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This thesis focuses on investigations of transient dark states of fluorescent molecules using spectroscopic techniques. The main purpose is to show and convince the reader that transient dark states are not always a nuisance, but also represent an additional source of information. Several studies with fluo-rescence correlation spectroscopy were performed,(More)
Inter- or intramolecular distances of biomolecules can be studied by Förster resonance energy transfer (FRET). For most FRET methods, the observable range of distances is limited to 1-10 nm, and the labeling efficiency has to be controlled carefully to obtain accurate distance determinations, especially for intensity-based methods. In this study, we exploit(More)
Electrostatic interactions between dielectric surfaces and different fluorophores used in ultrasensitive fluorescence microscopy are investigated using objective-based Total Internal Reflection Fluorescence Correlation Spectroscopy (TIR-FCS). The interfacial dynamics of cationic rhodamine 123 and rhodamine 6G, anionic/dianionic fluorescein, zwitterionic(More)
In this work, fluorescence correlation spectroscopy (FCS) was used to investigate the effects of potassium iodide (KI) on the electronic-state population kinetics of a range of organic dyes in the visible wavelength range. Apart from a heavy atom effect promoting intersystem crossing to the triplet states in all dyes, KI was also found to enhance the(More)
For a spatially restricted excitation volume, the effective modulation of the excitation in time is influenced by the passage times of the molecules through the excitation volume. By applying an additional time-modulated excitation, the buildup of photoinduced reversible dark states in fluorescent molecules can be made to vary significantly with their(More)
In this work, Fluorescence Correlation Spectroscopy (FCS) was used to investigate the effects of potassium io-dide (KI) on the electronic state population kinetics of a range of organic dyes in the visible wavelength range. Apart from a heavy atom effect promoting intersystem crossing to the triplet states in all dyes, KI was also found to enhance the(More)
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