor) is the thermodynamically favored configuration. However, it is shown ‐ using a combination of in situ experiments and phase field simulations ‐ that formation of the buried organic semiconductor layer can be kinetically controlled. Formation of a high quality buried semiconductor layer is induced using careful control. It yields unusually high mobility > 2 cm2 V−1 s−1 in the bottom‐gate top‐contact configuration.
      PubDate: 2016-02-03T07:24:08.979255-05:
      DOI: 10.1002/adfm.201503943
       
  • Nanoscale Graphene Doped with Highly Dispersed Silver Nanoparticles: Quick
           Synthesis, Facile Fabrication of 3D Membrane‐Modified Electrode, and
           Super Performance for Electrochemical Sensing
    • Authors: Yang Li; Panpan Zhang, Zhaofei Ouyang, Mingfa Zhang, Zhoujun Lin, Jingfeng Li, Zhiqiang Su, Gang Wei
      Abstract: The performance of graphene‐based hybrid materials greatly depends on the dispersibility of nanoscale building blocks on graphene sheets. Here, a quick green synthesis of nanoscale graphene (NG) nanosheets decorated with highly dispersed silver nanoparticles (AgNPs) is demonstrated, and then the electrospinning technique to fabricate a novel nanofibrous membrane electrode material is utilized. With this technique, the structure, mechanical stability, biochemical functionality, and other properties of the fabricated membrane electrode material can be easily controlled. It is found that the orientations of NG and the dispersity of AgNPs on the surface of NG have significant effects on the properties of the fabricated electrode. A highly sensitive H2O2 biosensor is thus created based on the as‐prepared polymeric NG/AgNP 3D nanofibrous membrane‐modified electrode (MME). As a result, the fabricated biosensor has a linear detection range from 0.005 to 47 × 10−3m (R = 0.9991) with a supralow detection limit of 0.56 × 10−6m (S/N = 3). It is expected that this kind of nanofibrous MME has wider applications for the electrochemical detection and design of 3D functional nanomaterials in the future. Nanofibrous 3D membrane‐modified electrode (MME) for H2O2 detection are successfully fabricated by electrospun polyvinyl alcohol nanofibrous membrane doped with nanoscale graphene/silver nanoparticle hybrids based on electrospinning technique. With a freestanding porous 3D structure, the MME has super large surface area that can enhance the adsorption of electrolytes and the diffusion of reactants and it has an excellent performance for H2O2.
      PubDate: 2016-02-03T07:24:03.980669-05:
      DOI: 10.1002/adfm.201504533
       
  • Hyaluronic Acid‐Based Hydrogels Enable Rod Photoreceptor Survival
           and Maturation In Vitro through Activation of the mTOR Pathway
    • Authors: Nikolaos Mitrousis; Roger Y. Tam, Alexander E. G. Baker, Derek van der Kooy, Molly S. Shoichet
      Abstract: The culture of isolated photoreceptors in vitro has remained elusive in ­neuroscience. By using defined hyaluronic acid (HA) hydrogels, photo­receptor survival and maturation in vitro is dramatically increased, as evidenced by upregulation of outer segment markers at the RNA and protein levels. While substrate stiffness is known to be a key factor influencing cell survival in vitro, it is shown that isolated photoreceptors do not respond to modifications in hydrogel stiffness modifications but depend, instead, on HA for survival. While the molecular pathways that are induced by HA on photoreceptors are unknown, mTOR activation is identified as the molecular mechanism underlying the pro‐survival effect, and it is demonstrated that the canonical Wnt and RhoA pathways are intermediaries. This work establishes a valuable method for isolated photoreceptor culture in vitro, which will be useful in translational and basic retinal research. The pathways identified herein may be useful targets in retinal degeneration. A hydrogel that can maintain isolated photoreceptors alive in vitro is developed. Toward deciphering its mechanism of action, stiffness and hyaluronic acid presence are investigated. This platform can be used for basic and translational research.
      PubDate: 2016-02-03T07:23:51.738525-05:
      DOI: 10.1002/adfm.201504024
       
  • Red Blood Cell‐Facilitated Photodynamic Therapy for Cancer Treatment
    • Abstract: Photodynamic therapy (PDT) is a promising treatment modality for cancer management. So far, most PDT studies have focused on delivery of photo­sensitizers to tumors. O2, another essential component of PDT, is not artificially delivered but taken from the biological milieu. However, cancer cells demand a large amount of O2 to sustain their growth and that often leads to low O2 levels in tumors. The PDT process may further potentiate the oxygen deficiency, and in turn, adversely affect the PDT efficiency. In the present study, a new technology called red blood cell (RBC)‐facilitated PDT, or RBC‐PDT, is introduced that can potentially solve the issue. As the name tells, RBC‐PDT harnesses erythrocytes, an O2 transporter, as a carrier for photosensitizers. Because photosensitizers are adjacent to a carry‐on O2 source, RBC‐PDT can efficiently produce 1O2 even under low oxygen conditions. The treatment also benefits from the long circulation of RBCs, which ensures a high intraluminal concentration of photosensitizers during PDT and hence maximizes damage to tumor blood vessels. When tested in U87MG subcutaneous tumor models, RBC‐PDT shows impressive tumor suppression (76.7%) that is attributable to the codelivery of O2 and photosensitizers. Overall, RBC‐PDT is expected to find wide applications in modern oncology. Red blood cell(RBC)‐facilitated photodynamic therapy (PDT), or RBC‐PDT, harnesses RBC, an O2 transporter, as a photosensitizer carrier. This measure makes it possible to efficiently generate 1O2 even under low oxygen conditions. RBC‐PDT addresses the oxygen defficiency limitation that is constantly encountered in conventional PDT and is expected to find wide applications in modern oncology.
      PubDate: 2016-02-03T07:23:45.510535-05:
      DOI: 10.1002/adfm.201504803
       
  • Enzyme‐Catalyzed Formation of Supramolecular Hydrogels as Promising
           Vaccine Adjuvants
    • Authors: Huaimin Wang; Zichao Luo, Youzhi Wang, Tao He, Chengbiao Yang, Chunhua Ren, Linsha Ma, Changyang Gong, Xingyi Li, Zhimou Yang
      Abstract: Promising vaccine adjuvants of self‐assembling peptide hydrogels for protein ovalbumin (OVA) are introduced in this study. The hydrogels are formed by the enzyme of phosphatase, and the vaccine adjuvant potency of both l‐ and d‐peptide hydrogels is evaluated. The results indicate that, compared with the clinically used alum adjuvant, both l‐ and d‐peptide hydrogels can increase the IgG production of OVA for about 1.3 and 3.8 times, respectively. Both gels can enhance antigen uptake and induce dendritic cell maturation, and promote and prolong accumulation of antigen in lymph node, as well as evoke germinal center formation. However, the d‐peptide hydrogel with OVA exhibits a slightly more efficient accumulation of OVA in the lymph nodes and seems preventing tumor growth more significantly than its l‐counterpart. With the good biocompatibility and degradability of peptide hydrogels, the hydrogels described in this study have big potential for the production of protein vaccines for immunotherapy against different diseases. Short peptides and the protein antigen can coassemble into supramolecular hydrogels capable of raising both humoral and cellular immune responses in mice.
      PubDate: 2016-02-03T07:23:29.109841-05:
      DOI: 10.1002/adfm.201505188
       
