Thermoplasmonics of Gold-Core Silica-Shell Colloidal Nanoparticles under Pulse Illumination

TL;DR

This study models the thermal and plasmonic behavior of gold-core silica-shell nanoparticles under pulse illumination, revealing how shell properties influence heat transfer and potential photothermal applications.

Contribution

It introduces a combined theoretical framework incorporating Mie theory, electronic temperature corrections, and molecular dynamics to analyze heat transfer in core-shell nanoparticles.

Findings

Thinner dense silica shells accelerate water heating.

Enhanced electron-phonon coupling at the gold-silica interface improves thermal response.

Porous silica shells affect heat dissipation dynamics.

Abstract

Core-shell nanoparticles, particularly those having a gold core, have emerged as a highly promising class of materials due to their unique optical and thermal properties, which underpin a wide range of applications in photothermal therapy, imaging, and biosensing. In this study, we present a comprehensive study of the thermal dynamics of gold-core silica-shell nanoparticles immersed in water under pulse illumination. The plasmonic response of the core-shell nanoparticle is described by incorporating Mie theory with electronic temperature corrections to the refractive indices of gold, based on a Drude Lorentz formulation. The thermal response of the core-shell nanoparticles is modeled by coupling the two temperature model with molecular dynamics simulations, providing an atomistic description of nanoscale heat transfer. We investigate nanoparticles with both dense and porous silica shells (with 50% porosity) under laser pulse durations of 100 fs, 10 ps, and 1 ns, and over a range of fluences between 0.05 and 5mJ/cm2. We show that nanoparticles with a thin dense silica shell (5 nm) exhibit significantly faster water heating compared to bare gold nanoparticles. This behavior is attributed to enhanced electron-phonon coupling at the gold silica interface and to the relatively high thermal conductance between silica and water. These findings provide new insights into optimizing nanoparticle design for efficient photothermal applications and establish a robust framework for understanding energy transfer mechanisms in heterogeneous metal dielectric nanostructures.