Nanoparticulate nickel sulfide

Huang, Shanshan 2008. Nanoparticulate nickel sulfide. PhD Thesis, Cardiff University.

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Abstract

Nickel sulfide possesses a variety of typical structures and stoichiometries that distinguish itself from iron sulfide and exhibits unique roles in the prebiotic reactions which are proposed to be involved in the origin of life. Nickel sulfide precipitate is hydrated and nanocrystalline, modelled as a 4 nm sphere with a 1 nm crystalline and anhydrous NiS (millerite) core, surrounded by a hydrated and defective mantle phase. It is a metastable but fairly robust structural configuration. It may be formulated as NiSxFbOx approximates to 1.5 and decreases on heating. The fresh nanoparticulate nickel sulfide precipitates undergo structural transformation from the initial millerite-like NiS to the more crystalline polydymite-like Ni3S4. This reaction is accompanied by the formation of a less crystalline Ni3S2 (heazlewoodite) phase. The reaction, happening in ambient conditions, occurs more readily for the solids precipitated from acidic environments (i.e., pH 3) and may be facilitated by the hydrogen and water bonding contained in this material. The performance of nickel sulfide and iron sulfide precipitates is investigated in the formaldehyde world under ambient and sulfidic environments which mimic the ambient ancient Earth environments to some extent. The catalytic capacity of the metal sulfides is not obvious in these experiments. An interesting finding is that, trithiane, the cyclic (SCH2)3, also suppresses the pyrite formation and thus promotes the greigite formation in the reaction between FeS and H2S. This provides another cause for the greigite formation in the Earth sedimentary systems and adds information to the origin-of-life theory in the iron sulfur world. Voltammetry experiments reveal that the nickel-cysteine complex lowers the overpotential for molecular H2 evolution in sea water to -1.53 V under ambient conditions. This catalytic property of the abiotic nickel-cysteine complex apparently mimics the Ni-S core in some hydrogenase enzymes functioning in physiological conditions. This bridges the abiotic and biotic worlds and supports the idea that life originated in the prebiotic ancient ocean.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
ISBN:	9781303213618
Date of First Compliant Deposit:	30 March 2016
Last Modified:	10 Jan 2018 03:44
URI:	https://orca.cardiff.ac.uk/id/eprint/54754

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