Particle Size-Dependent Energy Conversion in Plasmonic Nanostructures for Photothermal Catalysis Applications

Abstract

This work examines the influence of nanoparticle size and morphology on the photothermal catalytic behavior of gold and silver nanostructures. Localized surface plasmon resonance (LSPR) effects were tuned to optimize light absorption and heat generation. A tight and nonlinear relation between particle diameter and optical properties was confirmed as the particles with diameters in the range 25-35 nm have achieved the maximum efficiency of light absorption, making this range optimum to convert the photons into condensed local heat. A radical transformation was disclosed when the particle diameters exceed 60 nm as the scattering dominates the absorption. Results revealed that he particle diameter can change the maximum temperature as well as the heat distribution in the surrounding medium. Particles in the range 20-40 nm produce sharp thermal concentration, which is localized at the surface interface (<10 nm from the surface). The larger particles (>40 nm) exhibit a unique phenomenon (secondary hot spots) at the far-field range, which extends the effective thermal range in the catalyst. Finally, the reaction rate constant does not continuously increase with decreasing the particle diameter as a precise balance between the surface-to-volume ratio and photothermal conversion efficiency, whose maximum was obtained for the particle diameter of 40 nm.