Synthesis Of Bi@Bi₂Se₃ Nanoparticles For The Research Of Photothermal Therapy

Bismuth nanoparticles(Bi NPs)have been widely used as green photothermal therapy(PTT)agent due to their low cost and biocompatibility.However,the surface of Bi NPs is chemically active and is easily oxidized by oxygen in the air or media.More importantly,the photothermal conversion efficiency needs to be improved for the better killing of cancer cells and eliminating tumors.Bi@Bi₂Se₃core-shell heterostructure nanoparticles are constructed by coating bismuth selenide(Bi₂Se₃)on the surface of Bi NPs,which improves the photothermal efficiency of Bi NPs and prevents the surface oxidation of Bi NPs.We got the results as follows:(1)Construction of Bi@Bi₂Se₃core-shell nanoparticlesBi NPs were synthesized by thermal injection method,and Bi₂Se₃was coated on the surface of Bi NPs by in-situ growth method to construct Bi@Bi₂Se₃NPs.Both Bi and Bi₂Se₃have extremely narrow band gaps,the band gap structure of Bi and Bi₂Se₃can form a type II heterostructure with staggered energy levels.When irradiated by near-infrared light,the electrons on Bi and Bi₂Se₃are excited and transferred from the valence band to the conduction band,due to the existence of staggered energy levels,hot electrons are transferred to the conduction band of bismuth selenide,and hot holes are transferred to the valence band of bismuth,resulting in effective separation of electrons and holes.Hot electrons and hot holes recombine non-radiatively at the interface of Bi and Bi₂Se₃due to the slightly higher CB of Bi₂Se₃than VB of Bi,producing more phonons andultimately leading to excellent photothermal performance.(2)Biocompatibility improvement and surface oxidation preventionCompared with Bi NPs,Bi₂Se₃is more stable.Therefore,coating Bi₂Se₃on the surface of Bi NPs can improve the photothermal efficiency of Bi NPs and protect the surface of Bi NPs from surface oxidation.Oligosaccharides have excellent water solubility and biocompatibility.The oligosaccharides are loaded by in-situ polymerization of glucose on the surface of Bi@Bi₂Se₃NPs under high temperature conditions,so that Bi@Bi₂Se₃NPs have good water solubility and biocompatibility.(3)In vitro photothermal therapyUnder near-infrared light irradiation,Bi@Bi₂Se₃NP_Sshowed better temperature elevation ability than Bi NPs,which proved that core-shell heterostructure can effectively improve the photothermal performance of Bi NPs.Cell experiments confirmed that Bi@Bi₂Se₃NPs have excellent photothermal therapy(PTT)effects under NIR light conditions.