Abstract

This study investigates the optimization of light-to-heat conversion in gold nanoparticles under irradiation by continuous- and pulsed-wave laser sources. The conversion process relies on the absorption of electromagnetic energy and the subsequent generation of heat, a phenomenon that is integral to a variety of applications. The photothermal conversion model is based on the Rayleigh-Drude approximation, facilitating predictions of the optical cross-sections for capped gold nanorods. The mathematical model takes into account the shape and size parameters of the nanoparticles, in particular diameter and length, as well as the thickness of the capping agent, the concentration of the nanoparticles and the refractive indices of the surrounding medium and the capping material. The aim is to maximize the efficiency of photothermal conversion. Using the Nelder-Mead optimization algorithm, the research examines three distinct laser wavelengths: two continuous-wave lasers at 465 nm, 808 nm, and a pulsed laser at 532 nm, respectively. The present research extends to the mathematical modeling of six key parameters that influence the conversion of light to heat, providing a comprehensive optimization framework. The obtained results indicate that for continuous-wave lasers, the aspect ratio of optimal gold nanoparticle dimensions varies as a function of wavelength: a higher aspect ratio (0.7) is optimal for the shortest wavelength 465 nm, compared to the 808 nm wavelength with 0.17 aspect ratio. In contrast, for the pulsed laser at 532 nm, the aspect ratio of the optimal nanoparticles approaches almost unity (0.96), demonstrating that a quasi-spherical shape is most effective in maximizing heat generation. These results point to the dependence of photothermal efficiency on laser characteristics such as wavelength, pulse behavior and intensity. By correlating nanoparticle design with specific laser parameters, this work contributes to the targeted development of nanomaterials for efficient energy conversion in applications ranging from bacteria deactivation, through energy generation and medical therapies to materials processing.

Citations

Authors (8)