Recent progress of UCNPs-MoS nanocomposites as a platform for biological applications.

Composite materials can take advantages of the functional benefits of multiple pure nanomaterials to a greater degree than single nanomaterials alone. The UCNPs-MoS composite is a nano-application platform that combines upconversion luminescence and photothermal properties. Upconversion nanoparticles (UCNPs) are inorganic nanomaterials with long-wavelength excitation and short-wavelength tunable emission capabilities, and are able to effectively convert near-infrared (NIR) light into visible light for increased photostability. However, UCNPs have a low capacity for absorbing visible light, whereas MoS shows better absorption in the ultraviolet and visible regions. By integrating the benefits of UCNPs and MoS, UCNPs-MoS nanocomposites can convert NIR light with a higher depth of detection into visible light for application with MoS through fluorescence resonance energy transfer (FRET), which compensates for the issues of MoS's low tissue penetration light-absorbing wavelengths and expands its potential biological applications. Therefore, starting from the construction of UCNPs-MoS nanoplatforms, herein, we review the research progress in biological applications, including biosensing, phototherapy, bioimaging, and targeted drug delivery. Additionally, the current challenges and future development trends of UCNPs-MoS nanocomposites for biological applications are also discussed.