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  Subjects -> CHEMISTRY (Total: 837 journals)
    - ANALYTICAL CHEMISTRY (48 journals)
    - CHEMISTRY (586 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (46 journals)
    - PHYSICAL CHEMISTRY (68 journals)

CHEMISTRY (586 journals)                  1 2 3 4 5 6 | Last

2D Materials     Hybrid Journal   (Followers: 6)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 32)
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: 10)
ACS Macro Letters     Full-text available via subscription   (Followers: 21)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 24)
ACS Nano     Full-text available via subscription   (Followers: 203)
ACS Photonics     Full-text available via subscription   (Followers: 6)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 11)
Acta Chemica Iasi     Open Access  
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 6)
Acta Chromatographica     Full-text available via subscription   (Followers: 10)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 11)
Advanced Functional Materials     Hybrid Journal   (Followers: 41)
Advanced Science Focus     Free   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 23)
Advances in Chemical Science     Open Access   (Followers: 9)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 15)
Advances in Drug Research     Full-text available via subscription   (Followers: 18)
Advances in Enzyme Research     Open Access  
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 13)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 16)
Advances in Nanoparticles     Open Access   (Followers: 13)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Science     Hybrid Journal   (Followers: 39)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 10)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
African Journal of Chemical Education     Open Access   (Followers: 1)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 1)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 5)
AMB Express     Open Access  
Ambix     Hybrid Journal   (Followers: 2)
American Journal of Applied Sciences     Open Access   (Followers: 30)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 84)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
American Journal of Chemistry     Open Access   (Followers: 19)
American Journal of Plant Physiology     Open Access   (Followers: 10)
American Mineralogist     Full-text available via subscription   (Followers: 7)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 22)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 126)
Annales UMCS, Chemia     Open Access   (Followers: 2)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access  
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 1)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 2)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 6)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 11)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 12)
Anti-Infective Agents     Hybrid Journal   (Followers: 1)
Antiviral Chemistry and Chemotherapy     Full-text available via subscription  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
Applied Spectroscopy     Full-text available via subscription   (Followers: 15)
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: 4)
Autophagy     Full-text available via subscription   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 6)
Biochemistry     Full-text available via subscription   (Followers: 148)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 4)
BioChip Journal     Hybrid Journal   (Followers: 1)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 4)
Bioinspired Materials     Open Access  
Biointerface Research in Applied Chemistry     Open Access   (Followers: 1)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 30)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 24)
Bioorganic Chemistry     Hybrid Journal   (Followers: 5)
Biopolymers     Hybrid Journal   (Followers: 14)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 3)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 13)
C - Journal of Carbon Research     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 6)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Carbohydrate Research     Hybrid Journal   (Followers: 11)
Carbon     Hybrid Journal   (Followers: 63)
Catalysis for Sustainable Energy     Open Access   (Followers: 3)

        1 2 3 4 5 6 | Last

Journal Cover   Advanced Functional Materials
  [SJR: 4.682]   [H-I: 156]   [41 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  [1610 journals]
  • Photophysics of Molecular‐Weight‐Induced Losses in
           Indacenodithienothiophene‐Based Solar Cells
    • Authors: Nicola Gasparini; Athanasios Katsouras, Mamantos I. Prodromidis, Apostolos Avgeropoulos, Derya Baran, Michael Salvador, Stefanie Fladischer, Erdmann Spiecker, Christos L. Chochos, Tayebeh Ameri, Christoph J. Brabec
      Abstract: The photovoltaic performance and optoelectronic properties of a donor–acceptor copolymer are reported based on indacenodithienothiophene (IDTT) and 2,3‐bis(3‐(octyloxy)phenyl)quinoxaline moieties (PIDTTQ) as a function of the number‐average molecular weight (Mn). Current–voltage measurements and photoinduced charge carrier extraction by linear increasing voltage (photo‐CELIV) reveal improved charge generation and charge transport properties in these high band gap systems with increasing Mn, while polymers with low molecular weight suffer from diminished charge carrier extraction because of low mobility–lifetime (μτ) product. By combining Fourier‐transform photocurrent spectroscopy (FTPS) with electroluminscence spectroscopy, it is demonstrate that increasing Mn reduces the nonradiative recombination losses. Solar cells based on PIDTTQ with Mn = 58 kD feature a power conversion efficiency of 6.0% and a charge carrier mobility of 2.1 × 10−4 cm2 V−1 s−1 when doctor bladed in air, without the need for thermal treatment. This study exhibits the strong correlations between polymer fractionation and its optoelectronics characteristics, which informs the polymer design rules toward highly efficient organic solar cells. The synthesis of a series of indaceno­dithieno[3,2‐b]thiophenebased donor–acceptor copolymers (PIDTT) and the strong correlations between polymer fractionation and its optoelectronics characteristics are demonstrated. In the best case, the active material exhibits more than 6% PCE in inverted solar cells processed via doctor blading in air, without requiring thermal treatment.
      PubDate: 2015-06-26T09:32:52.629338-05:
      DOI: 10.1002/adfm.201501062
       
  • Doxorubicin‐Loaded Single Wall Nanotube Thermo‐Sensitive
           Hydrogel for Gastric Cancer Chemo‐Photothermal Therapy
    • Authors: Minyu Zhou; Shuhan Liu, Yaqi Jiang, Huanrong Ma, Min Shi, Quanshi Wang, Wen Zhong, Wangjun Liao, Malcolm M. Q. Xing
      Abstract: Single wall carbon nanotube (SWNT) based thermo‐sensitive hydrogel (SWNT‐GEL) is reported, which provides an injectable drug delivery system as well as a medium for photothermal transduction. SWNT‐hydrogel alone appears to be nontoxic on gastric cancer cells (BGC‐823 cell line) but leads to cell death with NIR radiation through a hyperthermia proapoptosis mechanism. By incorporating hyperthermia therapy and controlled in situ doxorubicin (DOX) release, DOX‐loaded SWNT‐hydrogel with NIR radiation proves higher tumor suppression rate on mice xenograft gastric tumor models compared to free DOX without detectable organ toxicity. The developed system demonstrates improved efficacy of chemotherapeutic drugs which overcomes systemic adverse reactions and presents immense potential for gastric cancer treatment. A DOX‐loaded SWNT‐based thermo‐sensitive hydrogel (DOX/SWNT‐GEL) in situ drug delivery system is reported. DOX/SWNT‐GEL exhibits pro‐apoptosis effect through a hyperthermia therapy mechanism by NIR radiation, as well as better tumor growth suppression efficacy compared with free DOX in vivo. The combination of controlled drug release and photothermal transduction of DOX/SWNT‐GEL provides a promising prospect in future nanomedicine progress.
      PubDate: 2015-06-26T09:29:42.021844-05:
      DOI: 10.1002/adfm.201501434
       
  • Poly(Acrylic Acid) Modification of Nd3+‐Sensitized Upconversion
           Nanophosphors for Highly Efficient UCL Imaging and pH‐Responsive
           Drug Delivery
    • Authors: Bei Liu; Yinyin Chen, Chunxia Li, Fei He, Zhiyao Hou, Shanshan Huang, Haomiao Zhu, Xueyuan Chen, Jun Lin
      Abstract: In this work, a simple method is demonstrated for the synthesis of multifunctional core–shell nanoparticles NaYF4:Yb,Er@NaYF4:Yb@NaNdF4:Yb@NaYF4:Yb@PAA (labeled as Er@Y@Nd@Y@PAA or UCNP@PAA), which contain a highly effective 808‐nm‐to‐visible UCNP core and a thin shell of poly(acrylic acid) (PAA) to achieve upconversion bioimaging and pH‐sensitive anticancer chemotherapy simultaneously. The core–shell Nd3+‐sensitized UCNPs are optimized by varying the shell number, core size, and host lattices. The final optimized Er@Y@Nd@Y nanoparticle composition shows a significantly improved upconversion luminescence intensity, that is, 12.8 times higher than Er@Y@Nd nanoparticles. After coating the nanocomposites with a thin layer of PAA, the resulting UCNP@PAA nanocomposite perform well as a pH‐responsive nanocarrier and show clear advantages over UCNP@mSiO2, which are evidenced by in vitro/in vivo experiments. Histological analysis also reveals that no pathological changes or inflammatory responses occur in the heart, lungs, kidneys, liver, and spleen. In summary, this study presents a major step forward towards a new therapeutic and diagnostic treatment of tumors by using 808‐nm excited UCNPs to replace the traditional 980‐nm excitation. Multifunctional uniform core–shell nanoparticles NaYF4:Yb, Er@NaYF4:Yb@NaNdF4:Yb@NaYF4:Yb@PAA (UCNP@PAA) consist of a highly effective 808‐nm‐to‐visible UCNP core (with an absolute upconversion quantum yield of 0.18% in green emission mode) and a thin shell of PAA. These UCNP@PAA nanoparticles are designed and synthesized to simultaneously achieve in vitro/in vivo upconversion bioimaging and pH‐sensitive chemotherapy.
      PubDate: 2015-06-25T06:31:22.312389-05:
      DOI: 10.1002/adfm.201501582
       
  • On the Mechanism of Cuprate Crystal Growth: The Role of Mixed Metal
           Carbonates
    • Authors: David C. Green; Rebecca Boston, Stefan Glatzel, Martin R. Lees, Stuart C. Wimbush, Jason Potticary, Wataru Ogasawara, Simon R. Hall
      Abstract: The mechanism of formation of the superconductor Bi2Sr2CaCu2O8+x (Bi‐2212) has been an open question since its discovery in 1988. By controlling crystal growth through the use of biopolymers as multivalent cation chelating agents, it is demonstrated through X‐ray diffraction and thermogravimetric analysis, that it is the formation of a mixed metal carbonate eutectic that promotes the formation of the target phase. X‐ray diffraction experiments, supported by infrared spectroscopy, identify this phase as (Sr1−x Ca x )CO3. This knowledge allows to further reduce the eutectic melting point by the incorporation of a biopolymer rich in potassium ions, resulting in the scalable formation of Bi‐2212 at a temperature 50 °C lower than has been achieved previously. The precise mechanism of formation of the superconductor Bi2Sr2CaCu2O8 +x (Bi‐2212) is unknown. Here, via extensive X‐ray diffraction, infrared spectroscopy, and thermogravimetric analysis, the mechanism is identified, and it is found that a carbonate eutectic (Sr1−x Ca x )CO3 is the key driver in the formation of Bi‐2212. The introduction of potassium ions leads to the formation of Bi‐2212 at a temperature 50 °C lower than has been achieved previously.
      PubDate: 2015-06-25T06:30:20.604189-05:
      DOI: 10.1002/adfm.201501058
       
  • Optimizing the Size of Micellar Nanoparticles for Efficient siRNA Delivery
    • Authors: Shi Liang; Xian‐Zhu Yang, Xiao‐Jiao Du, Hong‐Xia Wang, Hong‐Jun Li, Wei‐Wei Liu, Yan‐Dan Yao, Yan‐Hua Zhu, Yin‐Chu Ma, Jun Wang, Er‐Wei Song
      Abstract: Delivery of small interfering RNA (siRNA) by nanocarriers has shown promising therapeutic potential in cancer therapy. However, poor understanding of the correlation between the physicochemical properties of nanocarriers and their interactions with biological systems has significantly hindered its anticancer efficacy. Herein, in order to identify the optimal size of nanocarriers for siRNA delivery, different sized cationic micellar nanoparticles (MNPs) (40, 90, 130, and 180 nm) are developed that exhibit similar siRNA binding efficacies, shapes, surface charges, and surface chemistries (PEGylation) to ensure size is the only variable. Size‐dependent biological effects are carefully and comprehensively evaluated through both in vitro and in vivo experiments. Among these nanocarriers, the 90 nm MNPs show the optimal balance of prolonged circulation and cellular uptake by tumor cells, which result in the highest retention in tumor cells. In contrast, larger MNPs are rapidly cleared from the circulation and smaller MNPs are inefficiently taken up by tumor cells. Accordingly, 90 nm MNPs carrying polo‐like kinase 1 (Plk1)‐specific siRNA (siPlk1) show superior antitumor efficacy, indicating that 90 nm could either be the optimal size for systemic delivery of siRNA or close to it. Our findings provide valuable information for rationally designing nanocarriers for siRNA‐based cancer therapy in the future. To investigate the optimal size of nanocarriers for siRNA delivery, different sized MNP/siRNAs are rationally designed. Size‐dependent biological effects on circulation, internalization, retention, and overall antitumor efficacy are carefully and comprehensively evaluated. These results indicate that 90 nm could be at or close to the optimal size for systemic delivery of siRNA.
      PubDate: 2015-06-25T06:29:58.260844-05:
      DOI: 10.1002/adfm.201501548
       
  • Restoring Intrinsic Properties of Electromagnetic Radiators Using
           Ultralightweight Integrated Metasurface Cloaks
    • Authors: Zhi Hao Jiang; Peter E. Sieber, Lei Kang, Douglas H. Werner
      Abstract: The concept of invisibility has garnered long‐standing interest throughout human history but has only been realized experimentally within the past decade, albeit over a limited bandwidth. While the physical wave phenomenon of a reduced scattering signature has been demonstrated with different cloaking methods such as transformation optics and scattering cancellation, such technology has yet to be incorporated into any practical real‐world devices. Through the use of quasi‐2D functional metasurfaces, the long‐standing issue of simultaneous mutual coupling and radiation blockage is addressed that occurs when two or more electromagnetic radiators are placed in close proximity to one another. The proposed compact and ultralightweight metasurfaces, comprising arrays of subwavelength electric and magnetic resonators with tailored dispersive properties, are capable of fully restoring the intrinsic properties of real‐world electromagnetic radiators when placed in a multiradiator environment. This work introduces a general design approach to bridge the gap between the theory and practice for cloaks, which is applicable to microwave, terahertz, and optical radiators, as well as acoustic and thermal sources. Moreover, this technology provides an unprecedented opportunity for enabling high‐density deployment of radiating systems with low interference and undistorted signal wave fronts. Integrated ultralightweight metasurface cloaking coatings are demonstrated for restoring intrinsic properties of electromagnetic radiators. By tailoring the dispersive properties of the metasurfaces, the mutual coupling and mutual blockage between multiple radiators can be simultaneously reduced. The general concept and design approach pave the way for dense deployment of terahertz/optical antennas as well as radiators in other realms of physics.
      PubDate: 2015-06-25T06:29:30.443181-05:
      DOI: 10.1002/adfm.201501261
       
  • Strongly Anisotropic Thermal Conductivity of Free‐Standing Reduced
           Graphene Oxide Films Annealed at High Temperature
    • Authors: Jackie D. Renteria; Sylvester Ramirez, Hoda Malekpour, Beatriz Alonso, Alba Centeno, Amaia Zurutuza, Alexandr I. Cocemasov, Denis L. Nika, Alexander A. Balandin
      Abstract: Thermal conductivity of free‐standing reduced graphene oxide films subjected to a high‐temperature treatment of up to 1000 °C is investigated. It is found that the high‐temperature annealing dramatically increases the in‐plane thermal conductivity, K, of the films from ≈3 to ≈61 W m−1 K−1 at room temperature. The cross‐plane thermal conductivity, K⊥, reveals an interesting opposite trend of decreasing to a very small value of ≈0.09 W m−1 K−1 in the reduced graphene oxide films annealed at 1000 °C. The obtained films demonstrate an exceptionally strong anisotropy of the thermal conductivity, K/K⊥ ≈ 675, which is substantially larger even than in the high‐quality graphite. The electrical resistivity of the annealed films reduces to 1–19 Ω □−1. The observed modifications of the in‐plane and cross‐plane thermal conductivity components resulting in an unusual K/K⊥ anisotropy are explained theoretically. The theoretical analysis suggests that K can reach as high as ≈500 W m−1 K−1 with the increase in the sp2 domain size and further reduction of the oxygen content. The strongly anisotropic heat conduction properties of these films can be useful for applications in thermal management. The high‐temperature treatment of reduced graphene oxide films dramatically increases their in‐plane thermal conductivity at room temperature. The cross‐plane thermal conductivity reveals an opposite trend of decreasing to a very small value in the films annealed at 1000 °C. The synthesized films demonstrate an exceptionally strong anisotropy of thermal conductivity, which is useful for thermal management applications.
      PubDate: 2015-06-25T06:28:57.545098-05:
      DOI: 10.1002/adfm.201501429
       
  • Electrochemically Nanostructured Polyvinylferrocene/Polypyrrole Hybrids
           with Synergy for Energy Storage
    • Authors: Wenda Tian; Xianwen Mao, Paul Brown, Gregory C. Rutledge, T. Alan Hatton
      Abstract: Unconjugated redox polymers, such as polyvinylferrocene (PVF), have rarely been used for energy storage due to their low intrinsic conductivity. Conducting polymers with conjugated backbones, though conductive, may suffer from insufficient exposure to the electrolyte due to the often formed nonporous structures. The present work overcomes this limitation via simultaneous electropolymerization of pyrrole and electroprecipitation of PVF on electrode surfaces. This synthesis method relies on the π–π stacking interactions between the aromatic pyrrole monomers and the metallocene moieties of PVF. This fabrication process results in a highly porous polymer film, which enhances the ion accessibility to polypyrrole (PPy). PPy serves as a “molecular wire,” improving the electronic conductivity of the hybrid and the utilization efficiency of ferrocene. The PVF/PPy hybrid exhibited a specific capacitance of 514.1 F g−1 , which significantly exceeds those of PPy (27.3 F g−1) and PVF (79.0 F g−1), respectively. This approach offers an alternative to nanocarbon materials for improving the electronic conductivity of polymer hybrids, and suggests a new strategy for fabricating nanostructured polymer hybrids. This strategy can potentially be applied to various polymers with π‐conjugated backbones and redox polymers with metallocene moieties for applications such as energy storage, sensing, and catalysis. The π–π stacking interactions between aromatic monomers and metallocene moieties are exploited via simultaneous electroprecipitation of polyvinylferrocene and electropolymerization of pyrrole to form a highly porous redox‐responsive hybrid. The resulting synergistic enhancement of the utilization efficiency of ferrocene and the accessibility of ions to polypyrrole leads to the significantly improved electrochemical energy storage performance.
      PubDate: 2015-06-24T13:24:38.634809-05:
      DOI: 10.1002/adfm.201501041
       
