Varghese Neenu, Biswas Kanishka, Rao C N R
Chemistry and Physics of Materials Unit, DST Nanoscience Unit and CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P. O, Bangalore 560064, India.
Chem Asian J. 2008 Sep 1;3(8-9):1435-42. doi: 10.1002/asia.200800119.
The growth of capped CdSe and CdS nanocrystals formed by the reaction of selenium or sulfur with cadmium stearate in toluene solution in the presence of dodecanethiol or trioctylphosphine oxide and tetralin, has been investigated by a variety of techniques to obtain reliable data. Whereas small angle X-ray scattering has provided statistically satisfactory data on the variation of size distribution with time, TEM has been used as a direct probe of the particle size, although with a limited sampling size. UV/Vis and photoluminescence spectroscopies have also provided information about the time evolution of the average diameter (D) of the nanocrystals. By employing all these techniques, we have obtained the D(t) data and fitted then to various growth models. Although certain qualitative observations suggest growth of the nanocrystals to be controlled by diffusion-limited Ostwald ripening, we have found it is necessary to include the surface reaction term in the growth equation. Thus, the growth of CdSe and CdS nanocrystals has contributions from both diffusion and surface reaction, with a D(3)+D(2) type behavior, independent of the capping agent.
通过多种技术研究了在十二硫醇或三辛基氧化膦以及四氢化萘存在下，硒或硫与硬脂酸镉在甲苯溶液中反应形成的 capped CdSe 和 CdS 纳米晶体的生长情况，以获取可靠数据。小角 X 射线散射提供了关于尺寸分布随时间变化的统计上令人满意的数据，而透射电子显微镜（TEM）已被用作颗粒尺寸的直接探测手段，尽管采样尺寸有限。紫外/可见光谱和光致发光光谱也提供了有关纳米晶体平均直径（D）随时间演变的信息。通过运用所有这些技术，我们获得了 D(t) 数据并将其拟合到各种生长模型。尽管某些定性观察表明纳米晶体的生长受扩散限制的奥斯特瓦尔德熟化控制，但我们发现有必要在生长方程中纳入表面反应项。因此，CdSe 和 CdS 纳米晶体的生长既有扩散的贡献也有表面反应的贡献，呈现 D(3)+D(2) 类型的行为，且与封端剂无关。
