Efficient nanoheater operated in a biological window for photo-hyperthermia therapy

Remotely monitoring and regulating temperature in a small area are of vital importance for hyperthermia therapy. Herein, we report ~11 nm NaErF₄ nanocrystal as the ultra-small nanoheater, which is highly safe for biological applications. Under 1530 nm photon excitation, upconversion intensity of NaErF₄ is significantly enhanced as compared to the conventionally used 980 nm pumping source. Upconversion mechanisms are discussed on the basis of power dependence measurements. Importantly, light-to-heat transformation efficiency of NaErF₄ through 1530 nm pumping is determined as high as 75%. Efficient NIR emission, centered at ~800 nm and thus within the biological window, is used for the temperature feedback. The potential applications of this highly efficient nanoheater for controlled photo-hyperthermia treatments are also demonstrated.