  • Cellular Polypropylene Piezoelectret for Human Body Energy Harvesting and
           Health Monitoring
    • Authors: Nan Wu; Xiaofeng Cheng, Qize Zhong, Junwen Zhong, Wenbo Li, Bo Wang, Bin Hu, Jun Zhou
      Abstract: Self‐powered and wearable electronics, which are away from the problems of batteries, can provide the sustainable and comfortable interactive service for people. In this work, cellular polypropylene piezoelectret, which is with excellent physical and electrical properties, is utilized to build the human body energy harvesting and self‐powered human health monitoring systems. The cellular polypropylene piezoelectret flexible generator can reach a maximum peak power density of ≈52.8 mW m−2. Simultaneously, self‐powered human body biological signals detecting sensors are demonstrated to detect the human physiological signals, such as coughing action and arterial pulses. This study strongly indicates the great compatibility and potential applications in human healthy monitoring may pave a new developing way for portable and wearable electronics systems. Simple‐structured and efficient human body energy harvesting and self‐powered human health monitoring systems are demonstrated basing on the cellular polypropylene piezoelectret. A maximum peak power density of ≈52.8 mW m−2 is obtained and human physiological signals, such as coughing action and arterial pulse, are detected. These systems develop a new way for self‐powered and wearable electronics.
      PubDate: 2015-06-24T13:22:34.298001-05:
      DOI: 10.1002/adfm.201501695
       
  • Tunable Photodynamic Switching of DArE@PAF‐1 for Carbon Capture
    • Authors: Richelle Lyndon; Kristina Konstas, Richard A. Evans, Daniel J. Keddie, Matthew R. Hill, Bradley P. Ladewig
      Abstract: A new type of photodynamic carbon capture material with up to 26 wt% CO2 desorption capacity is synthesized via incorporation of diarylethene (DArE) as guest molecules in porous aromatic framework‐1 (PAF‐1). In these host–guest complexes, the carboxylic acid groups featured in DArE allow multiple noncovalent interactions to exist. DArE loadings ranging from 1 to 50 wt% are incorporated in PAF‐1 and the complexes characterized by UV–vis spectroscopy, FT‐IR spectroscopy, CO2, and N2 adsorption. Successful inclusion of DArE in PAF‐1 is indicated by the reduction of pore size distributions and an optimum loading of 5 wt% is determined by comparing the percentage photo­response and CO2 uptake capacity at 1 bar. Mechanistic studies suggest that photoswitching modulates the binding affinity between DArE and CO2 toward the host, triggering carbon capture and release. This is the first known example of photodynamic carbon capture and release in a PAF. Dynamic light‐activated carbon capture and release in porous aromatic framework‐1 (PAF‐1) is achieved by successfully loading diarylethene (DArE) as a guest molecule. Up to 26 wt% CO2 desorption capacity is possible with 50 wt% DArE loading. The observed photodynamicity is because of host–guest competition between DArE and CO2 inside the sterically hindered pores of PAF‐1.
      PubDate: 2015-06-22T12:31:38.615327-05:
      DOI: 10.1002/adfm.201502069
       
  • Masthead: (Adv. Funct. Mater. 24/2015)
    • PubDate: 2015-06-22T09:29:05.25619-05:0
      DOI: 10.1002/adfm.201570161
       
  • Standing‐Wave‐Assisted Creation of Nanopillar Arrays with
           Vertically Integrated Nanogaps for SERS‐Active Substrates
    • Authors: Tae Yoon Jeon; Sung‐Gyu Park, Dong‐Ho Kim, Shin‐Hyun Kim
      Abstract: An optical method is used to create multi‐dimensional metal structures with three distinct periodicities for surface‐enhanced Raman scattering (SERS). Periodic arrays of nanopillars are formed by phase‐shift interference lithography on sub‐micrometer length scales. With the help of a standing wave, each nanopillar is made to be a disk‐stacking structure consisting of a series of 20‐nm‐thick metal nanogaps; the nanopillars consequently resemble a pagoda. The vertically integrated metal nanogaps of the metal‐deposited pagoda‐like nanopillars enable strong localization of an electromagnetic field and effective enhancement of Raman signals for molecules adsorbed on the metal surface. Moreover, the nanopillars are arranged in a regular lattice, which results in a low spatial variation of the SERS intensity and provides high reproducibility in measurements. Arrays of the nanopillars can be further micropatterned to have a periodicity ranging from tens of micrometers to a millimeter by subsequently employing photo‐lithography. The nanopillar arrays promote the wetting of sample fluids, which enables the selective confinement of fluids on the array regions of the micropatterns without spreading. Consequently, numerous fluid samples can be separately deposited, enabling SERS‐based analysis of multiple samples using a single substrate. Arrays of pagoda‐like nanopillars are created by employing a standing wave during phase‐shift interference lithography. A series of metallic nanogaps on the side walls of the nanopillars provide a high density of hot spots for the localization of the electric field, thereby making the arrays an effective SERS substrate. The arrays can be further micropattened by photo‐lithography, enabling the analysis of multiple samples on a single substrate.
      PubDate: 2015-06-22T09:09:07.627538-05:
      DOI: 10.1002/adfm.201501274
       
  • Advanced Concentration Gradient Cathode Material with Two‐Slope for
           High‐Energy and Safe Lithium Batteries
    • Authors: Byung‐Beom Lim; Sung‐Jun Yoon, Kang‐Joon Park, Chong S. Yoon, Sung‐Jin Kim, Juhyon J. Lee, Yang‐Kook Sun
      Abstract: Li[Ni0.65Co0.13Mn0.22]O2 cathode with two‐sloped full concentration gradient (TSFCG), maximizing the Ni content in the inner part of the particle and the Mn content near the particle surface, is synthesized via a specially designed batch‐type reactor. The cathode delivers a discharge capacity of 200 mAh g−1 (4.3 V cutoff) with excellent capacity retention of 88% after 1500 cycles in a full‐cell configuration. Overall electrochemical performance of the TSFCG cathode is benchmarked against conventional cathode (CC) with same composition and commercially available Li[Ni0.8Co0.15Al0.05]O2 (NCA). The TSFCG cathode exhibits the best cycling stability, rate capability, and thermal stability of the three electrodes. Transmission electron microscopy analysis of the cycled TSFCG, CC, and NCA cathodes shows that the TSFCG electrode maintains both its mechanical and structural integrity whereas the NCA electrode nearly pulverizes due to the strain during cycling. Two‐sloped full concentration gradients (TSFCG) of Ni, Co, and Mn ions throughout the cathode particles to maximize the average Ni concentration are successfully synthesized via coprecipitation. The TSFCG cathode exhibits the best cycling stability compared to conventional cathode and Li[Ni0.8Co0.15Al0.05]O2, which delivers a discharge capacity in excess of 200 mAh g−1 with excellent cycle life and thermal stability.
      PubDate: 2015-06-22T09:09:00.503819-05:
      DOI: 10.1002/adfm.201501430
       
  • Imaging‐Guided Combined Photothermal and Radiotherapy to Treat
           Subcutaneous and Metastatic Tumors Using Iodine‐131‐Doped
           Copper Sulfide Nanoparticles
    • Authors: Xuan Yi; Kai Yang, Chao Liang, Xiaoyan Zhong, Ping Ning, Guosheng Song, Dongliang Wang, Cuicui Ge, Chunying Chen, Zhifang Chai, Zhuang Liu
      Abstract: Combining different therapeutic strategies to treat cancer by overcoming limitations of conventional cancer therapies has shown great promise in both fundamental and clinical studies. Herein, by adding 131I when making iodine‐doped CuS nanoparticles, CuS/[131I]I nanoparticles are obtained, which after functionalization with polyethylene glycol (PEG) are used for radiotherapy (RT) and photothermal therapy (PTT), by utilizing their intrinsic high near‐infrared absorbance and the doped 131I‐radioactivity, respectively. The combined RT and PTT based on CuS/[131I]I‐PEG is then conducted, achieving remarkable synergistic therapeutic effects as demonstrated in the treatment of subcutaneous tumors. In the meanwhile, as revealed by bimodal nuclear imaging and computed tomography (CT) imaging, it is found that CuS/[131I]I‐PEG nanoparticles after being injected into primary solid tumors could migrate to and retain in their nearby sentinel lymph nodes. Importantly, the combined RT and PTT applied on those lymph nodes to assist surgical resection of primary tumors results in remarkably inhibited cancer metastasis and greatly prolonged animal survival. In vivo toxicology studies further reveal that our CuS/I‐PEG is not obviously toxic to animals at fourfold of the treatment dose. This work thus demonstrates the potential of combining RT and PTT using a single nanoagent for imaging‐guided treatment of metastatic tumors. Radionuclide iodine‐131‐doped CuS/I nanoparticles are developed for imaging guided combined photothermal and radiotherapy. Such a treatment strategy not only offers synergistic therapeutic effect in the treatment of subcutaneous tumors, but also enables effective treatment of sentinel lymph nodes under the guidance of multimodal gamma and CT imaging to prevent tumor metastasis.
      PubDate: 2015-06-22T09:08:07.673383-05:
      DOI: 10.1002/adfm.201502003
       
  • Highly Sensitive and Selective Biosensors Based on Organic Transistors
           Functionalized with Cucurbit[6]uril Derivatives
    • Authors: Moonjeong Jang; Hyoeun Kim, Sunri Lee, Hyun Woo Kim, Jayshree K. Khedkar, Young Min Rhee, Ilha Hwang, Kimoon Kim, Joon Hak Oh
      Abstract: Biosensors based on a field‐effect transistor platform allow continuous monitoring of biologically active species with high sensitivity due to the amplification capability of detected signals. To date, a large number of sensors for biogenic substances have used high‐cost enzyme immobilization methods. Here, highly sensitive organic field‐effect transistor (OFET)‐based sensors functionalized with synthetic receptors are reported that can selectively detect acetylcholine (ACh+), a critical ion related to the delivery of neural stimulation. A cucurbit[6]uril (CB[6]) derivative, perallyloxyCB[6] ((allyloxy)12CB[6], AOCB[6]), which is soluble in methanol but insoluble in water, has been solution‐deposited as a selective sensing layer onto a water‐stable p‐channel semiconductor, 5,5′‐bis‐(7‐dodecyl‐9H‐fluoren‐2‐yl)‐2,2′‐bithiophene layer. The OFET‐based sensors exhibit a detection limit down to 1 × 10–12 m of ACh+, which is six orders of magnitude lower than that of ion‐selective electrode‐based sensors. Moreover, these OFET‐based sensors show highly selective discrimination of ACh+ over choline (Ch+). The findings demonstrate a viable method for the fabrication of OFET‐based biosensors with high sensitivity and selectivity, and allow for practical applications of OFETs as high‐performance sensors for biogenic substances. Highly sensitive organic‐transistor‐based sensors that can selectively detect a neurotransmitter acetylcholine without enzyme immobilization are prepared by functionalization with a synthetic receptor, a cucurbit[6]uril derivative. These sensors exhibit highly sensitive (detection limit of 1 × 10−12 m) and selective sensing behaviors. This work describes a low‐cost and viable way for the fabrication of high‐performance sensors for the detection of biogenic molecules.
      PubDate: 2015-06-19T10:14:37.32881-05:0
      DOI: 10.1002/adfm.201501587
       
  • Phase‐Transition Microneedle Patches for Efficient and Accurate
           Transdermal Delivery of Insulin
    • Authors: Sixing Yang; Fei Wu, Jianguo Liu, Guorong Fan, William Welsh, Hua Zhu, Tuo Jin
      Abstract: Utilizing the unique virtue of polyvinyl alcohol (PVA) of forming microcrystalline domains as the cross‐linking junctions, a new microneedle system, phase‐transition microneedle (PTM) patch, is invented, which enables highly efficient transdermal delivery of insulin without depositing the needle tip materials to the skin. PTM, formed of biocompatible PVA as the main component, is sufficiently strong for its needle tip to penetrate the epidermis in the dry state, release preloaded cargos by absorbing body fluid in the dermis layer nearly as fast as subcutaneous injection, and retain mechanical toughness in the hydrated state to ensure complete removal from the skin. The microcrystalline cross‐linking enables a protein‐friendly fabrication process free of hazardous cross‐linking agents required for chemical and ionic cross‐linking. Pharmacokinetic and efficacy studies of insulin‐loaded PTM using pig models indicate a transdermal bioavailability over 20%, similar deviations and peak width, only 18 min behind Tmax, and lower glycated hemoglobin (HbA1c) as compared with injection pens. The complete removability of hydrated needle tips may endow PTM with an additional safety insurance, terminating medication whenever hypoglycemia becomes a concern. PTM patch is practically applicable to a variety of protein/peptide medicines requiring frequent dosing by offering painless administration, freedom of refrigeration, and minimal safety concerns. Phase‐transition microneedle (PTM) patch is designed for efficient transdermal delivery of biomedicines without skin deposition of the needle tip materials because of its water‐swelling (instead of dissolving) activated drug release. The main matrix of the PTM is formed from polyvinyl alcohol, a unique hydrophilic polymer whose solution may convert to water‐insoluble hydrogel by forming microcrystalline domains as the cross‐linking junctions via a mild freeze‐thaw treatment.
      PubDate: 2015-06-18T12:28:54.967701-05:
      DOI: 10.1002/adfm.201500554
       
  • Physics of the Switching Kinetics in Resistive Memories
    • Authors: Stephan Menzel; Ulrich Böttger, Martin Wimmer, Martin Salinga
      Abstract: Memristive cells based on different physical effects, that is, phase change, valence change, and electrochemical processes, are discussed with respect to their potential to overcome the voltage–time dilemma that is crucial for an application in storage devices. Strongly non‐linear switching kinetics are required, spanning more than 15 orders of magnitude in time. Temperature‐driven and field‐driven crystallization, threshold switching, ion migration, as well as redox reactions at interfaces are identified as relevant mechanisms. In phase change materials the combination of a reversible threshold switching and extremely large crystal growth velocities at high voltages enables ultra‐fast resistive switching whereas lower voltages will not be sufficient to overcome the energy barrier for crystallization. In electrochemical cells it depends on the voltage regime, which mechanism is the rate‐determining one for switching. While electro‐crystallization dominates at low voltages, electron transfer in the medium voltage range and a mixture of electron transfer and ion migration at high voltages. In valence change materials, ion migration is found to be accelerated by a combined effect of electric field and local temperature increase due to Joule heating. All discussed types of resistive switches can provide sufficient non‐linearity of switching kinetics for overcoming the voltage time dilemma. Highly non‐linear switching kinetics can overcome the voltage‐time dilemma in resistive switching memory devices: while information can be written very fast using high voltages, data retention is excellent over long times under application of lower read voltages. The two time scales can be up to 15 orders of magnitude apart for voltages spanning only around one order of magnitude.
      PubDate: 2015-06-18T12:27:46.030652-05:
      DOI: 10.1002/adfm.201500825
       
  • Inverted Layer‐By‐Layer Fabrication of an Ultraflexible and
           Transparent Ag Nanowire/Conductive Polymer Composite Electrode for Use in
           High‐Performance Organic Solar Cells
    • Authors: Youngmin Kim; Tae In Ryu, Ki‐Hoon Ok, Min‐Gi Kwak, Sungmin Park, Nam‐Gyu Park, Chul Jong Han, Bong Soo Kim, Min Jae Ko, Hae Jung Son, Jong‐Woong Kim
      Abstract: A highly flexible and transparent conductive electrode based on consecutively stacked layers of conductive polymer (CP) and silver nanowires (AgNWs) fully embedded in a colorless polyimide (cPI) is achieved by utilizing an inverted layer‐by‐layer processing method. This CP‐AgNW composite electrode exhibits a high transparency of >92% at wavelengths of 450–700 nm and a low resistivity of 7.7 Ω ◻−1, while its ultrasmooth surface provides a large contact area for conductive pathways. Furthermore, it demonstrates an unprecedentedly high flexibility and good mechanical durability during both outward and inward bending to a radius of 40 μm. Subsequent application of this composite electrode in organic solar cells achieves power conversion efficiencies as high as 7.42%, which represents a significant improvement over simply embedding AgNWs in cPI. This is attributed to a reduction in bimolecular recombination and an increased charge collection efficiency, resulting in performance comparable to that of indium tin oxide‐based devices. More importantly, the high mechanical stability means that only a very slight reduction in efficiency is observed with bending (
      PubDate: 2015-06-18T12:26:16.58046-05:0
      DOI: 10.1002/adfm.201501046
       
  • Realization of Boolean Logic Functionality Using Redox‐Based
           Memristive Devices
    • Authors: Anne Siemon; Thomas Breuer, Nabeel Aslam, Sebastian Ferch, Wonjoo Kim, Jan van den Hurk, Vikas Rana, Susanne Hoffmann‐Eifert, Rainer Waser, Stephan Menzel, Eike Linn
      Abstract: Emerging resistively switching devices are thought to enable ultradense passive nanocrossbar arrays for use as random access memories (ReRAM) by the end of the decade, both for embedded and mass storage applications. Moreover, ReRAMs offer inherent logic‐in‐memory (LIM) capabilities due to the nonvolatility of the devices and therefore great potential to reduce the communication between memory and calculation unit by alleviating the so‐called von Neumann bottleneck. A single bipolar resistive switching device is capable of performing 14 of 16 two input logic functions in the logic concept presented by Linn et al. (“CRS‐logic”). In this paper, five types of selectorless devices are considered to validate this CRS‐logic concept is experimentally by means of the IMP and AND logic operations. As reference device a TaO x ‐based ReRAM cell is considered, which is compared to three more advanced device configurations consisting either of a threshold supported resistive switch (TS‐ReRAM), a complementary switching device (CS), or a complementary resistive switch (CRS). It is shown that all of these devices offer the desired LIM behavior. Moreover, the feasibility of XOR and XNOR operations using a modified logic concept is applied for both CS and CRS devices and the pros and cons are discussed. Resistive switching devices enable sequential logic‐in‐memory operations. The feasibility of 14 of 16 two input Boolean logic functions is proven experimentally for: redox‐based resistive switching cells (ReRAMs), ReRAMs offering inherent threshold switching, ReRAMs offering complementary switching (CS), and complementary resistive switching (CRS) cells. Moreover, it is shown that CS and CRS cells also enable the two remaining functions, XOR and XNOR.
      PubDate: 2015-06-18T12:24:28.589609-05:
      DOI: 10.1002/adfm.201500865
       
