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

Abstract

A detailed study of the photophysics and photochemistry of polymer-immobilized luminescent transition-metal complex oxygen sensors is presented. Emphasis is on understanding the underlying origin of the nonlinear Stern-Volmer quenching response. Microheterogeneity is important in both photophysical and photochemical behavior, and the nonlinear quenching responses in RTV 118 silicone rubber can be adequately described by a two-site model, although detailed lifetime measurements suggest a more complex Underlying system. Counterion studies with quenching counterions are shown to be useful probes of the structure of the complex in the polymer. While oxygen enhances photochemical instability, singlet oxygen is not directly implicated in sensor decomposition. I n 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.

Oxygen and temperature sensitivity of blue to green to yellow light-emitting Pt(ii) complexes

“…Generally, the oxygen sensitivity of the studied platinum complexes is very weak in contrast to other phosphorescent metal complexes such as platinum(II)-porphyrins, 22,44,45 ruthenium(III), 46 Fig (2). τ 0 refers to the lifetime at 10 kPa pO 2 and 30°C.…”

Exceptional Oxygen Sensing Properties of New Blue Light‐Excitable Highly Luminescent Europium(III) and Gadolinium(III) Complexes

“…4B and 4C) which is a typical case for the state-of-the-art oxygen sensors. The Stern-Volmer plots can be fitted by so-called "twosite model" assuming localization of the dye in two different environments: [77] ( 1) where f 1 and f 2 are the fractions of the total emission for each environment, respectively (with f 1 + f 2 being 1), and and are the Stern-Volmer constants for each component. Although the equation is physically meaningful for the intensity only, it can often be used to fit the decay time plots as well.…”

Fluorescent Microparticles for Sensing Cell Microenvironment Oxygen Levels within 3D Scaffolds

“…Reported values for f 1 have ranged from 0.97 for the Ru(Ph 2 phen 3 )Cl 2 luminophore in PDMS films [14], to 0.73 in poly(styrene) films [23], and to 0.61 while adsorbed on mesoporous silica particles suspended in selfassembled polymer films [24]. The value obtained from our experiments is closer to that obtained by Carraway et al [14], which pertains to Ru(Ph 2 phen 3 )Cl 2 in PDMS. Our result reflects that approximately 90% of the available oxygen-sensitive luminophore is quenched under our particular testing conditions.…”

“…First, we adapted a conventional Stern-Volmer model that describes the relationship between fluorescence intensity of the Ru(Ph 2 phen 3 )Cl 2 luminophore and oxygen concentration and normalizes the fluorescence intensity of Ru(Ph 2 phen 3 )Cl 2 with the Nile blue chloride reference fluorophore: (1) where I R,0 and I R are the ratios of the fluorescence intensities of Ru(Ph 2 phen 3 )Cl 2 and Nile blue chloride in the absence and presence of oxygen respectively, K SV is the Stern-Volmer quenching constant, and [O 2 ] is the concentration of oxygen. Second, we also applied a twosite Stern-Volmer model: (2) This model, proposed by Carraway et al [14], states that the oxygen-sensitive luminophore is distributed mainly in two populations through the matrix of a polymer, a quenched population and an unquenched population (with fractions f 1 and f 2 respectively), each with its own quenching constant (K SV,1 and K SV,2 ). The quenching constant for the unquenched population (K SV,2 ) is very small and is generally assumed to be negligible.…”