Abstract
A sodium dodecyl sulphate (SDS)-assisted approach was used for the synthesis of alpha-MnO2 nanorods by aerial oxidation of MnCl2 in the presence of NaOH. The mixing order of reactants (Mn2+ + OH-, Mn2+ + SDS, Mn2+ - OH- + SDS and Mn2+ -SDS + OH-), their molar ratios and pH have significant impacts on the pseudo-first-order kinetics of the redox system. Use of SDS decreases the Mn2+ reduction potential and avoids the formation of Mn(OH)(2) as an intermediate in alkaline medium. alpha-MnO2 nanorods were further used in the preparation of Ag@MnO2 nanocomposites by a wet chemical method. The morphologies of alpha-MnO2 and Ag-doped MnO2 were determined by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), X-ray diffraction (XRD) and dynamic light scattering (DLS) measurements, which show that the alpha-MnO2 nanorods are successfully converted into Ag-doped MnO2. The complex formation constant, K-c = 26 mol(-1) dm(3), and difference in absorption, Delta epsilon = 5.5 mol(-1) dm(3) cm(-1), were calculated. The optical band gap energy was calculated and found to be 2.4 and 2.0 eV for MnO2 and Ag@MnO2, respectively. (C) 2018 Elsevier B.V. All rights reserved.