Hexagonal Bismuthene and Bismuth Nanoparticles for Light-To-Heat Conversion

Bismuth is an inexpensive, biocompatible, and semimetallic material. Light absorption in bismuth occurs by means of intraband transitions from mid-IR to UV due to its exotic electronic structure. Thus, bismuth has been pointed out as an excellent material in applications relying on optical absorption, such as computed tomography, photocatalysis, and photothermal therapy. Herein, we present an extensive study of the unexplored thermo-optical response of high-quality bismuth nanomaterials: hexagonal bismuthene (hBi) and spherical bismuth nanoparticles (sBiNPs). We observed the light-to-heat conversion (LHC) performance of both compared to that of functionalized Au NPs (NPs) as an alternative to plasmonic NPs for LHC applications. As a result, we have illustrated the potential of bismuth NPs and bismuthene for thermo-optical applications, demonstrating the potential of bismuth NPs and bismuthene for thermo-optical applications, with precise local heating quantified via Raman thermometry. Under 2.1 mW excitation at 633 nm, maximum temperatures of 425 K for AuPMBT, 400 K for sBiNPs, and 325 K for hBi were reached. These values highlight the competitive LHC efficiency of bismuth-based nanostructures, especially sBiNPs, and reveal the influence of thermal diffusion in 2D systems like hBi.