  • Difluorobenzothiadiazole‐Based Small‐Molecule Organic Solar
           Cells with 8.7% Efficiency by Tuning of π‐Conjugated Spacers
           and Solvent Vapor Annealing
    • Abstract: The synthesis of a series of tetrafluorine‐substituted, wide‐bandgap, small molecules consisting of various π‐conjugated spacers (furan, thiophene, selenophene) between indacenodithiophene as the electron‐donating core and the electron‐deficient difluorobenzothiadiazole unit is reported and the effect of the π‐conjugated spacers on the photovoltaic properties is investigated. The alteration of the π‐conjugated spacer enables fine‐tuning of the photophysical properties and energy levels of the small molecules, and allows the adjustment of the charge‐transport properties, the morphology of the photoactive films, as well as their photovoltaic properties. Moreover, most of these devices exhibit superior device performances after CH2Cl2 solvent annealing than without annealing, with a high fill factor (0.70–0.75 for all cases). Notably, the devices based on the new molecule BIT4FTh (with thiophene as the spacer) show an outstanding PCE of 8.7% (with an impressive FF of 0.75), considering its wide‐bandgap (1.81 eV), which is among the highest efficiencies reported so far for small‐molecules‐based solar cells. The morphologies of the photoactive layers with/without CH2Cl2 solvent annealing are characterized by atomic force microscopy, transmission electron microscopy and two‐dimensional grazing incidence X‐ray diffraction analysis. The results reported here clearly indicate that highly efficient small‐molecules‐based solar cells can be achieved through rational design of their molecular structure and optimization of the phase‐separated morphology via an adapted solvent–vapor annealing process. A series of wide‐bandgap small‐molecules are synthesized and the effect of the various π‐conjugated spacers and of an additional solvent–vapor annealing process on their photovoltaic properties is demonstrated. The devices based on BIT4FTh (with thiophene as a spacer) shows an outstanding PCE of 8.7% (with an impressive FF of 0.75), which is among the highest efficiencies reported for devices based on wide‐bandgap small‐molecules.
      PubDate: 2016-02-03T07:23:24.456098-05:
      DOI: 10.1002/adfm.201505020
       
  • Earth‐Abundant and Durable Nanoporous Catalyst for Exhaust‐Gas
           Conversion
    • Authors: Takeshi Fujita; Hideki Abe, Toyokazu Tanabe, Yoshikazu Ito, Tomoharu Tokunaga, Shigeo Arai, Yuta Yamamoto, Akihiko Hirata, Mingwei Chen
      Abstract: Precious metals (Pt and Pd) and rare earth elements (Ce in the form of CeO2) are typical materials for heterogeneous exhaust‐gas catalysts in automotive systems. However, their limited resources and high market‐driven prices are principal issues in realizing the path toward a more sustainable society. In this regard, herein, a nanoporous NiCuMnO catalyst, which is both abundant and durable, is synthesized by one‐step free dealloying. The catalyst thus developed exhibits catalytic activity and durability for NO reduction and CO oxidation. Microstructure characterization indicates a distinct structural feature: catalytically active Cu/CuO regions are tangled with a stable nanoporous NiMnO network after activation. The results obtained by in situ transmission electron microscopy during NO reduction clearly capture the unique reaction‐induced self‐transformation of the nanostructure. This finding can possibly pave the way for the design of new catalysts for the conversion of exhaust gas based on the element strategy. An earth‐abundant and durable nanoporous catalyst is developed for exhaust‐gas conversion. The nanoporous NiCuMnO catalyst obtained by one‐step dealloying exhibits high catalytic activity and durability for NO reduction and CO oxidation. The catalytically active Cu/CuO regions are tangled with a stable nanoporous NiMnO network, indicating a new catalyst design. The nanoporous catalysts may be a rational alternative to traditional precious‐metal catalysts.
      PubDate: 2016-02-03T02:54:34.764888-05:
      DOI: 10.1002/adfm.201504811
       
  • Theoretical Study of Cellular Piezoelectret Generators
    • Authors: Wenbo Li; Nan Wu, Junwen Zhong, Qize Zhong, Sheng Zhao, Bo Wang, Xiaofeng Cheng, Suling Li, Kang Liu, Bin Hu, Jun Zhou
      Abstract: The cellular piezoelectret generator (CPG) has drawn considerable attention as an emerging flexible energy harvester because of its advantages of a simple structure, easy assembly, a low cost, and eco‐friendliness. To facilitate practical applications, an initial theoretical study of CPGs is presented in this work, in which the output characteristics of CPGs can be optimized through an appropriate choice of parameters, including the electret dielectric permittivity, device structure, polarization process, and external load. A good agreement with experimental results is achieved, verifying the validity of the theoretical study. The reported theory offers a complete interpretation of the dynamic working mechanism of CPGs and provides significant guidance for the design of a CPG with enhanced yield. A theoretical study of cellular piezoelectret generators (CPGs) is presented, focusing on the enhancement of their dynamic performance. An effective means to optimize the output characteristics of CPGs is found. This discovery will enhance performance and application range of future devices.
      PubDate: 2016-02-02T14:38:30.551051-05:
      DOI: 10.1002/adfm.201503704
       
  • Energy Quantization in Solution‐Processed Layers of Indium Oxide and
           Their Application in Resonant Tunneling Diodes
    • Abstract: The formation of quantized energy states in ultrathin layers of indium oxide (In2O3) grown via spin coating and thermally annealed at 200 °C in air is studied. Optical absorption measurements reveal a characteristic widening of the optical band gap with reducing In2O3 layer thickness from ≈43 to ≈3 nm in agreement with theoretical predictions for an infinite quantum well. Through sequential deposition of In2O3 and gallium oxide (Ga­2O3) layers, superlattice‐like structures with controlled dimensionality and spatially varying conduction band characteristics are demonstrated. This simple method is then explored for the fabrication of functional double‐barrier resonant tunneling diodes. Nanoscale current mapping analysis using conductive atomic force microscopy reveals that resonant tunneling is not uniform but localized in specific regions of the apparent device area. The latter observation is attributed to variation in the layer(s) thickness of the In2O3 quantum well and/or the Ga2O3 barrier layers. Despite the nonidealities, the tremendous potential of solution‐processable oxide semiconductors for the development of quantum effect devices that have so far been demonstrated only via sophisticated growth techniques is demonstrated. The existence of quantized energy states in ultrathin, solution‐processed layers of indium oxide is demonstrated. For layers below a critical thickness threshold a widening of the optical band gap is observed experimentally and in calculations. Sequential deposition of indium oxide and gallium oxide layers forms double‐barrier resonant tunneling diodes that exhibit negative differential conductance under reverse and forward biases.
      PubDate: 2016-02-02T14:38:21.101121-05:
      DOI: 10.1002/adfm.201503732
       
  • Mesoporous Silica as Nanoreactors to Prepare Gd‐Encapsulated Carbon
           Dots of Controllable Sizes and Magnetic Properties
    • Authors: Hongmin Chen; Geoffrey D. Wang, Xilin Sun, Trever Todd, Fan Zhang, Jin Xie, Baozhong Shen
      Abstract: Gd‐encapsulated carbonaceous dots (Gd@C‐dots) hold great potential in clinical applications as a novel type of T1 contrast agent for magnetic resonance imaging (MRI). However, current synthetic methods require multiple purification steps due to poor size control, making them unsuitable for high throughput. Herein, a novel, mesoporous silica nanoparticle (MSN)‐templated method for the size‐controlled synthesis of Gd@C‐dots is reported. Briefly, MSNs nanoreactors of different pore sizes are loaded with Gd precursors. Upon calcination, carbon layers are grown around the Gd cations. The spatial restraint of the silica cavity facilitates size control of the produced Gd@C‐dots. Specifically, using 3, 7, and 11 nm MSNs as templates allows the synthesis of 3.0, 7.4, and 9.6 nm Gd@C‐dots, respectively. A significant size impact on the magnetic and optical properties of the nanoparticles is shown, with the smallest Gd@C‐dots showing the highest r1 relaxivity (10 mM−1 s−1) and fluorescence quantum yield (30.2%). The 3.0‐nm Gd@C‐dots were then conjugated with a tumor‐targeting ligand, c(RGDyK), and injected into U87MG xenograft tumor models. Good tumor targeting was observed in T1‐weighted MRI images; whereby the unbound nanoparticles were efficiently excreted through renal clearance, avoiding long‐term toxicity to the host. Mesoporous silica nanoparticles serve as nanoreactors for the synthesis of Gd‐Encapsulated carbon dots (Gd@C‐dots) from Gd‐complexes by calcination. Since the dimension of the silica cavity limits growth, the size distribution of the Gd@C‐dots is narrow. The Gd@C‐dots are successfully appied in MRI imaging.
      PubDate: 2016-02-02T14:37:39.653049-05:
      DOI: 10.1002/adfm.201504177
       