  • Pyrene‐Capped Conjugated Amorphous Starbursts: Synthesis,
           Characterization, and Stable Lasing Properties in Ambient Atmosphere
    • Authors: Weidong Xu; Jianpeng Yi, Wen‐Yong Lai, Li Zhao, Qi Zhang, Wenbo Hu, Xin‐Wen Zhang, Yi Jiang, Ling Liu, Wei Huang
      Abstract: A family of trigonal starburst conjugated molecules (TrFPy, TrFPy, and TrF2Py) composed of a truxene core and pyrene cappers with various bridge lengths is synthesized and characterized. The incorporation of pyrene cappers successfully depress the crystallization tendency, resulting in enhanced glassy temperature and improved morphological stability of the thin films. The high photoluminescence yield in neat films and excellent thermal stability render these pyrene‐capped starbursts promising lasing optical gain media. Low amplified spontaneous emission (ASE) thresholds (EthASE) of 180 nJ pulse‐1 and 101 nJ pulse–1 were recorded for TrFPy and TrF2Py, respectively. One dimensional distributed feedback (1D DFB) lasers demonstrated lasing threshold of 9.3 kW/cm2 and 7.3 kW/cm2 for TrFPy (at 457 nm) and TrF2Py lasers (at 451 nm), respectively. The ASE performance of TrFPy and TrF2Py in an ambient condition was recorded with various annealing temperature (from 80 to 250 °C, 10 min). Surprisingly, TrFPy exhibited excellent ASE stability in an ambient condition, which is still detectable even after annealing at 250 °C for 10 min. The results suggest the pyrene‐capped molecular design strategy is positive on improving the optical gain stability and meanwhile maintaining excellent lasing properties. Well‐defined starburst conjugated macromolecules with pyrene moieties as end‐capped groups are explored as the optical gain media for organic semiconductor lasers. The length of oligofluorene bridges between the truxene core and pyrene cappers is carefully tuned. The relationships between their morphology, thermal stability, and amplified spontaneous emission stability in an ambient condition are systematically investigated, suggesting that the pyrene‐capped molecular design improves the optical gain stability.
      PubDate: 2015-06-18T11:48:39.259057-05:
      DOI: 10.1002/adfm.201501337
       
  • Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced
           Solute Segregation
    • Authors: Austin J. Akey; Daniel Recht, James S. Williams, Michael J. Aziz, Tonio Buonassisi
      Abstract: Nanosecond melting and quenching of materials offers a pathway to novel structures with unusual properties. Impurity‐rich silicon processed using nanosecond‐pulsed‐laser‐melting is known to produce nanoscale features in a process referred to as “cellular breakdown” due to destabilization of the planar liquid/solid interface. Here, atom probe tomography combined with electron microscopy is applied to show that the morphology of cellular breakdown in these materials is significantly more complex than previously documented. Breakdown into a complex, branching filamentary structure topped by a few nm of a cell‐like layer is observed. Single‐phase diamond cubic silicon highly supersaturated with at least 10% atomic Co and no detectable silicides is reported within these filaments. In addition, the unprecedented spatio‐chemical accuracy of the atom probe allows to investigate nanosecond formation dynamics of this complex material. Previously reported properties of these materials can now be reconsidered in light of their true composition, and this class of inhomogeneous metastable alloys in silicon can be explored with confidence. A novel single‐phase, filamentary inhomogeneous alloy composed of crystalline silicon with at least 10 atomic % Co incorporated, formed by ion implantation of high doses of Co into crystalline silicon followed by ultrafast pulsed‐laser melting is investigated. Using atom probe tomography measurements of local composition and morphology, the kinetics of formation of this material is explored.
      PubDate: 2015-06-18T11:46:15.396129-05:
      DOI: 10.1002/adfm.201501450
       
  • Miniaturized Flexible Electronic Systems with Wireless Power and
           Near‐Field Communication Capabilities
    • Authors: Jeonghyun Kim; Anthony Banks, Zhaoqian Xie, Seung Yun Heo, Philipp Gutruf, Jung Woo Lee, Sheng Xu, Kyung‐In Jang, Fei Liu, Gregory Brown, Junghyun Choi, Joo Hyun Kim, Xue Feng, Yonggang Huang, Ungyu Paik, John A. Rogers
      Abstract: A class of thin, lightweight, flexible, near‐field communication (NFC) devices with ultraminiaturized format is introduced, and systematic investigations of the mechanics, radio frequency characteristics, and materials aspects associated with their optimized construction are presented. These systems allow advantages in mechanical strength, placement versatility, and minimized interfacial stresses compared to other NFC technologies and wearable electronics. Detailed experimental studies and theoretical modeling of the mechanical and electromagnetic properties of these systems establish understanding of the key design considerations. These concepts can apply to many other types of wireless communication systems including biosensors and electronic implants. Materials and design concepts are introduced for miniaturized flexible electronic systems with wireless power and near‐field communication (NFC) capabilities. The devices have thin, lightweight, flexible construction and advantages in mechanical strength, placement versatility, and minimized interfacial stresses for integration on the body. These concepts can apply to other wireless communication systems including new opportunities in biosensors and electronic implants.
      PubDate: 2015-06-18T11:45:57.056259-05:
      DOI: 10.1002/adfm.201501590
       
  • ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic
           Light Emitting Diodes
    • Authors: Jorge C. D. Faria; Alasdair J. Campbell, Martyn A. McLachlan
      Abstract: Nanostructured oxide arrays have received significant attention as charge injection and collection electrodes in numerous optoelectronic devices. Zinc oxide (ZnO) nanorods have received particular interest owing to the ease of fabrication using scalable, solution processes with a high degree of control of rod dimension and density. Here, vertical ZnO nanorods as electron injection layers in organic light emitting diodes are implemented for display and lighting purposes. Implementing nanorods into devices with an emissive polymer, poly(9,9‐dioctyluorene‐alt‐benzothiadiazole) (F8BT) and poly(9,9‐di‐n‐octylfluorene‐alt‐N‐(4‐butylphenyl)dipheny‐lamine) (TFB) as an electron blocking layer, brightness and efficiencies up to 8602 cd m−2 and 1.66 cd A−1 are achieved. Simple solution processing methodologies combined with postdeposition thermal processing are highlighted to achieve complete wetting of the nanorod arrays with the emissive polymer. The introduction of TFB to minimize charge leakage and nonradiative exciton decay results in dramatic increases to device yields and provides an insight into the operating mechanism of these devices. It is demonstrated that the detected emission originates from within the polymer layers with no evidence of ZnO band edge or defect emission. The work represents a significant development for the ongoing implementation of ZnO nanorod arrays into efficient light emitting devices. Hybrid LEDs combining vertically aligned ZnO nanorods as electron injection layers and polymeric emitters are demonstrated using a simple solution‐processing route. Performance enhancements are achieved by combining a thermal anneal with the inclusion of an electron‐blocking polymer. The measured brightness and efficiencies, up to 8600 cd m−2 and 1.66 cd A−1, highlight the applicability of such architectures for general lighting applications.
      PubDate: 2015-06-18T11:45:47.179206-05:
      DOI: 10.1002/adfm.201501411
       
  • Roll‐to‐Roll Printed Silver Nanowire Semitransparent
           Electrodes for Fully Ambient Solution‐Processed Tandem Polymer Solar
           Cells
    • Authors: Dechan Angmo; Thomas R. Andersen, Janet J. Bentzen, Martin Helgesen, Roar R. Søndergaard, Mikkel Jørgensen, Jon E. Carlé, Eva Bundgaard, Frederik C. Krebs
      Abstract: Silver nanowires (AgNWs) and zinc oxide (ZnO) are deposited on flexible substrates using fast roll‐to‐roll (R2R) processing. The AgNW film on polyethylene terephthalate (PET) shows >80% uniform optical transmission in the range of 550–900 nm. This electrode is compared to the previously reported and currently widely produced indium‐tin‐oxide (ITO) replacement comprising polyethylene terephthalate (PET) silver grid poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) ZnO known as Flextrode. The AgNW/ZnO electrode shows higher transmission than Flextrode above 490 nm in the electromagnetic spectrum reaching up to 40% increased transmission at 750 nm in comparison to Flextrode. The functionality of AgNW electrodes is demonstrated in single and tandem polymer solar cells and compared with parallel devices on traditional Flextrode. All layers, apart from the semitransparent electrodes which are large‐scale R2R produced, are fabricated in ambient conditions on a laboratory roll‐coater using printing and coating methods which are directly transferrable to large‐scale R2R processing upon availability of materials. In a single cell structure, Flextrode is preferable with active layers based on poly‐3‐hexylthiophene(P3HT):phenyl‐C61‐butyric acid methylester (PCBM) and donor polymers of similar absorption characteristics while AgNW/ZnO electrodes are more compatible with low band gap polymer‐based single cells. In tandem devices, AgNW/ZnO is more preferable resulting in up to 80% improvement in PCE compared to parallel devices on Flextrode. Rolling in tandem: Roll‐to‐roll rotary screen printing of silver nanowires (AgNWs) and zinc oxide (ZnO) is realized on flexible substrates enabling large‐area semi‐transparent electrodes with >80% transmission. This electrode is employed in all‐ambient roll‐coating of single and tandem polymer solar cells. AgNW/ZnO proves highly suitable especially for tandem structures while the traditional indium‐tin‐oxide replacement—Flextrode—remains unbeaten in single cells with wide band‐gap polymers.
      PubDate: 2015-06-18T11:42:56.572506-05:
      DOI: 10.1002/adfm.201501887
       
  • Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors
    • Authors: Yu Song; Tian‐Yu Liu, Xin‐Xin Xu, Dong‐Yang Feng, Yat Li, Xiao‐Xia Liu
      Abstract: Polypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Here a two‐prong strategy is demonstrated to stabilize PPy film by growing it on a functionalized partial‐exfoliated graphite (FEG) substrate and doping it with β‐naphthalene sulfonate anions (NS−). The PPy electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between −0.8 and 0 V versus saturated calomel electrode for 10 000 cycles. Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retains 97% of capacitance after 10 000 cycles, which is the best value reported for PPy‐based supercapacitors. The exceptional stability of PPy electrode can be attributed to two factors: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and 2) the presence of immobile NS− dopants suppresses the counterion drain effect during charge–discharge cycling. By a doping polypyrrole film supported on functionalized partial‐exfoliated graphite (FEG) substrate with β‐naphthalene sulfonate anions, the polypyrrole electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between −0.8 and 0 V versus SCE for 10 000 cycles. An asymmetric pseudocapacitor (FEG/PPy‐NS//FEG/MnO2) using the stabilized PPy film as anode can also retain 97% of capacitance after 10 000 cycles.
      PubDate: 2015-06-18T11:42:03.947371-05:
      DOI: 10.1002/adfm.201501709
       
  • Stepwise Drug‐Release Behavior of Onion‐Like Vesicles
           Generated from Emulsification‐Induced Assembly of Semicrystalline
           Polymer Amphiphiles
    • Authors: Mi‐Kyoung Park; Sangmi Jun, Inhye Kim, Seon‐Mi Jin, Jin‐Gyu Kim, Tae Joo Shin, Eunji Lee
      Abstract: Tailoring unique nanostructures of biocompatible and degradable polymers and the consequent elucidation of shape effects in drug delivery open tremendous opportunities not only to broaden their biomedical applications but also to identify new directions for the design of nanomedicine. Cellular organelles provide the basic structural and functional motif for the development of novel artificial nanoplatforms. Herein, aqueous onion‐like vesicles structurally mimicking multicompartmentalized cellular organelles by exhibiting exquisite control over the molecular assembly of poly(ethylene oxide)‐block‐poly(ε‐caprolactone) (PEO‐b‐PCL) semicrystalline amphiphiles are reported. Compared to in situ self‐assembly, emulsification‐induced assembly endows the resulting nanoaggregates of PEO‐b‐PCL with structural diversity such as helical ribbons and onion‐like vesicles through the molecular packing modification in the hydrophobic core with a reduction of inherent crystalline character of PCL. In particular, onion‐like vesicles composed of alternating walls and water channels are interpreted by nanometer‐scale 3D visualization via cryogenic‐electron tomo­graphy (cryo‐ET). Interestingly, the nature of the multi‐walled vesicles results in high drug‐loading capacity and stepwise drug release through hydrolytic cleavage of the PCL block. The crystalline arrangement of PCL at the molecular scale and the spatial organization of assembled structure at the nanoscale significantly affect the drug‐release behavior of PEO‐b‐PCL nanovehicles. Tailoring unique nanostructures of biocompatible and degradable polymers and elucidating their shape effects in drug delivery open tremendous opportunities to not only broaden their biomedical applications but also to identify new directions for designing nanomedicine. The exquisite fabrication of onion‐like vesicles, based on the assembly of poly(ethylene oxide)‐block‐poly(ε‐caprolactone), allows stepwise anticancer drug release through the sequential hydrolytic cleavage of multi‐walls.
      PubDate: 2015-06-18T11:40:21.557601-05:
      DOI: 10.1002/adfm.201501595
       
  • Bioactive Photodegradable Hydrogel for Cultivation and Retrieval of
           Embryonic Stem Cells
    • Authors: Jungmok You; Amranul Haque, Dong‐Sik Shin, Kyung Jin Son, Christian Siltanen, Alexander Revzin
      Abstract: The development of a novel photodegradable heparin‐based hydrogel for cultivation and retrieval of embryonic stem cells is described. Mouse embryonic stem cells cultured atop the gel with encapsulated growth factors (GFs) express higher levels of differentiation markers compared to a standard protocol employing soluble GFs. Beyond improving differentiation of stem cells, the novel hydrogels can be used to release specific stem cell colonies without disturbing neighboring cells. This way, stem cell colonies can be retrieved at different time points and from different locations of the culture surface for polymerase chain reaction (PCR) analysis without the loss of the microenvironment context. The ability to retrieve some stem cell colonies without disturbing neighboring colonies will open possibilities for characterizing in‐dish heterogeneity of stem cell phenotype and will also allow to conserve cells/reagents. Overall, the bioactive photodegradable hydrogel developed in this study may offer new possibilities for cultivation and analysis of stem cells as well as other cell types. A photodegradable bioactive hydrogel helps to improve stem cell differentiation while opening the possibility to retrieve specific colonies from the culture dish for downstream analysis.
      PubDate: 2015-06-18T11:39:06.893069-05:
      DOI: 10.1002/adfm.201501979
       
  • Bioinspired Graphene Actuators Prepared by Unilateral UV Irradiation of
           Graphene Oxide Papers
    • Authors: Dong‐Dong Han; Yong‐Lai Zhang, Yan Liu, Yu‐Qing Liu, Hao‐Bo Jiang, Bing Han, Xiu‐Yan Fu, Hong Ding, Huai‐Liang Xu, Hong‐Bo Sun
      Abstract: Inspired by natural autonomous systems that demonstrate controllable shape, appearance, and actuation under external stimuli, a facile preparation of moisture responsive graphene‐based smart actuators by unilateral UV irradiation of graphene oxide (GO) papers is reported. UV irradiation of GO is found to be an effective protocol to trigger the reduction of GO; however, due to the limited light transmittance and thermal relaxation, thick GO paper cannot be fully reduced. Consequently, by tuning the photoreduction gradient, anisotropic GO/reduced GO (RGO) bilayer structure can be easily prepared toward actuation application. To get better control over the responsive properties, GO/RGO bilayer paper with a certain curvature and RGO patterns are successfully prepared for actuator design. As representative examples, smart humidity‐driven graphene actuators that mimic the cilia of respiratory tract and tendril climber plant are successfully developed for controllable objects transport. A facile preparation of graphene actuators by unilateral UV irradiation of graphene oxide (GO) papers is reported. Anisotropic GO/reduced GO bilayer paper can be directly prepared by controlling the photoreduction gradient. As typical examples, smart humidity‐driven graphene actuators that mimic the cilia of respiratory tract and the tendril climber plant are developed for objects transport.
      PubDate: 2015-06-16T12:41:51.220437-05:
      DOI: 10.1002/adfm.201501511
       
  • Hybrid Organic/Inorganic Nanostructures for Highly Sensitive
           Photoelectrochemical Detection of Dissolved Oxygen in Aqueous Media
    • Authors: Sebastiano Bellani; Ali Ghadirzadeh, Laura Meda, Alberto Savoini, Alessandra Tacca, Gianluigi Marra, Rui Meira, Jorge Morgado, Fabio Di Fonzo, Maria Rosa Antognazza
      Abstract: Precise, reliable, and remote measurement of dissolved oxygen in aqueous media is of great importance for many industrial, environmental, and biological applications. In particular, photoelectrochemical sensors working in differential mode have recently demonstrated promising properties, in terms of stability, sensitivity, and application potential. Here, a new approach is presented, combining visible light sensitivity, efficient photocurrent generation, and solution‐processed fabrication methods of conjugated polymers, with charge carriers selectivity, energetic alignment favorable to efficient interfacial charge transfer and high surface area achievable by using metal oxide nanostructures. Extensive characterization and optimization of the hybrid organic/inorganic system are carried out, leading to the realization of an oxygen sensor device, based on nanostructured palladium oxide/poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole]/[6,6]phenyl‐C61‐butyric acid methyl ester (PdO/APFO‐3:PCBM) as materials of choice. State‐of‐the‐art sensitivity, amounting at −5.87 μA cm−2 ppm−1, low background signal, in the order of −4.85 μA cm−2, good electrochemical stability for more than 2 h of continuous functioning and high reproducibility of the signal over the pH 1 to 10 range, are reported, making the hybrid device suitable for several practical uses. The results fully validate the mixed organic/inorganic approach for photoelectrochemical applications, and pave the way for its further exploitation in fields like waste water treatment, environmental monitoring, and water splitting. A photoelectrochemical sensor for dissolved oxygen, based on the hybrid interface between an organic semiconductor and a nanostructured metal oxide, is realized. State‐of‐the‐art sensitivity, good electrochemical stability and high reproducibility in different environmental conditions, ranging from acid to basic pH, are reported, making the polymer‐based device suitable for applications in waste water treatment, environmental monitoring and water splitting.
      PubDate: 2015-06-16T12:41:41.957081-05:
      DOI: 10.1002/adfm.201500701
       
  • Polyoxometalate‐Modified Sponge‐Like Graphene Oxide Monolith
           with High Proton‐Conducting Performance
    • Authors: Yiwei Liu; Shumei Liu, Xuying Lai, Jun Miao, Danfeng He, Ning Li, Fang Luo, Zhan Shi, Shuxia Liu
      Abstract: Graphene oxide (GO) contains abundant oxygen‐containing functional groups acting as hydrogen bond acceptors for proton conduction on its basal plane. However, the dilemma in realizing bulk in‐plane conduction and the metastability at room temperature of GO films both obstruct its application. Polyoxometalate‐modified sponge‐like GO monolith (PEGO) with 3D cross‐linking inner structure, which exhibits unique “shrink‐expand” effect to polar solvent, are synthesized. Owing to the introduction of polyoxometalates and the replacement of unstable epoxy groups by ethylenediamine, PEGO exhibits hitherto the highest proton conductivity under low relative humidity (1.02 × 10−2 S cm−1 at 60% relative humidity) and excellent long‐term stability (more than 1 month). The outstanding conductivity originates from 3D transporting pathways, high‐density hopping sites, and eliminated grain boundary resistance. This study provides a practical way to design GO‐based proton‐conducting material dominated by in‐plane diffusion. Polyoxomatelate‐modified sponge‐like graphene oxide monolith with 3D cross‐linked inner structure is synthesized. The excellent proton conductivity originates from 3D transporting pathways, higher content of hopping sites, more delocalized hydrogen ions, and eliminated grain boundary resistance. This study provides a practical way to design GO‐based proton‐conducting material dominated by in‐plane diffusion.
      PubDate: 2015-06-16T12:41:35.329918-05:
      DOI: 10.1002/adfm.201501912
       
