Showing papers in "Npg Asia Materials in 2015"
TL;DR: In this paper, hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity, are prepared, and a specific capacitance increase of >62%, from 445 to 718 ǫ F g−1, is achieved at a current density of 1ǫ Aǫg−1.
Abstract: Hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity, are prepared. A specific capacitance increase of >62%, from 445 to 718 F g−1, is achieved at a current density of 1 A g−1. A full cell combined with NiCo2O4 and activated carbon is assembled, and an energy density of 34.8 Wh kg−1 is obtained at a power density of 464 W kg−1.
174 citations
TL;DR: Xun et al. as discussed by the authors used direct annealing without a sintering process to obtain high-density Cu2Te samples and showed that this method can save substantial time and cost during the sample growth.
Abstract: Recently, Cu2-δS and Cu2-δSe were reported to have an ultralow thermal conductivity and high thermoelectric figure of merit zT. Thus, as a member of the copper chalcogenide group, Cu2-δTe is expected to possess superior zTs because Te is less ionic and heavy. However, the zT value is low in the Cu2Te sintered using spark plasma sintering, which is typically used to fabricate high-density bulk samples. In addition, the extra sintering processes may change the samples’ compositions as well as their physical properties, especially for Cu2Te, which has many stable and meta-stable phases as well as weaker ionic bonding between Cu and Te as compared with Cu2S and Cu2Se. In this study, high-density Cu2Te samples were obtained using direct annealing without a sintering process. In the absence of sintering processes, the samples’ compositions could be well controlled, leading to substantially reduced carrier concentrations that are close to the optimal value. The electrical transports were optimized, and the thermal conductivity was considerably reduced. The zT values were significantly improved—to 1.1 at 1000 K—which is nearly 100% improvement. Furthermore, this method saves substantial time and cost during the sample’s growth. The study demonstrates that Cu2-δX (X=S, Se and Te) is the only existing system to show high zTs in the series of compounds composed of three sequential primary group elements. A time-saving procedure for boosting the performance of experimental thermoelectric energy harvesters has been developed by a team in China. Recently, copper sulfide (CuS) and copper selenide (CuSe) compounds have garnered interest as thermoelectric generators because their extraordinarily low thermal conductivities enable highly efficient conversion of temperature swings into electricity. However, copper telluride (CuTe) compounds, which have even lower lattice thermal conductivities than CuS or CuSe compounds, have so far displayed only moderate thermoelectric capacities. Xun Shi at the Chinese Academy of Sciences and co-workers solved this mystery by eliminating the spark plasma sintering procedure normally used to produce high-density CuS and CuSe thermoelectrics. The researchers raised the thermoelectric efficiency by a few times by directly annealing CuTe crystals. They attribute this increase to better control over carrier concentrations in the samples’ crystal structure. Enhanced thermoelectric figure of merit in the fully densified Cu2Te bulk materials by direct annealing method.
173 citations
TL;DR: The 3D network structure of NiCo2S4 nanosheets offers the additional advantages of large surface area, efficient electron and ion transport capability, easy access of electrolyte to the electrode surface, sufficient void space and mechanical robustness as discussed by the authors.
Abstract: We present the design and synthesis of three-dimensional (3D)-networked NiCo2S4 nanosheet arrays (NSAs) grown on carbon cloth along with their novel application as anodes in lithium-ion batteries The relatively small (~60%) volumetric expansion of NiCo2S4 nanosheets during the lithiation process was confirmed by in situ transmission electron microscopy and is attributed to their mesoporous nature The 3D network structure of NiCo2S4 nanosheets offers the additional advantages of large surface area, efficient electron and ion transport capability, easy access of electrolyte to the electrode surface, sufficient void space and mechanical robustness The fabricated electrodes exhibited outstanding lithium-storage performance including high specific capacity, excellent cycling stability and high rate of performance A reversible capacity of ~1275 mAh g−1 was obtained at a current density of 1000 mA g−1, and the devices retained ~1137 mAh g−1 after 100 cycles, which is the highest value reported to date for electrodes made of metal sulfide nanostructures or their composites Our results suggest that 3D-networked NiCo2S4 NSA/carbon cloth composites are a promising material for electrodes in high-performance lithium-ion batteries Three-dimensional networks of NiCo2S4 nanosheets on carbon cloth substrates are highly promising as anodes for lithium-ion batteries Nanostructures made from metal sulphides make attractive anode materials for lithium-ion batteries except they tend to undergo large volume changes during electrochemical reactions, which lead to reduced capacity and poor cycling stability Now, Wenjun Zhang and colleagues at City University of Hong Kong and Donghua University in Shanghai have demonstrated that NiCo2S4 nanosheet arrays on carbon cloths expand by only about 60% during lithiation as a result of their mesoporous structure Furthermore, the arrays exhibited the highest specific capacity of any metal sulphide electrode reported to date as well as an excellent cycling stability and a high rate capability They are thus excellent candidates for anode materials in high-performance lithium-ion batteries 3D Networked NiCo2S4 nanosheet array/carbon cloth composites are synthesized by a facile hydrothermal reaction and subsequent sulfurization process, and the rational material composition and structure design lead to their outstanding overall performance as an anode material in lithium-ion batteries
159 citations
TL;DR: In this paper, a new high-κ dielectric material was identified by automated ab initio calculations on ~1800 oxides and the cubic BeO was found to possess an unprecedented material property of 10
Abstract: Novel high-κ dielectric materials are identified by automated ab initio calculations on ~1800 oxides. The cubic BeO is found to possess an unprecedented material property of 10 eV for band gap and 275 for dielectric constant. Candidate high-κ oxides are suggested for microelectronic devices such as CPU, DRAM and flash memory.
151 citations
TL;DR: In this paper, the authors exploit shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam, which resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1-96.0nm.
