Multipulse luminescence detection of the spatial distribution of reagents and the diffusion flow of O2 molecules into polymer layer

Abstract

The problem of monitoring processes involving molecular oxygen in porous media still remains relevant due to the development of technologies based on the use of nanostructured systems. It is becoming important to study the characteristics of the reactions in nano cells with different morphologies and connectivity. The specifics of the localization and transport of reagents, which determine the yield of the product during transformations, provide valuable information for analyzing the process and optimizing its flow conditions. In this regard, it is necessary to improve the methodology for measuring photoinduced signals of oxygen-containing systems in non-stationary modes with time resolution to determine the current concentrations of reactant molecules. The kinetics of oxidative photoreactions in a colored polymer film was studied with multiple pulse activation of the system taking into account the layer-by-layer diffusion replenishment of the concentration of oxygen consumed in the reaction from the atmosphere. The process of chemical binding of oxygen molecules with immobilized anthracene molecules in an oxygen-permeable polymer film of polyvinyl butyral containing molecules of an organic dye (erythrosine) as a photosensitizer was recorded. A mathematical model is proposed that describes the kinetics of oxygen-dependent photoreactions in the film and the formation of luminescent response signals during its multi-pulse laser activation taking into account the diffusion replenishment of oxygen molecules in the intervals between the activating pulses. Based on a comparative analysis of the experimental and calculated luminescence signals, the nature of the non-uniform spatial distribution of the photosensitizer and the oxidized reagent in the polymer film is assessed.