Detection and characterization of single molecules in aqueous solution |
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Authors: | C Zander M Sauer K H Drexhage D -S Ko A Schulz J Wolfrum L Brand C Eggeling C A M Seidel |
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Institution: | (1) Institut für Physikalische Chemie, Universität-Gesamthochschule Siegen, Adolf-Reichwein-Straße 2, 57068 Siegen, Germany;(2) Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany;(3) Max-Planck-Institut für Biophysikalische Chemie, Am Faßberg 11, 37077 Göttingen, Germany |
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Abstract: | Using a confocal microscope with a single-photon avalanche photodiode as detector, we studied photon bursts of single Rhodamine 6G (R6G) and Rhodamin B-zwitterion (RB) molecules in aqueous solution by excitation of the lowest excited singlet stateS
1 with a frequency-doubled titanium: sapphire laser. Multichannel scaler traces, the fluorescence autocorrelation function and fluorescence decay times determined by time-correlated single-photon counting have been measured simultaneously. The time-resolved fluorescence signals were analyzed with a maximum likelihood estimator. Fluorescence lifetime patterns in steps of 100 ps were generated by convolution with the excitation pulse. The lifetime of theS
1 state was derived from the Kullback-Leibler minimum discrimination information. We are able to demonstrate for the first time identification of two different single dye molecules via their characteristic fluorescence lifetimes of 1.79 ± 0.33 ns (RB) and 3.79 ± 0.38 ns (R6G) in aqueous solution.Dedicated to Prof. F. P. Schäfer on the occasion of his 65th birthday.On leave from Department of Physics, Mokwon University, Taejon, 301-729, Korea |
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