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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
A rollable ultra-light polymer electrolyte membrane fuel cell NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01 Taehyun Park, Yun Sik Kang, Segeun Jang, Suk Won Cha, Mansoo Choi, Sung Jong Yoo
We have developed a highly flexible, ultra-light and thin polymer electrolyte membrane fuel cell that can be used as a portable power source for flexible electronics. To achieve such flexibility and ultra-lightness, we fabricated a thin flow-field plate using a thermal imprinting process and combined it with a laser-machined metal current collector. The air-breathing fuel cell, with a thickness of 0.992 mm and a weight of 2.23 g, demonstrated a total power of 508 mW and a performance degradation of <10% after severe bending fatigue (200 repeated bends). This high power per weight (0.228 W g−1) and robust bending durability have never been observed before. The highly flexible architecture enabled the operation of the fuel cell in an S-shape or even in a rolled-up state without any significant performance loss. We have fabricated a cylindrical planar stack of 10 fuel cells and successfully carried out its outdoor operation to demonstrate its practical applications in various fields.
Supramolecular thermoplastics and thermoplastic elastomer materials with self-healing ability based on oligomeric charged triblock copolymers NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-01 Lenny Voorhaar, Maria Mercedes Diaz, Frederic Leroux, Sarah Rogers, Artem M Abakumov, Gustaaf Van Tendeloo, Guy Van Assche, Bruno Van Mele, Richard Hoogenboom
Supramolecular polymeric materials constitute a unique class of materials held together by non-covalent interactions. These dynamic supramolecular interactions can provide unique properties such as a strong decrease in viscosity upon relatively mild heating, as well as self-healing ability. In this study we demonstrate the unique mechanical properties of phase-separated electrostatic supramolecular materials based on mixing of low molar mass, oligomeric, ABA-triblock copolyacrylates with oppositely charged outer blocks. In case of well-chosen mixtures and block lengths, the charged blocks are phase separated from the uncharged matrix in a hexagonally packed nanomorphology as observed by transmission electron microscopy. Thermal and mechanical analysis of the material shows that the charged sections have a Tg closely beyond room temperature, whereas the material shows an elastic response at temperatures far above this Tg ascribed to the electrostatic supramolecular interactions. A broad set of materials having systematic variations in triblock copolymer structures was used to provide insights in the mechanical properties and and self-healing ability in correlation with the nanomorphology of the materials.
A monolithic hydro/organo macro copolymer actuator synthesized via interfacial copolymerization NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-19 Feilong Zhang, Junbing Fan, Pengchao Zhang, Mingjie Liu, Jingxin Meng, Lei Jiang, Shutao Wang
Authors: Feilong Zhang, Junbing Fan, Pengchao Zhang, Mingjie Liu, Jingxin Meng, Lei Jiang & Shutao Wang
Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-19 Zhanhao Hu, Zhiming Zhong, Kai Zhang, Zhicheng Hu, Chen Song, Fei Huang, Junbiao Peng, Jian Wang, Yong Cao
Authors: Zhanhao Hu, Zhiming Zhong, Kai Zhang, Zhicheng Hu, Chen Song, Fei Huang, Junbiao Peng, Jian Wang & Yong Cao
Superaerophobic graphene nano-hills for direct hydrazine fuel cells NPG Asia Mater. (IF 9.157) Pub Date : 2017-05-19 Kamran Akbar, Jung Hwa Kim, Zonghoon Lee, Minsoo Kim, Yeonjin Yi, Seung-Hyun Chun
Authors: Kamran Akbar, Jung Hwa Kim, Zonghoon Lee, Minsoo Kim, Yeonjin Yi & Seung-Hyun Chun
Phase separation of composite materials through simultaneous polymerization and crystallization NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-21 Kosuke Sato, Yuya Oaki, Hiroaki Imai
Authors: Kosuke Sato, Yuya Oaki & Hiroaki Imai
A 3D-printed scaffold with MoS2 nanosheets for tumor therapy and tissue regeneration NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-21 Xiaocheng Wang, Tao Li, Hongshi Ma, Dong Zhai, Chuan Jiang, Jiang Chang, Jinwu Wang, Chengtie Wu
