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  • Corrigendum: On the speed of piezostrain-mediated voltage-driven perpendicular magnetization reversal: a computational elastodynamics-micromagnetic phase-field study
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Ren-Ci Peng, Jia-Mian Hu, Long-Qing Chen, Ce-Wen Nan

    Corrigendum: On the speed of piezostrain-mediated voltage-driven perpendicular magnetization reversal: a computational elastodynamics-micromagnetic phase-field study NPG Asia Materials 9, e446 (October 2017). doi:10.1038/am.2017.193 Authors: Ren-Ci Peng, Jia-Mian Hu, Long-Qing Chen & Ce-Wen Nan

    更新日期:2017-10-27
  • Nature-inspired thermo-responsive multifunctional membrane adaptively hybridized with PNIPAm and PPy
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Hyejeong Kim, Kiwoong Kim, Sang Joon Lee

    Specialized plant tissues, such as the epidermis of a leaf covered with stomata, consist of soft materials with deformability and electrochemical properties to achieve specific functions in response to various environmental stimuli. Stimulus-responsive hydrogels with electrochemical properties are good candidates for imitating such special functionalities in nature and thus have great potential in a wide range of academic and industrial applications. However, hydrogel-incorporated conductive materials are usually mechanically rigid, which limits their application in other fields. In addition, the fabrication technology of structured functional hydrogels has low reproducibility due to the required multistep processing. Here, inspired by nature, specifically the stimulus-responsive functionalities of plants, a new thermo-responsive multifunctional hybrid membrane (HM) is synthesized through the in situ hybridization of conductive poly(pyrrole) (PPy) on a photopolymerized poly(N-isopropylacrylamide) (PNIPAm) matrix. The morphological and electrical properties of the fabricated HM are investigated to characterize various aspects of its multiple functions. In terms of morphology, the HM can be easily fabricated into various structures by smartly utilizing photopolymerization patterning, and it exhibits thermo-responsive deformability. In terms of functionality, it exhibits various electrical and charge responses to thermal stimuli. This simple and efficient fabrication method can be used as a promising platform for fabricating a variety of functional devices.

    更新日期:2017-10-27
  • Cargo–carrier interactions significantly contribute to micellar conformation and biodistribution
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Adrian T Press, Anuradha Ramoji, Moritz vd Lühe, Alexandra C Rinkenauer, Jessica Hoff, Marianne Butans, Carsten Rössel, Christian Pietsch, Ute Neugebauer, Felix H Schacher, Michael Bauer

    Strategies to deliver drugs using nanocarriers, which are passively or actively targeted to their alleged site of action might favorably affect benefit–risk profiles of novel therapeutics. Here we tested the hypothesis whether the physico-chemical properties of the cargo as well as the actual conditions during encapsulation interfere during formulation of nanoparticular cargo–carrier systems. On the basis of previous work, a versatile class of nanocarriers is polyether-based ABC triblock terpolymer micelles with diameters below 50 nm. Their tunable chemistry and size allows to systematically vary important parameters. We demonstrate in vivo differences in pharmacokinetics and biodistribution not only dependent on micellar net charge but also on the properties of encapsulated (model) drugs and their localization within the micelles. On the basis of in vitro and in vivo evidence we propose that depending on drug cargo and encapsulation conditions micelles with homogeneous or heterogeneous corona structure are formed, contributing to an altered pharmacokinetic profile as differences in cargo location occur. Thus, these interactions have to be considered when a carrier system is selected to achieve optimal delivery to a given tissue.

    更新日期:2017-10-27
  • A skin-attachable, stretchable integrated system based on liquid GaInSn for wireless human motion monitoring with multi-site sensing capabilities
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Yu Ra Jeong, Jeonghyun Kim, Zhaoqian Xie, Yeguang Xue, Sang Min Won, Geumbee Lee, Sang Woo Jin, Soo Yeong Hong, Xue Feng, Yonggang Huang, John A Rogers, Jeong Sook Ha

    This paper introduces a liquid-metal integrated system that combines soft electronics materials and engineering designs with advanced near-field-communication (NFC) functionality for human motion sensing. All of the active components, that is, strain sensor, antenna and interconnections, in this device are made of liquid metal, and the device has unique gel-like characteristics and stretchability. Patterning procedures based on selective wetting properties of the reduced GaInSn enable a skin-attachable, miniaturized layout, in which the diameter of the device is less than 2 cm. Electromechanical characterization of the strain sensor and antenna reveals their behaviors under large uniaxial tensile and compressive strains, as well as more complex modes of deformation. Demonstrations of these devices involve their use in monitoring various human motions in a purely wireless fashion; examples include wrist flexion, movements of the vocal cord and finger motion. This simple platform has potential for use in human–machine interfaces for prosthetic control and other applications.

    更新日期:2017-10-27
  • A novel ultra-thin-walled ZnO microtube cavity supporting multiple optical modes for bluish-violet photoluminescence, low-threshold ultraviolet lasing and microfluidic photodegradation
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Qiang Wang, Yinzhou Yan, Feifei Qin, Chunxiang Xu, Xuelu Liu, Pingheng Tan, Nana Shi, Shuopeng Hu, Lin Li, Yong Zeng, Yan Zhao, Yijian Jiang

    ZnO optical microcavities have shown great promise as a potential core component material/structure for ultraviolet lasers, light-emitting diodes and photonic sensors because of their outstanding optoelectronic properties. Here, we report a novel ultra-thin-walled ZnO (UTW-ZnO) microtube cavity with a wall thickness of ~750 nm, supporting multiple types of optical modes, including in-tube Fabry–Perot modes, in-wall Fabry–Perot modes and wave-guided whispering gallery modes (WG-WGMs). The free-exciton recombination rate and exciton–exciton collisions are promoted in the cavity. The intensities of near-band edge (ultravoilet (UV) light) and X-band (blue light) emission are therefore increased at least one order of magnitude in the temperature range of 0–500 °C. Meanwhile, the temperature-sensitive multicolor luminescence of the UTW-ZnO microtubes in the visible band from near-white to bluish-violet is demonstrated for the first time. Low-threshold UV lasing is also achieved in the UTW-ZnO microtube by WG-WGMs, where the excitation threshold is down to 5.50 μW. Furthermore, light harvesting in the microtube cavity is beneficial to boosting the ZnO catalytic performance for photodegradation of organic dyes. The UTW-ZnO microtube exhibits compatibility to microfluidic channels for recyclable on-chip degradation. The present work provides new opportunities to design novel tubular wide-bandgap semiconductor devices for a variety of optoelectronic applications in micro/nanophotonics.

    更新日期:2017-10-27
  • Lipid nanoparticle-mediated efficient delivery of CRISPR/Cas9 for tumor therapy
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Lingmin Zhang, Peng Wang, Qiang Feng, Nuoxin Wang, Zitian Chen, Yanyi Huang, Wenfu Zheng, Xingyu Jiang

    The emerging CRISPR/Cas9 system represents a promising platform for genome editing. However, its low transfection efficiency is a major problem hampering the application of the gene-editing potential of CRISPR/Cas9. Herein, by screening a pool of more than 56 kinds of agents, we constructed a novel polyethylene glycol phospholipid-modified cationic lipid nanoparticle (PLNP)-based delivery system that can condense and encapsulate a Cas9/single-guide RNA (sgRNA) plasmid (DNA) to form a core–shell structure (PLNP/DNA) that mediated up to 47.4% successful transfection of Cas9/sgPLK-1 plasmids in A375 cells in vitro. An intratumor injection of Cas9/sgPLK-1 plasmids into melanoma tumor-bearing mice resulted in significant downregulation of Polo-like kinase 1 (PLK-1) protein and suppression of the tumor growth (>67%) in vivo. This approach provides a versatile method that could be used for delivering the CRISPR/Cas9 system with high efficiency and safety both in vitro and in vivo.

    更新日期:2017-10-27
  • Biomimetic hydrogel-CNT network induced enhancement of fluid-structure interactions for ultrasensitive nanosensors
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Meghali Bora, Ajay Giri Prakash Kottapalli, Jianmin Miao, Michael S Triantafyllou

    Flexible, self-powered, miniaturized, ultrasensitive flow sensors are in high demand for human motion detection, myoelectric prosthesis, biomedical robots, and health-monitoring devices. This paper reports a biomimetic nanoelectromechanical system (NEMS) flow sensor featuring a PVDF nanofiber sensing membrane with a hydrogel infused, vertically aligned carbon nanotube (VACNT) bundle that mechanically interacts with the flow. The hydrogel-VACNT structure mimics the cupula structure in biological flow sensors and gives the NEMS flow sensor ultrahigh sensitivity via a material-induced drag force enhancement mechanism. Through hydrodynamic experimental flow characterization, this work investigates the contributions of the mechanical and structural properties of the hydrogel in offering a sensing performance superior to that of conventional sensors. The ultrahigh sensitivity of the developed sensor enabled the detection of minute flows generated during human motion and micro-droplet propagation. The novel fabrication strategies and combination of materials used in the biomimetic NEMS sensor fabrication may guide the development of several wearable, flexible, and self-powered nanosensors in the future.

