A background-subtraction strategy leads to ratiometric sensing of oxygen without recalibration.

Luminescence-quenching based optical oxygen sensors have wide applications in many fields, which have already replaced almost 40% of the commercial market share dominated previously by the Clark oxygen electrode. The majority of optical oxygen sensors are based on lifetime measurement, which are precise, but are relatively expensive, and require high-speed electronics and detecting circuits. Alternatively, oxygen concentration can be measured via a luminescence intensity change, which is a referenced approach according to the Stern-Volmer equation. However, luminescence intensity based measurement tends to be highly influenced by background light. At a given sensor composition, different instrumentation setups, sensor surface roughnesses and thicknesses, and environmental light will result in significantly different calibration curves and sensitivities. This makes luminescence-intensity based optical sensors almost impossible to use practically, because each sensor needs to be recalibrated before use, and the calibration curve each time is quite different. We have solved this problem by introducing a new background-subtraction strategy. After background subtraction, oxygen sensors with different probe concentrations, instrumentation setups, surface roughnesses, supporting matrixes, and at different temperatures present identical calibration curves. This could greatly reduce the calibration task during practical use. Combined with the advantages of low price and a simple optical configuration, the new method will significantly promote wider applications of optical oxygen sensors.