A microgel of CdSe quantum dots for fluorescent bisphenol A detection

A fluorescent microgel for BPA detection has been successfully prepared by cross-linking linear poly(styrene-co-glycidyl methacrylate) (poly (STY-co-GMA)) with L-cysteine-capped CdSe quantum dots (Lcys-caped CdSe QDs). The microgel contained specific binding sites created by the covalent grafting of the copolymer onto the QDs via the GMA units, allowing for selective trapping of BPA molecules through π-π and hydrogen bond interactions with phenyl, carboxylic, and amine groups. After binding, electron transfer from the QDs to the analyte quenched the fluorescence at a wavelength of 547 nm when excited at 400 nm. The rational compositional and structural design allows the microgel to accurately detect BPA concentrations over a wide dynamic range of 1.0×10^-1 to 1.0×10⁵ μg/L with a low detection limit (7.0×10^-2 to 8.0×10^-2 μg/L) in deionized, drinking, and tap waters within just 2.0 min. On top of that, the sensitivity for BPA detection was 2.0-4.6 times higher than that of the other 3 structural analogues, even molecular imprinting was not involved. The influence of the STY/GMA compositions in the copolymers and environmental conditions, including pH and ionic strength, on the sensing performance was determined. Moreover, the sensing mechanism and the selectivity with respect to the molecular features were elucidated.