Near-infrared luminescent materials: a review of their practical applications and prospective advancements.

Near-infrared (NIR) spectroscopy has the characteristics of invisible human eyes, strong ability to penetrate biological tissues, fast response speed, non-destructive testing, and avoidance of autofluorescence interference. Therefore, NIR luminescent materials are widely used in various fields, including food monitoring, night vision supplementation, face recognition, imaging, biological analysis, safety monitoring, autonomous driving, and agricultural lighting. However, the lack of NIR luminescent materials with high quantum efficiency, wide bandwidth, and weak thermal quenching still hinders the development of NIR spectroscopy technology. Herein, we review the current research progress and luminescence mechanisms in NIR luminescent materials doped with rare earth (RE) ions, transition metal (TM) ions, and main-group ions, including Yb, Pr, Er, Eu, Nd, Ni, Mn, Mn, Fe, Cu, Cr, Bi, Sb and other ion-doped NIR fluorescent materials. The optical properties, enhancement mechanisms of NIR luminescence, and modulation strategies to adjust the emission wavelength of active ion-doped NIR luminescent materials are highlighted, respectively. We further elaborate on the possible solutions to the design of broadband NIR luminescent materials. This study aims to help researchers in related fields understand the current research status, challenges, and future development trends of RE ion-, TM ion-, and main-group ion-doped NIR luminescent materials.