Preparation and characterization of dye-intercalated Zn–Al-layered double hydroxide and its surface modification by silica coating

The new organic–inorganic hybrid pigments have been prepared via the direct co-precipitation method involving the simultaneous formation of the inorganic layers of Zn–Al (3:1) the layered double hydroxide (LDH) and intercalation of the anionic dye species. Intercalation of bulky colored organic anions into Zn/Al LDH caused the interlayer spacing of LDH to increase from 4.8 to 18.7–24.3 Å. Intercalation compounds have high optical selectivity and purity due to the spatial confinement. In this study, the shape of hybrid material was controlled by the synthetic method and the shape of anion dye. Then they were subsequently surrounded by homogeneous silica shell by the coating procedure containing hydrolysis of tetraethyl orthosilicate (TEOS). The acid treatment for the above silica-coated particles led to the selective removal of Zn–Al hydroxide inorganic lattices, resulting in the low-density hybrid pigment of molecular dyes encapsulated in silica hollow sphere.