  • Free‐Standing Functionalized Graphene Oxide Solid Electrolytes in
           Electrochemical Gas Sensors
    • Authors: Gaopeng Jiang; Maciej Goledzinowski, Felix J. E. Comeau, Hadis Zarrin, Gregory Lui, Jared Lenos, Alicia Veileux, Guihua Liu, Jing Zhang, Sahar Hemmati, Jinli Qiao, Zhongwei Chen
      Abstract: A free‐standing sulfonic acid functionalized graphene oxide (fSGO)‐based electrolyte film is prepared and used in an electrochemical gas sensor, an alcohol fuel cell sensor (AFCS), for the detection of alcohol. The fSGO electrolyte film‐based AFCS detects ethanol vapor with excellent response, linearity, and sensitivity, since it possesses a high proton conductivity (58 mS cm−1 at 55 °C). An ethanol detection limit level as low as 25 ppm is achieved and high selectivity for ethanol over acetone is demonstrated. These results do not only show the promising potential of fSGO films in an electrochemical gas sensors, specifically a portable breathalyzer, but also open an alternative pathway to investigate the application of graphene derivatives in the field of gas sensors. An new type of electrochemical gas sensor, employing a free‐standing film of sulfonic acid functionalized graphene oxide (fSGO) as the solid electrolyte, is developed. Based on the design of alcohol fuel cell sensors (AFCSs), the developed sensor detects alcohol with excellent sensor response, linearity, sensitivity, and selectivity, promising its implementation into portable devices.
      PubDate: 2016-02-02T14:36:57.211462-05:
      DOI: 10.1002/adfm.201504604
       
  • Ultrafast Spectroscopy of Photoexcitations in Organometal Trihalide
           Perovskites
    • Authors: Yaxin Zhai; ChuanXiang Sheng, Chuang Zhang, Zeev Valy Vardeny
      Abstract: Studying the room temperature broadband ultrafast transient response of photoexcitations in three perovskite films, namely MAPbI3, MAPbI1.1Br1.9, and MAPbI3−xClx (MA = CH3NH3), allowed unravelling the branching ratio between photogenerated carriers and excitons, a key factor for optoelectronic applications of perovskites. An instantaneously generated mid‐IR photoinduced absorption (PA) band, PA1 is observed in all three perovskites, as well as a strong derivative‐like band of photoinduced bleaching (PB) and PA (PA2) close to the corresponding absorption band edge. From the distinguished different decay dynamics of the PA bands in MAPbI3, PA1 is interpreted as due to the exciton transition, whereas PA2 and PB are due to band‐filling effect caused by the photocarriers. In contrast, all bands in MAPbI1.1Br1.9 and MAPbI3−xClx share the same dynamics and are therefore due to the same species, namely photogenerated excitons. The transient photoinduced polarization memory (POM) for both excitons and photocarriers as well as the steady‐state photoluminescence (PL) emission are observed in MAPbI3, but not in MAPbI1.1Br1.9 and MAPbI3−xClx because they possess cubic symmetry at room temperature. The estimated long excitons diffusion length (≈150 nm) in MAPbI3 opens up the possibility of photocarriers generation at interfaces and grain boundaries even when the exciton binding energy is large compare to kBT. The room temperature broadband ultrafast transient response of photoexcitations has been studied in three perovskite films: MAPbI3, MAPbI1.1Br1.9, and MAPbI3−xClx (MA = CH3NH3). This work shows that the exciton binding energy in the hybrid perovskites is a crucial parameter that determines the branching ratio between the photogenerated exciton and free carriers following the thermalization process.
      PubDate: 2016-02-02T03:50:18.078719-05:
      DOI: 10.1002/adfm.201505115
       
  • Dealloyed AuNi Dendrite Anchored on a Functionalized Conducting Polymer
           for Improved Catalytic Oxygen Reduction and Hydrogen Peroxide Sensing in
           Living Cells
    • Abstract: Dealloyed‐AuNi dendrite anchored on carboxylic acid groups of a conducting polymer is prepared and demonstrated for the catalysis of the oxygen reduction reaction (ORR) and detection of hydrogen peroxide (H2O2) released from living cells. The dendrite formation is initiated on a poly(benzoic acid‐2,2′:5′,2′′‐terthiophene) (pTBA) layer, where the polymer layer acts as a stable substrate to improve the long‐term stability and catalytic activity of the alloy electrode. A co‐deposition of Au and Ni is performed to produce a Ni‐rich Au surface at first; subsequent removal of the surface Ni atoms through electrochemical dealloying enhances the performance of the catalyst because of an increase in the electrochemically active area by 12 times. The hydrodynamic voltammetry of dealloyed‐AuNi@pTBA shows a half‐wave potential at –0.08 V, which is a large shift towards more positive potential when compared to those on AuNi@pTBA (−0.14 V) and commercial Pt/C (–0.12 V) electrodes. The proposed catalytic electrode achieved a superior analytical performance for the detection of trace H2O2 (at –0.15 V) released from cancer and normal cells with a very low detection limit (ca. 5 nM). In addition, the in vitro studies suggest no significant cytotoxicity effect for the dealloyed sample and the viability of the cells are more than 85% even after 48 h of incubation. A terthiophene polymer‐supported dealloyed AuNi dendrite (AuNi@pTBA) is designed by a simple electrochemical approach. This stable and active electrocatalyst is formed through complexation between the metal ions and the carboxylic acid groups of the polymer. Electrodes based on this material possess excellent catalytic properties, which surpass those of commercial Pt/C electrodes for the oxygen reduction reaction, and are good candidates for the sensitive detection of H2O2 release from living cells.
      PubDate: 2016-02-02T03:42:02.580752-05:
      DOI: 10.1002/adfm.201504506
       
  • Noninvasive Transdermal Vaccination Using Hyaluronan Nanocarriers and
           Laser Adjuvant
    • Authors: Ki Su Kim; Hyemin Kim, Yunji Park, Won Ho Kong, Seung Woo Lee, Sheldon J. J. Kwok, Sei Kwang Hahn, Seok Hyun Yun
      Abstract: Vaccines are commonly administered by injection using needles. Although transdermal microneedles are less invasive promising alternatives, needle‐free topical vaccination without involving physical damage to the natural skin barrier is still sought after as it can further reduce needle‐induced anxiety and is simple to administer. However, this long‐standing goal has been elusive since the intact skin is impermeable to most macromolecules. Here, we show an efficient, noninvasive transdermal vaccination by employing two key innovations: the use of hyaluronan (HA) as vaccine carriers and non‐ablative laser adjuvants. Conjugates of a model vaccine ovalbumin (OVA) and HA—HA–OVA conjugates—induced more effective maturation of dendritic cells in vitro, compared to OVA. Following topical administration in the skin, HA–OVA conjugates penetrated into the epidermis and dermis in murine and porcine skins, as revealed by intravital microscopy and fluorescence assay. Topical administration of HA‐OVA conjugates significantly elevated both humoral and mucosal antibodies, with peak levels at four weeks. An OVA challenge at week eight elicited strong immune‐recall responses. With pretreatment of the skin using non‐ablative fractional laser beams as adjuvant, strong immunization was achieved with much reduced doses of HA–OVA (1 mg kg–1 OVA). Our results demonstrate the potential of the noninvasive patch‐type transdermal vaccination platform. A highly effective, noninvasive transdermal vaccination system is demonstrated using laser adjuvant and hyaluronan (HA) nanocarrier. Topically applied HA–OVA conjugates penetrate the intact skin efficiently and establish strong humoral (IgG) and mucosal (IgA) responses at ovalbumin (OVA) doses as small as 1 mg kg−1 in mice. The transdermal immunization efficiency is higher than intramuscular injection of OVA and similar to intramuscular injection of HA–OVA.
      PubDate: 2016-02-01T02:56:30.505687-05:
      DOI: 10.1002/adfm.201504879
       