  • Does Electronic Type Matter when Single‐Walled Carbon Nanotubes are
           Used for Electrode Applications?
    • Authors: G. Dinesha M. R. Dabera; M. R. Ranga Prabhath, Khue T. Lai, K. D. G. Imalka Jayawardena, F. Laurent M. Sam, Lynn J. Rozanski, A. A. Damitha T. Adikaari, S. Ravi P. Silva
      Abstract: Single‐walled carbon nanotube (SWNT) electrodes that are chemically and mechanically robust are fabricated using a simple drop cast method with thermal annealing and acid treatment. An electronic‐type selective decrease in sheet resistance of SWNT electrodes with HNO3 treatment is shown. Semiconducting SWNTs show a significantly higher affinity toward hole doping in comparison to metallic SWNTs; a ≈12‐fold and a ≈fivefold drop in sheet resistance, respectively. The results suggest the insignificance of the electronic type of the SWNTs for the film conductivity after hole doping. The SWNT films have been employed as transparent hole extracting electrodes in bulk heterojunction (BHJ) organic photovoltaics. Performances of the devices enlighten the fact that the electrode film morphology dominates over the electronic type of the doped SWNTs with similar sheet resistance and optical transmission. The power conversion efficiency (PCE) of 4.4% for the best performing device is the best carbon nanotube transparent electrode incorporated large area BHJ solar cell reported to date. This PCE is 90% in terms of PCEs achieved using indium tin oxide (ITO) based reference devices with identical film fabrication parameters indicating the potential of the SWNT electrodes as an ITO replacement toward realization of all carbon solar cells. Fabrication of electronic‐type separated single‐walled carbon nanotube (SWNT) electrodes for organic solar cells, using a simple drop cast method followed by thermal and acid treatment. The thermal and acid treatment processes significantly enhance the conductivity of the SWNT films, enabling the use of the conductivity‐enhanced SWNT layers as hole extracting, transparent electrodes in organic bulk heterojunction solar cells.
      PubDate: 2015-06-15T13:34:35.557294-05:
      DOI: 10.1002/adfm.201501394
       
  • Performances of Liquid‐Exfoliated Transition Metal Dichalcogenides
           as Hole Injection Layers in Organic Light‐Emitting Diodes
    • Authors: Cheolmin Kim; Thang Phan Nguyen, Quyet Van Le, Jong‐Myeong Jeon, Ho Won Jang, Soo Young Kim
      Abstract: 2D transition metal dichalcogenide (TMD) nanosheets, including MoS2, WS2, and TaS2, are used as hole injection layers (HILs) in organic light‐emitting diodes (OLEDs). MoS2, WS2, and TaS2 nanosheets are prepared using an exfoliation by ultrasonication method. The thicknesses and sizes of the TMD nanosheets are measured to be 3.1–4.3 nm and more than 100 nm, respectively. The work functions of the TMD nanosheets increase from 4.4–4.9 to 4.9–5.1 eV following ultraviolet/ozone (UVO) treatment. The turn‐on voltages at 10 cd m−2 for UVO‐treated TMD‐based devices decrease from 7.3–12.8 to 4.3–4.4 V and maximum luminance efficiencies increase from 5.74–9.04 to 12.01–12.66 cd A−1. In addition, this study confirms that the stabilities of the devices in air can be prolonged by using UVO‐treated TMDs as HILs in OLEDs. These results demonstrate the great potential of liquid‐exfoliated TMD nanosheets for use as HILs in OLEDs. 2D transition metal dichalcogenide (TMD) nanosheets, including MoS2, WS2, and TaS2, are used as hole injection layers (HILs) in organic light‐emitting diodes (OLEDs). MoS2, WS2, and TaS2 nanosheets are prepared using an exfoliation by an ultrasonication method. It is shown that the stability of the devices in air can be prolonged by using UV/ozone‐treated TMDs as HILs in OLEDs.
      PubDate: 2015-06-15T13:34:28.227905-05:
      DOI: 10.1002/adfm.201501333
       
  • Developing Biotemplated Data Storage: Room Temperature Biomineralization
           of L10 CoPt Magnetic Nanoparticles
    • Authors: Johanna M. Galloway; Jennifer E. Talbot, Kevin Critchley, Jim J. Miles, Jonathan P. Bramble
      Abstract: L10 cobalt platinum can be used to record data at approximately sixfold higher densities than it is possible to on existing hard disks. Currently, fabricating L10 CoPt requires high temperatures (≈500 °C) and expensive equipment. One ecological alternative is to exploit biomolecules that template nanomaterials at ambient temperatures. Here, it is demonstrated that a dual affinity peptide (DAP) can be used to biotemplate L10 CoPt onto a surface at room temperature from an aqueous solution. One part of the peptide nucleates and controls the growth of CoPt nanoparticles from solution, and the other part binds to SiO2. A native silicon oxide surface is functionalized with a high loading of the DAP using microcontact printing. The DAP biotemplates a monolayer of uniformly sized and shaped nanoparticles when immobilized on the silicon surface. X‐ray diffraction shows that the biotemplated nanoparticles have the L10 CoPt crystal structure, and magnetic measurements reveal stable, multiparticle zones of interaction, similar to those seen in perpendicular recording media. This is the first time that the L10 phase of CoPt has been formed without high temperature/vacuum treatment (e.g., annealing or sputtering) and offers a significant advancement toward developing environmentally friendly, biotemplated materials for use in data storage. A dual affinity peptide is designed to template the formation of technologically valuable L10 CoPt, a magnetic material for use in data storage, onto a surface. This biokleptic synthesis is the first time that L10 CoPt has been formed at room temperature from an aqueous solution and offers a cheaper, greener route to developing biotemplated magnetic thin films for recording.
      PubDate: 2015-06-15T13:34:19.269749-05:
      DOI: 10.1002/adfm.201501090
       
  • Stretchable Supercapacitor with Adjustable Volumetric Capacitance Based on
           3D Interdigital Electrodes
    • Authors: Fengwang Li; Jitao Chen, Xusheng Wang, Mianqi Xue, G. F. Chen
      Abstract: Reduced graphene oxide (rGO)‐based materials have shown good performance as electrodes in flexible energy storage devices owing to their physical properties, high specific surface area, and excellent electrical conductivity. Here, a novel road is reported for fabricating high‐performance supercapacitors based on 3D rGO electrodes and solid electrolyte multilayers via pressure spray printing and machine coating. These supercapacitors demonstrate high and adjustable volumetric capacitance, excellent flexibility, and stretchability. The results show that this commercial strategy has its essential merits such as low‐cost, inexpensive, and simple fabrication for large area production. These properties are in the favor of fabricating high‐performance supercapacitor to meet the practical energy demands in devices, especially flexible electronic devices. Furthermore, this novel 3D interdigital electrode concept can be widely applied to other energy devices for enhancing performances and to other micro devices for reducing cost. 3D interdigital electrodes ensure the adjustable volumetric capacitance of stretchable supercapacitors. A 3D interdigital electrode supercapacitor is composed of reduced graphene oxide (rGO) electrodes (with sandwiched Ag nanowire layers as currents collector) via pressure spray printing and solid electrolyte multilayers via machine coating. It can retain high specific volumetric capacitance while keeping its stretchability, and the specific volumetric capacitance can be adjusted by tuning the thickness of rGO layers.
      PubDate: 2015-06-15T13:34:12.827072-05:
      DOI: 10.1002/adfm.201500718
       
  • Stomata‐Inspired Membrane Produced Through Photopolymerization
           Patterning
    • Authors: Hyejeong Kim; Sang Joon Lee
      Abstract: The programmed movements of responsive functional hydrogels have received much attention because of their abundant functions and wide range of engineering applications. In this study, an innovative stomata‐inspired membrane (SIM) is fabricated by using a temperature‐responsive hydrogel through a simple, cost‐effective, and high‐throughput patterned photopolymerization. Polymerization‐induced diffusion on the macroscale surface results in formation of a double‐parted polymer membrane with fine pores after single illumination. After heating the SIM, the less deformable thick frame supports the whole structure and the highly deformable thin base regulates pore shape. Among various SIM types, the slit pores of monocot SIM, which are lined up in parallel, exhibit the largest radius deformation. The morphological configuration of the SIM can be easily controlled by changing the photomask for a given application. As the developed SIM features the sensing‐to‐activation functions of stimuli‐responsive hydrogels and can be easily fabricated, this membrane can be potentially used for numerous practical applications, such as filter membranes with adjustable pores, membrane‐based sensors, membrane‐based actuators, and multifunctional membranes. An innovative stomata‐inspired membrane (SIM) is fabricated by using a temperature‐responsive hydrogel through a patterned photopolymerization. Polymerization‐induced diffusion on the macroscale surface results in formation of a double‐parted polymer membrane with controllable pores in single illumination, and each part exhibits different mechanical functions. The easily fabricated sensing‐to‐actuation functions of SIM can be used in numerous practical applications.
      PubDate: 2015-06-13T02:42:45.085816-05:
      DOI: 10.1002/adfm.201501445
       
  • Aligned Carbon Nanotube–Based Flexible Gel Substrates for
           Engineering Biohybrid Tissue Actuators
    • Authors: Su Ryon Shin; Courtney Shin, Adnan Memic, Samaneh Shadmehr, Mario Miscuglio, Hyun Young Jung, Sung Mi Jung, Hojae Bae, Ali Khademhosseini, Xiaowu (Shirley) Tang, Mehmet R. Dokmeci
      Abstract: Muscle‐based biohybrid actuators have generated significant interest as the future of biorobotics but so far they move without having much control over their actuation behavior. Integration of microelectrodes into the backbone of these systems may enable guidance during their motion and allow precise control over these actuators with specific activation patterns. Here, this challenge is addressed by developing aligned carbon nanotube (CNT) forest microelectrode arrays and incorporating them into scaffolds for cell stimulation. Aligned CNTs are successfully embedded into flexible and biocompatible hydrogels exhibiting excellent anisotropic electrical conductivity. Bioactuators are then engineered by culturing cardiomyocytes on the CNT microelectrode‐integrated hydrogel constructs. The resulting cardiac tissue shows homogeneous cell organization with improved cell‐to‐cell coupling and maturation, which is directly related to the contractile force of muscle tissue. This centimeter‐scale bioactuator has excellent mechanical integrity, embedded microelectrodes, and is capable of spontaneous actuation behavior. Furthermore, it is demonstrated that a biohybrid machine can be controlled by an external electrical field provided by the integrated CNT microelectrode arrays. In addition, due to the anisotropic electrical conductivity of the electrodes provided by aligned CNTs, significantly different excitation thresholds are observed in different configurations such as the ones with electrical fields applied in directions parallel versus perpendicular to the CNT alignment. Aligned carbon nanotubes (CNTs) are successfully embedded into flexible and biocompatible self‐standing cardiac muscle tissue exhibiting excellent anisotropic electrical conductivity. This centimeter‐scale biohybrid machine has excellent mechanical integrity, embedded micro­electrodes, and is capable of spontaneous linear cyclic contraction/extension actuation. It is demonstrated that a biohybrid machine can be controlled by electrical signals provided by integrated CNT microelectrode arrays.
      PubDate: 2015-06-12T06:03:31.076458-05:
      DOI: 10.1002/adfm.201501379
       
  • Engineering Zeolitic‐Imidazolate Framework (ZIF) Thin Film Devices
           for Selective Detection of Volatile Organic Compounds
    • Authors: Min Tu; Suttipong Wannapaiboon, Kira Khaletskaya, Roland A. Fischer
      Abstract: Thin films of sodalite‐type zeolitic‐imidazolate frameworks (ZIFs, ZIF‐7, 8, 9, 67, 90, and ZIF‐65‐Zn) with different metal centers and functional moieties are fabricated on SiO2 coated quartz crystal microbalance (QCM) substrates using automatic program controlled repeated direct growth method. The repeated direct growth procedure manipulated here shows great applicability for rapid growth of uniform ZIF thin films with controllable thickness. The fabricated ZIF/QCM devices are used to detect vapor phase volatile organic compounds including alcohol/water, BTEX compounds (benzene, toluene, ethylbenzene and xylene isomers), and hexane isomers. The ZIF/QCM devices exhibit selective detection behavior upon exposure to these chemical vapors. The effects of ZIF pore size, limited pore diameter, surface functionality, and structural flexibility on the sensing performances of ZIF/QCM devices are systematically investigated, which would be beneficial for the practical application of ZIF sensors based on array‐sensing technology. Furthermore, the selective adsorption behavior suggests that these ZIF materials have great potentials in the applications of biofuel recovery and the separation of benzene/cyclohexane, xylene, and hexane isomers. A convenient method is employed to fabricate uniform thin films of zeolitic‐imidazolate frameworks (ZIFs) with controllable thickness on silica coated quartz crystal microbalance (QCM) substrates. Because of the effects of ZIF pore size, limited pore diameter, surface functionality, and structural flexibility, the ZIF/QCM hybrid devices exhibit selective adsorption (detection) behavior upon exposure to various vapor phase volatile organic compounds.
      PubDate: 2015-06-12T06:02:37.133426-05:
      DOI: 10.1002/adfm.201500760
       
  • Facile Single‐Precursor Synthesis and Surface Modification of
           Hafnium Oxide Nanoparticles for Nanocomposite γ‐Ray
           Scintillators
    • Authors: Chao Liu; Tibor Jacob Hajagos, David Kishpaugh, Yunxia Jin, Wei Hu, Qi Chen, Qibing Pei
      Abstract: Inorganic nanoparticles/polymer nanocomposites provide a low cost, high performance alternative for gamma scintillation. However, inorganic nanoparticles used thus far suffer from either moderate atomic numbers or low band gaps, limiting the gamma stopping power and photoelectron production in these systems. Here, a highly efficient, facile single‐precursor synthesis protocol is reported for hafnium oxide nanoparticles with an average diameter of 5 nm. The nanoparticle surface is further functionalized for the fabrication of highly transparent bulk‐size nanocomposite monoliths (2 mm thick, transmittance at 550 nm >75%) with nanoparticle loadings up to 40 wt% (net hafnium wt% up to 28.5%). Using poly(vinyltoluene) as the matrix, 2‐(4‐tert‐butylphenyl)‐5‐(4‐biphenylyl)‐1,3,4‐oxadiazole and 1,4‐bis(5‐phenyl‐2‐oxazolyl)benzene as the cascade fluors, and hafnium oxide nanoparticles as the gamma sensitizer, the nanocomposite monolith of 1 cm diameter and 2 mm thickness is fabricated capable of producing a full energy photopeak for 662 keV gamma rays, with the best deconvoluted photopeak energy resolution 75%) at loadings up to 40 wt%. The nanocomposite monoliths are efficient in detecting gamma radiation, being capable of producing a full energy photopeak with deconvoluted resolution
      PubDate: 2015-06-12T05:59:05.744841-05:
      DOI: 10.1002/adfm.201501439
       
  • Semi‐Egg‐Like Heterogeneous Compartmentalization of Cells
           Controlled by Contact Angle Hysteresis
    • Authors: Kang Sun; Mingjie Liu, Hongliang Liu, Pengchao Zhang, Junbing Fan, Jingxin Meng, Shutao Wang
      Abstract: Precise control of liquid inside compartments is critically important in bioreactors, combinatorial analysis, and tissue engineering. A contact angle hysteresis (CAH)‐based strategy is demonstrated to construct a semi‐egg‐like hydrogel architecture, leading to spatial heterogeneous compartmentalization of cells. The semi‐egg‐like architecture is fabricated by successively capturing and gelling prehydrogel liquids using a substrate with controlled‐CAH pattern and ultralow‐CAH background. The controlled‐CAH pattern could capture liquid with tunable size, while ultralow‐CAH background prevents liquid sticking. It is envisioned that this CAH‐based strategy would be promising in designing functional surface for engineering complicated architectures of either biomedical or nonbiomedical systems. From bad to good: Large contact angle hysteresis (CAH, defined by θA − θR) that causes pinning of droplet on surface is often an unfavorable factor in surface chemistry. It is, however, harnessed in constructing a semi‐egg‐like hydrogel for 3D heterogeneous compartmentalization of cells. By designing surface with controlled‐CAH patterns and ultralow‐CAH background, the semi‐egg‐like architecture is fabricated by dip‐coating in a facile way.
      PubDate: 2015-06-12T05:51:09.384284-05:
      DOI: 10.1002/adfm.201501527
       
  • Surface Chemistry of Vitamin: Pyridoxal 5′‐Phosphate (Vitamin
           B6) as a Multifunctional Compound for Surface Functionalization
    • Authors: Jung Seung Lee; Kyuri Kim, Kihong Lee, Joseph P. Park, Kisuk Yang, Seung‐Woo Cho, Haeshin Lee
      Abstract: Vitamins are non‐toxic compounds that perform a variety of biological functions and also available in a large quantity. Other than the usage as food supplements, few attempts have been made to use them as functional materials. In this study, we report that vitamin B6, pyridoxal 5′‐phosphate (PLP), is a multi‐functional molecule for oxide surface chemistry. PLP‐immobilized surfaces exhibit superhydrophilicity and even hemophilicity, enhancing proliferation, migration, and differentiation of mammalian cells. Unlike existing molecules used so far in surface modification, PLP has an intrinsic chemical reactivity toward biomacromolecules due to the presence of the aldehyde group. In fact, RGD peptide is covalently tethered onto PLP surfaces directly in one step without any chemical activation. Furthermore, PLP‐functionalized implant device showed rapid bone healing. As vitamin B6 is a FDA approved molecule for human usage, the surface chemistry of vitamin B6 potentially allows a fast route for surface functionalized medical devices into clinic. Pyridoxal 5′‐phosphate (PLP; vitamin B6) is demontrated as a multifunctional compound for surface functionalization. Vitamin B6 can be anchored onto surfaces via the phosphate group, converting them into hydrophilic surfaces that allow covalent tethering of molecules. Enhancement in endothelial cell and osteoblast proliferation, migration, and differentiation on PLP‐coated surfaces as well as healing of PLP‐coated dental implants in vivo is observed.
      PubDate: 2015-06-11T10:31:31.793692-05:
      DOI: 10.1002/adfm.201501471
       
