Department Chair

Jinseok Heo

Date of Award

8-2025

Access Control

Campus-Only Access

Degree Name

Master of Science (MS)

Department

Chemistry

Advisor

Dr. Jinseok Heo

First Reader

Dr. Jinseok Heo

Abstract

Gold nanoparticles (AuNPs) are renowned for their unique optical properties driven by localized surface plasmon resonance, making them valuable in sensing, imaging, and therapeutic applications. My research explores an innovative approach to enhancing surface-enhanced Raman scattering (SERS) signals using quick freezing techniques to aggregate citrate-capped AuNPs into stable structures known as quick freezing-induced AuNP aggregates (QFIAAs). These aggregates exhibit strong, reproducible SERS activity, especially in the near-infrared (NIR) region.

Using Raman and UV-Vis absorption spectroscopy, the adsorption behavior of various dyes on QFIAAs were investigated. Co-freezing AuNPs with positively charged dyes, like Rhodamine 6G, significantly improved dye adsorption and enhanced SERS signals at higher concentrations, while results were mixed with negatively charged dyes. These findings highlight the importance of electrostatic interactions, freezing dynamics, and laser excitation wavelengths in analyte detection. Selective SERS enhancement was achieved depending on whether 532 nm or 780 nm lasers were used, with resonance effects playing a key role in spectral dominance.

This work demonstrates how controlled freezing processes can tune nanoparticle surface chemistry and improve the detection sensitivity of charged analytes, offering implications for biosensing and environmental monitoring.

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