Exploring the Optical Potential of Nano-Bismuth: Tunable Surface Plasmon Resonances in the Near Ultraviolet-to-Near Infrared Range

Although the optical and plasmonic properties of noble metal (Ag and Au) nanoparticles (NPs) have been thoroughly studied and reported, less information is available concerning NPs made of non-noble metals or semimetals that present a more complex electronic structure. In this work, we combine experiments and modeling to explore the optical response of bismuth NPs in the near-ultraviolet, visible, and near-infrared, which has not been studied so far, despite the unusual and interesting electronic properties of bulk Bi. Two dimensional distributions of Bi NPs with different topologies have been prepared and embedded in a protecting and transparent dielectric matrix, thus providing robust materials suitable for structural and optical characterizations. The Bi NP distributions display optical resonances whose spectral position and width are topology-sensitive. The observed macroscopic optical response has been modeled by quasistatic effective medium models, and the analysis shows that the optical resonances present features similar to those of surface plasmon resonances, such as environmental sensitivity. In contrast to noble metals resonances, important nonradiative damping is evidenced in the whole near-ultraviolet-to-near-infrared range, likely due to interband desexcitation paths available in Bi in relation to its electronic structure. Finally, dynamic calculations of the optical extinction performed as a function of the NP's size and shape show a roadmap for tuning the spectral position of the optical resonances in Bi NPs in the whole near-ultraviolet, visible, and near-infrared range.