Synthesis of size controlled metal nanoparticles using microwave and sonochemical approaches

Simplicio Grasina, Manuel 2019. Synthesis of size controlled metal nanoparticles using microwave and sonochemical approaches. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This work aimed to produce using different and new microwave and ultrasound protocols monometallic metal nanoparticles of gold, palladium, silver, iridium and copper (Au, Pd, Ag, Ir and Cu) and bimetallic alloys of AuPd. The developed batch and continuous flow protocols originated from batch optimisation work mainly carried out with microwave synthesis of Au nanoparticles and were based on the sol-immobilization method with the production of stabilized colloids in water, organic solvents or a mixture of both, with PVA and PVP being used as stabilizers and ethylene glycol as the main organic solvent. The produced metal nanoparticles will be used for improving and developing current catalytic applications and eventually will be hugely beneficial for society. To tackle this multidisciplinary project the following targets have been chosen: To develop new metal nanoparticles synthesis protocols characterised by reduced synthesis time, improved production, minimal operation cost, minimal use of toxic reagents and controlled size and shape and to utilise the synthesised materials to convert fossil and bio-renewable feedstock via sustainable catalytic processes. This thesis could be divided into four areas: The first (chapter 3) focused on microwave synthesis of monometallic metal nanoparticles of Au, Pd, Ag, Ir and Cu and bimetallic metal nanoparticles of the alloy type of AuPd at different molar ratios (7:1, 3:1, 1:1, 1:3, 1:7). This included work carried out under batch and continuous flow regime; The second (chapter 4) focused on ultrasound synthesis of monometallic metal nanoparticles of Au, Pd and bimetallic metal nanoparticles of the alloy type of AuPd at a molar ratio of 1:1. All work was carried out under batch regime; The third (chapter 5) saw the application of several characterisation techniques (TEM, SEM/EDX, XPS and DRIFTS) to selected metal nanoparticles produced by microwave and ultrasound synthesis and supported on TiO2, C and CeO2. This provided important information regarding particles average size, shape, loading, composition, stabilizer traces and oxidation state; The fourth (chapter 6) focused on catalytic testing of some of the supported metal nanoparticles by using them as heterogeneous catalysts in liquid/gas phase reactions. In total seven reactions were tested, namely 4-nitrophenol reduction, carbon monoxide oxidation, propane total oxidation, furfural hydrogenation, cinnamaldehyde hydrogenation, formic acid decomposition and hydrazine decomposition; Even though some future work is mentioned in chapter 7, the main conclusion is that the new non-conventional synthesis protocols developed for this work have already allowed to address challenging issues in the areas of green chemistry, catalysis and materials design. This positive outcome offers a potential impact in future projects relating to water purification, biomass transformation and hydrogen storage and production.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	5 May 2020
Last Modified:	13 Mar 2021 02:20
URI:	https://orca.cardiff.ac.uk/id/eprint/131462

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