Preparation of Semiconductor Nanoparticle-Assembled Layers Having Desired Photoluminescent Properties

我们开发了制备二氧化硅包覆的半导体纳米颗粒复合材料的新策略，该复合材料具有理想的光化学性质。采用逐层堆积技术可以制备纳米复合材料的颗粒层。首先，利用尺寸选择光刻技术对二氧化硅包裹的硒化镉纳米颗粒(SiO_2/CdSe)进行尺寸选择光刻，以精确控制其光致发光性能。虽然制备的SiO_2/CdSe没有光致发光，但尺寸选择性光刻导致了禁带发射的发展，且程度随着光刻的进行而增强。部分光刻的SiO_2/cdSe纳米颗粒薄膜在光刻区域产生了强烈的带隙发射，而其余的SiO_2/cdSe纳米颗粒薄膜没有表现出d-…。光致发光能力更强，在紫外光照射下可形成清晰的光致发光图像。该技术使得通过使用单一源材料用具有不同波长的单色光照射来产生多色光致发光图像成为可能。其次，通过加入三烷基胺对铃铛状二氧化硅包裹的硫化镉纳米颗粒(SiO_2/CDS)的光致发光进行猝灭，猝灭程度与其分子大小有关。这归因于猝灭剂分子从体液到空隙的分子尺寸选择性渗透到铃铛状纳米粒子的SiO_2壳层的孔隙中。由于铃声铃状半导体纳米粒子中复合位置的数量较少，因此它们表现出强烈的光致发光，因此似乎是一种很有前途的光能转换材料。铃铛状二氧化硅/硫化镉颗粒的光催化活性远高于市售块状硫化镉颗粒。特别是对硝基苯的光还原，可以通过改变光催化剂的纳米结构来改变还原产物的产率和选择性。较少

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