Abstract: The low cost, significant reduction potential and relative safety of the zinc electrode is a common hope for a reductant in secondary batteries, but it is limited mainly to primary implementation due to shape change. In this work, we exploit such shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam. Electrodeposition of zinc foam resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1–96.0 nm. The nanoporous zinc foam contributed to highly oriented crystals, high surface area and more rapid kinetics in contrast to conventional zinc in alkaline mediums. The anode material presented had a utilization of ~88% at full depth-of-discharge (DOD) at various rates indicating a superb rate capability. The rechargeability of Zn0/Zn2+ showed significant capacity retention over 100 cycles at a 40% DOD to ensure that the dendritic core structure was imperforated. The dendritic architecture was densified upon charge–discharge cycling and presented superior performance compared with bulk zinc electrodes. A synthetic method turns a problem with plate metal batteries into a path for greater stability and may lead to safer, cheaper batteries. Zinc is more abundant and easier to handle than lithium, but electrodes made from it suffer from shape-change effects that prevent stable cycling. Now, by electrodepositing nanoporous zinc foam onto a traditional current collector, Daniel Steingart from Princeton University in the USA and colleagues have exploited a problem with zinc electrodes — the formation of dendritic crystals that can short-circuit batteries. The team broke convention by deliberately conditioning their zinc electrodes at potentials far from equilibrium. This created a hyper-dendritic network foam that forms with 88% current efficiency and remains stable for over 100 recharge cycles — results superior to those of conventional batteries with non-porous zinc electrodes. The low cost, significant reduction potential and relative safety of the zinc electrode is a common hope for a reductant in secondary batteries, but it is limited mainly to primary implementation due to shape change. In this work, we exploit such shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam. Electrodeposition of zinc foam resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1–96.0 nm. The nanoporous zinc foam contributed to highly oriented crystals, high surface area and more rapid kinetics in contrast to conventional zinc in alkaline mediums. The anode material presented had a utilization of ~88% at full depth-of-discharge (DOD) at various rates indicating a superb rate capability. The rechargeability of Zn0/Zn2+ showed significant capacity retention over 100 cycles at a 40% DOD to ensure that the dendritic core structure was imperforated. The dendritic architecture was densified upon charge–discharge cycling and presented superior performance compared with bulk zinc electrodes.
149 citations
TL;DR: Tanaka et al. as discussed by the authors introduced the results of primarily recent studies on boron diketonate and related compounds containing polymers and particularly explained their optical properties, and the synthesis and emission properties of nanostructures are described, as are the modulation of optical properties by the application of mechanical stress.
Abstract: The synthesis and application of organoboron complexes are a highly relevant topic owng to their unique characteristics. Based on their emissive properties, these complexes have been used to make novel optical materials and devices; boron β-diketonate is a simple and robust organoboron complex. From a series of recent studies, unique and versatile optical properties have been reported. In this review, we introduce the results of primarily recent studies on boron diketonate and related compounds containing polymers and particularly explain their optical properties. Initially, the multi-emission of boron diketonate derivatives and its application to biotechnology are explained. Next, the formation of nanostructures and its emission properties are demonstrated. The modulation of optical properties by mechanical stress is also presented. Finally, recent progress in the development of solid-emissive materials are shown with boron diketonates and their derivatives, which have aggregation-induced emission properties. The versatility of boron diketonates as a building block for the preparation of functional optical materials is the focus of this review. Recent studies have revealed that boron diketonate and related compounds make versatile building blocks for functional optical materials. In particular, their ease of synthesis and emissive properties make them suitable for various optical materials and devices. Kazuo Tanaka and Yoshiki Chujo of Kyoto University in Japan provide an overview of recent progress in this area. They explain the dual emission of derivatives of boron diketonate and its application in biotechnology. The synthesis and emission properties of nanostructures are described, as are the modulation of optical properties by the application of mechanical stress. In addition, recent advances in the development of solid-emissive materials are illustrated by considering the aggregation-induced emission properties of boron diketonates and their derivatives. Tanaka and Chujo anticipate that these materials will spawn many new optical functional materials in the future. The synthesis and application of organoboron complexes are a topic with high relevance owing to their unique characteristics. This manuscript introduces the results primarily from recent studies of boron diketonates, ketoiminates and diiminates containing polymers and particularly focuses on their optical properties.
146 citations
TL;DR: In this article, a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)-O4 : Cr) was presented.
Abstract: We present a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)O4: Cr) and highlight their special optical characteristics of broad emission band (650-1200 nm, peaking at 800 nm) and long afterglow duration (>35h). In the context of materials selection, these systems successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. Zn2SnO4 is employed as a host to take advantage of its characteristic inverse spinel crystal structure, easy substitution into Zn2+ and Sn4+ sites by Cr3+ in distorted octahedral coordination and non-equivalent substitution. In this work, Al dopant was introduced both to precisely tailor the local crystal field around the activator center, Cr3+, and to redeploy trap distribution in the system. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and the formation of defects. The results demonstrate that the method employed here can be an effective way to fabricate multi-wavelength, low-cost, NIR phosphorescent phosphors with many potential multifunctional bio-imaging applications.
120 citations
TL;DR: In this paper, a stable and efficient solid-state solar cells have been made based on perovskite quantum dots of methylammonium lead bromide (MAPbBr3).
Abstract: Highly stable and efficient solid-state solar cells have been made based on perovskite quantum dots of methylammonium lead bromide (MAPbBr3). Sawanta Mali, Chang Su Shim and Chang Kook Hong of Chonnam National University in South Korea fabricated highly crystalline MAPbBr3 quantum dots by an ex situ process using dimethyl sulphoxide as a solvent and then examined their performance in perovskite solar cells having two different hole-transporting materials. They also produced quantum dots of different sizes by varying the solution processing conditions and found that the solar-cell performance depended significantly on the quantum dot size. The team obtained a maximum conversion efficiency of 11.46% when poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was used as the hole-transporting material and MAPbBr3 quantum dots with diameters smaller than three nanometres were used. They found that the solar cells were stable over a four-month period.
115 citations
TL;DR: A thermoresponsive hydrogel containing gold nanorods can reduce breast cancer recurrence by delivering thermotherapeutic and chemotherapeutic drug.