Authors: Xiaocheng Wang, Tao Li, Hongshi Ma, Dong Zhai, Chuan Jiang, Jiang Chang, Jinwu Wang & Chengtie Wu
Single crystals of caesium formamidinium lead halide perovskites: solution growth and gamma dosimetry NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-14 Olga Nazarenko, Sergii Yakunin, Viktoriia Morad, Ihor Cherniukh, Maksym V Kovalenko
Authors: Olga Nazarenko, Sergii Yakunin, Viktoriia Morad, Ihor Cherniukh & Maksym V Kovalenko
Tough, self-healable and tissue-adhesive hydrogel with tunable multifunctionality NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-14 Lu Han, Liwei Yan, Kefeng Wang, Liming Fang, Hongping Zhang, Youhong Tang, Yonghui Ding, Lu-Tao Weng, Jielong Xu, Jie Weng, Yujie Liu, Fuzeng Ren, Xiong Lu
Authors: Lu Han, Liwei Yan, Kefeng Wang, Liming Fang, Hongping Zhang, Youhong Tang, Yonghui Ding, Lu-Tao Weng, Jielong Xu, Jie Weng, Yujie Liu, Fuzeng Ren & Xiong Lu
Synergistic protective effect of a BN-carbon separator for highly stable lithium sulfur batteries NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-14 Patrick Joo Hyun Kim, Jihoon Seo, Kun Fu, Junghyun Choi, Zhiming Liu, Jiseok Kwon, Liangbing Hu, Ungyu Paik
Authors: Patrick Joo Hyun Kim, Jihoon Seo, Kun Fu, Junghyun Choi, Zhiming Liu, Jiseok Kwon, Liangbing Hu & Ungyu Paik
New photopatternable polyimide and programmable nonvolatile memory performances NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-14 Suk Gyu Hahm, Samdae Park, Moonhor Ree
Authors: Suk Gyu Hahm, Samdae Park & Moonhor Ree
Engineering protein nanocages as carriers for biomedical applications NPG Asia Mater. (IF 9.157) Pub Date : 2017-04-07 Sathyamoorthy Bhaskar, Sierin Lim
Authors: Sathyamoorthy Bhaskar & Sierin Lim
Microstructure dynamics of rechargeable battery materials studied by advanced transmission electron microscopy NPG Asia Mater. (IF 9.157) Pub Date : 2017-03-10 Yuren Wen, Dongdong Xiao, Xiaozhi Liu, Lin Gu
Authors: Yuren Wen, Dongdong Xiao, Xiaozhi Liu & Lin Gu
Conversion of an ultra-wide bandgap amorphous oxide insulator to a semiconductor NPG Asia Mater. (IF 9.157) Pub Date : 2017-03-10 Junghwan Kim, Takumi Sekiya, Norihiko Miyokawa, Naoto Watanabe, Koji Kimoto, Keisuke Ide, Yoshitake Toda, Shigenori Ueda, Naoki Ohashi, Hidenori Hiramatsu, Hideo Hosono, Toshio Kamiya
Authors: Junghwan Kim, Takumi Sekiya, Norihiko Miyokawa, Naoto Watanabe, Koji Kimoto, Keisuke Ide, Yoshitake Toda, Shigenori Ueda, Naoki Ohashi, Hidenori Hiramatsu, Hideo Hosono & Toshio Kamiya
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
- Acad. Manag. Ann.
- Acc. Chem. Res.
- ACS Appl. Mater. Interfaces
- ACS Biomater. Sci. Eng.
- ACS Catal.
- ACS Cent. Sci.
- ACS Chem. Biol.
- ACS Chem. Neurosci.
- ACS Comb. Sci.
- ACS Earth Space Chem.
- ACS Energy Lett.
- ACS Infect. Dis.
- ACS Macro Lett.
- ACS Med. Chem. Lett.
- ACS Nano
- ACS Omega
- ACS Photonics
- ACS Sens.
- ACS Sustainable Chem. Eng.
- ACS Synth. Biol.
- Acta Mater.
- Acta Neuropathol.
- Adv. Drug Deliver. Rev.
- Adv. Electron. Mater.
- Adv. Energy Mater.
- Adv. Funct. Mater.
- Adv. Healthcare Mater.
- Adv. Mater.
- Adv. Opt. Mater.
- Adv. Opt. Photon.
- Adv. Phys.
- Adv. Sci.
- Adv. Synth. Catal.
- AlChE J.
- Alzheimers Dement.
- Am. J. Hum. Genet.
- Am. J. Psychiatry
- Am. J. Respir. Crit. Care Med.
- Anal. Chem.
- Anal. Chim. Acta
- Anal. Methods
- Angew. Chem. Int. Ed.
- Ann. Intern. Med.
- Ann. Neurol.
- Ann. Oncol.
- Ann. Rheum. Dis.
- Annu. Rev. Anal. Chem.
- Annu. Rev. Astron. Astrophys.
- Annu. Rev. Biochem.
- Annu. Rev. Biomed. Eng.
- Annu. Rev. Biophys.
- Annu. Rev. Cell Dev. Biol.
- Annu. Rev. Clin. Psychol.
- Annu. Rev. Condens. Matter Phys.
- Annu. Rev. Earth Planet. Sci.
- Annu. Rev. Ecol. Evol. Syst.
- Annu. Rev. Entomol.
- Annu. Rev. Fluid Mech.
- Annu. Rev. Immunol.
- Annu. Rev. Mar. Sci.
- Annu. Rev. Mater. Res.
- Annu. Rev. Med.
- Annu. Rev. Microbiol.
- Annu. Rev. Neurosci.
- Annu. Rev. Nutr.
- Annu. Rev. Pathol. Mech. Dis.
- Annu. Rev. Pharmacol. Toxicol.
- Annu. Rev. Phys. Chem.
- Annu. Rev. Physiol.
- Annu. Rev. Phytopathol.
- Annu. Rev. Plant Biol.
- Annu. Rev. Psychol.
- Annu. Rev. Publ. Health
- Annu. Rev. Virol.
- Antivir. Res.
- Appl. Catal. A Gen.
