Reduced blinking and long-lasting fluorescence of single fluorophores coupling to silver nanoparticles.

The fluorescence signal of single organic fluorophores is characterized by random blinking and irreversible photobleaching. Photoinduced blinking of Cy5 has posed various limitations of this popular near-infrared (NIR) probe in biological applications. Here we show that fluorophore-metal nanoparticle (NP) complexes greatly suppress Cy5 blinking and noticeably reduce photobleaching events. The blinking behavior of single Cy5 molecules was investigated and compared in the absence and the presence of silver nanostructures. A power-law distribution of off time population was observed for single Cy5 molecules. Average off times were compared to evaluate the plasmonic effect of silver nanoparticles on the triplet decay rates. We furthermore demonstrate enhanced photostability in the presence of silver NPs. The results show that plasmonic-controlled fluorescence can lead to a novel physical mechanism to enhance fluorescence intensity, reduce blinking, and increase photostability.