Artículos SCI

The degree of aggregation and/or coalescence of Au-citrate nanoparticles (AuNPs, mean size 21.5 ± 2.9 nm), after delivery in simulated seawater, are shown to be concentration-dependent. At low concentrations no coalescence and only limited aggregation of primary particles were found. Experiments were performed in which the marine bivalve (Ruditapes philippinarum) was exposed to AuNPs or dissolved Au and subsequently, bivalve tissues were studied by Scanning and Transmission Electron Microscopy and chemical analyses. We show that the bivalve accumulates gold in both cases within either the digestive gland or gill tissues, in different concentrations (including values of predicted environmental relevance). After 28 days of exposure, electron-dense deposits (corresponding to AuNPs, as proven by X-ray microanalysis) were observed in the heterolysosomes of the digestive gland cells. Although non-measurable solubility of AuNPs in seawater was found, evidence is presented of the toxicity produced by Au3+ dissolved species (chloroauric acid solutions) and its relevance is discussed.

In this work the development of a series of gold catalysts, essentially based on γ-alumina promoted with a small superficial fraction of Ce–Fe mixed oxides, is reported. The catalytic behaviour is evaluated in the water gas shift reaction. The formation of a Ce–Fe solid solution is evidenced by XRD and related to the catalytic activity where the importance of the Ce–Fe interaction is demonstrated. The best catalyst reached CO conversions very close to the equilibrium limit. A long-term stability test is performed and the loss of activity is observed and attributed to reaction intermediates. Almost complete recovery of the initial conversion is achieved after oxidation treatment, suggesting that the problem of stability could be overcome by a suitable change in the reaction parameters thus leading to a highly efficient catalyst for future applications in H2 production and clean-up.