Function of dye concentration

Quantum yields are a function of solvent, and are also likely a function of dye concentration. 

Laser flash photolysis has been performed with the halogenated derivatives in ethanol [374], Measurements of the triplet lifetimes as a function of dye concentration, laser power, and in the presence of electron donors allowed us to determine the rate constants collected in Table 17. 

The subscript s refers to the values of the pure solvent and fs = P ps / Ms. d ldxD and dn2 Id Xp were determined by linear regression of and n2 as a function of dye concentration for typically five different solutions of mol fraction less than 10 3. In all cases, the linear approximation was fully justified within the experimental error. Figure 5 shows, as an example, as a function of concentration for X in chloroform. For molecules with large dipole moments, like the ones discussed in this paper, the contribution of dp IdXp can be neglected since even the extreme assumption of dp Id Xp =1 g/cm3 changes the value of iD by only 0.4%. Similarly, the term proportional to dn2 Idxp contributes less than 4% to the... 

In addition to proflavin and rhodamine, the photobleaching-resistant Cy3 and Cy5 fluorophores are also frequently used in single-molecule experiments and have been incorporated in the form of hydrazide derivatives into tRNAs via D residues (Pan et al., 2009) (Fig. 4.2). However, quantitative uptake of these hydrazide dyes requires modification of three reaction parameters higher concentrations of the hydrazide dyes (40 mM) than that required for proflavin or rhodamine (22 mM), pH 3.7 rather than pH 3.0, and 2 h reaction time instead of 45—90 min. The requirement of higher concentration is to promote formation of hydrazide adduct, while the slighdy elevated pH prevents hydrolysis of the adduct, which is acid labile. Thus, while the labeling method can be adapted to incorporate new fluorophores besides proflavin and rhodamine, it is prudent to systematically evaluate for the fluorophores under consideration for coupling efficiency as a function of dye concentration, pH, and reaction time. 

Garof et found similar results for R6G on silver films. They study the optical density of the dye-coated films as a function of dye concentration (in the solution from which it is adsorbed on the silver) and as a function of film thickness. The double peaks appeared and were explained on the basis of Mie formalism. Note that significant changes in the spectrum shape appear only from a concentration of 2.8 x M. Also no determination of the amount... 

The function of sodium chloride as the aqueous supporting electrolyte is physiologically relevant to the experiment. Figure 4 shows the variation of interfacial potential as a function of dye concentration at selected concentrations of sodium chloride. The value 0.12 mol/L (7-g/L NaCl) corresponds to a physiological concentration. 

Figure 4. Calculated interfacial potential as a function of dye concentration for a system that contains aqueous sodium chloride in concentrations ranging from 0 to 1 mol/L as indicated at the curves. 0.12 mol/L is a physiological saline solution (7 g/L NaCl). The dye DiOC2(3)1 was dissolved in the nitrobenzene...

Fig. si. Atomic ratio N/Si for sulforhodamine 101 (full symbols) and rhodamine 6G (open symbols) adsorbed on 25 or 150 A pore silicas as a function of dye concentration. Straight lines in the plot represent average values. 

Fig. 2. Comparison of the induction of DNA strand-breaks (including those arising from alkali-labile lesions) in HT29 cells as a function of dye concentration (1 h exposure) or X-ray dose (irradiated monolayer cultures). Symbols O X-ray data (n = 3) Ho33342 data (n = 2-7). Data points represent arithmetic means (SE < 15%) for the number (n) of determinations indicated above in parentheses. (Data from [17] by permission of Taylor Francis Ltd.)...

Photoluminescence emission spectra (left) of freshly prepared blend films of LLDPE and BCMB as a function of dye concentration (given in % w/w), and image (right) of a blend film of LLDPE and 0.20% w/w BCMB stretched at room temperature to a draw ratio of 500% (irradiated with UV light of A = 365 nm). All spectra were normalised to the intensity of the monomer peak. 

The measured quadratic E-0 coefficient as a function of dye concentration is shown in Figure 8. An approximately linear relationship exists between them, which indicates no aggregation in this dye doped polymer system. The quadratic E-0 coefficients in this system are large compared with those of our former systems based on azomethine dyes and those reported recently by Kuzyk et al at the same dye concentrations. 

Dye molecules have been shown to greatly increase the photon output of OLEDs, as shown in Figure 9.18. Flowever, there is a strong peak in the luminescence as a function of dye concentration. At very low concentrations a minority carrier may not... 

Fig. 3 Intensity sensing (a) and this sensing with the reference dye (b). The fluorescence intensity with the band maximum at decreases as a function of analyte concentration. The reference dye allows providing the ratio of two intensities detected at wavelengths ki and X2...