  • Multigaps Embedded Nanoassemblies Enhance In Situ Raman Spectroscopy for
           Intracellular Telomerase Activity Sensing
    • Authors: Liguang Xu; Sen Zhao, Wei Ma, Xiaoling Wu, Si Li, Hua Kuang, Libing Wang, Chuanlai Xu
      Abstract: The highly sensitive and quantitative biodetection of intracellular telomerase is challenging. A DNA‐driven nanoparticle self‐assembling pyramid encoding a Raman reporter (Cy5) is reported that detects telomerase in live cells. In the presence of the target, the telomerase primer is extended and the inner DNA chain is replaced, leading to the reduction in the surface‐enhanced Raman scattering (SERS) signal and the simultaneous recovery of the fluorescent signal. The SERS signal has a linear range for the detection of telomerase in situ of 1 × 10–14 to 5 × 10–11 IU, with a limit of detection of 6.2 × 10–15 IU. The fluorescent signal is used to confirm the intracellular telomerase activity, demonstrating the efficacy of the designed pyramid probe. This biosensing strategy provides a reliable and ultrasensitive protocol for the quantification of biomarkers in living cells. In situ distinguishing between cancerous and normal cells can easily be carried out using Raman spectroscopy to determine the telomerase activity within the cells. The pyramid‐like structures are used for sensing intracellular telomerase activity in live cells without complicated extraction procedures. The analytical ability of this method is more sensitive than that of fluorescence assays.
      PubDate: 2016-02-01T02:56:23.187439-05:
      DOI: 10.1002/adfm.201504587
       
  • Strain Modulation in Graphene/ZnO Nanorod Film Schottky Junction for
           Enhanced Photosensing Performance
    • Authors: Shuo Liu; Qingliang Liao, Shengnan Lu, Zheng Zhang, Guangjie Zhang, Yue Zhang
      Abstract: Strain modulation in flexible semiconductor heterojunctions has always been considered as an effective way to modulate the performance of nanodevices. In this work, a graphene/ZnO nanorods film Schottky junction has been constructed. It shows considerable responsivity and fast on‐off switch to the UV illumination. Through utilizing the piezopotential induced by the atoms displacement in ZnO under the compressive strain, 17% enhanced photosensing property is achieved in this hybrid structure when applying −0.349% strain. This performance improvement can be ascribed to the Schottky barrier height modification by the strain‐induced piezopotential, which results in the facilitation of electron–hole separation in the graphene/ZnO interface. An energy band principle as well as a finite element analysis is proposed to understand this phenomenon. The results here provide a facile approach to boost the optoelectronic performance of graphene/ZnO heterostructure, which may also be applied to other Schottky junction based hybrid devices. Strain modulation in graphene/ZnO film Schottky junction is investigated. Utilizing the piezopotential generated in ZnO under compressive strain, 17% enhanced photosensing performance is achieved when applying −0.349% strain. The results here provide a facile approach to boost the optoelectronic performance of graphene/ZnO heterostructures, which may also be applied to other Schottky junction‐based hybrid devices.
      PubDate: 2016-01-29T05:50:53.929598-05:
      DOI: 10.1002/adfm.201503905
       
  • Large Area Artificial Spin Ice and Anti‐Spin Ice Ni80Fe20
           Structures: Static and Dynamic Behavior
    • Abstract: Artificial spin ice has been the subject of extensive investigation in the last few years due to advances in nanotechnology and characterization techniques. So far, most of the studies have been limited to local probe of small area magnetic elements due to limitations with lithographic techniques used. In this study, large area spin ice and anti‐spin ice Ni80Fe20 structures with three lattice configurations have been fabricated using deep ultraviolet lithography at 193 nm exposure wavelength. The static and dynamic properties are systematically characterized using vibrating sample magnetometer, magnetic force microscopy, and broadband ferromagnetic resonance spectroscopy. Intriguing static and dynamic behaviors are observed due to the geometrical arrangement of the nanomagnets in the lattice. When the nanomagnets are saturated at high field, multiple resonance peaks whose frequencies are strongly dependent on the orientation of the applied magnetic field are observed. The experimental results are in qualitative agreement with the micromagnetic simulations. These findings may find application in the design of magnetically controlled tunable microwave filters. The nanofabrication of large area artificial spin ice and anti‐spin ice structures by using deep ultraviolet lithography at 193 nm exposure wavelength is reported. The method allows to arrange the magnetic elements in three different lattice configurations. It is demonstrated that the static and dynamic behaviors of these structures are highly tunable. The results are validated using micromagnetic simulations.
      PubDate: 2016-01-29T05:50:49.406705-05:
      DOI: 10.1002/adfm.201505165
       
  • An Interface Engineered Multicolor Photodetector Based on
           n‐Si(111)/TiO2 Nanorod Array Heterojunction
    • Authors: Tao Ji; Qian Liu, Rujia Zou, Yangang Sun, Kaibing Xu, Liwen Sang, Meiyong Liao, Yasuo Koide, Li Yu, Junqing Hu
      Abstract: A multicolor photodetector based on the heterojunction of n‐Si(111)/TiO2 nanorod arrays responding to both ultraviolet (UV) and visible light is developed by utilizing interface engineering. The photodetector is fabricated via a consecutive process including chemical etching, magnetron sputtering, hydrothermal growth, and assembling. Under a small reverse bias (from 0 to ≈−2 V), only the photogenerated electrons in TiO2 are possible to tunnel through the low barrier of ΔEC, and the device only responses to UV light; as the reverse bias increases, the photogenerated holes in Si also begin to tunnel through the high barrier of ΔEV. As a result, the device is demonstrated to have the capacity to detect both UV and visible lights, which is useful in the fields of rapid detection and multicolor imaging. It has been also observed that the crystal orientation of Si affects the characteristics of bias‐controlled spectral response of the n‐Si/TiO2 heterojunctions. A multicolor photodetector based on a n‐Si(111)/TiO2 nanorod array heterojunction is developed by utilizing interface engineering, responding to both ultraviolet and visible light by changing the applied bias.
      PubDate: 2016-01-29T05:50:43.481967-05:
      DOI: 10.1002/adfm.201504464
       
  • Toward Ambient Armor: Can New Materials Change Longstanding Concepts of
           Projectile Protection?
    • Authors: Pingwei Liu; Michael S. Strano
      Abstract: Materials that protect against the high strain rate loading of a projectile have traditionally been constrained by their use on the target of protection. Here the possibility of new materials, particularly carbon nanocomposites, are explored for projectile protection removed off of the target and placed along the trajectory at an intermediate location. A mathematical model of such Ambient Armor (AA) separates the impact, capture, and energy dissipation of an incident projectile into each of three stages, respectively. A distinct scaling of the projectile to composite area ratio and areal density ratio is derived for a given requisite stopping distance. As an example, the model predicts that a 1 g and 800 m s21 small projectile could be decelerated to 3 m s21 within 6–9 m using a 2.34 3 104 layer monolayer graphene nanocomposite at 0.02 volume fraction. For larger projectiles with higher kinetic energy, a tandem system using a second composite body with the specified area density is explored with the idea of making the projectile gyroscopically unstable for rapid deceleration and subsequent interception. Off target reinforcement or AA may in general allow for the exploration of a broader range of material properties for projectile protection. Ambient Armor (AA) concept is demonstrated mathematically to protect against high velocity impact of projectiles in an off‐target way. Semi‐infinite graphene/polymer nanocomposite with a multilayer structure can be used as a free body in the AA system for projectile capture and energy dissipation via air drag without penetration.
      PubDate: 2016-01-12T12:32:56.288524-05:
      DOI: 10.1002/adfm.201503915
       