  • Microscopic Complexity in Phase‐Change Materials and its Role for
           Applications
    • Authors: Volker L. Deringer; Richard Dronskowski, Matthias Wuttig
      Abstract: Phase‐change materials (PCMs) are widely used for data storage and in other functional devices. Despite their seemingly simple compositions, these materials exhibit intriguing microscopic complexity and a portfolio of interesting properties. In this Feature Article, it is shown that structural and electronic peculiarities on the atomic scale are key determinants for the technological success of PCMs. Particular emphasis is put on the interplay of different experimental and theoretical methods, on the bonding nature of crystalline and amorphous PCMs, and on the role of surfaces and nanostructures. Then, unconventional transport properties of the crystalline phases are highlighted, both with regard to electrical and heat conduction. Finally, perspectives and future directions are drawn: for finding new PCMs based on microscopic understanding, and also for new applications of these materials in emerging fields. The property contrast of phase‐change materials (PCMs), used to encode “ones” and “zeroes” in digital memories, originates on the atomic scale. This Feature Article reviews unconventional structural, bonding, and transport properties of seemingly simple PCMs. This intriguing microscopic complexity can be exploited for new applications in data storage and beyond.
      PubDate: 2015-06-10T22:57:44.734837-05:
      DOI: 10.1002/adfm.201500826
       
  • Mesoporous Carbon Nanocube Architecture for High‐Performance
           Lithium–Oxygen Batteries
    • Authors: Bing Sun; Shuangqiang Chen, Hao Liu, Guoxiu Wang
      Abstract: One of the major challenges to develop high‐performance lithium–oxygen (Li–O2) battery is to find effective cathode catalysts and design porous architecture for the promotion of both oxygen reduction reactions and oxygen evolution reactions. Herein, the synthesis of mesoporous carbon nanocubes as a new cathode nanoarchitecture for Li–O2 batteries is reported. The oxygen electrodes made of mesoporous carbon nanocubes contain numerously hierarchical mesopores and macropores, which can facilitate oxygen diffusion and electrolyte impregnation throughout the electrode, and provide sufficient spaces to accommodate insoluble discharge products. When they are applied as cathode catalysts, the Li–O2 cells deliver discharge capacities of 26 100 mA h g−1 at 200 mA g−1, which is much higher than that of commercial carbon black catalysts. Furthermore, the mesoporous nanocube architecture can also serve as a conductive host structure for other highly efficient catalysts. For instance, the Ru functionalized mesoporous carbon nanocubes show excellent catalytic activities toward oxygen evolution reactions. Li–O2 batteries with Ru functionalized mesoporous carbon nanocube catalysts demonstrate a high charge/discharge electrical energy efficiency of 86.2% at 200 mA g−1 under voltage limitation and a good cycling performance up to 120 cycles at 400 mA g−1 with the curtaining capacity of 1000 mA h g−1. Mesoporous carbon nanocubes (MCCs) are synthesized by a chemical vapor deposition method. Oxygen electrode made of MCCs contains a hierarchical porous structure, which can facilitate oxygen diffusion, electrolyte impregnation, and accommodation of discharge products during the charge and discharge processes.
      PubDate: 2015-06-10T22:57:37.881592-05:
      DOI: 10.1002/adfm.201500863
       
  • Low‐Temperature Transport in Crystalline Ge1Sb2Te4
    • Authors: Hanno Volker; Peter Jost, Matthias Wuttig
      Abstract: Disorder and its reduction upon annealing play a crucial role in understanding the electrical transport in the crystalline phase‐change material Ge1Sb2Te4. Previous studies focus either on the impact of disorder at moderate temperatures or on the low‐temperature properties of crystalline films with a low degree of disorder. The present investigation describes and discusses the impact of pronounced disorder on charge transport at low temperatures. The present data reveal the existence of a metal‐to‐insulator transition (MIT), where upon increasing order the zero‐temperature limit of conductivity changes from zero (insulator) to nonzero values (metal). The position of the MIT is determined with respect to the control parameter, i.e., the disorder, which is modified through the annealing conditions. Disorder is shown to localize carriers for an exceptionally large density of states. In the most disordered films, variable range hopping is observed, enabling the determination of the localization length. At the lowest temperatures studied, deviations from Mott variable range hopping are observed, which can be explained by a transition to Efros–Shklovskii hopping due to the presence of a soft Coulomb gap. The phase‐change material Ge1Sb2Te4 displays a strong annealing effect in its electronic properties. It is shown that even an insulator‐to‐metal transition in the zero‐temperature limit takes place. The low‐temperature transport on the insulating side can be described by Mott's hopping law. A crossover to a different transport mechanism at even lower temperatures is investigated.
      PubDate: 2015-06-10T22:57:31.763706-05:
      DOI: 10.1002/adfm.201500830
       
  • Layered, Nanonetwork Composite Cathodes for Flexible,
           High‐Efficiency, Organic Light Emitting Devices
    • Authors: Junwei Xu; Gregory M. Smith, Chaochao Dun, Yue Cui, Jiwen Liu, Huihui Huang, Wenxiao Huang, David L. Carroll
      Abstract: In this work, the application of an aluminum (Al)/multiwall carbon nanotube (MWCNT)/Al, multilayered electrode to flexible, high‐efficiency, alternating current driven organic electroluminescent devices (AC‐OEL), is reported. The electrode is fabricated by sandwiching a spray‐cast nanonetwork film of MWCNTs between two evaporated layers of Al. The resulting composite film facilitates a uniform charge distribution across a robust crack‐free electrode under various bending angles. It is demonstrated that these composite electrodes stabilize the power efficiency of flexible devices for bending angles up to 120°, with AC‐OEL device power efficiencies of ≈22 lm W−1 at luminances of ≈4000 cd m−2 (using no output coupling). Microscopic examination of the Al/MWCNTs/Al electrode after bending of up to 1300 cycles suggests that the nanotubes significantly enhance the mechanical properties of the thin Al layers while providing a moderate modification to the work function of the metal. While the realization of robust, high‐brightness, and high‐efficiency AC‐OEL devices is potentially important in their future lighting applications, it is anticipated that this to also have significant impact in standard organic light emitting diodes lighting applications. Nanocomposite cathode structures—in this case metals together with multiwalled nanotubes—with the aim of combining mechanical and electronic properties to achieve better performance in an organic flexible are examined. A flexible high‐efficiency alternating current (AC) driven field‐induced polymer electroluminescent) device is chosen as the platform system with the understanding that this approach to organic devices clearly points to organic light emitting diodes, organic thin‐film transistors, and other flexible systems.
      PubDate: 2015-06-10T22:57:28.075176-05:
      DOI: 10.1002/adfm.201501068
       
  • A Surface Tailoring Method of Ultrathin Polymer Gate Dielectrics for
           Organic Transistors: Improved Device Performance and the Thermal Stability
           Thereof
    • Authors: Hyejeong Seong; Jieung Baek, Kwanyong Pak, Sung Gap Im
      Abstract: Tailoring the surface of the dielectric layer is of critical importance to form a good interface with the following channel layer for organic thin film transistors (OTFTs). Here, a simple surface treatment method is applied onto an ultrathin (
      PubDate: 2015-06-10T22:56:51.567592-05:
      DOI: 10.1002/adfm.201500952
       
  • “Layer‐Filter Threshold” Technique for
           Near‐Infrared Laser Ablation in Organic Semiconductor Device
           Processing
    • Authors: Feng Ye; Zhaobin Chen, Xiaoli Zhao, Jiayue Chen, Xiaoniu Yang
      Abstract: Although conventional laser ablation (CLA) method has widely been used in patterning of organic semiconductor thin films, its quality control still remains unsatisfied due to the ambiguous photochemical and photothermal processes. Based on industrial available near‐infrared laser source, herein, a novel “layer‐filter threshold” (LFT) technique is proposed, which involves the decomposition of targeted “layer‐filter” and subsequent explosive evaporation process to purge away the upper layers instead of layer‐by‐layer ablation. For photovoltaic device with structure of metal/blend/PEDOT:PSS/ITO/glass, the PEDOT:PSS layer as the “layer‐filter” is first demonstrated to be effective, and then the merged P1–P2 line and metal electrode layer are readily patterned through the “self‐aligned” effect and regulation of ablation direction, respectively. The correlation between laser fluence and explosive ablation efficacy is also investigated. Finally, photovoltaic modules based on classical P3HT:PC61BM and low‐bandgap PBDT‐TFQ:PC71BM systems are separately fabricated following the LFT technique. It is found that over 90% of geometric fill factor is achieved while device performances maintain in a limited change with increased number of series cells. In comparison to conventional laser ablation methods, the LFT technique does not require sophisticated instruments but reaches comparable processing accuracy, which shows promising potential in the fabrication and commercialization of organic semiconductor thin‐film devices. Layer‐filter threshold (LFT) technique based on near‐infrared laser is proposed and demonstrated, which enables the patterning strategy through an interlayer explosion effect with high precision and easily reachable operating conditions. Thus obtained organic photovoltaic modules reach geometric fill factors exceeding 90% and maintain the performances with increasing number of interconnected cells, which verifies the potential of LFT technique in the patterning of organic semiconductor devices.
      PubDate: 2015-06-10T22:56:46.477912-05:
      DOI: 10.1002/adfm.201501688
       
  • Polywraplex, Functionalized Polyplexes by Post‐Polyplexing Assembly
           of a Rationally Designed Triblock Copolymer Membrane
    • Authors: Xuemei Ge; Shiyue Duan, Fei Wu, Jia Feng, Hua Zhu, Tuo Jin
      Abstract: A core–shell structured synthetic carrier, polywraplex, is reported to overcome the hurdles along the inter‐ and intracellular pathways of systemic delivery of siRNA, yet remain structurally simple and easy‐to‐formulate. The core is a cationic polyplex formed of siRNA with polyethylene imine (PEI) and polyspermine‐imidazole‐4,5‐imine (PSI), respectively, and the shell is a self‐assembled unilamella membrane of PEG45‐PCL20‐mototriose‐COO−, a triblock copolymer possessing multicarboxyl saccharide block to guide adsorption to each polyplex surface, a hydrophobic central block to form a protecting layer around the nucleic acid core, and a PEG block functioning as a steric stabilization out‐layer to extend in vivo circulation. The hydrophobic layer limits the anionic charges of the guiding block within a 2D surface to prevent them from penetrating into the polyplex, a common cause for prephagocytic siRNA leaking by polyelectrolytes in vivo. Cell targeting agents may be conjugated to the distal end of the PEG block and assembled on polyplex surface in optimal population. Chemical characterizations comprising consequent fluorescent imaging, dynamic laser scattering, zeta potential, as well as electrophoresis confirm polywraplex formation and its protection to siRNA against leaking and degradation in serum. Cellular and in vivo (mice) assays of biotin‐conjugated polywraplexes suggest prolonged circulation and tumor tissue targeting. This report demonstrates an easy‐formulating core‐shell structured carrier for nucleic acids, comprising a polyplex core of any content and triblock copolymer membrane to encapsulate, protect, and direct the nucleic acid materials such as siRNA to target cells without pre‐phagocytic leaking, degradation, and disassembly.
      PubDate: 2015-06-09T06:47:28.044684-05:
      DOI: 10.1002/adfm.201500724
       
  • Creation of Liquid Metal 3D Microstructures Using Dielectrophoresis
    • Authors: Shi‐Yang Tang; Jiuyang Zhu, Vijay Sivan, Berrak Gol, Rebecca Soffe, Wei Zhang, Arnan Mitchell, Khashayar Khoshmanesh
      Abstract: Patterning customized arrays of microscale Galinstan or EGaIn liquid metals enables the creation of a variety of microfabricated systems. Current techniques for creating microsized 3D structures of liquid metals are limited by the large dimension or low aspect ratio of such structures, and time‐consuming processes. Here, a novel technique for creating 3D microstructures of Galinstan using dielectrophoresis is introduced. The presented technique enables the rapid creation of Galinstan microstructures with various dimensions and aspect ratios. Two series of proof‐of‐concept experiments are conducted to demonstrate the capabilities of this technique. First, the 3D Galinstan microstructures are utilized as 3D microelectrodes to enhance the trapping of tungsten trioxide (WO3) nanoparticles flowing through a microfluidic channel. Second, the patterned Galinstan microstructures are utilized as microfins to improve the dissipation of heat within a microfluidic channel that is located onto a hot spot. The presented technique can be readily used for creating customized arrays of 3D Galinstan microstructures for a wide range of applications. This work introduces a novel technique for creating 3D microstructures of Galinstan using dielectrophoresis. It enables the rapid formation of multiple microstructures with controllable diameters and aspect ratios. Proof‐of‐concept experiments are conducted by utilizing the patterned microstructures as 3D microelectrodes for enhancing the trapping of suspended nanoparticles, and as microfins to improve the convective heat transfer within a microfluidic channel.
      PubDate: 2015-06-09T06:46:42.303518-05:
      DOI: 10.1002/adfm.201501296
       
  • Controllable Fabrication of Transparent Macroporous Graphene Thin Films
           and Versatile Applications as a Conducting Platform
    • Authors: Jinhua Sun; Mushtaque A. Memon, Wei Bai, Linhong Xiao, Bin Zhang, Yongdong Jin, Yong Huang, Jianxin Geng
      Abstract: Graphene sheets have been demonstrated to be the building blocks for various assembly structures, which eventually determine the macroscopic properties of graphene materials. As a new assembly structure, transparent macroporous graphene thin films (MGTFs) are not readily prepared due to the restacking tendency of graphene sheets during processing. Here, an ice crystal‐induced phase separation process is proposed for preparation of transparent MGTFs. The ice crystal‐induced phase separation process exhibits several unique features, including efficient prevention of graphene oxide restacking, easy control on the transparency of the MGTFs, and wide applicability to substrates. It is shown that the MGTFs can be used as porous scaffold with high conductivity for electrochemical deposition of various semiconductors and rare metal nanoparticles such as CdSe, ZnO, and Pt, as well as successive deposition of different materials. Notably, the macroporous structures bestow the MGTFs and the nanoparticle‐decorated MGTFs (i.e., Pt@MGTF and CdSe@MGTF) enhanced performance as electrode for oxygen reduction reaction and photoelectrochemical H2 generation. Macroporous graphene thin films (MGTFs) that combine the features of 2D graphene films (being transparent) and 3D porous monoliths (being porous) are fabricated. The MGTFs can be used as porous electrode for electrochemical deposition of nanoparticles such as Pt and CdSe. The macroporous structures lead to enhanced performance in ORR and photoelectrochemical H2 generation.
      PubDate: 2015-06-08T08:43:51.126604-05:
      DOI: 10.1002/adfm.201501733
       
  • High Quality Carbon Nanotubes on Conductive Substrates Grown at Low
           Temperatures
    • Authors: Muhammad Ahmad; Jose V. Anguita, Vlad Stolojan, Tony Corless, Jeng‐Shiung Chen, J. David Carey, S. Ravi P. Silva
      Abstract: For carbon nanotubes (CNTs) to be exploited in electronic applications, the growth of high quality material on conductive substrates at low temperatures (
      PubDate: 2015-06-08T08:43:43.170861-05:
      DOI: 10.1002/adfm.201501214
       
  • Protein Corona Influences Cell–Biomaterial Interactions in
           Nanostructured Tissue Engineering Scaffolds
    • Authors: Vahid Serpooshan; Morteza Mahmoudi, Mingming Zhao, Ke Wei, Senthilkumar Sivanesan, Khatereh Motamedchaboki, Andrey V. Malkovskiy, Andrew B. Goldstone, Jeffrey E. Cohen, Phillip C. Yang, Jayakumar Rajadas, Daniel Bernstein, Y. Joseph Woo, Pilar Ruiz‐Lozano
      Abstract: Biomaterials are extensively used to restore damaged tissues, in the forms of implants (e.g., tissue engineered scaffolds) or biomedical devices (e.g., pacemakers). Once in contact with the physiological environment, nanostructured biomaterials undergo modifications as a result of endogenous proteins binding to their surface. The formation of this macromolecular coating complex, known as “protein corona,” onto the surface of nanoparticles and its effect on cell–particle interactions are currently under intense investigation. In striking contrast, protein corona constructs within nanostructured porous tissue engineering scaffolds remain poorly characterized. As organismal systems are highly dynamic, it is conceivable that the formation of distinct protein corona on implanted scaffolds might itself modulate cell–extracellular matrix interactions. Here, it is reported that corona complexes formed onto the fibrils of engineered collagen scaffolds display specific, distinct, and reproducible compositions that are a signature of the tissue microenvironment as well as being indicative of the subject's health condition. Protein corona formed on collagen matrices modulated cellular secretome in a context‐specific manner ex vivo, demonstrating their role in regulating scaffold–cellular interactions. Together, these findings underscore the importance of custom‐designing personalized nanostructured biomaterials, according to the biological milieu and disease state. The use of protein corona as in situ biosensor of temporal and local biomarkers is proposed. The formation of “protein corona” complexes onto the nanofibrillar structure of tissue engineering collagen‐based scaffolds is evaluated. The corona decorations formed onto collagen matrices are tissue‐specific and subject's health‐specific, and regulated cellular secretome ex vivo. In sum, the results demonstrate the significance of protein corona formation onto tissue engineered constructs in the cell–biomaterial interactions.
      PubDate: 2015-06-05T10:26:17.547534-05:
      DOI: 10.1002/adfm.201500875
       