    更新日期:2017-10-27
  • Decorated ultrathin bismuth selenide nanosheets as targeted theranostic agents for in vivo imaging guided cancer radiation therapy
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Zhenhuan Song, Yanzhou Chang, Hanhan Xie, Xue-Feng Yu, Paul K Chu, Tianfeng Chen

    An efficient radiotherapeutic agent is synthesized using ultrathin two-dimensional 30-nm-wide and 2-nm-thick Bi2Se3 nanosheets (NSs) as a radiosensitizer. Chitosan (CS) and RGD peptide are employed to enhance the radiotherapy efficiency and biocompatibility. The Bi2Se3-CS-RGD NSs exhibit excellent targeting ability to αvβ3 integrin-overexpressing cancer cells and potent radiosensitization efficiency with high stability. Detailed in vitro experiments show that the Bi2Se3-CS-RGD NSs enhance the sensitivity of HeLa cells to X-ray-induced cell death by inhibiting TrxR activities and activating downstream reactive oxygen species-mediated signaling pathways. In vivo experiments using intravenous or intratumor injection demonstrate that the Bi2Se3-CS-RGD NSs are more efficient tumor growth inhibitors compared to bare Bi2Se3 NSs. The multifunctionality of the NSs enables the use of photoacoustic imaging and magnetic resonance imaging to examine their targeting ability and therapeutic effects, respectively. In addition, the RGD-decorated Bi2Se3 NSs show much better in vivo biocompatibility and can be efficiently expelled from the body after 48 h post injection. This study reveals an effective and safe theranostic agent for next-generation cancer radiotherapy.

    更新日期:2017-10-27
  • A highly flexible transparent conductive electrode based on nanomaterials
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Chang-Lae Kim, Chan-Won Jung, Young-Jei Oh, Dae-Eun Kim

    The electrical, optical, thermal, chemical, mechanical and tribological characteristics of a highly flexible transparent conductive electrode (HFTCE) coating based on reduced graphene oxide (rGO), carbon nanotubes (CNTs) and silver nanowires (AgNWs) were investigated under various conditions. The motivation was to develop a highly durable and flexible film for transparent conductive electrode applications. The overall characteristics of multilayers based on rGO, CNTs and AgNWs were found to be much better than those of the single-layer AgNW coating. The rGO and CNT layers served to protect the AgNW layer from damage due to bending and contact sliding motions. The contact pressure and bending stress were effectively distributed by the CNT layer deposited on top of the AgNW layer due to its spring-like behavior. In addition, the shear force from the friction force was reduced by the rGO top layer, which acted as a solid lubricant. Furthermore, the excellent performance of an HFTCE heater based on the rGO/CNT/AgNW coating was demonstrated by the results of a defrosting test.

    更新日期:2017-10-13
  • A semitransparent snake-like tactile and olfactory bionic sensor with reversibly stretchable properties
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Guofa Cai, Jiangxin Wang, Meng-Fang Lin, Jingwei Chen, Mengqi Cui, Kai Qian, Shaohui Li, Peng Cui, Pooi See Lee

    Many organisms and animals have sensing abilities that are different from those of human beings; for example, snakes have strong smell-, vibration-, touch- and heat-sensing abilities. A nature-mimicking sensing platform capable of sensing multiple stimuli, such as strain, pressure, temperature and other uncorrelated conditions, is highly desirable to broaden the applications of sensors. Here, we construct a semitransparent intelligent skin-like sensing platform based on polyaniline (PANI) nanowire arrays that can act as a bionic component by simultaneously sensing tactile stimuli and detecting colorless, odorless gas. Our multifunctional bionic sensing strategy is remarkably adaptive for versatile applications. The strain-sensing performance is superior to that of most conducting polymer-based sensors reported so far and is comparable to or even better than traditional metal and carbon nanowire/nanotube-based strain sensors. The highest gauge factor demonstrated is 149, making our system a remarkable candidate for strain-sensing applications. The sensor can accurately detect a wide range of human motions. We also demonstrate the simultaneous controlled olfaction ability for the detection of methane with high sensitivity and a fast response time. These results enable the realization of multifunctional and uncorrelated sensing capabilities, which will afford a wide range of applications to augment robotics, treatment, simulated skin, health monitoring and bionic systems.

    更新日期:2017-10-13
  • Electrochemical half-reaction-assisted sub-bandgap photon sensing in a graphene hybrid phsotodetector
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Ze Xiong, Jiawei Chen, Jizhuang Wang, Yu Cai, Xiang Liu, Zhicheng Su, Shijie Xu, Arshad Khan, Wendi Li, Juncao Bian, Gaomin Li, Mingyuan Huang, Jinyao Tang

    The photogating effect has been previously utilized to realize ultra-high photoresponsivity in a semiconductor-graphene hybrid photodetector. However, the spectral response of the graphene hybrid photodetector was limited by the bandgap of the incorporated semiconductor, which partially compromised the broadband absorption of graphene. Here, we show that this limitation can be overcome in principle by harnessing the electron-accepting ability of the electrochemical half-reaction. In our new graphene phototransistor, the electrochemical half-reaction serves as an effective reversible electron reservoir to accept the photoexcited hot electron from graphene, which promotes the sub-bandgap photosensitivity in a silver chloride (AgCl)-graphene photodetector. The photoconductive gain of ~ 3 × 109 electrons per photon in the AgCl-graphene hybrid is favored by the long lifetime of photoexcited carriers in the chemically reversible redox couple of AgCl/Ag0, enabling a significant visible light (400–600 nm) responsivity that is far beyond the band-edge absorption of AgCl. This work not only presents a new strategy to achieve an electrically tunable sub-bandgap photoresponse in semiconductor-graphene heterostructures but also provides opportunities for utilizing the electrochemical half reaction in other two-dimensional systems and optoelectronic devices.

    更新日期:2017-10-11
  • Novel biomaterial strategies for controlled growth factor delivery for biomedical applications
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-10-01
    Zhenming Wang, Zhefeng Wang, William Weijia Lu, Wanxin Zhen, Dazhi Yang, Songlin Peng

    Growth factors (GFs) are soluble proteins secreted by cells that have the ability to regulate a variety of cellular processes and tissue regeneration. However, their translation into clinical applications is limited due to their short effective half-life, low stability, and rapid inactivation by enzymes under physiological conditions. To maximize the effectiveness of GFs and their biologically relevant applicability, a wide variety of sophisticated bio-inspired systems have been developed that augment tissue repair and cellular regeneration by controlling how much, when, and where GFs are released. Recently, protein immobilization techniques combined with nanomaterial carriers have shown promise in mimicking the natural healing cascade during tissue regeneration by augmenting the delivery and effectiveness of GFs. This review evaluates the latest techniques in direct immobilization and relevant biomaterials used for GF loading and release, including synthetic polymers, albumin, polysaccharides, lipids, mesoporous silica-based nanoparticles (NPs), and polymeric capsules. Specifically, we focus on GF-encapsulated NPs in functionalized microporous scaffolds as a promising alternative with the ability to mimic extracellular matrix (ECM) hierarchical architectures and components with high cell affinity and bioactivity. Finally, we discuss how these next-generation, advanced delivery systems have been used to enhance tissue repair and regeneration and consider future implications for their use in the field of regenerative medicine.

    更新日期:2017-10-11
  • Rapid purification of sub-micrometer particles for enhanced drug release and microvesicles isolation
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-09-01
    Hui Min Tay, Sharad Kharel, Rinkoo Dalan, Zhijie Joshua Chen, Kah Kee Tan, Bernhard O Boehm, Say Chye Joachim Loo, Han Wei Hou

    Efficient separation of sub-micrometer synthetic or biological components is imperative in particle-based drug delivery systems and purification of extracellular vesicles for point-of-care diagnostics. Herein, we report a novel phenomenon in spiral inertial microfluidics, in which the particle transient innermost distance (Dinner) varies with size during Dean vortices-induced migration and can be utilized for small microparticle (MP) separation; aptly termed as high-resolution Dean flow fractionation (HiDFF). The developed technology was optimized using binary bead mixtures (1–3 μm) to achieve ~100- to 1000-fold enrichment of smaller particles. We demonstrated tunable size fractionation of polydispersed drug-loaded poly(lactic-co-glycolic acid) particles for enhanced drug release and anti-tumor effects. As a proof-of-concept for microvesicles studies, circulating extracellular vesicles/MPs were isolated directly from whole blood using HiDFF. Purified MPs exhibited well-preserved surface morphology with efficient isolation within minutes as compared with multi-step centrifugation. In a cohort of type 2 diabetes mellitus subjects, we observed strong associations of immune cell-derived MPs with cardiovascular risk factors including body mass index, carotid intima-media thickness and triglyceride levels (P<0.05). Overall, HiDFF represents a key technological progress toward high-throughput, single-step purification of engineered or cell-derived MPs with the potential for quantitative MP-based health profiling.

    更新日期:2017-09-30
  • Fluorine-functionalized metal–organic frameworks and porous coordination polymers
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-09-01
    Shin-ichiro Noro, Takayoshi Nakamura

    Fluorine, the element with the highest electronegativity and low electric polarizability, can produce a variety of characteristics, including specific adsorption sites for molecules as well as flexibility to the host materials. In this review, we will introduce fluorine-functionalized metal–organic frameworks/porous coordination polymers that show unique and unprecedented structures, structural transformations, and gas and vapor adsorption/separation properties derived from the fluorine characteristics.

