【作者】 鲁启鹏；

【导师】 侯延冰；

【作者基本信息】 北京交通大学 ， 光学工程， 2014， 博士

【摘要】 本论文围绕Ti02和Y203纳米材料的光电性质展开研究,论文的主要内容分为三部分：1.采用光催化合成的方法制备Ag-TiO2纳米复合材料,并对纳米结构形成的机理做出了解释。令合成的过程中,在紫外光激发下Ti02纳米棒产生的电子还原Ag(Ⅰ)并产生若干Ag的纳米颗粒沉积在TiO2纳米棒的表面。通过延长光照时间,在紫外光促进的熟化作用下,粒径较小的Ag颗粒被光生空穴氧化、溶解,随后被光生电子还原并沉积在较大的Ag颗粒上,从而形成一个Ag纳米颗粒对应一根Ti02纳米棒的异质结结构。Ag纳米颗粒的粒径可以通过改变紫外光照的时间和空穴捕获剂的量来精确调节。(?)将Ag-TiO2纳米复合材料用作反型薄膜太阳能电池的电荷传输层,相比纯TiO2制备的器件,光电转换效率明显增加,从5.81%增加至6.92%。从外量子效率谱中可以看出,Ag的引入可以有效提高对电子的收集作用。2.在Ti02纳米棒催化合成Au颗粒中,通过对实验条件的控制,如反应温度、紫外光照时间、TiO2纳米棒的量等,Au纳米颗粒的形成机理得以研究(?)实验证明,单分散且粒径可控的Au纳米颗粒可以通过TiO2纳米棒光化学还原的方法被合成。(?) Au纳米颗粒的形成可以分为以下三个过程：Au(Ⅲ)还原形成Au(O),成核,籽晶生长。通过控制实验条件可以得出以下结论：第一步的还原反应主要取决于体系的温度,而成核和籽晶生长的速度主要取决于TiO2产生的电子的数量。3.通过共沉淀和热处理的合成方法制备了Er和Yb双掺的Y203纳米颗粒。通过表面活性剂引入缺陷和高温退火消除缺陷,研究了两个过程对Y203：Er,Yb纳米颗粒的形貌以及上转换发光性质的影响,在此基础上,阐述了发光颜色调控的机理。(?)由于表面活性剂可以在发光体系中引入缺陷,所以控制其浓度可以达到调控绿光(2H11/2,4S3/2→4I15/2)和红光(4F9/2→4◇15/2)上转换发光的强度的目的。同时,缺陷的增加导致了4F7/2,2H11/2和4S3/2向4F9/2弛豫几率的增加,进而使得材料发光的红绿比得到控制。(?)在体系中,通过高温退火消除缺陷,进而可以选择性的提高绿光(2H11/2,4S3/2→4I15/2)和红光(4F9/2→4I15/2)的发光强度,使材料的发光颜色从红光向绿光转变。图69幅,表7个,参考文献202篇更多还原

【Abstract】 This work is focused on the investigation of optoelectroic properties based on TiO2and Y2O3nano-materials. The main contents of dissertation include three parts.1. A photocatalytic strategy was developed to synthesize colloidal Ag-TiO2nanorod composites and the mechanism of the formation for Ag-TiO2nanorod composites was investigated.(?) Under UV illumination, TiO2nanorods produces electrons which reduce Ag (Ⅰ) precursor and deposit multiple small Ag nanoparticles on the surface of TiO2nanorods. Prolonged the time of UV irradiation induces an ripening process, in which the smaller nanoparticles is dissolved by photo-generated oxidative species and then redeposited onto one largest and more stable particle attached to each TiO2nanorod. The size of the Ag nanoparticles can be precisely controlled by varying the irradiation time and the amount of alcohol additive.(?)The Ag-TiO2nanorod composites were used as electron transport layers in the fabrication of organic solar cells, and showed notable enhancement in power conversion efficiency (6.92%) than pure TiO2nanorods (5.81%), which is attributed to the improved electron extraction.2. For the photocatalytic synthesis of gold nanoparticles assisted by TiO2nanorods, the mechanism was studied carefully by change the reaction temperature, UV irradiation time and amount of the TiO2nanorods.(?) Monodispersed gold nanoparticles were synthesized through a photochemical reduction approach using TiO2nanorods as the photocatalysts.(?) The formation of Au nanoparticles ccould be divided into three processes:the reduction of Au(Ⅲ), nucleation and growth of the gold seeds. The first step mainly depends on the temperature. And nucleation and growth of the gold seeds processes highly depend on the electrons generated on the TiO2nanorods.3. Er and Yb co-doped Y2O3nanoparticles were prepared by using a coprecipitation method followed by a post-thermal-treatment. In order to study the upconversion properties of the Y2O3:Er, Yb nanoparticls, the defects were induced and removed by surfactant and calcination. Moreover, the mechanism of color tuning was investigated.(?)The green (2H11/2,4S3/2→4I15/2) and red emission (4F9/2→4I15/sn) intensity can be effectively tuned by varying the surfactant concentration, which can induce the defects in the as-obtained products. The probability of quenching from4F7/2,2H11/2, and4S3/2to4F9/2could be increased as the number of defects introduced by the surfactant increases, and thus the ratio of red to green emission is also changed.(?) After removing the defects via high temperature calcination, the green emission (2H11/2,4S3/2→4I15/2) and red emission (4F9/2→4I15/2) of Er ions are enhanced selectively, which leads to that the color of upconversion emittion is tuned from red to green.更多还原