Pyrene emission

Figure 13.8 /3//1 ratio of pyrene emission as a function of dendrimer generation. Modified from ref. 17... 

Fig. 17 Ratio of third to first vibrational peak of pyrene emission spectrum as a function of DTAB concentration in the presence of 1 g/L sodium polyacrylate...

Fig. 46 Pyrene monomer and excimer decay profiles in SDS micellar solutions [SDS] = 8.2 X 10 kmolm , [NaCl] = 10 kmolm , CMC = 1.5 x 10" kmolm", pyrene levels are indicated as the ratio of micellized SDS to added pyrene emission monitored at 383 nm for monomer and 480 nm for excimer. (A) Monomer emission for SDS/Py = 2160, (B) monomer emission for SDS/Py 108 (C) excimer emission for SDS/Py = 108...

Fig. 47 Pyrene emission spectra in SDS micellar solutions under varying levels of pyrene (A and B correspond to pyrene levels as indicated in Fig. 46)...

Fig. 16 Estimated environmental distributions of benzo[a]pyrene emissions to the atmosphere (a) and ambient air concentrations over Europe (b) (Gusev et al. 2007)...

In this paper, we present a preliminary analysis of the steady-state and time-resolved fluorescence of pyrene in supercritical C02. In addition, we employ steady-state absorbance spectroscopy to determine pyrene solubility and determine the ground-state interactions. Similarly, the steady-state excitation and emission spectra gives us qualitative insights into the excimer formation process. Finally, time-resolved fluorescence experiments yield the entire ensemble of rate coefficients associated with the observed pyrene emission (Figure 1). From these rates we can then determine if the excimer formation process is diffusion controlled in supercritical C02. 

Figure 8 shows a pair of typical time-resolved fluorescence decay traces for 100 / M pyrene in supercritical CO2 (Tr = 1.02 pr = 1.17). Note that the ordinate is logarithmic. The upper and lower panels show results for selective observation in the monomer (400 +. 10 nm) and excimer (460 + 10 nm) regions of the pyrene emission spectrum. Several interesting features are apparent from these traces. First, both decay processes are not single exponential. Second, the excimer emission has a significant contribution from a species that "grows in" between 30 - 75 ns this is a result of the excimer taking time to form (i.e., k in Figure 1). Third, the fits between the experimental data and the model shown in Figure 1 are good. Detailed analysis of these decay traces (10,11,21-26) yields the entire ensemble of photophysical kinetic parameters for the pyrene excimer in supercritical C02.

FIGURE 13.22 Plots of the uorescence inteniiftsnd intensity rati ofei /13 (from pyrene emission spectra) andl333/l338 as a function of PSTj-poly(sodium acrylate) concentration. Values of C are indicated by arrows. (Reproduced from Asta eva, I., X. Zhong, and F. A. Eisenberg. Maa >molecule 6 7339-7352. With permission from American Chemical Society.)... 

Complexants other than alcohols (e.g., amines, nitriles, tert-butyl compounds, surfactants, and multiple fluorophores) can also be detected by the method of Scheme 2 [279-284], Bohne and Yang have replaced alcohols with amino acids [285], although the zwitterionic charge distribution and increased steric requirements of the former lead to smaller stability constants of the ternary complex. Notwithstanding, tryptophan, leucine, and phenylalanine produce measurable changes in the I III ratio of pyrene emission, thereby allowing for their detection at mM levels. 

A Cu(II)-induced perturbation of pyrene fluorescence has been utilized to create a sensor for glutamate [388], A 2 2 1 Cu2+ 3-CD pyrene complex is formed by the noncovalent assembly of the constituents the site of Cu(II) binding is unknown. The pyrene emission resulting from complexation of the lu-mophore to 3-CD is effectively quenched by the addition of Cu(II). A 500-fold enhancement in pyrene intensity is observed upon the addition of 1.87 M glutamate, which is presumed to extract Cu(II) from the 2 2 1 complex. The precise nature of the quenching and restoration mechanisms is currently unknown. 

F ure 1.10. (A) Graphical representation of current interpretation for Metal-Enhanced P-type Fluorescence. (B) Experimental sample geometry. (C) Fluorescence emission spectra and photographs of pyrene emission from quartz (control sample) and SIFs. 

Pyrene has been used widely as a photophysical probe because of its long fluorescence lifetime and great tendency for excimer formation. Emission characteristics of pyrene molecules depend on the nature of the solvent. The ratio of relative intensities of the 1st (373 nm) and lllrd (383 nm) peaks, Ijjj/Ij, in a pyrene emission spectrum decreases as the polarity of the solvent increases. This... 

Fig. 86 Fluorescence spectra of a pyrene-implanted PBMA surface as a function of laser pulse number. Pyrene was transferred using ablation of a triazene polymer. Laser flu-ence 100 mj creT2, (a) 5 pulses, (b) 10 pulses, (c) 15 pulses, (d) 20 pulses. The vibrational pyrene emission peaks are denoted (I-V). Inset Normalized fluorescence intensity of the V pyrene peak at 393 nm vs laser pulse number. Data are taken from the spectra in the main figure. REPRINTED WITH PERMISSION OF [Ref. 360], COPYRIGHT (1998) Elsevier Science...

Table 5 Overall Quenching Rate Constants for Pyrene Emission in Sodium Taurocholate (NaTC) obtained in Time-Resolved Experiments... 

Figure 4.13 Plot of pyrene emission intensity as a function of temperature for aqueous solution of poly-(N-isopropylacrylamide) (PNIPAM) labelled with naphthalene(N)-donor and pyrene(Py)-acceptor PNIPAM-Py/366-N/50, 44 ppm in water. Wavelength excitation at 290 nm due to N excitation, at 328 nm due to...

Spectroscopy of the Polymers in Solution. The emissions of the pyrene and naphthalene groups attached to the polymers are sensitive to small changes in the chromophore separation distances. A short separation distance (ca 4 to 5 A) can be monitored with pyrene labeled polymers via changes in the features of the pyrene emission, and a longer scale (ca 15 to 50 A) by measuring the extent of non-radiative energy transfer between the two chromophores, either in solutions of the doubly-labeled copolymer or in mixed solutions of pyrene- and naphthalene-labeled materials. 

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