Improving the photothermal therapy efficacy and preventing the surface oxidation of bismuth nanoparticles through the formation of a bismuth@bismuth selenide heterostructure

Abstract

Bismuth (Bi) nanoparticles (NPs) are emerging as promising photothermal agents for computed tomography imaging-guided photothermal therapy. However, it is challenging to improve their photothermal conversion efficacy and prevent their oxidation. Herein, Bi@bismuth selenide (Bi₂Se₃) core@shell NPs were designed and fabricated for improving the photothermal performance due to the staggered energy levels between Bi and Bi₂Se₃. With near-infrared light irradiation, both the materials could be excited to generate hot carriers due to their extremely narrow bandgaps. The hot electrons would transfer to the conduction band of Bi₂Se₃ and the hot holes to the valence band of Bi, leading to the effective separation of hot carriers. Then, these hot electrons and holes would recombine nonradiatively at the interface of Bi and Bi₂Se₃ and produce more phonons, resulting in an enhanced photothermal conversion efficacy. Moreover, the presence of Bi₂Se₃ on the surface of Bi NPs could prevent Bi from surface oxidation due to the higher stability of Bi₂Se₃. In fact, Bi@Bi₂Se₃ NPs showed excellent biocompatibility and photothermal therapeutic efficacy against cancer cells.