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Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol

In recent years, gold nanoparticles (AuNPs) have received considerable attention owing to their unique properties which are promising in diverse fields and applications such as biomedical science and catalysis. AuNPs has been considered as the catalyst of choice for numerous organic reactions. Vast...

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Main Author: Borhamdin, Suhaila
Format: Thesis
Language:English
Published: 2019
Subjects:
QD Chemistry
Online Access:http://eprints.utm.my/id/eprint/102260/1/SuhailaBorhamdinPFS2019.pdf.pdf
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spelling my.utm.1022602023-08-13T06:17:58Z http://eprints.utm.my/id/eprint/102260/ Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol Borhamdin, Suhaila QD Chemistry In recent years, gold nanoparticles (AuNPs) have received considerable attention owing to their unique properties which are promising in diverse fields and applications such as biomedical science and catalysis. AuNPs has been considered as the catalyst of choice for numerous organic reactions. Vast numbers of chemical, physical and biological strategies have been employed to synthesise AuNPs. Among these approaches, the biological method employing plant extract is gaining attention as it is simple and environmentally friendly. In this research, a green biosynthetic approach for the preparation of AuNPs using aqueous leaf extract of Polygonum minus as reducing and stabilising agent is described. The reduction of Au(III) ions to elemental Au occurred rapidly and it was completed within 20 min at room temperature as monitored by ultraviolet-visible (UV-Vis) spectroscopy. High resolution transmission electron microscopy/energy-dispersive X-ray (HRTEM/ EDX) and X-ray diffraction (XRD) analytical data indicated that the nanoparticles were in fcc crystalline shape, mostly icosahedral and nearly monodispersed with an average size of 23 ± 5.1 nm. Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV) analyses of the AuNPs and the leaf extract revealed that the oxidised (quinone) form of quercetin and myricetin were presumably the main stabilising agents in the formation of stable nanoparticles. The biosynthesised AuNPs showed good catalytic activity, with a turnover frequency (TOF) of 85.2 h-1 for the oxidation of benzyl alcohol and a normalised rate constant, Knor of 0.06 s-1 mmol-1 in the reduction of 4-nitrophenol. The same bioreduction process was employed in the preparation of AuNPs catalysts supported on highly branched metforminfunctionalised silica-coated magnetite (Fe3O4-SiO2-Met). The structural, surface and magnetic properties of the support material (Fe3O4-SiO2-Met) was investigated by FTIR, XRD, HRTEM/EDX, elemental carbon-hydrogen-nitrogen (CHN), thermogravimetry (TGA) and vibrating sample magnetometry (VSM) analyses. The XRD, HRTEM/EDX, X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS) analytical data revealed that AuNPs with smaller average sizes (6.1 ± 2.2 nm and 16.2 ± 8.3 nm) were well-dispersed on the Fe3O4- SiO2-Met support. Under optimum benzyl alcohol oxidation reaction conditions, 0.3% Au/Fe3O4-SiO2-Met catalyst displayed an enhanced catalytic performance as compared to the unsupported AuNPs, with a TOF improvement factor of 2.5. Meanwhile, the catalytic performance of the 6% Au/Fe3O4-SiO2-Met catalyst showed enhancement with an increase in the normalised rate constant, Knor value by a factor of 8.8 as compared to the unsupported AuNPs under an optimised 4-nitrophenol reduction reaction conditions. The supported AuNPs catalyst could be easily recovered magnetically and reused for at least four times and three times in the oxidation and reduction reactions, respectively, without significant loss of activity. 2019 Thesis NonPeerReviewed application/pdf en http://eprints.utm.my/id/eprint/102260/1/SuhailaBorhamdinPFS2019.pdf.pdf Borhamdin, Suhaila (2019) Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol. PhD thesis, Universiti Teknologi Malaysia. http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:146054
institution Universiti Teknologi Malaysia
building UTM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Malaysia
content_source UTM Institutional Repository
url_provider http://eprints.utm.my/
language English
topic QD Chemistry
spellingShingle QD Chemistry
Borhamdin, Suhaila
Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
description In recent years, gold nanoparticles (AuNPs) have received considerable attention owing to their unique properties which are promising in diverse fields and applications such as biomedical science and catalysis. AuNPs has been considered as the catalyst of choice for numerous organic reactions. Vast numbers of chemical, physical and biological strategies have been employed to synthesise AuNPs. Among these approaches, the biological method employing plant extract is gaining attention as it is simple and environmentally friendly. In this research, a green biosynthetic approach for the preparation of AuNPs using aqueous leaf extract of Polygonum minus as reducing and stabilising agent is described. The reduction of Au(III) ions to elemental Au occurred rapidly and it was completed within 20 min at room temperature as monitored by ultraviolet-visible (UV-Vis) spectroscopy. High resolution transmission electron microscopy/energy-dispersive X-ray (HRTEM/ EDX) and X-ray diffraction (XRD) analytical data indicated that the nanoparticles were in fcc crystalline shape, mostly icosahedral and nearly monodispersed with an average size of 23 ± 5.1 nm. Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV) analyses of the AuNPs and the leaf extract revealed that the oxidised (quinone) form of quercetin and myricetin were presumably the main stabilising agents in the formation of stable nanoparticles. The biosynthesised AuNPs showed good catalytic activity, with a turnover frequency (TOF) of 85.2 h-1 for the oxidation of benzyl alcohol and a normalised rate constant, Knor of 0.06 s-1 mmol-1 in the reduction of 4-nitrophenol. The same bioreduction process was employed in the preparation of AuNPs catalysts supported on highly branched metforminfunctionalised silica-coated magnetite (Fe3O4-SiO2-Met). The structural, surface and magnetic properties of the support material (Fe3O4-SiO2-Met) was investigated by FTIR, XRD, HRTEM/EDX, elemental carbon-hydrogen-nitrogen (CHN), thermogravimetry (TGA) and vibrating sample magnetometry (VSM) analyses. The XRD, HRTEM/EDX, X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS) analytical data revealed that AuNPs with smaller average sizes (6.1 ± 2.2 nm and 16.2 ± 8.3 nm) were well-dispersed on the Fe3O4- SiO2-Met support. Under optimum benzyl alcohol oxidation reaction conditions, 0.3% Au/Fe3O4-SiO2-Met catalyst displayed an enhanced catalytic performance as compared to the unsupported AuNPs, with a TOF improvement factor of 2.5. Meanwhile, the catalytic performance of the 6% Au/Fe3O4-SiO2-Met catalyst showed enhancement with an increase in the normalised rate constant, Knor value by a factor of 8.8 as compared to the unsupported AuNPs under an optimised 4-nitrophenol reduction reaction conditions. The supported AuNPs catalyst could be easily recovered magnetically and reused for at least four times and three times in the oxidation and reduction reactions, respectively, without significant loss of activity.
format Thesis
author Borhamdin, Suhaila
author_facet Borhamdin, Suhaila
author_sort Borhamdin, Suhaila
title Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
title_short Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
title_full Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
title_fullStr Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
title_full_unstemmed Magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
title_sort magnetically recoverable biosynthesised gold nanoparticles as catalysts for oxidation of benzyl alcohol and reduction of 4-nitrophenol
publishDate 2019
url http://eprints.utm.my/id/eprint/102260/1/SuhailaBorhamdinPFS2019.pdf.pdf
http://eprints.utm.my/id/eprint/102260/
http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:146054
_version_ 1775621961286680576
score 13.211869

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