Ionic liquid assisted Synthesis and Characterization of metallic Molybdenum and Molybdenum oxide nanoparticles
Nanostructured Mo and MoO3 colloidal dispersions have been obtained reproducibly through reduction of ammonium molybdate by sodium borohydride in ionic liquids. When (NH4)6Mo7O24.4H2O is reduced by NaBH4 in both 1-ethyl-3-methyl imidazolium dicyanamide and 1-butyl-3- methylimidazoliumdicyanamide at 180oC, nanostructured MoO3 formed as the major phase. The XRD pattern confirmed the crystalline nature of the material. The most representative reflections of MoO3 (JCPDS: 47-1081) were indexed in monoclinic crystal system (space group P2 1/c (14) Y-unique) . The average mean diameter of 53.8nm was calculated using Debye-Scherrer equation from full width at halfmaximum (FWHM) of (111), (-311), (160), (-421), (330) and (413) planes for material in IL EmimN(CN)2. But in BmimN(CN)2 the diameter was estimated to be 40.8nm. When the reduction was carried out in EmimOTf and BmimOTf, the products consists of metallic molybdenum and MoO3. The crystalline phase of MoO3 is rodlike and is determined to be orthorhombic, space group Pbnm(62) with the cell dimensions [a=3.963, b=13.856, c=3.696 Ǻ.; Vol.=203. Ǻ3, Z=4, ρ=4.7096gcm-1] corresponding to MoO3 (JCPDS: (35-0609). The average diameter of 51.0 and 48.9nm was calculated respectively for particles in IL EmimOTf. UV-Visible absorption spectra of the fraction in ionic liquid dispersed in ethanol .shows that the predominant feature in the spectra is the spin-allowed ligand-to-metal charge transfer (LMCT) from O2- ion tiu orbital to a d0 eg orbital, which is observed in the range 200-300nm centred at 212nm in the UV region. This strongly indicates the presence of metallic Molybdenum with particle size less than 100nm.
