Recent studies have demonstrated the use of nanomaterials for photothermal cancer treatment, both in clinical trials and in veterinarian research. Hybrid plasmonic nanoparticles composed of gold and silver with a spherical core and layered shell architectures are a new class of noble metallic nanomaterials which provide highly tunable plasmonic spectra for photothermal therapy and other biological applications in nanomedicine. The seed-mediated growth dynamics of silver-gold core-shell (Ag@Au CS) nanoparticles are monitored based on a stepwise synthetic route in water. These nanoparticles have highly tunable extinction spectra depending on the silver core size and gold shell thickness. In this study, in-situ second harmonic generation (SHG) spectroscopy coupled with extinction spectroscopy is used to investigate the gold shell formation on a spherical silver core in aqueous colloidal suspension. The in-situ SHG results capture a slow rise and formation of a stable signal at early stages of the reaction, followed by time-dependent exponential decays as the CS nanoparticle growth reaction proceeds. The in-situ extinction spectra also show a slow increase in intensity with red shifting and narrowing of the plasmon peak during the gold shell formation. Transmission electron microscopy images show that CS nanoparticle surface morphology becomes more smooth and uniform as the reaction proceeds, corresponding to lower, stable SHG signals and narrower plasmonic spectra. The final extinction spectra are compared to finite-difference time-domain (FDTD) theoretical calculations, showing general agreement. Additionally, the synthesis, characterization, and photothermal measurements of colloidal gold nanoparticles (GNPs) and Ag@Au CS nanoparticles are reported. In a second study, the origin and mechanism of the photothermal process in plasmonic nanoparticles is investigated under varying wavelengths and laser powers to determine the photothermal absorption and scattering efficiencies in water. Overall, the combined approach of synthesis and characterization of various plasmonic nanoparticles with different nano-architectures are studied with different spectroscopies and photothermal measurements to provide a detailed foundation for controlling complex nanoparticle synthesis approaches in developing enhanced nanomaterial technologies.

Measuring the photothermal efficiencies and investigating the growth dynamics of colloidal gold and silver-gold core–shell nanoparticles

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.