In this work, we use a combination of transient absorption spectroscopy and global target analysis to measure excited-state lifetimes in a series of DNA-templated cyanine dye aggregates. For example, little is known about how the excited-state lifetime, a parameter essential to many applications, is influenced by structural factors, such as the number of dyes within the aggregate and their spatial arrangement. Although considerable progress has been made in characterizing the more » optical properties and associated electronic structures of these materials, less is known about their excited-state dynamics. These factors, combined with the programmability of DNA, raise the prospect of designer materials custom tailored for specific applications. Using DNA to template dye aggregation is attractive due to the relative ease with which DNA nanostructures can be assembled in solution, the diverse array of nanostructures that can be assembled, and the ability to precisely position dyes to within a few Angstroms of one another. = ,ĭNA-templated molecular (dye) aggregates are a novel class of materials that have garnered attention in a broad range of areas including light harvesting, sensing, and computing. Furthermore, the results allow conclusions to be drawn regarding the plausibility of the reduced species being responsible for light-induced blinking in more » direct stochastic optical reconstruction microscopy. The experimental absorption spectra recorded for the one-electron reduced radicals and the presumed dimer cation radical compare well to spectra obtained from time-dependent density functional theory calculations. Under anaerobic conditions, the transient species decay on the microsecond to millisecond time scale, with the mean lifetime depending on molecular structure, radiation dose, and dye concentration. In all cases, absorption maxima lie to the blue of the main ground-state transition. Relative to the ground state, absorption transitions for the various radicals are weak and somewhat broadened but do allow correlation with the π-conjugation length. The experiment allows recording of both differential absorption spectra and decay kinetics of the resultant one-electron reduced or oxidized transient species in water. Here, we examine a small series of cyanine dyes, possessing disparate π-conjugation lengths, under selective reducing or oxidizing conditions. There is, however, only scant literature information related to one-electron reduced cyanine dyes, especially in an aqueous environment. Light-induced blinking, an inherent feature of many forms of super-resolution microscopy, has been linked to transient reduction of the fluorescent cyanine dye used as an imaging agent.
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