    更新日期:2017-09-30
  • Rapid production of large-area, transparent and stretchable electrodes using metal nanofibers as wirelessly operated wearable heaters
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-09-01
    Jiuk Jang, Byung Gwan Hyun, Sangyoon Ji, Eunjin Cho, Byeong Wan An, Woon Hyung Cheong, Jang-Ung Park

    A rapidly growing interest in wearable electronics has led to the development of stretchable and transparent heating films that can replace the conventional brittle and opaque heaters. Herein, we describe the rapid production of large-area, stretchable and transparent electrodes using electrospun ultra-long metal nanofibers (mNFs) and demonstrate their potential use as wirelessly operated wearable heaters. These mNF networks provide excellent optoelectronic properties (sheet resistance of ~1.3 Ω per sq with an optical transmittance of ~90%) and mechanical reliability (90% stretchability). The optoelectronic properties can be controlled by adjusting the area fraction of the mNF networks, which also enables the modulation of the power consumption of the heater. For example, the low sheet resistance of the heater presents an outstanding power efficiency of 0.65 W cm−2 (with the temperature reaching 250 °C at a low DC voltage of 4.5 V), which is ~10 times better than the properties of conventional indium tin oxide-based heaters. Furthermore, we demonstrate the wireless fine control of the temperature of the heating film using Bluetooth smart devices, which suggests substantial promise for the application of this heating film in next-generation wearable electronics.

    更新日期:2017-09-08
  • Non-dissipative internal optical filtering with solution-grown perovskite single crystals for full-colour imaging
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-09-01
    Sergii Yakunin, Yevhen Shynkarenko, Dmitry N Dirin, Ihor Cherniukh, Maksym V Kovalenko

    Herein we demonstrate that solution-grown single crystals of semiconducting methylammonium lead halide perovskites (MAPbX3, where MA=CH3NH3+, X=Cl−, Br− and Br/I−) can be used as semiconductor absorbers for full-colour imaging. A one-pixel photodetector prototype was constructed by stacking three layers of blue-, green- and red-sensitive MAPbCl3, MAPbBr3 and MAPb(Br/I)3 crystals, respectively. The prototype detector was demonstrated to recognize and faithfully reproduce coloured images by recombination of the signals from each individual colour channel. This layered structure concept, besides imparting a two- to three-fold reduction in the number of required pixels, also offers several other advantages over conventional technologies: three times more efficient light utilization (and thus higher sensitivity) than common Bayer scheme devices based on dissipative optical filters, colour moiré suppression and no need for de-mosaic image processing. In addition, the direct band gap structure of perovskites results in optical absorption that is several orders of magnitude greater than silicon. This opens a promising avenue towards the reduction of pixel-size in next-generation devices as compared with conventional silicon-based technologies.

    更新日期:2017-09-04
  • Exploration and characterization of the memcapacitor and memristor properties of Ni–DNA nanowire devices
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-09-01
    Hsueh-Liang Chu, Jian-Jhong Lai, Li-Ying Wu, Shen-Lin Chang, Chia-Ming Liu, Wen-Bin Jian, Yu-Chang Chen, Chiun-Jye Yuan, Tai-Sing Wu, Yun-Liang Soo, Massimiliano Di Ventra, Chia-Ching Chang

    A 2-μm-long Ni ion-chelated DNA molecule (Ni–DNA) was found for the first time to possess both memcapacitor and memristor properties; this Ni–DNA molecule is known as a dual memory circuit element (memelement). As a memelement, the state of impedance on Ni–DNA is proportional to the unit number of Ni ions containing a base pair complex (Ni–bp), which is determined by the previously applied external voltage. Interestingly, the impedances of Ni–DNA change in response to a change in the sweeping frequencies of the external bias. Our simulation results also indicate that changes in the effective resistance and capacitance of Ni–bp may be attributed to changes in the Ni ion redox species in the Ni–bp of a Ni–DNA nanowire. Therefore, the working mechanism of a nanowire-type memcapacitor and memristor is revealed. In summary, the Ni–DNA nanowire is shown to be a multi-dimensional memory device, whose memory state depends on the length of DNA and applied external voltages/frequencies.

    更新日期:2017-09-04
  • Optically and spatially templated polymer architectures formed by photopolymerization of reactive mesogens in periodically deformed liquid crystals
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Vijay Kumar Baliyan, Seung Hee Lee, Shin-Woong Kang

    A unique and versatile method for forming optically (that is, orientationally) and spatially patterned polymer architectures was developed based on the photopolymerization of reactive mesogens (RMs) in a periodically deformed liquid crystal (LC). Without using lithographic or holographic implements, various polymer patterns were produced by employing nematic LCs as reaction solvents and spatially nonuniform electric fields. The nematic mixture, containing 5.0 wt.% RMs and sandwiched between patterned electrodes, was exposed to spatially uniform reaction-initiating radiation. The spatially nonuniform electric field induced periodic optical patterns in the reaction template with spatially varying elastic deformations. The resulting polymerized RM networks were both spatially and optically patterned, with good fidelity with respect to the electrode pattern and subsequent periodic director profiles. The spatial distribution of dense RM networks coincided precisely with the profile of highly deformed regions in the reaction medium. The optical birefringence of the polymer network was templated by the local director of the reaction template. Numerical calculations of director configuration and the associated elastic energy of the reaction template precisely matched the spatial and orientational order of polymerized RM networks. The proposed method provides ease and flexibility in forming organized polymer architectures for functional materials that require both positional and orientational order for their applications.

    更新日期:2017-08-25
  • Hyperbolic spoof plasmonic metasurfaces
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Yihao Yang, Liqiao Jing, Lian Shen, Zuojia Wang, Bin Zheng, Huaping Wang, Erping Li, Nian-Hai Shen, Thomas Koschny, Costas M Soukoulis, Hongsheng Chen

    Hyperbolic metasurfaces have recently emerged as a new research frontier because of the unprecedented capabilities to manipulate surface plasmon polaritons (SPPs) and many potential applications. However, thus far, the existence of hyperbolic metasurfaces has neither been observed nor predicted at low frequencies because noble metals cannot support SPPs at longer wavelengths. Here, we propose and experimentally demonstrate spoof plasmonic metasurfaces with a hyperbolic dispersion, where the spoof SPPs propagate on complementary H-shaped, perfectly conducting surfaces at low frequencies. Thus, non-divergent diffractions, negative refraction and dispersion-dependent spin-momentum locking are observed as the spoof SPPs travel over the hyperbolic spoof plasmonic metasurfaces (HSPMs). The HSPMs provide fundamental new platforms to explore the propagation and spin of spoof SPPs. They show great capabilities for designing advanced surface wave devices such as spatial multiplexers, focusing and imaging devices, planar hyperlenses, and dispersion-dependent directional couplers, at both microwave and terahertz frequencies.

    更新日期:2017-08-25
  • Graphene membranes for water desalination
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Shahin Homaeigohar, Mady Elbahri

    Extensive environmental pollution caused by worldwide industrialization and population growth has led to a water shortage. This problem lowers the quality of human life and wastes a large amount of money worldwide each year due to the related consequences. One main solution for this challenge is water purification. State-of-the-art water purification necessitates the implementation of novel materials and technologies that are cost and energy efficient. In this regard, graphene nanomaterials, with their unique physicochemical properties, are an optimum choice. These materials offer extraordinarily high surface area, mechanical durability, atomic thickness, nanosized pores and reactivity toward polar and non-polar water pollutants. These characteristics impart high selectivity and water permeability, and thus provide excellent water purification efficiency. This review introduces the potential of graphene membranes for water desalination. Although literature reviews have mostly concerned graphene’s capability for the adsorption and photocatalysis of water pollutants, updated knowledge related to its sieving properties is quite limited.

    更新日期:2017-08-25
  • Texturing degree boosts thermoelectric performance of silver-doped polycrystalline SnSe
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Xue Wang, Jingtao Xu, Guo-Qiang Liu, Xiaojian Tan, Debo Li, Hezhu Shao, Tianya Tan, Jun Jiang

    Tin selenite (SnSe) has attracted significant attention due to its record thermoelectric figure of merit (ZT=2.6 at 923 K) of its single crystal. However, the polycrystalline SnSe processes considerably less ZTs (1.1). In this study, we investigate the thermoelectric properties of Ag-doped polycrystalline SnSe, which was synthesized via zone melting and hot pressing. By comparing our results and previous reports of Ag-doped single crystals and polycrystals, we determine that the high texturing degree is essential for achieving good thermoelectric performance in polycrystalline SnSe. The zone-melted Sn0.99Ag0.02Se shows better thermoelectric performance than the Ag-doped SnSe single crystal in the entire temperature range, exhibiting a peak ZT of 1.3 at 793 K.

    更新日期:2017-08-25
  • Plasmonics of topological insulators at optical frequencies
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Jun Yin, Harish NS Krishnamoorthy, Giorgio Adamo, Alexander M Dubrovkin, Yidong Chong, Nikolay I Zheludev, Cesare Soci

    The development of nanoplasmonic devices, such as plasmonic circuits and metamaterial superlenses in the visible to ultraviolet frequency range, is hampered by the lack of low-loss plasmonic media. Recently, strong plasmonic response was reported in a certain class of topological insulators. Here, we present a first-principles density functional theory analysis of the dielectric functions of topologically insulating quaternary (Bi,Sb)2(Te,Se)3 trichalcogenide compounds. Bulk plasmonic properties, dominated by interband transitions, are observed from 2 to 3 eV and extend to higher frequencies. Moreover, trichalcogenide compounds are better plasmonic media than gold and silver at blue and UV wavelengths. By analyzing thin slabs, we also show that these materials exhibit topologically protected surface states, which are capable of supporting propagating plasmon polariton modes over an extremely broad spectral range, from the visible to the mid-infrared and beyond, owing to a combination of inter- and intra-surface band transitions.

