Molecular imprinted Bi4O5Br2 nanosheets for visual ultrasensitive chlorophenols detection by developing a dye-photosensitization sensing system

The ultrasensitive, visual and intelligent identification of persistent chlorophenols (CPs) in complex drinking and environmental water matrices is highly desirable. In this study, we have established an interesting colorimetric dye eosin Y (EY)-molecular imprinted Bi 4 O 5 Br 2 nanosheet photosensitization sensing system for CPs detection, in which the key is the rapid EY photosensitization decolorization to be efficiently inhibited in the presence of CPs. It displays an ultrasensitive detection of CPs, especially for the typical 2,4,6-trichlorophenol (TCP) across from 10 ng·L −1 to 1 mg·L −1 , achieving a limit of detection of 7 ng·L −1 with remarkable selectivity. By means of in-situ Fourier transform infrared spectroscopy, time-resolved laser flash photolysis spectroscopy, and theoretical calculations, the outstanding performance is attributed to (i) the efficient transfer of triplet excited state electrons from EY to the ultrathin Bi 4 O 5 Br 2 (∼4 nm) nanosheets through energy band alignment and (ii) enhanced TCP selective adsorption resulting from a planar adsorption configuration induced by multiple Bi–Cl interactions, along with specific molecular imprinting recognition sites. Additionally, a real-time intelligent sensing platform was further engineered by integrating automatic sampling, an optical fiber source and a smartphone with color recognition software, enabling convenient and visual detection of TCP in challenging water environments. The sensing system exhibited excellent performance in detecting TCP across various actual water matrices, achieving acceptable recovery rates ranging from 93.33% to 113.33% with the relative standard deviations between 0.80% and 11.31%. It also demonstrated significant advantages over the ultra-performance liquid chromatography-tandem mass spectrometry, particularly regarding speed, simplicity and sensitivity, thus indicating substantial potential for practical applications in water quality monitoring.