Photoluminescence quenching and intensity fluctuations of CdSe-ZnS quantum dots on an Ag nanoparticle film
Photoluminescence quenching and intensity fluctuations of CdSe-ZnS quantum dots on an Ag nanoparticle film
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DOI：
10.1021/jp076659
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发表时间：
2008-02-07
影响因子：
3.7
通讯作者：
Biju, Vasudevanpillai
中科院分区：
文献类型：
--
作者：
Matsumoto, Yuusuke;Kanemoto, Ryodai;Biju, Vasudevanpillai
当置于银纳米颗粒（NP）膜上时，单CdSe/ZnS量子点（QD）的间歇“开”和“关（闪烁）光致发光（PL）被修改成具有非零强度“关”（伪关）周期的随机波动。此外，量子点的PL量子效率（从0.42到0.22）和寿命（从5.2到1.5 ns）显着降低在系综水平的存在下的银纳米粒子，和单量子点的PL寿命的直方图移动（从4.2到1.7 ns）和锥形（半高全宽从3.3到1.1 ns）时，放置在银纳米粒子膜。荧光量子效率的猝灭和荧光寿命的降低归因于从光激发量子点到银纳米颗粒的超快能量转移。能量转移过程与激子弛豫竞争，并影响表面缺陷态（带隙缺陷）和俄歇弛豫中的载流子捕获，这被认为是闪烁的起源。表面态对改性PL的贡献被确定为从降低的贡献的缓慢组件的PL衰减的合奏和单量子点在银纳米粒子的存在下。基于系综平均光致发光强度和寿命以及单量子点寿命和强度轨迹的分析，我们提出从光激发量子点到银纳米颗粒的能量转移过程导致弛豫过程的重新分布，并为单量子点提供了非零强度的涨落轨迹。除了观察到的修改闪烁和窄寿命分布的量子点，目前的工作部分支持了马库斯和同事提出的模型，闪烁是与本地化的电荷载流子的缺陷。
Intermittent "on" and "off (blinking) photoluminescence (PL) of single-CdSe/ZnS quantum dots (QDs) is modified when placed on an Ag nanoparticle (NP) film into stochastic fluctuations with nonzero intensity "off" (pseudo off) periods. Also, the PL quantum efficiency (from 0.42 to 0.22) and lifetime (from 5.2 to 1.5 ns) of QDs are considerably decreased at ensemble level in the presence of Ag NPs, and a histogram of the PL lifetime of single-QDs is shifted (from 4.2 to 1.7 ns) and tapered (full width at half-maximum from 3.3 to 1.1 ns) when placed on an Ag NP film. The quenching of the PL quantum efficiency and decrease of the PL lifetime are attributed to ultrafast energy transfer from photoexcited QDs to Ag NPs. The energy-transfer process competes with exciton relaxations and influences carrier trapping in surface defect-states (band gap defects) and Auger relaxation, which are considered to be the origins of blinking. The contribution of surface-states on the modified PL was identified from decreased contribution of a slow component to the PL decays of ensemble- and single-QDs in the presence of Ag NPs. On the basis of ensemble averaged PL intensity and lifetime and single-QD lifetime and intensity trajectory analyses, we propose that the energy-transfer process from photoexcited QDs to Ag NPs result a redistribution of relaxation processes and provide fluctuating trajectories with nonzero intensities to single-QDs. Apart from the observations of modified blinking and narrow lifetime distribution of QDs, the current work partially supports a model proposed by Markus and co-workers that blinking is related to localization of charge carriers in defects.