    更新日期:2017-08-25
  • Quantum-well-induced engineering of magnetocrystalline anisotropy in ferromagnetic films
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Ching-Hao Chang, Kun-Peng Dou, Guang-Yu Guo, Chao-Cheng Kaun

    Tuning quantum well states (QWSs) to govern physical properties in nanoscale leads to the development of advanced electronic devices. Here, we propose that QWSs can be engineered to control magnetocrystalline anisotropy energy (MCAE) which dominates the magnetization orientation (that is, the easy axis) of a ferromagnetic thin film. We investigate from first-principles the MCAE of the bcc Fe film on an Ag substrate. The calculated MCAE oscillates largely as Fe thickness increases agreeing well with experiments, and reaches oscillation extremes as the Fe d-orbital QWSs approach the Fermi level (EF). Crucially, we find that this phenomenon stems from the combined effect of intrinsic spin-orbit interaction (SOI) and Rashba SOI field on the Fe QWSs, which modulates the density of states at EF as the Fe thickness varies. Moreover, this effect offers a way to tune not only the strength of magnetic anisotropy but also the easy axis of a Fe film by shifting EF within ten meV via moderately charge injection, which could realize advanced memory devices with ultra-low power consumption.

    更新日期:2017-08-25
  • Methemoglobin as a redox-responsive nanocarrier to trigger the in situ anticancer ability of artemisinin
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Huan Li, Yangjun Chen, Tingting Chen, Haijie Han, Hongxin Tong, Qiao Jin, Jian Ji

    Learning from the antimalarial mechanism of artemisinin (ART) in nature, we explored methemoglobin (MHb) as a smart nanocarrier of ART, in which anticancer abilities can be turned on in situ through the upregulated reducing capacity of tumor tissue. Ultra violet–visible, electron paramagnetic resonance spectrometry and in vitro cell assessment proved that a reducing agent such as glutathione can work as an excellent biogenic trigger to reduce ferric iron in MHb to the ferrous state, activating the ability of ART to generate free radicals and resulting in cytotoxicity and apoptosis. In vivo investigations showed that the MHb–ART complex had encouraging anticancer outcomes. The bioinspired nanocarrier may pave a new way to achieve targeted toxicity to cancer cells with extremely low side effects.

    更新日期:2017-08-25
  • Nano-bio interactions between carbon nanomaterials and blood plasma proteins: why oxygen functionality matters
    NPG Asia Mater. (IF 9.157) Pub Date : 
    Kenry, Alisha Geldert, Yanpeng Liu, Kian Ping Loh, Chwee Teck Lim

    Nano-bio interactions between carbon nanomaterials and blood plasma proteins: why oxygen functionality matters NPG Asia Materials 9, e422 (August 2017). doi:10.1038/am.2017.129 Authors: Kenry , Alisha Geldert, Yanpeng Liu, Kian Ping Loh & Chwee Teck Lim

    更新日期:2017-08-18
  • Dual-electrochromic bipolar electrode-based universal platform for the construction of various visual advanced logic devices
    NPG Asia Mater. (IF 9.157) Pub Date : 
    Qingfeng Zhai, Daoqing Fan, Xiaowei Zhang, Jing Li, Erkang Wang

    Dual-electrochromic bipolar electrode-based universal platform for the construction of various visual advanced logic devices NPG Asia Materials 9, e421 (August 2017). doi:10.1038/am.2017.132 Authors: Qingfeng Zhai, Daoqing Fan, Xiaowei Zhang, Jing Li & Erkang Wang

    更新日期:2017-08-18
  • Intrinsic self-healing polymers with a high E-modulus based on dynamic reversible urea bonds
    NPG Asia Mater. (IF 9.157) Pub Date : 
    Stefan Zechel, Robert Geitner, Marcus Abend, Michael Siegmann, Marcel Enke, Natascha Kuhl, Moritz Klein, Jürgen Vitz, Stefanie Gräfe, Benjamin Dietzek, Michael Schmitt, Jürgen Popp, Ulrich S Schubert, Martin D Hager

    Intrinsic self-healing polymers with a high E-modulus based on dynamic reversible urea bonds NPG Asia Materials 9, e420 (August 2017). doi:10.1038/am.2017.125 Authors: Stefan Zechel, Robert Geitner, Marcus Abend, Michael Siegmann, Marcel Enke, Natascha Kuhl, Moritz Klein, Jürgen Vitz, Stefanie Gräfe, Benjamin Dietzek, Michael Schmitt, Jürgen Popp, Ulrich S Schubert & Martin D Hager

    更新日期:2017-08-18
  • Direct growth of FeCo2O4 nanowire arrays on flexible stainless steel mesh for high-performance asymmetric supercapacitor
    NPG Asia Mater. (IF 9.157) Pub Date : 
    Nilesh R Chodankar, Deepak P Dubal, Yongchai Kwon, Do-Heyoung Kim

    Direct growth of FeCo2O4 nanowire arrays on flexible stainless steel mesh for high-performance asymmetric supercapacitor NPG Asia Materials 9, e419 (August 2017). doi:10.1038/am.2017.145 Authors: Nilesh R Chodankar, Deepak P Dubal, Yongchai Kwon & Do-Heyoung Kim

    更新日期:2017-08-18
  • Enhanced photoresponsivity of the MoS2-GaN heterojunction diode via the piezo-phototronic effect
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Fei Xue, Leijing Yang, Mengxiao Chen, Jian Chen, Xiaonian Yang, Longfei Wang, Libo Chen, Caofeng Pan, Zhong Lin Wang

    Combining layered MoS2 flakes with conventional 3D semiconductors is a feasible route to fabricate high-quality heterojunction devices by harnessing the advantages of both materials. Here, we present a pressure-modulated heterojunction photodiode that is composed of an n-type multilayer MoS2 and a p-type GaN film via the piezo-phototronic effect. Under the illumination of 365 nm incident light, a strong photoresponse is observed with response and recovery times of ~66 and 74 ms, respectively. Under a pressure of 258 MPa, the photoresponsivity of this photodiode can be tuned by the piezo-phototronic effect arising from the GaN film to ~3.5 times. Because of the lowered junction barrier with an applied external pressure (strain), more photogenerated carriers can successfully pass through the junction area without recombination, which results in an enhancement effect. This work provides a possible path for the implementation of high-performance electronic and optoelectronic devices that are based on hybrid heterostructures via human interfacing.

    更新日期:2017-08-04
  • Hygromorphic actuator from a metal oxide film driven by a nano-capillary forest structure
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Hosung Kang, Minki Lee, Hyuneui Lim, Howard A Stone, Jinkee Lee

    We have developed a hygromorphic metal oxide actuator using an electrochemical method to produce a superhydrophilic free-standing nano-capillary forest of titanium oxide with a high aspect ratio (~80). This metal oxide film has an inhomogeneous initial gap at the top and bottom surfaces between the tubes due to flexure during fabrication. The actuation mechanism is as follows. First, when a drop of water is applied on the surface of a titanium oxide nano-capillary forest (TNF), the water penetrates through the film instantaneously, and the titanium oxide nano-capillaries are pulled together by interplay of the capillary force and van der Waals force. When water has fully filled in the gaps between the capillaries, the free-standing TNF film remains unbent for ~2 min. Then, as the water evaporates, the film bends further in the forward direction. When the water has completely evaporated, the van der Waals force alone acts on the capillaries, and the TNF film returns to its initial state. This TNF possesses great stability and repeatability for long-term usage having a high bending energy density of ~1250 kJ m–3 and unique capabilities. It may lead to novel stimuli-responsive systems, including energy collection and storage, as well as robotics applications.

    更新日期:2017-08-04
  • Easy on-demand self-assembly of lateral nanodimensional hybrid graphene oxide flakes for near-infrared-induced chemothermal therapy
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Raj Kumar Thapa, Jeong Hoon Byeon, Sae Kwang Ku, Chul Soon Yong, Jong Oh Kim

    Near-infrared (NIR)-induced chemothermal doxorubicin (DOX) release for anticancer activity was demonstrated using DOX-incorporated fully lateral nanodimensional graphene oxide (nGO) flakes layered with chitosan-polyethylene glycol (PEG) conjugate (nGO@DOX-cPEG) from a single-pass gas-phase self-assembly. Unlike most previously reported graphene oxide-based drug carriers, the proposed processing method introduced a fully nanoscale (both in lateral dimension and thickness) configuration without multistep wet physicochemical processes that enhance the drug-loading capacity and NIR-induced heat generation resulting from the increased surface area. The accumulation of nGO@DOX-cPEG flakes in prostate cancer cells enhanced apoptotic phenomena via the combined effects of DOX release and heat generation upon NIR irradiation. The combined anticancer effects were verified through in vivo assessment with better safety profiles than free DOX. The proposed strategy warrants continuous assembly of multimodal nanocarriers for the efficient treatment of prostate cancers and may be a promising candidate for advanced drug delivery systems.