Abstract: Smart hydrogels that undergo structural changes in response to stimuli (for example, pH, heat, light) have promising biomedical applications as delivery systems, especially for the locally controlled release of drugs Early prevention of locoregional recurrence (LRR) is critical for patients who have undergone breast-conserving therapy This work reports the preparation of a hybrid hydrogel system in which gold nanorods (GNRs) were doped into a thermally responsive hydrogel A near-infrared (NIR) laser was used to trigger the release of loaded Doxorubicin (DOX) by utilizing the photothermal effect of GNRs to induce the contraction of the thermo-responsive hydrogels In a 4T1 breast cancer model of the in vivo locoregional prevention of post-operative recurrence, we found that after NIR irradiation, DOX/GNR-embedded Methoxylpoly(ethylene glycol)-poly(ɛ-caprolactone)-acryloyl chloride (PECA)/glycidylmethacrylated chitooligosaccharide (COS-GMA)/N-isopropylacrylamide (NIPAm)/acrylamide (AAm) (PCNA) hydrogels (DOX-PCNA-GNR hydrogels) significantly reduced tumor recurrence to 167%, compared with 50% for DOX-PCNA-GNRs without NIR irradiation, 833% for PCNA-GNRs with NIR irradiation, 100% for PCNA-GNRs without NIR irradiation, 833% for single systemic or local administration of Dox, 100% for intravenous DOX administration once or three times, and 100% for the blank control This study demonstrates that these DOX-PCNA-GNR hybrid hydrogels with NIR-triggered thermo-responsive drug release exhibit great potential in preventing post-operation cancer relapse A thermoresponsive hydrogel containing gold nanorods can reduce breast cancer recurrence by delivering thermotherapeutic and chemotherapeutic drug Effective inhibition of breast cancer relapse remains an important challenge Now, Zhi Yong Qian and co-workers at the State Key Laboratory of Biotherapy and Cancer Center and Tsinghua University in China have demonstrated that the combination of photothermal therapy and chemotherapy considerably inhibits the postoperative relapse of breast cancer They synthesized the hydrogel by heat-initiated free-radical polymerization The researchers found that applying near-infrared radiation simultaneously heated the gold nanorods and caused the thermoresponsive hydrogel to contract; this ‘squeezing’ of the hydrogel caused it to release the chemotherapy drug faster This combined approach has the advantage of reducing systemic toxicity since it limits non-selective application of the drug We prepared a hybrid hydrogel system by doping the gold nanorods (GNRs) into the thermal responsive hydrogel The near-infrared (NIR) laser was used to trigger the release of loaded Doxorubicin (DOX) by utilizing the photothermal effect of GNRs to induce the contraction of thermo-responsive hydrogels The development of the hydrogel as the carrier is for the chemo-photothermal co-therapy of local breast cancer recurrence The DOX-PCNA-GNRs hydrogel effectively prevented breast cancer recurrence after primary tumor resection in a mouse model
109 citations
TL;DR: Yan et al. as mentioned in this paper showed that the best performance was obtained at a size of 7.9 nanometers and the specific capacity dropped off rapidly due to the quantum confinement effect and slower charge and proton transfer.
Abstract: Nanosizing is the fashionable method to obtain a desirable electrode material for energy storage applications, and thus, a question arises: do smaller electrode materials exhibit better electrochemical performance? In this context, theoretical analyses on the particle size, band gap and conductivity of nano-electrode materials were performed; it was determined that a critical size exist between particle size and electrochemical performance. To verify this determination, for the first time, a scalable formation and disassociation of nickel-citrate complex approach was performed to synthesize ultra-small Ni(OH)2 nanoparticles with different average sizes (3.3, 3.7, 4.4, 6.0, 6.3, 7.9, 9.4, 10.0 and 12.2 nm). The best electrochemical performance was observed with a specific capacity of 406 C g−1, an excellent rate capability was achieved at a critical size of 7.9 nm and a rapid decrease in the specific capacity was observed when the particle size was <7.9 nm. This result is because of the quantum confinement effect, which decreased the electrical conductivity and the sluggish charge and proton transfer. The results presented here provide a new insight into the nanosize effect on the electrochemical performance to help design advanced energy storage devices. There is acritical size for nanoparticles that maximizes their electrochemical performance in energy storage devices, show a team in China. This finding goes against the conventional wisdom that smaller is better for the electrode material of such devices. Electrochemical energy storage devices such as batteries and supercapacitors are attractive power sources. One way to boost their performance has been to reduce the size of their electrode materials. Xingbin Yan and co-workers at the Lanzhou Institute of Chemical Physics prepared nine sets of Ni(OH)2 nanoparticles having various average sizes in the range 3.3 to 12.2 nanometers. They found that the best electrochemical performance was obtained at a size of 7.9 nanometers. Below that size, the specific capacity dropped off rapidly due to the quantum confinement effect and slower charge and proton transfer. Ultra-small Ni(OH)2 nanoparticles with different average sizes are prepared in large scale, and the best electrochemical performance is obtained at the critical size rather than the smallest size, which provides a new insight on nanosize effect on electrode materials in energy storage.
107 citations
TL;DR: In this article, a poly-adenine (polyA)-mediated approach was proposed to obtain mDNA-AuNPs with a nearly quantitative yield of similar to 90% using 80 As, as confirmed by both gel electrophoresis and transmission electron microscope observation.
Abstract: Monovalent DNA-gold nanoparticle (mDNA-AuNP) conjugates hold great promise for widespread applications, especially the construction of well-defined, molecule-like nanosystems. Previously reported methods all rely on the use of thiolated DNA to functionalize AuNPs, resulting in relatively low yields. Here, we report a facile method to rapidly prepare mDNA-AuNPs using a poly-adenine (polyA)-mediated approach. As polyA can selectively bind to AuNPs with high controllability of the surface density of DNA, we can use a DNA strand with a sufficiently long polyA to wrap around the surface of an individual AuNP, preventing further the adsorption of additional strands. Based on this observation, we obtained mDNA-AuNPs with a nearly quantitative yield of similar to 90% using 80 As, as confirmed by both gel electrophoresis and transmission electron microscope observation. The yields of mDNA-AuNPs were insensitive to the stoichiometric ratio between DNA and AuNPs, suggesting the click chemistry-like nature of this polyA-mediated reaction. mDNA-AuNPs exhibited rapid kinetics and high efficiency for sequence-specific hybridization. More importantly, we demonstrated that AuNPs of fixed valences could form well-defined heterogenous oligomeric nanostructures with precise, atom-like control.
TL;DR: In this article, a review of the recent achievements and the proposed strategy for addressing the emerging challenges in encapsulated noble metal nanocatalysts is presented, including the types of hybrid nanostructures and successful synthetic strategies.
Abstract: Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO2-encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area.
TL;DR: In this paper, the authors investigated the synergistic effect of one-dimensional nanofibrillated cellulose (NFC) and two-dimensional graphene oxide (GO) to facilitate low-cost, mechanically strong hybrid microfibers.
