High-Performance Ratiometric Fluorescence pH Sensor Based on HPTS-IP/TiO₂@THHM Sensing Film

A high-performance ratiometric fluorescence pH sensor based on HPTS-IP/TiO₂@THHM pH sensing film which contains a pH sensing layer and a scattering layer was developed. The pH sensing layer and scattering layer were fabricated by embedding HPTS-IP hydrophobic ion pairs and TiO₂ in TEOS-HTES organic/inorganic hybrid matrix (THHM), respectively. The HPTS-IP hydrophobic ion pairs were excited using pulsed signals from two LEDs with emission peaks of 404 nm and 454 nm, respectively. The fluorescence intensity ratio ([Formula: see text]) was significantly correlated with pH and exhibited excellent performance within the pH range of 6.0 ~ 9.0. Based on fluorescence intensity, peak position, peak width and spectral shape characteristics, a support vector regression (SVR) model was established for predicting the pH value. The root mean square error (RMSE) of the validation dataset in leave-one-out cross-validation (LOOCV) method was 0.180 and the correlation coefficient (R) of the predicted pH versus experimental pH reached as high as 0.999. The sensor exhibited fast response with a response time of 27 s, excellent reproducibility, reversibility and stability.