School of Electronic Engineering, Heilongjiang University, Harbin 150080, Peoples Republic of China.
Nanoscale Res Lett. 2012 Jun 8;7(1):301. doi: 10.1186/1556-276X-7-301.
The yellow- and red-emitting CdSeS nanocrystals (NCs) synthesized through one-step organometallic synthesis method are uniformly assembled in polymethyl methacrylate (PMMA). A higher-energy emission band originates from band-edge excitonic state appeared at low temperature. With the Se dopant concentration increasing, the luminescent spectra of CdSeS NCs have a red-shifted emission peak and a shorter luminescent lifetime, which is attributed to the existence of trapping state caused by surface defect and Se dopant. CdSeS NC shows a shorter luminescence lifetime and higher energy emission peak in PMMA matrix than that in toluene, indicating that the former is more favorable to transfer energy through exciton-phonon coupling. The upconversion luminescence (UCL) is observed using 800 nm femtosecond laser excitation. The pump power dependence demonstrated UCL spectra of yellow-emitting CdSeS NCs has a slope of 2.2, while that of red-emitting CdSeS NCs has a slope of 1.4. The results demonstrate that the two-photon absorption plays a dominating role when Se concentration of CdSeS NCs is lower, while phonon-assisted UCL by one-photon excitation gradually takes place with the amount of Se dopants increasing.
通过一步有机金属合成法合成的黄-红发射 CdSeS 纳米晶体 (NCs) 均匀地组装在聚甲基丙烯酸甲酯 (PMMA) 中。低温下出现的源于带边激子态的高能发射带。随着 Se 掺杂浓度的增加，CdSeS NCs 的发光光谱具有红移的发射峰和较短的荧光寿命，这归因于表面缺陷和 Se 掺杂引起的陷获态的存在。CdSeS NC 在 PMMA 基质中的荧光寿命和能量发射峰比在甲苯中更短，表明前者更有利于通过激子-声子耦合进行能量转移。使用 800nm 飞秒激光激发观察到上转换发光 (UCL)。泵浦功率依赖性表明，黄色发射 CdSeS NCs 的 UCL 光谱斜率为 2.2，而红色发射 CdSeS NCs 的斜率为 1.4。结果表明，当 CdSeS NCs 的 Se 浓度较低时，双光子吸收起主导作用，而随着 Se 掺杂量的增加，通过单光子激发的声子辅助 UCL 逐渐发生。
