Gong Hong-Mei, Zhou Zhang-Kai, Song Hao, Hao Zhong-Hua, Han Jun-Bo, Zhai Yue-Ying, Xiao Si, Wang Qu-Quan
Department of Physics, Wuhan University, Wuhan, China.
J Fluoresc. 2007 Nov;17(6):715-20. doi: 10.1007/s10895-007-0223-z. Epub 2007 Aug 10.
To investigate the influence of surface trapping and dark states on CdSe and CdSe/ZnS quantum dots (QDs), we studied the absorption, fluorescence intensity and lifetime by using one-and two-photon excitation, respectively. Experimental results show that both one- and two-photon fluorescence emission efficiencies of the QDs enhance greatly and the lifetime increase after capping CdSe with ZnS due to the effective surface passivation. The lifetime of one-photon fluorescence of CdSe and CdSe/ZnS QDs increase with increasing emission wavelength in a supralinear way, which is attributed to the energy transfer of dark excitons. On the contrary, the lifetime of two-photon fluorescence of bare and core-shell QDs decrease with increasing emission wavelength, and this indicates that the surface trapping is the dominant decay mechanism in this case.
为了研究表面俘获和暗态对CdSe和CdSe/ZnS量子点（QDs）的影响，我们分别使用单光子和双光子激发研究了其吸收、荧光强度和寿命。实验结果表明，由于有效的表面钝化，用ZnS包覆CdSe后，量子点的单光子和双光子荧光发射效率均大大提高，寿命增加。CdSe和CdSe/ZnS量子点的单光子荧光寿命随发射波长的增加呈超线性增加，这归因于暗激子的能量转移。相反，裸量子点和核壳量子点的双光子荧光寿命随发射波长的增加而减小，这表明在这种情况下表面俘获是主要的衰减机制。
