In this work we present an atomistic simulation study analyzing the effect of ligand molecules on the morphology and crystalline structure of monolayer protected gold nanoparticles (NPs). In particular, we focused on Au NPs covered with alkyl thiolates (-SR), which form a strong covalent bond with the Au surface, and alkyl amines (-NH2R), which physisorb onto gold. The atomic interactions between gold and the head groups of ligand molecules were represented by means of a recently developed bond-order potential [Olmos-Asar et al., Phys. Chem. Chem. Phys., 2011, 13, 6500]. We found in the case of strong passivants (i.e. -SR) significant surface damage and/or amorphous-like structures, whereas soft passivants (-NH2R) do not produce almost any distortion in the crystalline structure of the metallic NPs. The enriched coverage degree related to flat surfaces is also discussed. We have also demonstrated that the new semi-empirical potential can reproduce low-coordinated adsorption sites, unlike usual pairwise classical potentials. In general, our simulations provide a direct observation of the structure of ligand protected gold nanoparticles.

In this work we investigate the performance of several simulation techniques, i.e., Canonical Molecular Dynamics, Canonical Monte Carlo, and the Optimized Multicanonical Monte Carlo, to study melting-like transitions of Co/Au nanoalloys that are compared to those of pure Co and Au clusters of the same size. A surprising enhancement in the thermal stability of core/shell Co 13 Au 42 is observed compared to both pure clusters of the same size and shape. The novel property is analyzed using energetic and vibrational contributions throughout a detailed microscopic dynamic analysis.

Nanotherapeutics is a promising field for numerous diseases and represents the forefront of modern medicine. In the present work, full atomistic computer simulations were applied to study poly(lactic acid) (PLA) nanoparticles conjugated with polyethylene glycol (PEG). The formation of this complex system was simulated using the reactive polarizable force field (ReaxFF). A full picture of the morphology, charge and functional group distribution is given. We found that all terminal groups (carboxylic acid, methoxy and amino) are randomly distributed at the surface of the nanoparticles. The surface design of NPs requires that the charged groups must surround the surface region for an optimal functionalization/charge distribution, which is a key factor in determining physicochemical interactions with different biological molecules inside the organism. Another important point that was investigated was the encapsulation of drugs in these nanocarriers and the prediction of the polymer–drug interactions, which provided a better insight into structural features that could affect the effectiveness of drug loading. We employed blind docking to predict NP–drug affinity testing on an antiaggregant compound, cilostazol. The results suggest that the combination of molecular dynamics ReaxFF simulations and blind docking techniques can be used as an explorative tool prior to experiments, which is useful for rational design of new drug delivery systems.