Carbon spheres with high photothermal conversion efficiency for photothermal therapy of tumor

Development of high-performance photothermal agent plays a decisive role in photothermal therapy of tumor. Herein, carbon spheres are rapidly synthesized by pyrolysis of pyrogallol-formaldehyde spheres at 400–1000 °C under nitrogen atmosphere. As-prepared carbon spheres exhibit strong absorption in near-infrared region and good photothermal effect. The results reveal that the photothermal conversion efficiency of carbon spheres has a tight association with carbon defects caused by pyrolysis. The carbon defects serve as the nonradiative recombination centers of the excited electrons to promote photothermal conversion efficiency. Strikingly, carbon spheres after calcination at 700 °C exhibit the photothermal conversion efficiency of 54.2% under 808 nm laser irradiation, which is superior to the reported carbon-based photothermal agents. The prepared carbon spheres have good cell biocompatibility and can ablate the tumor tissues in tumor-bearing mice through the conversion of near-infrared laser energy into thermal energy.