Imagine that a reactor is operating in the steady state with a constant throughflow, Q, of 3.7 dm min. At the reactor inlet, 50 g of concentrated dye are instantaneously injected. The outlet concentration of this tracer is detected and recorded as a function of time. Steady-state calibrations of the dye-detecting system show that its sensitivity is essentially constant and equal to 3.88 mV (g dye dm over the range of dye concentrations encountered. The data in Table 1 is collected. 

It remains to be determined to what extent the dye adsorption technique is applicable to other substrates. No evidence was obtained for Pseudocyanine adsorption to Mn02, Fe2Os or to pure silver surfaces, although this dye can be bound to mica, lead halides, and mercury salts with formation of a /-band (61). Not only cyanines but other dye classes can yield surface spectra which may be similarly analyzed. This is specifically the case with the phthalein and azine dyes which were recommended by Fajans and by Kolthoff as adsorption indicators in potentio-metric titrations (15, 30). The techniques described are also convenient for determining rates and heats of adsorption and surface concentrations of dyes they have already found application in studies of luminescence (18) and electrophoresis (68) of silver halides as a function of dye coverage. 

Fig. 9 QxQy chromaticity coordinate of the optode sensors with and without the screening dye as a function of Li+ concentration...

Critical micelle concentrations can be determined by measuring any micelle-influenced physical property as a function of surfactant concentration. In practice, surface tension, electrical conductivity and dye solubilisation measurements (see Figure 4.13 and page 90) are the most popular. The choice of physical property will slightly influence the measured c.m.c., as will the procedure adopted to determine the point of discontinuity. 

FIGURE 3.26 Three-dimensional plot of fluorescence intensity of carboxyfluorescein dye molecules in aqueous solution as a function of their concentration (0.00715—0.266 pM) and temperature (28-74°C). The plot was mapped over 110 data points (excluded for clarity) gained from 11 temperature measurements across 10 microchannels [447]. Reprinted with permission from the American Chemical Society. 

In the vast majority of cases reported where a streak camera has been used to measure fluorescence lifetimes, the measurements have been made from a single laser shot. Since a high fluorescence efficiency is necessary for single shot experiments, most of these studies have been concerned with measuring the lifetimes and quenching of organic dye molecules in solution. For example, Yu etal. [67] have made a study of the fluorescence lifetime of malachite green as a function of solvent viscosity and the lifetime and relative yield of erythrosin as a function of water concentration in a water—acetone mixture. The fluorescence lifetimes of these dyes are... 

The experiments reported here were formulated with the intention of uncovering, in as much detail as possible, the environment existing within a cellulosic fiber in contact with an ionic aqueous phase. Measurements were made at room temperature ( 25°C) and at 90°C. The salt used most extensively was NaaS04 and measurements were made on the uptake of both cation and anion as a function of the concentration of the bath at 25°C and 90°C and as a function of pH at 25°C. In addition, the uptake of the direct dye, Chrysophenine G, and the effect of the dye on the salt uptake were studied at 90°C. It was also necessary to perform some measurements relating to the stability of the fibers. Finally, some measurements were made on the uptake of the Br ion from NaBr solutions. 

Table VII. The Uptake of Chrysophenine G by Viscose at 90°C as a Function of Dye and Salt Concentration...

The plots of calculated interfacial potential as a function of DiOC 3) concentration are shown in Figure 7 together with the experimental results for DiOC 3) and DiOC2(5). In the range of dye concentration from 10 2 to 10 6 mol/L, the measured values agree with those predicted through calculations. 

Fc is the fluorescence of the dye in a lipid vesicle suspension with a lipid concentration of C F0 and Fx are the limiting dye fluorescence readings in the absence of lipid and at very high lipid concentrations, respectively. The fluorescence as a function of lipid concentration is fitted to this equation via nonlinear regression. The results of such measurements for a series of styryl dyes (10), as well as the spectral characteristics of the dyes in several solvents, are given in Table I. As expected, the membrane affinity of the dyes increases with the length of the chromophore or the number of carbons in the appended hydrocarbon chains. Also noteworthy is the striking increase in fluorescence quantum yield for the membrane-bound dyes this is probably due to the well-ordered immobile environment of the membrane, which inhibits nonradiative decay processes that require molecular motion in the excited state. 

Reaction of Stable Solvated Electrons with Water. One of the most promising ways of generating a homogeneous solution of hydrated electrons has been pursued by Dewald, Dye, Eigen, and DeMaeyer (26), who mixed a solution of electrons solvated in ethylenediamine with water. These authors took a solution of Cs in ethylenediamine, a solvent in which solvated electrons are stable, and combined it in a fast-flow mixing cell with a solution of water in ethylenediamine. They then followed the rate of decay of the near infrared absorption band of e ed as a function of water concentration. More recently other active metals have been used and the kinetics fully analyzed (32). The second-order rate constant (20M 1 sec. 1) obtained is attributed to Reaction 16 and compared with... 

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