The nonlinear optical absorption, scattering and optical limiting properties of CdS nanoparticles dispersed in dimethylformamide (DMF) are investigated. The nanoparticles are synthesized using the standard chemical synthesis method with thioglycerol as the capping agent. The investigations are carried out at 532 nm in the ns regime. Strong two-photon absorption and nonlinear scattering are found to be responsible for good optical limiting characteristics in these nanoparticles.

Iron, cobalt and molybdenum compounds are extensively used for the conversion of coal to liquid fuels. To examine the correlations between catalytic, magnetic, and spectroscopic properties, we investigated the Zero-field Nuclear Magnetic Resonance spectra of cobalt, Mossbauer spectra of iron, FTIR spectra and magnetic character of the composite for a series of Fe/MoO 3 and Fe/Co/MoO 3 catalysts with different inter-metallic ratios and metal loadings. All the precursors are paramagnetic according to the magnetization data. Mossbauer results show that in the precursors Fe is in Fe 3+ state. FTIR spectra reveal bands due to monodentate and bidentate structures of Fe-MoO 3 and Co-MoO 3 . NMR spectra support these findings indicating strong inter-metallic interaction between Co and MoO 3 . FTIR results show that exposure to CO or syngas (CO+H 2 ), leads to dissociation of metal-MoO 3 structures and Mossbauer data shows the presence of excess lattice charge with iron in the Fe 2+ state. Only a minute portion of the composite gets reduced to metallic state. Cobalt seems to form cobalt carbonyl structures, while carbide formations seem to occur with iron. Lack of free metal sites seems to be the reason for the poor conversion of CO observed in the catalytic runs.

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