Dey Swayandipta, Zhou Yadong, Tian Xiangdong, Jenkins Julie A, Chen Ou, Zou Shengli, Zhao Jing
Department of Chemistry, University of Connecticut, 55 North Eagleville Rd, Storrs, CT 06269-3060, USA.
Nanoscale. 2015 Apr 21;7(15):6851-8. doi: 10.1039/c5nr00274e.
In this work, we systematically investigated the plasmonic effect on blinking, photon antibunching behavior and biexciton emission of single CdSe/CdS core/shell quantum dots (QDs) near gold nanoparticles (NPs) with a silica shell (Au@SiO2). In order to obtain a strong interaction between the plasmons and excitons, the Au@SiO2 NPs and CdSe/CdS QDs of appropriate sizes were chosen so that the plasmon resonance overlaps with the absorption and emission of the QDs. We observed that in the regime of a low excitation power, the photon antibunching and blinking properties of single QDs were modified significantly when the QDs were on the Au@SiO2 substrates compared to those on glass. Most significantly, second-order photon intensity correlation data show that the presence of plasmons increases the ratio of the biexciton quantum yield over the exciton quantum yield (QYBX/QYX). An electrodynamics model was developed to quantify the effect of plasmons on the lifetime, quantum yield, and emission intensity of the biexcitons for the QDs. Good agreement was obtained between the experimentally measured and calculated changes in QYBX/QYX due to Au@SiO2 NPs, showing the validity of the developed model. The theoretical studies also indicated that the relative position of the QDs to the Au NPs and the orientation of the electric field are important factors that regulate the emission properties of the excitons and biexcitons of QDs. The study suggests that the multiexciton emission efficiency in QD systems can be manipulated by employing properly designed plasmonic structures.
在这项工作中，我们系统地研究了等离子体激元对单个CdSe/CdS核壳量子点（QDs）在具有二氧化硅壳的金纳米颗粒（NPs）（Au@SiO2）附近的闪烁、光子反聚束行为和双激子发射的影响。为了获得等离子体激元和激子之间的强相互作用，选择了适当尺寸的Au@SiO2 NPs和CdSe/CdS QDs，以使等离子体激元共振与QDs的吸收和发射重叠。我们观察到，在低激发功率 regime 下，与在玻璃上相比，当QDs位于Au@SiO2衬底上时，单个QDs的光子反聚束和闪烁特性发生了显著改变。最显著的是，二阶光子强度相关数据表明，等离子体激元的存在增加了双激子量子产率与激子量子产率的比值（QYBX/QYX）。建立了一个电动力学模型来量化等离子体激元对QDs双激子的寿命、量子产率和发射强度的影响。由于Au@SiO2 NPs，实验测量和计算得到的QYBX/QYX变化之间取得了良好的一致性，表明所建立模型的有效性。理论研究还表明，QDs相对于Au NPs的相对位置和电场方向是调节QDs激子和双激子发射特性的重要因素。该研究表明，通过采用适当设计的等离子体激元结构，可以操纵QD系统中的多激子发射效率。
