Statistical Mechanical analysis of the electrochemical stability of nanoparticles

E.P.M. LEIVA

Cancun

Conferencia; Symposium at the XIX Material Reasearch Congress; 2010

MRS

The special properties of nanocrystals have awaked great interest in both scientific and technological communities, and the size dependence of their thermodynamic properties has been topic of intensive research in recent years. A great number of techniques, including chemical, electrical, and physical processes, have been employed for the preparation of NP[1,2]. Syntheses through simple wet-chemical methods are particularly favored for the cost-effective and large-scale production of such nanostructures. In particular most of the wet-chemical methods consist of the reduction of a metal salt precursor solution in the presence of a stabilizing reagent. The main advantage of electrochemical methods is that they allow precise adjustment of the supersaturation conditions at the interface, via control of the deposition potential. Potential adjustment can be achieved by means of straightforward potentiostatic control of an electrode or alternatively by the proper choice of a redox couple. In the case of the electrochemical synthesis of nanoparticles, the redox potential plays a very important role, since it allows the control of the chemical potential of the metal constituting the nanoparticle. In this respect, Plieth[3] found a shift of the reversible redox potential with nanoparticle size that was explained using an expression analogous to Kelvin equation, thus predicting that these changes are inversely proportional to the radius of the NP. Besides pure metallic nanoparticles, the preparation of bimetallic NP is also of interest to both basic and applied science because they exhibit characteristic electronic, optical, and catalytic properties that differ from those of their individual constituent metallic. For theses systems, also a wealth of preparation methods have been developed, but a complete theoretical framework to understand their stability is still lacking. In the present talk, we summarize the statistical mechanic features of a new model devoted to understand the electrochemical stability of pure and bimetallic metal nanoparticles, and perform an analysis of electrochemical metal deposition on a NP used as a seed. The present model is based on the work of Hill and Chamberlin[4] devoted to the description of metastable states.