Photophysics and photochemistry of oxygen sensors based on luminescent transition-metal complexes

A detailed study of the photophysics and photochemistry of -immobilized luminescent transition-metal complex sensors is presented. Emphasis is on understanding underlying origin of the nonlinear Stern-Volmer quenching response. Microheterogeneity is important in both photophysical and photochemical behavior, and the nonlinear responses in RTV 118 silicone rubber can be adequately described by a two-site model, although detailed measurements suggest a more complex Underlying. Counterion studies with quenching counterions are to be useful probes of the structure of the complex in polymer. While oxygen enhances photochemical instability, singlet oxygen is not directly implicated in sensor decomposition. In the photochemistry there is at least one reactive and one much less reactive site, although the photochemistry and quenching measurements probably sample different populations of sites. The existence of reactive sites suggests that stability can be enhanced by a preliminary photolysis to eliminate the more reactive sites.