Abstract: High-performance microfibers such as carbon fibers are widely used in aircraft and wind turbine blades. Well-aligned, strong microfibers prepared by hybridizing two-dimensional (2D) graphene oxide (GO) nanosheets and one-dimensional (1D) nanofibrillated cellulose (NFC) fibers are designed here for the first time and have the potential to supersede carbon fibers due to their low cost. These well-aligned hybrid microfibers are much stronger than microfibers composed of 1D NFC or 2D GO alone. Both the experimental results and molecular dynamics simulations reveal the synergistic effect between GO and NFC: the bonding between neighboring GO nanosheets is enhanced by NFC because the introduction of NFC provides the extra bonding options available between the nanosheets. In addition, 1D NFC fibers can act as ‘lines’ to ‘weave and wrap’ 2D nanosheets together. A 2D GO nanosheet can also bridge several 1D NFC fibers together, providing extra bonding sites between 1D NFC fibers over a long distance. The design rule investigated in this study can be universally applied to other structure designs where a synergistic effect is preferred. Scientists in the US and China have produced strong microfibres by combining 2D graphene oxide nanosheets and 1D nanofibrillated cellulose. The low cost of production of these fibres could make them attractive for replacing carbon fibres, the researchers say. They produced these fibres by wet spinning a liquid-crystal solution of the nanosheets and the nanofibrillated cellulose, which were derived from wood cellulose. The hybrid fibres were much stronger than their components. Experimental results and molecular dynamic simulations reveal that this improved strength is due to a synergistic effect — bonding between adjacent graphene oxide nanosheets is enhanced by the nanofibrillated cellulose, while the nanofibrillated cellulose chains act like threads and bind the nanosheets together. The same synergistic effect could be exploited in other materials, the researchers note. For the first time, we investigate the synergistic effect of one-dimensional nanofibrillated cellulose (NFC) and two-dimensional graphene oxide (GO) to facilitate low-cost, mechanically strong hybrid microfibers. Both experimental and molecular dynamics simulations were carried out. Such GO-NFC hybrid microfibers show an elastic modulus of 34.1 GPa, an ultimate tensile strength of 442.4 MPa and a toughness of 4.9 MJ m−3, which outperform among the best GO fibers in literature. This study promotes a new design strategy to create high-performance microfibers for a range of applications.
TL;DR: In this paper, the authors describe fish-scale bio-inspired multifunctional ZnO nanostructures that have similar morphology and structure to the cycloid scales of the Asian Arowana.
Abstract: Scales provide optical disguise, low water drag and mechanical protection to fish, enabling them to survive catastrophic environmental disasters, predators and microorganisms. The unique structures and stacking sequences of fish scales inspired the fabrication of artificial nanostructures with salient optical, interfacial and mechanical properties. Herein, we describe fish-scale bio-inspired multifunctional ZnO nanostructures that have similar morphology and structure to the cycloid scales of the Asian Arowana. These nanostructured coatings feature tunable light refraction and reflection, modulated surface wettability and damage-tolerant mechanical properties. The salient properties of these multifunctional nanostructures are promising for applications in (i) optical coatings, sensing or lens arrays for use in reflective displays, packing, advertising and solar energy harvesting; (ii) self-cleaning surfaces, including anti-smudge, anti-fouling and anti-fogging, and self-sterilizing surfaces; and (iii) mechanical/chemical barrier coatings. This study provides a low-cost and large-scale production method for the facile fabrication of these bio-inspired nanostructures and provides new insights for the development of novel functional materials for use in 'smart' structures and applications.
TL;DR: By intercalating monolayer titania (TO) nanosheets into graphene oxide (GO) laminates with mild ultraviolet (UV) reduction, the as-prepared RGO/TO hybrid membranes exhibit excellent water desalination performances.
Abstract: By intercalating monolayer titania (TO) nanosheets into graphene oxide (GO) laminates with mild ultraviolet (UV) reduction, the as-prepared RGO/TO hybrid membranes exhibit excellent water desalination performances. Without external hydrostatic pressures, the ion permeations through the RGO/TO hybrid membranes can be reduced to <5% compared with the GO/TO cases, while the water transmembrane permeations, which are measured using an isotope-labeling technique, can be retained up to ~60%. The mechanism for the excellent water desalination performances of the RGO/TO hybrid laminates is discussed, which indicates that the photoreduction of GO by TO is responsible for the effective rejection of ions, while the photoinduced hydrophilic conversion of TO under UV irradiation is responsible for the well-retained water permeabilities. These excellent properties make RGO/TO hybrid membranes favorable for practical water desalination. Excellent water desalination has been achieved using hybrid laminates consisting of graphene oxide and titania. Researchers from Tsinghua University in China and the National Institute for Materials Science in Japan made these hybrid laminates using a simple vacuum filtration method that involves intercalating monolayer titania nanosheets in graphene oxide laminates while employing mild ultraviolet reduction. Employing an isotope labeling technique, they then investigated the water desalination properties of the hybrid laminates. The team ascribed the low ion flow through the hybrid membranes to the photoreduction of graphene oxide by titania, whereas they attributed the high water flow through the membranes to the hydrophilicity of titania, which was induced by ultraviolet irradiation. Such reduced graphene oxide/titania hybrid membranes are very promising for practical water desalination. By intercalating monolayer titania nanosheets (TO) into graphene oxide (GO) laminates, assisted with mild ultraviolet reduction, the as-prepared hybrid membranes exhibit excellent water desalination performances. The photoreduction of GO by TO is responsible for the effective rejection of ions, while the photoinduced hydrophilic conversion of TO is responsible for the well-retained water permeabilities.
TL;DR: In vitro as well as in vivo results suggest that this smart nanocomposite is promising as an NIR light-triggered and -targeted theranostic platform for imaging-guided PDT of cancer, which may provide a solution to the bottleneck problems of PDT, namely, limited penetration depth and oxygen-deficient microenvironment.
Abstract: Photodynamic therapy (PDT) is an excellent therapeutic modality for various malignant and nonmalignant cancers. This approach utilizes reactive oxygen species generated through the reaction between photosensitizer and oxygen in tissues upon light irradiation to achieve effective treatment. However, limited penetration depth and oxygen-deficient microenvironment hinder the efficiency of PDT. In this work, we design a multifunctional near-infrared (NIR)-triggered theranostic agent based on upconversion-nanoparticles-Polyoxyethylene bis (amine)-trismethylpyridylporphyrin-fullerene nanocomposite (UCNP-PEG-FA/PC70) for imaging (fluorescence/upconversion luminescence/magnetic resonance imaging)-guided photodynamic therapy. In this multimodal nanocompsite, UCNPs are employed as light transducers to convert NIR light into ultraviolet-visible light to activate PC70 to generate singlet oxygen (O-1(2)) even under low-oxygen conditions. Meanwhile, the upconversion emission, magnetic resonance imaging and fluorescence signal coming from UCNPs and PC70 nanocomposite enable UCNP-PEG-FA/PC70 to act as a multimodal imaging diagnostic agent, which facilitates the imaging-guided PDT. Furthermore, folate-mediated active targeting would enhance the accumulation of multifunctional hybrid in tumor. In vitro as well as in vivo results suggest that this smart nanocomposite is promising as an NIR light-triggered and -targeted theranostic platform for imaging-guided PDT of cancer, which may provide a solution to the bottleneck problems of PDT, namely, limited penetration depth and oxygen-deficient microenvironment.
