What is the principle of oxygen measurement based on fluorescence quenching?
Optical oxygen sensors are based on the property of molecular oxygen quenching of fluorescence. The luminescent probe molecules are encapsulated in a gas permeable, but ion impermeable, material and coated on the optical probe tip. Upon irradiation of the luminescent molecules by an excitation light (blue), a fluorescence (red) emits from the probe tip. In the presence of oxygen, the fluorescence is reversibly and quantitatively quenched by oxygen due to form charge transfer complex. Reversible quenching of the luminescent dyes by oxygen has been found to obey the Stern-Volmer equation: I0/I = 1 + Ksv*pO2 (1) where Io and I are the intensities of the fluorescence in the absence and presence, respectively, of oxygen at partial pressure pO2, and Ksv is the Stern-Volmer constant. The Ksv depends directly upon the rate constant for the diffusion of oxygen, the solubility of oxygen, and the natural lifetime of the electronically excited state of the lumophore in the matrix. Equation 1 appli