The photothermal nonlinearity in plasmon-assisted photocatalysis

TL;DR

This paper reveals that the nonlinear photothermal response in plasmon-assisted photocatalysis is primarily governed by the temperature-dependent thermal conductivity of the host, significantly affecting temperature rise and experimental interpretations.

Contribution

It demonstrates that the host's thermal conductivity dependence causes strong sublinear temperature rise, clarifying previous experimental results and challenging claims of non-thermal electron dominance.

Findings

Temperature rise is dominated by host thermal conductivity.

Nonlinear photothermal response causes sublinear temperature increase.

Explains recent experimental observations in plasmon-assisted photocatalysis.

Abstract

Understanding the intricate relation between illumination and temperature in metallic nano-particles is crucial for elucidating the role of illumination in various physical processes which rely on plasmonic enhancement but are also sensitive to temperature. Recent studies have shown that the temperature rise in optically-thick ensembles of metal nanoparticles under intense illumination is dominated by the thermal conductivity of the host, rather than by the optical properties of the metal or the host. Here, we show that the temperature dependence of the thermal conductivity of the host dominates the nonlinear photothermal response of these systems. In particular, this dependence typically causes the temperature rise to become strongly sublinear, reaching even several tens of percent. We then show that this can explain experimental observations in several recent plasmon-assisted photocatalysis experiments. This shows that any claim for dominance of non-thermal electrons in plasmon-assisted photocatalysis must account first for this photothermal nonlinear mechanism.