Top (left) and side (right) view of thiolate-covered Au surfaces. (a) Au(111), (b) Au(211), (c) Au(310), and (d) Au(421). A (3 × 3) repetition of the simulation cell is shown.
Dissociative adsorption energy of CH3S−SCH3 on Au(hkl) as a function of the Au coordination number, z, and its linear fit.
Wulff construction for a thiolate-protected Au nanoparticle. The shape consists almost entirely of (211) faces.
Atomistic Wulff construction for thiolate-covered gold nanoparticles at 5.0 and 14.2 nm, respectively. Grey atoms are Au atoms at edges or corners.
(Left) Model of a typical Au nanoparticle (d ∼ 10 nm, ca. 22750 atoms) in non-interacting environment (sphericity = 89%, 78 μmol of active sites per g) (Right) a same size thiolate-protected gold nanoparticle (sphericity = 95%, 299 μmol of active sites per g). Step and kink atoms are shown in darker color.
Properties of methanethiolate adsorption on Au surfaces. A is the area per adsorbate in Å2, and z is the average coordination number of the Au atoms bonded to S. The adsorption geometry is described by three letters: The first refers to the position of the sulfur atom: (t) for on top, (b) for bridge, and (h) for hollow. The second letter defines the orientation of the methyl group: (t) for planar surfaces, (u) for above the upper terrace, and (l) for above the lower terrace in stepped surfaces. The third letter refers to the direction of one hydrogen atom: (t) for towards the surface, (a) for away from the surface, and (p) when all hydrogen atoms are parallel to the surface. E ads is the adsorption energy, ϕAu − S − Au the angle between the S and the two Au atoms bonded to S for bridge and hollow site only, θAu − S − C is the angle between the Au atom bonded to S, the S atom and the carbon. d Au − S and d S − C are the bond lengths between the Au and S atom and the S and C atom respectively.
Ratios of the surface tension of an Au(hkl) surface with respect to the Au(211) surface tension, for covered with CH3S and clean surfaces.
Characteristic values for the stable nanoparticles, including diameter, d, of the Au core in nm, number of the atoms in corners N c , edges N e , surfaces N s , and total N t , the surface area in nm2, the volume in nm3, the active (step) site density N act in μmol/g, and the faces appearing for each nanoparticle with the percentages due to the total area for each one face.
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