水溶性CdTe量子点的稳态和纳秒时间分辨光致发光光谱

报道了以飞秒脉冲激光为激发光源的水溶性CdTe量子点(QDs)的稳态荧光光谱和纳秒时间分辨荧光光谱.实验发现CdTe量子点的荧光光谱峰值位置随激发波长变化发生明显移动，激发脉冲波长越长，荧光峰位红移越大.荧光动力学实验数据显示，在400nm和800nm脉冲激光激发下，水溶性CdTe量子点的荧光光谱中均含有激子态和诱捕态两个衰减成分，两者的发射峰相距很近，诱捕态的发射峰波长较长.在800nm脉冲激光激发下的诱捕态成分占总荧光强度的比重比400nm激发下的约高3倍，其相对强度的这种变化导致了稳态荧光发射峰位的红移. 关键词： CdTe 量子点 时间分辨 荧光光谱 上转换荧光

Steady-state and nanosecond time-resolved photoluminescence spectroscopies of aqueous CdTe quantum dots

We have used femtosecond laser pulse to investigate the steady-state and nanosecond time-resolved photoluminescence of aqueous CdTe quantum dots (QDs). Up-conversion luminescences of the CdTe QDs induced by two-photon excitation were observed. Compared with 400nm excitation, the peak wavelength of photoluminescence induced by 1208nm excitation was red-shifted about 28nm (88meV). The decay kinetics showed a fast and a slow decay component which can be assigned to band-edge excitonic state (3—5ns) and surface trapping state (30—50ns), respectively. Luminescence and up-conversion luminescence at room temperature showed similar decay kinetics. The relative change of photoluminescence intensity between excitonic and trapping state is responsible for the red shift of emission peak. It was found that the proportion of excitonic emission in whole luminescence at 400nm excitation is bigger than that of excitonic emission at 800nm excitation, so with increasing the wavelength of laser excitation steady state spectra have the red shift of emission peaks.