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Core-shell nanoparticle models for in-situ SERS measurements of carbonate dissolution under environmentally realistic conditions

Davis, Charles Stuart 2015. Core-shell nanoparticle models for in-situ SERS measurements of carbonate dissolution under environmentally realistic conditions. PhD Thesis, Cardiff University.
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Abstract

Surface enhanced Raman spectroscopy was used in conjunction with cyclic voltammetry to probe the initial stages of the deposition and dissolution of calcium carbonate. Gold nanoparticles were synthesised and employed for their SERS activity so that the weak signal usually associated with calcium carbonate was enhanced to a degree whereby the very initial stages of both deposition and dissolution would be revealed. Reduction potentials were utilised along with electrolyte composition to encourage the deposition and control the phase or morphology of calcium carbonated produced, this was further explored using core-shell type gold nanoparticles with calcium carbonate shells. Novel multinucleated calcite particles were produced with numerous nanoparticle seeds contained within, the presence of which was attributed to the multinucleated nature of the particles, Au@calcium carbonate nanoparticles were also synthesised with various shell features. Gold coated platinum single crystals were produced and calcium carbonate was electrochemically deposited on the surface to probe this interface and ascertain whether epitaxial growth occurred and could be controlled for the purpose of better understanding this interface in the hope that it would better inform of the conditions governing core-shell particle synthesis. It was found that epitaxial growth of calcite occurred on the Au(111) and Au(110) but not the Au(100). Finally the reaction of carbon dioxide with caesium to form carbonate on gold single crystals was studied under ultra-high vacuum conditions. The aim being to improve the understanding of the fundamental properties of carbonates forming and interacting with the gold surface. The development of the carbonate was investigated with XPS and STM. At well annealed, ordered gold surfaces dissolution of Cs into the gold to form CsAu alloys was reversed on adsorption of carbon dioxide and caesium carbonate was formed. On roughened surfaces however, neither Cs dissolution nor carbonate formation was observed. This was attributed to the availability of high energy adsorption sites at the sputtered surface. Thermal decomposition of the carbonates occurred between 473 K and 673 K with the desorption of CO2 and the formation of Cs oxide.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 30 March 2016
Last Modified: 02 Aug 2018 09:07
URI: http://orca-mwe.cf.ac.uk/id/eprint/86355

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