Directing the Synthesis of Emergent Colloidal Quantum Dots by Correlated Photophysics and Atomic Structure

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The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Sandra Rosenthal and her group at Vanderbilt University to study new quantum dots that are free of toxic heavy metals. Quantum dots which are nanometer-sized versions of semiconductors represent a success stories arising out of the nanotechnology revolution. Quantum dots are notable for their size-dependent light interactions. Quantum dots are tools for neuroscience as they can be used to track individual proteins on a living cell’s surface. Quantum dots occupy a growing portion of the electronic display market due to the vivid colors they produce. While the use and importance of quantum dots are growing, the best performing quantum dots are composed of cadmium, a toxic heavy metal. Indium-based quantum dots are made from non-toxic materials and show comparable color purity and brightness, but struggle in challenging environments such as those found in biological systems. To accelerate the development of new quantum dots, Professor Rosenthal and her research team are using a method to directly correlate the structure of individual quantum dots with their optical performance. In systems where every atom in each quantum dot matters, this methodology can reveal new insights into how complex quantum dot structures yield specific optical behavior. This research enables scientists and engineers to precisely design and synthesize customized quantum dot light emitters as part of advanced manufacturing efforts. As a part of this project, the next generation of scientists are introduced to the growing field of nanotechnology through undergraduate research opportunities and outreach activities for the middle-school students in rural Tennessee.With this award from the Macromolecular, Supramolecular, and Nanochemistry Program, Professor Rosenthal’s research group develops and studies heavy metal-free colloidal quantum dots, including transition metal-based systems. The heavy metal-free quantum dots are being synthesized with complex architectures with the goal of tuning their brightness and photostability. Ultrafast fluorescence upconversion and nanosecond fluorescence spectroscopy are employed to probe both the short and long-time scale carrier dynamics of the photogenerated electrons and holes revealing the effectiveness of the surface passivation. Advanced analytical electron microscopy in conjunction with aberration-corrected scanning transmission electron microscopy (STEM) are used to reveal the chemical and atomic arrangement of the synthesized quantum dots. Further, correlated single particle nanocrystal spectroscopy with STEM imaging is being used to identify structure-function relationships that provide guidance for subsequent synthesis.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.