Fluorescence time-resolved measurements

Investigation of water motion in AOT reverse micelles determining the solvent correlation function, C i), was first reported by Sarkar et al. [29]. They obtained time-resolved fluorescence measurements of C480 in an AOT reverse micellar solution with time resolution of > 50 ps and observed solvent relaxation rates with time constants ranging from 1.7 to 12 ns. They also attributed these dynamical changes to relaxation processes of water molecules in various environments of the water pool. In a similar study investigating the deuterium isotope effect on solvent motion in AOT reverse micelles. Das et al. [37] reported that the solvation dynamics of D2O is 1.5 times slower than H2O motion. 

The values of the rate constant ki were determined by time-resolved fluorescence measurements, and the values of log rc were plotted as a function of T — Tg (Figure B8.2.2). The data reveal an important effect of the chemical structure of the matrix and a good agreement with the WLF equation in all cases. 

C. D. Stubbs, K. Kinosita, Jr., F. Munkonge, P. J. Quinn, and A. Ikegami, The dynamics of lipid motion in sarcoplasmic reticulum membranes determined by steady-state and time-resolved fluorescence measurements on l,6-diphenyl-l,3,5-hexatriene and related molecules, Biochim. Biophys. Acta 775, 374-380 (1984). 

M. G. Badea and L. Brand, Time-resolved fluorescence measurements, Methods Enzymol. 61, 378-425 (1979). 

In the first example, we describe time-resolved fluorescence measurements of a fluorescent bead (Fujino and Tahara 2004). Figure 3.6a shows the CCD image of a commercial fluorescent bead that has a diameter of -4.85 pm (Mag Sphere). This bead was laser trapped near the focus point by the excitation pulse. In fact, when the irradiation... 

The transient absorption spectrum of DMABN-F4 in acetonitrile, recorded at 1-ps delay shows an absorption band near 360 nm (Fig. 3a). This band can be attributed to the CT state by comparison with that reported for DMABN in acetonitrile at lOOps (Fig. 3b). For the latter, both the LE state decay and CT state risetime were found to be 6 ps in time-resolved fluorescence measurements with a 4-ps time-resolution streak-camera [6]. From various studies, the CT formation time is now well known to be 4-6 ps [1] so that, at 100 ps, only the CT state is present. Fig. 3a shows that, for DMABN-F4, the CT state is populated in less than 1 ps in acetonitrile. We can thus conclude from the present observation that the access to the CT state for DMABN-F4 is significantly faster than for DMABN in acetonitrile. 

Various mechanisms for the photoinduced geometrical isomerization of 9-styrylanthracenes have been proposed recently [90-93]. From steady-state and time-resolved fluorescence measurements on the parent 9-styrylanth-racenes 68a/69a and their formyl and 4-phenylsulfonyl derivatives (681/691 68j/69j), it has been concluded that the geometrical isomerization is an adiabatic process which occurs both in the excited singlet and triplet states [90]. Thus, for the conversion of the parent cis compound 68a into 69a, 85%... 

We further carried out time-resolved fluorescence measurement on a single fluorescent spot of the individual enzyme-TNP-ATP complexes. Figure 24A and B shows a representative fluorescence decay curve and fluorescence spectrums of single enzyme-TNP-ATP complexes. The fluorescence spectrum varied from spot to spot, as an indication of fluorescence from individual complexes. The decay curve cannot be fitted to a single exponential, but was well fitted to a... 

Kumke, M. U., Abbt-Braun, G., and Frimmel, F. H. (1998). Time-resolved fluorescence measurements of aquatic natural organic matter (NOM). Acta Hydrochim. Hydrobiol. 26, 73-81. 

Hibara, A., Saito, T., Kim, H.-B., Tokeshi, M., Ooi, T., Nakao, M., Kitamori, T., Nanochannels on a fused-silica microchip and liquid properties investigation by time-resolved fluorescence measurements. Anal. Chem. 2002, 74(24), 6170-6176. 

The monolayer also provides an environment of variable dielectric so that intermolecular association between photoactive molecules can readily occur. For example, molecular association of pyrene within a Langmuir-Blodgett film is clearly seen through time-resolved fluorescence measurements on the picosecond timescale [92], Attenuated total reflectance studies of dyes in cast films can similarly reveal their positions and photophysical interactions [93], Photochromism in a monolayer assembly has been attributed to excitation of ion-pair charge transfer complexes formed within the array [94]. 

A time-resolved fluorescence measurement collects the emission spectra at regular time intervals after the excitation, defined at t=0, from which one constructs the normalized solvation dynamics response function, S(t) = [hv(t)—hv(oo)]/[hv(0)— hv(oo)] [55], In our simulations, hundreds of uncorrelated equilibrium molecular configurations with the electron in its ground state were selected as initial configurations (t=0). From each of these initial configurations, the electronic state is adiabatically promoted to the first excited state, the system is then propagated in... 

The cyclodextrin-sandwiched porphyrin 18 of Kuroda [98] effectively recognizes hydrophobic quinones in water, with association constants ranging from A a = 7.4 X 10 M for 1,4-naphthoquinone to Ka > 5 x 10 M for an adamantyl-functionalized benzoquinone. In contrast, the association of p-benzoquinone is negligible. Molecular modeling predicts that the quinone approaches the porphyrin from an out-of-plane direction. Time-resolved fluorescence measurements give an estimate of the intramolecular electron transfer rate constant on the order of 10 s for all quinones studied. 

The quantum yields of fluorescence and phosphorescence, 4>f and d>p, may be determined experimentally by means of a fluorescent standard such as a rhodamine B solution whose independent of the exciting wavelength within a wide range. Lifetimes rp and rp are also experimentally accessible through time-resolved fluorescence measurements (phase method or single-photon counting) or by measuring the time dependence of phosphorescence. (Cf. Rabek, 1982.) In Table 5.2 the observable quantities and their relationship to rate constants are collected. 

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