Dual optical sensor for oxygen and temperature based on the combination of time domain and frequency domain techniques

Abstract

In measuring specific conditions in the real world, there are many situations where both the oxygen concentration and the temperature have to be determined simultaneously. Here we describe a dual optical sensor for oxygen and temperature that can be adapted for different applications. The measurement principle of this sensor is based on the luminescence decay times of the oxygen-sensitive ruthenium complex tris-4,7-diphenyl-1,10-phenanthroline ruthenium(III) [Rudpp] and the temperature-sensitive europium complex tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) [Eudatp]. The excitation and emission spectra of the two luminophores overlap significantly and cannot be discriminated in the conventional way using band pass filters or other optical components. However, by applying both the frequency and time domain techniques, we can separate the signals from the individual decay time of the complexes. The europium complex is entrapped in a poly-(methyl methacrylate) (PMMA) layer and the ruthenium complex is physically adsorbed on silica gel and incorporated in a silicone layer. The two layers are attached to each other by a double sided silicone based tape. The europium sensing film was found to be temperature-sensitive between 10 and 70ºC and the ruthenium oxygen-sensitive layer can reliably measure between 0 and 21% oxygen.

Interpretation of europium(III) spectra

“…The delay is measured as a phase shift, which can be used to calculate the decay time. Although frequencydomain measurements are often used in fluorescence spectroscopy of organic molecules, only few studies have been devoted to frequency-domain measurements on europium(III) compounds [752][753][754][755][756].…”

Exceptional Oxygen Sensing Properties of New Blue Light‐Excitable Highly Luminescent Europium(III) and Gadolinium(III) Complexes

“…The materials used in optical oxygen sensors are quite established. [1][2][3][4] Most oxygen sensors employ such widespread indicators as ruthenium(II) polypyridyl complexes, [5][6][7] platinum(II) and palladium(II) porphyrins [8][9][10][11] and their analogues. [12][13][14] Other luminescent indicators are less popular which is explained by their inferior photophysical properties (low absorption coefficients and luminescence quantum yields, short luminescence decay times, poor photostability etc.)…”

The Applicability of 2-amino-4,6-diphenyl-pyridine-3-carbonitrile Sensors for Monitoring Different Types of Photopolymerization Processes and Acceleration of Cationic and Free-Radical Photopolymerization Under Near UV Light

“…Due to molecular sizes of the sensor, information obtained through it mainly concerns its closest surroundings. The chemical composition of the molecular sensor can display sensitivity to changes in polarity [6,7], viscosity [8,9,10], temperature [11,12,13], pressure [14,15], oxygen [16] and other parameters of the researched system. To monitor the observed process, the parameters are explicitly used for the applied molecular probe, such as, for example, changes in the character of the absorption spectrum [17] or fluorescence [18,19].…”