Doctoral theses
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Current Record: 2022 of 2443
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| Identifier |
000376233 |
| Title |
Environment-dependent shape and properties of gold nanoparticles/ : a first principles study |
| Alternative Title |
Σχήμα και ιδιότητες νανοσωματιδίων χρυσού σε διάφορα περιβάλλοντα |
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Author
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Μπαρμπαρής, Γεώργιος Δημ
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Thesis advisor
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Ρεμεδιάκης, Ιωάννης
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Reviewer
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Αναστασιάδης, Σπύρος
Ανδριώτης, Αντώνης
Φαράντος, Σταύρος
Φρουδάκης, Γεώργιος
Κιοσέογλου, Γεώργιος
Κοπιδάκης, Γεώργιος
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| Abstract |
In the present Thesis a computational study that links extensive quantum- mechanical calculations, based on
density functional theory (DFT), to Wulff constructions in order to predict the environment-dependent
equilibrium shape and properties of large gold nanoparticles is presented.
We firstly present the methodology used to obtain the equilibrium shape, including the main aspects of the
density functional theory and the Wulff construction method. We continue by presenting the code developed
to construct any clean or having a molecule adsorbed at a given site Au(hkl) surface. Then, we study the adsorption
of CO and the dissociative adsorption of dimethyl disulfide (CH3S-SCH3) on every possible
Au(hkl) with h,k,l ≤ 3 plus the kinked Au(421) and we dis- cuss trends on adsorption energies, bond lengths
and bond angles as the surface structure changes.
We calculate the surface energy per unit area for clean surfaces and use it together with the Wulff
construction method to predict the equilibrium shape of clean gold nanoparticles with diameters up to
several tenths of a nanometer, in-accessible by direct atomistic simulations. We also present the codes
developed to construct atomistic models of nanoparticles using the Wulff construction method and analyse
the geometrical features of them. We point out a surprising agreement between Wulff construction,
experiments, and atomistic simulations at small sizes. Au nanoparticles smaller than 16.3 nm in diameter
have truncated octahedral shape, exposing only (111) and (100) faces. Larger nanoparticles also expose
higher-index faces, mostly (332).
Then we use the surface energies per unit area and the results for the adsorption energy to obtain the
interface energy per unit area between Au and CO or Au and thiolates (CH3S-) at low pressure and temperature. These results are then used to obtain the equilibrium shape of CO- or thiolate-covered Au
nanoparticles. In agreement with experimental data, Au nanoparticles in CO are found to be more spherical
and more reactive compared to Au nanoparticles in noninteracting environments. Gold nanoparticles change their shape upon adsorption of thiolates towards shapes of higher sphericity and higher concentration of
step-edge atoms.
Finally, we check the stability of these nanoparticles through Molecular Dynamics simulations and we
present a theoretical method providing shape-dependent spectroscopic properties of gold nanoparticles.
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| Language |
Greek, English |
| Subject |
Adsorption |
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CO |
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Thiolates |
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Θειολικές ενώσεις |
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Μονοξείδιο |
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Νανοσωματίδια |
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Προσρόφηση |
| Issue date |
2012 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Doctoral theses
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Type of Work--Doctoral theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/b/5/e/metadata-dlib-1352104023-533204-23933.tkl
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| Views |
441 |
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