Smartphone-assisted dual-functional fluorescence probe for on-site and visual detection of hypochlorite and pH in...

Hypochlorite (ClO^-) and pH are critical factors in environmental safety and physiological processes. Meanwhile, detection of ClO^- and pH has practical value in optimizing disinfection processes to ensure efficacy and safety. Herein, a facile dual-functional fluorescence probe was constructed for the determination of ClO^- and pH by a one-step chemical reaction, utilizing 4-chloro-7-nitrobenzofurazan as the fluorophore and piperazine as the recognition unit. The probe enabled quantitative pH detection from 2.0 to 10.0 via the intramolecular charge transfer (ICT) and photoinduced electron transfer (PET) mechanisms. It can also specifically react with ClO^- under the alkaline conditions, leading to the cleavage of the CN bond and the release of the piperazine group, suggesting a possible cleavage-mediated selective recognition mechanism. The proposed probe has quick response for pH and ClO^- detection within 1 min, and has good selectivity and high sensitivity with LOD of 69.8 nM. It was further constructed into a paper sensor integrated with a smartphone, which can achieve smartphone-assisted RGB analysis for on-site detection of pH and ClO^- in actual environmental water samples. This work can provide a new strategy for fabricating multi-functional fluorescence probes and a promising application for on-site detection of pH and ClO^- in environmental monitoring.