Materials Chemistry and Physics, Vol.89, No.1, 154-158, 2005
Silica coating of Zn2Al/4-hydroxy-3-methoxybenzoic acid nanocomposites via seeded polymerization technique
Organic ultraviolet (UV) rays absorbents have been used as sunscreen materials, but may pose a safety problem when used at high concentration. In order to prevent direct contact of organic UV-rays absorbent to the human skin a typical organic UV-absorbent, 4-hydroxy3-methoxybenzoic acid (HMBA) was intercalated into Zn2Al layered double hydroxide (Zn2Al-LDHs) by coprecipiation reaction. But deintercalation of organic molecules from Zn2Al-LDHs, by the anion exchange reaction with carbonate ion, was observed. Therefore, Zn(2)AILDH/4-hydroxy-3-methoxybenzoic acid is directly coated with silica by means of polymerization technique based on the Stober method. Silica coating effectively depress the deintercalation of 4-hydroxy-3-methoxybenzoic acid from Zn(2)AI-LDHs. The amorphous silica is confirmed by X-ray diffraction, scanning electron microscope and FT-IR. The deintercalation behavior as well as UV-shielding properties is investigated for coated particles. (C) 2004 Elsevier B.V. All rights reserved.