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In this work we report a detailed X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) study of poly(ethylene glycol) PEG-like chemical gradients deposited via plasma enhanced chemical vapour deposition (PECVD) at two different load powers using diethylene glycol dimethyl ether (DG) as a monomer. Principal component analysis (PCA) was applied to the ToF-SIMS data both before and after protein adsorption on the plasma polymer thin films. Results of the PCA loadings indicated a higher content of hydrocarbon fragments across the higher load power gradient, which adsorbed higher amounts of proteins. Gradients deposited at a lower load power retained a higher degree of monomer like functionality as did the central region directly underneath the knife edge electrode. Analysis of the adsorption of serum proteins (human serum albumin and fetal bovine serum) was monitored across the gradient films and increased with decreasing ether (PEG-like) film chemistries. The effect of protein incubation time on the levels adsorbed fetal bovine serum on the plasma polymer films was critical, with significantly more protein adsorbing after 24 hour incubation times on both gradient films. The attachment of HeLa cells on the gradients appeared to be dictated not only by the surface chemistry, but also by the adsorption of serum proteins. XPS analysis revealed that at surface ether concentrations of less than 70% in the gradient films, significant increases in protein and cell attachment were observed. Refereed/Peer-reviewed

Rare earth (RE) promoted cobalt-silica gel catalysts for Fischer-Tropsch (F-T) synthesis were investigated systematically by various analytical techniques. The addition of small amounts of praseodymium to cobalt-silica gel catalysts greatly enhances their activity and selectivity in the F-T synthesis. The optimal atomic ratio of Pr/Co for 6% cobalt-silica gel catalysts was found to be between 0.26 and 0.35. Spectroscopic and other experimental results show that impregnated praseodymium readily substitutes the surface silicon atoms to form negatively charged centres on the surface of the support. Due to the presence of praseodymium, the deposited cobalt species can partially react with the support. Consequently, significant amounts of surface cobalt silicates or hydrosilicates can be formed. Most of these species undergo reduction during activation and can be converted to a metallic cobalt phase that remains incorporated at the silica surface. Refereed/Peer-reviewed

In Merensky (Bushveld Complex, South Africa) ore flotation, normally more than 2% of the gangue minerals,principally pyroxene with minor chromite, reports to the concentrate diluting the PGM recovery and contributing to subsequent processing costs. Understanding and controlling the mechanisms that cause this misreporting remains a primary target in PGM flotation. The orthopyroxene in Merensky ore can develop floatable properties through chemical interactions in the flotation system, principally through inadvertent copper-collector complexation, but this paper shows that this mechanism does not fully account for the true flotation of large pyroxene (20–150 µm) particles. Statistical comparison of ToF-SIMS analysis of particles from concentrate and tails reveals no significant difference in Cu and collector (IBX, DTP) signals between these streams but surface exposure of Mg and Si is favoured in the concentrate. Flotation of pyroxene without collector has confirmed this statistical discrimination. Hydrophobic talc-like residual layers, probably from partial serpentinisation of the pyroxene, seen in XRD differences between the concentrate and tails, explain this flotation mechanism. Refereed/Peer-reviewed

A study of polyaniline (PANI), poly-o-toluidine (POT) and poly-o-anisidine (POA) cobalt supported catalysts has been presented. The catalysts were prepared by depositing cobalt species onto the polymers surfaces. Cobalt(II) acetate and N,N′-ethylene-bis(salicylideneimine) cobalt(II) (Co(II)Salen) were used in the syntheses. The catalysts performance was examined in epoxidation of trans-stilbene by molecular oxygen and they turned out to be very efficient under mild conditions. The relationship between the surface exposure of cobalt species and the activity of these polymeric catalysts has been established.