Nanospace-Confined High-Temperature Solid-State Reactions: Versatile Synthetic Route for High-Diversity Pool of Catalytic Nanocrystals

Abstract

The present study proposes a methodology to extend the utility of solid-state reactions to a synthetic route for producing a high-diversity pool of nanocrystals (NCs) by circumventing the problematic sintering of nanoparticles at high temperatures. For this purpose, nanometer-scale-confined NC formations/transformations were investigated using specifically designed SiO2 nanospheres with a radially differentiated core@shell structure as a reaction medium. The core of the SiO2 medium was modified by aminosilanes, thus providing binding sites for the metal ions and enabling pore creation through thermochemical treatment. This hindered the outward diffusion of fast-moving tiny species initially generated within the tens of nanometers-sized medium. The entire evolution process of Pd NCs during the high temperature reaction was confined within the SiO2 nanosphere, which transforms from the amine-containing nanosphere, Pd2+/SiO2(NH2), to a hollow nanosphere, Pd@h-SiO2. This nanoscale confinement strategy was app...