1 September 2009 Time-resolved fluorescence and FCS studies of dye-doped DNA
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Fluorescence lifetime, anisotropy and intensity dependent single molecule fluorescence correlation spectroscopy (I-FCS) are used to investigate the mechanism of fluorescence saturation in a free and nucleotide bound fluorophore (NR6104) in an antioxidising ascorbate buffer. Nucleotide attachment does not appreciably affect the fluorescence lifetime of the probe and there is a decrease in the rate of intersystem crossing relative to that of triplet state deactivation. The triplet state fraction is seen to plateau at 72% (G-attached) and 80% (free fluorophore) in agreement with these observations. Measurements of translational diffusion times show no intensity dependence for excitation intensities between 1 and 105kW cm-2 and photobleaching is therefore negligible. The dominant mechanism of fluorescence saturation is thus triplet state formation. I-FCS measurements for Rhodamine 6G in water were compared with those in the ascorbate buffer. In water the triplet fraction was saturated at considerably higher powers (45% at ca. 1.5 × 103kW cm-2) than in the ascorbate buffer (55%ca. 1 1kW cm-2)
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N. Nicolaou, N. Nicolaou, R. J. Marsh, R. J. Marsh, T. Blacker, T. Blacker, D. A. Armoogum, D. A. Armoogum, A. J. Bain, A. J. Bain, } "Time-resolved fluorescence and FCS studies of dye-doped DNA", Proc. SPIE 7393, Nanophotonic Materials VI, 73930L (1 September 2009); doi: 10.1117/12.826043; https://doi.org/10.1117/12.826043

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