Linking single-molecule blinking to chromophore structure and redox potentials.

ABSTRACT

Intensity fluctuations between an ON-state and an OFF-state, also called blinking, are common to all luminescent objects when studied at the level of individuals. We studied blinking of three dyes from a homologous series (Cy3, Cy5, Cy7). The underlying radical anion states were induced by removing oxidants (i.e. oxygen) and by adding the reductant ascorbic acid. We find that for different conditions with distinct levels of oxidants in solution the OFF-state lifetime always increases in the order Cy3anion that are unexpectedly low at the assumed oxygen concentration. On the other hand, reaction rates meet the expectations of similar Rehm-Weller plots when methylviologen is used as oxidant, confirming the model of photoinduced reduction and oxidation reactions. The relation of OFF-state lifetimes to redox potentials might enable predictions about the nature of dark states, depending on the fluorophores' nano-environment in super-resolution microscopy.