ZnO纳米带梳的制备及生长机理的研究

采用化学气相沉积(CVD)法成功制备出ZnO纳米带梳,实验过程不需要催化剂.X射线衍射仪(XRD)分析结果表明,ZnO纳米带梳为高度结晶的六方纤锌矿结构;利用扫描电子显微镜(SEM)观测,所制样品是由纳米带组成梳状形貌,纳米带梳的形成经过两个步骤:先通过VS机制形成微米带,而梳的齿通过自催化生长平行于(0001)极性面形成.对样品的光致荧光(PL)谱测量发现了位于～395nm和495nm处的室温光致发光峰.     

ZnO纳米阵列增强大功率蓝光LED出光效率的研究

采用低成本的化学溶液法在大功率GaN基蓝光LED芯片上生长ZnO纳米阵列, 以提高LED芯片的出光效率. 通过改变生长溶液中氨水及锌离子浓度实现对纳米阵列结构形貌的可控性, 进而得到不同形貌的ZnO纳米阵列. 在此基础上, 进一步研究纳米结构形貌对LED芯片出光性能的影响, 探讨纳米结构增强LED芯片发光效率的机理. 结果表明, 较高密度、锥形形貌的ZnO纳米阵列更有利于增强LED芯片的出光效率. 在优化的实验条件下, 表面沉积ZnO纳米阵列的LED芯片比普通LED的出光效率高出60%以上, 并且纳米阵列不影响LED器件的电学性能和发光稳定性.     

分级氧化铟纳米结构的同质外延生长及发光性能

用无催化碳热还原法合成了大量三维分级的In2O3亚微/纳米结构,用XRD、SEM、TEM和EDS等手段对In2O3纳米棒的形貌、成分和结构进行了表征.结果表明:In2O3纳米棒为具有体心立方结构单晶,沿着<100>和<111>方向外延生长,属于自组装和气固外延生长机制.同质外延生长的分级结构是"二次成核"和气固生长协同...     

纳米ZnO阵列形貌对其光催化降解性能的影响

利用溶液法在不同形貌基片上制备了ZnO纳米棒阵列。通过聚苯乙烯球自组装阵列控制模板基片的形貌,制备出具有周期性结构的ZnO纳米花点阵;进而通过反应离子刻蚀聚苯乙烯球模板,实现了ZnO周期性点阵由纳米花向纳米环的结构转变。以亚甲基蓝水溶液为目标降解物,比较了不同ZnO纳米棒阵列的光降解能力,发现单位基片面积上ZnO纳米棒的有效受光面积是影响ZnO纳米棒阵列光降解能力的重要因素。     

溶液生长ZnO一维纳米阵列及其复合纳米结构的研究进展

对溶液生长ZnO一维纳米阵列的研究进展进行了评述,分析了晶种制备和溶液生长过程中各工艺因素对阵列微观形貌的影响,并介绍了在溶液中通过控制定点成核并利用有机基团调控ZnO晶体生长习性的合成路线用于构筑ZnO复合纳米结构的最新研究,指出了溶液生长ZnO一维纳米阵列和构筑复合结构中存在的问题及今后的研究方向.     

ZnO纳米棒阵列、纳米片及其发光和光催化特性

首先通过溶胶-凝胶法在Si片基底上制备1层ZnO纳米薄膜,作为纳米棒的晶种层,然后利用金属浴沉积法在ZnO纳米薄膜基础上制备择优取向的ZnO纳米棒阵列,最后通过水热法二次成核结晶形成纳米片。研究证明,ZnO纳米棒阵列和纳米片均沿着c轴取向。在Cu2+抑制极性面生长的作用下,形成的ZnO纳米片结构均匀,分布面积广,单片ZnO纳米片的厚度约为8 nm,面积呈平方微米级,较大的有40μm2左右。ZnO纳米结构的生长取向对其物理化学性能具有重要影响。高度沿c轴取向的ZnO纳米棒有利于紫外光发射和激光器的发展,但极性面的缩小不利于光催化反应。     

基于ZnO纳米带的纳米器件

ZnO作为一种被人们广泛研究的具有优良性质的半导体材料,在具有了纳米带状结构之后,展现出了更多的奇特性质.主要介绍了ZnO纳米带的合成以及ZnO纳米带二极管、激光器、微悬臂和声学谐振器等4种基于ZnO纳米带的纳米器件的制作及其性能的研究.     

ZnO/Zn2SnO4纳米电缆结构表征与发光特性

ZnO、Zn2SnO4均为直接带隙宽禁带氧化物半导体,是优异的功能材料.以ZnO、SnO2为原料,通过共热蒸发法,合成了ZnO/Zn2SnO4纳米电缆结构.该纳米电缆结构为以ZnO为芯,Zn2SnO4为鞘,直径为50~100nm,长度可达上百微米.通过TEM分析手段,发现该纳米电缆结构中,ZnO的生长方向为<0001>方向,ZnO芯与Zn2SnO4鞘之间形成晶格外延关系.室温下光致发光谱结果显示,该纳米电缆结构在紫外区域(380.58nm附近处)存在很强的带边发光,而在可见光区域没有明显的发光带,这一结果表明:Zn2SnO4鞘层的存在能有效抑制ZnO表面的缺陷发光.ZnO/Zn2SnO4纳米电缆结构可以抑制电子-空穴的复合,在染料敏化太阳能电池等方面有一定的应用潜力.     

