Temperature Effect of Photoluminescence from Aqueous CdSe Quantum Dots

Thiol-capped CdSe quantum dots are synthesized rapidly in aqueous solution assisted by microwave irradiation without any poisonous materials. The growth rate of quantum dots is greatly enhanced in this current microwave synthesis. The narrow size distribution (~30nm) of CdSe quantum dots is similar to the oil samples. The results indicate that the photoluminescence quality of quantum dots is improved effectively assisted by microwave irradiation compared to traditional aqueous solution. Room and low temperature photoluminescence is employed to investigate the excitonic emission from thiol-capped CdSe quantum dots between 83K and 300K. The photoluminescence peak position of CdSe quantum dots shift to shorter wavelengths. The relationship between the shift wavelengths and the temperature is linear. The slope for linear fitting curve is nearly constant in repeated experiment. This implies CdSe quantum dots may be applied in the low temperature nano-sensor. The photoluminescence intensity first enhances and then quench with decrease of temperature. The temperature dependence of the photoluminescence intensity is demonstrated through thermal escape and thermal rectification of surface trap states.