Non-destructive food-quality analysis using near-infrared luminescence from Mg₃Gd₂Ge₃O₁₂:Cr³

Rapid, non-destructive food-quality analysis using near-infrared (NIR) photoluminescence spectroscopy produced by phosphor-converted light-emitting diodes (pc-LEDs) has fascinating prospects for future food-safety monitoring. However, covering the energy window for organic molecular vibrations of interest in these applications requires NIR-emitting phosphors that are highly energy-efficient with ultra-broadband photoluminescence. This remains a materials design challenge. Here, a Cr³⁺-substituted garnet phosphor, Mg₃Gd₂Ge₃O₁₂, is found to possess a desired broadband NIR emission (λ_em = 815 nm, fwhm = 172 nm; 2513 cm^-1) covering from 700 nm to 1200 nm with a photoluminescence quantum yield of 60.8% and absorption efficiency of 44.1% (λ_ex = 450 nm). Fabricating a prototype NIR pc-LED device using the title material combined with a 455 nm emitting InGaN LED chip produces a NIR output power of 23.2 mW with photoelectric efficiency of 8.45% under a 100 mA driving current. This NIR light source is then used to demonstrate the quantitative detection of ethanol in solution. These results highlight the feasibility of this material for NIR spectroscopy and validate the prospects of using NIR pc-LEDs in food-quality analysis.