Near-infrared-II (NIR-II) luminescence, which serves as a promising spectral window for biomedical applications and spectral analysis, has numerous potential applications. In this work, the NIR-II luminescence is realized in Li4SrCa(SiO4)2:Cr4+ phosphors. Under 465 nm excitation, the emission peak of Li4SrCa(SiO4)2:3%Cr4+ is located at 1215 nm and the full width at half maximum (FWHM) is more than 230 nm, covering the ultra-long range of 950–1600 nm. The photoluminescence spectra, diffuse reflectance spectra, Raman spectra and time-resolved emission spectra confirm the NIR-II luminescence mechanism. Furthermore, a novel post-reduction strategy is proposed to realize the leap-forward enhancement of NIR-II luminescence from Cr4+. By mutually substituting Sr2+ and Ca2+, a series of Li4Sr1+zCa1−z(SiO4)2:3%Cr4+ (z = −1 to 1) samples are prepared to investigate the universality and applicable conditions of the post-reduction strategy. Benefitting from the NIR-II emission of Cr4+, it has great application potential in optical temperature measurement and spectral analysis.
Near-infrared (NIR) II region (1000–1700 nm) lighting sources possess special potential for temperature sensing and quantitative composition analysis. However, it is a challenge to tune the luminescence toward such long wavelength NIR-II emission. Herein, Cr 4+ ions occupation is designed and verified in olivine-type CaYGaO 4 as [CrO 4 ] tetrahedron by site occupancy confinement. Under 620 nm red light excitation, the phosphors display broadband NIR-II emission centered at 1330 nm with a full width at half maximum (FWHM) of 233 nm, resulting from spin-allowed 3 T 2 to 3 A 2 transition of Cr 4+ ions in T d symmetry. The optical thermometry application is demonstrated by decoding the spectral shift and decay times varying with temperature, and the maximum relative sensitivities are 5.82% and 0.78% K −1 , respectively. Furthermore, a flexible film containing CaYGaO 4 :Cr 4+ is fabricated to implement the non-invasive detections of fillet temperature and NH 3 concentration in ammonia. This work represents a step toward developing next-generation NIR-II luminescence materials and widens non-invasive detection applications.
危险品化学品经营许可证（带存储）