Synthesis and application of ratio fluorescence probe for chloride

As chloride ions (Cl−) play a vital role in maintaining normal physiological activity, detection of chloride ions is quite urgent. Hence, we developed chloride fluorescence probes to highly selectively and sensitively monitor chloride ions. The probe M2 with single emission has a high fluorescence quantum yield (Φ = 45%), and it is capable of quantitative detection of Cl− under physiological conditions (pH = 7.4) and pH = 5.0 with a linear range of 0.1–4.0 mM; nevertheless, it is of the switch-off type. We further synthesized a ratiometric fluorescent probe MY with M2 as raw material, which featured excellent selectivity and anti-interference, and large two-photon cross section (555 GM). The probe is conveniently used to detect Cl− in water samples and biological samples including human sweat, serum, and urine samples, indicating it holds great promise for chloride detection and biological application.