TL;DR: Xiu et al. as discussed by the authors showed a gate-induced transition from band conduction to hopping conduction in single-crystalline Cd3As2 thin films via electrostatic doping by solid electrolyte gating.
Abstract: Electrostatic doping in materials can lead to various exciting electronic properties, such as metal–insulator transition and superconductivity, by altering the Fermi level position or introducing exotic phases. Cd3As2, a three-dimensional (3D) analog of graphene with extraordinary carrier mobility, was predicted to be a 3D Dirac semimetal, a feature confirmed by recent experiments. However, most research so far has been focused on metallic bulk materials that are known to possess ultra-high mobility and giant magneto-resistance but limited carrier transport tunability. Here we report on the first observation of a gate-induced transition from band conduction to hopping conduction in single-crystalline Cd3As2 thin films via electrostatic doping by solid electrolyte gating. The extreme charge doping enables the unexpected observation of p-type conductivity in a ∼50-nm-thick Cd3As2 thin film grown by molecular beam epitaxy. More importantly, the gate-tunable Shubnikov–de Haas oscillations and the temperature-dependent resistance reveal a unique band structure and bandgap opening when the dimensionality of Cd3As2 is reduced. This is also confirmed by our first-principle calculations. The present results offer new insights toward nanoelectronic and optoelectronic applications of Dirac semimetals in general and provide new routes in the search for the intriguing quantum spin Hall effect in low-dimension Dirac semimetals, an effect that is theoretically predicted but not yet experimentally realized. The tunable quantum transport capabilities of cadmium arsenide thin films may unlock new applications for graphene-like semiconductors. Cadmium arsenide has similar electronic properties to graphene, but is easier to work with thanks to its three-dimensional crystal structure. Faxian Xiu of Fudan University in Shanghai and co-workers have now mapped out this material's band structure in confined 50-nanometre-thin film structures. By using a source-drain layout with an unconventional gate electrode — a droplet of ionic electrolyte that electrostatically dopes cadmium arsenide and changes its Fermi level — they saw remarkable conductivity switching behaviour, which is useful for ambipolar field effect transistors. Applying magnetic fields during device operation also revealed the possibility of generating quantum spin Hall effects — the team observed intriguing quantum oscillation conductivity when the Fermi level was pushed into the high-mobility conduction band. Cd3As2, which is known as a topological Dirac semimetal, has been grown on mica substrates by molecular beam epitaxy with high mobility. The temperature-dependent resistance of as-grown Cd3As2 thin films showed semiconducting behavior, indicating the band gap opening as opposed to the bulk counterpart. By solid electrolyte gating, the ambipolar effect and gate-tunable quantum oscillations were clearly demonstrated. These features make the Cd3As2 thin film system a promising platform to observe various exotic phenomena and realize new electronic applications.
TL;DR: Wang et al. as mentioned in this paper reported a bulk hybrid nanostructured Al alloy with high strength at both room temperature and elevated temperatures, and attributed the strengthening mechanism to the composite effect of the high-strength nanocrystalline fcc-Al and nano-sized intermetallics as well as to the confinement effect between these nano phases.
Abstract: Methods to strengthen aluminum alloys have been employed since the discovery of the age-hardening phenomenon in 1901. The upper strength limit of bulk Al alloys is ~0.7 GPa by conventional precipitation strengthening and increases to >1 GPa through grain refinement and amorphization. Here we report a bulk hybrid nanostructured Al alloy with high strength at both room temperature and elevated temperatures. In addition, based on high-resolution transmission electron microscopic observations and theoretical analysis, we attribute the strengthening mechanism to the composite effect of the high-strength nanocrystalline fcc-Al and nano-sized intermetallics as well as to the confinement effect between these nano phases. We also report the plastic deformation of nano-sized intermetallics and the occurrence of a high density of stacking faults and twins in fcc-Al after low-strain-rate deformation at room and high temperatures. Our findings may be beneficial for designing high-strength materials for advanced structural applications. An international team of scientists create an aluminum alloy that is twice as strong as those made by conventional techniques. Zhi Wang from IFW Dresden in Germany and Tohoku University in Japan and co-workers from China, Germany, Japan and Austria have developed a technique that allows the microstructure of aluminum alloys to be carefully controlled, enabling them to create hybrid structures consisting of nanoscale intermetallic compounds in an aluminum matrix. Previous attempts to create strong alloys included making an aluminum-based material that is non-crystalline, like glass, or one that is made up of crystalline nanograins. But these approaches lead to materials that are unsuitable for use at high temperatures. In contrast, the aluminum alloy created by the researchers exhibits high strength at both ambient and elevated temperatures. We report a bulk hybrid nanostructured Al alloy with super-high strength at both room and elevated temperatures. The strengthening mechanisms were clearly elucidated, which are mainly attributed to the composite structure and confinement effect between the nano phases. The confining effect can effectively suppress the premature brittle fracture of the nano-intermetallic phases. The microstructural strategy and strengthening mechanisms in this work may be beneficial for the scientific community in understanding and designing high-strength materials.
TL;DR: This work presents a wirelessly operated, implantable drug delivery system that offers such capabilities in a form that undergoes complete bioresorption after an engineered functional period, thereby obviating the need for surgical extraction.
Abstract: On-demand, localized release of drugs in precisely controlled, patient-specific time sequences represents an ideal scenario for pharmacological treatment of various forms of hormone imbalances, malignant cancers, osteoporosis, diabetic conditions and others. We present a wirelessly operated, implantable drug delivery system that offers such capabilities in a form that undergoes complete bioresorption after an engineered functional period, thereby obviating the need for surgical extraction. The device architecture combines thermally actuated lipid membranes embedded with multiple types of drugs, configured in spatial arrays and co-located with individually addressable, wireless elements for Joule heating. The result provides the ability for externally triggered, precision dosage of drugs with high levels of control and negligible unwanted leakage, all without the need for surgical removal. In vitro and in vivo investigations reveal all of the underlying operational and materials aspects, as well as the basic efficacy and biocompatibility of these systems.