  • Silver/Reduced Graphene Oxide Hydrogel as Novel Bactericidal Filter for
           Point‐of‐Use Water Disinfection
    • Authors: Xiangkang Zeng; David T. McCarthy, Ana Deletic, Xiwang Zhang
      Abstract: Nanomaterials open an alternative way for water disinfection. However, limitations such as aggregation, toxicity, and complex post‐treatment block their practical application. In this study, an antibacterial silver/reduced graphene oxide (Ag/rGO) hydrogel consisting of controlled porous rGO network and well‐dispersed Ag nanoparticle is synthesized by a facile hydrothermal reaction. Scanning electron microscopy, transmission electron microscope, X‐ray diffraction, mercury porosimetry, and Fourier transform IR spectroscopy are employed to characterize the Ag/rGO hydrogel. The 3D structure of the rGO network serves as an excellent support for Ag nanoparticles. Disinfection experiments show that the Ag/rGO hydrogel exhibits good efficacy against Escherichia coli when used as a bactericidal filter driven by gravity. The mechanistic study indicates that bacteria cells are inactivated due to cell membrane damage induced by silver nanoparticles and rGO nanosheets when they flow through Ag/rGO hydrogel. Moreover, due to the retaining of Ag by rGO, the leaching level of silver from Ag/rGO hydrogel is considerably lower than the drinking water standard. This study sheds new light on designing antibacterial materials for point‐of‐use water disinfection application. A novel bactericidal silver/reduced graphene oxide (Ag/rGO) hydrogel with well‐dispersed Ag nanoparticles and controlled porous rGO network is synthesized by an environment‐friendly one‐pot hydrothermal reaction. The highly porous Ag/rGO hydrogel exhibits excellent antibacterial performance when it is used to filter real impaired water driven only by gravity, inactivating more than 94% of Escherichia coli cells and around 99% of coliforms.
      PubDate: 2015-06-05T10:25:57.804817-05:
      DOI: 10.1002/adfm.201501454
       
  • Strain Tuning and Strong Enhancement of Ionic Conductivity in
           SrZrO3–RE2O3 (RE = Sm, Eu, Gd, Dy, and Er) Nanocomposite Films
    • Authors: Shinbuhm Lee; Wenrui Zhang, Fauzia Khatkhatay, Quanxi Jia, Haiyan Wang, Judith L. MacManus‐Driscoll
      Abstract: Fast ion transport channels at interfaces in thin films have attracted great attention due to a range of potential applications for energy materials and devices, for, solid oxide fuel cells, sensors, and memories. Here, it is shown that in vertical nanocomposite heteroepitaxial films of SrZrO3–RE2O3 (RE = Sm, Eu, Gd, Dy, and Er) the ionic conductivity of the composite can be tuned and strongly enhanced using embedded, stiff, and vertical nanopillars of RE2O3. With increasing lattice constant of RE2O3 from Er2O3 to Sm2O3, it is found that the tensile strain in the SrZrO3 increases proportionately, and the ionic conductivity of the composite increases accordingly, by an order of magnitude. The results here conclusively show, for the first time, that strain in films can be effectively used to tune the ionic conductivity of the materials. It is shown that the ionic conductivity in vertical nanocomposite heteroepitaxial films of SrZrO3–RE2O3 can be tuned and strongly enhanced using embedded, stiff, and vertical nanopillars of RE2O3 (RE = Sm, Eu, Gd, Dy, and Er). This is attributed to proportional increase of tensile strain in SrZrO3 with increasing lattice constant of RE2O3 from Er2O3 to Sm2O3.
      PubDate: 2015-06-05T10:25:14.865593-05:
      DOI: 10.1002/adfm.201404420
       
  • Improved Heat Spreading Performance of Functionalized Graphene in
           Microelectronic Device Application
    • Authors: Yong Zhang; Haoxue Han, Nan Wang, Pengtu Zhang, Yifeng Fu, Murali Murugesan, Michael Edwards, Kjell Jeppson, Sebastian Volz, Johan Liu
      Abstract: It is demonstrated that a graphene‐based film (GBF) functionalized with silane molecules strongly enhances thermal performance. The resistance temperature detector results show that the inclusion of silane molecules doubles the heat spreading ability. Furthermore, molecular dynamics simulations show that the thermal conductivity (κ) of the GBF increased by 15%–56% with respect to the number density of molecules compared to that with the nonfunctionalized graphene substrate. This increase in κ is attributed to the enhanced in‐plane heat conduction of the GBF, resulting from the simultaneous increase of the thermal resistance between the GBF and the functionalized substrate limiting cross‐plane phonon scattering. Enhancement of the thermal performance by inserting silane‐functionalized molecules is important for the development of next‐generation electronic devices and proposed application of GBFs for thermal management. Graphene‐based film (GBF) functionalized with silane molecules doubles the heat spreading ability. Molecular dynamics (MD) simulations show that the thermal conductivity (κ) of the GBF increased by 15%–56% compared to that with the nonfunctionalized graphene substrate. The enhancement of the thermal performance by inserting silane‐functionalized molecules holds great potential for applications in thermal management field.
      PubDate: 2015-06-05T10:24:50.288952-05:
      DOI: 10.1002/adfm.201500990
       
  • 3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent
           Layers for Flexible Transparent Displays without Mirrors, Electrodes, and
           Electric Circuits
    • Authors: Satoshi Watanabe; Takeo Asanuma, Takafumi Sasahara, Hiroshi Hyodo, Mutsuyoshi Matsumoto, Kohei Soga
      Abstract: A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho3+‐ and Yb3+‐codoped NaYF4 nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF4 nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF4 nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF4 nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF4 nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er3+‐doped NaYF4 nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits. Arrayed waveguide gratings consisting of two optical polymers are fabricated on patterned upconversion luminescent layers prepared with rare‐earth‐ion‐doped nanoparticle films for upconversion transparent displays. These displays take advantages of long‐operating lifetimes, high transparency, and mechanical flexibility, and do not require mirrors, transparent electrodes, transistor circuits, leading to the fabrication with low cost, minimized material consumptions, and few fabrication steps.
      PubDate: 2015-06-05T02:21:18.210414-05:
      DOI: 10.1002/adfm.201500542
       
  • Eclipse Pulsed Laser Deposition for Damage‐Free Preparation of
           Transparent ZnO Electrodes on Top of Organic Solar Cells
    • Authors: Sylvio Schubert; Florian Schmidt, Holger von Wenckstern, Marius Grundmann, Karl Leo, Lars Müller‐Meskamp
      Abstract: Pulsed laser deposited gallium doped zinc oxide (ZnO:Ga) is reported as transparent top electrode for organic solar cells. In contrast to standard coating techniques, prone to harm organic sublayers and leading to strongly reduced device efficiencies, eclipse pulsed laser deposition (PLD) in argon atmosphere is identified as compatible, nonharmful deposition method for ZnO:Ga, even on top of sensitive organic material. Although PLD is not yet ready for mass production, the experiments reveal and solve crucial process limitations, e.g., droplet impacts, which might be useful also for high yield deposition methods. Optimized ZnO:Ga top electrodes achieve a high mean transparency in the visible spectral range of Tvis = 82.7% and a reasonable sheet resistance of RS = 83 Ω sq−1. The organic photovoltaic devices prepared with this electrode obtained an efficiency of η = 2.9%, almost equal to the efficiency of reference samples using a state‐of‐the‐art metal top contact (η = 3.0%). The investigations here demonstrate the successful deposition of transparent conductive oxides as top electrode for organic devices and open a new path towards the combination of metal oxides and organic semiconductors. ZnO transparent topelectrodes are successfully deposited onto evaporated small molecule organic solar cells by eclipse pulsed laser deposition (PLD). The damage‐free deposition is achieved by variation of the target composition (Ga content), the chamber background gas (O2, N2, Ar) and pressure, and the PLD parameters, including distance and substrate shadowing (eclipse PLD). Thus, PLD enables the deposition of TCO materials onto sensitive organic devices.
      PubDate: 2015-06-05T02:19:17.26441-05:0
      DOI: 10.1002/adfm.201500569
       
  • Graphene‐Oxide‐Conjugated Polymer Hybrid Materials for
           Calmodulin Sensing by Using FRET Strategy
    • Authors: Hongbo Yuan; Junjie Qi, Chengfen Xing, Hailong An, Ruimin Niu, Yong Zhan, Yibing Fan, Wenmin Yan, Ruihua Li, Bing Wang, Shu Wang
      Abstract: The conformation of calmodulin (CaM) changes from closed configuration to open one, converting to a claviform dumbbell‐shaped biomolecule upon Ca2+‐binding. A hybrid probe of graphene oxide (GO) cationic conjugated polymer for detection of the conformation transition of CaM by using FRET technique is demonstrated. The stronger hydrophobic interaction and weaker electrostatic repulsion leads to more CaM adsorption to the surface of GO upon binding with Ca2+ than that of CaM in the absence of Ca2+ (apoCaM), resulting in much farther proximity between poly[(9,9‐bis(6′‐N,N,N‐trimethy­lammonium)hexyl)‐fluorenylene phenylene dibromide] (PFP) and green fluorescent protein labeled at the N‐terminus of CaM and therefore much weaker FRET efficiency for PFP/Ca2+/CaM in comparison with that of PFP/apoCaM in the presence of GO. Notably, the assembly of CaM with GO is quantitatively and reversibly controlled by Ca2+ ions. A hybrid probe of graphene oxide cationic conjugated polymer for detection of Ca2+‐induced conformation changes of calmodulin by using FRET technique is demonstrated. The detection is based on the electrostatic and hydrophobic interactions between CaM and GO, and the assembly of CaM with GO is quantitatively and reversibly controlled by Ca2+ ions.
      PubDate: 2015-06-05T02:18:51.991675-05:
      DOI: 10.1002/adfm.201501668
       
  • Internal Magnetic Structure of Nanoparticles Dominates
           Time‐Dependent Relaxation Processes in a Magnetic Field
    • Authors: Cindi L. Dennis; Kathryn L. Krycka, Julie A. Borchers, Ryan D. Desautels, Johan van Lierop, Natalie F. Huls, Andrew J. Jackson, Cordula Gruettner, Robert Ivkov
      Abstract: Magnetic nanoparticles provide a unique combination of small size and responsiveness to magnetic fields making them attractive for applications in electronics, biology, and medicine. When exposed to alternating magnetic fields, magnetic nanoparticles can generate heat through loss power mechanisms that continue to challenge a complete physical description. The influence of internal nanoparticle (intracore) magnetic domain structure on relaxation remains unexplored. Within the context of potential biomedical applications, this study focuses on the dramatic differences observed among the specific loss power of three magnetic iron oxide nanoparticle constructs having comparable size and chemical composition. Analysis of polarization analyzed small angle neutron scattering data reveals unexpected and complex coupling among magnetic domains within the nanoparticle cores that influences their interactions with external magnetic fields. These results challenge the prevailing concepts in hyperthermia which limit consideration to size and shape of magnetic single domain nanoparticles. Internal magnetic properties of nanoparticles hold key for medicine. This study focuses on the dramatic differences observed among the specific loss power of three magnetic iron oxide nanoparticle constructs having comparable size and chemical composition. The results challenge the prevailing concepts in hyperthermia which limit consideration to size and shape of magnetic single domain nanoparticles.
      PubDate: 2015-06-02T14:05:54.206687-05:
      DOI: 10.1002/adfm.201500405
       
  • Redox Reactions at Cu,Ag/Ta2O5 Interfaces and the Effects of Ta2O5 Film
           Density on the Forming Process in Atomic Switch Structures
    • Authors: Tohru Tsuruoka; Ilia Valov, Stefan Tappertzhofen, Jan van den Hurk, Tsuyoshi Hasegawa, Rainer Waser, Masakazu Aono
      Abstract: Cu and Ag redox reactions at the interfaces with Ta2O5 and the impact of Ta2O5 film density on the forming process of Cu,Ag/Ta2O5/Pt atomic switch structures are investigated. Cyclic voltammetry measurements revealed that under positive bias to the Cu (Ag) electrode, Cu is preferentially oxidized to Cu2+, while Ag is oxidized to Ag+ ions. Subsequent negative bias causes a reduction of oxidized Cu (Ag) ions at the interfaces. The diffusion coefficient of the Cu and Ag ions in the Ta2O5 film is estimated from the results from different bias voltage sweep rates. It is also found that the redox current is enhanced and the forming voltage of the Cu/Ta2O5/Pt cell is reduced when the density of the Ta2O5 film is decreased. This result indicates the importance of the structural properties of the matrix oxide film in understanding and controlling resistive switching behavior. Redox reactions at the Ag,Cu/Ta2O5 interfaces and the impacts of Ta2O5 film density on the electroforming process of Ag,Cu/Ta2O5/Pt structures are clarified. When the density of the Ta2O5 film is decreased, the redox current is enhanced and the forming voltage is reduced. This finding contributes to a detailed understanding and control of the resistive switching behavior of oxide‐based atomic switches.
      PubDate: 2015-06-01T14:55:25.017149-05:
      DOI: 10.1002/adfm.201500853
       
  • Dual Targeted Immunotherapy via In Vivo Delivery of Biohybrid
           RNAi‐Peptide Nanoparticles to Tumor‐Associated Macrophages and
           Cancer Cells
    • Authors: João Conde; Chenchen Bao, Yeqi Tan, Daxiang Cui, Elazer R. Edelman, Helena S. Azevedo, Hugh J. Byrne, Natalie Artzi, Furong Tian
      Abstract: Lung cancer is associated with very poor prognosis and considered one of the leading causes of death worldwide. Here, highly potent and selective biohybrid RNA interference (RNAi)‐peptide nanoparticles (NPs) are presented that can induce specific and long‐lasting gene therapy in inflammatory tumor associated macrophages (TAMs), via an immune modulation of the tumor milieu combined with tumor suppressor effects. The data here prove that passive gene silencing can be achieved in cancer cells using regular RNAi NPs. When combined with M2 peptide–based targeted immunotherapy that immuno‐modulates TAMs cell population, a synergistic effect and long‐lived tumor eradication can be observed along with increased mice survival. Treatment with low doses of siRNA (ED50 0.0025–0.01 mg kg−1) in a multi and long‐term dosing system substantially reduces the recruitment of inflammatory TAMs in lung tumor tissue, reduces tumor size (≈95%), and increases animal survival (≈75%) in mice. The results here suggest that it is likely that the combination of silencing important genes in tumor cells and in their supporting immune cells in the tumor microenvironment, such as TAMs, will greatly improve cancer clinical outcomes. Immunomodulation using RNA interference (RNAi) nanoparticles against tumor associated immune cells and cancer cells at the same time is presented. Using a multi and long‐term dosing system, the administration of RNAi nanoparticles targeting tumor associated macrophages substantially reduces the recruitment of these inflammatory immune cells in lung tumor tissue, reduces tumor size (≈95%), and increases animal survival (≈75%) in mice.
      PubDate: 2015-06-01T14:55:20.188-05:00
      DOI: 10.1002/adfm.201501283
       
  • Confined Sulfur in Microporous Carbon Renders Superior Cycling Stability
           in Li/S Batteries
    • Authors: Yunhua Xu; Yang Wen, Yujie Zhu, Karen Gaskell, Katie A. Cychosz, Bryan Eichhorn, Kang Xu, Chunsheng Wang
      Abstract: The use of sulfur in the next generation Li‐ion batteries is currently precluded by its poor cycling stability caused by irreversible Li2S formation and the dissolution of soluble polysulfides in organic electrolytes that leads to parasitic cell reactions. Here, a new C/S cathode material comprising short‐chain sulfur species (predominately S2) confined in carbonaceous subnanometer and the unique charge mechanism for the subnano‐entrapped S2 cathodes are reported. The first charge–discharge cycle of the C/S cathode in the carbonate electrolyte forms a new type of thiocarbonate‐like solid electrolyte interphase (SEI). The SEI coated C/S cathode stably delivers ≈600 mAh g−1 capacity over 4020 cycles (0.0014% loss cycle−1) at ≈100% Coulombic efficiency. Extensive X‐ray photoelectron spectroscopy analysis of the discharged cathodes shows a new type of S2 species and a new carbide‐like species simultaneously, and both peaks disappear upon charging. These data suggest a new sulfur redox mechanism involving a separated Li+/S2− ion couple that precludes Li2S compound formation and prevents the dissolution of soluble sulfur anions. This new charge/discharge process leads to remarkable cycling stability and reversibility. A new sulfur chemistry is created with the sequestration of short‐chain sulfur species into subnanometer cavities and the charge delocalization between them and the carbonaceous host. Highly reversible capacities achieved at almost 100% Coulombic efficiency over 4020 cycles are demonstrated. This new charge/discharge mechanism opens up new possibilities for designing nanostructured cathode materials for rechargeable Li/S battery chemistry.
      PubDate: 2015-06-01T14:54:26.389424-05:
      DOI: 10.1002/adfm.201500983
       
  • Surface Engineering: Locally and Dynamically Controllable Surface
           Topography Through the Use of Particle‐Enhanced Soft Composites
           (Adv. Funct. Mater. 24/2015)
    • Authors: Mark Guttag; Mary C. Boyce
      Pages: 3617 - 3617
      Abstract: Creating tunable and reversible surfaces is an interesting challenge with no single solution. On page 3641, M. Guttag and M. C. Boyce present a new approach using a composite of stiff particles embedded into a soft matrix which provides a wide range of tunable and locally controllable surface topographies. By applying an external load to the composite, complex surface topographies take shape. (Photo credit: Felice C. Frankel.)
      PubDate: 2015-06-22T09:29:12.002065-05:
      DOI: 10.1002/adfm.201570158
       
  • Thermoelectrics: From Bonding Asymmetry to Anharmonic Rattling in
           Cu12Sb4S13 Tetrahedrites: When Lone‐Pair Electrons Are Not So Lonely
           (Adv. Funct. Mater. 24/2015)
    • Authors: Wei Lai; Yuxing Wang, Donald T. Morelli, Xu Lu
      Pages: 3618 - 3618
      Abstract: Tetrahedrites were recently discovered to be high‐performance thermoelectrics but the chemical and structural origins of the rattling guests and resultant low thermal conductivity remain elusive. On page 3648, W. La and team establish a clear connection between the local bonding asymmetry and anharmonic rattling modes in Cu12Sb4S13 tetrahedrites, enabled by the chemically active electron lone pairs.
      PubDate: 2015-06-22T09:29:06.203582-05:
      DOI: 10.1002/adfm.201570159
       
  • Contents: (Adv. Funct. Mater. 24/2015)
    • Pages: 3619 - 3625
      PubDate: 2015-06-22T09:29:06.046945-05:
      DOI: 10.1002/adfm.201570160
       