    更新日期:2017-08-04
  • Reducing the contact time using macro anisotropic superhydrophobic surfaces — effect of parallel wire spacing on the drop impact
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-08-01
    Meirong Song, Zhaohui Liu, Yongjian Ma, Zhichao Dong, Yilin Wang, Lei Jiang

    Surfaces designed to reduce the contact time of impacting droplets are potentially of great importance for fundamental science and technological applications, for example, anti-icing, self-cleaning and heating transfer applications. Previous studies have shown that the contact time can be reduced via introducing one or several crossing macroscale wires on superhydrophobic surfaces (SHSs). However, the impacts that strike far from the wires (off-center impacts) have contact times that are equal to those obtained on SHSs. Here we demonstrate that this problem can be largely solved by using macro anisotropic SHSs (macro-aniso-SHSs)—in which the wires are parallel and macroscaled. The droplet contact time depends on the spacing between the macrostripes and is remarkably reduced by 40–50% when the spacing is comparable to the droplet size. Obvious differences in the contact time are not observed for impacts that are centered on the stripe and in the groove. The impacts centered in the groove produce new hydrodynamics that are characterized by extended spreading, easy break up and bouncing in a flying-eagle configuration. The study discusses the underlying mechanisms of the impact processes. Moreover, the effect of parallel wires on the contact time is discussed by comparing the droplet impact data for grooved rice leaves and non-grooved cabbage leaves. The enhanced drop mobility associated with the macro-aniso-SHSs should be very useful in many industrial applications.

    更新日期:2017-08-04
  • Kinetically controlled formation of uniform FePO4 shells and their potential for use in high-performance sodium ion batteries
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Shu-Yi Duan, Jun-Yu Piao, Tian-Qi Zhang, Yong-Gang Sun, Xiao-Chan Liu, An-Min Cao, Li-Jun Wan

    Amorphous iron phosphates are potential cathode materials for sodium ion batteries. The amorphous FePO4 matrix is able to insert/extract sodium ions reversibly without apparent structural degradation, resulting in stable performance during the charge/discharge process. However, the extremely low electronic conductivity of FePO4 itself becomes a formidable obstacle for its application as a high-performance cathode material. Here, by tuning the growth kinetics of FePO4 in an aqueous solution, we were able to control its formation onto a large variety of substrates, forming uniform core-shell structures. Specifically, the use of multiwalled carbon nanotubes as the core material together with the growth control of FePO4 produced the core-shell structure of MWCNTs@FePO4 with a delicately controlled shell thicknesses. We confirmed that such a nanocomposite can act as an effective cathode material by taking advantage of both the highly conductive core and the electrochemically active shell, leading to improved battery performance as revealed by the high discharge capacity and the greatly improved rate capability. We anticipate that our progress in FePO4 control offers new potential in different research fields, such as materials chemistry, catalysis and energy storage devices.

    更新日期:2017-07-30
  • Organic electronic synapses with pinched hystereses based on graphene quantum-dot nanocomposites
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Hwan Young Choi, Chaoxing Wu, Chang Han Bok, Tae Whan Kim

    Organic electronic synapses (e-synapses) based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/graphene quantum dot (GQD) nanocomposites are fabricated by using a solution method. Current–voltage (I–V) curves for the devices under dual positive bias voltage sweeps show that the conductance with a pinched hysteresis gradually increased with increasing applied voltage, and those for the devices under dual negative bias voltage sweeps gradually decreased with increasing applied voltage, indicative of the fingerprint of e-synapses. The current in the devices decreases with increasing concentration of GQDs in the active layer, and the devices fabricated utilizing the ratio of PEDOT:PSS to GQDs of 1:0.4 shows the best performance among the e-synapses. The carrier transport and operating mechanisms of the e-synapses are described on the basis of both the I–V results and the trapping and escape of electrons from the GQDs.

    更新日期:2017-07-30
  • Colloidal templating of highly ordered gelatin methacryloyl-based hydrogel platforms for three-dimensional tissue analogues
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Bae Hoon Lee, Hitomi Shirahama, Myung Hee Kim, Jae Ho Lee, Nam-Joon Cho, Lay Poh Tan

    Three-dimensional, protein-based hydrogel scaffolds that successfully mimic in vivo extracellular matrix microenvironments are desirable for tissue engineering and regenerative medicine applications, and can provide highly capable in vitro tissue analogues. However, the fabrication of protein-based scaffolds with uniform porosity, thin walls and durable mechanical properties remains a challenging prospect that might be overcome by integrating advances in microfabrication and protein functionalization. Towards this goal, herein, we report the successful fabrication of a highly ordered, gelatin-based inverted colloidal crystal (ICC) hydrogel platform that is robust and supports high levels of cell function. In particular, the utilization of colloidal templating microfabrication strategies together with highly substituted, photocrosslinkable gelatin methacryloyl (GelMA) allowed us to fabricate protein-based three-dimensional scaffolds with uniform pore interconnectivity, structural stability and tailorable degradation properties. The resulting GelMA ICC scaffolds provided cell attachment sites and promoted intercellular interaction of hepatocytes, which resulted in improved cell function compared to a flat 2D system. The results demonstrate the potential of GelMA ICC scaffolds to become an effective tissue engineering platform for drug screening and regenerative medicine.

    更新日期:2017-07-30
  • Universal high work function flexible anode for simplified ITO-free organic and perovskite light-emitting diodes with ultra-high efficiency
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Su-Hun Jeong, Seong-Hoon Woo, Tae-Hee Han, Min-Ho Park, Himchan Cho, Young-Hoon Kim, Hyunsu Cho, Hobeom Kim, Seunghyup Yoo, Tae-Woo Lee

    Flexible transparent electrode materials such as conducting polymers, silver nanowires, carbon nanotubes and graphenes are being investigated as possible replacements for conventional brittle inorganic electrodes. However, they have critical drawbacks of low work function (WF), resulting in a high hole injection barrier to an overlying semiconducting layer in simplified organic or organic–inorganic hybrid perovskite light-emitting diodes (OLEDs or PeLEDs). Here, we report a new anode material (AnoHIL) that has multifunction of both an anode and a hole injection layer (HIL) as a single layer. The AnoHIL has easy WF tunability up to 5.8 eV and thus makes ohmic contact without any HIL. We applied our anodes to simplified OLEDs, resulting in very high efficiency (62% ph el−1 for single and 88% ph el−1 for tandem). The AnoHIL showed a similar tendency in simplified PeLEDs, implying universal applicability to various optoelectronics. We also demonstrated large-area flexible lightings using our anodes. Our results provide a significant step toward the next generation of high-performance simplified indium tin oxide (ITO)-free light-emitting diodes.

    更新日期:2017-07-30
  • Transferable single-crystal GaN thin films grown on chemical vapor-deposited hexagonal BN sheets
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Kunook Chung, Hongseok Oh, Janghyun Jo, Keundong Lee, Miyoung Kim, Gyu-Chul Yi

    Single-crystal gallium nitride (GaN) layers were directly grown on centimeter-scale hexagonal boron nitride (h-BN). Using chemical vapor deposition (CVD), centimeter-scale h-BN films were synthesized on a single-crystal Ni(111) and readily transferred onto amorphous fused silica supporting substrates that had no epitaxial relationship with GaN. For growing fully coalescent GaN layers on h-BN, the achievement of high-density crystal growths was a critical growth step because the sp2-bonded h-BN layers are known to be free of dangling bonds. Unlike GaN layers grown on a typical heterogeneous sapphire substrate, the morphological and microstructural results strongly suggest a high-density growth feature that is driven by the atomic cliffs inherent in the CVD-grown h-BN layers. More importantly, the GaN layers grown on CVD-grown h-BN exhibited a flat and continuous surface morphology with well-aligned crystal orientations both along the c-axis and in-plane, indicating the characteristics of GaN heteroepitaxy on h-BN.

    更新日期:2017-07-30
  • Homogeneous dewetting on large-scale microdroplet arrays for solution-processed electronics
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Xuying Liu, Chuan Liu, Kenji Sakamoto, Takeshi Yasuda, Pan Xiong, Lijuan Liang, Tengzhou Yang, Masayuki Kanehara, Jun Takeya, Takeo Minari

    Unidirectional dewetting enables the production of large-area thin films with high efficiency at low cost. Herein, we report homogeneous unidirectional dewetting on large-area microdroplet arrays via gravity-induced deformation in droplets combined with alternating lyophilic/lyophobic patterns. This process allows the scaled-up deposition of thin films, including organic semiconductors and transition metal oxides, through the autogenous shrinkage of droplets, which further enables the fabrication of large-area organic thin-film transistor (OTFT) arrays. The resulting field-effect mobility and on/off ratio of the fully printed OTFTs exceeded 13 cm2 V−1 s−1 and 108, respectively. Therefore, the presented dewetting method is promising to realize the roll-to-roll manufacture of large-area flexible electronics.

