1-Pyrene carboxaldehyde systems

Pyrene Carboxaldehyde Probe Studies. Fluorescence spectra of 1-pyrene carboxaldehyde in nonane solutions of sulfonates A and B and In an octane solution of Aerosol OT are compared to the probe spectra in pure hydrocarbon media in Figure 1. Parts (a) and (b) are of sulfonates A and B systems, respectively part (c) is of aerosol OT system. They were constructed at different gain settings and therefore the intensities shown for the individual system are not directly comparable. The fluorescence intensity of 1-pyrene carboxaldehyde in nonane alone is much weaker than in either the sulfonate A or sulfonate B solution. Aerosol OT containing solubilized H.O does not enhance the fluorescence intensity of 1-pyrene carboxardehyde as much as sulfonates A and B, but the band maximum is shifted as expected for this probe in a water-rich medium. 

We measured the time-dependent anisotropy of 1-pyrene carboxaldehyde in sulfonate A and B systems. The results are shown in Figure 2. Relaxation times determined from the unconvoluted anisotropy decays for sulfonates A and B in heptane solution were found to be 7 ns and 28 ns, respectively. 

In order to test further the applicability of 1-pyrene carboxaldehyde as a fluorescent probe, we applied Keh and Valeur s method (4) to determine average micellar sizes of sulfonate A and B micelles. This method is based on the assumption that the motion of a probe molecule is coupled to that of the micelle, and that the micellar hydrodynamic volumes are the same in two apolar solvents of different viscosities. For our purposes, time averaged anisotropies of these systems were measured in two n-alkanes hexane and nonane. The fluorescence lifetime of 1-pyrene carboxaldehyde with the two sulfonates in both these solvents was found to be approximately 5 ns. The micellar sizes (diameter) calculated for sulfonates A and B were 53 5A and 82 lOA, respectively. Since these micelles possesed solid polar cores, they were probably more tightly bound than typical inverted micelles such as those of aerosol OT. Hence, it was expected that the probe molecules would not perturb the micelles to an extent which would substantially affect the micellar sizes measured. 

Pyrene Carboxaldehyde in Calcium Alkarylsulfonates. Our work shows that 1-pyrene carboxaldehyde as a fluorescent probe for the sulfonate systems behaves very much the same as rhodamine B (1 ) and anillnonaphthalene sulfonate (2), whose fluorescence intensities in hydrocarbon media are enhanced in the presence of inverted micelles. However, the intensity Increase observed with AOT was considerably less than that observed with the sulfonates. It is speculated that... 

The internal rotational relaxation times of 1-pyrene carboxaldehyde in sulfonate systems may offer some indication of the extent of probe binding to the inverted micelle. In the absence of any background fluorescence interference to the time-dependent anisotropy decay profile, the internal rotational relaxation time should correlate with the strength of binding with the polar material in the polar core. However, spectral interference from the aromatic moieties of sulfonates is substantial, so that the values of internal rotational relaxation time can only be used for qualitative comparison. 

Pyrene carboxaldehyde has utility as a fluorescent probe in some Inverted micellar systems containing solubilized Inorganic species in the polar core. Its fluorescence lifetime is ca. 5 ns thus it is an appropriate probe for measuring micellar sizes which are approximately lOOA. 

Carbofinan. atrazine, metolachlor, and their byproducts were separated on HPTLC plates containing fluorescent indicator. Several single and dual solvent systems were investigated for resolution by one-dimensional development. The quantification of the compounds was carried out by densitometric scanning. 1-pyrene carboxaldehyde detected chlorpyrifos and its byproducts with a sensitivity of 0.5-0.05 pg, but dansyl chloride, NBD-Cl, DPH, and Rhodamine 6G were also investigated and compared to fluorescence quench detection (131b) (Table 10). 

The quantum yield is an indicator of how efficient a particular process is. However, some care must be taken in comparing quantum yields for different systems, because the quantum yield is always measured relative to other processes in the molecule. For example, pyrene derivative. The reason this is not reflected in the quantum yields is that we must also consider competing processes. The ISC rate for pyrene-3-carboxaldehyde is also much faster than that for benzene due to the ability to access a ( ,tt ) state that is not available for benzene. This competing ISC process limits the amount of fluorescence, and by coincidence the two compounds end up with the same fluorescence quantum yield. Thus, while the quantum yield tells you about the efficiency of a process for a given molecule, it alone cannot tell you why the process is or is not efficient. 

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