Disperse dyes marking results

Differences in geometry and polarity of the dye molecules can lead to wide variations in these finishing or dye-specific properties and can have a marked effect on the absorption characteristics of all dyes, irrespective of whether singlecomponent or combination dyeing processes are used. For instance, uneven dyeing may occur when an unequal distribution of particle size results in insufficient dispersion stability and hence crystal growth and precipitation at the substrate surface. 

For example, simple fluorescence intensity measurements on dispersed hydrocarbon probes such as anthracene [17], perylene [18], pyrene [6,17,22], 9,10-dimethylanthracene (DMA) [60], and coumarin dyes [62] have confirmed that PMAA displays pH-dependent solution behavior. A marked decrease in the intensity of the probe occurs between pH 5 and 6, which coincides with the conformational transition of PMAA as determined by classical methods [2-4,47-50]. Two interrelated effects account for this behavior the solubilizing capacity of the polymer promotes an increase in the concentration of the probe in the solution [6,17,18,60,62] and because the intensity of the fluorescence observed is proportional to the excited state population the resulting emission is enhanced. The hydrocarbons may also be considered to be preferentially solubilized within the hydrophobic domains or structures of the hypercoiled state [6,22]. This results in a degree of protection from the deactivating effects of the aqueous phase and a concomitant increase in the fluorescence observed [6,17,18,22,60,62]. 

Water-soluble probes have also been reported to undergo marked changes in their fluorescence characteristics when dispersed in polyelectrolyte solutions [18,52,61,72-78]. For example, the cationic dye, auramine O (AuO) is virtually nonfluorescent in aqueous solution but an increase in intensity is observed in the presence of PMAA at low pH as a result of enhanced binding in the hypercoiled state [72,73,75,78]. On neutralization, the fluorescence from AuO decreases as the compact structure breaks down forming the expanded state and the probe is released to the aqueous phase [52]. In a recent extension of this theme, the sensitivity of the emission spectrum of AuO to the environment in which it resides has been further exploited by covalently bonding the dye to PMAA [61]. Figure 2.1 shows the... 

Stable activable tracers are powerful tools for the study of many environmental problems. Compared with fluorescent dyes or radiotracers, they offer many advantages that are reviewed herein. Our research group has emphasized the use of rare earth nuclides with short-lived activation products as stable activable tracers. Use of rare earth nuclides is cost-competitive with conventional tracers and allows rare earth "fingerprints to mark individual sources with subsequent simultaneous tracing of effluents from several sources. We present results from the application of these tracers to monitor pollutant dispersal from multiple industrial stacks, monitor fluid-bound pollutant dispersal in estuarine and fresh-water systems, monitor herbicide dispersal, and trace toxic organic chemicals in the marine environment. 

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