    更新日期:2017-07-30
  • In vivo targeted therapy of gastric tumors via the mechanical rotation of a flower-like Fe3O4@Au nanoprobe under an alternating magnetic field
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Ting Yin, Haigang Wu, Qian Zhang, Guo Gao, Joseph G Shapter, Yulan Shen, Qiaozhi He, Peng Huang, Wen Qi, Chunlei Zhang, Yuming Yang, Daxiang Cui

    Owing to their hypotoxicity, great spatial resolution and tomographic properties, Fe3O4 nanoparticles (NPs) are becoming one of the most promising materials for noninvasive biological imaging and shape-dependent therapeutic agents for malignant tumor therapy. Conventional spherical NPs are unable to effectively destroy cellular structure in therapy and thus result in tumors with a high risk of drug resistance. Herein we developed a novel flower-like targeting Fe3O4@Au-HPG-Glc nanoprobe (thiol-containing hyperbranched polyglycerol (HPG); 4-aminophenyl β-D-glucopyranoside (Glc)) that can enhance magnetic resonance imaging (MRI) for cancer therapy. With the guidance of a targeting molecule, Fe3O4@Au-HPG-Glc nanoprobes can precisely target tumor cells. Under an alternating magnetic field (AMF), the flower-like Fe3O4@Au-HPG-Glc nanoprobes can rotate along the central axis of the core to substantially destroy tumor cells by damaging the nucleus or cell membrane. Our results showed that this shape-dependent therapeutic agent-based strategy had remarkable efficacy for MRI-guided tumor therapy. Furthermore, the inhibition of tumor growth in tumor-bearing mice was up to approximately 47.3% on the twelfth day of treatment compared with the level of inhibition in a blank group. Different from other reported methods for cancer therapy, our proposed AMF-dependent targeted cancer therapy is a novel strategy that can potentially reduce drug resistance in gastric tumors.

    更新日期:2017-07-14
  • Bimetallic AuRh nanodendrites consisting of Au icosahedron cores and atomically ultrathin Rh nanoplate shells: synthesis and light-enhanced catalytic activity
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Yongqiang Kang, Qi Xue, Ruili Peng, Pujun Jin, Jinghui Zeng, Jiaxing Jiang, Yu Chen

    Precise control of the morphology, composition and structure of metal nanostructures not only effectively improves their catalytic activity and durability but also enhances their range of applications. In this work, bimetallic Au@Rh core–shell nanodendrites are synthesized by a facile one-pot hydrothermal method. Physical characterizations show that the dendritic Rh consists of two-dimensional (2D) ultrathin Rh nanoplates with a thickness of approximately 1.2 nm. For the first time, Au@Rh core–shell nanostructures are used as a catalyst for the hydrogen generation reaction from aqueous hydrazine solution (N2H4=N2+2H2, HGR-N2H4). Bimetallic Au@Rh core–shell nanodendrites exhibit improved catalytic activity and durability for the HGR-N2H4 compared with commercial Rh nanocrystals, which can be attributed to the atomically ultrathin structure of 2D Rh nanoplates and the interconnected structure of nanodendrites, respectively. Under light irradiation, bimetallic Au@Rh core–shell nanodendrites show light-enhanced catalytic activity for the HGR-N2H4, originating from the distinctive localized surface plasmon resonance of Au icosahedron cores.

    更新日期:2017-07-14
  • Route to achieving perfect B-site ordering in double perovskite thin films
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Josée E Kleibeuker, Eun-Mi Choi, Edward D Jones, Tse-Min Yu, Bianca Sala, Belinda A MacLaren, Demie Kepaptsoglou, David Hernandez-Maldonado, Quentin M Ramasse, Lewys Jones, Juri Barthel, Ian MacLaren, Judith L MacManus-Driscoll

    Double perovskites (DP, A2BB’O6) exhibit a breadth of multifunctional properties with a huge potential range of applications, including magneto-optic and spintronic devices. However, spontaneous cation ordering is limited by the similar size and charge of B and B’ cations. We introduce a route to stimulate B-site rock-salt ordering. By growing thin films on (111)-oriented substrates, ‘in-plane’ strain acts on the intrinsically tilted oxygen octahedra of the DP and produces two different B-site cages (in size and shape), stimulating spontaneous cation ordering. For the ferromagnetic insulator La2CoMnO6, clear Co/Mn ordering was achieved by growing on (111)-oriented substrates. The difference in B-site cages was further enhanced when grown under minor (111) in-plane compressive strain, resulting in long-range ordering with a saturation magnetization of 5.8 μB/formula unit (f.u.), close to the theoretical 6 μB/f.u., without antiferromagnetic behavior. Our approach enables the study of many new ordered DPs which have never been made before.

    更新日期:2017-07-14
  • Micron-thick highly conductive PEDOT films synthesized via self-inhibited polymerization: roles of anions
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Wei Shi, Qin Yao, Sanyin Qu, Hongyi Chen, Tiansong Zhang, Lidong Chen

    The inhibitor-dependent poly(3,4-ethylenedioxythiophene) (PEDOT) fabrication suffers major problems in the areas of controllability and film thickness. In this work, we found that anions play a key role in both the polymerization and the structure of PEDOT. As a precursor, anions greatly influence the reaction rate and oxidant solubility. In its role as a counter-ion, the anions also affect chain conductance and crystal growth. With these behaviors in mind, a self-inhibited polymerization approach using novel oxidants with appropriate anions was successfully developed to facilitate the fabrication of high quality in situ polymerized PEDOT films and solve the thickness limitation problem. Inhibitor-free heavy oxidative solutions with weakly basic anions enable the spin-coating of thick and homogeneous oxidant layers and also effectively inhibit both the crystallization of the oxidant and H+ formation throughout the polymerization process. PEDOT: dodecylbenzenesulfonate (PEDOT:DBSA) exhibits the highest performance among all candidates due to its appropriate anion basicity and low steric effect. An extremely high doping level of 42.9% is achieved, and an electrical conductivity of ~1100 S cm−1 is successfully maintained for film thicknesses between 310 nm and 1.79 μm. In addition, the thermoelectric power factor (RT) for pristine films was improved to 77.2 μW mK−2 from 69.6 μW mK−2 by the dedoping treatment. This study provides a new approach for fabricating high performance PEDOT thick films using anion-based design.

    更新日期:2017-07-14
  • On the speed of piezostrain-mediated voltage-driven perpendicular magnetization reversal: a computational elastodynamics-micromagnetic phase-field study
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Ren-Ci Peng, Jia-Mian Hu, Long-Qing Chen, Ce-Wen Nan

    By linking the dynamics of local piezostrain to the dynamics of local magnetization, we computationally analyzed the speed of a recently proposed scheme of piezostrain-mediated perpendicular magnetization reversal driven by a voltage pulse in magnetoelectric heterostructures. We used a model heterostructure consisting of an elliptical ultrathin amorphous Co20Fe60B20 on top of a polycrystalline Pb(Zr,Ti)O3 (PZT) thin film. We constructed a diagram showing the speed of perpendicular magnetization reversal as a function of the amplitude of the applied voltage pulse and the stiffness damping coefficient of PZT film. In addition, we investigated the influence of thermal fluctuations on the switching speed. The analyses suggest that the switching time remains well below 10 ns and that the energy dissipation per switching is on the order of femtojoule. The present computational analyses can be generally used to predict the speed of piezostrain-enabled magnetization switching and magnetic domain-wall motion, which critically determines the response time of corresponding piezostrain-enabled spintronic and magnonic devices.

    更新日期:2017-07-08
  • Platinum loaded on dual-doped TiO2 as an active and durable oxygen reduction reaction catalyst
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Bing-Jen Hsieh, Meng-Che Tsai, Chun-Jern Pan, Wei-Nien Su, John Rick, Jyh-Fu Lee, Yaw-Wen Yang, Bing-Joe Hwang

    In this work, dual-doped TiO2 was successfully synthesized by using tungsten or niobium as the cation and nitrogen as the anion and, as compared with single-doped TiO2, provided a higher electron conductivity and improved physical properties. Platinum (Pt) nanoparticles loaded on these materials showed better electrochemical performance, and the Pt/Ti0.9Nb0.1NxOy and Pt/Ti0.8W0.2NxOy catalysts were 2.6–3.7 times more active than the Pt/Ti0.9Nb0.1Oy and Pt/Ti0.8W0.2Oy catalysts without nitrogen doping. Additionally, there was an activity loss of 22.9% as compared with 81% in Pt/C after 30 000 cyclic voltammetry cycles, a value exceeding the US Department of Energy (DOE) stability target. Dual doping not only enhances the electron conductivity but also changes the electronic state of Pt on the support materials, thus allowing for more active and stable catalysts. Both X-ray absorption spectroscopy (XAS) and density functional theory (DFT) studies were undertaken to demonstrate how defect formation affects the interactions between Pt and the single- or dual-doped TiO2 supports and manipulates the physical and chemical properties of the resulting catalysts. Thus, these catalytic supports are strong candidates for proton exchange membrane fuel cell applications.

    更新日期:2017-07-08
  • Van der Waals epitaxy between the highly lattice mismatched Cu-doped FeSe and Bi2Te3
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Arsham Ghasemi, Demie Kepaptsoglou, Pedro L Galindo, Quentin M Ramasse, Thorsten Hesjedal, Vlado K Lazarov

    We present a structural and density functional theory study of FexCu1−xSe within the three-dimensional topological insulator Bi2Te3. The FexCu1−xSe inclusions are single-crystalline and epitaxially oriented with respect to the Bi2Te3 thin film. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy show an atomically sharp FeICu1−xSe/Bi2Te3 interface. The FexCu1−xSe/Bi2Te3 interface is determined by Se–Te bonds and no misfit dislocations are observed, despite the different lattice symmetries and large lattice mismatch of ~19%. First-principle calculations show that the large strain at the FexCu1−xSe/Bi2Te3 interface can be accommodated by van der Waals-like bonding between Se and Te atoms.