  • Hybrid Improper Ferroelectricity in Multiferroic Superlattices:
           Finite‐Temperature Properties and Electric‐Field‐Driven
           Switching of Polarization and Magnetization
    • Authors: Bin Xu; Dawei Wang, Hong Jian Zhao, Jorge Íñiguez, Xiang Ming Chen, Laurent Bellaiche
      Pages: 3626 - 3633
      Abstract: The so‐called hybrid improper ferroelectricity (HIF) mechanism allows to create an electrical polarization by assembling two nonpolar materials within a superlattice. It may also lead to the control of the magnetization by an electric field when these two nonpolar materials are magnetic in nature, which is promising for the design of novel magneto‐electric devices. However, several issues of fundamental and technological importance are presently unknown in these hybrid improper ferroelectrics. Examples include the behaviors of its polarization and dielectric response with temperature, and the paths to switch both the polarization and magnetization under electric fields. Here, an effective Hamiltonian scheme is used to study the multiferroic properties of the model superlattice (BiFeO3)1/(NdFeO3)1. Along with the development of a novel Landau‐type potential, this approach allows to answer and understand all the aforementioned issues at both microscopic and macroscopic levels. In particular, the polarization and dielectric response are both found to adopt temperature dependences, close to the phase transition, that agree with the behavior expected for first‐order improper ferroelectrics. And most importantly, a five‐state path resulting in the switching of polarization and magnetization under an electric field, via the reversal of antiphase octahedral tiltings, is also identified. The hybrid improper ferroelectricity (HIF) mechanism generates el ectrical polarization in a superlattice made of two nonpolar materials and is promising for the design of novel multiferroics. A first‐principles‐based technique is used here to resolve unknown issues about HIF, including the discovery of a path allowing the switching of polarization and magnetization, and how the HIF transition occurs upon cooling.
      PubDate: 2015-05-12T01:52:48.683946-05:
      DOI: 10.1002/adfm.201501113
       
  • Controllable Broadband Absorption in the Mixed Phase of Metamagnets
    • Authors: Matej Pregelj; Oksana Zaharko, Andrej Zorko, Matjaž Gomilšek, Oles Sendetskyi, Axel Günther, Mykhaylo Ozerov, Sergei A. Zvyagin, Hubertus Luetkens, Christopher Baines, Vladimir Tsurkan, Alois Loidl
      Pages: 3634 - 3640
      Abstract: Materials with broad absorption bands are highly desirable for electromagnetic filtering and processing applications, especially if the absorption can be externally controlled. Here, a new class of broadband‐absorption materials is introduced. Namely, layered metamagnets exhibit an electromagnetic excitation continuum in the magnetic‐field‐induced mixed ferro‐ and anti­ferromagnetic phase. Employing a series of complementary experimental techniques involving neutron scattering, muon spin relaxation, specific heat, ac and dc magnetization measurements, and electron magnetic resonance, a detailed magnetic phase diagram of Cu3Bi(SeO3)2O2Br is determined and it is found that the excitations in the mixed phase extend over at least ten decades of frequency. The results, which reveal a new dynamical aspect of the mixed phase in metamagnets, open up a novel approach to controllable microwave filtering. Controllable broadband microwave absorption is highly desired for improved electromagnetic shielding and superior signal processing. The absorption of the microwaves in an extremely wide frequency range is demonstrated in layered metamagnets. The effect is controlled by the external magnetic field and should be easily reproduced in artificial metamagnets, that is, magnetic multilayers, allowing a direct tuning of the functional properties.
      PubDate: 2015-05-15T08:25:24.663236-05:
      DOI: 10.1002/adfm.201500702
       
  • Locally and Dynamically Controllable Surface Topography Through the Use of
           Particle‐Enhanced Soft Composites
    • Authors: Mark Guttag; Mary C. Boyce
      Pages: 3641 - 3647
      Abstract: A new class of soft composite materials with dynamically tunable and reversible surface topographies is introduced that allows a wide diversity and local positioning of surface features. The particle‐enhanced soft composites are comprised of a soft elastomeric matrix with relatively stiff particles embedded below the surface. Upon application of external stimuli, a surface that is originally smooth and flat (or of other initial topology) transforms to engineered surface topographies. Finite element based micromechanical simulations are used to design and study the hybrid material structures that govern the evolution in surface topographies. Physical prototypes are fabricated using multimaterial 3D‐printing, and then experimentally evaluated to validate the accuracy of our simulations. It is demonstrated that a rich variety in periodic and random surface features including variable waves, crease‐like features, flat apexes, and valleys can be attained by changing different dimensionless geometric parameters (e.g., relative particle size, shapes, spacing, and distributions). Furthermore, these surface features can be locally controlled by positioning of particles and do not rely on instabilities. The material design depends primarily on the geometry of the particles and the arrays, making this approach to on‐demand custom and reversible surface patterning applicable over a wide range of size scales. Creating tunable and reversible surfaces is an interesting challenge with no single solution. A new approach using a composite of stiff particles embedded into a soft matrix provides a wide range of tunable and locally controllable surface topographies. By applying an external load to the composite, complex surface topographies take shape.
      PubDate: 2015-05-07T11:26:58.230891-05:
      DOI: 10.1002/adfm.201501035
       
  • From Bonding Asymmetry to Anharmonic Rattling in Cu12Sb4S13 Tetrahedrites:
           When Lone‐Pair Electrons Are Not So Lonely
    • Authors: Wei Lai; Yuxing Wang, Donald T. Morelli, Xu Lu
      Pages: 3648 - 3657
      Abstract: Some of the best thermoelectrics are complex materials with rattling guests inside oversized atomic cages. Understanding the chemical and structural origins of the rattling behavior is essential to the design of thermoelectric materials. In this work, a clear connection is established between the local bonding asymmetry and anharmonic rattling modes in tetrahedrite thermoelectrics, enabled by the chemically active electron lone pairs. The studies reveal a five‐atom atomic cage Sb[CuS3]Sb in Cu12Sb4S13 tetrahedrites that exhibits strong local bonding asymmetry: covalent bonding inside the CuS3 trigonal plane and weak out‐of‐plane bonding induced by the lone‐pair electrons of Sb. This bonding asymmetry leads to out‐of‐plane rattling modes that are quasilocalized and anharmonic with low frequency and large amplitude, and are likely the origin of low thermal conductivity in tetrahedrites. Such knowledge highlights the importance of local structure asymmetry and lone‐pair atoms in driving anharmonic rattling, providing a stepping stone to the discovery and design of next‐generation thermoelectrics. A strong local bonding asymmetry is identified inside a Sb[CuS3]Sb atomic cage, in which Cu (blue) forms strong covalent bonding with S (green and yellow) and forms weak covalent bonding with one of the Sb atoms (brown) enabled by the lone‐pair electrons. This bonding asymmetry causes the out‐of‐plane anharmonic rattling which leads to the low thermal conductivity.
      PubDate: 2015-05-12T10:18:44.628181-05:
      DOI: 10.1002/adfm.201500766
       
  • Self‐Assembled, Millimeter‐Sized TIPS‐Pentacene
           Spherulites Grown on Partially Crosslinked Polymer Gate Dielectric
    • Authors: Hocheon Yoo; Hyun Ho Choi, Tae Joo Shin, Taiuk Rim, Kilwon Cho, Sungjune Jung, Jae‐Joon Kim
      Pages: 3658 - 3665
      Abstract: Here, a highly crystalline and self‐assembled 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐Pentacene) thin films formed by simple spin‐coating for the fabrication of high‐performance solution‐processed organic field‐effect transistors (OFETs) are reported. Rather than using semiconducting organic small‐molecule–insulating polymer blends for an active layer of an organic transistor, TIPS‐Pentacene organic semiconductor is separately self‐assembled on partially crosslinked poly‐4‐vinylphenol:poly(melamine‐co‐formaldehyde) (PVP:PMF) gate dielectric, which results in a vertically segregated semiconductor‐dielectric film with millimeter‐sized spherulite‐crystalline morphology of TIPS‐Pentacene. The structural and electrical properties of TIPS‐Pentacene/PVP:PMF films have been studied using a combination of polarized optical microscopy, atomic force microscopy, 2D‐grazing incidence wide‐angle X‐ray scattering, and secondary ion mass spectrometry. It is finally demonstrated a high‐performance OFETs with a maximum hole mobility of 3.40 cm2 V−1 s−1 which is, to the best of our knowledge, one of the highest mobility values for TIPS‐Pentacene OFETs fabricated using a conventional solution process. It is expected that this new deposition method would be applicable to other small molecular semiconductor–curable polymer gate dielectric systems for high‐performance organic electronic applications. Partial crosslinking of polymer gate‐dielectrics (pc‐PVP:PMF) allows semiconducting small molecules in solvent to permeate into it. The solvent evaporation during spinning promotes the extraction of TIPS‐Pentacene solution onto pc‐PVP:PMF surface. The residual solvent in pc‐PVP:PMF network evaporates slowly, so it helps millimeter‐sized crystallization of TIPS‐Pentacene molecules. Consequently, the OFET devices exhibit high mobilities with maximum value of 3.40 cm2 V−1 s−1.
      PubDate: 2015-05-07T11:27:03.423255-05:
      DOI: 10.1002/adfm.201501381
       
  • Synthesis of Layer‐Tunable Graphene: A Combined Kinetic Implantation
           and Thermal Ejection Approach
    • Authors: Gang Wang; Miao Zhang, Su Liu, Xiaoming Xie, Guqiao Ding, Yongqiang Wang, Paul K. Chu, Heng Gao, Wei Ren, Qinghong Yuan, Peihong Zhang, Xi Wang, Zengfeng Di
      Pages: 3666 - 3675
      Abstract: Layer‐tunable graphene has attracted broad interest for its potentials in nanoelectronics applications. However, synthesis of layer‐tunable graphene by using traditional chemical vapor deposition method still remains a great challenge due to the complex experimental parameters and the carbon precipitation process. Herein, by performing ion implantation into a Ni/Cu bilayer substrate, the number of graphene layers, especially single or double layer, can be controlled precisely by adjusting the carbon ion implant fluence. The growth mechanism of the layer‐tunable graphene is revealed by monitoring the growth process, it is observed that the entire implanted carbon atoms can be expelled toward the substrate surface and thus graphene with designed layer number can be obtained. Such a growth mechanism is further confirmed by theoretical calculations. The proposed approach for the synthesis of layer‐tunable graphene offers more flexibility in the experimental conditions. Being a core technology in microelectronics processing, ion implantation can be readily implemented in production lines and is expected to expedite the application of graphene to nanoelectronics. By taking advantage of the dual metal substrate of Ni‐coated Cu foils, the precise control of layer number of graphene by ion implantation is demonstrated and the layer number of graphene strictly corresponds to the implantation fluence as expected. Besides, the formation mechanism is explored by the experimental analysis in detail and confirmed by the theoretical calculations.
      PubDate: 2015-05-04T10:00:26.181618-05:
      DOI: 10.1002/adfm.201500981
       
  • Fluorescence: Dichotomy in the Lithiation Pathway of Ellipsoidal and
           Platelet LiFePO4 Particles Revealed through Nanoscale Operando
           State‐of‐Charge Imaging (Adv. Funct. Mater. 24/2015)
    • Authors: Yiyang Li; Johanna Nelson Weker, William E. Gent, David N. Mueller, Jongwoo Lim, Daniel A. Cogswell, Tolek Tyliszczak, William C. Chueh
      Pages: 3676 - 3676
      Abstract: A nanoscale liquid imaging platform is developed by W. C. Chueh and co‐workers to track lithium intercalation in LiFePO4 electrodes. The results on page 3677 show that the intercalation pathway strongly depends on the particle morphology and synthesis protocol. Highly faceted ellipsoidal particles intercalate sequentially, with a small number of actively‐intercalating particles and low electrode utilization. Platelet particles, on the other hand, intercalate simultaneously with a more uniform current distribution.
      PubDate: 2015-06-22T09:29:02.492211-05:
      DOI: 10.1002/adfm.201570162
       
  • Dichotomy in the Lithiation Pathway of Ellipsoidal and Platelet LiFePO4
           Particles Revealed through Nanoscale Operando State‐of‐Charge
           Imaging
    • Authors: Yiyang Li; Johanna Nelson Weker, William E. Gent, David N. Mueller, Jongwoo Lim, Daniel A. Cogswell, Tolek Tyliszczak, William C. Chueh
      Pages: 3677 - 3687
      Abstract: LiFePO4 is a promising phase‐separating battery electrode and a model system for studying lithiation. The role of particle synthesis and the corresponding particle morphology on the nanoscale insertion and migration of Li is not well understood, and elucidating the intercalation pathway is crucial toward improving battery performance. A synchrotron operando liquid X‐ray imaging platform is developed to track the migration of Li in LiFePO4 electrodes with single‐particle sensitivity. Lithiation is tracked in two particle types—ellipsoidal and platelet—while the particles cycle in an organic liquid electrolyte, and the results show a clear dichotomy in the intercalation pathway. The ellipsoidal particles intercalate sequentially, concentrating the current in a small number of actively intercalating particles. At the same cycling rate, platelet particles intercalate simultaneously, leading to a significantly more uniform current distribution. Assuming that the particles intercalate through a single‐phase pathway, it is proposed that the two particle types exhibit different surface properties, a result of different synthesis procedures, which affect the surface reactivity of LiFePO4. Alternatively, if the particles intercalate through nucleation and growth, the larger size of platelet particles may account for the dichotomy. Beyond providing particle engineering insights, the operando microscopy platform enables new opportunities for nanoscale chemical imaging of liquid‐based electrochemical systems. A nanoscale liquid imaging platform is developed to track lithium intercalation in LiFePO4 electrodes. The results show that the intercalation pathway strongly depends on the particle morphology and synthesis protocol. Highly faceted ellipsoidal particles intercalate sequentially, with a small number of actively intercalating particles and low electrode utilization. Platelet particles, on the other hand, intercalate simultaneously with a more uniform current distribution.
      PubDate: 2015-05-12T10:18:49.434977-05:
      DOI: 10.1002/adfm.201500286
       
  • Stretchable‐Rubber‐Based Triboelectric Nanogenerator and Its
           Application as Self‐Powered Body Motion Sensors
    • Authors: Fang Yi; Long Lin, Simiao Niu, Po Kang Yang, Zhaona Wang, Jun Chen, Yusheng Zhou, Yunlong Zi, Jie Wang, Qingliang Liao, Yue Zhang, Zhong Lin Wang
      Pages: 3688 - 3696
      Abstract: A stretchable‐rubber‐based (SR‐based) triboelectric nanogenerator (TENG) is developed that can not only harvest energy but also serve as self‐powered multifunctional sensors. It consists of a layer of elastic rubber and a layer of aluminum film that acts as the electrode. By stretching and releasing the rubber, the changes of triboelectric charge distribution/density on the rubber surface relative to the aluminum surface induce alterations to the electrical potential of the aluminum electrode, leading to an alternating charge flow between the aluminum electrode and the ground. The unique working principle of the SR‐based TENG is verified by the coupling of numerical calculations and experimental measurements. A comprehensive study is carried out to investigate the factors that may influence the output performance of the SR‐based TENG. By integrating the devices into a sensor system, it is capable of detecting movements in different directions. Moreover, the SR‐based TENG can be attached to a human body to detect diaphragm breathing and joint motion. This work largely expands the applications of TENG not only as effective power sources but also as active sensors; and opens up a new prospect in future electronics. A stretchable‐rubber‐based triboelectric nanogenerator is developed, which can not only harvest energy but also serve as self‐powered multifunctional sensors. It is composed of a layer of elastic rubber and a layer of aluminum film that acts as the electrode. Electrical outputs are generated by stretching and releasing the rubber. It can be attached to a human body to detect diaphragm breathing and joint motion.
      PubDate: 2015-05-08T14:16:44.462438-05:
      DOI: 10.1002/adfm.201500428
       
  • Epidermal Systems: Soft Core/Shell Packages for Stretchable Electronics
           (Adv. Funct. Mater. 24/2015)
    • Authors: Chi Hwan Lee; Yinji Ma, Kyung‐In Jang, Anthony Banks, Taisong Pan, Xue Feng, Jae Soon Kim, Daeshik Kang, Milan S. Raj, Bryan L. McGrane, Briana Morey, Xianyan Wang, Roozbeh Ghaffari, Yonggang Huang, John A. Rogers
      Pages: 3697 - 3697
      Abstract: Human skin‐like core/shell material encapsulating structures for wearable electronics serve to minimize interface stresses and mechanical constraints on natural body motions, with ability to strain isolate the active devices. On page 3698, Y. Huang, J. A. Rogers, and co‐workers show how integrating emerging commercial classes of stretchable electronics into this type of structure provides systems with capabilities in continuous, precision wireless monitoring of motion and skin temperatures during exercise.
      PubDate: 2015-06-22T09:29:06.251626-05:
      DOI: 10.1002/adfm.201570163
       
  • Soft Core/Shell Packages for Stretchable Electronics
    • Authors: Chi Hwan Lee; Yinji Ma, Kyung‐In Jang, Anthony Banks, Taisong Pan, Xue Feng, Jae Soon Kim, Daeshik Kang, Milan S. Raj, Bryan L. McGrane, Briana Morey, Xianyan Wang, Roozbeh Ghaffari, Yonggang Huang, John A. Rogers
      Pages: 3698 - 3704
      Abstract: This paper presents materials and core/shell architectures that provide optimized mechanical properties in packages for stretchable electronic systems. Detailed experimental and theoretical studies quantitatively connect the geometries and elastic properties of the constituent materials to the overall mechanical responses of the integrated systems, with a focus on interfacial stresses, effective modulus, and maximum extent of elongation. Specific results include core/shell designs that lead to peak values of the shear and normal stresses on the skin that remain less than 10 kPa even for applied strains of up to 20%, thereby inducing minimal somatosensory perception of the device on the human skin. Additional, strain‐limiting mesh structures embedded in the shell improve mechanical robustness by protecting the active components from strains that would otherwise exceed the fracture point. Demonstrations in precommercial stretchable electronic systems illustrate the utility of these concepts. Human skin‐like core/shell material structure is presented for use in wearable, stretchable electronic systems. Here, an ultralow‐modulus elastomer (core) with a thin enclosure (shell) serves to minimize interface stresses and mechanical constraints on natural motions, with ability to strain‐isolate the electronics. Demonstration examples exploit emerging commercial classes of stretchable electronic system to wirelessly monitor a subject's motion and body temperature during exercise.
      PubDate: 2015-05-15T08:24:55.411418-05:
      DOI: 10.1002/adfm.201501086
       
