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Functionalisation of graphite surfaces with varying concentrations of nitric acid and aqua regia, and their effect on the deposition of gold nanoparticles

Wotton, Daniel 2017. Functionalisation of graphite surfaces with varying concentrations of nitric acid and aqua regia, and their effect on the deposition of gold nanoparticles. MPhil Thesis, Cardiff University.
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Abstract

The surface science of graphite surfaces for real world applications currently is poorly understood but shows promise in certain chemical industries such as acetylene hydrochlorination and thiosulfate leaching of preg-robbing ores. In this work the role of oxygen functional groups on the surface of HOPG introduced through acid treatment with nitric acid, aqua regia and sulfuric acid has been explored to determine how these functionalities influence the deposition of gold nanoparticles. Previous work by Cardiff University has determined that acid treatment with 0.5 moldm-3 nitric acid introduces hydroxyl groups onto the surface determined by selective derivatization. Heating of these surfaces creates ketones and ethers and that these differences in functionality change how gold is deposited on the surface. HAuCl4 treatment of HNO3 activated HOPG resulted in very little gold deposition on the surface when using low concentrations of nitric acid or no nitric acid. At nitric acid concentrations of 1.0M or higher there is a large increase in the quantities of gold on the surface. Higher concentrations showed an increase in the ratio of Au(III) to Au(0) deposited. In aqua regia treated surfaces higher concentrations resulted in more ketone present on the surface as determined by selective derivatization. This effected gold deposition by showing a large increase in Au(0) deposited at these higher aqua regia concentrations. Sulfuric acid activated samples showed sulfur being incorporated into the HOPG samples. Dilute concentrations of sulfuric acid were required to deposit large amounts of gold and all gold deposited was in the form of Au(0). The results and conclusions derived from them give insight into the effect of acid washing with different acids and their effect on the subsequent loading of the active gold ion.

Item Type: Thesis (MPhil)
Status: Unpublished
Schools: Chemistry
Funders: Welsh Government
Date of First Compliant Deposit: 19 June 2018
Last Modified: 08 May 2019 01:56
URI: http://orca-mwe.cf.ac.uk/id/eprint/112553

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