【作者】 王昕；

【导师】 韩高荣；

【作者基本信息】 浙江大学 ， 材料学， 2007， 博士

【摘要】 ZnO由于同时具有优异的半导体、压电、热电和荧光特性而一直得到广泛的关注和应用。尤其是在近年来发现ZnO作为一种典型的直接带隙半导化合物,室温下的禁带宽度为3.37eV,激子结合能为60meV,可用于短波长半导体激光器、紫外光发射和探测器件、透明半导体、机电耦合传感器等光电子纳米器件,使得ZnO成为纳米领域的研究热点。本论文综述了近年来纳米氧化锌的制备方法及它们的应用状况。鉴于气相法制备纳米氧化锌需要昂贵的实验设备、较高的实验温度、且产物收集困难,本研究着眼于液相法制备低维纳米氧化锌材料,主要包括可以低成本规模化生产的水热/溶剂热法、溶胶—凝胶法和直接反应沉淀法,通过不同的制备条件来实现对纳米氧化锌的形貌控制并对纳米氧化锌的形貌控制机理进行了系统的研究。最后为了实现纳米氧化锌的有序可控生长,深入研究了利用模板法制备纳米氧化锌,并对其结构和性能进行表征。本文的主要工作和取得的主要结果如下:1.水热法中,选用聚乙二醇（PEG）为软模板,水为溶剂,调节Zn²⁺╱OH浓度,成功制备出包括纳米碗、纳米棒、纳米花在内的多种形貌纳米氧化锌。PEG在水溶液中的分相团聚现象是合成纳米碗和纳米花纳米结构的决定性因素。2.溶剂热法中,选用聚乙二醇（PEG）为软模板,乙醇与水为混合溶剂,调节Zn²⁺╱OH^-浓度,制备出包括纳米线、纳米棒、六角螺母、六方棱柱在内的不同形貌纳米氧化锌,探讨了PEG作为软模板对产物形貌的控制。由于PEG会同时和溶剂分子及Zn²⁺产生化学键和,因此PEG的作用主要受到[OH^-]/[Zn²⁺]的影响。只有在[OH^-]/[Zn²⁺]=2:1时才能够得到一维纳米氧化锌,在[OH^-]/[Zn²⁺]=1:1的条件下则只能形成六角螺母和六方棱柱,在其他更高的反应物浓度比范围则形成纳米棒同十四面体的混合体。3.采用两步阳极氧化法,以草酸为电解液制备出高度有序的多孔氧化铝,孔洞垂直铝片表面呈六方蜂窝状排列,孔径大小一致并可通过阳极氧化参数调节孔道尺寸,为定向有序生长纳米氧化锌提供完美模板。4.以醋酸锌为先驱体配置溶胶溶液,通过浸渍法、滴入法和真空抽滤法,在毛细管力、重力和大气压力作用下,将ZnO胶体渗入阳极氧化铝模板的孔道,利用模板的空间限制效应,控制氧化锌纳米线的生长位置和尺寸。其中,以真空抽滤法的效果最佳,可获得直径约60nm,长达几微米的氧化锌纳米线阵列。5.以氨水为矿化剂采用直接反应沉淀法制备纳米氧化锌,在不同锌离子浓度下,pH值以及温度的条件下成功得到星状、针状、棒状等不同形貌的低维纳米氧化锌材料。在直接反应沉淀法的基础上选用制—维纳米氧化锌的最佳条件并将阳极氧化铝模板引入反应体系作为异相形核生长的基板,成功制备出了直立的片状氧化锌纳米晶有序阵列。6.水热法和直接沉淀法可以制备结晶完好的氧化锌纳米颗粒,具有较好的本征蓝紫光（约390nm）发光特性,但由于颗粒形貌各异、分布无序,发光峰宽化,且样品中存在较多氧空位,出现绿光（约460nm）和橙黄光（＞500nm）的发射。利用多孔氧化铝模板有序的孔洞排布,可以控制氧化锌纳米结构的生长位置和形貌,特别是结合真空抽滤手段生长的有序纳米线阵列,仅在蓝紫光区域出现强烈发光峰,具有良好的发光性能。更多还原

