RESUMEN
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 (λem = 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% (λex = 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.
RESUMEN
Endowing a single material with various types of luminescence, that is, exhibiting a simultaneous optical response to different stimuli, is vital in various fields. A photoluminescence (PL)- and mechanoluminescence (ML)-based multifunctional sensing platform is built by combining heterojunctioned ZnS/CaZnOS:Mn2+ mechano-photonic materials using a 3D-printing technique and fiber spinning. ML-active particles are embedded in micrometer-sized cellulose fibers for flexible optical devices capable of emitting light driven by mechanical force. Individually modified 3D-printed hard units that exhibit intense ML in response to mechanical deformation, such as impact and friction, are also fabricated. Importantly, they also allow low-pressure sensing up to ≈100 bar, a range previously inaccessible by any other optical sensing technique. Moreover, the developed optical manometer based on the PL of the materials demonstrates a superior high-pressure sensitivity of ≈6.20 nm GPa-1 . Using this sensing platform, four modes of temperature detection can be achieved: excitation-band spectral shifts, emission-band spectral shifts, bandwidth broadening, and lifetime shortening. This work supports the possibility of mass production of ML-active mechanical and optoelectronic parts integrated with scientific and industrial tools and apparatus.