Preparation of Semiconductor Nanoparticle-Assembled Layers Having Desired Photoluminescent Properties

我们开发了新的策略来制备二氧化硅涂层半导体纳米颗粒复合材料，该复合材料具有理想的光化学性质。采用逐层积累技术制备纳米复合材料的颗粒层。采用尺寸选择光蚀刻技术，将所得颗粒的纳米结构修饰成铃铛形状。首先，对二氧化硅包覆的硒化镉（SiO2/CdSe）纳米颗粒进行了尺寸选择性光蚀刻，以精确控制其光致发光性能。虽然制备的SiO2/CdSe不表现出光致发光，但对SiO2/CdSe进行尺寸选择性光蚀刻后，其带隙发光得到了发展，且程度随着光蚀刻的进行而增强。SiO2/CdSe纳米颗粒膜的部分光蚀刻在光蚀刻区域产生强烈的CdSe带隙发射，而其余的SiO2/CdSe膜没有表现出更强的可探测光致发光，从而在紫外照射下形成清晰的光致发光图像。这种技术使得使用单一源材料用具有不同波长的单色光照射产生多色光致发光图像成为可能。其次，通过添加三烷基胺来猝灭钟形二氧化硅包覆的硫化镉纳米颗粒（SiO2/CdS）的光致发光，猝灭程度取决于它们的分子大小。这是由于淬灭剂分子通过铃形纳米颗粒的SiO2壳孔，从体溶液中选择性地渗透到孔洞中。所制备的钟形半导体纳米粒子具有较强的光致发光特性，其重组位点较少，是一种很有前途的光能转换材料。铃铛形SiO2/CdS颗粒的光催化活性明显高于市售散装CdS颗粒。特别是在硝基苯的光还原反应中，可以通过改变光催化剂的纳米结构来改变产物的收率和选择性。少

We developed novel strategies of the preparation of silica-coated semiconductor nanoparticle composites which exhibited the desired photochemical properties. The particulate layers of the nanocomposites could be prepared by using layer-by-layer accumulation techniques. The nanostructure of the obtained particles was modified to the shape of the jingle bell by using the size-selective photoetching technique.First, the size-selective photoetching was applied to silica-coated cadmium selenide (SiO2/CdSe) nanoparticles to precisely control their photoluminescence properties. Although as-prepared SiO2/CdSe did not exhibit photoluminescence, the application of size-selective photoetching to SiO2/CdSe resulted in the development of the band gap emission, the degree being enhanced with progress of the photoetching. Partial photoetching of SiO2/CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, while the remainder of the SiO2/CdSe films did not exhibit d … More etectable photoluminescence, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolor photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material. Second, the photoluminescence of the jingle-bell-shaped silica-coated cadmium sulfide nanoparticles (SiO2/CdS) was quenched by the addition of trialkylamines, the degree being dependent on their molecular size. These facts were attributable to the molecular-size-selective penetration of quencher molecules from the bulk solution to the void space through the pores of the SiO2 shell of the jingle-bell-shaped nanoparticles.The prepared jingle-bell-shaped semiconductor nanoparticles seemed to be promising materials for light energy conversion owing to the less amount of recombination sites in the particles, because these exhibited the strong photoluminescence. The jingle-bell-shaped SiO2/CdS particles exhibited much higher photocatalytic activities than those of commercially available bulk CdS particles. For the photoreduction of nitrobenzene, especially, the yield and selectivity of the reduction products could be varied by changing the nanostructure of photocatalysts used. Less