A Comprehensive Investigation Into How Metal Nanoparticles Enhance Photochemical Processes

Integrated nanoparticle-fluorophore systems are an emerging class of hybrid materials with potential for a variety of applications. Within these systems, Metal-Enhanced Fluorescence (MEF) is a phenomenon that arises through the unique near-field interactions between organic fluorophores and metallic nanoparticles. These interactions can enhance fluorophore brightness by operating under two mechanistic pathways: increased fluorophore excitation, and increased fluorophore emission. It is critical, however, to garner an understanding of the balance between the two mechanisms in order to optimize its use for customized applications. In this work, silver nanoplates (AgNP) were synergistically integrated with a photoactivatable system consisting of a fluorogenic boron dipyrromethene (BODIPY) and select photoacid generators (PAGs). Light irradiation of the PAGs promotes the release of acid, which encourages the formation of a fluorescent BODIPY analogue. AgNP were found to enhance the output of steady-state emission via MEF. Furthermore, single molecule total internal reflection fluorescence microscopy (TIRFM) was executed to distinguish the relative contributions of the two MEF mechanisms between the quenched and fluorescent BODIPY fluorochromes and AgNP. Interestingly, increased excitation was the dominant MEF mechanism amongst both dyes. Finally, the rational design of a ‘uninanomolecular’ superstructure incorporating both a photoactivatable dihydrofluorescein dye and AgNP within a single system was investigated. Two synthetic approaches were proposed, however neither method yielded superstructures that photoactivated with subsequent MEF. Overall, this work aids to advance the understanding of complex particle-molecule interactions.