Interface evolution in the platelet-like SiC@C and SiC@SiO₂ monocrystal nanocapsules

Carbon-coated SiC@C nanocapsules (NCs) with a hexagonal platelet-like morphology were fabricated by a simple direct current (DC) arc-discharge plasma method. The SiC@C NCs were monocrystalline, 120–150 nm in size, and approximately 50 nm thick. The formation of the as-prepared SiC@C NCs included nucleation of truncated octahedral SiC seeds and subsequent anisotropic growth of the seeds into hexagonal nanoplatelets in a carbon-rich atmosphere. The disordered carbon layers on the SiC@C NCs were converted into SiO₂ shells of SiC@SiO₂ NCs by heat treatment at 650 ℃ in air, during which the shape and inherent characteristics of the crystalline SiC core were obtained. The interface evolution from carbon to SiO₂ shells endowed the SiC@SiO₂ NCs with enhanced photocatalytic activity due to the hydrophilic and transparent nature of the SiO₂ shell, as well as to the photosensitive SiC nanocrystals. The band gap of the nanostructured SiC core was determined to be 2.70 eV. The SiC@SiO₂ NCs degraded approximately 95% of methylene blue in 160 min under visible light irradiation.