Asymmetric silica encapsulation toward colloidal Janus nanoparticles: a concave nanoreactor for template-synthesis of an electocatalytic hollow Pt nanodendrite

Abstract

A novel reverse microemulsion strategy was developed to asymmetrically encapsulate metal–oxide nanoparticles in silica by exploiting the self-catalytic growth of aminosilane-containing silica at a single surface site. This strategy produced various colloidal Janus nanoparticles, including Au/Fe₃O₄@asy-SiO₂, which were converted to an Au-containing silica nanosphere, Au@con-SiO₂, by reductive Fe₃O₄ dissolution. The use of Au@con-SiO₂ as a metal-growing nanoreactor allowed the templated synthesis of various noble-metal nanocrystals, including a hollow dendritic Pt nanoshell which exhibits significantly better electrocatalytic activities for the oxygen reduction reaction than commercial Pt/C catalysts.