【Abstract】 Zinc oxide has been widely used in different industries due to its excellent semiconductor, piezoelectric,pyroelectric and fluorescent properties.In recent years,ZnO was found to be a unique direct band semiconductor with band gap of 3.37eV and exciton binding energy of 60meV at room temperature,which makes it a very attractive for the potential application as a nano-device in the fields of short wavelength semiconductor laser,UV light emission and detector,transparent semiconductor and electromechanical coupling sensor etc.,thus ZnO has been a hot topic in the last decades in "Nano" science.A comprehensive and detailed review about the synthesis methods of preparing ZnO nanostructure was done in this thesis.Due to the shortcomings encountered in the vapor condensation methods,including expensive and complicated equipment,high reaction temperatures and difficult product collection procedures,the simple and easy-to-realize liquid route,including low-cost and easy-to-scale-up hydrothermal/solvothermal,sol-gel and reaction precipitation,were focused in this thesis as the tools to make ZnO nanostructures with preferred morphologies and properties.The mechnisms of controlling ZnO morphologies through different synthesis parameters were discussed.For the final purpose of making ordered and controllable growth of ZnO,further investigation with the growth of ZnO by applying templates were also done,the microstructure and properties of these nanostructures are analysed.Accordingly,the main work done and main results are summarized as followings:1.In hydrothermal synthesis,PEG was selected to work as a soft template to modulate the morphology and water as the solvent.ZnO nanostructures including nano-bowl,nano-rod and nano-"flower" were successfully synthesized by changing Zn²⁺/OH^- concentrations and ratios.The phase separation and aggregation phenomean are the key factors for the formation of nano-bowl and nano-"flower".2.In solvothermal synthesis,PEG was selected to work as a soft template to modulate the morphology while ethanol and water as the solvent.ZnO nanostructures including nanowire, nano-rod,hexagonal nut and prism were successfully synthesized by changing OH^-concentrations and ratios.The morphology is controlled by the PEG in solution due to its chemical bonding interactions with solvent molecule and Zn²⁺.When[OH^-]/[Zn²⁺]=2:1,the final products are one-dimensional nanostructure;when[OH^-]/[Zn²⁺]=1:1,the final products are hexagonal nuts and prism;and the final products are nanorod or polyhedral at higher reagent concentration3.Two-step anodic method is chosen to fabricate ordered porous alumina oxide template by using oxalic acid as electrolyte.With the proper anodization parameter,ordered honeycomb structure with uniform channel diameters and spacing of the pores can be fabricated with this method.This affords a promising route to synthesize large-area,ordered nanostructure with high aspect ratio.4.Combining template and sol-gel method,zinc oxide sol prepared from zinc acerate as precursor can be introduced into the nanosized channel of anodic alumina oxide template by the capillary force,gravity or gas pressure as the driving force,thus ZnO nanowire can be grown under the confinement of the channel size afterwards.Different methods of dipping, dripping and vacuum pumping were applied for the best performance.Through vaccum pumping method,as the best in three,nanowire array with diameter of 60nm and length of several micrometers can be prepared.5.In the direct reaction precipitation method,amonia was selected as the simple precipitation reagent.ZnO nanostructures with morphologies of star,rod or needle can be harvested by changing Zn²⁺concentration,pH values and temperatures.Based on the results of getting 1-dimentional ZnO nanostructures,anodic alumina oxide template was introduced to grow ZnO on the surface by heterogenous crystallization process.Ordered and highly compacted ZnO nanostructured film composed of erected hexagonal nano-flakes is successfully prepared on the top of AAO template.6.Well-crystallized zinc oxide nanostructures synthesized by hydrothermal method and precipitation method show not only intrinsic violet emission but also green and orange emission coming from the oxygen vacancy.Take advantage of the ordered structure of anodic alumina oxide,the growth position and morphology of the zinc oxide nanostructures are controllable,highly ordered zinc oxide nanowire array is further synthesized using vacuum pumping mehod,which shows very good violet emission.更多还原