40. 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 commercial market share dominated previously by 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 luminescence intensity change, which is a referenced approach according to Stern-Volmer equation. However, luminescence intensity based measurement tends to be highly interfered by background light. At a given sensor composition, different instrumentation setup, sensor surface roughness and thickness, and environmental light will result in significantly different calibration curves and sensitivity. This makes luminescence-intensity based optical sensors almost impossible to be used practically, because each sensor need to be recalibrated before use, and calibration curve in 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 concentration, instrumental setup, surface roughness, supporting matrix, and in different temperatures, present identical calibration curve. This could greatly reduce calibrating task during practical use. Combined with advantages of low price and simple optical configuration, the new method will significantly promote wider applications of optical oxygen sensors.

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