TL;DR: In this paper, a 5.5mm-long normal mode helical antenna operating in the industry-scientific-medical radio bands at 5.8 and 2.4 GHz was developed for use in smart medical implants.
Abstract: Smart implants are envisioned to revolutionize personal health care by assessing physiological processes, for example, upon wound healing, and communicating these data to a patient or medical doctor. The compactness of the implants is crucial to minimize discomfort during and after implantation. The key challenge in realizing small-sized smart implants is high-volume cost- and time-efficient fabrication of a compact but efficient antenna, which is impedance matched to 50 Ω, as imposed by the requirements of modern electronics. Here, we propose a novel route to realize arrays of 5.5-mm-long normal mode helical antennas operating in the industry-scientific-medical radio bands at 5.8 and 2.4 GHz, relying on a self-assembly process that enables large-scale high-yield fabrication of devices. We demonstrate the transmission and receiving signals between helical antennas and the communication between an antenna and a smartphone. Furthermore, we successfully access the response of an antenna embedded in a tooth, mimicking a dental implant. With a diameter of ~0.2 mm, these antennas are readily implantable using standard medical syringes, highlighting their suitability for in-body implant applications. Helical antennas that are just 5.5 millimetres long have been developed for use in smart medical implants by scientists in Germany. Smart implants are set to transform personal health care by monitoring physiological processes and relaying data to medical workers. It is critical for such implants to be compact, but miniaturizing antenna has proved challenging. Now, researchers based in Dresden have applied strain engineering to polymer–metal heterostructures to achieve large scale high yield fabrication of compact helical antennas that are about five times smaller than conventional two-dimensional dipole antennas. They demonstrate transmission and reception of signals between a pair of antennas as well as between an antenna and smartphone. They also show that the antenna can be addressed when embedded in a tooth model. The small size of the antennas permits them to be implanted using standard medical syringes. We fabricated compact helical antenna operating in the industry-scientific-medical radio band. With a total length of only 5.5 mm, it is about five times smaller compared with the conventional dipole antenna. The transmission and receiving signals between helical antennas and the communication between a helical antenna and a smartphone is reported. Owing to the shape and dimensions, we successfully demonstrate the possibility to address the antenna, when embedded in a tooth, as well as to implant the antenna using standard medical syringes. These demonstrations highlight the potential of helical antennas for medical applications as components of smart system implants.
TL;DR: Chi et al. as mentioned in this paper reviewed recent advances in advanced analytical electron microscopy (AEM) and their implications for studying lithium-ion batteries and demonstrated how such methods have created unrivaled opportunities for understanding the working mechanisms of battery materials.
Abstract: Recent advances in advanced analytical electron microscopy (AEM) and their implications for studying lithium-ion batteries are reviewed Lithium-ion batteries are promising for powering electric vehicles and for use in smart grid applications, but require further optimization before they can achieve widespread use in these applications Powerful advanced AEM techniques are ideal for gaining unprecedented insight into the dynamic processes of active lithium-ion batteries Miaofang Chi, a research scientist at Oak Ridge National Laboratory, and her co-workers overview recent developments in novel AEM capabilities and demonstrate how such methods have created unrivaled opportunities for understanding the working mechanisms of battery materials Both static, ex situ studies and newly developed in situ AEM techniques, which offer the opportunity to explore dynamic electrochemical processes during charging and discharging, are highlighted The scientists also propose future directions
TL;DR: Wallace et al. as discussed by the authors reviewed a wide range of scalable chemistries that potentially could be used to produce processable Graphene, including aqueous and organic solvents, and discussed the differences between natural and synthetic graphite, the necessary steps for converting them into graphene and how graphene can be used for producing composites.
Abstract: There now exists a wide range of scalable chemistries that potentially could be used to produce processable graphene. Graphene holds a lot of promise, but before it can be used commercially, methods are needed for producing processable forms of graphene in scalable amounts and also for incorporating graphene in devices. Gordon Wallace and co-workers at the ARC Centre of Excellence for Electromaterials Science, University of Wollongong in Australia comprehensively review the various chemistries available for chemically converting graphite into graphene. In particular, they consider suitable chemistries for developing graphene dispersions in aqueous and organic solvents and their use for preparing various polymer composites, which can be used to fabricate graphene-based structures and devices. They discuss the differences between natural and synthetic graphite, the necessary steps for converting them into graphene and how graphene can be used to produce composites.
TL;DR: Sun et al. as discussed by the authors demonstrate a highly active and stable Pt nanoparticle/Mo2C nanotube catalyst for methanol electro-oxidation using a controllable atomic layer deposition (ALD) technique.
Abstract: Poor electrocatalytic activity and carbon monoxide (CO) poisoning of the anode in Pt-based catalysts are still two major challenges facing direct methanol fuel cells. Herein, we demonstrate a highly active and stable Pt nanoparticle/Mo2C nanotube catalyst for methanol electro-oxidation. Pt nanoparticles were deposited on Mo2C nanotubes using a controllable atomic layer deposition (ALD) technique. This catalyst showed much higher catalytic activity for methanol oxidation and superior CO tolerance, when compared with those of the conventional Pt/C and PtRu/C catalysts. The experimental evidence from X-ray absorption near-edge structure spectroscopy and scanning transmission X-ray microscopy clearly support a strong chemical interaction between the Pt nanoparticles and Mo2C nanotubes. Our studies show that the existence of Mo2C not only minimizes the required Pt usage but also significantly enhances CO tolerance and thus improves their durability. These results provide a promising strategy for the design of highly active next-generation catalysts. Platinum nanoparticles on Mo2C nanotubesact as a stable, highly active catalyst for methanol electro-oxidation, find a binational team led by Chunwen Sun from Institute of Physics, Chinese Academy of Sciences. Methanol electro-oxidation is a critical reaction in direct methanol fuel cells, but conventional methods for catalysing it using Pt-based catalysts loaded on carbon suffer from low activities and CO poisoning of the anode. Now, researchers in China and Canada have discovered that a catalyst produced by depositing Pt nanoparticles on Mo2C nanotubes by controlled atomic layer deposition can overcome both problems. Based on X-ray spectroscopy and microscopy measurements, they attribute this to synergistic effects between the two components. Their results reveal that the presence of Mo2C both reduces the amount of Pt needed (thus lowering costs) and enhances CO tolerance (thereby improving durability), indicating that it is a promising strategy for designing highly active next-generation catalysts. In this paper, we demonstrate a highly active and stable Pt nanoparticle/Mo2C nanotube catalyst for methanol electro-oxidation. Well-dispersed Pt nanoparticles were deposited on Mo2C nanotubes using a controllable atomic layer deposition (ALD) technique. This catalyst showed much higher catalytic activity for methanol oxidation and superior CO tolerance, when compared with those of the conventional Pt/C and PtRu/C catalysts. These results provide a promising strategy for the design of highly active next-generation catalysts.
