BODIPY with Solvent Polarity and Viscosity Sensitivity for Colorimetric and Fluorescent dual-mode Detection of Cu2.

Dual-mode probes integrating colorimetric and fluorescent responses allow the rapid, accurate, and on-site detection of Cu²⁺. Here in, the synthesized TPA-B-Me consists of BODIPY core structure and thiosemicarbazide moiety, which exhibited good sensitivity to solvent polarity and viscosity, yet a low fluorescence quantum yield (0.48%) due to the photo-induced electron transfer (PET). The Cu²⁺ complexation decreased the absorption peak of TPA-B-Me at 552 nm and disrupted the PET to significantly enhance the fluorescence peak at 572 nm. The H-aggregation by TPA-B-Me-Cu2+ chelates emerged a new absorption peak at 492 nm and emitted a new fluorescence peak at 510 nm. Therefore, TPA-B-Me served as a colorimetric and enhanced fluorescent dual-mode probe for Cu²⁺ detection. Under the colorimetric and fluorescent modes, the limits of detection in PBS and Tris system were 0.369 µM and 0.605 µM, 0.011 µM and 0.078 µM, respectively. Moreover, in real water and soil samples, the fluorescent mode achieved spiked recoveries of 94.1%-108.8% with relative standard deviations (RSDs) of 1.4%-7.3%.