ZnO纳米棒的制备及光催化性能研究

采用水热法制备ZnO纳米棒。利用X射线粉末衍射(XRD)仪和透射电镜(TEM)对其结构和形貌分别进行表征,并通过紫外-可见分光光度计分析ZnO纳米棒光降解甲基紫来研究其光催化活性。结果表明,以氢氧化钠和醋酸锌为原料,聚丙烯酰胺为表面活性剂制备得到直径约26nm,长度达400nm的单晶纤锌矿结构的ZnO纳米棒。添加ZnO纳米棒光催化剂时的光降解率为70%,未加ZnO纳米棒的光降解率为30%,表明ZnO纳米棒具有很好的光催化活性。     

Influence of vanadium concentration on the microstructure and magnetic properties of V-doped ZnO thin films

Vanadium doped ZnO thin films (Zn_1 − xV_xO, where x = 0.05 or x = 0.13) were grown on c-cut sapphire substrates using pulsed laser deposition technique. Their structure and magnetic properties were examined in relation to the doping concentration. All deposited films were highly oriented along the c-axis and exhibited ferromagnetic behavior with a Curie temperature up to 300 K. The crystal structure was found to be better for layers with lower vanadium concentration. The films had a porous fine-grained microstructure and a column-like character as the V concentration was reduced. A weak dependence of magnetization on temperature was observed. The saturation magnetization was found to be strongly dependent on the crystal structure, grain size and V-ion concentration.     

Effect of carrier concentration on optical bandgap shift in ZnO:Ga thin films

The Ga-doped ZnO thin films were deposited on glass substrate by sputtering and annealed at 350 °C in hydrogen atmosphere for 1 h. The optical bandgap of thin films showed the lower blueshift than the theoretical value of the Burstein-Moss (BM) effect. The shift of bandgap was dependent on the carrier concentration and acquired by combining the nonparabolic BM effect and bandgap narrowing (BGN). The modified BM effect equation was proposed to substitute the nonparabolic BM effect and BGN. The exponent in the modified BM equation was affected by carrier concentration and it was decreased with carrier concentration.     

Effect of high-energy electron beam irradiation on the properties of AZO thin films prepared by rf magnetron sputtering

We investigated that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affected remarkably the properties of Al-doped ZnO (AZO) films grown on SiO₂ substrates by radio frequency magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the n-type conductivity was preserved in HEEBI treated films with low dose up to 10¹⁵ electrons/cm² and converted to p-type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy confirmed the conversion of conductivity by showing that in-diffusion of O₂ from the ambient as well as out-diffusion of Zn from the films took place as a result of HEEBI treatment at high dose of 10¹⁶ electrons/cm². X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was enhanced by HEEBI treatment with the increase of doses. It was also found that worse crystallinity with a smaller grain size was observed in HEEBI treated films with a higher dose, which was correlated with rougher surface morphologies of films observed by an atomic force microscope.     

Selective growth of ZnO nanorods for gas sensors using ink-jet printing and hydrothermal processes

Selective growth of ZnO nanorod arrays with well-defined areas was developed to fabricate the NO₂ gas sensor. The seed solution was ink-jet printed on the interdigitated electrodes. Then, vertically aligned ZnO nanorods were grown on the patterned seed layer by the hydrothermal approach. The influences of seed-solution properties and the ink-jet printing parameters on the printing performance and the morphology of the nanorods were studied. Round micropattern (diameter: 650 μm) of ZnO nanorod arrays is demonstrated. The dimensions and positions of the nanorod arrays can be controlled by changing the printed seed pattern. The effects of nanorod structure and nanorod size on the gas-sensing capability of ZnO nanorod gas sensors were demonstrated. Due to the high surface-to-volume ratios of the nanorod-array structure, the ZnO nanorod gas sensor can respond to 750 ppb NO₂ at 100 °C. The sensors without baking treatment exhibit the typical response of a p-type semiconductor. However, only the response of n-type semiconductor oxides was observed after the annealing treatment at 150 °C for 2 h.     

