Formation of uniform TiO₂ nanoshell on α-alumina nanoplates for effective metallic luster pigments

To synthesize non-corroding effect pigment appearing metallic silver in color, we coated uniform anatase TiO₂ nanoshell via sol-gel chemistry. Under the reaction condition using 3M TiCl₄ aqueous solution: deionized water: HCl solution=0.75mL: 20 mL: 0 mL, ∼50 nm-thick smooth TiO₂ nano-shell was fully coated on the surface of α-alumina nanoplates; consequently, the synthesized effect pigments exhibited similar lustering effect and structuring color to commercial effect pigment. Under relatively acidic condition and higher TiCl₄ precursor concentration condition (3 M TiCl₄ aqueous solution: deionized water:HCl solution=0.75mL: 20 mL: 0.05mL for acidic condition and 1.0 or 1.5mL: 20 mL: 0 mL for higher TiCl₄ precursor concentration condition), rougher TiO₂ shell was formed.