A “turn-on” fluorescent probe for highly selective discrimination of hypochlorite (ClO−) from oxidants including dichromates (Cr2O72−) in aqueous media

Abstract

A carbazole-based fluorescent probe was synthesized and found to fluoresce (λ_em,max = 440 nm) in the presence of hypochlorite. Guided by a series of control experiments and kinetics studies, protocols for using the sensor to measure the concentration of hypochlorite under a range of conditions were established. The synthesized probe is highly selective for hypochlorite in the presence of interfering strong oxidants including dichromates (Cr₂O₇²⁻). The probe was also used to quantify the presence of the ClO⁻ oxidant in various sources of water conveniently. The underlying mechanism of the sensor was elucidated by NMR, HRMS, and cyclic voltammetry and further confirmed by DFT calculations to proceed through a series of tandem proton and electron transfer processes.