The fluorescence characteristics of Ag/g-C3N4 gel and its application in the marine atmospheric chloride ion optical fiber sensing system

This paper develops a fluorescence quenching fiber optic sensing system based on nano-silver modified graphite phase carbon nitride (Ag/g-C₃N₄) gel for the detection of chloride ion concentration in marine atmosphere. By optimizing the ratio and preparation process, the composite ratio of 5 mg carbon nitride and 0.2 mL nano-silver was determined. The gel was coated on the end face of the plastic optical fiber (POF) and the inner wall of the hollow glass tube to construct a fluorescent optical fiber probe, which was combined with an ultraviolet light source and a photomultiplier tube (PMT) to form a miniature optical fiber sensing system. Experiments show that nano-silver modification significantly improves the sensitivity of chloride ion detection. The fluorescent material produces a fluorescence peak of 440 nm under the excitation of 370 nm light source. The sensing system exhibits good linear response characteristics in the range of 0–15 µg/L chloride ion concentration, the limit of detection (LOD) is as low as 0.0143 µM, and the response time is about 3 s. The sensing system has the advantages of miniaturization, environmental friendliness and strong anti-interference ability, which provides a new idea for the application of fluorescent materials and optical fiber sensing technology in the field of marine environment detection.