Thermodynamic and Kinetic properties of bare and capped nanoparticles

J. A. OLMOS ASAR; A. RAPALLO; M. M. MARISCAL

Laussane

Workshop; CECAM Workshop, Nanoscale alloys: from experiment and theory to quantitative modelling; 2010

CECAM

Nowadays, nanomaterials are of great interest in several research areas as well on many technological applications, mainly due that they have some properties that depend specifically on their size and geometry. Those materials are useful when a high area/volume ratio is required. Some of their applications include biosensors, catalysis, drug “delivery” and construction of nano-circuits , , . Preparation, conservation and protection of metallic nanoparticles require passivation with organic ligand molecules if they will remains in a colloidal suspension. When nanoparticles are made of gold, a relatively easy way of protect them is through organic molecular self-assembly, particularly with thiols molecules due to the strong interaction between sulfur and gold atoms. Self-assembly monolayer’s (SAM’s) have been intensively studied, at experimental , , and theoretical level , , , , on extended gold (111) surfaces. Nevertheless, a clear understanding about some fundamental structural aspects of passivated Au nanoparticles in the range of 1-10 nm still does not exist. In the present talk we show a new semiempirical approach to describe molecule-metal interfaces in a realistic way. Using Density Functional calculations (DFT) in combination with the bond-order concept we have developed a new semiempirical framework which in principle is very simple and easy to implement in standard molecular dynamics codes. In particular we show a parameterization for S – Au. The new potential is used in combination with classical force-fields and the second-moment approximation of the tight binding (SMTB) to reproduce the adsorption of alkanethiol molecules on Au planar surfaces and nanoparticles by means of molecular dynamics simulations. Finally, we will show studies which involve the nucleation and growth processes of metal NP´s carried out in solution under control of the chemical potential of the metal ions.