Differential evolution-optimized gold nanorods for enhanced photothermal conversion

Noble metallic nanoparticles (NPs) have shown great potential in the field of sustainable energy. Gold nanorods (AuNRs), known for their size-dependent optical and electrical characteristics, are strong candidates for various applications, particularly in solar energy conversion. Additionally, AuNRs are well-established nanomaterials in precision medicine. In this paper, we optimize the shape and size of AuNRs to maximize light-to-heat conversion based on a validated theoretical model. Utilizing the Differential Evolution (DE) algorithm, a robust metaheuristic optimization approach, we calculated the optimal size and shape of AuNRs for selected wavelengths. The aspect ratio (AR), defined as the ratio of the diameter to the length of the AuNRs, was a key parameter in the optimization process. The optimization results reveal that for shorter wavelengths, near-spherical AuNRs (AR of 0.71 and 0.75) demonstrate the highest efficiency, while for longer wavelengths, more elongated AuNRs (AR of 0.24 and 0.17) outperform others. This study also includes Computational Fluid Dynamics (CFD) calculations to evaluate the impact of optimized AuNRs on heat generation in a real-world scenario. A case study is presented in which lasers of different wavelengths irradiate a borosilicate glass embedded with a slab of AuNRs at its center. The results, reported as temperature distributions and temperature evolution during irradiation, indicate that the optimized AuNRs significantly enhance heat generation across various laser wavelengths. Specifically, temperature increases were observed as follows: from 2.28 to at 465 nm, from 1.91 to at 532 nm, from 1.7 to at 640 nm, from 40 to at 808 nm, and from 0.94 to at 980 nm, respectively. These findings underscore the effectiveness of the optimization process in enhancing photothermal conversion.