Broadband NIR-II luminescence from Cr3+/Ni2+ co-doped Lu3Ga5O12 for non-destructive plastic identification and sorting

The second near-infrared window (NIR-II, 1000-1700 nm) phosphor-converted LEDs (pc-LEDs) show great potential for portable spectroscopic detection. However, high-performance long-wavelength (>1350 nm) NIR-II phosphors that combine broadband emission, high thermal stability, and efficient blue-light excitation, are still relatively scarce. Herein, a Lu 3 Ga 5 O 12 :Cr 3+ ,Ni 2+ phosphor was developed via a Cr 3+ sensitization strategy. Cr 3+ and Ni 2+ stably occupy the [GaO 6 ] octahedral sites, enabling efficient energy-transfer from Cr 3+ to Ni 2+ . The optimal sample exhibits broadband NIR-II emission at 1427 nm with an FWHM of 277 nm, an EQE of 23.1%, and excellent thermal stability (I 373K /I 293K  = 81.5%). The pc-LED based on this NIR-II phosphor achieves penetration imaging and non-destructive identification of daily necessities. More notably, rapid spectral differentiation of common plastics (PA, PE, PP, PVC and PET) was successfully realized using the NIR-II luminescence of the as-prepared phosphor. This work provides guidance for constructing high-performance NIR-II phosphors and promotes the practical deployment of NIR spectroscopy in resource recycling.