01/07/2026
By Kwok Fan Chow

The Kennedy College of Science, Department of Chemistry, invites you to attend a Ph.D. Research Proposal defense by Kithma Sajini entitled “Computational Investigation of Ligand-Protected Gold Nanoclusters and Graphene-Based Hybrid Systems.”

Date: Monday, January 26, 2026
Time: 9 a.m.
Location: Olney Room 518

Committee:

  • Jerome Delhommelle (Advisor), Department of Chemistry, University of Massachusetts Lowell
  • James Whitten, Department of Chemistry, University of Massachusetts Lowell
  • Marina Ruths, Department of Chemistry, University of Massachusetts Lowell
  • Caroline Desgranges, Department of Physics and Applied Physics, University of Massachusetts Lowell

Abstract: 

Nanoclusters represent a unique class of materials that bridge the gap between molecules and bulk metals, exhibiting discrete electronic structures and size-dependent optical properties. Among them, the gold nanocluster Au25(SR)18, protected by trehalose ligands, is particularly attractive due to its atomic precision, chiroptical activity, and potential applications in catalysis and bioelectronics. Despite significant experimental progress, a detailed understanding of the relationship between its structure, ligand effects, and electronic properties remains limited. 

To address this challenge, this research proposal integrates quantum chemical and machine learning approaches to explore the structural, electronic, and catalytic behavior of Au25(SR)18 nanoclusters and their graphene-based hybrids. In the first project, Time- Dependent Density Functional Theory (TD-DFT) calculations will be performed to study the optical and chiroptical properties of the Au25(SR)18 nanocluster. Simulated UV–Vis and circular dichroism (CD) spectra will be compared with experimental data to identify the origin of its optical activity and characterize charge-transfer transitions. 

The second project focuses on modeling the covalent functionalization of pristine graphene with perfluorophenyl azide (PFPA) linkers using Density Functional Theory (DFT). This study aims to elucidate how linker chemistry and substrate effects influence charge transfer and the electronic coupling between graphene and gold nanoclusters. In the third project, a Machine Learning Interatomic Potential (MLP) based on the Atomic Cluster Expansion (ACE) framework will be developed to perform large-scale molecular dynamics simulations, enabling the explo- ration of nanocluster dynamics and thermal stability beyond the reach of quantum methods. The integration of TD-DFT, DFT, and MLP approaches will establish a unified multi-scale framework for understanding and predicting the properties of ligand-protected gold nan- oclusters and their hybrid interfaces. The outcomes of this work are expected to provide fundamental insights that support the rational design of nanocluster–graphene composites for future applications in catalysis, sensing, and energy conversion. 

All interested students and faculty members are invited to attend.