The aggregation and the micropolarity of Aerosol-OT reverse micelles in benzene are investigated by using a new absorption probe, l-methyl-8-oxyquinolinium betaine (QB) at 25 °C, as a function of the surfactant concentration and the water content of the solutions. QB is preferentially partitioned (>500:1) in the aqueous pool of the aggregates, and its transition energy £qB is shown to have a linear relationship with Kosower's Z values and Dimroth et al. 's ET(30) values.

Langmuir 1988,4,653-655 653 Fe/MgO or Fe/A1203. The results of both studies suggest that one way silica and titania can interact with supported iron is through the stabilization of iron in low-coordination sites.The low-coordination sites in the ferrisilicates of this study were found to be unstable with respect to repeated oxidation-reduction cycles. Such cycles converted the low-coordination iron in the sample with an iron loading of 3.60% to high-coordination iron. Although the same behavior was not observed for the sample with the higher iron loading, most of the iron in that sample was already in sites of high coordination after the first reduction. Corresponding experiments have not yet been tried for Fe/SiOz. Nevertheless, it can be seen from the M h b a u e r spectroscopy spectral areas in Table IV that the ferrisilicate sample with an iron loading of 3.60% had approximately half of its iron in low-coordination sites after the first reduction. The iron loading of this sample was approximately 7 times the loading at which a similar amount of inner doublet was observed for Fe/SiOa6 Hence, ferrisilicates synthesized as described above provide the opportunity to study and utilize low-coordination iron in samples with relatively high loadings. This may make these materials useful for catalytic reactions where iron cations function as Lewis acid or redox centers.The NO adsorption experiments done on the sample with a loading of 5.41% showed that iron in the high-coordination sites of the ferrisilicates has only a limited accessibility to gas-phase molecules like NO. However, low-coordination iron in Fe/Si02 and iron-exchanged zeolites has been shown before to readily adsorb NO?J'*9J0 In addition, low-coordination iron in the 3.60% ferrisilicate described above was found to act as a strong adsorption center for pyridine. Therefore, while the ferrisilicate sample with the lower loading (3.60%) has iron in sites that are accessible to the gas phase, the 5.41 w t % sample appears to be a less promising catalytic material.The two samples with the higher iron loadings were found to exhibit doublets with a low IS after treatment with Oa Ferric doublets of low IS are indicative of iron that is covalently bonded.20 Hence, it was found that the higher the silica content the more ionic were the Fe-0 bonds. This suggests that another way silica can interact with iron cations is by making the bonding of iron with oxygen more ionic. This may be one reason why silicasupported metal cations display interesting acidic properties at low cation loadings.6*20Acknowledgment. We express gratitude to the National Science Foundation for Grant CBT-8414622, which supported this work. In addition, we gratefully acknowledge funding from the Chinese government that allowed Z.Y. to be a visiting scholar at the University of Wisconsin.Registry No. Fe, 7439-89-6; SOz, 7631-86-9; iron silicate, 12673-39-1.The mean aggregation number it and water vapor pressure pw of 0.1 M Aerosol-OT reverse micelles were determined by controlled partial ...

We have investigated the rate of catalytic hydrolysis of cellulose fabrics by a cellulase enzyme in the presence of dyes on a cotton substrate. We found that both direct and reactive dyes on the substrate apparently inhibited the enzyme catalytic reaction, whereas a vat dye did not. The enzyme was more active for mercerized than for nonmercerized cotton. The enzyme treatment significantly reduced both tear strength and dye uptake of the fabrics. Enzyme-treated and successively dyed fabrics showed different color fading profiles compared to untreated fabrics after laundering.

No abstract

No abstract