首页|XPS studies of freshly prepared rhenium nanoparticle dispersions from hydrazinium hydrate and borohydride reduction of hexacholororhenate solutions
XPS studies of freshly prepared rhenium nanoparticle dispersions from hydrazinium hydrate and borohydride reduction of hexacholororhenate solutions
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With an increase in the incorporation of colloidal or nano-sized rhenium particles into advanced materials such as catalysts [1], an intimate knowledge of the surface properties of rhenium in this state is vital. Earlier reports [2-4] have attempted to characterize the colloidal rhenium products obtained from reduction of perrhenate but only led to unproven inferences as to which oxidation states were present in the samples. In general, there is a surprising lack of such fundamental studies in the materials science or chemical literature. X-ray photoelectron spectrometry (XPS) is an authoritative technique for studying the surface speciation of colloidal materials ex situ [6, 7]. Our earlier XPS studies [5] conducted on colloidally unstable rhenium colloids generated from the hydrazinium hydrate reduction of hexachlororhenate (IV) ion showed that colloids prepared 1-2 days before XPS analysis had already undergone extensive oxidation to states even beyond the starting Re(IV) salt (i. e., to Re(VI) or Re(VII) by the time analysis was performed so that the initial oxidation state of the just prepared rhenium colloids was still uncertain. The current report aims to present and interpret XPS data of not only freshly prepared hydrazinium hydrate-generated rhenium colloids but also of the hitherto unstudied borohydride-generated rhenium colloid systems in order to deduce the initial oxidation states of the colloidal rhenium. The choice of hexacholorhenate (IV) as a starting reagent was made because there is an almost complete lack of data on the characterization of colloidal products from this compound.
K. M. Babu、M. R. Mucalo
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Chemistry Department, University of Waikato, Private Bag 3105, Hamilton, New Zealand
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