Analysis of biogenic magnetite nanoparticles

Cobalt doped magnetite (CoxFe3-xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by SQUID, x-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to <4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites.

Organic petrography and extractable hydrocarbons of sediments at DSDP Leg 58 Holes

The quantity, type, and maturity of organic matter of Quaternary and Tertiary sediments from the Philippine Sea (DSDP Leg 58; Sites 442-446) were determined. Hydrocarbons in lipid extracts were analyzed by capillary-column gas chromatography. Kerogen concentrates were investigated by microscopy for vitrinite reflectance values and maceral composition. In the Shikoku Basin sediments (Sites 442, 443, and 444), organic carbon values range between 0.03 and 0.44 per cent. The higher values in the younger sediments are interpreted as an indication of increasing deposition of eroded organic particles during the past 4 m.y. Microscopic analyses revealed a dominance of reworked organic matter. Primary material could not be distinguished readily; thus, no maturation trend could be established. Extract yields were low. TV-alkane distributions mostly show maxima at n-C29 and n-C31 and high odd-over-even predominances, typical of material which originated in terrigenous higher plants. The organic-carbon values of sediments of the Daito Ridge and Basin region (Sites 444 and 445) range from less than 0.01 to 0.05 per cent. TV-alkanes exhibit varying marine and terrigenous influences. Some carbonate-rich samples show a pronounced even-over-odd predominance. At least the older sediments contained less recycled organic matter than the Shikoku Basin samples. The maturity, where measurable, was low. None of the Philippine Sea samples indicates a significant hydrocarbon-generation potential.