TL;DR: Wu et al. as discussed by the authors synthesized n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate.
Abstract: Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm−1, 1.55 V μm−1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. Spiky silicon carbide (SiC) ‘nanoneedles’ can improve light emission from e-paper and other bendable electronic devices. Flexible field-emission displays are an emerging technology in which tiny conductive tips grown on lightweight, rollable surfaces generate intense light. Significant manufacturing- and materials-related obstacles, however, have limited their application. Now, a team led by Tom Wu from King Abdullah University of Science and Technology in Saudi Arabia and Weiyou Yang from Ningbo University of Technology in China investigated how SiC — a compound with notable stiffness and stablity — performed as a field emitter by catalytically synthesising this material into nanoscale needles with ultrasharp tips and controllable doping levels on a carbon fabric surface. Their experiments showed that the SiC nanoneedles had low ‘turn-on’ field requirements and minimal emission fluctuations even after repeated bending cycles, thanks to their impressive mechanical robustness. We demonstrated for the first time highly flexible N-doped SiC nanoneedle field emitters with low turn-on fields and excellent emission stabilities. The characterizations of their field emission properties under repeated bending cycles and different bending states confirmed that such emitters are mechanically and electrically robust. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications.
TL;DR: In this paper, the polyallylamine-functionalized PdPt@PtPd CSNDs were synthesized by using PAH that serves as a complexant, reductant and chemical functionalization molecule.
Abstract: Pt-based bimetallic nanostructures have found intriguing applications in electrocatalysis. However, the pristine Pt-based nanostructures generally lack the selectivity for the target reaction because of their high activity for both oxygen reduction reactions (ORRs) and fuel molecule oxidation reactions. By employing a recently developed chemical functionalization strategy, the functionalized Pt-based nanostructures have achieved their selectivity for the target reaction in fuel cells. In this work, we report a facile thermal decomposition route to synthesize the polyallylamine (PAH)-functionalized Pd–Pt bimetallic core–shell nanodendrites with a Pd-rich PdPt alloy core and a Pt-rich PtPd alloy shell (PdPt@PtPd CSNDs) by using PAH that serves as a complexant, reductant and chemical functionalization molecule. The composition, morphology and structure of PdPt@PtPd CSNDs are characterized in detail. Compared with commercial Pt black electrocatalyst, the PAH-functionalized PdPt@PtPd CSNDs show improved electrocatalytic activity and durability for the ORR, and achieve good selectivity for the ORR in the presence of ethanol molecules. The study shows a promising cathode electrocatalyst for direct alcohol fuel cells (DAFCs). Palladium–platinum core–shell nanodendrites have been made that are promising as a cathode electrocatalyst for direct alcohol fuel cells. Such fuel cells convert the chemical energy of alcohol into electricity and are attractive for powering vehicles and portable electronic devices. To become commercially viable, it is vital to improve the efficiency, activity, alcohol tolerance and durability of platinum electrocatalysts for the oxygen reduction reaction (ORR). Now, researchers in Singapore and China have demonstrated a simple one-step approach involving water-based thermal decomposition for synthesizing polyallylamine-functionalized palladium–platinum nanodendrites that have palladium-rich cores and platinum-rich shells. These bimetallic nanostructures exhibited superior electrocatalytic activity and durability for the ORR than a commercial platinum black electrocatalyst. Importantly, unlike pristine platinum-based nanostructures, they showed good selectivity for the ORR in the presence of ethanol. The polyallylamine functionalization imparted Pd–Pt nanodendrites with extraordinary selectivity for the oxygen reduction reaction because of its steric hindrance effect and ethanol-phobic property.
TL;DR: In this paper, strongly coupled Cu2O@CeO2 core@shell nanostructures have been successfully prepared via a non-organic and clean aqueous route without using any organic additive.
Abstract: The fabrication of multi-component hybrid nanostructures is of vital importance because their two-phase interface could provide a rich environment for redox reactions, which are beneficial for enhancing catalytic performance. Inspired by the above consideration, strongly coupled Cu2O@CeO2 core@shell nanostructures have been successfully prepared via a non-organic and clean aqueous route without using any organic additive. In this process, an auto-catalytic redox reaction occurred on the two-phase interface, followed by a triggered self-assembly process. Additionally, the size, morphology and composition of the as-obtained nanostructures can be tuned well by varying the reaction temperature, as well as the species and the amount of Cu precursors. The catalytic tests for peroxidase-like activity and CO oxidation have been conducted in detail, and the results confirm a strong synergistic effect at the interface sites between the CeO2 and Cu2O components.
TL;DR: In this paper, a reversible electric-field-driven out-of-plane to in-plane magnetization switching in Cu/Ni multilayers on ferroelectric BaTiO3 at room temperature was demonstrated.
Abstract: Perpendicularly magnetized layers are used widely for high-density information storage in magnetic hard disk drives and nonvolatile magnetic random access memories. Writing and erasing of information in these devices is implemented by magnetization switching in local magnetic fields or via intense pulses of electric current. Improvements in energy efficiency could be obtained when the reorientation of perpendicular magnetization is controlled by an electric field. Here, we report on reversible electric-field-driven out-of-plane to in-plane magnetization switching in Cu/Ni multilayers on ferroelectric BaTiO3 at room temperature. Fully deterministic magnetic switching in this hybrid material system is based on efficient strain transfer from ferroelastic domains in BaTiO3 and the high sensitivity of perpendicular magnetic anisotropy in Cu/Ni to electric-field-induced strain modulations. We also demonstrate that the magnetoelectric coupling effect can be used to realize 180° magnetization reversal if the out-of-plane symmetry of magnetic anisotropy is temporarily broken by a small magnetic field. An electric-field switching technique can lower the energy required to write and erase data in high-density magnetic storage devices. Perpendicularly magnetic recording is a new technology that aligns magnetic bits into vertical arrangements using specially constructed multilayer films. Normally, magnetic fields or intense bursts of electric currents are needed to modify individual bits. Tomoyasu Taniyama from the Tokyo Institute of Technology and international collaborators have discovered that growing perpendicularly magnetised copper-nickel multilayers on top of ferroelectric BaTiO3 crystals produces devices responsive to modest electric fields. Laser-based measurements and theoretical analysis revealed that this fast, reversible, and room temperature data switching method was driven by mechanical strain at the metal multilayer-ferroelectric interface. Successful results with films up to 65 nanometers thick indicate that this approach holds promise for practical spintronics applications. Reversible electric-field-driven magnetization switching between perpendicular-to-plane and in-plane orientations in Cu/Ni multilayers on ferroelectric BaTiO3 is demonstrated at room temperature. Fully deterministic magnetic switching is based on efficient strain transfer from ferroelastic domains in BaTiO3 and the high sensitivity of perpendicular magnetic anisotropy in Cu/Ni to electric-field-induced strain modulations. The magnetoelectric coupling effect can also be used to realize 180° magnetization reversal if the out-of-plane symmetry of magnetic anisotropy is temporarily broken by a small magnetic field.