- Appl. Catal. B Environ.
- Appl. Energy
- Appl. Phys. Lett.
- Appl. Phys. Rev.
- Arch. Pharm.
- Asian J. Org. Chem.
- CA: Cancer J. Clin.
- Cancer Cell
- Cancer Discov.
- Cancer Res.
- Carbohydr. Polym.
- Catal. Sci. Technol.
- Catal. Today
- Cell Chem. Bio.
- Cell Host Microbe
- Cell Metab.
- Cell Res.
- Cell Stem Cell
- Ceram. Int.
- Chem. Asian J.
- Chem. Bio. Drug Des.
- Chem. Commun.
- Chem. Educ. Res. Pract.
- Chem. Eng. J.
- Chem. Eur. J.
- Chem. Mater.
- Chem. Phys.
- Chem. Phys. Lett.
- Chem. Res. Toxicol.
- Chem. Rev.
- Chem. Sci.
- Chem. Soc. Rev.
- Circ. Res.
- Clin. Cancer Res.
- Clin. Microbiol. Rev.
- Compos. Part A Appl. Sci. Manuf.
- Comput. Fluids
- Coordin. Chem. Rev.
- Corros. Sci.
- Crit. Rev. Food Sci. Nutr.
- Cryst. Growth Des.
- Curr. Opin. Biotech.
- Curr. Opin. Cell Biol.
- Ecol. Lett.
- Electrochem. Commun.
- Electrochim. Acta
- Endocr. Rev.
- Energy Environ. Sci.
- Energy Fuels
- Environ. Pollut.
- Environ. Sci. Technol.
- Environ. Sci. Technol. Lett.
- Environ. Sci.: Nano
- Environ. Sci.: Processes Impacts
- Environ. Sci.: Water Res. Technol.
- Eur. Heart J.
- Eur. J. Inorg. Chem.
- Eur. J. Med. Chem.
- Eur. J. Org. Chem.
- Eur. Polym. J.
- Eur. Respir. J.
- Eur. Urol.
- Ecol. Lett.
- Electrochem. Commun.
- Electrochim. Acta
- Endocr. Rev.
- Energy Environ. Sci.
- Energy Fuels
- Environ. Pollut.
- Environ. Sci. Technol.
- Environ. Sci. Technol. Lett.
- Environ. Sci.: Nano
- Environ. Sci.: Processes Impacts
- Environ. Sci.: Water Res. Technol.
- Eur. Heart J.
- Eur. J. Inorg. Chem.
- Eur. J. Med. Chem.
- Eur. J. Org. Chem.
- Eur. Polym. J.
- Eur. Respir. J.
- Eur. Urol.
- J Nucl. Med.
- J. Agric. Food Chem.
- J. Allergy Clin. Immunol.
- J. Alloys Compd.
- J. Am. Ceram. Soc.
- J. Am. Chem. Soc.
- J. Am. Coll. Cardiol.
- J. Anal. At. Spectrom.
- J. Antibiot.
- J. Cachexia Sarcopenia Muscle
- J. Catal.
- J. Chem. Educ.
- J. Chem. Eng. Data
- J. Chem. Inf. Model.
- J. Chem. Phys.
- J. Chem. Theory Comput.
- J. Chromatogr. A
- J. Chromatogr. B
- J. Clin. Invest.
- J. Clin. Oncol.
- J. Comput. Chem.
- J. Comput. Phys.
- J. Control. Release
- J. Cryst. Growth
- J. Electrochem. Soc.
- J. Eur. Ceram. Soc.
- J. Exp. Med.
- J. Fluid Mech.
- J. Fluorine Chem.
- J. Funct. Foods
- J. Hazard. Mater.
- J. Hepatol.
- J. Mater. Chem. A
- J. Mater. Chem. B
- J. Mater. Chem. C
- J. Med. Chem.
- J. Membr. Sci.
- J. Nat. Gas Sci. Eng.
- J. Nat. Prod.
- J. Natl. Cancer Inst.
- J. Org. Chem.
- J. Photochem. Photobiol. C Photochem. Rev.
- J. Phys. Chem. A
- J. Phys. Chem. B
- J. Phys. Chem. C
- J. Phys. Chem. Lett.
- J. Pineal. Res.
- J. Power Sources
- J. Proteome Res.
- J. Virol.
- JACC Cardiovasc. Imag.
- JAMA Intern. Med.
- JAMA Neurol.
- JAMA Oncol.
- JAMA Pediatr.
- JAMA Psychiatry
- Macromol. Rapid Commun.
- Mass Spectrom. Rev.
- Mater. Chem. Front.
- Mater. Des.
- Mater. Horiz.
- Mater. Sci. Eng. A
- Mater. Sci. Eng. R Rep.
- Mater. Today
- Meat Sci.
- Med. Chem. Commun.
- Med. Res. Rev.
- Microbiol. Mol. Biol. Rev.
- Microchim. Acta
- Mol. Biosyst.
- Mol. Cancer Ther.
- Mol. Catal.
- Mol. Cell
- Mol. Pharmaceutics
- Mol. Psychiatry
- Mol. Syst. Des. Eng.