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In this work, we report a facile synthesis route, structural characterization, and full atomistic simulations of gold–palladium nanoalloys. Through aberration corrected-STEM, UV-vis spectroscopy and EDS chemical analysis, we were able to determine that Au(core)–Pd(shell) bimetallic nanoparticles were formed. Using different computational approaches, we were capable of establishing how the size of the core and the thickness of the shell will affect the thermodynamic stability of several core–shell nanoalloys. Finally, grand canonical simulations using different sampling procedures were used to study the growth mechanism of Pd atoms on Au seeds of different shapes.

Customarily, it is likely that irradiated graphene yield indication of per- turbations induced by irradiation. High Resolution Transmission Electron Micros- copy (HRTEM) analysis has been performed on proton irradiated graphene. The analysis indicates the existence of Moiré patterns produced by the rotations induced by the irradiation in between planes. The rotations measured fluctuate between 3 and 5 degrees respectively. These rotations may influence the electronic properties of the material under investigation. In order to explain the observed rotations in between planes, theoretical analysis were performed under the scheme of extended Hückel tight-binding method. Average total energy of the system was careful ana- lyzed throughout the experiment composed of two graphene layers with two carbon vacancies and then the replaced carbons were intercalated in between the two lay- ers. The results obtained indicate that the system remain semi metallic. Moreover, the theoretical results yielded that the 3 degree rotation is favored, although the 5 degree rotation is not discarded. Furthermore, energy bands as well as total and projected DOS were performed in order to provide more information about the electronic changes induced by the rotations applied to the system.

Highly monodispersed Cu–Pt bimetallic nanoclusters were synthesized by a facile synthesis approach. Analysis of transmission electron microscopy (TEM) and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM) images shows that the average diameter of the Cu–Pt nanoclusters is 3.0 ± 1.0 nm. The high angle annular dark field (HAADF-STEM) images, intensity profiles, and energy dispersive X-ray spectroscopy (EDX) line scans, allowed us to study the distribution of Cu and Pt with atomistic resolution, finding that Pt is embedded randomly in the Cu lattice. A novel simulation method is applied to study the growth mechanism, which shows the formation of alloy structures in good agreement with the experimental evidence. The findings give insight into the formation mechanism of the nanosized Cu–Pt bimetallic catalysts.

The role that protecting molecules have on the way that palladium atoms arrange themselves in nanoparticles prepared at room temperature was studied by the analysis of aberration-corrected scanning transmission electron microscopy images and atomistic Langevin dynamics simulations. It was found that the arrangement of Pd atoms is less ordered in thiolate-protected nanoparticles than in amine-protected ones. The experimental and theoretical data showed that the disorder in ∼3 nm thiolate-protected particles is promoted by the strong S−Pd bond in the sulfide layer that surrounds the nanoparticles.

Gold–copper (Au–Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core–shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations.

Au-core, Au3Cu-alloyed shell nanoparticles passivated with CuS2 were fabricated by the polyol method, and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu alloyed shell surrounded by CuS2 surface layer. X-ray diffraction measurements and results from numerical simulations confirm these findings. From the atomic resolution micrographs, we identified edge dislocations at the twin boundaries of the particles, as well as evidence of the diffusion of Cu atoms into the Au region, and the reordering of the lattice on the surface, close to the vertices of the particle. These defects will impact the atomic and electronic structures, thereby changing the physical and chemical properties of the nanoparticles. On the other hand, we show for the first time the formation of an ordered superlattice of Au3Cu and a self-capping layer made using one of the alloy metals. This has significant consequences on the physical mechanism that form multicomponent nanoparticles.

We report the synthesis, structural characterization, and atomistic simulations of AgPd–Pt trimetallic (TM) nanoparticles. Two types of structure were synthesized using a relatively facile chemical method: multiply twinned core–shell, and hollow particles. The nanoparticles were small in size, with an average diameter of 11 nm and a narrow distribution, and their characterization by aberration corrected scanning transmission electron microscopy allowed us to probe the structure of the particles at an atomistic level. In some nanoparticles, the formation of a hollow structure was also observed, that facilitates the alloying of Ag and Pt in the shell region and the segregation of Ag atoms on the surface, affecting the catalytic activity and stability. We also investigated the growth mechanism of the nanoparticles using grand canonical Monte Carlo simulations, and we have found that Pt regions grow at overpotentials on the AgPd nanoalloys, forming 3D islands at the early stages of the deposition process. We found very good agreement between the simulated structures and those observed experimentally.

The fabrication of bimetallic magnetic nanoparticles (NPs) smaller than the size of single magnetic domain is very challenging because of the agglomeration, non-uniform size, and possible complex chemistry at nanoscale. In this paper, we present an alloyed ferromagnetic 4 ± 1 nm thiolated Au/Co magnetic NPs with decahedral and icosahedral shape. The NPs were characterized by Cs-corrected scanning transmission electron microscopy (STEM) and weretheoretically studied by Grand Canonical Monte Carlo simulations. Comparison of Z-contrast imaging and energy dispersive x-ray spectroscopy used jointly with STEM simulated images from theoretical models uniquely showed an inhomo- geneous alloying with minor segregation. The magnetic measurements obtained from superconducting quantum interference device magnet- ometer exhibited ferromagnetic behavior. This magnetic nanoalloy in the range of single domain is fully magnetized and carries significance as a promising candidate for magnetic data recording, permanent magnetization, and biomedical applications.