Synthesis and Color Evolution of Silica‐Coated Hematite Nanoparticles

The aim of this communication is to investigate the color evolution of silica-coated hematite nanoparticles versus treating temperature. The silica-coated hematite nanoparticles were prepared by first suspending commercial hematite nanoparticles in an ammonia–water–2-propanol system, and then depositing amorphous nano-SiO2 onto the surface of hematite nanoparticles using the Stober method. The silica-coated nanoparticles were dripped onto biscuits and heat treated at various temperatures. The color changes of heat treated samples were determined by the CIE L*a*b* parameters, and the possible mechanism of color evolution was discussed.