Optochemical fiber sensor for Toluidine Blue detection in high turbidity media

We report the analytical performance of an optochemical fiber optic sensor for the detection of dyes in aqueous media with high turbidity. Specifically, the analytical performance of this sensor was evaluated for the quantitative detection of Toluidine Blue (TB) in aqueous solution and also in turbid suspensions of TiO2 anatase nanoparticles. The detection limit attained was 5 × 10−7 M with a linear sensitivity of 7 × 104 M−1 across a linear range from 5 × 10−7 to 5 × 10−6 M. We used the optochemical sensor for two main purposes: (1) in situ characterization of the adsorption isotherm of Toluidine Blue on TiO2 nanoparticles; (2) in situ characterization of the photodegradation of Toluidine Blue mediated by UV irradiation of TiO2 nanoparticles. The main aim of this report is to establish the construction and performance of a simple, cheap and small optochemical sensor with clear applications in the field of dye-polluted environmental monitoring.