Tran, Dung Trung (2011)
Ph.D. thesis, University of Birmingham.
This thesis describes computational studies, syntheses and characterization of Cu-Au, Pd-Au, and Pt-Au bimetallic nanoparticles. The computational methodology is a combination of a genetic algorithm coupled with an empirical potential and density functional theory, which is used to study theoretically the geometrical structure, chemical configuration, and electronic properties of 38 atom Cu-Au and 40-atom Pt-Au nanoparticles. Experimental Cu Au and Pt-Au nanoparticles are synthesized by wet-chemical methods: the two-phase method combined with a galvanic exchange procedure (dodecanethiol-stabilized Cu-Au nanoparticles), the polyol method (Polyvinylpyrrolidone stabilized Pt-Au nanoparticles), and the Turkevich-Frens method combined with a successive reduction procedure (citrate-stabilized Pt-Au nanoparticles). The Pd-Au nanoparticles which are characterized in our work were synthesized by a microbial method. The nanoparticles are characterized using transmission electron microscopy (TEM) and scanning TEM (STEM) combined with high angle annular dark field (HAADF) imaging, energy dispersive X-ray elemental mapping using a silicon drift detector (SDD), tomography, and electron energy loss spectroscopy (EELS). Sizes and shapes of the Cu-Au, Pd-Au, and Pt-Au nanoparticles are studied by TEM. Morphological evolution and aggregation of the Cu-Au nanoparticles are also observed under the TEM electron beam. SDD-EDX elemental mapping combined with HAADF contrast is used to study the chemical configuration of all the three systems. HAADF-STEM tomography is performed for the Pd-Au nanoparticles. Surface plasmon resonances of the Cu-Au and Pd-Au nanoparticles are studied using EELS. The structures and configurations of the theoretical bimetallic clusters and the experimental bimetallic nanoparticles are found to be composition-dependent.
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