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Type: Thesis
Title: A study into the kinetic formation and oxidation states of gold nanoparticles produced via laser ablation synthesis in solution.
Author: Fong, Yuen-Yan (Mable)
Issue Date: 2012
School/Discipline: School of Chemistry and Physics
Abstract: Nano-sized gold particles are generated by exploiting the laser ablation synthesis in solution technique (LASiS) from gold metal disc. We report on the kinetics of gold nanoparticle (AuNP) production during LASiS and the resulting size distributions. Studies were conducted as a function of laser irradiation in pure water samples, with anionic surfactants, sodium dodecylsulphate (SDS), and cationic surfactants, cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC), in water. Our investigations provide a mechanistic insight into the laser-induced formation kinetics involved in AuNP production via 1064 nm laser irradiation in aqueous solution. This has been achieved by developing a kinetic model involving three different AuNP size regimes. Specifically, we have found that there is no apparent influence of the SDS concentration around the surfactant critical micelle concentration (CMC) on particle size during AuNP production. This is in contrast to results observed for size reduction via 532-nm irradiation where a clear CMC effect has previously been observed. [Yamada et al, J. Phys. Chem. B, 2006, 110, 11751-11756] In addition, we also explore the surface oxidation states of produced AuNPs in various surfactants using X-ray photoelectron spectroscopy (XPS). Our investigations shows the Au¹¹¹ chemical oxidation state was present in produced AuNPs in high concentrations of CTAB and CTAC, but absent in those produced in pure water and SDS solution. Prior to XPS investigations on the LASiS prepared AuNPs, a study to observe the behavior of gold during irradiation of X-rays was performed. We report on the time evolution of the Au oxidation state in sodium tetrachloroaurate NaAuCl₄ as a function of soft X-ray exposure time. Our investigations provide mechanistic insight into the photoreduction kinetics from Au¹¹¹ to Au¹ and then subsequently Au¹ to Au⁰.We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au¹ state.
Advisor: Buntine, Mark Anthony
Metha, Gregory Francis
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2012
Keywords: gold nanoparticle; laser; LASIS; laser ablation; kinetic; oxidation state; formations; sodium dodecylsuphate; SDS; CTAB; CTAC
Provenance: Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
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