Blinking Suppression in CdSe/ZnS Single Quantum Dots by TiO2 Nanoparticles
Blinking Suppression in CdSe/ZnS Single Quantum Dots by TiO2 Nanoparticles
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DOI：
10.1021/nn100698u
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发表时间：
2010-08-01
期刊：
影响因子：
17.1
通讯作者：
Biju, Vasudevanpillai
中科院分区：
文献类型：
--
作者：
Hamada, Morihiko;Nakanishi, Shunsuke;Biju, Vasudevanpillai
半导体量子点的光致发光和单分子的荧光间歇地打开和关闭，这种现象被称为闪烁。在量子点中，闪烁是间歇性俄歇电离的结果，这导致形成带正电的量子点。由于强库仑相互作用，带电量子点的连续光活化导致非辐射载流子复合，在强度轨迹中诱导长寿命的OFF状态。闪烁是量子点应用于单分子成像和单光子逻辑器件的不期望的特性。在这里，我们报告显着的闪烁抑制的CdSe/ZnS单量子点的存在下，二氧化钛纳米粒子。在这项工作中，我们连续记录光致发光强度轨迹的单量子点和没有二氧化钛纳米粒子。有趣的是，一旦引入TiO 2纳米颗粒溶液，共价连接在盖玻片上并浸入水中的单个量子点的强度轨迹就会导致几乎完全的闪烁抑制。闪烁抑制与光致发光强度的降低，但没有相当大的变化，在光致发光寿命，表明量子点中的非辐射载流子复合被引导到电子转移到二氧化钛纳米粒子和背电子转移到量子点。基于这些实验和最近关于从量子点到TiO 2纳米颗粒的光诱导电子转移的报道，我们假设量子点的闪烁可以通过与明确定义的电荷载流子陷阱（例如电子受体）接口来增加其中性状态的非辐射再生速率来抑制，其在俄歇电离期间接受电子并通过反向电子转移来中和带电量子点。闪烁抑制和电子转移之间的相关性在量子点-TiO 2纳米颗粒系统中可能具有重要的意义，对于制备不闪烁的量子点用于连续和按需发光，用于高效太阳能收集的供体-受体系统，以及用于量子光学器件的混合半导体材料。
The photoluminescence of semiconductor quantum dots and fluorescence of single molecules intermittently turn ON and OFF, a phenomenon referred to as blinking. In quantum dots, blinking occurs as a result of intermittent Auger ionization, which results in the formation of positively charged quantum dots. Due to strong Coulombic interactions, successive photoactivation of a charged quantum dot results in nonradiative carrier recombination, inducing long-lived OFF states in the intensity trajectories. Blinking is an undesirable property with respect to applications of quantum dots toward single-molecule imaging and single-photon logic devices. Here we report significant blinking suppression for CdSe/ZnS single quantum dots in the presence of TiO2 nanoparticles. In this work, we continuously recorded photoluminescence intensity trajectories of single quantum dots with and without TiO2 nanoparticles. Interestingly, the intensity trajectory of a single quantum dot that was covalently tethered on a cover glass and dipped in water resulted in near-complete blinking suppression as soon as a TiO2 nanoparticle solution was introduced. The blinking suppression was associated with a decrease in the photoluminescence intensity but without considerable changes in the photoluminescence lifetime, indicating that nonradiative carrier recombination in quantum dots was channeled into electron transfer to TiO2 nanoparticles and back electron transfer to quantum dots. On the basis of these experiments and recent reports on photoinduced electron transfer from quantum dots to TiO2 nanoparticles, we hypothesize that blinking of a quantum dot can be suppressed by increasing the rate of nonradiative regeneration of its neutral state by interfacing with a well-defined charge carrier trap such as an electron acceptor, which accepts an electron during Auger ionization and neutralizes the charged quantum dot by back electron transfer. Correlation between blinking suppression and electron transfer in a quantum dot-TiO2 nanoparticle system may have important implications, for the preparation of nonblinking quantum dot for incessant and on-demand light emission, donor-acceptor systems for efficient solar energy harvesting, and hybrid semiconductor materials for quantum optical devices.