Correlation of Quantum Dot Photophysics and Structure with Atomic Precision

本研究旨在阐明核/壳纳米晶体（量子点）的原子结构如何影响其光物理特性。在这项工作中，范德比尔特大学的Sandra Rosenthal教授和James McBride教授利用现代化学技术合成了不同成分和壳层覆盖的量子点，然后将通过像差校正扫描透射电子显微镜（STEM）进行原子分辨率成像。此外，这些结构将利用单纳米晶体光谱和超快荧光上转换光谱进行表征，以获得除激子动力学外的闪烁统计数据。最终，将开发执行相关单纳米晶体光谱和像差校正STEM的方法，以精确确定哪些特定纳米结构提供最高的荧光产率、光稳定性和减少闪烁；在集合测量中丢失的信息。利用最先进的电子显微镜结合单分子荧光技术将澄清壳覆盖和组成的真实效果。这将直接影响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。荧光探针的改进将为药物发现应用带来更高的灵敏度，并允许在单分子水平上直接测量生物动力学。此外，完善量子点设计将大大提高量子点固态照明器件的效率和寿命。本科研究将在纳米晶体的合成和表征中发挥不可或缺的作用，同时培养学生对如何设计、实施实验以及如何解释和呈现数据的理解。将为范德比尔特学生科学志愿者组织（VSVS）开发一套演示大小相关量子点荧光的工具包，作为“纳米”的介绍。该组织去年安排了400多次课堂参观，并将通过NSF EPSCoR奖扩展到田纳西州农村地区。

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.