Mater. Chem. Today,2021,22,100555.https://doi.org/10.1016/j.mtchem.2021.100555

Full control on the valence of the active ions in solids to improve properties is the central topic of chemistry and materials. Cr3+ and Cr4+ ions generally emit wavelength-different near-infrared (NIR) light. Here, we have developed a chromium valence-controllable single-phase phosphor, Mg2GeO4:Cr3+,Cr4+ to achieve super-broad NIR luminescence. High Li+ content charge compensators can stabilize Cr3+ while high temperature sintering tends to facilitate the formation of Cr4+. Through fine adjusting the synthesis conditions, pure Cr3+ or Cr4+ luminescence can be obtained with peak emission locating at 935 and 1190 nm, respectively. Super-broad-band dual emission spanning from 650 to 1600 nm is realized via fully controlling the concentration ratio of Cr3+ to Cr4+ in single host. By measuring the transmission spectra of several foodstuffs illuminated by our phosphors, nondestructive analysis in food safety area can be realized. This study provides a new strategy for exploiting super-broad-band NIR luminescent materials.