Modeling of Charge Transfer Processes in Heterostructured Nanocomposites

美国国家科学基金会化学部的大分子、超分子和纳米化学项目支持北达科他州立大学的Kilina、Kilin和Kryjevski教授开发计算方法，模拟量子点（大小为十亿分之一米的微小晶体固体碎片）中发生的光诱导过程。开发可持续和高效的能源是人类面临的最大挑战之一。一个有吸引力的解决方案是基于太阳能的燃料电池，它利用太阳能从水中产生氢。这些氢可以用作燃料，燃烧时只产生水（与氧气结合）。然而，高成本、低效率和耐久性是阻碍这种太阳能电池大规模使用的主要因素。应对这些挑战的一种方法是利用量子点。将分子附着在量子点表面会改变其捕捉光的能力。这种改性可以显著提高太阳能转化为化学能的效率。这项研究可能会产生更高效的太阳能电池组件。计算预测指导合理设计新颖的，具有成本效益的能源应用材料。本项目也为高中生、本科生和研究生在计算化学和材料化学建模方面提供了教育和研究经验。提供远程培训/研究活动，以增加女性和美洲土著学生的参与。该项目有助于培养多样化的STEM劳动力，为能源应用新材料的实际设计提供关键的技能和知识。研究团队创造并实现了新颖的量子化学方法，能够准确地模拟具有复杂表面和界面的扩展纳米结构中的光激发动力学。具体来说，该方法适用于由两种不同半导体组成的janus型量子点，如PbS(e)/CdS(e)，并被有机染料共价功能化，以确定在其他竞争过程（如载流子倍增、能量转移、声子介导的载流子弛豫和载流子重组）存在下控制电荷转移动力学的条件。这些计算对于解释时间分辨光谱学数据和指导新的实验探针是有用的。了解电荷和激子传递效率对表面和界面效应的依赖性对于通过化学工程控制量子点/染料复合材料的光激发过程至关重要，从而提高其能量转换应用的功能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division at the National Science Foundation supports Professors Kilina, Kilin, and Kryjevski of North Dakota State University to develop computational methods that model light-induced processes taking place in quantum dots (tiny pieces of crystalline solids that are one billionth of a meter in size). Developing sustainable and efficient energy sources is one of the greatest challenges facing mankind. One attractive solution is solar-based fuel cells that utilize the sun's energy to produce hydrogen from water. This hydrogen can then be used as a fuel, producing only water when it is burned (combined with oxygen). However, high cost, and low efficiency and durability are the main factors that hinder the large-scale use of this solar cells. One way to meet these challenges is to utilize quantum dots. Attaching a molecule to the quantum dot surface alters its ability to capture light. This modification can significantly enhance the efficiency of solar energy conversion to chemical energy. This research may result in more efficient solar cell components. Computational predictions guide the rational design of novel, cost-effective materials for energy applications. This project also provides educational and research experiences for high school, undergraduate and graduate students in computational chemistry and materials chemistry modeling. Remote training/research activities are offered to increase participation of female and Native American students. The project helps prepare a diverse STEM workforce with the skills and knowledge critical for the real-world design of novel materials for energy applications.The research team creates and implements novel quantum chemistry methods capable of accurately modeling the photoexcited dynamics in extended nanostructures with complex surfaces and interfaces. Specifically, this methodology is suitable for the Janus-type quantum dots composed of two different semiconductors, such as PbS(e)/CdS(e), and covalently functionalized by organic dyes, to determine the conditions that govern the dynamics of charge transfer in the presence of other competing processes, such as carrier multiplication, energy transfer, phonon-mediated carrier relaxation and carrier recombination. These computations are useful for interpreting data from time-resolved optical spectroscopy and guiding new experimental probes. Knowledge of the dependence of charge and exciton transfer efficiency on the surface and interface effects is critical for controlling the photoexcited processes via chemical engineering of quantum dot/dye composites, thus improving their functionality for energy conversion applications.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.