Synthesis of binary metal–metal oxide core‐shell nanoparticles via surfactant‐free intercation redox reactions

Surfactant‐free one‐step redox reactions between two types of metal cations enable the synthesis of core‐shell nanoparticles without sophisticated control. The reduced noble metal cations form a solid core, and the transition metal cations dissolved upon oxidation induce the subsequent formation of a metal oxide shell. Various nanostructures are obtained from the combination of reduction‐preferring Au3+, Pd2+, Pt2+, Rh3+, and Ir3+ cations, and oxidation‐preferring Ti3+, Mo3+, V2+, and V3+ cations. Among the synthesized core‐shell nanoparticles, Au–M (M = Ti, Mo, and V) is selected for the photodegradation tests at 365 and 808 nm. The spontaneous redox reaction between the two transition metal cations enabled the formation of core‐shell nanoparticles. This approach, called the intercation redox reaction, does not require any additional substances, including surfactants or reducing agents. The composite structure of the synthesized metal‐core metal oxide shell has the potential for a variety of additional applications.