Collaborative Research: Nanoscale Charge Transfer in Quantum Dots Connected with Molecular Switches

该项目旨在发现通过使用光作为开关来控制电子如何在量子点阵列上移动的新方法。量子点是具有光学和电学性质的半导体纳米颗粒，可以通过改变颗粒的大小进行调节。这项研究的重点是研究如何通过使用不同颜色的光改变连接量子点的分子的形状来打开和关闭相邻量子点之间的电子流动。这种现象可以被用来制造用于光学计算和存储设备的光学可切换组件的材料，与传统电子设备相比，这些组件更快、更高效。广泛地说，这项研究有可能促进对纳米级电荷转移的基本理解，这对于理解大分子、纳米级和生物系统中的光学和电学过程至关重要。研究活动与旨在加强招收、培训和留住科学和工程领域学生的教育努力相结合，特别是在弗吉尼亚大学和老多米尼恩大学代表性不足的群体中。以初中生和高中生为重点，提供了“用光交换分子”的实践活动。通过弗吉尼亚-北卡罗来纳州少数人参与联盟和其他项目招募本科生研究人员。这项拟议的研究旨在测试一种假设，即胶体量子点组件中的电荷转移和激子解离速度可以通过改变连接量子点的光致变色分子的构象来调节。为此，我们综合运用了纳米粒子合成、有机合成、表面化学表征、光学光谱、电学测量和X射线散射等技术。在Marcus理论的背景下，系统地研究了在保持相同的电荷施主-受主对和接触表面化学的情况下，势垒高度对纳米尺度电荷转移的影响。这项研究有可能导致发现一种新型的量子点组件，具有光学可切换的光发射和非易失性的读写操作。通过本研究可能获得的致密、快速、可靠的片上兼容非易失性光存储材料可以为光计算、数据存储、处理和传输带来新的研究方向和能力。来自两所大学的研究小组将(1)在马库斯理论的背景下确定量子点组装中的势垒高度与电荷转移和激子解离速率之间的关系，(2)研究桥分子结构和官能团对量子点组装中电荷转移和激子解离的关系，以及(3)展示具有光学开关光致发光强度的量子点组装。该奖项由化学部/CSDM-B项目提供部分资金。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to discover new ways of controlling how electrons move across arrays of quantum dots by using light as a switch. Quantum dots are nanoparticles of semiconductors with optical and electrical properties that can be tuned through changing the size of the particles. This research is focused on studying how flow of electrons between neighboring quantum dots can be turned ‘on’ and ‘off’ by switching the shape of molecules connecting the quantum dots using light with different colors. Such phenomena can be exploited to make materials for optically switchable components for optical computing and memory devices that are faster and more efficient compared to traditional electronics. Broadly, this research has a potential to advance the fundamental understanding of nanoscale charge transfer which is crucial for understanding optical and electrical processes in macromolecular, nanoscale, and biological systems. The research activities are integrated with educational efforts aimed at enhancing the recruitment, training, and retention of students in the science and engineering fields, especially among underrepresented groups at the University of Virginia and Old Dominion University. With an emphasis on middle and high school students, hands-on activities on 'Switching Molecules with Light' are provided. Undergraduate researchers are recruited through the Virginia-North Carolina Alliance for Minority Participation and other programs.The proposed research aims to test a hypothesis that the rates of charge transfer and exciton dissociation in colloidal quantum dot assemblies can be modulated by changing conformation of the 'bridge' photochromic molecules that inter-connect the quantum dots. To this end, a combination of nanoparticle synthesis, organic synthesis, surface chemistry characterization, optical spectroscopy, electrical measurements and X-ray scattering is employed. In the context of Marcus theory, the impact of potential barrier height on nanoscale charge transfer is systematically studied while keeping exactly the same charge donor-acceptor pair and the surface chemistry at contacts. This research has a potential to result in the discovery of a novel class of quantum dot assemblies with optically switchable light emission and non-volatile ‘read’ and ‘write’ operations. The dense, fast and reliable on-chip compatible non-volatile optical memory materials potentially obtained through this research can lead to new research directions and capabilities for optical computing, data storage, processing and transmission. The research team from the two universities will (1) determine the relationship between the potential barrier height and the rates of charge transfer and exciton dissociation in quantum dot assemblies in the context of Marcus theory, (2) investigate the relationship between bridge molecule structure and functional groups on charge transfer and exciton dissociation in quantum dot assemblies, and (3) demonstrate quantum dot assemblies with optically switchable photoluminescence intensity. This award was partially funded by the Division of Chemistry/CSDM-B Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.