Ultrafast Charge Transfer and Trapping Dynamics in a Colloidal Mixture of Similarly Charged CdTe Quantum Dots and Silver Nanoparticles
Ultrafast Charge Transfer and Trapping Dynamics in a Colloidal Mixture of Similarly Charged CdTe Quantum Dots and Silver Nanoparticles
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DOI：
10.1021/acs.jpcc.5b08630
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发表时间：
2016-01-14
影响因子：
3.7
通讯作者：
Samanta, Anunay
中科院分区：
文献类型：
--
作者：
Mondal, Navendu;Samanta, Anunay
研究了胶体CdTe量子点和银纳米粒子之间的相互作用，确定了表面电荷和外延耦合对实现金属半导体纳米复合材料潜在活性的重要性。这两个相似带电物种之间出人意料的强相互作用从银纳米粒子对量子点激子发射的戏剧性猝灭中可见一斑。在瞬时吸收测量中，从量子点第一激子带的加速漂白恢复和载流子冷却的加速获得了从光激发的量子点到银纳米粒子的电子转移的直接证据。在可见光-近红外区观察到一个新的正的瞬时正吸收，证明了电荷载流子捕获的证据，而这是孤立的载流子所没有的。核/壳(CdTe/ZnS)量子点的类似测量结果进一步证实了电子转移和电荷载流子捕获过程。由于超快电荷载流子(尤其是空穴)捕获减缓了电荷复合过程，本发现为利用太阳能和利用这些胶体混合物提高光催化活性开辟了新的可能性。
The interaction between colloidal CdTe quantum dots (QDs) and silver nanoparticles (Ag NPs), both in their negatively charged state, is studied to determine the importance of surface charge and epitaxial coupling of the two components to achieve the potential activity of the metalsemiconductor nanocomposites. An unexpected strong interaction between the two similarly charged species is evident from dramatic quenching of the excitonic emission of the QDs by the Ag NPs. Direct evidence of electron transfer from the photoexcited QDs to Ag NPs is obtained from an accelerated bleach recovery of the first exciton band of the QDs and a faster carrier cooling in the presence of Ag NPs in transient absorption measurements. The evidence of charge carrier trapping is demonstrated by the observation of a new broad positive transient absorption in the visible-near-infrared region, which was absent in their isolated counterparts. The electron transfer and charge carrier trapping processes are further substantiated by the results of similar measurements on core/shell (CdTe/ZnS) QDs. As ultrafast charge carrier (especially the hole) trapping slows the charge recombination process, the present findings open up new possibilities of harnessing solar energy and improving the photocatalytic activity by employing these colloidal mixtures.