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1. chinaXiv:201710.00078 [pdf]

Laser irradiation-induced Au-ZnO nanospheres with enhanced sensitivity and stability in ethanol sensing.pdf

Hao Zhang; Shouliang Wu; Jun Liu; Yunyu Cai; Changhao Liang
Subjects: Materials Science >> Materials Chemistry

Incorporating noble metal nanoparticles on the surface or inner side of semiconductors to form a hybrid nanostructure is an effective route to improve the gas sensing performance of these semiconductors. In this study, we present novel Au-decorated ZnO nanospheres (Au-ZnO NSs) obtained by laser irradiation of liquids. Structural characterization indicated that the Au-ZnO NSs consisted of single crystalline ZnO NSs with few Au nanoparticles decorated on their surfaces and abundant encapsulated Au nanoparticles with relatively small sizes. Laser irradiation-induced heating–melting–evaporating processes are responsible for the formation of unique Au-ZnO NSs. Gas sensing properties of the Au-ZnO NSs, as gas sensing materials, were investigated and compared with those of pure ZnO NSs. The former showed lower working temperature, higher sensitivity, better selectivity, and good reproducibility. The response values of Au-ZnO NSs and pure ZnO NSs sensors to ethanol of 100 ppm were 252 and 75 at working temperature of 320 °C and 360 °C, respectively. The significant enhancements in gas sensing performance should be attributed to the electronic sensitization induced by the depleted layers between encapsulated Au nanoparticles and ZnO and chemical sensitization originating from the catalytic effects of Au nanoparticles decorated on the surfaces that dissociated molecular oxygen.

submitted time 2017-10-31 Hits15951Downloads1385 Comment 0

2. chinaXiv:201609.01013 [pdf]

Perturbativity Limits for Scalar Minimal Dark Matter with Yukawa Interactions: Septuplet

Chengfeng Cai; Ze-Min Huang; Zhaofeng Kang; Zhao-Huan Yu; Hong-Hao Zhang
Subjects: Physics >> Nuclear Physics

The candidate of minimal dark matter (MDM) is limited if one demands perturbativity up to a very high scale, and it was believed that the MDM model with a real scalar septuplet could keep perturbative up to the Planck or GUT scale. In this work we point out that it is not true after taking into account the running of the quartic self-couplings of the scalar septuplet. For the septuplet mass around?10?TeV, which is suggested by the observed dark matter relic abundance, these couplings would hit the Landau pole at a scale??108?109?GeV, much lower than the Planck scale. We attempt to push up the Landau pole scale as high as possible by proposing an extension with extra Yukawa interactions of the septuplet. We find that in principle the Landau pole could be deferred to a scale of??1014?GeV if one could tolerate a serious fine-tuning of the initial condition of the Yukawa coupling. Moreover, if the MDM particle mass could be relaxed to??108?GeV, which would need some nonthermal production mechanisms to give a correct relic abundance, the Landau pole scale could be pushed up above the Planck scale.

submitted time 2016-09-14 Hits1067Downloads618 Comment 0

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