The Concept of Localized Atomic Mobility: Unraveling Properties of Nanoparticles

The concept of short time scale mean-square displacement (MSD) was used to get a picture of the distribution of atomic mobilities in different layers and regions of Au and Pt nanoparticles (NPs). The NPs were simulated in vacuum at different temperatures using molecular dynamics and the embedded-atom model. The calculated atomic mobilities were greater for atoms located at corner positions, followed by atoms on edges and planes, independently of the layer analyzed. The short time scale MSD was revealed to be an excellent alternative to predict melting temperatures of small (<100 atoms) transition-metal NPs. Finally, the combination of classical (MSD) and quantum (density of states) properties brought some insight into how the catalytic activity may locally change over the NP surface. The trends found for subnanometer-sized NPs indicate that corner, kinks, and defect regions play a major role for the catalytic activity of these particles

Cooperative Supramolecular Polymerization Driven by Metallophilic Pd···Pd Interactions

A new oligophenyleneethynylene (OPE)-based Pd­(II) pyridyl complex has been synthesized, and its self-assembly has been investigated in solution, in the bulk state, and on surfaces. Detailed analysis of concentration- and temperature-dependent UV–vis studies in methylcyclohexane supported by DFT calculations demonstrate for the first time that cooperative supramolecular polymerization processes can be driven by metallophilic interactions

Palladium-Mediated Catalysis Leads to Intramolecular Narcissistic Self-Sorting on a Cavitand Platform

Palladium-catalyzed aminocarbonylation reactions have been used to directly convert a tetraiodocavitand intermediate into the corresponding carboxamides and 2-ketocarboxamides. When complex mixtures of the amine reactants are employed in competition experiments using polar solvents, such as DMF, no “mixed” products possessing structurally different amide fragments are detected either by ¹H or ¹³C NMR. Only highly symmetrical cavitands are sorted out of a large number of potentially feasible products, which represents a rare example of intramolecular, narcissistic self-sorting. Our experimental results along with thermodynamic energy analysis suggest that the observed self-sorting is a symmetry-driven, kinetically controlled process

Impact of the AuAg NPs Composition on Their Structure and Properties: A Theoretical and Experimental Investigation

Bimetallic AuAg NPs (NPs) were synthesized via chemical reduction of AuCl₃ and AgNO₃ and fully characterized by several experimental techniques and theoretical calculations. The plasmon absorptions of these NPs were correlated with the most stable particle structure through different simulations, revealing the most stable structure to be consisted of a gold core and a silver shell. This structural motif was then confirmed by HR-TEM coupled with line-scan EDS and molecular dynamics. Finally, the impact of the nanoparticle composition on their catalytic performance for glycerol electrooxidation was evaluated. The better catalytic performance in terms of the onset potential found for the Au₅₀Ag₅₀ and Au₇₅Ag₂₅ catalysts suggests the existence of a synergistic effect between Au and Ag