ZnO纳米棒阵列和薄膜的同步外延生长及其光电化学性能

使用化学气相沉积法在a面蓝宝石衬底上同步外延生长氧化锌(ZnO)竖直纳米棒阵列和薄膜,研究了阵列和薄膜的光电化学性能。结果表明,纳米结构中的竖直单晶纳米棒有六棱柱形和圆柱形,其底部ZnO薄膜使竖直纳米棒互相联通。与ZnO纳米薄膜的比较表明,这种纳米结构具有优异的光电化学性能,其入射光电流效率是ZnO纳米薄膜的2.4倍;光能转化效率是ZnO纳米薄膜的5倍。这种纳米结构优异的光电化学性能,可归因于其高表面积-体积比以及其底部薄膜提供的载流子传输通道。本文分析了这种纳米结构的生长过程,提出了协同生长机理：Au液化吸收气氛中的Zn原子生成合金,合金液滴过饱和后ZnO开始成核,随后在衬底表面生成了ZnO薄膜。同时,还发生了Zn自催化的气-固(VS)生长和Au催化的气-液-固(VLS)生长,分别生成六棱柱纳米棒和圆柱形纳米棒,制备出底部由薄膜连接的竖直纳米棒阵列。     

海胆形氧化锌纳米结构的制备与光催化性能

以Zn(AC)2.2H2O为原料,NH3.H2O为络合剂,在NaBH4辅助下140℃水热反应2 h制备出ZnO纳米棒自组装的海胆形结构。采用X射线衍射仪、扫描电镜和透射电镜对产物进行表征。结果表明,海胆形ZnO结构的直径约为3～17μm,它是由直径约为100 nm,长度约为500 nm～3μm范围的ZnO纳米棒自组装而成。提出了ZnO纳米棒自组装海胆形结构的可能生长机理。NaBH4与溶液中的少量H+结合生成H2气泡,ZnO纳米晶吸附在H2的气液界面形成了纳米颗粒自组装的微球,随着反应时间的延长,组装成微球的ZnO纳米颗粒沿[0001]方向取向生长成ZnO纳米棒,最终形成ZnO纳米棒自组装的海胆形颗粒。室温下以海胆形ZnO纳米结构和ZnO纳米棒为光催化剂,以偶氮染料甲基橙作为光催化研究对象,紫外光照70 min,对甲基橙的降解率分别为97%和67%。     

Fabrication of ZnS/ZnO hierarchical nanostructures by two-step vapor phase method

A simple two-step vapor phase method is presented to fabricate ZnS/ZnO hierarchical nanostructures in bulk quantities. That is ZnS nanobelts were first synthesized and then used as substrate for growth of ZnO nanorod arrays. Investigation results demonstrate that the polar surfaces of ZnS nanobelts could induce a preferred asymmetric growth of ZnO nanorods on the side surfaces. But it is believed that if the local concentration of ZnO was high enough, ZnO nanorods could also grow symmetrically on the top/bottom surface of the ZnS nanobelts. The optical property of the products was also recorded by means of photoluminescence (PL) spectroscopy.     

Controlled synthesis of ZnO branched nanorod arrays by hierarchical solution growth and application in dye-sensitized solar cells

We demonstrate the controlled synthesis of ZnO branched nanorod arrays on fluorine-doped SnO₂-coated glass substrates by the hierarchical solution growth method. In the secondary growth, the concentration of Zn(NO₃)₂/hexamethylenetetramine plays an important role in controlling the morphology of the branched nanorod arrays, besides that of diaminopropane used as a structure-directing agent to induce the growth of branches. The population density and morphology of the branched nanorod arrays depend on those of the nanorod arrays obtained from the primary growth, which can be modulated though the concentration of Zn(NO₃)₂/hexamethylenetetramine in the primary growth solution. The dye-sensitized ZnO branched nanorod arrays exhibit much stronger optical absorption as compared with its corresponding primary nanorod arrays, suggesting that the addition of the branches improves light harvesting. The dye-sensitized solar cell based on the optimized ZnO branched nanorod array reaches a conversion efficiency of 1.66% under the light radiation of 1000 W/m². The branched nanorod arrays can also be applied in other application fields of ZnO.     

