Gamal A.-W. Ahmed

Further evidence for detection of short-lived transient hypomanganate(V) and manganate(VI) intermediates during oxidation of some sulfated polysaccharides by alkaline permanganate using conventional spectrophotometric techniques.

Spectrophotometric evidence for the formation of hypomanganate(V), [CAR-Mn(V)O43-], and manganate(VI), [CAR-Mn(VI)O42-], intermediate complexes has been confirmed during the oxidation of iota- and lambda-carrageenan-sulfated polysaccharides (CAR) by alkaline permanganate at pHs 12 using a conventional spectrophotometer. These short-lived intermediate complexes were identified and characterized. A reaction mechanism in good consistence with the experimental results is suggested.

Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan polysaccharides as sulfated carbohydrates in acid perchlorate solutions.

The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm(-3) have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that Mn(III) is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed.

Effect of surfactant-free addition and γ-irradiation on the synthesis of CdO quantum dots by thermal decomposition of γ-irradiated anhydrous cadmium acetate†

Abstract Pure phase of cubic (FCC) CdO quantum dots were successfully synthesized by thermal oxidation of γ-irradiated anhydrous cadmium acetate at 400°C for three hours in the presence and absence of benzyl alcohol as surfactant-free. Morphological and structural characteristic of the as-synthesized quantum dots were performed with X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). SEM image of CdO quantum dots synthesized using γ-irradiated anhydrous cadmium acetate with 102 kGy absorbed dose shows the formation of the mesoporous nanostructure. In the presence of benzyl alcohol surfactant, the calcination process afforded cauliflower-like structure. TEM image of CdO quantum dots synthesized using γ-irradiated anhydrous cadmium acetate in presence of benzyl alcohol surfactant shows formation of nanoribbon of CdO quantum dots.