Naphthalene fluorescence lifetime

Photoinduced excited states of the naphthalene derivatives included in the amphiphilic p-CD LB films were found to be stablized by measurements of the fluorescence lifetimes and the excimer formation of the naphthalene derivatives adsorbed by the CD monolayer occured mainly between the adjacent layers [29]. 

Nemzek and Ware [7] have studied the fluorescence decay of 1,2-benzanthracene (and naphthalene) in 1,2-propanediol or purified mineral oil by the single photon counting technique over the temperature range 10—45°C. The fluorescence lifetimes, t0, were measured. In further experiments, which included a heavy atom fluorescence quencher, carbon tetrabromide in concentration [Q] 0.05—0.29 mol dm-3, no longer could the decay be characterised by an exponential with a constant lifetime. However, the decay of fluorescence was well described by an expression of the form... 

The unimolecular micellar characteristics of this poly(ammonium carboxylate) 156 were demonstrated 179 by UV analysis of guest molecules, such as pinacyanol chloride, phenol blue, and naphthalene combined with fluorescence lifetime decay experiments employing diphenylhexatriene as a molecular probe. The monodispersity, or absence of intermolecular aggregation, and molecular size were determined by electron microscopy. 

All data obtained with Tecan Ultra Evolution MTP reader. The following excitation and emission wavelengths were used EDANS and AMC 350 and 500 nm RhllO 485 and 535 nm TAMRA 535 and 595 nm PT14 405 and 450 nm. 4 = primary cleavage site confirmed by MS. AMC = aminomethylcoumarin. RhllO = rhodamine 110. yE = glutamic acid attached to RhllO via its carbonic acid in side chain. EDANS = fluorophore 5-[(2-aminoethyl)amino]naphthalene-l-sulphonic acid. DABCYL = 4-(4-dimethylaminophenylazo)benzoic acid quencher. BTN = biotin. PT14 = acridone-based fluorescence lifetime label. 

Natural sunlight induced photooxidation of naphthalene in aqueous solution has also been reported by McConkey et al. to produce six major products including 1-naphthol, coumarin, and two hydroxyquinone [9]. The authors proposed that the initially formed 2 + 2 and 2 + 4 photo cyclo addition products undergo subsequent oxidation and/or rearrangement to form the observed products [9]. Grabner et al. have studied solvent effects on the photophysics of naphthalene and report that fluorescence lifetime decreases by a factor of 2.5 in aqueous solution compared to organic solvents (e.g. ethanol, hexane, acetonitrile) [10]. Based on the observed differences in naphthalene excited triplet state properties in aqueous and organic media, the decrease... 

Roek, D.P. Chateauneuf, J.E. Brennecke, J.F. A fluorescence lifetime and integral equation study of the quenching of naphthalene fluorescenceby bromoethane in super-and subcritical ethane. Ind. Eng. Chem. Res. 2000, 39, 3090. 

Fig. 16.4 Correlation between the fluorescence lifetime rp and the longitudinal dielectric relaxation time, TL (Eq. (15.19)) of 6-A -(4-methylphenylamino-2-naphthalene-sulfonW,iV-dimethylaniide) (TNSDMA) and 4-N, A-dimethylaminobenzonitrile (DMAB) in linear alcohol solvents. The fluorescence signal is used to monitor an electron transfer process that precedes it. The line is drawn with a slope of 1. (From E. M. Kosower and D. Huppert, Ann. Rev. Phys. Chem. 37,127 (1986) see there for original publications.)...

The naphthalene monomer fluorescence lifetime is shortened by the solubilized Anth to an extent in reasonable agreement with the observed v values. Following the general analysis of Fredrickson and Frank , we have argued that x can be estimated from the fluorescence decay from the expression... 

The product e N G (t) is the decay function for the monomer naphthalene singlet state where kj is the unperturbed naphthalene lifetime and Cjj(t) is a general, non-exponential function that describes the naphthalene fluorescence decay In the presence of X mole fraction of mergy accepter. Using our multlexponentlal... 

The other aromatic hydrocarbons capable of intermolecular excimer formation (10-14), i.e. benzene, naphthalene, 9,10-al)cylated anthracenes,1,2-benzanthracene and also perylene, have considerably smaller values for the ratio shorter fluorescence lifetimes... 

