Rational Design of a 3D-printed Sensing Platform for On-site Measurement of Toluene Based on Cu(I) Complex.

This study reports the rational design and synthesis of a novel stimuli-responsive fluorescent complex based on Cu(I) and 4-methylpyridine. The material exhibits a unique vapor-triggered fluorescence switching behavior: upon exposure to toluene vapor, its emission undergoes a significant bathochromic shift from 445 nm (blue) to 553 nm (yellow), accompanied by a distinct naked-eye-detectable blue-to-yellow colorimetric transition. Based on this effective molecular switching mechanism, we have developed a portable fluorescence detection platform featuring integrated excitation optics, long-pass filtration (λcut = 420 nm), and real-time spectral analysis software. This device achieves rapid (< 1 min) and selective quantification of trace toluene vapor with a detection limit of 4.45 ppm, demonstrating excellent anti-interference capability against relevant aromatic compounds such as benzene, benzaldehyde, paraxylene, orthoxylene or mesitylene and common organic solvents (e.g., ethanol, acetone, hexane) and potential environmental interferents (relative error < ± 5%). The sensing system exhibits remarkable reversibility and operational stability under ambient conditions (20-40 °C, RH 30-80%). This work establishes a promising strategy for on-site, real-time monitoring of hazardous volatile organic compound such as toluene, with significant implications for environmental surveillance, industrial safety, and point-of-care diagnostics.