Bimetallic nanoparticles via microemulsions: The effects of concentration in surface composition

The precise control of surface composition is crucial for enhancing the efficiency of bimetallic nanocatalysts. The scarcity and contradictory nature of experimental results keep open the question of whether reactant concentration promotes the enrichment of the nanoparticle surface with the slower reduction metal. A computer simulation study is carried out to thoroughly investigate how the initial concentration of metals salts modifies the resulting surface for various metal pairs and under different microemulsion compositions. Across all cases, it was observed that less Au is located at the surface as concentration increases. The resulting surface compositions are explained based on the relative rates of the two metals, which consider not only the reduction rate of particular metal pair but also factors such as the concentration of reactants, the intermicellar exchange rate, and the contribution of ripening to growth. This study provides a comprehensive understanding of the mechanism of nanoparticle formation in microemulsions and enables the proposal of practical guidelines for obtaining bimetallic nanoparticles with customized surfaces.