The influence of water permeates almost all areas including biochemistry,chemistry,physics and is particularly evident in phenomena occurring at the interfaces of solid surface such as SiC nanocrystals,which are promising nanomaterials and exhibit unique surface chemical properties.In this paper,the quantum confinement effect and stability of 3C-SiC nanocrystals in aqueous solution as well as photoluminescence properties in water suspensions with different pH values are reviewed based on design and analysis of surface structures.On this basis,the significant progress of 3C-SiC nanocrystals in efficiently splitting water into usable hydrogen is summarized and the relative mechanisms are described.In addition,the water-soluble 3C-SiC quantum dots as robust and nontoxic biological probes and labels also are introduced as well as future prospects given.
Due to a large surface-to-volume ratio, the optoelectronic performance of low- dimensional semiconductor nanostructure-based photodetectors depends in principle on chemisorption/photodesorption at the exposed surface, but practical examples that show such an effect are still unavailable. Some theoretical calculations have predicted that the {001} facets of In2O3 can effectively accumulate photogenerated holes under irradiation, providing a model material to examine whether the facet cutting of nanowires （NWs） can boost their optoelectronic performance. Herein, we present the design and construction of a novel nanowire-based photodetector using square In2O3 NWs with four exposed {001} crystal facets. The photodetector delivers excellent optoelectronic performance with excellent repeatability, fast response speed, high spectral responsivity （Rλ）, and high external quantum efficiency （EQE）. The Rλ and EQE values are as high as 4.8 × 10^6 A/W and 1.46 × 10^9%, respectively, which are larger than those of other popular semiconductor photodetectors. In addition, the square In2O3 NWs show hydrophobic wettability as manifested by a contact angle of 118° and a fast photoinduced reversible switching behavior is observed.
Ming MengXinglong WuXiaoli JiZhixing GanLizhe LiuJiancang ShenPaul K. Chu
Ferromagnetism is investigated in high-quality Cu-doped A1 N single crystal whiskers.The whiskers exhibit roomtemperature ferromagnetism with a magnetic moment close to the results from first-principles calculations.High crystallinity and low Cu concentrations are found to be indispensable for high magnetic moments.The difference between the experimental and theoretical moment values is explored in terms of the influence of nitrogen vacancies.The calculated results demonstrate that nitrogen vacancies can reduce the magnetic moments of Cu atom.
A cost-effective carbon-free nanocoating strategy was developed for the synthesis of ultra-fine SnO2 coatingα-Fe2O3 core-shell nanoparticles. This strategy only involves a two-step molten salt reaction at low temperature of 300 °C. The as-preparedα-Fe2O3@SnO2 core-shell nanocomposites show enhanced electrochemical performances than the bareα-Fe2O3 nanoparticles. This involved metal oxide nanocoating method is easy to be carried out, and the heat treatment temperature is much lower than that of other traditional solid-state annealing method and many carbon or metal oxide nanocoating methods. The molten salt method may also be used to produce other metal oxides coating nanostructures as the electrode materials for lithium-ion batteries.
Core-shell nanostructures have attracted considerable attention in the past decades because of their fundamental scientific significance and many technological applications.Recently,it has been reported that the core-shell nanostructures with advanced compositions and complicated morphologies show great potential as high-performance microwave absorbers due to their unique properties,such as large surface areas,multi-functionalities and synergistic effects between the interior core and outer shell.This review article focuses on the recent progress in synthesis and characterization of hierarchical magnetic core-shell nanostructures for microwave absorption applications based on our own work.In addition,several future trends in this field for next-generation microwave absorbers are discussed.
LIU JiWeiXU JunJieLIU ZhengWangLIU XiaLinCHE RenChao
Threaded aluminum nitride （A1N） whiskers are grown by a physical vapor transport method in a radio-frequency induction heating furnace. The resultant whiskers are characterized by X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy and photoluminescence. The analysis shows that the whiskers are single-crystalline, wurtzite AIN. The threaded A1N whiskers are 0.5 μm^100 μm in diameter and several millimeters in length in the fiber direction, and have lots of tiny sawteeth on the surface. The morphology of this threaded A1N whisker is beneficial for bonding when the whisker is used in composite. The growth of the whiskers is dominated by the vapor-solid （VS） mechanism, and the particular morphology might result from an oscillating condition produced in the radio-frequency induction heating furnace.
The photoluminescence （PL） characteristics of hybrid β-FeSi2/Si and pure β-FeSi2 films fabricated by pulsed laser deposition at 20 K are investigated. The intensity of the 1.54-μm PL from the former is enhanced, but the enhancement vanishes when the excitation wavelength is larger than the widened band gap of Si nanocrystal. Time-resolved PL decay measurements reveal that the lifetime of the photo-excited carriers in the hybrid β-FeSi2/Si film is longer than that in the pure β-FeSi2 film, providing evidence that the PL enhancement results from the resonant charge transfer from nanocrystalline Si to β-FeSi2.
