Effects of Plasticizers on Fluorescence Quenching Properties of Oxygen-Sensing Films with a Polymer Matrix
Oxygen sensing films comprising PtTFPP as a fluorescent indicator,polyvinyl chloride(PVC)as matrix with tributyl citrate(TBC)plasticizer were fabricated in this study.The films were prepared using a tape casting technique,and their fluorescence lifetimes were measured using the phase-modulation method.The results demonstrated that the addition of 40% TBC significantly increased the oxygen permeability of the PVC matrix,resulting in an enhanced fluorescence quenching effect.At 20 kPa oxygen partial pressure,the fluorescence lifetime decreased substantially from 69.8 μs to 16.3 µs.The Ksv constant which characterizes the film's sensitivity to oxygen increased from 0.013 kPa-1 to 0.375 kPa-1.The fluorescence lifetime exhibited a two-site Stern-Volmer behavior in response to changes in oxygen partial pressure,which is attributed to the variation in oxygen concentration between the film's surface and interior,leading to strong and weak fluorescence quenching effects.When the atmosphere was switched from nitrogen to air,the response time of the fluorescence phase signal to variations in gas-phase oxygen partial pressure was 4.5 s for the TBC-containing sample,much shorter than that of the sample without TBC(30.5 s).These findings contribute to the development of oxygen sensors based on fluorescence quenching.