Use of transition-metal-doped sapphire crystals to calibrate and thermally compensate fluorescent-lifetime chemical detectors

Description/Abstract

The paper describes the first use of a plug-in Ti³⁺ - doped sapphire probe to act as a fluorescence-lifetime calibration aid. It has been used for validating a blue-LED-based optoelectronic system designed to interrogate a Ru²⁺ dye oxygen sensor. Ti-sapphire has a compatible absorption and fluorescence spectrum and a similar fluorescence lifetime to Ru²⁺ dye, and its lifetime can be varied, in a predictable manner, by heating or cooling. Use of a small Cr³⁺ - doped sapphire crystal (ruby), close to the Ru²⁺ dye indicator at the probe tip, is also proposed as a temperature monitor, and has, for the first time, been interrogated using the same light source, detector and phase-delay electronics as the Ru²⁺ dye chemical probe.