Segregation and color change on (Cr,Ca) codoped nanocrystalline tin dioxide

摘要

The intense violet color and the high catalyst activity of Cr-doped SnO2 nanoparticles have motivated several authors to understand the solid solution formation and the oxidation state of chromium ions after synthesis. Recent work has demonstrated the ability of surface segregation in chromium-doped tin oxide system but the oxidation state is still misunderstood. Calcium oxide addition changes the color of (Cr,Ca) codoped nanocrystalline tin dioxide pigments from violet to yellow simultaneously to a high particle size stabilization demonstrating that co-segregation could be associated to color change due to chemical environment change of chromium ions and specific surface area increase. High solubility of Cr~(+6) and Ca~(+2) allow us to determine the surface excess of both cations by ionic chromatography and the color change after surface solubilization.