Step-wise Assembly of Nanocrystal Synthons for Precision Doping

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With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Kevin Kittilstved of the University of Massachusetts Amherst will study the formation of clusters that can be used as precursors for preparing semiconductor nanocrystals or quantum dots. Semiconductor nanocrystals are useful for a wide range of optoelectronics, sensing, and biomedical imaging applications. The deliberate incorporation of a small amounts of chemical impurities (or dopants) into the semiconductor nanocrystals introduces tunable functionality and novel properties. This research aims to gain a thorough understanding of the formation mechanism of doped semiconductor clusters and to develop a bottom-up synthetic approach to enable precise control of the dopant level and distribution. This project will contribute to the preparation of a skilled workforce in STEM fields by training graduate and undergraduate students in chemical synthesis and characterization using sophisticated techniques. Members of the Kittilstved group supported by this funding will be involved in developing and executing a hands-on lab experience for the Eureka! Program organized by Girls Inc of Holyoke and the College of Natural Sciences at the University of Massachusetts Amherst. To facilitate effective collaboration amongst group members, Dr. Kittilstved and his research team will engage with the various research mentoring and professional development workshops available through the Graduate School at the University of Massachusetts Amherst. The long-term goal of this project is to establish the chemical parameters that promote precise doping of targeted impurity ions within magic-size clusters, which are known to be critical metastable precursors in the synthesis of quantum dots, nanowires, and nanoplatelets. To achieve this goal, the team led by Dr. Kittilstved will first examine the effect of transition metal dopants in mononuclear precursors and multinuclear CdS-based molecular clusters on the formation mechanism of magic-size clusters and determine what chemical factors promote stepwise assembly of molecular clusters into a precisely doped magic-size clusters. In conjunction with the synthetic aspect of this study, this team will use conventional and state-of-the-art spectroscopic and analytical methods to characterize dopant speciation in the magic-size clusters, to study the kinetics of magic-size cluster formation, and to follow the evolution of the electronic structure from the molecular to the quantum confinement regime. This research strives to provide fundamental knowledge to inform the rational design of high-quality and homogeneously doped designer semiconductor nanostructures for spin-based electronics or optoelectronics 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.