Colloidal gold-palladium-platinum alloy nanospheres with tunable compositions and defined numbers of atoms

The combination of different metals into a discrete colloidal nanocrystal (NC) lattice to form solid solutions can result in synergetic and non-additive effects, leading to physicochemical properties distinct from those observed in monometallic NCs. However, these features are influenced by parameters that are challenging to control simultaneously using conventional synthesis methods, including composition, morphology, size, and elemental distribution. In this study, we present a methodology that exploits seed-mediated growth routes and pulsed laser-induced ultrafast heating to synthesize bimetallic and trimetallic colloidal alloy NCs with tailored compositions, well-defined spherical morphologies, and precise control over the number of atoms per NC lattice. Initially, core-shell heterostructures with adjustable compositions and ca. 10⁷ atoms per NC are formed, using Au as the core material and Pd and Pt as the shell metals. In the subsequent stage, ultrafast heating of the heterostructure lattice via nanosecond pulsed laser irradiation facilitates the formation of colloidal AuPd, AuPt and AuPdPt alloy nanospheres. The ability of the proposed synthesis route to produce multimetallic NCs with distinct compositions, consistent morphology, and a fixed number of atoms provides exciting opportunities to investigate how multimetallic NC composition influences catalytic properties. Accordingly, using the catalytic reduction of nitrophenol as a reaction model, we observed a significantly enhanced catalytic performance for AuPdPt NCs compared to AuPd and AuPt NCs.