Materials Functions in Nanometer Particles

纳米半导体和氧化物粒子的合成主要采用浮选法、乳液法或反胶束法制备。针对特定的材料功能，分析了它们的物理化学性质。Fe304的大小不仅受合成条件的控制，而且还可以用液相色谱来控制，合成的Fe304颗粒的直径在4~20 nm之间。这些颗粒在溶液中与表面活性剂反应，通过浮选只选择最小尺寸的5 nm颗粒。它们的大小和形状足够均匀，以在衬底上形成规则的二维排列。在100Oe下的磁测量表明，阻挡温度为15K，这是由表面自旋无序产生的各向异性能解释的。利用反胶束技术可以制备出尺寸为1.3 nm的小颗粒CdSe。光学测量表明，蓝移到415 nm的量子尺寸效应很大，而块体的量子尺寸效应为700 nm。吸收光谱与有效质量近似的球形量子阱模型的预测结果吻合较好。我们还制备了CeO2和ZnO等样品，并根据它们的大小和形状分析了它们的光催化反应等各种光化学效应。

Nanometer-scale semiconductor and oxide particles are synthesized by solution methods with flotation, emulsion, or reverse micelle technique. Their physical and chemical properties are analyzed for specific materials functions. Sizes are controlled not only by synthesis conditions but also by making use of liquid chromatography.Small particles of Fe304 are synthesized in their diameter ranging from 4 to 20 nm. These particles are reacted with surfactants in solution and only smallest size particles of 5 nm are selected by flotation. Their size and shape are sufficiently uniform to form regular arrangement in two-dimension on a substrate. Magnetic measurements at 100 Oe show the blocking temperature of 15 K explained by the anisotropy energy coming form surface spin disorder around the surface.Small particles of CdSe of size as small as 1.3 nm are produced by reverse micelle technique. Optical measurements show a large quantum-size effect of blue shift to 415 nm as compared with 700 nm of the bulk. Absorption spectra are in good agreement with prediction by the spherical quantum well model with effective mass approximation.Other samples such as CeO2 and ZnO are also produced and their various photochemical effects such as photo-catalytic reactions are analyzed in terms of their size and shape.