Near‐Infrared Windows I and II Phosphors for Theranostic Applications: Spectroscopy, Bioimaging, and Light‐Emitting Diode Photobiomodulation

Abstract The importance and practicality of near‐infrared (NIR) light for the biomedical field has attached importance to the academe and industry with the development of technology. Luminescent materials with different doping strategies are promising candidates for covering near‐infrared biological windows from 700 nm to 1 700 nm. The relationship between NIR light, nanophosphors, and biological tissue towards the function of diagnostic and therapy in different NIR windows is explored clearly, which corresponds to diffuse reflection spectroscopy with bioimaging and light‐emitting diode (LED) photobiomodulation. The diseases can be monitored with specific chromophore absorption under the NIR light source, which also can be traced to the dynamic change of the biological environment by luminescent materials. Especially in brain diseases, cytochrome c oxidase in mitochondria as the crucial photoreceptor can be activated under NIR irradiation to achieve the non‐invasive treatment of neuron protection and recovery. NIR light attributed to LED or nanophosphors show the potential of theranostic approaches in biomedical technology. Cr³⁺‐ and Ni²⁺‐activated phosphors covering NIR windows I and II are presented with optical properties to explore the feasibility and practicability of non‐invasive precise medical treatment in the future.