Fe3O4 clusters with high photothermal performance for photothermal therapy of tumor

The poor photothermal performance of Fe3O4 magnetic particles under 808 nm near-infrared laser inevitably limits their application in the field of photothermal therapy for tumor. Herein, Fe3O4 clusters with a mean size of 239.1 nm were synthesized by solvothermal method and thermal treatment at 400 degrees C. Compared with the reported Fe3O4 materials, the developed clusters exhibit high extinction coefficient of 7.88 L/(g center dot cm) and the highest photothermal conversion efficiency of 51.1 %, for which thermal treatment plays a key role. Due to the introduction of thermal treatment, the increased grain size and decreased grain distance can enhance the Fe3+ magnetic coupling and thus improve the extinction ability, while the defects caused by high temperature can trigger more electron traps to promote electron non-radiative relaxation and translate into more thermal energy. The measurements of coercivity (10.6 Oe to 67.3 Oe), blocking temperature (382.3 K to over 400 K) and Urbach energy (0.461 eV to 0.692 eV) before and after thermal treatment support this explanation. The in vitro and in vivo photothermal experiments show that the Fe3O4 clusters can kill tumor cells and inhibit tumor growth through the conversion of laser energy into thermal energy.