New advances on the marrying of UCNPs and photothermal agents for imaging-guided diagnosis and the therapy of tumors.

In recent years, near-infrared (NIR) light, as a powerful means of external stimulus, has attracted widespread attention in the field of tumor research. On one hand, NIR light-excited rare earth upconversion nanoparticles (UCNPs) have presented unique features in multimodal bioimaging, energy conversion and photocontrolled drug delivery. On the other hand, NIR-light-triggered photothermal therapy (PTT) is a minimally invasive approach in the fight against tumors, owing to its high spatial resolution, economic viability and improved target selectivity. Thus, the marrying of UCNPs and NIR photothermal agents could open new avenues in the construction of theranostic nanoplatforms. This review primarily focuses on the new advances in the design and the therapeutic applications of multifunctional UCNPs-NIR absorber nanoplatforms. The future challenges and prospects in this field are also addressed.