Optical and electrical properties of Ga-doped ZnO nanorod arrays fabricated by thermal evaporation

Well-aligned Ga-doped ZnO nanorod arrays with high optical and electrical property were fabricated by catalyst-free thermal evaporation on p-silicon substrate. As the Ga/Zn atom ratio in the source material was tuned from 0 to 0.2, wurtzite structure ZnO nanorod arrays were realized with length of -6 microm and growth direction along c-axis. With the addition of Ga, the intensity of the near-band-edge emission was enhanced and the deep-level emissions maintained neglectable. As the Ga/Zn atom ratio increased from 0 to 0.1, the red shift of the near-band-edge emission occurred due to Ga-doping induced band gap renormalization effect related with the enhancement of the carrier density, while the blue shifts of the emission were found once the Ga/Zn ratio is higher than 0.1 resulting from Burstein-Moss effect. The configuration of the vertical-aligned Ga-doped ZnO nanorod arrays on p-Si substrate makes it straightforward for the fabrication of p-n nanodiode, which shows an excellent rectifying characteristic with threshold voltage as low as -4.7 V with the Ga/Zn atomic ratio of 0.2.     

Necktie-like ZnO nanobelts grown by a self-catalytic VLS process

ZnO nanobelts with triangular top/bottom surfaces (so-called necktie-like nanobelts) are synthesized by a vapor transport deposition method. Scanning electron microscopy observations show that the ZnO nanobelts have a necktie-like morphology and are capped by particles. Transmission electron microscopy examinations indicate that the nanobelts have top and bottom surfaces of ± (11–20), and grow along [1–100]. The particles adhered at tips of the nanobelts are proved to be ZnO. On the basis of SEM and TEM observations, it is believed that the growth of the necktie-like ZnO nanobelts is a VLS process catalyzed by Zn droplets, i.e. a self-catalytic VLS growth. The result reported here is new evidence for such a mechanism.     

Effect of pulsed electromagnetic field on growth and structure properties of ZnO nanorod arrays

Well-aligned ZnO nanorod arrays had been prepared by hydrothermal methods assisted with pulsed electromagnetic field (PEMF). The effects of pulsed electromagnetic field on growth and structure properties of ZnO nanorod arrays were studied in detail. XRD and SEM analysis showed ZnO nanorod arrays had bigger length to diameter ratio and better verticality on the substrate. And the Raman analysis showed well-aligned ZnO nanorod arrays have highly crystallized wurtzite structure with much fewer defects after a pulsed electromagnetic field was introduced. At last, a possible mechanism of pulsed electromagnetic field acted on nanorod arrays was proposed.     

可见光诱导TiO2光催化及其机理研究进展

简述了二氧化钛的光催化机理。针对其禁带宽度较大,只能被小于387nm的紫外光所激发的缺点,综述了近年来国内外针对纳米TiO2可见光催化的改性方法和改性机理研究进展,包括离子掺杂、半导体复合、表面光敏化等方法。最后展望了提高纳米TiO2可见光光催化活性研究的前景。     

The competition growth of ZnO microrods and nanorods in chemical bath deposition process

Well-aligned ZnO nanorod arrays were synthesized on the c-axis orientated ZnO seed layer by chemical bath deposition (CBD) technique. Randomly distributed ZnO microrods with big diameter and growth speed were also formed simultaneously in the same process. The growth of the microrods followed the expected diffusion-limited Ostwald ripening mechanism reasonably well, while that of the nanorods was suggested to be controlled not only by the nutrition ions available but also by the density of nuclei site and the reaction kinetics on the growing surfaces, etc. The microstructure and optical properties of the well-ordered nanorod were also investigated.     

Site-specific multi-stage CVD of large-scale arrays of ultrafine ZnO nanorods

Multi-stage growth of ZnO nanorod arrays has been carried out by Au-assisted chemical vapor deposition (CVD) in order to better understand and more precisely control the growth behaviors. It is evidenced that Au-catalyzed vapor-liquid-solid (VLS) growth only dominates the initial site-specific nucleation of the nanorods, while the subsequent growth is governed by a vapor-solid (VS) epitaxy mechanism. The sequential VLS and VS behaviors permit the fabrication of large-scale highly ordered arrays of ZnO nanorods with precisely tunable diameters and embedded junctions by controlling reactant concentration and nanorod top morphology. Based on the above results, two routes to fabricate ultrafine ZnO nanorod arrays are proposed and stepwise nanorod arrays with ultrafine top segment (~10 nm in diameter) have been achieved. Temperature-dependent photoluminescence (PL) and spatial resolved PL were carried out on the nanorod arrays and on individual nanorods, indicating high quality optical properties and tunable light emission along the length of the stepwise nanorods.     

Synthesis and photoluminescence properties of the ZnO@SnO<Subscript>2</Subscript> core–shell nanorod arrays

The ZnO@SnO₂ core–shell nanorod arrays have been synthesized. As the cores, ZnO nanorod arrays were first prepared by aqueous chemical growth method. Then using a simple liquid-phase deposition method, SnO₂ was deposited on the ZnO nanorod arrays. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were used to characterize the morphologies and structures of the products. Photoluminescence properties were also investigated. It was found that the ZnO@SnO₂ core–shell nanorod arrays showed enhanced UV and green emissions when compared with the bare ZnO nanorod arrays.