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Electrochemical Preparation of Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: An Efficient Catalyst for Cycloisomerization of 4-Alkynoic Acids to Lactones
Stockholm University, Faculty of Science, Department of Organic Chemistry. (Organisk kemi)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described and the thiol-stabilized gold nanoparticles were found to catalyze the cyclization of 4-pentynoic acids to lactones. The reported method is based on an electrochemical oxidation of a gold substrate generating oxidative Au(III) species which give rise to a surface-confined redox reaction yielding MCF supported Au(I)-thiolates. By reducing the MCF-S-Au(I) complex with sodium borohydride thiol-stabilized gold nanoparticles were obtained which were characterized with Transmission Electron Microscopy (TEM). The nanoparticles were found to be in the size of 1-8 nm. Inductive Coupled Plasma (ICP) analysis indicated an Au loading of 3 % (w/w) on the MCF. Further 0.5 mol% of the MCF-S-Au(0) solids were used to catalyze the cyclization reaction of 4-alkynoic acid under mild conditions with high selectivity (> 99%).

National Category
Natural Sciences
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-88208OAI: oai:DiVA.org:su-88208DiVA: diva2:610358
Available from: 2013-03-11 Created: 2013-03-11 Last updated: 2013-03-19Bibliographically approved
In thesis
1. Development and Applications of Surface-Confined Transition Metal Complexes: Heterogeneous Catalysis and Anisotropic Particle Surfaces
Open this publication in new window or tab >>Development and Applications of Surface-Confined Transition Metal Complexes: Heterogeneous Catalysis and Anisotropic Particle Surfaces
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main focus of this thesis has been directed towards developing novel surface-confined transition metal complexes for applications in heterogeneous catalysis and for the preparation of anisotropic particle surfaces. The first part describes the heterogenization of a homogeneous transition metal-based catalyst tetraphenyl cobalt porphyrin (CoTPP) on silicon wafers and on silica particles. The activity in hydroquinone oxidation for the silica particle-immobilized CoTPPs was found to be increased 100-fold compared to its homogeneous congener whereas the silicon wafer-immobilized CoTPPs achieved lower activity due to the formation of clusters of catalyst molecules on the support surface as detected with atomic force microscopy (AFM). The second part of this thesis describes the development and characterization of anisotropic particle-surfaces by electrochemical site-specific oxidation of surface-confined thiols. Reactive patches or gold gradients could be obtained on the particle surfaces depending on the type of working electrode used and on the electrolyte composition. The particle surface functionalities were characterized with X-ray photoelectron spectroscopy (XPS) and the particle-surface-confined patches and gradients were conjugated with proteins to obtain fluorescence for investigation using fluorescence microscopy. Gold-functionalized siliceous mesocellular foams were further demonstrated to be highly efficient and selective catalysts in the cycloisomerization of 4-alkynoic acids to lactones. The final part of this thesis describes the preparation and characterization of palladium nanoparticles heterogenized in the pores of siliceous mesocellular foam. The nanoparticles were analyzed with transmission electron microscopy (TEM) and found to have a size of 1-2 nm. Primary- and secondary benzylic- and allylic alcohols were oxidized by the heterogeneous palladium nanoparticles in high to excellent yields using air atmosphere as the oxygen source. The nanopalladium catalyst was used up to five times without any decrease in activity and the size of the nanoparticles was retained according to TEM.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. 93 p.
Keyword
heterogeneous catalysis, anisotropic particles, protein gradients, nanoparticles
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-88215 (URN)978-91-7447-656-9 (ISBN)
Public defence
2013-04-18, Magnelisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
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Note

At the time of doctoral defence the following paper were unpublished and had a status as follows: Paper1: Manuscript; Paper 4: Manuscript

Available from: 2013-03-26 Created: 2013-03-11 Last updated: 2017-10-11Bibliographically approved

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