  • Phenylboronic Acid‐Decorated Chondroitin Sulfate A‐Based
           Theranostic Nanoparticles for Enhanced Tumor Targeting and Penetration
    • Authors: Jae‐Young Lee; Suk‐Jae Chung, Hyun‐Jong Cho, Dae‐Duk Kim
      Pages: 3705 - 3717
      Abstract: Phenylboronic acid‐functionalized chondroitin sulfate A (CSA)–deoxycholic‐acid (DOCA)‐based nanoparticles (NPs) are prepared for tumor targeting and penetration. (3‐Aminomethylphenyl)boronic acid (AMPB) is conjugated to CSA–DOCA conjugate via amide bond formation, and its successful synthesis is confirmed using proton nuclear magnetic resonance spectroscopy (1H‐NMR). Doxorubicin (DOX)‐loaded CSA–DOCA–AMPB NPs with a mean diameter of ≈200 nm, a narrow size distribution, negative zeta potential, and spherical morphology are prepared. DOX release from NPs is enhanced at acidic pH compared to physiological pH. CSA–DOCA–AMPB NPs exhibit improved cellular uptake in A549 (human lung adenocarcinoma) cells and penetration into A549 multicellular spheroids compared to CSA–DOCA NPs as evidenced by confocal laser scanning microscopy and flow cytometry. In vivo tumor targeting and penetrating by CSA–DOCA–AMPB NPs, based on both CSA–CD44 receptor and boronic acid–sialic acid interactions, is revealed using near‐infrared fluorescence (NIRF) imaging. Penetration of NPs to the core of the tumor mass is observed in an A549 tumor xenografted mouse model and verified by three‐dimensional NIRF imaging. Multiple intravenous injections of DOX‐loaded CSA–DOCA–AMPB NPs efficiently inhibit the growth of A549 tumor in the xenografted mouse model and increase apoptosis. These boronic acid‐rich NPs are promising candidates for cancer therapy and imaging. (3‐Aminomethylphenyl)boronic acid ­(AMPB)‐­functionalized chondroitin sulfate A (CSA)–deoxycholic acid (DOCA)‐based nanoparticles (NPs) are prepared for anticancer drug delivery and cancer diagnosis. Doxorubicin (DOX)‐loaded CSA–DOCA–AMPB NPs exhibit improved targeting, penetration, and therapeutic efficacies for CD44 receptor‐expressed tumors, compared to CSA–DOCA NPs, via CSA–CD44 receptor and boronic‐acid–sialic‐acid interactions.
      PubDate: 2015-05-08T14:16:36.637113-05:
      DOI: 10.1002/adfm.201500680
       
  • Liquid‐Metal Electrode for High‐Performance Triboelectric
           Nanogenerator at an Instantaneous Energy Conversion Efficiency of 70.6%
    • Authors: Wei Tang; Tao Jiang, Feng Ru Fan, Ai Fang Yu, Chi Zhang, Xia Cao, Zhong Lin Wang
      Pages: 3718 - 3725
      Abstract: Harvesting ambient mechanical energy is a key technology for realizing self‐powered electronics, which has tremendous applications in wireless sensing networks, implantable devices, portable electronics, etc. The currently reported triboelectric nanogenerator (TENG) mainly uses solid materials, so that the contact between the two layers cannot be 100% with considering the roughness of the surfaces, which greatly reduces the total charge density that can be transferred and thus the total energy conversion efficiency. In this work, a liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is developed for high power generation through conversion of mechanical energy, which allows a total contact between the metal and the dielectric. Due to that the liquid–solid contact induces large contacting surface and its shape adaptive with the polymer thin films, the LM‐TENG exhibits a high output charge density of 430 μC m−2, which is four to five times of that using a solid thin film electrode. And its power density reaches 6.7 W m−2 and 133 kW m−3. More importantly, the instantaneous energy conversion efficiency is demonstrated to be as high as 70.6%. This provides a new approach for improving the performance of the TENG for special applications. Furthermore, the liquid easily fluctuates, which makes the LM‐TENG inherently suitable for vibration energy harvesting. A liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is developed for high power generation through conversion of mechanical energy, which allows total contact between the metal and the dielectric. The LM‐TENG exhibits a high output charge density of 430 μC m−2, which is four to five times of that using a solid thin film electrode. An instantaneous energy conversion efficiency as high as 70.6% is demonstrated.
      PubDate: 2015-05-12T01:52:59.845798-05:
      DOI: 10.1002/adfm.201501331
       
  • Formation of Bi2WO6 Bipyramids with Vacancy Pairs for Enhanced
           Solar‐Driven Photoactivity
    • Authors: Gong Zhang; Ziyu Hu, Meng Sun, Yang Liu, Limin Liu, Huijuan Liu, Chin‐Pao Huang, Jiuhui Qu, Jinghong Li
      Pages: 3726 - 3734
      Abstract: In order to improve the photoactivity, many attempts have focused on increasing the exposure of highly reactive surfaces on crystals. However, the connection between the reactive surfaces and enhancement is still elusive. Herein, Bi2WO6 nanostructured bipyramids with a large fraction of {100} facets are fabricated by the solvothermal method. The formation of “Bi–O” dimer vacancy pairs on the {100} high‐energy facets is responsible for the reduction in band gap and the decrease in the recombination of photo‐excited charge carriers, which is unambiguously confirmed by the positron annihilation spectra (PAS), X‐ray photoelectron spectrum (XPS), and theoretical calculations. The effective separation of electron–hole pairs and the narrowing bandgap significantly improve the photoactivity of Bi2WO6 nanobipyramids, especially under solar light irradiation. These findings can be applied broadly to the design and fabrication of energy efficient and robust catalysts. Bi2WO6 nanobipyramid is successfully fabricated via a facile strategy in which “Bi–O” vacancy pairs are key to increase its solar‐light photoactivity.
      PubDate: 2015-05-13T15:12:34.571741-05:
      DOI: 10.1002/adfm.201501009
       
  • Rapid Thiol‐Yne‐Mediated Fabrication and Dual
           Postfunctionalization of Micro‐Resolved 3D Mesostructures
    • Authors: Alexander S. Quick; Andres de los Santos Pereira, Michael Bruns, Tiemo Bückmann, Cesar Rodriguez‐Emmenegger, Martin Wegener, Christopher Barner‐Kowollik
      Pages: 3735 - 3744
      Abstract: 3D mesostructures with a height of up to 1 mm and micrometer feature size are fabricated employing a writing speed of 1 cm s−1 via direct laser writing utilizing a novel functional photoresist based on the radical coupling reaction of thiols and alkynes. The refractive index of the resist—consisting of a tetrafunctional thiol, a tetrafunctional alkyne and a photoinitiator—is tailored to be compatible with the employed high numerical aperture (NA) objective lens, thus enabling a Dip‐in configuration. Mesostructures are characterized by scanning electron microscopy, optical photography, and nondestructive 3D time‐of‐flight secondary ion mass spectrometry. Woodpile photonic crystals are fabricated as benchmark structures in order to investigate the axial resolution. Verification of the chemical fabrication mechanism is achieved via transmission Fourier transform infrared (FTIR) spectroscopy of fabricated cuboid structures by monitoring the decrease of corresponding thiol and alkyne absorption peaks. Postmodification reactions, namely the thiol‐Michael addition and the copper‐catalyzed azide alkyne cycloaddition, are conducted employing residual thiols and alkynes throughout the cuboid structures. Successful dual and orthogonal modification throughout the structure and on the surface is achieved and verified utilizing transmission FTIR spectroscopy and time‐of‐flight secondary ion mass spectrometry. Reactive 3D mesostructures with micrometer feature size are fabricated via dip‐in direct laser writing employing the radical thiol‐yne coupling reaction. Axial resolution and the polymerization process of the photoresist are investigated. Residual thiols and alkynes are exploited for postmodification reactions, namely thiol‐Michael addition and copper‐catalyzed azide alkyne cycloaddition, demonstrating successful dual functionalization throughout the structure and on the surface.
      PubDate: 2015-05-15T08:25:31.937772-05:
      DOI: 10.1002/adfm.201500683
       
  • A High‐Capacitance Salt‐Free Dielectric for
           Self‐Healable, Printable, and Flexible Organic Field Effect
           Transistors and Chemical Sensor
    • Authors: Weiguo Huang; Kalpana Besar, Yong Zhang, Shyuan Yang, Gregory Wiedman, Yu Liu, Wenmin Guo, Jian Song, Kevin Hemker, Kalina Hristova, Ionnis J. Kymissis, Howard E. Katz
      Pages: 3745 - 3755
      Abstract: Printable and flexible electronics attract sustained attention for their low cost, easy scale up, and potential application in wearable and implantable sensors. However, they are susceptible to scratching, rupture, or other damage from bending or stretching due to their “soft” nature compared to their rigid counterparts (Si‐based electronics), leading to loss of functionality. Self‐healing capability is highly desirable for these “soft” electronic devices. Here, a versatile self‐healing polymer blend dielectric is developed with no added salts and it is integrated into organic field transistors (OFETs) as a gate insulator material. This polymer blend exhibits an unusually high thin film capacitance (1400 nF cm−2 at 120 nm thickness and 20–100 Hz). Furthermore, it shows pronounced electrical and mechanical self‐healing behavior, can serve as the gate dielectric for organic semiconductors, and can even induce healing of the conductivity of a layer coated above it together with the process of healing itself. Based on these attractive properties, we developed a self‐healable, low‐voltage operable, printed, and flexible OFET for the first time, showing promise for vapor sensing as well as conventional OFET applications. Printable and flexible, low‐voltage operating, particularly self‐healable electronics is a highly desirable suite of technologies proposed for future intelligent electronic devices such as body monitors and window displays. A key material used in printed logic circuits is reported, the “gate dielectric” insulator, with which all these attributes for the first time are demonstrated.
      PubDate: 2015-05-12T01:53:55.851452-05:
      DOI: 10.1002/adfm.201404228
       
  • Thickness Dependence of the Mechanical Properties of Free‐Standing
           Graphene Oxide Papers
    • Authors: Tao Gong; Do Van Lam, Renlong Liu, Sejeong Won, Yun Hwangbo, Sanghyuk Kwon, Jinseon Kim, Ke Sun, Jae‐Hyun Kim, Seung‐Mo Lee, Changgu Lee
      Pages: 3756 - 3763
      Abstract: Graphene oxide (GO) papers are candidates for structural materials in modern technology due to their high specific strength and stiffness. The relationship between their mechanical properties and structure needs to be systematically investigated before they can be applied to the broad range fields where they have potential. Herein, the mechanical properties of GO papers with various thicknesses (0.5–100 μm) are investigated using bulge and tensile test methods; this includes the Young's modulus, fracture strength, fracture strain, and toughness. The Young's modulus, fracture strength, and toughness are found to decrease with increasing thickness, with the first two exhibiting differences by a factor of four. In contrast, the fracture strain slightly increases with thickness. Transmission electron, scanning electron, and atomic force microscopy indicate that the mechanical properties vary with thickness due to variations in the inner structure and surface morphology, such as crack formation and surface roughness. Thicker GO papers are weaker because they contain more voids that are produced during the fabrication process. Surface wrinkles and residual stress are found to result in increased fracture strain. Determination of this structure–property relationship provide improved guidelines for the use of GO‐based thin‐film materials in mechanical structures. The mechanical properties of graphene oxide (GO) papers are shown to be thickness‐dependent. This dependence arises from the micro‐ and macrostructure formed during the fabrication process; microscopy studies reveal that corrugations, void defects, and surface wrinkles all influence the mechanical properties. Establishing this structure–property relationship is expected to enable improved guidelines for the application of GO to mechanical structures.
      PubDate: 2015-05-12T01:53:38.054603-05:
      DOI: 10.1002/adfm.201500998
       
  • Facile Fabrication of Robust Organic Counterion‐Induced Vesicles:
           Reversible Thermal Behavior for Optical Temperature Sensor and Synergistic
           Catalyst upon Removal of Amine
    • Authors: Chuanqi Li; Shiyong Zhang, Jie Pang, Yao Wu, Zhongwei Gu
      Pages: 3764 - 3774
      Abstract: A general concept of organic counterion‐directed molecular strategy for thepreparation of robust vesicles is developed. Functional amphiphilic ammonium salts (L1‐L3) bearing readily available oligo‐ethyleneglycol‐based ligand 1 and single‐tailed fatty amines self‐assemble into vesicles with controllable sizes in aqueous media. The organic counterion‐induced vesicles (OCIVs) are characterized by dynamic light scattering, transmission electron microscopy, and acid triggered release of hydrophilic drug (DOX·HCl). The introduction of organic counterion not only plays an important role in vesicle construction, but also endows the material with greatly practical values. By virtue of alkynyl groups attached on the organic ligand, the OCIVs can be easily cross‐linked via thiol‐ene reaction to generate a robust material. Importantly, the cross‐linked OCIVs exploit reversible temperature‐dependant size change, which can be repeated over 10 times without appreciable size fluctuating. Based on the unique property, a robust luminescence temperature sensor with a useful detection range of 35–70 °C is developed. Besides, removing the amines buried in the polymerized OCIVs under acidic condition, the resulting carboxylic acid‐functionalized material is found to have unusual efficiency as “nanozyme” for acetal hydrolysis, which exhibits over 20‐fold rate acceleration compared with that catalyzed by 1 or benzoic acid. A general concept of organic counterion‐induced vesicles is established. The introduction of organic counterion not only plays an important role in vesicle construction, but also endows the material with greatly practical values. As examples, a robust luminescence temperature sensor and a highly efficient synergistic catalyst are developed successfully.
      PubDate: 2015-05-13T15:12:42.80367-05:0
      DOI: 10.1002/adfm.201500176
       
  • Mussel Byssus‐Like Reversible Metal‐Chelated Supramolecular
           Complex Used for Dynamic Cellular Surface Engineering and Imaging
    • Authors: Wen Li; Wei Bing, Sa Huang, Jinsong Ren, Xiaogang Qu
      Pages: 3775 - 3784
      Abstract: Inspired by the load‐bearing biostructures in nature, a multifunctional shell for encapsulating cell using the polyphenol–metal complexes is fabricated. The artificial shell is formed by cross‐linking of tannic acid and iron ion on cell surface. It can protect cells from unfriendly environments, including UV light irradiation and reactive oxygen damage. With the hybrid property of polyphenol and metal liands, the shell provides a versatile platform for cell surface engineering. The magnetic nanoparticles, DNA molecules, as well as the magnetic resonance imaging agents are easily incorporated into the shell. More interestingly, unlike the traditional passive coatings, here the shell can be controllably disassembled under external stimuli. The dynamic coating is used as a reversible element to regulate cell division and surface modification. The cell viability and protein expression experiments further confirm that the shell formation and degradation processes are biocompatible. This multifunctional coating strategy is applicable to multiple living cell types, including yeast cells, Escherichia coli bacteria, and mammalian cells. Therefore, this platform would be useful for living cell based fundamental research and biological applications. Inspired by nature, herein a versatile strategy is reported for encapsulating cells with polyphenolic metal coordination‐based shell. The shell provides powerful tools for simultaneously protecting cells and engineering cell surface with nanoparticles, bioactive molecules, and imaging agents. In addition, in contrast to traditional passive shell, the coating here can be removed on‐demand with stimuli to evoke the original feature of cells.
      PubDate: 2015-05-13T15:13:00.38641-05:0
      DOI: 10.1002/adfm.201500039
       
  • Self‐Healing Actuating Adhesive Based on Polyelectrolyte Multilayers
    • Authors: Yuanqing Gu; Nicole S. Zacharia
      Pages: 3785 - 3792
      Abstract: Creating actuators capable of mechanical motion in response to external stimuli is a key for design and preparation of smart materials. The lifetime of such materials is limited by their eventual wear. Here, self‐healable and adhesive actuating materials are demonstrated by taking advantage of the solvent responsive of weak polyelectrolyte multilayers consisting of branched poly(ethylenimine)/poly(acrylic acid) (BPEI/PAA). BPEI/PAA multilayers are dehydrated and contract upon contact with organic solvent and become sticky when wetted with water. By constructing an asymmetric heterostructure consisting of a responsive BPEI/PAA multilayer block and a nonresponsive component through either layer‐by‐layer assembly or the paste‐to‐curl process, smart films that actuate upon exposure to alcohol are realized. The curl degree, defined as degrees from horizontal that the actuated material reaches, can be as high as ≈228.9°. With evaporation of the ethanol, the curled film returns to its initial state, and water triggers fast self‐healing extends the actuator's lifetime. Meanwhile, the adhesive nature of the wet material allows it to be attached to various substrates for possible combination with hydrophobic functional surfaces and/or applications in biological environments. This self‐healable adhesive for controlled fast actuation represents a considerable advance in polyelectrolyte multilayers for design and fabrication of robust smart advanced materials. Self‐healable adhesive that actuates upon exposure to ethanol is developed by layer‐by‐layer assembly and paste‐to‐curl approaches. The degree of curling is easily controlled by controlling exposure to the organic solvent stimulus as well as engineering the thickness and modulus of the inert part of the actuator. The branched poly(ethylenimine)/poly(acrylic acid) film, which is the active component, can easily be self‐healed in water, prolonging lifetime of the actuator.
      PubDate: 2015-05-15T08:24:48.560703-05:
      DOI: 10.1002/adfm.201501055
       
  • Organic Electronics: Self‐Assembled, Millimeter‐Sized
           TIPS‐Pentacene Spherulites Grown on Partially Crosslinked Polymer
           Gate Dielectric (Adv. Funct. Mater. 24/2015)
    • Authors: Hocheon Yoo; Hyun Ho Choi, Tae Joo Shin, Taiuk Rim, Kilwon Cho, Sungjune Jung, Jae‐Joon Kim
      Pages: 3795 - 3795
      Abstract: In the study presented by K. Cho, S. Jung, J.‐J. Kim, and co‐workers on page 3658, partial crosslinking of polymer gate dielectrics (pc‐PVP:PMF) allows semiconducting small molecules in solvent to permeate into it. The solvent evaporation during spinning promotes the extraction of TIPS‐Pentacene solution onto pc‐PVP:PMF surface. The residual solvent in pc‐PVP:PMF network evaporates slowly, helping millimeter‐sized crystallization of TIPS‐Pentacene molecules. Consequently, the OFET devices exhibit high mobilities with maximum value of 3.40 cm2 V−1 s−1.
      PubDate: 2015-06-22T09:29:04.226474-05:
      DOI: 10.1002/adfm.201570164
       
  • Graphene: Synthesis of Layer‐Tunable Graphene: A Combined Kinetic
           Implantation and Thermal Ejection Approach (Adv. Funct. Mater. 24/2015)
    • Authors: Gang Wang; Miao Zhang, Su Liu, Xiaoming Xie, Guqiao Ding, Yongqiang Wang, Paul K. Chu, Heng Gao, Wei Ren, Qinghong Yuan, Peihong Zhang, Xi Wang, Zengfeng Di
      Pages: 3796 - 3796
      Abstract: On page 3666, Q. Yuan, Z. Di, and colleagues take advantage of the dual metal substrate of Ni‐coated Cu foils to precisely control of layer number of graphene by ion implantation and the layer number of graphene strictly corresponds to the implantation fluence as expected. Besides, the formation mechanism is explored in detail by the experimental analysis and confirmed by theoretical calculations.
      PubDate: 2015-06-22T09:29:03.373957-05:
      DOI: 10.1002/adfm.201570165
       
 
 
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