    更新日期:2017-07-08
  • Beyond 8% ultrathin kesterite Cu2ZnSnS4 solar cells by interface reaction route controlling and self-organized nanopattern at the back contact
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Fangyang Liu, Jialiang Huang, Kaiwen Sun, Chang Yan, Yansong Shen, Jongsung Park, Aobo Pu, Fangzhou Zhou, Xu Liu, John A Stride, Martin A Green, Xiaojing Hao

    Highly efficient, ultrathin (~400 nm) pure sulfide kesterite Cu2ZnSnS4 (CZTS) solar cells have been realized by interface reaction route controlling and self-organized nano-pattern at the back contact. The Al2O3 intermediate layer introduced at the Mo/CZTS interface can effectively inhibit the detrimental interfacial reaction between CZTS and Mo in the initial stage of sulfurization, and then turns into a self-organized nanopattern yielding a nanoscale opening for electrical contact. With this interface modification, the traditional issues of phase segregation (secondary phases) and voids at the back contact region can be well addressed, which greatly improves uniformity and reduces back contact recombination. As a result, this interface modification not only leads to beyond 8% ultrathin CZTS solar cells but also yields two certificated world record efficiencies: 9.26% for 0.237 cm2 small area and 7.61% for 1 cm2 standard kesterite CZTS solar cells (normal thickness).

    更新日期:2017-07-08
  • Three-dimensional buckled honeycomb boron lattice with vacancies as an intermediate phase on the transition pathway from α-B to γ-B
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Woo Hyun Han, Young Jun Oh, Duk-Hyun Choe, Sunghyun Kim, In-Ho Lee, Kee Joo Chang

    In the phase diagram of elemental boron, an unknown high-pressure form was identified as γ-orthorhombic boron (γ-B28), provoking studies of the extraordinary properties of its main building blocks, B12 icosahedra and B2 dumbbells. Although two low-pressure phases, α- and β-rhombohedral boron (α-B12 and β-B106), are also composed of icosahedra, the detailed kinetics and mechanisms of the structural transition from α-B12 or β-B106 to γ-B28 remain poorly understood. We report on new metastable boron phases formed during the transition in high-pressure high-temperature conditions that were discovered using the crystal structure search method. The metastable phases are understood to be a three-dimensional buckled defective honeycomb lattice in which boron vacancies lead to a dynamically and mechanically stable structure with triangular motifs. We suggest that the metastable phases act as intermediate states on the transition pathway from α-B12 to γ-B28 owing to their structural flexibility and low enthalpies, in the framework of Ostwald’s step rule.

    更新日期:2017-07-08
  • Construction of a photothermal Venus flytrap from conductive polymer bimorphs
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Hanwhuy Lim, Teahoon Park, Jongbeom Na, Chihyun Park, Byeonggwan Kim, Eunkyoung Kim

    A photothermally foldable soft bimorph was prepared via the dry transfer of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with tosylate onto a poly(dimethylsiloxane) film. The photothermal folding was optimized via reversible actuation by controlling the thickness of each layer and the temperature increase to afford large deflection and displacement up to 150° and >20 mm, respectively, upon exposure to near-infrared (NIR) light (808 nm). A two-dimensional array of the bimorph converted into complex three-dimensional architectures, such as a Venus flytrap, under light and reversibly unfolded in the dark. Taking advantage of the photothermal nature of PEDOT, a localized heat pocket was generated inside the folding structure. Thus, a Venus flytrap with a hot pocket reaching 100 °C was realized for the first time. The Venus flytrap could trap and move an object within a few seconds of NIR exposure.

    更新日期:2017-07-08
  • Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-07-01
    Dae-wook Kim, Hiromasa Shiiba, Nobuyuki Zettsu, Tetsuya Yamada, Takeshi Kimijima, Gabriel Sánchez-Santolino, Ryo Ishikawa, Yuichi Ikuhara, Katsuya Teshima

    Small amounts of fluorine substituting for oxygen deficiencies could reduce Mn dissolution, enhancing the cyclability in spinel-type lithium nickel manganese oxides (LiNi0.5Mn1.5O4). Fluorine anion incorporation simultaneously enhances the C-rate capability and specific capacity fading. We used experimental and theoretical approaches to obtain a full picture of the mixed-anion effects for LiNi0.5Mn1.5O4−xFx cathode materials. The fluorine anion reduced the activation barrier for lithium-ion hopping along the most energetically preferable 8a-16c-8a route, enhancing the C-rate capability. Simultaneously, the coordination bond of the linear F−–Mn3+–F− (Mn@2F diagonal) arrangement increased the oxidation potential to 5.1 V (vs Li+/Li). This hampered full extraction of Li+ from the spinel lattice, which was triggered by the oxidation of Mn3+ below the cutoff voltage (3.5–4.8 V (vs Li+/Li)), leading to a capacity loss.

    更新日期:2017-07-08
  • Highly transparent to truly black electrochromic devices based on an ambipolar system of polyamides and viologen
    NPG Asia Mater. (IF 9.157) Pub Date : 
    Huan-Shen Liu, Bo-Cheng Pan, De-Cheng Huang, Yu-Ruei Kung, Chyi-Ming Leu, Guey-Sheng Liou

    Highly transparent to truly black electrochromic devices based on an ambipolar system of polyamides and viologen NPG Asia Materials 9, e388 (June 2017). doi:10.1038/am.2017.57 Authors: Huan-Shen Liu, Bo-Cheng Pan, De-Cheng Huang, Yu-Ruei Kung, Chyi-Ming Leu & Guey-Sheng Liou

    更新日期:2017-06-24
  • Thermoelectric performance of CuFeS2+2x composites prepared by rapid thermal explosion
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-06-01
    Hongyao Xie, Xianli Su, Yonggao Yan, Wei Liu, Liangjun Chen, Jiefei Fu, Jihui Yang, Ctirad Uher, Xinfeng Tang

    Although many thermoelectric materials, such as Bi2Te3, PbTe and CoSb3, possess excellent thermoelectric properties, they often contain toxic and expensive elements. Moreover, most of them are synthesized by processes such as vacuum melting, mechanical alloying or solid-state reactions, which are highly energy and time intensive. All these factors limit commercial applications of the thermoelectric materials. Therefore, it is imperative to develop efficient, inexpensive and non-toxic materials and explore rapid and low-cost synthesis methods. Herein we demonstrated a rapid, facile and low-cost synthesis route that combines thermal explosion (TE) with plasma-activated sintering and used it to prepare environmentally benign CuFeS2+2x. The phase transformation that occurred during the TE and correlations between the microstructure and transport properties were investigated. In a TE process, single-phase CuFeS2 was obtained in a short time and the thermoelectric performance of the bulk samples was better than that of the samples that were synthesized using traditional methods. Furthermore, the effect of phase boundaries on the transport properties was investigated and the underlying physical mechanisms that led to an improvement in the thermoelectric performance were revealed. This work provides several new ideas regarding the TE process and its utilization in the synthesis of thermoelectric materials.

    更新日期:2017-06-24
  • Pine cone scale-inspired motile origami
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-06-01
    Kahye Song, Sang Joon Lee

    Stimuli-sensitive hydrogels have received attention because of their potential applications in various fields. Stimuli-directed motion offers many practical applications, such as in drug delivery systems and actuators. Directed motion of asymmetric hydrogels has long been designed; however, few studies have investigated the motion control of symmetric hydrogels. We designed a pine cone scale-inspired movable temperature-sensitive symmetric hydrogel that contains Fe3O4. Alignment of Fe3O4 along the magnetic force is key in motion control in which Fe3O4 acts like fibers in a pine cone scale. Although a homogeneous temperature-sensitive hydrogel cannot respond to a temperature gradient, the Fe3O4-containing hydrogel demonstrates considerable bending motion. Varying degrees and directions of motion are easily facilitated by controlling the amount and alignment angle of the Fe3O4. The shape of the hydrogel layer also influences the morphological structure. This study introduced facile and low-cost methods to control various bending motions. These results can be applied to many fields of engineering, including industrial engineering.

    更新日期:2017-06-17
  • Intrinsically low thermal conductivity from a quasi-one-dimensional crystal structure and enhanced electrical conductivity network via Pb doping in SbCrSe3
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-06-01
    Dingfeng Yang, Wei Yao, Yanci Yan, Wujie Qiu, Lijie Guo, Xu Lu, Ctirad Uher, Xiaodong Han, Guoyu Wang, Tao Yang, Xiaoyuan Zhou

    The development of new routes for the production of thermoelectric materials with low-cost and high-performance characteristics has been one of the long-term strategies for saving and harvesting thermal energy. Herein, we report a new approach for improving thermoelectric properties by employing the intrinsically low thermal conductivity of a quasi-one-dimensional (quasi-1D) crystal structure and optimizing the power factor with aliovalent ion doping. As an example, we demonstrated that SbCrSe3, in which two parallel chains of CrSe6 octahedra are linked by antimony atoms, possesses a quasi-1D property that resulted in an ultra-low thermal conductivity of 0.56 W m−1 K−1 at 900 K. After maximizing the power factor by Pb doping, the peak ZT value of the optimized Pb-doped sample reached 0.46 at 900 K, which is an enhancement of 24 times that of the parent SbCrSe3 structure. The mechanisms that lead to low thermal conductivity derive from anharmonic phonons with the presence of the lone-pair electrons of Sb atoms and weak bonds between the CrSe6 double chains. These results shed new light on the design of new and high-performance thermoelectric materials.

