Excitation wavelength and intensity dependence of photo-spectral blue shift in single CdSe/ZnS quantum dots

The influence of excitation wavelength and intensity on core/shell CdSe/ZnS quantum dots (QDs) photo-spectral blue shift was investigated by spectral imaging. Analysis of the evolution of the distance between the zeroth-order spot and the first-order spectral streak, we found that the extent of blue shift strongly depends on the excitation wavelength and QDs sizes, but not on the excitation intensity. Converted the extent of blue shift into the decreased QDs volume at a series of time, the core oxidation kinetics of CdSe/ZnS QDs was uncovered that provided a quantitative comparison method for study the excitation wavelength and intensity dependence of single QDs blue shift. The core oxidation rate is almost proportional to the excitation intensity. These results are explained by a fact that higher energy excitation wavelength can accelerate individual exciton formation and higher excitation intensity can induce more amount of exciton formation per a unit time