Thermal properties of Co/Au nanoparticles and comparison of di

ARNALDO RAPALLO, JIMENA A. OLMOS-ASAR, OSCAR A. OVIEDO, MARTÍN LUDUEÑA , RICCARDO FERRANDO AND MARCELO M. MARISCAL

Encuentro; COST MP0903 Discussion meeting; 2013

In the last years, the study of small clusters and nanoparticles (NPs) has been the focus of many investigation areas, such as catalysis, solid state physics, physical-chemistry, biomedicine and optics, to mention some of them[1]. Thermal stability is one of the basic requirements for a NP to be used in biological applications. Therefore, it is of great importance to study the thermal behavior of pure and alloyed metal particles. One of the most relevant aspects is the melting process, i.e., the solid-liquid transition. Metal nanoparticles usually have melting temperatures much lower than bulk, due to the high surface-to-volume ratio. The lowering in the melting point as the particle size decreases is a phenomenon commonly observed both at the experimental and theoretical levels[2]. From a theoretical view point, the melting of metal NPs has been studied with classical thermodynamic methods[1]. Many of these studies employed computational simulations, from where it can be extracted the atomic structure and energy distributions of the system simultaneously. Many results show that nanoalloys can suer complex structural transformations before the melting takes place. The simulation methods more widely employed in this eld are canonical Monte Carlo and canonical Molecular Dynamics. However, comparison between these computational techniques in the literature is scarce. In this work we present the study of the melting of metal NPs with dierent computational techniques. We chose Co, Au and Co/Au nanoparticles as model systems, due to the high interest for applications in dierent elds. NPs which contain Co are chemically reactives and ferromagnetic. Due to the fact that Co and Au form NPs with structure Cocore-Aushell, in these structures the less reactive and biocompatible metal is in contact with the media, whereas the Co core keeps its magnetic properties. A surprising enhancement in the thermal stability of core/shell Co13Au42 is observed compared to both pure clusters of the same size and shape[3].