Figure 2

Optical performance of CdTe cores and corresponding CdTe/CdSe type II QDs by means of microwave-assisted synthesis. The optical performance of a series of original CdTe cores and corresponding CdTe/CdSe type II QDs by means of microwave-assisted synthesis. The QD samples are excited at their first excitation absorption peak, and The PL intensities of all the samples are normalized. (a) Fluorescence spectra of CdTe cores (black line) and CdTe/CdSe core/shell QDs with controlled reaction time under microwave irradiation, giving rise to the different CdSe shell thickness surrounding the CdTe core. The molar ratio of [Cd²⁺]/[MPA]/[Se^2-] was set as 1:2.4:1, the concentration of Cd²⁺ was fixed at 1.25 mM, reaction temperature at about 100°C, and reaction time range from 2 min to approximately 20 min. (b) Fluorescence decay curves of a CdTe core (black line) and the CdTe/CdSe core/shell QDs (red line). The lifetimes were recorded at the maxima of the emission with the excitation wavelength of 371 nm. The inset picture indicates the fluorescence spectra of the corresponding QDs. The decay lifetime increases dramatically due to the coating of CdSe shell (reaction time of about 5 min under microwave irradiation).