Facile synthesis of manganese dioxide nanocolloid and its application in oxidative decomposition of cysteine in absence and presence of non-ionic surfactant TX-100
Mohammad Altaf and Deogratius Jaganyi
School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa
Manganese dioxide nanocolloid has been synthesised by the chemical method in neutral medium without stabilizing agent at room temperature. The UV-vis spectrophotometer, Transmission electron microscopy (TEM), and Fourier transforms infrared (FT-IR) spectroscopy were used for characterization of the sample. Fourier transforms infrared spectroscopy (FTIR) spectra of pure MnO2 show the occurrence of O-Mn-O vibrational mode at around 600 and 475 cm-1. The chemical composition was obtained by EDX analysis and confirmed the presence of Mn and O in the sample. The kinetics of the oxidation of cysteine has also been investigated both in aqueous as well as micellar media at 35°C. The first- and fractional-order-rate is observed with respect to [MnO2] and [Cyst] in both media. The non-ionic surfactant TX-100 has catalytic effect on the rate of the oxidation of cysteine. The use of surfactant micelles is highlighted as, in favorable cases; the micelles help the redox reactions by bringing the reactants in a close proximity due to hydrogen bonding. A possible mechanism involving association/binding between the reactant and the surfactant micelle has been proposed.
Keywords: nanocolloid, manganese dioxide, kinetics, cysteine, TX-100