As far as the excimer decay kinetics of PAA in aqueous media is concerned, de Melo and coworkers [122,130,131] have investigated the time-resolved fluorescence from a series of samples modified with various amounts of pyrene and naphthalene, respectively. Even when the aromatic content was as low as 2mol%, excimer formation was evident in the steady-state spectra. The fluorescence decays were complex irrespective of the label and were best modeled by a triple-exponential function (as in Eq. 2.8) both when emission was sampled in the monomer and excimer regions. In contrast to the distribution of rate constants in the blob model [133,134], the authors favored a scheme that describes the decay kinetics in terms of discrete rate constants. The data were also consistent with previous schemes [124-127] that account for the presence of two distinct types of monomer in addition to that of excimer in macromolecular systems one monomer enjoys kinetic isolation and is unable to form excimers, whereas the second is able to participate in excimer formation within its fluorescence lifetime. The authors [130] concluded from both steady-state and time-resolved data that PAA undergoes a conformational change from a compact form in acidic solution to an open coil at high pH. Furthermore, as the... 

Figure 8. Excitation energy dependence of the S, decay rate (reciprocal of the measured fluorescence lifetime) in vapor-phase naphthalenes. Excitation source was a deuterium flash lamp. (From ref. [4] with permission.)...

Furthermore, Payer and co-workers have recently reported" detailed results of the concentration dependence of the photon echo decay in the mixed crystal of pentacene in naphthalene. At low guest concentration they find that at 1.4K r, whereby ry, is the fluorescence lifetime. 

Excited singlet lifetimes, also called fluorescence lifetimes, of organic molecules are normally smaller than 10 ns. Notable exceptions are polycyclic aromatic hydrocarbons, such as pyrene and naphthalene. Due to their short lifetimes, fluorescent probes can only explore a small volume therefore, competition between the probe s decay to the ground state and dissociation from the supramolecular structure to the homogeneous phase occurs only infrequently. For example, in order to compete with the decay of the excited state, a probe with a 10 ns excited state lifetime must possess a dissociation rate constant from the supramolecular structure that is larger than 10 s. For this reason, fluorescent probes are normally assumed not to relocate during their lifetimes hence, explore a very limited volume. 

However maquettes for the design of redox proteins were proposed, based on a three helix bundle with a capping Co(III) (bipyridine)3 electron acceptor at the N-terminus and an electron donor at the C-terminus (199, 200). These proteins were tested for LRET. The a-helical percent was adjusted by addition of urea or trifluoroethanol (201, 202). Intriguingly, studies of one of the proteins (l6-mer-three helix bundle) shows a 2-fold higher LRET rate constant when the percent of helicity is 77% than when it is 0% (denatured in urea). However authors indicate that the kinetics is not a simple first-order one in the presence of urea. They interprete these data as coming from different donor-acceptor distances. The distribution of distances was determined by fluorescence lifetimes fit. Both when helicity is 0% or 77%, distributions peak around 18 A for the Ru(II) (16-mer)3-A (where A=5-((((2-acetyl)amino]ethyl)amino)-naphthalene-l sulfonic acid). Actually the distance appears 0.7A shorter for a-helix which is found consistent with the increased rate constant, by the authors. 

Fluorescence lifetime data of 1, 4, 5, and 6 in presence of 10 M -CD were collected with frequency-domain fluorometry. These probes gave only 1 1 complexes with P-CD [58] and, given the association constant values, the complex molar fraction was >0.95 for 4 and 5 and 0.1 for 6. The fluorescence decay of all the probes was best described by unimodal Lorentzian lifetime distribution [51,59] rather than by a mono- or biexponential function corresponding to the emission of the complexed and the free probe. This distribution was attributed to the coexistence of molecules included in the cavity to different extents. It was proposed that, in the case of 4, the apolar benzene ring enters the cavity first and penetrates until the whole naphthalene is included. This is the most stable and, hence, the most populated conformation of the complex. The distribution of the lifetimes suggests that at any time there is an ensemble of molecules in different stages of complexation which have slightly different lifetimes. 

Molecular inclusion was demonstrated by the aqueous solubilization and UV and fluorescence analysis of the guest dyes phenol blue (8), pinacyanol chloride (9). chlortetracycline (10).and naphthalene (11).Fluorescence lifetime decay experiments using 1,6-diphenylhexatriene (12) as the probe further supported the host-guest relationship while electron microscopy (EM) coirobo-rated the single molecule, non-aggregated state. Calculated molecular modeling diameters o/48 A in a fully extended conformation were also substantiated via EM. 

The intersystem crossing is practically unaffected by collisions. If initial populations of Si vibronic levels are close to the Boltzmann equilibrium (this may be done by a simultaneous pumping of the Oo band and of the neighbor sequence bands), the fluorescence lifetime of naphthalene is independent of the added gas pressure (Soep et ai, 1973). The initial triplet yield is equally pressure independent (Schroder et ai, 1978). 

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