Study of nucleation and growth mechanism of the metallic nanodumbbells

We propose a general nucleation and growth model that can explain the mechanism of the formation of CoPt 3/Au, FePt/Au, and Pt/Au nanodumbbells. Thus, we found that the nucleation event occurs as a result of reduction of Au + ions by partially oxidized surface Pt atoms. In cases when Au 3+ is used as a gold precursor, the surface of seeds should be terminated by ions (e.g., Co 2+, Pb 2+) that can reduce Au 3+ to Au + ions, which can further participate in the nucleation of gold domain. Further growth of gold domain is a result of reduction of both Au 3+ and Au + by HDA at the surface of gold nuclei. We explain the different ability of CoPt 3, Pt, and FePt seeds to serve as a nucleation center for the reduction of gold and further growth of dumbbells. We report that the efficiency and reproducibility of the formation of CoPt 3/Au, FePt/Au, and Pt/Au dumbbells can be optimized by the concentration and oxidation states of the surface ions on metallic nanocrystals used as seeds as well as by the type of the gold precursor. Fil: Krylova, Galyna. Argonne National Laboratory; Estados Unidos Fil: Giovanetti, Lisandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina