Plasmonic Enhancement of Photothermal Conversion Efficiency in Gold‐Nanoparticle Hydrogels

Abstract This study investigates the photothermal properties of citrate‐capped gold nanoparticles (Au NPs) dispersed in agarose gel, examining various sizes and concentrations, particularly within a low‐concentration range (0.2–2.5 nM). Heat transfer measurements are conducted on Au NP hydrogels using laser‐light induced heating, revealing a size‐ and concentration‐dependent temperature increase compared to the plain agarose gel matrix. Experimental data, combined with finite‐element analysis, demonstrate that photothermal energy conversion efficiencies are dependent on NP size and concentration, while the thermal conductivity (TC) of all Au NP hydrogels remains constant and independent of these parameters within the tested concentration range. UV‐visible spectroscopy indicates that the observed photothermal heating arises from light absorption and scattering within the Au NP hydrogels. This work highlights the interplay between plasmonic Au NPs of varying sizes and hydrogels as host matrices, significantly impacting photothermal energy conversion properties. The findings herein aim to provide valuable insights for advancements in biomedical and energy‐related applications.