  • Mobility Enhancement in Solution‐Processed Transparent Conductive
           Oxide TFTs due to Electron Donation from Traps in High‐k Gate
           Dielectrics
    • Authors: Andre Zeumault; Vivek Subramanian
      Abstract: High‐mobility ZnO thin films are deposited onto solution‐processed ZrO2 dielectrics in order to investigate the large differences between experimental field‐effect mobility values obtained when transparent conductive oxide (TCO) materials are deposited onto high‐k dielectrics as opposed to thermally grown SiO2. Through detailed electrical characterization, the mobility enhancement in ZnO is correlated to the presence of electron traps in ZrO2 serving to provide an additional source of electrons to the ZnO. Furthermore, as a consequence of the general tendency for solution‐processed high‐k dielectrics to exhibit similar behavior, the broad applicability is suggested to other TCO/high‐k material combinations in agreement with experimental observations. Zinc oxide (ZnO) thin‐films are deposited onto solution‐processed zirconia dielectrics to investigate differences in mobility obtained when transparent conductive oxide semiconductors are deposited onto high‐k dielectrics as opposed to thermally‐grown silica. Through detailed electrical characterization, the mobility enhancement in ZnO is correlated with the presence of electron traps in zirconia – providing an additional source of electrons to the ZnO.
      PubDate: 2016-01-12T12:32:50.588652-05:
      DOI: 10.1002/adfm.201503940
       
  • Mechanical Restoration of Damaged Polymer Films by
           “Repair‐and‐Go”
    • Abstract: A microencapsulation and nanoparticle deposition technique, termed “repair‐and‐go,” is employed for inducing mechanical restoration of damaged polymer films. In “repair‐and‐go,” polymer‐stabilized emulsion droplets, containing surface‐functionalized SiO2 nanoparticles, traverse a substrate and deposit their nanoparticle contents selectively into the damaged regions. Surface‐oxidized poly(dimethylsiloxane) is employed as the substrate, and dynamic mechanical analysis reveals the enhanced mechanical properties of the film following nanoparticle deposition. Healing efficiency is optimal when using thinner test substrates, repeated deposition cycles, and functional SiO2 nanoparticles that afford access to postdeposition curing. Microencapsulation and nanoparticle deposition are combined in a materials healing technique termed “repair‐and‐go”. It has been shown that polymer‐stabilized oil droplets can traverse a substrate and deposit nanoparticles into the damaged regions of a polymer film. Dynamic mechanical analysis demonstrated effective restoration of mechanical properties through assessment of film stiffness.
      PubDate: 2016-01-08T11:48:15.281184-05:
      DOI: 10.1002/adfm.201503947
       
  • Transparent Electrodes: Electrohydrodynamic NanoDrip Printing of High
           Aspect Ratio Metal Grid Transparent Electrodes (Adv. Funct. Mater. 6/2016)
           
    • Authors: Julian Schneider; Patrik Rohner, Deepankur Thureja, Martin Schmid, Patrick Galliker, Dimos Poulikakos
      Pages: 805 - 805
      Abstract: D. Poulikakos and co‐workers explain on page 833 how electro‐hydrodynamic NanoDrip printing enables the fully additive fabrication of high‐aspect‐ratio nanostructures. Tiny gold nanoparticle ink droplets are ejected from a much larger nozzle to build up gold nanowall grids that show impressive optoelectronic properties and have great potential as transparent electrodes in display and solar cell applications.
      PubDate: 2016-02-08T07:01:12.517051-05:
      DOI: 10.1002/adfm.201670034
       
  • Aggregation‐Induced Emission: Synthesis of Imidazole‐Based
           AIEgens with Wide Color Tunability and Exploration of their Biological
           Applications (Adv. Funct. Mater. 6/2016)
    • Authors: Zhegang Song; Weijie Zhang, Meijuan Jiang, Herman H. Y. Sung, Ryan T. K. Kwok, Han Nie, Ian D. Williams, Bin Liu, Ben Zhong Tang
      Pages: 806 - 806
      Abstract: A series of aggregation‐induced emission (AIE) luminogens (AIEgens) based on imidazole‐cored molecular rotors are designed and synthesized by B. Liu, B. Z. Tang, and co‐workers. By selecting appropriate acceptors, these AIEgens have emission colors covering the whole visible spectrum. On page 824, they are shown to exhibit organelle specificity and are applied for mitochondria imaging. Moreover, due to the antifungal characteristics of imidazole moiety, the imidazole derivatives are demonstrated for the inhibition of yeast growth and the evaluation of antifungal activity.
      PubDate: 2016-02-08T07:01:11.803542-05:
      DOI: 10.1002/adfm.201670035
       
  • Contents: (Adv. Funct. Mater. 6/2016)
    • Pages: 807 - 813
      PubDate: 2016-02-08T07:01:13.303268-05:
      DOI: 10.1002/adfm.201670036
       
  • Nanostructures: Enhanced Differentiation of Human Embryonic Stem Cells
           Toward Definitive Endoderm on Ultrahigh Aspect Ratio Nanopillars (Adv.
           Funct. Mater. 6/2016)
    • Authors: Camilla Holzmann Rasmussen; Paul M. Reynolds, Dorthe Roenn Petersen, Mattias Hansson, Robert M. McMeeking, Martin Dufva, Nikolaj Gadegaard
      Pages: 814 - 814
      Abstract: N. Gadegaard and co‐workers report on page 815 a nanofabricated thermoplastic substrate with ultra‐high aspect ratio nanopillars. This substrate, formed via injection molding, is used to enhance the differentiation of human embryonic stem cells. The nanostructured surface results in a softer substrate, which mimics the natural extracellular environment.
      PubDate: 2016-02-08T07:01:09.542589-05:
      DOI: 10.1002/adfm.201670038
       
  • Carbon Nanotubes: Modulation of Carbon Nanotube's Perturbation to the
           Metabolic Activity of CYP3A4 in the Liver (Adv. Funct. Mater. 6/2016)
    • Authors: Yi Zhang; Yabin Wang, Aijuan Liu, Sherry Li Xu, Bin Zhao, Yi Zhang, Hanfa Zou, Wenyi Wang, Hao Zhu, Bing Yan
      Pages: 980 - 980
      Abstract: On page 841, multiwalled carbon nanotubes are chemically modified by B. Yan and co‐workers to afford them biocompatible or medicinally beneficial properties. In the image, the chemical modifications of the multiwalls of carbon nanotubes are likened to the five lines of a musical stave: together they make harmonic music instead of harm. Image drawn by Joshua Stokes (Biomedical Communications, St. Jude Children's Research Hospital, Memphis, TN).
      PubDate: 2016-02-08T07:01:07.217751-05:
      DOI: 10.1002/adfm.201670039
       
  • Solution‐Processable Ultrathin Black Phosphorus as an Effective
           Electron Transport Layer in Organic Photovoltaics
    • Abstract: 2D van der Waals crystals, possessing excellent electronic and physical properties, have been intriguing building blocks for organic optoelectronic devices. Most of the 2D materials are served as hole transport layers in organic devices. Here,it is reported that solution exfoliated few layers black phosphorus (BP) can be served as an effective electron transport layer (ETL) in organic photovoltaics (OPVs) for the first time. The power conversion efficiencies (PCEs) of the BP‐incorporated OPVs can be improved to 8.18% in average with the relative enhancement of 11%. The incorporation of BP flakes with the optimum thickness of ≈10 nm can form cascaded band structure in OPVs, which can facilitate electron transport and enhance the PCEs of the devices. This study opens an avenue in using solution exfoliated BP as a highly efficient ETL for organic optoelectronics. Solution‐processable black phosphorus (BP) is served as an effective electron transport layer in organic solar cells for the first time. The efficiencies of the ­BP‐incorporated devices can be relatively improved for 11% due to the formation of cascaded band structure that can facilitate electron transport in the devices. This study broadens the application of BP in electronics devices.
      PubDate: 2015-12-28T04:37:05.894728-05:
      DOI: 10.1002/adfm.201503273
       
