Oxygen sensor based on a luminescence sensing element
Evstrapov A.A., Kotov V.P., Kurochkin V.E., Muravyov D.O.
Istitute for Analytical Instrumentation, 198103 St Peterburg, Russia

The sensor is intended for determination of the macro and microconcentration of oxygen in gaseous and liquid environments. The operation of the sensing element (SE) of the device is based on the phenomenon of oxygen quenching of luminescence of polypyridine Ru(II) complexes immobilized in the porous glass matrices.

The dimensions of SE matrix are 8x4x0.3 mm. The concentration of luminescence indicator in the matrix is 10^-3 M, providing a sensitivity of 0.1 vol.% and 5 s response of the sensor when measuring oxygen concentration in the atmosphere. The use of the pulse excitation of luminescence and the phase measurement method allows to increase the lifespan of gas sensitive element and to reduce the sensor drift caused by SE photodestruction. The sensor includes an oxygen-insensitive reference channel that compensates the influence of temperature and pressure variations.

There are two factors which allow to achieve a compact sensor design with highly effective selection of the information signal:

• use of a small-size high-intensity source of excitation (namely light emitting diode with a maximum of radiation in the range of 430 to 470 nm) with spectrum matching the maximum of SE absorption,
• application of silicon photodiodes with the correcting filter.

The versatility of the sensor allows its application

• in ecology and life support systems: for the control of oxygen concentration in closed rooms and in fluids;
• in medicine and biology: for quality control of catheters in biological research, for examination and treatment of various forms of respiratory diseases, monitoring of oxygen in blood, for the control of respiratory mixtures at freezing;
• in industry for process control.

Optical luminescence sensors have certain advantages. They can be made extremely small, have low response time, high sensitivity and long service life. Besides, the use of remote optical fiber probes ensures that the sensors are practically safe when operating in explosive environments. The luminescence sensor of oxygen does not contain expensive materials and inventory parts, is rather simple to manufacture and tuning and, therefore, can be much cheaper than electrochemical sensors similar in characteristics.

The investigations on development of the luminescence sensor of oxygen have been conducted at the Institute for Analytical Instrumentation RAS since 1997. There are several models now at the stage of alpha testing.

A host of scientific publications, patents and copyright certificates both in Russia and abroad testifies great practical value of this project.