@article {35076,
	title = {Redox-Controlled Energy Transfer Quenching of Fluorophore-Labeled DNA SAMs Enables In Situ Study of These Complex Electrochemical Interfaces},
	journal = {Journal of the American Chemical Society},
	volume = {144},
	year = {2022},
	pages = {23428{\textendash}23437},
	abstract = {<p>Interfaces modified by a molecular monolayer can be challenging to study, particularly in situ, requiring novel approaches. Coupling electrochemical and optical approaches can be useful when signals are correlated. Here we detail a methodology that uses redox electrochemistry to control surface-based fluorescence intensity for detecting DNA hybridization and studying the uniformity of the surface response. A mixed composition single-strand DNA SAM was prepared using potential-assisted thiol exchange with two alkylthiol-modified ssDNAs that were either labeled with a fluorophore (AlexaFluor488) or a methylene blue (MB) redox tag. A significant change in fluorescence was observed when reducing MB to colorless leuco-MB. In situ fluorescence microscopy on a single-crystal gold bead electrode showed that fluorescence intensity depended on (1) the potential controlling the oxidation state of MB, (2) the surface density of DNA, (3) the MB:AlexFluor488 ratio in the DNA SAM, and (4) the local environment around the DNA SAM. MB efficiently quenched AlexaFluor488 fluorescence. Reduction of MB showed a significant increase in fluorescence resulting from a decrease in quenching or energy transfer efficiency. Hybridization of DNA SAMs with its unlabeled complement showed a large increase in fluorescence due to MB reduction for surfaces with sufficient DNA coverage. Comparing electrochemical\&ndash;fluorescence measurements to electrochemical (SWV) measurements showed an improvement in detection of a small fraction of hybridized DNA SAM for surfaces with optimal DNA SAM composition and coverage. Additionally, this coupled electrochemical redox-fluorescence microscopy method can measure the spatial heterogeneity of electron-transfer kinetics and the influence of the local interfacial environment.</p>},
	issn = {0002-7863},
	doi = {10.1021/jacs.2c09474},
	author = {Ma, Tianxiao and Grzedowski, Adrian Jan and Doneux, Thomas and Bizzotto, Dan}
}
