The Daily Bulletin

The Chemistry Department is hosting a graduate student seminar on Thursday, May 8, during Bengal Pause (12:15 to 1:30 p.m.) in SAMC 151. Our speaker will be Alyssa Heisler, a graduate student in the forensic science master's program. Coffee and snacks will be served. 

Title: Freezing-Induced Dye Adsorption on AuNPs

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 applications1. This presentation 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) region2.

Through a combination of Raman spectroscopy and UV-Vis absorption measurements, the adsorption behavior of various dyes on QFIAAs were investigated3. 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 detection4. 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.

References

Kim, T.; Lee, C.-H.; Joo, S.-W.; Lee, K. Kinetics of Gold Nanoparticle Aggregation: Experiments and Modeling. J. Colloid Interface Sci. 2007, 316 (1), 647–653. https://doi.org/10.1016/j.jcis.2007.08.030.
Cimmerer, C. The Effect of Capping Ligands on the Freezing-Induced Aggregation of Gold Nanoparticles (AuNPs) for Near-IR SERS Substrates; Digital Commons at Buffalo State, 2020. https://digitalcommons.buffalostate.edu/srcc-sp20-physgeosci/3/
Ye, Y.; Hou, S.; Wu, X.; Cheng, X.; He, S. Freeze-Driven Adsorption of Poly-A DNA on Gold Nanoparticles. Langmuir 2022, 38 (14), 4345–4352. https://doi.org/10.1021/acs.langmuir.2c00007
Hoyt, K. W.; Block, A. C.; Tung, J.; Goodman, M. S.; Lednev, I. K.; Heo, J. Quick Freezing-Induced Au Nanoparticle Aggregates (QFIAAs) with Strong and Reproducible Surface-Enhanced Raman Scattering Activity. Langmuir 2025, 41 (2), 1234–1243. https://doi.org/10.1021/acs.langmuir.4c03842