Synergistic Fluorescence with Significant Red Shift in Coumarin-Doped PMMA Matrices Using CdTe Quantum Dots for Luminescent Concentrator 2D Position Sensing

Luminescent concentrators (LCs) with dimensions of 15 × 10 × 0.3 cm were fabricated and calibrated as high-precision non-imaging position sensors for wide-area detecting applications. The plates were prepared using PMMA/chloroform solutions doped with 10⁻⁴ wt% coumarin dye (MACROLEX Fluorescent Red G) and varying concentrations of 3.5 nm CdTe quantum dots (QDs). Characterization techniques, including XRD, UV-vis absorption, and fluorescence polarization spectroscopy, revealed significant enhancements in photophysical properties with increasing CdTe QDs concentrations. At 0.8 wt%, a giant redshift of 58 nm and fluorescence quantum yield improvement from 90.05 to 94.76% were achieved. Fluorescence polarization measurements confirmed this concentration as optimal, with the highest fluorescence anisotropy. Preliminary evaluations of the proposed LC position sensors demonstrated excellent sensitivity (99.75%) across the horizontal (± 1 mm) and vertical (0–50 mm) displacement ranges in 10-micron increments. The obtained results endorsed the potential of luminescent concentrators as efficient position sensors, for achieving sustainable development goals regarding industrial growth and smart cities development.