非配位性溶剂中CdS纳米颗粒的生长动力学及其机理研究

Nucleation and Growth Kinetics of CdS Nanocrystals Synthesized in Non-coordinating Solvent

本文以氧化镉为镉源，硫单质为硫源，油酸为配体，在十八烯体系中合成单分散的CdS纳米颗粒。通过改变油酸的浓度，研究了油酸对颗粒的生长动力学、颗粒尺寸分布以及颗粒浓度的影响。所得到的CdS纳米颗粒直径从2．2—4．5nm变化，最大荧光发射波长为450nm。在油酸浓度为297M，反应时间为60min左右时，所得到的CdS颗粒直径为4．5nm，而颗粒浓度仅为10^-5M；在油酸浓度为42mM时，实际可得到的CdS颗粒的直径可小至2．2nm，反应溶液中颗粒的平均浓度可达到8×10^-5M左右。研究表明，油酸浓度增大，使初始成核速度加快，反应平衡时所得到的纳米颗粒直径较大，但是颗粒数目显著减少，并且尺寸分布也有所增宽。

CdS nano-erystals were synthesized in octadecanoic olefin system, a non-coordinating solvent, using cadmium oxide as Cd precursors, sulfur powder as S precursors and oleic acid as capping agent. The effects of oleic acid concentration on growth kinetics, size and size dispersion were investigated through changing the oleic acid concentration in the reaction system. In this study, the diameters of CdS nanocrystals varied from 2.2 to 4.5nm, and the corresponding fluorescence emission peaks lied in 390 to 450 nm, respectively. When the concentration of oleic acid is as high as 287mM at the moment of 60min after sulfur precursor injection, the average diameter of obtained nanocrystals could reach 4.5nm,and the actual nucleation concentration was only 10^-5 M. When the oleic acid concentration was decreased to 42mM, the actually nucleation concentration of CdS nanocrystals was about 8 × 10^-5M. The nanocrystals of 2.2nm diameter could be obtained during the initial of nucleation. The results indicate that the initial nucleation rate speeds up significantly with the oleic acid concentration increasing. The higher oleic acid concentration in the reaction system is, the larger the size of resulted nanocrystals. Nevertheless, the nucleation number is less, but the size distribution is broader in the solution with high oleic acid concentration than ones with low oleic acid concentration.