Analysis of the Response Characteristics of Toluene Gas Sensors with a ZnO Nanorod Structure by a Heat Treatment Process.

The sensing characteristics of toluene gas are monitored by fabricating ZnO nanorod structures. ZnO nanostructured sensor materials are produced on a Zn film via an ultrasonic process in a 0.01 M aqueous solution of C6H12N4 and Zn(NO3)2∙6H2O. The response of the sensors subjected to heat treatment in oxygen and nitrogen atmospheres is improved by 20% and 10%, respectively. The improvement is considered to be correlated with the increase in grain size. The relationship between the heat treatment and sensing characteristics is evaluated.

Fabrication of Au/graphene-wrapped ZnO-nanoparticle-assembled hollow spheres with effective photoinduced charge transfer for photocatalysis.

Heterostructures of gold-nanoparticle-decorated reduced-graphene-oxide (rGO)-wrapped ZnO hollow spheres (Au/rGO/ZnO) are synthesized using tetra-n-butylammonium bromide as a mediating agent. The structure of amorphous ZnO hollow spheres is found to be transformed from nanosheet- to nanoparticle-assembled hollow spheres (nPAHS) upon annealing at 500 °C. The ZnO nPAHS hybrids with Au/rGO are characterized using various techniques, including photoluminescence, steady-state absorbance, time-resolved photoluminescence, and photocatalysis. The charge-transfer time of ZnO nPAHS is found to be 87 ps, which is much shorter than that of a nanorod (128 ps), nanoparticle (150 ps), and nanowall (990 ps) due to its unique structure. The Au/rGO/ZnO hybrid shows a higher charge-transfer efficiency of 68.0% in comparison with rGO/ZnO (40.3%) and previously reported ZnO hybrids. The photocatalytic activities of the samples are evaluated by photodegrading methylene blue under black-light irradiation. The Au/rGO/ZnO exhibits excellent photocatalytic efficiency due to reduced electron-hole recombination, fast electron-transfer rate, and high charge-transfer efficiency.

Photoluminescence Properties and Photocatalytic Performance of Different Size ZnO Nanoparticles Decorated Graphene Oxide.

We synthesized the hybrid structure of the graphene oxide (GO) sheet and the size-controlled ZnO nanoparticles. The ZnO quantum sizes were confirmed from UV-vis spectrophotometry and TEM results. The ZnO quantum dot exhibited a stable broad and strong photoluminescence (PL) emission which is broader with the increase of ZnO nanoparticle size. The hybrid ZnO/GO results an abrupt decrease of PL emission and the excellent photodegradation performance of methylene blue under UV-light irradiation. A considerable increase of the photodegradation rate with decreasing ZnO nanoparticle size is due to the enhancement of ZnO surface interaction and the improvement of electron transfer at the ZnO/GO interface.

Photocatalytic activity of metal-inserted WO3 thin films prepared by RF magnetron sputtering.

Metal (Au,Pt)-inserted WO3 thin films were deposited on quartz glass using a radio frequency magnetron sputtering method. Their structural and optical properties were analyzed by scanning electron microscopy, X-ray diffractometry, absorption spectrometry, and photoluminescence spectrometry. The photocatalytic activities of the films were investigated by the measurement of photodecomposition of methylene blue under visible-ray irradiation. Metal-inserted WO3 films showed higher photocatalytic activity than WO3 film. Pt-inserted WO3 thin film showed the most effective decomposition efficiency, it is due to the high absorption and the suppression of recombination between photo-excited electrons and holes.

Controlling ferromagnetic easy axis in a layered MoS2 single crystal.

We report the effective methods to induce weak ferromagnetism in pristine MoS2 persisting up to room temperature with the improved transport property, which would lead to new spintronics devices. The hydrogenation of MoS2 by heating at 300 °C for 1 h leads to the easy axis out of plane, while the irradiation of proton with a dose of 1 × 10(13) P/cm(2) leads to the easy axis in plane. The theoretical modeling supports such magnetic easy axes.