Evaluating singlet oxygen-generating photoresponsive materials and their cross-reactivity for photoelectroanalysis

Type II photosensitizers (PSs) are chromophores that, upon light absorption, induce photochemical reactions, particularly in generating singlet oxygen (1O2). Over the years, PSs have gained importance in various fields. However, their use as photoresponsive materials in electroanalysis is in its early stages. This study investigates water-soluble PSs across various classes (i.e. chlorin, porphyrin, xanthene and phenothiazine derivatives) for their potential application as photoresponsive materials in photoelectrochemical analysis. A novel methodology utilizing multi-wavelength LEDs and screen-printed electrodes (SPEs) is developed to assess the PS photocatalytic activity and cross-reactivity. The cross-reactivity, defined as the PS's ability to produce 1O2 only when illuminated with a specific LED wavelength (lambda LED), is systematically analyzed in the context of multiplexed photoelectrochemical analysis. PSs like chlorin e6 and pheophorbide A exhibit higher cross-reactivity due to the presence of multiple peak maxima in their absorption spectra and aggregation effects, while others like eosin Y, TMPyP4 and methylene blue demonstrate lower cross-reactivity, showcasing the great potential of PSs as photoresponsive materials attached to detection target molecules (e.g. nucleic acids, proteins or antibodies). This research highlights the importance of PS selection based on cross-reactivity profiles and photocurrent responses, paving the way for the development of new multiplexing strategies.