Optical sensor with radioluminescent light source

An optical sensor is disclosed which uses a radioluminescent light source to supply the incident radiation for detecting a selected substance in a test medium. The radioluminescent source includes a beta emitting radio isotope which energizes a co-immobilized luminophore to release light in a given wavelength for a chemical sensor operation. The radioluminescent source is coupled with a sensing matrix for detecting and quantifying the analyte of interest. The sensing matrix produces a characteristic signal based on either absorbance or fluorescence which varies according to the concentration of the selected analyte in the sample. A photodetector measures the resulting optical signal from which the analyte concentration is determined.