银溶胶均相成核过程的研究

利用紫外光谱测定了柠檬酸钠还原硝酸银制备银溶胶的成核诱导期,考察了溶液温度和过饱和度对反应诱导期的影响.结合均相成核理论,得到当溶液的过饱和浓度大于或等于4×108时体系为均相成核过程.结果表明,诱导期随着温度和过饱和浓度的上升而下降.同时计算出不同反应温度下纳米银的固-液界面张力,并与经验理论模型的数据结果加以比较,实验预测结果低于模型值.本实验通过测定银溶胶制备过程中银离子的浓度变化验证了紫外光谱测定反应诱导期的可行性.

Study on homogeneous nucleation of silver colloids

Induction time of silver colloids primary nucleation was determined by UV-Vis spectra,silver colloids were synthesized by a reaction of silver nitrate and sodium citrate.The effects of temperature and supersaturation(S) on induction time were considered.The results show that induction time decreases with increasing supersaturation and temperature.According to the classical theory of homogeneous nucleation,the primary nucleation of reaction was a homogeneous nucleation when S ≥ 4×108.Interfacial tensions between solid and liquid were estimated at different temperatures and compared with an empirical correlation for calculation of interfacial tension.The estimated values of the interfacial tension are lower than the values predicted by the empirical correlation.In this paper,the concentration of silver ion in the process of nucleation was also determined by UV-Vis spectra and it validates the method for measuring induction time by monitoring the adsorption of the colloids.