Mossbauer evidence for fast electron hopping between Fe(II) and Fe(III) iniron hydroxide/molybdenum disulfide lamellar nanocomposite

Nanocomposite compounds with iron hydroxide and molybdenum disulfide altern ating layers have been studied using Fe-57 Mossbauer spectroscopy. Evidence is given of the presence of two oxidation states for iron (Fe(II)/Fe(III)a pproximate to 1.9). In the temperature range 60-160 K thermal evolution of the absorption areas obeys Debye's model, with the lattice temperature Thet a(M) equal to 275 and 320 K for Fe(II) and Fe(III) respectively. At higher temperature (T greater than or equal to 180 K), a new iron state is observe d, which can be related to fast electron hopping between certain heterovale nt iron ions. Tin-doping enhances this process which can already be detecte d at 140 K. (C) 2000 Elsevier Science BN. AU rights reserved.