  • Enhanced Differentiation of Human Embryonic Stem Cells Toward Definitive
           Endoderm on Ultrahigh Aspect Ratio Nanopillars
    • Authors: Camilla Holzmann Rasmussen; Paul M. Reynolds, Dorthe Roenn Petersen, Mattias Hansson, Robert M. McMeeking, Martin Dufva, Nikolaj Gadegaard
      Pages: 815 - 823
      Abstract: Differentiation of human embryonic stem cells is widely studied as a potential unlimited source for cell replacement therapy to treat degenerative diseases such as diabetes. The directed differentiation of human embryonic stem cells relies mainly on soluble factors. Although, some studies have highlighted that the properties of the physical environment, such as substrate stiffness, affect cellular behavior. Here, mass‐produced, injection molded polycarbonate nanopillars are presented, where the surface mechanical properties, i.e., stiffness, can be controlled by the geometric design of the ultrahigh aspect ratio nanopillars (stiffness can be reduced by 25.0003). It is found that tall nanopillars, yielding softer surfaces, significantly enhance the induction of definitive endoderm cells from pluripotent human embryonic stem cells, resulting in more consistent differentiation of a pure population compared to planar control. By contrast, further differentiation toward the pancreatic ­endoderm is less successful on “soft” pillars when compared to “stiff” pillars or control, indicating differential cues during the different stages of differentiation. To accompany the mechanical properties of the nanopillars, the concept of surface shear modulus is introduced to describe the characteristics of engineered elastic surfaces through micro or nanopatterning. This provides a framework whereby comparisons can be drawn between such materials and bulk elastomeric materials. A nanoengineered thermoplastic substrate with ultrahigh aspect ratio nano­pillars is manufactured by injection molding to mimic a soft cell matrix environment. The reduction in stiffness results in a significantly enhanced differentiation of human embryonic stem cells toward definitive endoderm.
      PubDate: 2015-12-15T13:15:12.079303-05:
      DOI: 10.1002/adfm.201504204
       
  • Synthesis of Imidazole‐Based AIEgens with Wide Color Tunability and
           Exploration of their Biological Applications
    • Authors: Zhegang Song; Weijie Zhang, Meijuan Jiang, Herman H. Y. Sung, Ryan T. K. Kwok, Han Nie, Ian D. Williams, Bin Liu, Ben Zhong Tang
      Pages: 824 - 832
      Abstract: Research on aggregation‐induced emission (AIE) has become increasingly popular recently and various AIE luminogens (AIEgens) have been developed based on tetraphenylethene, hexaphenylsilole, distyrylanthracene, tetraphenylpyrazine, etc. However, facile tuning of the AIEgen emissions in a wide range remains challenging. Herein, a novel series of AIEgens is reported, based on imidazole‐cored molecular rotors, with facile synthesis and emission colors covering the whole visible spectrum. Moreover, these imidazole derivatives exhibit biological functions unique among the AIEgens, including mitochondria‐specific imaging and antifungal activity. Benefiting from the easy preparation and the tunable emission, the imidazole derivatives are expected to not only diversify the family of AIEgens but also enrich their biological applications. A series of imidazole derivatives is designed with a facile synthesis and wide color tunability. With an imidazole core as the stator and aromatic rings as the rotors, all the compounds show typical aggregation‐induced emission (AIE) characteristics. Moreover, these imidazole‐based AIE luminogens (AIEgens) exhibit unique biological functions, including mitochondria‐specific imaging and antifungal activity.
      PubDate: 2015-12-17T10:51:59.789286-05:
      DOI: 10.1002/adfm.201503788
       
  • Electrohydrodynamic NanoDrip Printing of High Aspect Ratio Metal Grid
           Transparent Electrodes
    • Authors: Julian Schneider; Patrik Rohner, Deepankur Thureja, Martin Schmid, Patrick Galliker, Dimos Poulikakos
      Pages: 833 - 840
      Abstract: The transparent conducting electrode is an essential component in many contemporary and future devices, ranging from displays to solar cells. Fabricating transparent electrodes requires a balancing act between sufficient electrical conductivity and high light transmittance, both affected by the involved materials, fabrication methodology, and design. While metal films possess the highest conductivity at room temperature, a decent optical transmittance can only be achieved with ultrathin films. Structuring the metal into optically invisible nanowires has been shown to be promising to complement or even substitute transparent conductive oxides as dominant transparent electrode material. Here the out‐of‐plane fabrication capability of the recently developed method of electrohydrodynamic NanoDrip printing to pattern gold and silver nanogrids with line widths from 80 to 500 nm is demonstrated. This fully additive process enables the printing of high aspect ratio nanowalls and by that significantly improves the electrical performance, while maintaining the optical transmittance at a high level. Metal grid transparent electrodes optimized for low sheet resistances (8 Ω sq−1 at a relative transmittance of 94%) as well as optimized for high transmittance (97% at a sheet resistance of 20 Ω sq−1) are reported, which can be tailored on demand for the use in various applications. Electrohydrodynamic NanoDrip printing is used to pattern gold and silver nanowalls into high performance metal grid transparent electrodes. The out‐of‐plane capability of this additive process enables the printing of nanowall aspect ratios up to 7, greatly improving the electrical performance, while maintaining the exceptional optical transmittance.
      PubDate: 2015-12-15T13:33:22.344634-05:
      DOI: 10.1002/adfm.201503705
       
  • Modulation of Carbon Nanotubes' Perturbation to the Metabolic Activity of
           CYP3A4 in the Liver
    • Authors: Yi Zhang; Yabin Wang, Aijuan Liu, Sherry Li Xu, Bin Zhao, Yi Zhang, Hanfa Zou, Wenyi Wang, Hao Zhu, Bing Yan
      Pages: 841 - 850
      Abstract: The liver plays an important role in metabolizing foreign materials, such as drugs. The high accumulation of carbon nanotubes and other hydrophobic nanoparticles in the liver has raised concerns that nanoparticles may interfere with liver metabolic function. We report here that carbon nanotubes enter hepatic cells after intravenous introduction and interact with CYP enzymes, including CYP3A4. Surface chemical modifications alter the carbon nanotubes' interactions with CYP450 enzymes in human liver microsomes. They enhance, inhibit, or have no effect on the enzymatic function of CYP3A4. Using a cheminformatics analysis, certain chemical structures are identified on the surface of the carbon nanotubes that induce an enzyme inhibitory effect or prevent disruption of CYP3A4 enzymes. The high accumulation of multiwalled carbon nanotubes (MWCNTs) in the liver results in their internalization in hepatic cells and perturbations to CYP enzymes, including CYP3A4. Surface chemical modifications on MWCNTs cause enhancement, inhibition, or no effect in CYP3A4 activity. Computational analysis identifies chemical structures on the surface modifications that induce CYP3A4 inhibition or prevent its perturbation.
      PubDate: 2015-12-21T08:49:38.788845-05:
      DOI: 10.1002/adfm.201504182
       
  • Diving–Surfacing Smart Locomotion Driven by a CO2‐Forming
           Reaction, with Applications to Minigenerators
    • Authors: Lina Zhang; Mengmeng Song, Meng Xiao, Feng Shi
      Pages: 851 - 856
      Abstract: Harvesting energy from environment has attracted increasing attention for its potential applications in fabricating minigenerator. However, most studies in the fabrication of mini‐ or nanogenerators are based on the concept of piezoelectricity or triboelectrification while few of the reports paid attention to the classical theory of Faraday's law. Herein, a pH responsive smart surface is combined with the reaction between CaCO3 and HCl to develop a new minigenerator, which can convert mechanical energy generated from the chemical reaction into electrical energy through cutting magnetic lines with moving conductive lines. The conductive lines are connected with a smart device consisting of a pH‐responsive cube, a hydrophobic cube, and a quartz cell window; the device can perform diving‐surfacing cycled motions with an intelligent initiation through the adjustment of the solution. The device can surface through gathering CO2 bubbles from the reaction between CaCO3 and HCl and dive by releasing the bubbles on the water/air interface. Moreover, the results demonstrate that the inert CO2 was nonhazardous to the smart surfaces, which is meaningful for durable electricity generation. A functionally cooperative smart device is designed to perform cycling diving/surfacing motions with a pH‐responsive initiation. By connecting the device to an electrochemical workstation through a conductive line in a parallel magnetic field, chemical energy of reactant is converted to electricity through mechanical form. Moreover, carbon dioxide does little harm on the device surfaces, indicating sustainability of electricity harvesting process.
      PubDate: 2015-12-07T06:43:29.66693-05:0
      DOI: 10.1002/adfm.201504305
       