    更新日期:2017-06-10
  • A new biocatalyst employing pyrenecarboxaldehyde as an anodic catalyst for enhancing the performance and stability of an enzymatic biofuel cell
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-06-01
    Marcelinus Christwardana, Yongjin Chung, Yongchai Kwon

    A new enzyme catalyst consisting of pyrenecarboxaldehyde (PCA) and glucose oxidase (GOx) immobilized on polyethyleneimine (PEI) and a carbon nanotube supporter (CNT/PEI/[PCA/GOx]) is suggested, and the performance and stability of an enzymatic biofuel cell (EBC) using the new catalyst are evaluated. Using PCA, the amount of immobilized GOx increases (3.3 U mg−1) and the electron transfer rate constant of the CNT/PEI/[PCA/GOx] is promoted (11.51 s−1). Also, the catalyst induces excellent EBC performance (maximum power density (MPD) of 2.1 mW cm−2), long-lasting stability (maintenance of 93% of the initial MPD after 4 weeks) and superior catalytic activity (flavin adenine dinucleotide redox reaction rate of 0.62 mA cm−2 and Michaelis–Menten constant of 0.99 mM). These characteristics are ascribed to effects of (i) electron collection due to hydrophobic interactions, (ii) electron transfer pathways due to π-conjugated bonds and (iii) enzyme stabilization due to π-hydrogen bonds that are newly induced by the PCA/GOx composite. The existence of such positive interactions is properly verified using X-ray photoelectron spectroscopy and enzyme activity measurements.

    更新日期:2017-06-03
  • Superaerophobic graphene nano-hills for direct hydrazine fuel cells
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Kamran Akbar, Jung Hwa Kim, Zonghoon Lee, Minsoo Kim, Yeonjin Yi, Seung-Hyun Chun

    Hydrazine fuel-cell technology holds great promise for clean energy, not only because of the greater energy density of hydrazine compared to hydrogen but also due to its safer handling owing to its liquid state. However, current technologies involve the use of precious metals (such as platinum) for hydrazine oxidation, which hinders the further application of hydrazine fuel-cell technologies. In addition, little attention has been devoted to the management of gas, which tends to become stuck on the surface of the electrode, producing overall poor electrode efficiencies. In this study, we utilized a nano-hill morphology of vertical graphene, which efficiently resolves the issue of the accumulation of gas bubbles on the electrode surface by providing a nano-rough-edged surface that acts as a superaerophobic electrode. The growth of the vertical graphene nano-hills was achieved and optimized by a scalable plasma-enhanced chemical vapor deposition method. The resulting metal-free graphene-based electrode showed the lowest onset potential (−0.42 V vs saturated calomel electrode) and the highest current density of all the carbon-based materials reported previously for hydrazine oxidation.

    更新日期:2017-05-29
  • Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Zhanhao Hu, Zhiming Zhong, Kai Zhang, Zhicheng Hu, Chen Song, Fei Huang, Junbiao Peng, Jian Wang, Yong Cao

    In organic electronic devices, the interfacial dipole at organic/metal interfaces is critical in determining the carrier injection or extraction that limits the performance of the device. A novel technique to enable the direct measurement of underburied dipoles is developed and demonstrated. By tilting the shadow mask by a small angle, metal atoms diffuse into the opening slit to form an ultrathin metal layer during the evaporation process. As the ultrathin metal layer cannot screen out the dipole-induced surface work function change, the dipole strength and direction at the organic/metal interface can be revealed. It was found that the polarity of the organic material, the Fermi-level pinning and the interface morphology all play important roles in dipole formation. By comparing the energy level shifts at the organic/pre-deposited metal and organic/post-deposited metal interfaces, the dipole formed by molecular interactions could be distinguished from the dipole formed by Fermi-level pinning.

    更新日期:2017-05-29
  • A monolithic hydro/organo macro copolymer actuator synthesized via interfacial copolymerization
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Feilong Zhang, Junbing Fan, Pengchao Zhang, Mingjie Liu, Jingxin Meng, Lei Jiang, Shutao Wang

    Synthetic polymer actuators have attracted increasing attention for their potential applications in artificial muscles, soft robotics and sensors. The majority of previous efforts have focused on smart hydrogels with bilayer structures that can change their shape in response to environmental stimuli, such as temperature, light and certain chemicals. However, the practical application of hydrogels is limited because of their low modulus and weak mechanical strength. Here we synthesized a robust monolithic actuator of a macro-scale hydro/organo binary cooperative Janus copolymer film. The process involves direct, one-step interfacial polymerization of immiscible hydrophilic and hydrophobic vinyl monomer solutions, and the resultant product exhibited binary cooperative shape transformation to multiple external stimuli. The Janus copolymer film can work in both aqueous solutions and organic solvents, with bidirectional and site-specific bending arising from cooperative asymmetric swelling/shrinking of the hydrogel and organogel networks. In addition, the as-prepared Janus copolymer film can act as a sensor element for solvent leakage detection. This binary cooperative strategy is applicable to most immiscible monomer systems and provides a general approach to developing novel functional copolymer materials.

    更新日期:2017-05-29
  • Nanogenerator-induced synaptic plasticity and metaplasticity of bio-realistic artificial synapses
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Bo-Yun Kim, Hyun-Gyu Hwang, Jong-Un Woo, Woong-Hee Lee, Tae-Ho Lee, Chong-Yun Kang, Sahn Nahm

    A bio-realistic artificial synapse integrated with a nanogenerator (NG), which can be used in neuromorphic systems, is demonstrated for self-powered biomedical devices in this study. Biocompatible amorphous (Na0.5K0.5)NbO3 (NKN) films are grown on TiN/polyimide substrates to synthesize NKN memristors for use as artificial synapses. Various synaptic functions are realized in NKN memristors, which are driven by a pulse generator and an NG. The synaptic plasticity of the NKN memristor results from the oxygen vacancy movements and the changes in the shape of the oxygen vacancy filaments. As a further step toward developing more bio-realistic artificial synapses, various types of metaplasticity and their mechanisms in the NKN memristors are investigated. Moreover, the metaplasticity of spike-timing-dependent plasticity (a key characteristic of biological synapses) is realized in the NKN memristor with a priming stimulus given by the NKN NG.

    更新日期:2017-05-29
  • Hidden orbital polarization in diamond, silicon, germanium, gallium arsenide and layered materials
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Ji Hoon Ryoo, Cheol-Hwan Park

    It was previously believed that the Bloch electronic states of non-magnetic materials with inversion symmetry cannot have finite spin polarizations. However, since the seminal work by Zhang et al. (Nat. Phys. 10, 387–393 (2014)) on local spin polarizations of Bloch states in non-magnetic, centrosymmetric materials, the scope of spintronics has been significantly broadened. Here, we show, using a framework that is universally applicable independent of whether hidden spin polarizations are small (e.g., diamond, Si, Ge and GaAs) or large (e.g., MoS2 and WSe2), that the corresponding quantity arising from orbital—instead of spin—degrees of freedom, the hidden orbital polarization is (i) much more abundant in nature since it exists even without spin–orbit coupling and (ii) more fundamental since the interband matrix elements of the site-dependent orbital angular momentum operator determine the hidden spin polarization. We predict that the hidden spin polarization of transition metal dichalcogenides is reduced significantly upon compression. We suggest experimental signatures of hidden orbital polarization from photoemission spectroscopies and demonstrate that the current-induced hidden orbital polarization may play a far more important role than its spin counterpart in antiferromagnetic information technology by calculating the current-driven antiferromagnetism in compressed silicon.

    更新日期:2017-05-29
  • In vivo high-efficiency targeted photodynamic therapy of ultra-small Fe3O4@polymer-NPO/PEG-Glc@Ce6 nanoprobes based on small size effect
    NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01
    Ting Yin, Qian Zhang, Haigang Wu, Guo Gao, Joseph G Shapter, Yulan Shen, Qiaozhi He, Peng Huang, Wen Qi, Daxiang Cui

    Effectively prolonging the residence time of nanoprobes in the tumor region and reducing the accumulation of nanoprobes in the vital organs (for example, lung, liver and spleen) is crucial for high-efficiency photodynamic therapy (PDT) of cancer. Herein, we systematically report an ultra-small and highly stable nanoplatform with diameters of 4, 8 and 13 nm that exhibited excellent photodynamic therapeutic efficacy using Fe3O4@polymer-NPO/PEG-Glc@Ce6 nanoprobes. Based on the small size effect, the nanoprobes displayed lower cytotoxicity and excellent biocompatibility. Owing to the synergistic virtues of markedly active targeting and intrinsic small size effect, the Fe3O4@P-NPO/PEG-Glc@Ce6 nanoprobes can effectively prolong their residence time in the tumor region and reduce accumulation in the normal organs. Benefitting from the small size effect, the synthesized Fe3O4@P-NPO/PEG-Glc@Ce6 nanoprobes exhibited excellent tumor-targeting capability and photodynamic therapeutic efficacy by inhibiting the growth of tumors in mice under visible red light irradiation with a relatively lower power. The successful application of the small size effect in Fe3O4@P-NPO/PEG-Glc@Ce6 nanoprobes to significantly improve the PDT efficiency in our strategy suggests new building blocks for PDT of tumors and paves a new way for clinical therapies and translation in the near future.

    更新日期:2017-05-29
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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