Advanced bimetallic In–Cu/Ag/Au nanostructures via microemulsion-based reaction

Abstract

Bimetallic nanomaterials and nanostructures constituted of the coinage metals (Cu, Ag, Au) and indium with elaborate compositions and structures are realized via a microemulsion-based approach. In detail, this comprises Cu11In9@CuIn@In core@shell-A@shell-B nanoparticles, In-Ag Janushead-like nanoparticles, Ag0 hollow spheres, Ag3In@In core@shell nanoparticles, Au@AuIn2@In core@shell-A@shell-B nanoparticles and AuIn2 nanoparticles. To obtain these advanced architectures, two approaches are applied: (1) In0 nanoparticles—pre-synthesized in a microemulsion—were reacted in a follow-up reaction with CuCl2·2H2O, AgNO3 or KAuCl4; (2) simultaneous co-reduction of InCl3·4H2O together with CuCl2·2H2O, AgNO3 or KAuCl4 in a microemulsion. Characterization of the resulting advanced structures and compositions requires elaborate electron microscopy techniques, combined with energy dispersive X-ray spectroscopy for chemical analyses of single nanoparticles as well as X-ray powder diffraction and optical spectroscopy. The versatility of the experimental approach toward complex nanoparticle architectures is related to a precise control and fine-tuning of the experimental conditions. The resulting tool kit of In–Cu/In–Ag/In–Au-based bimetallic and intermetallic nanomaterials and, in general, of nanostructured metal architectures with such variability and complexity have not yet been described.