  • Physically Crosslinked Biocompatible Silk‐Fibroin‐Based
           Hydrogels with High Mechanical Performance
    • Authors: Kunyuan Luo; Yuhong Yang, Zhengzhong Shao
      Pages: 872 - 880
      Abstract: Developing hydrogel which combines superior mechanical performance and biocompatibility attracts researchers’ attention in recent years. Here, a novel biocompatible hydrogel with excellent mechanical performance, comprised of regenerated silk fibroin (RSF) and hydroxypropyl methyl cellulose (HPMC), is fabricated by simply mixing and heating. It is found that both of compressive modulus and tensile modulus of the optimal RSF/HPMC hydrogel are over 1.0 MPa. Meanwhile, the break energy is up to 3500 J m−2, which is higher than that of some natural elastomers, such as cartilage, cork, and skin. The investigation of gelation mechanism reveals that more uniformly dispersed crosslinks dominated by smaller β‐sheet structures, which is attributed to the synergistic effects of hydrogen bonding and hydrophobic interaction between HPMC and RSF molecules, contribute to the superior mechanical performance of RSF/HPMC hydrogel. This biocompatible high strength silk protein based hydrogel diversifies the robust hydrogels and holds a great promise as candidates for load‐bearing materials in biomedical field. A biocompatible and mechanically strong hydrogel, based on silk fibroin and a kind of cellulose ether derivative, is developed. The preparation process is very simple and green. In the best case, the silk based hydrogel exhibits both tensile and compressive modulus over 1.0 MPa while break energy over 3500 J m−2.
      PubDate: 2015-12-23T09:40:35.565097-05:
      DOI: 10.1002/adfm.201503450
       
  • Facile Synthesis of Highly Efficient Lepidine‐Based Phosphorescent
           Iridium(III) Complexes for Yellow and White Organic Light‐Emitting
           Diodes
    • Pages: 881 - 894
      Abstract: Highly efficient lepidine‐based phosphorescent iridium(III) complexes with pentane‐2,4‐dione or triazolpyridine as ancillary ligands have been designed and prepared by a newly developed facile synthetic route. Fluorine atoms and trifluoromethyl groups have been introduced into the different positions of ligand, and their influence on the photophysical properties of complexes has been investigated in detail. All the triazolpyridine‐based complexes display the blueshifted dual‐peak emission compared to the pentane‐2,4‐dione‐based ones with a broad single‐peak emission. The complexes show emission with broad full width at half maximum (FWHM) over 100 nm, and the emissions are ranges from greenish–yellow to orange region with the absolute quantum efficiency (ΦPL) of 0.21–0.92 in solution, i.e., ΦPL = 0.92 (18), which is the highest value among the reported neutral yellow iridium(III) complexes. Furthermore, high‐performance yellow and complementary‐color‐based white organic light‐emitting diodes (OLEDs) have been fabricated. The FWHMs of the yellow, greenish–yellow OLEDs are in the range of 94–102 nm, which are among the highest values of the reported yellow or greenish–yellow‐emitting devices without excimer emission. The maximum external quantum efficiency of monochrome OLEDs can reach 24.1%, which is also the highest value among the reported yellow or greenish–yellow devices. The color rendering indexes of blue and complementary yellow‐based white OLED is as high as 78. Excellent fluorine‐containing lepidine‐based phosphorescent iridium(III) complexes with pentane‐2,4‐dione or triazolpyridine as ancillary ligands are designed and prepared by a facile synthetic route. These complexes exhibit greenish‐yellow to yellow emission with high phosphorescent quantum yields up to 0.92 and wide emission band with FWHM over 100 nm, which is used for fabricating highly efficient yellow and white organic light‐emitting diodes.
      PubDate: 2015-12-21T08:51:11.220453-05:
      DOI: 10.1002/adfm.201503826
       
  • Visualization of Current and Mapping of Elements in Quantum Dot Solar
           Cells
    • Authors: J. Scott Niezgoda; Amy Ng, Jonathan D. Poplawsky, James R. McBride, Stephen J. Pennycook, Sandra J. Rosenthal
      Pages: 895 - 902
      Abstract: The delicate influence of properties such as high surface state density and organic–inorganic boundaries on the individual quantum dot electronic structure complicates pursuits toward forming quantitative models of quantum dot thin films ab initio. This report describes the application of electron beam‐induced current (EBIC) microscopy to depleted‐heterojunction colloidal quantum dot photovoltaics (DH‐CQD PVs), a technique which affords one a “map” of current production within the active layer of a PV device. The effects of QD sample size polydispersity as well as layer thickness in CQD active layers as they pertain to current production within these PVs are imaged and explained. The results from these experiments compare well with previous estimations, and confirm the ability of EBIC to function as a valuable empirical tool for the design and betterment of DH‐CQD PVs. Lastly, extensive and unexpected PbS QD penetration into the mesoporous TiO2 layer is observed through imaging of device cross sections by energy‐dispersive X‐ray spectroscopy combined with scanning transmission electron microscopy. The possible effects of this finding are discussed and corroborated with the EBIC studies on similar devices. Electron‐beam‐induced current serves Quantum Dot Solar Cells to visualize current collection within the active layer of multiple quantum dot solar cell devices. Furthermore, scanning transmission electron microscopy elemental mapping is used to reveal an unexpected penetration depth of quantum dots within the mesoporous oxide layer used in these solar cells.
      PubDate: 2015-12-17T10:51:54.132769-05:
      DOI: 10.1002/adfm.201503839
       
  • High‐Performance Mesostructured Organic Hybrid Pseudocapacitor
           Electrodes
    • Pages: 903 - 910
      Abstract: The electrodes of a hybrid electrochemical capacitor which utilize the quinone (Q)‐hydroquinone (QH2) couple, a prototypical organic redox system known to provide fast and reversible proton‐coupled electron‐transfer reactions, are deterministically mesostructured via a colloidal templating strategy to provide good ion and electron transport pathways, enabling a high rate performance. Specifically, a conducting polymer, polypyrrole (PPy), is functionalized with a pseudocapacitive material, a Q/QH2‐containing catechol derivative, by noncovalent interactions. The mesostructure of this hybrid material is formed into an ordered 3D porous structure by a polystyrene colloidal crystal template‐assisted electrosynthesis. The catechol derivative is sufficiently bound to the PPy through noncovalent interactions to provide a volumetric capacitance as high as ≈130 F cm−3 and a capacitance retention of ≈75% over 10 000 charging/discharging cycles. When compared with a randomly structured electrode, the deterministically structured electrode exhibits an improved rate performance due to the mesostructure facilitated electron and ion transport. High‐performance mesostructured organic pseudocapacitive electrodes are formed via a straightforward one‐step electrosynthesis. Mesostructuring of the electrodes offers good electron and ion transport pathways, leading to excellent rate performance. The catechol derivative adsorbed on the surface of the mesostructured scaffold provides larger volumetric capacitance and long cycle life.
      PubDate: 2015-12-17T10:51:02.443131-05:
      DOI: 10.1002/adfm.201504307
       
  • Facile Spraying Synthesis and High‐Performance Sodium Storage of
           Mesoporous MoS2/C Microspheres
    • Authors: Yanying Lu; Qing Zhao, Ning Zhang, Kaixiang Lei, Fujun Li, Jun Chen
      Pages: 911 - 918
      Abstract: A facile one‐step spraying synthesis of MoS2/C microspheres and their enhanced electrochemical performance as anode of sodium‐ion batteries is reported. An aerosol spraying pyrolysis without any template is employed to synthesize MoS2/C microspheres, in which ultrathin MoS2 nanosheets (≈2 nm) with enlarged interlayers (≈0.64 nm) are homogeneously embedded in mesoporous carbon microspheres. The as‐synthesized mesoporous MoS2/C microspheres with 31 wt% carbon have been applied as an anode material for sodium ion batteries, demonstrating long cycling stability (390 mAh g−1 after 2500 cycles at 1.0 A g−1) and high rate capability (312 mAh g−1 at 10.0 A g−1 and 244 mAh g−1 at 20.0 A g−1). The superior electrochemical performance is due to the uniform distribution of ultrathin MoS2 nanosheets in mesoporous carbon frameworks. This kind of structure not only effectively improves the electronic and ionic transport through MoS2/C microspheres, but also minimizes the influence of pulverization and aggregation of MoS2 nanosheets during repeated sodiation and desodiation. Mesoporous MoS2/C microspheres with ultrathin MoS2 nanosheets embedded in mesoporous carbon microspheres—fabricated by a facile template‐free aerosol spray method—can effectively suppress the volume variation and particle aggregation of MoS2 during prolonged sodiation/desodiation process and present superior sodium storage performance.
      PubDate: 2015-12-23T09:40:07.609619-05:
      DOI: 10.1002/adfm.201504062
       
