Fluorescence spectral profiles

Figure 11,3 Representative absorption (—) and emission (—) fluorescent spectral profiles.

In order to discuss any modification to the fluorescence spectral profile, it is important to first understand its origin for a free fluorophore. The model of fluorescence that we discuss below has been simplified as much as possible and retains only the features that are necessary for the generalization to the MEF... 

Another complementary approach to that presented so far is to study different fluorophores (with different free-space fluorescence spectral profiles) on the same NP arrays. This is illustrated in Fig. 2.7. Four fluorophores are used there Methylene Blue (MB) as before, Rhodamine 6G (Rh6G), Rhodamine B (RhB), and Crystal Violet (CV). All experiments are carried out at 633 nm excitation again, and the corresponding free-space fluorescence spectra are shown in Fig. 2.7(a). Rh6G, RhB, and CV all exhibit a tail-like fluorescence spectrum, very similar to each other. This simply reflects the fact that the excitation (at 633 nm) is close or below (in energy) the main absorption band. In this case, internal relaxation in S is expected to play a negligible role, even... 

Fullerene-styrene copolymers have been prepared in radical initiated and thermal polymerization reactions [148-151]. In radical copolymerizations of Cgg and styrene, copolymers with Cgg contents up to 50% (wt/wt) can be obtained [150]. Electronic absorption spectra of the copolymers are very different from that of monomeric C o (Fig. 36). The absorptivities per unit weight concentration of the copolymers j increase with increasing C q contents in the copolymers in a nearly linear relationship (Fig. 37). Fluorescence spectra of the Cgg-styrene copolymers, blue-shifted from the spectrum of monomeric Cgo, are dependent on excitation wavelengths in a systematic fashion [149]. Interestingly, the observed absorption and fluorescence spectral profiles of CgQ-styrene and Cyg-styrene copolymers are very similar, even though the spectra of monomeric CgQ and C70 are very different. The absorption and fluorescence spectra of the fullerene-styrene copolymers are also similar to those of the pendant Cgg-poly-styrene polymer (19) prepared in a Friedel-Crafts type reaction [150,156]. 

The ZnTPP chromophores encapsulated in the La microdomain also show phosphorescence and delayed fluorescence in aqueous solutions at ordinary temperatures, although the intensities are much less than those in the Cd microdomain. The phosphorescence and fluorescence spectral profiles for the ZnTPP in the Cd domain are greatly distorted when compared with those in the La domain. In the Cd domain, the phosphorescence peak is blue-... 

Kato, N., Pontier, D. and Lam, E. (2002). Spectral profiling for the simultaneous observation of four distinct fluorescent proteins and detection of protein-protein interaction via fluorescence resonance energy transfer in tobacco leaf nuclei. Plant Physiol. 129, 931-42. 

Gaussian Laser Profile-Voigt Atom Profile. This case turns out to be a better approximation of our experimental situation, i.e., the laser FWHM is fairly broad compared to the absorption line width and the absorption profile of atoms in an atmospheric combustion flame is described by a Voigt profile. Here the laser is assumed to have a Gaussian spectral profile as well as a Gaussian atomic absorption profile. In this case, convolution of two Gaussian functions is still a Gaussian function. Evaluation of the ratio n2/nT, and the fluorescence radiance. Bp, allows determination of the half width of the fluorescence excitation profile, 6X... 

However, three-way data can also be formed with two object ways and one variable way and by one sample with three variable ways. Environmental data where several distinct locations are monitored at discrete time intervals for multiple analytes exemplifies three-way data with two object ways and one variable way. Excitation-emission-time decay fluorescence or gas chromatography with a tandem mass spectroscopic detector are instrumental methods that form three-way data with three variable ways. These data types are employed mostly for qualitative application. Herein, the desire of the analyst to elicit underlying factors that influence the ecosystem or to deconvolve highly overlapped spectral profiles to deduce the number, identity, or relaxation coefficients of constituents in a complex sample can be realized. The same procedures employed for quantitation lend themselves to the extraction of qualitative information. 

Spectral Profile Modifications In Metal-Enhanced Fluorescence... 

This chapter is organized as follows. In Sec. 2.2, we review some basic aspects of the fi-ee-space fluorescence process and of its modification close to metal surfaces (MEF). These concepts are then extended in Sec. 2.3 to discuss the various mechanisms of spectral profile modification that can be expected in MEF conditions. Experimental demonstration of some of these concepts is... 

The signal (e.g. fluorescence) intensities will be characterized by their powers P [W]. The spectral profile is characterized by the spectral density (o) [rad ]. By definition, the number of photons per unit time at a frequency between 0) and CO+dCO is n(0))d0). 

Spectral Profile Of Fluorescence. Free-space Case... 

In most fluorescence models where the spectral profile is ignored, the emitted fluorescence power is then simply given as This... 

The spectral profile of fluorescence is therefore entirely determined (phenomenologically) by the -dependence of This is linked,... 

The EM theory of Metal Enhanced Fluorescence (MEF) was studied and developed extensively in the 70-80 s [2,3,4,5,6], All the EM mechanims involved in MEF can be understood within classical EM theory [3,4,5,6] as confirmed in the simplest cases by quantum studies [2,12,17,18], In most of these models, the emitter is depicted as a simple two- (or three-) level system, i.e. only one emission wavelength is considered. This is appropriate in general to understand modifications of absorption or emission rates, but it entirely ignores the spectral profile of the fluorescence emission. We will first review... 

Let us summarize the predictions of these simple models in terms of the spectral profile (0) -dependence) of the fluorescence ... 

The most direct approach to study the SPMs in MEF conditions is to measure the spectral profile of fluorescence under MEF conditions lijDDg ) and... 

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