Ratiometric optical sensor for dual sensing of temperature and oxygen

This paper proposes a ratiometric optical temperature and oxygen sensor that incorporates a sol–gel matrix doped with platinum tetrakis pentafluorophenyl porphine (PtTFPP) as the oxygen-sensitive material, 7-amino-4-trifluoromethyl coumarin (AFC) as the temperature-sensing material, and rhodamine 110 (Rh110) as the temperature/oxygen-independent fluorescent dye. The feasibility of coating a color sensor with the sensing film for fabricating a ratiometric optical dual sensing device is investigated. Using an LED with a central wavelength of 405 nm as the excitation source, it is shown that the emission wavelengths of the temperature-sensitive, oxygen-sensitive, and reference dyes have no spectral overlap and therefore permit the temperature and oxygen concentration to be measured using a ratiometric-based method. The ratiometric optical dual sensor was tested with regard to monitoring various temperatures and oxygen concentrations. The results show that the luminescence properties of the temperature sensor are independent of the presence of the oxygen sensor, and have a uniquely good linear response in the 25–65 °C range. The oxygen sensing scheme presented in this work is intended for use in temperature compensation. The proposed ratiometric sensing approach suppresses the effects of spurious fluctuations in the intensity of the excitation source.