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Project
Gold Nanoparticles in Ionic Liquids Prepared by Sputter Deposition.
The ability to synthesize monodisperse NPs with predetermined size and shape of a specific composition is still limited and keeps challenging the scientific community. Even more limited is the knowledge about mechanisms of nanoparticle formation. This thesis aimed to contribute to the understanding of metal nanoparticles synthesis via sputter deposition in ionic liquids. The influence of the ionic liquid on the growth process and on the stability of the nanoparticles was investigated.
The investigation into the synthesis of gold nanoparticles in ionic liquids bysputter deposition rendered some interesting results and revealed some fundamental mechanisms. It is found that primary nanoparticles with a diameter smaller than 2.5 nm are present in the sample immediately after sputtering. Growth of these primary particles proceeds after the end of the sputtering process and stops when the nanoparticles reach a certain size. The IL seems to play a role as capping agent. The growth speed is influenced by the viscosity of the ionic liquid and proceeds slower in more viscous ILs. A discussion on the growth mechanism of sputtered gold NPs is included.
Besides the growth of the gold nanoparticles, twoother processes were observed after sputtering, namely coagulation and sedimentation of the nanoparticles. It was found that the kinetics of aggregation and sedimentation scale with the viscosity of the ionic liquid. Small amounts of water were found to have a detrimental influence on the stability of the colloidal suspensions of the gold nanoparticles in ionic liquids. From the large discrepancy between the theoretical and theexperimentally observed stability of the NPs, it was concluded that structural forces stabilize the gold nanoparticles. This was also borne outby AFM measurements.
During characterization of gold nanoparticles by transmission electron microscopy, solidified, free-standing ionic liquid films were observed. Holes could be made in a solidified free-standing ionic liquid film with a focused ion beam and were shown to be stable for more than one month in contact with atmospheric air. A solidification mechanism is proposed and discussed.
The investigation into the synthesis of gold nanoparticles in ionic liquids bysputter deposition rendered some interesting results and revealed some fundamental mechanisms. It is found that primary nanoparticles with a diameter smaller than 2.5 nm are present in the sample immediately after sputtering. Growth of these primary particles proceeds after the end of the sputtering process and stops when the nanoparticles reach a certain size. The IL seems to play a role as capping agent. The growth speed is influenced by the viscosity of the ionic liquid and proceeds slower in more viscous ILs. A discussion on the growth mechanism of sputtered gold NPs is included.
Besides the growth of the gold nanoparticles, twoother processes were observed after sputtering, namely coagulation and sedimentation of the nanoparticles. It was found that the kinetics of aggregation and sedimentation scale with the viscosity of the ionic liquid. Small amounts of water were found to have a detrimental influence on the stability of the colloidal suspensions of the gold nanoparticles in ionic liquids. From the large discrepancy between the theoretical and theexperimentally observed stability of the NPs, it was concluded that structural forces stabilize the gold nanoparticles. This was also borne outby AFM measurements.
During characterization of gold nanoparticles by transmission electron microscopy, solidified, free-standing ionic liquid films were observed. Holes could be made in a solidified free-standing ionic liquid film with a focused ion beam and were shown to be stable for more than one month in contact with atmospheric air. A solidification mechanism is proposed and discussed.
Date:1 Oct 2008 → 15 Mar 2012
Keywords:electrodeposition, coordination chemistry, rare earths, lanthanides, molten salts, ionic liquids
Disciplines:Inorganic chemistry, Organic chemistry, Theoretical and computational chemistry, Other chemical sciences
Project type:PhD project