【作者】 王辉；

【导师】 刘润；

【作者基本信息】 浙江大学 ， 化学， 2012， 硕士

【摘要】 稀土离子具有丰富的能级跃迁和光转换方式,能够发射色彩鲜亮纯正、寿命长的可见光,使稀土发光材料在激光、显示、照明、生物标记等领域应用广泛。近年来,稀土发光材料的合成引起了研究者的兴趣。电沉积法作为反应条件温和、成本低、易控制的合成方法,有望实现材料的大规模工业生产。本论文采用电沉积法制备出了稀土离子掺杂的CaF2、NaYF4、 LaPO4发光材料,并对它们的结构、形貌、下转换、上转换发光等性质进行了研究。本论文研究分为三个部分：(1)电沉积制备CaF2和CaF2:Ln3+薄膜及光学性能研究。在Ca2+-EDTA和NH4F溶液体系中,以ITO导电玻璃作为工作电极,通过氧化抗坏血酸根离子来降低电极表面的pH值,从而使Ca2+-EDTA络合物解离出Ca2+,与游离的F-结合生成CaF2,沉积在ITO玻璃表面形成薄膜。采用XRD、SEM、EDS、FL等测试方法对薄膜进行了表征,探讨了可能的反应机理和球体形貌产生的原因。EDS面分布表明稀土离子均匀地掺杂在了CaF2薄膜中,CaF2:Ln3+呈现出良好的下转换和上转换发光性能。(2)稀土掺杂NaYF4薄膜的电化学合成及上转换发光性能研究。本章中采用电沉积法制备了稀土掺杂的NaYF4薄膜并着重对其上转换发光性质进行了探讨。上转换发光是稀土离子的独特性能,可通过多光子吸收将长波的红外光转换成短波的可见光。NaYF4:Yb3+,Er3+材料在980nnm激光激发下,发射绿光和红光；同时我们研究了’Yb3+/Er3+离子掺杂比、沉积温度、退火温度等因素对上转换发光的影响,并初步探讨了发光机理。Tm3+作为激活剂的NaYF4:Yb3+,Tm3+薄膜可发射上转换蓝光。此外,NaYF4:Tb3+, NaYF4:Eu3+可发射相应稀土离子的特征荧光,荧光强度与浓度淬灭现象有关。(3)纳米棒状LaPO4和LaPO4:Ln3+的电沉积制备及表征。采用阳极电沉积法在未加入表面活性剂、催化剂、模板等添加剂的水溶液中,制备了具有一维纳米棒状形貌的LaPO4:和LaPO4:Ln3+薄膜。经分析,纳米棒的形成与沉积温度密切相关,较高的温度使其结晶性增强,棒状形貌明显；此方法制备的LaPO4为六方相,具有类单晶结构。同时,LaPO4是良好的荧光基质材料,当其中掺杂不同的稀土离子时,呈现特征发光。电沉积制备了LaPO4:Ce3+,Tb3+荧光材料,Ce3+作为敏化剂、Tb3+作为发光中心,Ce3+、Tb3+离子之间存在高效的能量传递,使其发射强烈绿光。更多还原

【Abstract】 Owing to their abundant energy level transition and light conversion modes, rare-earth ions have been widely used in luminescent materials. With intense and long-life luminescence, rare-earth luminescent materials have potential application in fields of laser, display, lighting and biological label. Recently, rare-earth luminescent materials have attracted considerable research interest because of these extensive usages.Compared with other techniques, electrodeposition is a facial method with many advantages, such as low process temperature, low cost, and capability of controlling grain size, morphology and chirality of the deposited films. Rare-earth doped CaF2, NaYF4and LaPO4films have been synthesized by electrodeposition, and their structure, morphology, down-conversion and up-conversion luminescent properties have been discussed. The content of this thesis are listed as following:(1) Electrodeposition and characterization of CaF2and CaF2:Ln3+films:The solutions containing Ca2+-EDTA and NH4F have been used as reactor and CaF2films have been prepared on ITO electrode through anode electrochemical generated acid in solutions. H+ions are generated by the electrochemical oxidation of ascorbate anion instead of water, which is beneficial to cut down the oxidation potential. The released H+ions will lower the pH at the surface of working electrode. Calcium ions are set free from the Ca2+-EDTA complex and then react with F" ions to form CaF2deposits. CaF2and CaF2:Ln3+films are characterized by SEM, XRD, EDS and FL. The CaF2films are composed of spheres, and we also explore the reasons of the morphology. It has been proved that rare earth ions are uniformly distributed in the films by EDS mapping. CaF2:Ln3+films possess not only good down-conversion but also up-conversion properties.(2) Up-conversion fluorescence of lanthanide doped NaYF4films synthesized by electrodeposition:Lanthanide doped NaYF4films have been synthesized by electrodeposition and their up-conversion properties have been studied deeply. Up-conversion (UC) is a process that low energy light, usually near-infrared (NIR), is converted to ultraviolet (UV) or visible by multiple absorptions. When excited at980nm in near-infrared region, NaYF4:Yb3+,Er3+emit intense green and red light, and factors affecting the ratio of green to red are explored in the experiments. Furthermore, it is proved that two-photon up-conversion mechanism is involved in the emission of green and red light. NaYF4:Yb3+,Tm3+film has also been synthesized and it emits bright blue light. The optical properties of down-conversion materials, such as NaYF4:Eu3+and NaYF4:Tb3+, have been studied by photoluminescence (PL) spectra and phenomenon of concentration quenching has been observed.(3) Synthesis and luminescent properties of LaPO4and LaPO4:Ln3+nanorods: LaPO4and LaPO4:Ln3+nanostructures composed of interlaced nanorods or nanowires have been electrodeposited on tin doped indium oxide (ITO) substrate through electrochemical generation of acid in aqueous solutions without any surfactant, catalyst, or template. LaPO4nanorods can be indexed to hexagonal phase by XRD and they are single crystal like structure by electron diffraction (SAED). The optical properties of LaPO4:Ln3+nanostructures have been characterized by PL, and among them LaPO4:Ce3+,Tb3+shows a commercial value. In this material, Ce3+ions act as sensitizer and Tb3+ions act as activator. Due to efficient energy transfer between them, bright green light could be observed.更多还原