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利用400nm和800nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400nm激发下的荧光峰相比蓝移最多达15nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdTe/CdS核壳量子点荧光由带边激子态和诱捕态两种成分组成,两种成分峰位不同,带边激子态波长较短,诱捕态波长较长.800nm激发与400nm激发时相比,激子态相对比重增加,这导致荧光峰的蓝移.
CdTe and CdTe / CdS core-shell quantum dot sols were excited by low-intensity femtosecond laser beams of different wavelengths at 400 nm and 800 nm to study their steady-state and time-resolved fluorescence properties. CdTe and CdTe / CdS nuclei The quantum dots of the shell produce upconversion luminescence, and the upconversion fluorescence peak is blue-shifted by up to 15 nm compared to the fluorescence peak at 400 nm excitation, and the blue-shift value is related to the fluorescence quantum yield. Variable power excitation Confirms the difference between the excitation light power and the upconversion fluorescence The results of time-resolved fluorescence show that the fluorescence kinetic curve obeys the double-e-exponential decay, and the surface-state-assisted two-photon absorption model is the main mechanism of up-conversion luminescence with low excitation intensity.CdTe and CdTe / CdS nuclei The quantum dot fluorescence of the shell consists of exciton states and entrapment states, with different peak positions of the two components, shorter band-edge exciton wavelength and longer trapping wavelength. Compared with excitation at 400 nm, The relative weight of the daughter state increases, which results in a blue shift of the fluorescence peak.