Self-quenching, of fluorescence

Sfen c factors. An interesting example of steric effects upon excimer formation is demonstrated by the anthracenes. Many anthracenes exhibit selfquenching of fluorescence and these results are shown in Table 1 (from Bouas-Laurent, et a ., 1980). As one moves from anthracene to 9-methylan-thracene and then to 9,10-dimethylanthracene one finds that the rate constant for self-quenching of fluorescence ( jq) decreases and so does the rate constant for photodimerisation For anthracene, the latter reaction is very... 

Lakowicz, J. R., Malicka, J., D Auria, S., Gryczynski, I. (2003). Release of the self-quenching of fluorescence near silver metallic surfaces Anal. Biochem. 320 13-20. 

X 10 mol L range, with a detection limit of 0.27 jM. The fluorescence energy transfer between ferrocene donor and porphyrin acceptor was also considered. Nanofibers with distinct luminescent property were fabricated by electrospinning porphyrinated polyimides. The new material demonstrated to be a very interesting sensory material for detection of trace amounts of TNT vapor (10 ppb) [249]. The presence of covalently bonded porphyrin fluorophores in the main chain diminish the aggregation-induced self-quenching of fluorescence and improves the physicochemical stability of the polyimide nanofibers. 

Phillips RL, Kim IB, Tolbert LM, Bunz UHF (2008) Fluorescence self-quenching of a mannosylated poly(p-phenyleneethynylene) induced by concanavalin A. J Am Chem Soc 130 6952-6954... 

Figure 7 shows the self-quenching of the 660 nm fluorescence emission (normalized to relative intensity per chromophore using concentration values based on our aqueous subphase monolayer data) as a function of dilution of the ZnTOAPP by SA. A sharp decrease in the quenching occurs at ZnTOAPP SA ratios of 1 4, and a con-... 

Small chromophores, such as -alkylquinolinium, and isoquinolinium cations can also be intercalated into the galleries of a-ZrP. In most cases, this did not bring about any change in the fluorescence spectra from that observed in solution (acetonitrile). The fluorescence decays of the intercalated compounds were, however, nonexponential and contained a very short-lifetime component. High loadings resulted in self-quenching of the fluorescence and this contributed to the shorter-lived component for the intercalated dyes [58],... 

Figure 38 Stern-Volmer plot for self-quenching of the fluorescence lifetime of the intercalated component (0.008% BAZrP) as a function of Ru(bpy)2+ concentration. koha is the inverse of the luminescence lifetime. (From Ref. 76. Copyright 1995 The American Chemical Society.)...

In Section XIII.A this process was responsible for the delayed fluorescence. Here the self-quenching of triplets, following their electrochemical generation, lowers their quantum yield and resulting phosphorescence. 

Bimolecular constant for self-quenching of the fluorescence of substituted anthracenes... 

Finally, it should be mentioned that acetone itself quenches both its excited singlet and triplet states. A Stern-Volmer relation is obeyed by the self-quenching of phosphorence and probably of fluorescence as well . ... 

The self-quenching of the fluorescence and the decrease of the triplet yield with increasing acetone pressure were taken as evidence supporting the occurrence of step (3). It is to be noted, however, that these observations can also be interpreted in a different way. Even if step (3) occurs, it is of little importance a yield of approximately 0.02 was obtained at 50 torr pressure, 3130 A and 48 °C. 

Fluorescence emission data of the diporphyrins also are given in Table I the Q(0,0) band is red shifted and fluorescence yield is decreased. Although some reduction in is predicted by the exciton model (9), the extent of quenching found in the diporphyrins is certainly impressive. It is likely that the enormous red tail of the Soret band further enhances the self quenching of the dimer fluorescence yield. 

We have developed a direct and noninvasive method to determine Tg of polymers at the interface with solid substrates [54, 55]. The strategy is to use fluorescence lifetime measurements using evanescent wave excitation. Figure 15a shows PS-NBD, i.e., PS containing the dye 6-[A-(7-nitrobenz-2-oxa-l,3-diazol-4-yl)amino]hexanoic acid (NBD) [55]. The NBD fraction of PS was sufficiently low to avoid self-quenching of the dye. The NBD dye was excited with the second-harmonic generation of a mode-locked titanium sapphire laser equipped with a... 

Mixing of the P3HT with no appended units and the PDI molecule did not yield this kind of nanostructure, and the photophysical properties showed that the simple mixture did not lead to efficient charge transfer between the it-electron-rich and -deficient units, whereas in the copoly-mer-PDI system, a significant quenching of fluorescence was observed. This example shows how simple templates supported by robusf self-assembly of molecular componenfs can lead fo interesling functional nanomaterials. 

Scheme 7.2 Fluorescence (F) and phosphorescence (P). Normal fluorescence (F) arises from Sj (independently from which singlet has been initially reached, and thus its shape is not affected by the energy of the wavelength used, provided that this has been absorbed. This is the Vavilov rule, rationalized by Kasha as due to the fact that internal conversion among states of the same multiplicity is always the fastest process, see Chap. 3). Delayed fluorescence may involve triple-triplet annihilation, in which self-quenching of the triplet leads back to the singlet Sj, with the usual fluorescence spectrum but the triplet lifetime...

Ultra pH-sensitive (UPS) fluorescent nanoprobes with a 355-fold signal amplification in tumor relative to blood after systemic injection were recently established [40]. UPS probes possess an ultra pH-sensitive core copolymer (poly (ethylene glycol)-b-poly (2-(hexamethyleneimino) ethyl methacrylate) with micellar transitions within 0.25 pH units, fluorophores and cRGD for broad targeting of the tumor vasculature. The pH responsiveness is based on pH-dependent micellization of the core, micellization induced self-quenching of conjugated fluorophores (homoFRET), whereas micelle dissociation in acidic conditions resulted in an increased fluorescence signal. Systemic... 

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