X-ray images obtained from cold cathodes using carbon nanotubes coated with gallium-doped zinc oxide thin films

X-ray imaging data obtained from cold cathodes using gallium-doped zinc oxide (GZO)-coated CNT emitters are presented. Multi-walled CNTs were directly grown on conical-type (250 μm-diameter) tungsten-tip substrates at 700 °C via inductively coupled plasma-chemical vapor deposition (ICP-CVD). GZO films were deposited on the grown CNTs at room temperature using a pulsed laser deposition (PLD) technique. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were used to monitor the variations in the morphology and microstructure of the CNTs before and after GZO coating. The formation of the GZO layers on the CNTs was confirmed using energy-dispersive X-ray spectroscopy (EDX). The CNT-emitter that was coated with a 10-nm-thick GZO film displayed an excellent performance, such as a maximum emission current of 258 μA (at an applied field of 4 V/μm) and a threshold field of 2.20 V/μm (at an emission current of 1.0 μA). The electric-field emission characteristics of the GZO-coated CNT emitter and of the pristine (i.e., non-coated) CNT emitter were compared, and the images from an X-ray system were obtained by using the GZO-coated CNT emitter as the cold cathode for X-ray generation.     

Synthesis, characterization and optical properties of star-like ZnO nanostructures

Star-like ZnO nanostructures were synthesized in bulk quantity by thermal evaporation method. The morphologies and structure of ZnO nanostructures were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor-solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow ultraviolet emission at around 380 nm and a broad green emission around 491 nm. Raman spectrum of the ZnO nanostructures was also discussed.     

Raman spectra and photoluminescence properties of In-doped ZnO nanostructures

In-doped ZnO nanostructures with four different morphologies, which are nanotetrapods, nanocombs, nanowires, and nanodisks, have been synthesized on silicon substrates by a simple thermal evaporation method. The XRD patterns show the In-doped ZnO nanostructures are all with the hexagonal wurtzite structure, and a slight difference in lattice parameters had been detected among the samples with various morphologies. The Raman spectra demonstrate that the vibrational mode of 2LA, which is very weak in undoped ZnO, was strongly enhanced with indium ion doping into ZnO structures. The photoluminescence (PL) measurements indicate that the nanodisks have a relative strong ultraviolet (UV) emission than other three kinds of samples.     

Dynamic compressive response and failure behavior of fiber polymer composites embedded with tetra-needle-like ZnO nanowhiskers

Glass fiber polymer composites embedded with tetra-needle-like zinc oxide (ZnO) nanowhiskers were prepared. The prepared composites exhibited excellent mechanical properties after the effective dispersion of ZnO nanowhiskers in the resin. The static and dynamic compressive properties of the composites were tested in the thickness and in-plane directions. The macro- and microfracture morphologies of the damaged specimens were obtained by using a scanning electron microscope. The results show that the compressive properties of the composites could be significantly affected by strain rates. As the strain rate increases, the composites have a higher strength. The compressive properties of the composites are affected by the content of ZnO nanowhiskers in the resin. The high strength of the composites can be attributed to the three-dimensional structures of ZnO nanowhiskers and the corresponding stress transfer.     

Co/Co_9S_8/ZnO核壳结构纳米微球的制备与表征

在无水无氧条件下通过热分解还原制备Co纳米微粒,利用Co9S8和ZnO晶格的相匹配性,通过层层自组装对Co表面进行修饰,得到Co/Co9S8/ZnO核壳结构纳米微球.采用XRD、TEM、SQUID、光致发光光谱(PL)等对产物进行了表征.通过调节反应参数制备出核壳结构的Co/Co9S8/ZnO复合纳米微球,平均粒径58.8nm,壳层厚度均匀,常温下显示铁磁性,矫顽力为18.7kA/m.PL表明,产物在380~390nm处的带边跃迁不明显,光致发光最强峰在468nm处,属氧缺陷发射峰,研究了影响产物形貌的主要因素.结果表明,以油酸(OLA)及三正辛基氧化磷(TOPO)为溶剂和表面活性剂,Zn(acac)2温度为70℃、用量为1mmol,控制Co的硫化反应时间为5min,有利于核壳结构产物的形成.初步分析了Co/Co9S8/ZnO核壳结构纳米微球的形成机理.