  • Amorphous FeOOH Quantum Dots Assembled Mesoporous Film Anchored on
           Graphene Nanosheets with Superior Electrochemical Performance for
           Supercapacitors
    • Authors: Jiaqi Liu; Mingbo Zheng, Xiaoqin Shi, Haibo Zeng, Hui Xia
      Pages: 919 - 930
      Abstract: Previous research on iron oxides/hydroxides has focused on the crystalline rather than the amorphous phase, despite that the latter could have superior electrochemical activity due to the disordered structure. In this work, a simple and scalable synthesis route is developed to prepare amorphous FeOOH quantum dots (QDs) and FeOOH QDs/graphene hybrid nanosheets. The hybrid nanosheets possess a unique heterostructure, comprising a continuous mesoporous FeOOH nanofilm tightly anchored on the graphene surface. The amorphous FeOOH/graphene hybrid nanosheets exhibit superior pseudocapacitive performance, which largely outperforms the crystalline iron oxides/hydroxides‐based materials. In the voltage range between −0.8 and 0 V versus Ag/AgCl, the amorphous FeOOH/graphene composite electrode exhibits a large specific capacitance of about 365 F g−1, outstanding cycle performance (89.7% capacitance retention after 20 000 cycles), and excellent rate capability (189 F g−1 at a current density of 128 A g−1). When the lower cutoff voltage is extended to −1.0 and −1.25 V, the specific capacitance of the amorphous FeOOH/graphene composite electrode can be increased to 403 and 1243 F g−1, respectively, which, however, compromises the rate capability and cycle performance. This work brings new opportunities to design high‐performance electrode materials for supercapacitors, especially for amorphous oxides/hydroxides‐based materials. Amorphous FeOOH quantum dots (QDs) and amorphous FeOOH QDs/functualized graphene sheet (FGS) hybrid nanosheets have been synthesized by a novel, facile, and scalable chemical method. The amorphous FeOOH/FGS hybrid nanosheets exhibit superior supercapacitive performance compared to crystalline iron oxide/hydroxide‐based electrode materials, indicating the potential applicability of amorphous iron oxides/hydroxides as advanced electrode materials in supercapacitors with large energy and power density.
      PubDate: 2015-12-16T13:37:46.234471-05:
      DOI: 10.1002/adfm.201504019
       
  • Unusual Aspects of Supramolecular Networks: Plasticity to Elasticity,
           Ultrasoft Shape Memory, and Dynamic Mechanical Properties
    • Authors: Guogao Zhang; Qian Zhao, Weike Zou, Yingwu Luo, Tao Xie
      Pages: 931 - 937
      Abstract: Supramolecular bonds have been widely used for designing polymers because of their reversible nature. In contrast, utilization of their dynamic equilibrium nature to access materials of unusual mechanical properties has been poorly explored. Taking full advantage of this latter attribute requires the design of polymer networks with high contents of supramolecular bonds. In this work, polymer networks with high contents of self‐complementary hydrogen bonds (ureidopyrimidinone) are synthesized using thiol–acrylate click addition. The excellent tunability of the network allows a range of intriguing mechanical properties to be achieved including the transition from plasticity to elasticity, ultrasoft shape memory polymer, strong strain rate dependence, and high mechanical damping. Materials with such versatile dynamic behaviors may open up a range of new applications. Polymer networks containing both supramolecular and covalent crosslinks are synthesized by thiol–acrylate click reaction. By tuning the ratio of these two kinds of crosslinks, the network undergoes a transition from plasticity to elasticity. In the elasticity region, the materials show several unusual mechanical properties, including strong strain rate dependence, ultrasoft shape memory, and superior mechanical damping.
      PubDate: 2015-12-23T09:40:11.88424-05:0
      DOI: 10.1002/adfm.201504028
       
  • Natural Hematite for Next‐Generation Solid Oxide Fuel Cells
    • Authors: Yan Wu; Chen Xia, Wei Zhang, Xiang Yang, Zheng Yu Bao, Jiao Jun Li, Bin Zhu
      Pages: 938 - 942
      Abstract: Natural hematite ore is used as a novel electrolyte material for advanced solid oxide fuel cells (SOFCs). This hematite‐based system exhibits a maximum power density of 225 mW cm−2 at 600 °C and reaches 467 mW cm−2 when the hematite is mixed with perovskite‐structured La0.6Sr0.4Co0.2Fe0.8O3–δ. These results demonstrate that natural materials for next‐generation SOFCs can influence the multiutilization of natural resources, thereby affecting the environment and energy sustainability. The natural hematite explored in this work for advanced solid oxide fuel cells (SOFCs) indicates new‐generation affordable SOFC products. This design and processing concept can be easily extended to other systems, and these natural mineral materials with desired functions and properties hold great promise for potential applications in the fields of energy and environmental science.
      PubDate: 2015-12-09T09:48:12.205709-05:
      DOI: 10.1002/adfm.201503756
       
  • Preparation of Secondary Mesopores in Mesoporous Anatase–Silica
           Nanocomposites with Unprecedented‐High Photocatalytic Degradation
           Performances
    • Authors: Weiyang Dong; Yaojun Sun, Weiming Hua, Youwei Yao, Guoshun Zhuang, Xinchun Lv, Qingwei Ma, Dongyuan Zhao
      Pages: 964 - 976
      Abstract: In this article, a simple and mild preparation of secondary pores are reported, for the first time, with uniform and tunable sizes (in a wide range of 0.9–4.8 nm) in the walls highly connecting the primary mesochannels in 3D mesopore networks. The uniform secondary pores are obtained by using ordered 2D hexagonal mesoporous anatase TiO2–SiO2 nanocomposites as precursors, NaOH as an etchant via an “extracting SiO2” approach. The strategy here adopts diluted NaOH solution, appropriate extraction temperature, and solid/liquid ratio. The photocatalytic degradation rates of Rhodamine B (0.347 min–1), Acid Red 1 (0.0487 min–1), microcystin–LR (1.66 min–1) on the representative resultant nanocomposite are very high, which are 4.63, 11.7, 1.84 times that of the precursor without secondary mesopores; even up to 18.9, 8.21, 4.66 times that of P25, respectively. These results clearly demonstrate that the secondary mesopores play an overwhelming role to the increments of activities. The mesoporous anatase–silica nanocomposites with secondary mesopores present unprecedented‐high degradation activities to various organic pollutants in the mesoporous metal‐oxides‐based materials reported up to now and are considerably stable and reusable. It is believed that the fundamentals in this study will provide new insights for rational design and preparation of 3D highly interconnected mesoporous metal‐oxides‐based materials with super‐high performances. Secondary mesopores with uniform and tunable sizes are prepared, for the first time, in the walls of ordered 2D hexagonal mesoporous anatase–silica nanocomposites connecting the primary mesochannels in 3D mesopore networks via a moderate, simple, and controllable “extracting SiO2” approach. The resultant nanocomposites with secondary mesopores present unprecedented‐high photocatalytic degradation activities to various organic pollutants in the mesoporous metal‐oxides‐based materials.
      PubDate: 2015-12-23T09:40:18.767247-05:
      DOI: 10.1002/adfm.201504001
       
 
 
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