One-pot microwave-assisted synthesis of Ag2Se and photothermal conversion

•The Broad-spectrum light-harvesting Ag2Se nanoparticles were synthesized by the one-pot microwave-assisted method.•The higher concentration of the solution, the stronger photothermal conversion . The temperature of the Ag2Se with the concentration of 0.085 mol/L can reach 54.1℃.•The temperature of the Ag2Se aqueous solution can reach 60.2℃ under 1.6 W laser power irradiation.•The good UV–Vis-NIR absorption spectrum proves its good photothermal conversion , which is accordance with the first principle simulation.