Structural studies on colloidal tetraalkylammonium manganese oxides

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