Monolayer protected metal nanoparticles, the cases of Au and Pd

J. A. OLMOS ASAR; G. CORTHEY; M. LUDUEÑA; M. FONTICELLI; G. CASILLAS; S. MEJÍA ROSALES; R. SALVAREZZA; M. M. MARISCAL

Antalia

Congreso; ?COST Action conference: Nanoalloys?; 2012

p { margin-bottom: 0.08in; } Colloidal prepared metal nanoparticles (NPs) are gaining attention for catalytic applications because of the advanced possibilities to tailor their size and shape, which are often important factors governing catalytic activity and selectivity. In the case of bimetallic catalysts, composition is usually difficult to control by traditional techniques, but by colloidal chemistry the relative portions of the metals in the nanoparticles can be exactly predefined. This approach offers the advantage of controlling structure and composition of the resulting particles. Preparation, conservation and protection of metallic or multimetallic nanoparticles require ?in most cases- protection with organic ligand molecules if they will remain in a colloidal suspension. When nanoparticles are made of gold or palladium, a relatively easy way of protecting them is through organic molecular self-assembly, particularly with thiol molecules due to the strong interaction between sulfur and gold/palladium atoms. Self-assembled monolayer?s (SAM?s) have been intensively studied, at experimental and theoretical levels on extended gold (111) surfaces and small Au clusters. In the present talk we show the application of a new semiempirical potential, recently developed in our Lab, to describe molecule-metal interfaces in a more realistic way. Using Density Functional calculations (DFT) in combination with the bond-order concept we have developed a new semiempirical framework which is simple and easy to implement in standard MD/MC codes. In particular we show the effect of soft and hard surfactants on the structure of gold nanoparticles of > 1nm. We have studied also the influence of two different capping agents (alkanethiols and alkyl amines) on the crystalline structure of the NPs, by means of aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), aberration-corrected scanning TEM (AC-STEM) and image simulations.