Design and comprehensive characterization of novel fiber-optic sensor systems using fast-response luminescence-based O2 probes

Abstract

The detection of O2 using optical techniques has now become very important and significant progress has been made in this area over the past few years. The measurement of O2 concentration is a key parameter for diverse applications such as in life sciences, environmental monitoring, industry and biological research, and luminescence-based sensors are a valuable tool for measurements of this type. Often commercial sensors are unable to respond within a short time frame and drift over time - this demonstrates the importance of developing and validating a new technological approach. Given that need, a new sensor has been developed, with a specially-formed tip design coated with a very thin Platinum(II) 5,10,15,20-Tetrakis(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP)-containing a polystyrene layer. The performance and reproducibility of the sensor design has been studied by comparing three identically fabricated sensor probes, showing that the new probe design has extreme fast response times – of a maximum value, Δt90max ≈ 390 ms for increasing and Δt90max ≈ 250 ms for decreasing O2 concentrations. The sensors created had an accuracy of better than ± 0.03 % O2 over the detection range investigated (between 0 % and 20 % O2) and showed a very stable performance over many hours of use. Examining this in detail through extended continuous use, over 12 h in a 0 % O2 solution, the probe stability was confirmed, showing a very low drift of luminescence decay time of ≈ 0.025 %/h (0.01 µs/h). Furthermore, the temperature ‘cross-talk’ has been studied in the important region between 25 °C and 40 °C (so that temperature corrections can be applied) and its mechanical stability, as well as allowing for compensation for any effects seen, has been confirmed. Given the success of the design developed, this work offers both an effective probe design and illustrates many important criteria for the selection of highly effective O2-sensitive coating materials and thus their use as a measurement tool for different quality control (QC) applications in industry.