Two-phase thermal method for preparation of cadmium sulfide quantum dots

摘要

The present invention relates to a two-phase thermal method for the preparation of cadmium sulfide quantum dots. In the method, cadmium carboxylate containing 2 to 18 carbon atoms or cadmium oxide is selected as cadmium source; thiourea or thioacetamide is selected as sulfur source; oleic acid or trioctylphosphine oxide (TOPO) is selected as capping agent, and molar ratio of cadmium source to sulfur source is in a range of from 10:1 to 1:10, and molar ratio of cadmium source to capping agent is in a range of from 1:7 to 1:25. Water and water-insoluble organic compound in equal or similar volume are used as solvents forming a two-phase system. The mixture is heated at 120-180° C. in an autoclave for 0.5 to 24 hrs. By means of varying reaction time, cadmium sulfide quantum dots of different sizes could be prepared. Alternatively, it is also feasible to use quantum dots already obtained as crystal seeds in the reaction of newly added reaction precursor to give larger sized quantum dots with a size distribution similar to that of the initial crystal seeds so as to realize the control of quantum dot size. The quantum dots obtained in the present invention have relatively narrow size distribution, emit royal purple or blue light under ultraviolet lamp, with a photoluminescence quantum efficiency of from 3 to 60%.