Direct coating for layered double hydroxide/4,4′-diaminostilbene-2, 2′-disulfonic acid nanocomposite with silica by seeded polymerization technique

Organic ultraviolet (UV) ray 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 by the human skin, an organic UV absorbent such as 4,4′-diaminostilbene-2,2′-disulfonic acid (DASDSA) was intercalated into Zn₂Al-layered double hydroxide (Zn₂Al-LDHs) by coprecipiation reaction. The problem of deintercalation of organic molecules from LDHs by the anion exchange reaction with carbonate ion could be greatly depressed by forming a protection film of silica on the surface. Zn₂Al-LDH/DASDSA was directly coated with silica by means of a polymerization technique based on the Stöber method. The deintercalation behavior as well as UV-shielding properties were investigated for coated particles.