LEAPS-MPS: Unveiling the Origin of Carbon Dot Fluorescence Using Density Functional Tight Binding

In this project, managed by the Division of Chemistry at the NSF, Professor Duchimaza Heredia and students at Emmanuel College will use computer simulations to understand why carbon dots fluoresce. Carbon dots are formed by a polymerization reaction of small molecules at high temperatures, and they have been observed to glow in various colors. The multicolor fluorescence of carbon dots makes them useful in applications including drug delivery, biosensing, and imaging. Computational methods will be employed to investigate the reason for fluorescence, overcoming experimental challenges in determining the structure of the carbon dots. This project will create research positions that support training for undergraduate students of diverse backgrounds and establish partnerships with computational chemists around the Boston area to introduce students to a graduate-level research environment. The chemistry education pathway will be strengthened by involving high school teachers in this investigation and using aspects of this project to teach high school students how computers are used in chemistry research.Professor Duchimaza Heredia and his computational chemistry research group will investigate the electronic nature of multicolor fluorescence in polymeric or amorphous carbon dots. Existing hypotheses include size-dependent emissions, surface-state derived emission, and fluorescence due to molecular fluorophores. While fluorescence across the visible spectrum is possible, experimental analysis supports only blue fluorescence. The project will use enhanced sampling methods to predict the structure of amorphous carbon dots. It will also leverage the chemical accuracy of density functional theory (DFT) and the speed of density functional-based tight-binding (DFTB). This project aims to determine whether fluorescence is possible solely due to the carbon dot structure, identify how the environment of a fluorophore influences its emission properties, and perform extensive benchmarking to compare the results of DFT and DFTB for accurate and fast prediction of carbon dot and fluorophore systems.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.