Structural studies on colloidal tetraalkylammonium manganese oxides

Abstract

XAFS at the Mn K edge was employed to elucidate the structure of colloidal tetraalkylammonium (TAA) manganese oxides in sols and gels obtained by different preparation and heat treatment procedures. XANES analysis revealed an average valence of ∼ 3.7 for as-synthesized TAA colloids, whereas gelled TAA colloids showed a decreased average valence of ∼ 3.5. XAFS analysis was carried out to distances of ∼ 6.0 Å around the central Mn atom employing theoretical backscattering phases and amplitudes calculated with the abinitio code FEFF. A Birnessite layer MnOx model structure was used which resulted in a good agreement with experimental data.