CONTROLLING THE RESPONSE CHARACTERISTICS OF LUMINESCENT PORPHYRIN PLASTIC FILM SENSORS FOR OXYGEN

Two porphyrins, platinum(II) octaethylporphyrin (Pt-OEP) and palladium (II) octaethylporphyrin (Pd-OEP), are incorporated into a wide variety of different encapsulating matricies and tested as oxygen sensors, Th e excited state lifetimes of the two porphyrins are quite different, 0 .091 ms for Pt-OEP and 0.99 ms for Pd-OEP, and Pt-OEP-based oxygen sen sors are found to be much less sensitive than Pd-OEP-based ones to que nching by oxygen, Two major response characteristics of an oxygen sens or are (i) its sensitivity toward oxygen and (ii) its response and rec overy times when exposed to an alternating atmosphere of nitrogen and air. The response characteristics of a rang of Pt-OEP, and Pd-OEP-base d oxygen sensors were determined using cellulose acetate butyrate (CAB ), poly(methyl methacrylate) (PMMA), and PMMA/CAB polymer blends as th e encapsulating media. Pt-OEP and Pd-OEP oxygen sensors have better re sponse characteristics (i.e., more sensitive and lower response and re covery times) when CAB is used as the encapsulating medium rather than PMMA. For both Pt-OEP- and Pd-OEP-based oxygen sensors, in either pol ymer, increasing the level of tributyl phosphate plasticizer improves the response characteristics of the final oxygen-sensitive film. Pt-OE P in different unplasticized PMMA/CAB blended films produced a range o f oxygen sensors in which the response characteristics improved with i ncreasing level of CAB present.