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

An optical oxygen (O-2) 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 O-2 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 O-2. 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 O-2 concentration is at low levels (0.0-0.05% v/v), but the Stern-Volmer plot has a slightly downward curvature at higher O-2 levels. The two-site quenching model correlates well with the calibrated O-2 concentration range (0.0-0.55%). The t(95) response times of the sensor are <0.2 s on going from 0.0% to 0.55% O-2 and <1 s on going from 0.55% to 0.0% O-2. The sensor has high photostability a long lifetime and no hysteresis in the response. (C) 2000 Elsevier Science B.V. All rights reserved.