Formation of silver single crystal polyhedra with high catalytic activity toward oxidation of ascorbic acid in highly ordered SiO2 cavities

Two-dimensional array of SiO2 cavities is fabricated on an indium-doped tin oxide (ITO) electrode by using highly ordered self-assembly of polystyrene spheres as a template. Silver nanoparticles electrodeposited at the bottom of the SiO2 cavities are fused and recrystallized via aggregative and Ostwald ripening mechanisms under annealing treatment conditions. Due to the confinement effect of the SiO2 cavity, the vaporized silver atoms preferentially deposit on the surface of the relative large silver particles at near equilibrium state, leading to the formation of silver single crystal polyhedron dominated with (111) facets in each SiO2 cavity, which can functionalize as a nanoelectrode and exhibit excellent electrocatalytic activity toward oxidation of ascorbic acid. Based on the array of the silver single crystal polyhedra, an electrochemical sensing platform of ascorbic acid is developed with high sensitivity and rapid response.