Magnetic-induced graphene quantum dots for imaging-guided photothermal therapy in the second near-infrared window

Graphene quantum dots (GQDs) are considered emerging nanomaterials for photothermal therapy (PTT) of cancer due to their good biocompatibility and rapid excretion. However, the optical absorbance of GQDs in shorter wavelengths (< 1000 nm) limits their overall therapeutic efficacies as photothermal agent in the second near infrared window (1000-1700 nm, NIR-II). Herein, we report a type of GQDs with strong absorption (1070 nrn) in NIR-II region that was synthesized via a one-step solvothermal treatment using phenol as single precursor by tuning the decomposition of hydrogen peroxide under a high magnetic field with an intensity of 9T. The obtained 9T-GQDs demonstrate uniform size distribution (3.6 nm), and tunable fluorescence (quantum yield, 16.67%) and high photothermal conversion efficacy (33.45%). In vitro and in vivo results indicate that 9T-GQDs could efficiently ablate tumor cells and inhibit the tumor growth under NIR-II irradiation. Moreover, the 9T-GQDs exhibited enhanced NIR imaging of tumor in living mice, suggesting the great probability of using 9T-GQDs for in vivo MR imaging-guided PTT in the NIR-II window.