Single standard calibration for an optical oxygen sensor based on luminescence quenching of a ruthenium complex Original Research Article

An optical oxygen (O2) sensor consisting tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ditetrakis(4-chlorophenyl)borate adsorbed on silica gel has been successfully fabricated and used to continuously monitor O2 gas at low concentration. The luminescence material shows a very strong and stable pink emission when excited by blue light and it is efficiently quenched by O2. The calibration of the optical sensor can be simply done by a single standard flow injection method. The results demonstrate excellent linear Stern–Volmer behaviour when O2 concentration is at low levels (0.0–0.05% v/v), but the Stern–Volmer plot has a slightly downward curvature at higher O2 levels. The two-site quenching model correlates well with the calibrated O2 concentration range (0.0–0.55%). The t95 response times of the sensor are <0.2 s on going from 0.0% to 0.55% O2 and <1 s on going from 0.55% to 0.0% O2. The sensor has high photostability, a long lifetime and no hysteresis in the response.