Sol-Gel-based Fluorescent Sensor for MeasuringpHValues in Acidic Environments

This article describes the fabrication and pH sensing characteristics of a sol-gel-derived fluorescent sensor film. A fluorescent pH sensor film operating in an acidic solution was prepared by synthesizing a fluorescent dye having triethoxysilyl pendant group (DPMS) and covalently immobilizing DPMS on a sol-gel porous film. The sensor film shows maximum absorption near 374 nm and a maximum emission near 564 nm when irradiated with ultraviolet light at 374 nm. Both the fluorescence intensity and the absorbance of the sensor film increased with increasing pH. In particular, the fluorescence intensity of the sensor film increased 2.1 times in the pH range of 0.3- 6.5. The sensor film is reproducible, reversible, and stable even after repeated measurements in acidic solution, and it has a long life of more than 1 month without dye leaching.