XPS studies on the interaction of CeO2 with Silicon in magnetron sputtered CeO2 thin films on Si and Si3N4 substrates

CeO2 thin films were deposited on silicon and silicon nitride substrates by magnetron sputtering at room temperature and annealed at 400 and 600 °C in air and vacuum. Interaction between deposited CeO2 and Si in CeO2/Si and CeO2/Si3N4 systems was investigated by XPS. The results show that Ce is present as both Ce4+ and Ce3+ oxidation states in CeO2 film deposited on Si substrate, whereas Ce4+ is the main species in as-deposited CeO2/Si3N4 film. Detailed analyses of Ce3d, Si2p and O1s core level spectra demonstrate that Ce2O3 and SiOx or cerium silicate type of species are formed at the interface of CeO2 and Si. Concentrations of Ce3+ species increase drastically in CeO2/Si thin films after annealing at 400 °C in vacuum due to enhanced interfacial reaction. On the other hand, interfacial reaction between CeO2 and Si3N4 substrate is limited in as-deposited as well as 600 °C heat treated films

Removal of heavy metals by biosorption

Industrialization and urbanization have resulted in increased releases of toxic heavy metals into the natural environment comprising soils, lakes, rivers, groundwaters and oceans. Research on biosorption of heavy metals has led to the identification of a number of microbial biomass types that are extremely effective in bioconcentrating metals. Biosorption is the binding and concentration of adsorbate from aqueous solutions by certain types of inactive and dead microbial biomass. The novel types of biosorbents presently reviewed are grouped under fungal biomass, biomass of non-living, dried brown marine algae, agricultural wastes and residues, composite chitosan biosorbent prepared by coating chitosan, cellulose-based sorbents and bacterial strains. The reports discussed in this review collectively suggest the promise of biosorption as a novel and green bioremediation technique for heavy metal pollutants from contaminated natural waters and wastewaters

Control and enhancement of the oxygen storage capacity of ceria films by variation of the deposition gas atmosphere during pulsed DC magnetron sputtering

In this study, nanostructured ceria (CeO2) films are deposited on Si(100) and ITO coated glass substrates by pulsed DC magnetron sputtering using a CeO2 target. The influence on the films of using various gas ambients, such as a high purity Ar and a gas mixture of high purity Ar and O-2, in the sputtering chamber during deposition are studied. The film compositions are studied using XPS and SIMS. These spectra show a phase transition from cubic CeO2 to hexagonal Ce2O3 due to the sputtering process. This is related to the transformation of Ce4+ to Ce3+ and indicates a chemically reduced state of CeO2 due to the formation of oxygen vacancies. TGA and electrochemical cyclic voltammetry (CV) studies show that films deposited in an Ar atmosphere have a higher oxygen storage capacity (OSC) compared to films deposited in the presence of O-2. CV results specifically show a linear variation with scan rate of the anodic peak currents for both films and the double layer capacitance values for films deposited in Ar/O-2 mixed and Ar atmosphere are (1.6 +/- 0.2) x 10(-4) F and (4.3 +/- 0.5) x 10(-4) F, respectively. Also, TGA data shows that Ar sputtered samples have a tendency to greater oxygen losses upon reduction compared to the films sputtered in an Ar/O-2 mixed atmosphere. (C) 2015 Elsevier B.V. All rights reserved

Alternate spore stages of Myxobilatus gasterostei, a myxosporean parasite of three-spined sticklebacks (Gasterosteus aculeatus) and oligochaetes (Nais communis)

Two spore stages in the life cycle of Myxobilatus gasterostei, a ubiquitous myxosporean parasite of three-spined sticklebacks, were identified by matching small subunit ribosomal RNA gene sequences of actinospores from a worm with myxospores from fish. A Nais communis oligochaete collected in the Willamette River, Oregon, USA was found to produce a triactinomyxon-type actinospore which was distinguishable from previous records by its large size (approximately 500 microm across) and number of germ cells (approximately 500). Its small subunit ribosomal RNA gene sequence was >99% similar to M. gasterostei from Europe. Two of ten sticklebacks from the Willamette had renal infections with Myxobilatus myxospores which were smaller than the type description of M. gasterostei Parisi (1912) but were consistent with subsequent records. Primer Mg1097r was designed to selectively amplify M. gasterostei in the presence of another common kidney myxosporean, Sphaerospora elegans. DNA sequences of spores from the fish were identical to each other and were 99.8% similar over 2,112 nt to the spores from the oligochaete. The 0.2% sequence divergence comprised polymorphisms at five loci, which suggested that multiple alleles were present in the parasite population. This is the first Myxobilatus species shown to have two spore stages in its life cycle and to infect an invertebrate. The infected oligochaete underwent paratomic fission to produce two daughter worms with parasite stages in their intestinal epithelia, which suggested that M. gasterostei may be sustained and dispersed within the invertebrate host population