Room-Temperature Synthesis of Ag-Ni and Pd-Ni Alloy Nanoparticles

Ni-based alloy nanoparticles (NPs) are synthesized using room-temperature radiolysis. Density functional theory (DFT) and various nanoscale characterization methods are used to provide a strong basis for understanding and describing metastable phase regimes of alloy NPs whose reaction formation is determined by kinetic rather than thermodynamic reaction processes. Two series of nickel alloyed NPs, Ag-Ni and Pd-Ni, are analyzed and characterized via various analytical characterization techniques. Different ratios of Ag(x)-Ni(1-x) alloy NPs and Pd(0.5)-Ni(0.5) alloy NPs are prepared using a high gamma irradiation dose rate. Images from high-angle annular dark-field show that the Ag-Ni NPs are not in a core-shell configuration but, rather, a homogeneous alloy structure. Energy filtered transmission electron microscopy maps further elucidate the homogeneity of the metals in each alloy NP. Of particular interest are the normally immiscible Ag-Ni NPs that have been shown to form core-shell structures in thermodynamically driven reactions. All evidence supports that homogeneous Ag-Ni and Pd-Ni alloy NPs are successfully synthesized by a high dose rate radiolytic methodology. DFT modeling is used to support that nanoparticle alloying proceeds through the less energetically favorable path of formation, achievable via high dose rate radiolysis.