Correlation of Quantum Dot Photophysics and Structure with Atomic Precision

本研究旨在阐明核壳纳米晶(量子点)的原子结构对其光物理的影响。在这项工作中，范德比尔特大学的桑德拉·罗森塔尔教授和詹姆斯·麦克布莱德教授利用现代化学技术合成了不同组成和壳层覆盖率的量子点，然后通过像差校正的扫描透射式电子显微镜(STEM)以原子分辨率成像。此外，这些结构将利用单纳米晶体光谱以及超快荧光上转换光谱来表征，以获得除了激子动力学之外的闪烁统计数据。最终，将开发进行相关单纳米晶体光谱和校正像差的STEM的方法，以便准确确定哪些特定纳米结构提供最高的荧光产量、光稳定性和减少眨眼；这些信息在整体测量中丢失。结合使用最先进的电子显微镜和单分子荧光技术，将澄清外壳覆盖率和成分的真实效果。这将对利用量子点荧光作为生物探针的商业应用以及目前将高荧光和稳定的量子点用于固态照明的努力产生立竿见影的影响。荧光探针的改进将导致药物发现应用的更高灵敏度，并允许在单分子水平上直接测量生物动力学。此外，完善的量子点设计将极大地提高基于量子点的固态照明设备的效率和寿命。本科生的研究将在纳米晶体的合成和表征中发挥不可或缺的作用，同时促进对如何设计、实施实验以及如何解释和呈现数据的理解。范德比尔特学生科学志愿者组织(VSVS)将为范德比尔特学生科学志愿者组织(VSVS)开发一套演示与尺寸有关的量子点荧光的试剂盒，作为对“Nano”的介绍。该组织去年安排了400多次课堂访问，并将通过NSF EPSCoR奖推广到田纳西州农村。

This research aims to elucidate how the atomic structure of core/shell nanocrystals (quantum dots) impacts their photophysics. In this work, Prof. Sandra Rosenthal and Prof. James McBride of Vanderbilt University leverage modern chemical techniques to synthesize quantum dots of varying composition and shell coverage, which will then be imaged with atomic resolution via aberration-corrected scanning transmission electron microscopy (STEM). Further, these structures will be characterized utilizing single nanocrystal spectroscopy as well as ultrafast fluorescence upconversion spectroscopy to obtain blinking statistics in addition to exciton dynamics. Ultimately, methodologies to perform correlated single nanocrystal spectroscopy and aberration-corrected STEM will be developed in order to precisely determine which specific nanostructures provide the highest fluorescence yield, photostability and reduced blinking; information that is lost in ensemble measurements. The utilization of state-of-the-art electron microscopy in conjunction with single molecule fluorescence techniques will clarify the true effect of shell coverage and composition. This will have immediate impact on commercial applications utilizing quantum dot fluorescence as biological probes and current efforts to incorporate highly fluorescent and stable quantum dots for solid-state lighting. Improvement in fluorescent probes will lead to higher sensitivity for drug discovery applications as well as allowing for direct measurements of biological dynamics at the single molecule level. Additionally, perfecting quantum dot design will greatly enhance the efficiency and extend the lifetime of quantum dot-based solid state lighting devices. Undergraduate research will play an integral role in the synthesis and characterization of the nanocrystals, while fostering an understanding of how to devise, implement an experiment, and how to interpret and present data. A kit demonstrating the size-dependent quantum dot fluorescence as an introduction to 'nano' will be developed for the Vanderbilt Students Volunteers for Science organization (VSVS), which arranged more than four hundred classroom visits last year and will be extended to rural TN via an NSF EPSCoR award.