Comparison of the Vibrational Modes of Thiolated Gold Nanoparticles Undergoing Core-Conversions Via Raman Spectroscopy

Author

William Gregory Cannella Jr., University of MississippiFollow

Date of Award

Spring 5-9-2020

Document Type

Undergraduate Thesis

Department

Liberal Studies

First Advisor

Nathan Hammer

Second Advisor

Amal Dass

Third Advisor

Murrell Godfrey

Relational Format

Dissertation/Thesis

Abstract

In this project, the vibrational characteristics/vibrational modes are explored via Raman Spectroscopy for thiolated-gold nanoparticles. This class of compounds is also known as gold nanoparticles (AuNPs). They remain of great interest in research areas such as catalysis, gold dependent nanoelectronics, drug delivery, and sensing, due to their unique size-dependent optical, chiroptical, and electronic properties. Vibrational spectroscopy of thiolated gold nanoparticles are oftentimes considered nontrivial as the compounds strongly absorb light in the visible region of the electromagnetic spectrum, are generally considered weak scatterers, and give off large amounts of fluorescence. This combined with their black appearance, susceptibility to localized heating, and lack of topographical features makes these compounds challenging to study. These compounds possess unique structural compositions as they are composed of a number of covalently bonded gold atoms forming what is referred to as a gold core complex. This core complex is then surrounded by various gold-thiolate staple molecules such as monomeric (SR-Au-SR), dimeric (SR-Au-SR-Au-SR), trimeric (SR-Au-SR-Au-SR-Au-SR), as well as bridging thiols. Furthermore, the core complex is also surrounded by various ligand groups. For the purposes of this study, the ligands of 2-Phenylethylthiol and tert-butylthiol were investigated. One of the biggest opportunities AuNPs provide, is the ability to undergo core-size conversions due to electronic and steric effects of the ligands and the interaction of Au-S bonds. Here, the gold thiolate molecule Au₃₈(2-PET)₂₄ undergoes a core-size reduction via etching with tert-butylthiol to produce Au₃₀(S-tBu)₁₈, coined “green-gold” by the Dass Group. Oftentimes, subtle spectral differences are observed between core-size conversions; however, this study also explores the vibrational spectroscopic changes induced by ligand exchanges for a compound that has yet to be vibrationally studied elsewhere.

Recommended Citation

Cannella, William Gregory Jr., "Comparison of the Vibrational Modes of Thiolated Gold Nanoparticles Undergoing Core-Conversions Via Raman Spectroscopy" (2020). Honors Theses. 1383.
https://egrove.olemiss.edu/hon_thesis/1383

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