TL;DR: In this article, a giant two-dimensional (2D) piezoelectric effect on an intrinsic graphene-based NEMS platform, which results from dynamical adjustment of band structure-induced polarization instead of occurrence of electric dipoles at the molecular level, is reported.
Abstract: Graphene is an emerging material for nanoelectromechanical systems (NEMS) due to its intriguing electronic properties and promising mechanical character. However, intrinsic graphene has long been considered devoid of piezoelectric effect which restricts its electromechanical coupling ability. We report on a giant two-dimensional (2D) piezoelectric effect on an intrinsic graphene-based NEMS platform, which results from dynamical adjustment of band structure-induced polarization instead of occurrence of electric dipoles at the molecular level. These findings not only open an avenue for dynamical strain-engineered 2D electronics, but also pave the way for low-cost sensing and energy harvesting applications.
TL;DR: Yang et al. as discussed by the authors demonstrate a one-step approach toward the large-scale fabrication of robust super-hydrophobic coatings using strawberry-like hemispherical Janus particles.
Abstract: We demonstrate a one-step approach toward the large-scale fabrication of robust superhydrophobic coatings using strawberry-like hemispherical Janus particles. Hemispherical Janus particles are capable of self-organizing into a layer on substrates. Nanoscale roughness on the hydrophobic hemispherical side determines the superhydrophobic performance. The imidazolin group on the hydrophilic flat side determines the coating strength by covalent binding onto substrates via cations initiating the crosslinking of the intermediate epoxy resins. The coating can tolerate organic solvents and high water flushing speeds. If the hydrophobic side is smooth, then the coating is highly adhesive to water. This procedure can fabricate unique coatings on a diverse range of substrates with varied compositions and shapes. A new coating made from self-assembling, strawberry-shaped Janus nanoparticles can turn ordinary surfaces into ultra-water-repellent materials. This first finding by Zhenzhong Yang and colleagues at the Chinese Academy of Sciences involves using a sol-gel process to synthesize tiny silica shells with ‘Janus’, or two-faced properties. Thanks to the presence of special surfactants, one side of the nanoparticle forms a curved, bumpy surface resembling that of a strawberry, whereas the other side is flat. The team modified the flat, hydrophilic surface with a reactive precursor and then sprayed an aqueous dispersion of the particles onto an epoxy-coated glass sheet. Water evaporation caused the flat silica side to covalently anchor to the epoxy, exposing a uniform coating of superhydrophobic bumps. These coatings are attractive because they are remarkably robust and could be applied to complex substrates at industrially relevant scales. Schematic synthesis of the robust superhydrophobic coating from strawberry-like Janus hemispherical particles: (a) the dispersion of aqueous particles is sprayed onto the E-51 layer on the substrate; (b) the Janus particles self-orientate to form a layer; and (c) after the epoxy resin is cured by cationic catalysis, the robust superhydrophobic coating is fabricated.
TL;DR: In this article, the performance of polyhedral gold nanocrystals with high-index facets was investigated for the purpose of improving the catalytic performance of Li-O2 batteries.
Abstract: Cathode catalysts are the key factor in improving the electrochemical performance of lithium–oxygen (Li–O2) batteries via their promotion of the oxygen reduction and oxygen evolution reactions (ORR and OER). Generally, the catalytic performance of nanocrystals (NCs) toward ORR and OER depends on both composition and shape. Herein, we report the synthesis of polyhedral Au NCs enclosed by a variety of index facets: cubic gold (Au) NCs enclosed by {100} facets; truncated octahedral Au NCs enclosed by {100} and {110} facets; and trisoctahedral (TOH) Au NCs enclosed by 24 high-index {441} facets, as effective cathode catalysts for Li–O2 batteries. All Au NCs can significantly reduce the charge potential and have high reversible capacities. In particular, TOH Au NC catalysts demonstrated the lowest charge-discharge overpotential and the highest capacity of ~20 298 mA h g−1. The correlation between the different Au NC crystal planes and their electrochemical catalytic performances was revealed: high-index facets exhibit much higher catalytic activity than the low-index planes, as the high-index planes have a high surface energy because of their large density of atomic steps, ledges and kinks, which can provide a high density of reactive sites for catalytic reactions. Gold nanocrystals with high-index facets improve the electrochemical performance of lithium–oxygen batteries, find scientists in Australia. The high energy densities of lithium–oxygen batteries make them attractive for powering electric vehicles. The researchers investigated three differently shaped gold nanocrystals — cubic, truncated octahedral and trisoctahedral nanocrystals — for their effectiveness as cathode catalysts for lithium–oxygen batteries. They found that all three nanocrystals significantly reduced the charge potential while possessing high reversible capacities. Furthermore, the trisoctahedral nanocrystals, which have the highest index facets among three nanocrystals, exhibited the lowest charge–discharge overpotential and highest capacity. The researchers attribute the improved catalytic performance of crystals with high-index facets to higher index planes having greater surface energies resulting from the large density of atomic steps, ledges and kinks, which act as reactive sites for catalytic reactions. Polyhedral Au nanocrystals enclosed by a variety of index facets are prepared: cubic Au NCs enclosed by {100} facets; truncated octahedral Au NCs enclosed by {100} and {110} facets; and trisoctahedral Au NCs enclosed by 24 high-index {441} facets. It is found that high index facets exhibit much higher catalytic activity toward oxygen reduction and oxygen evolution reactions in Li–O2 batteries.