Synthesis of zinc oxide nanocrystalline powders for cosmetic applications

The synthesis of zinc oxide (ZnO) nanocrystalline powders for cosmetic applications by a coprecipitation process has been investigated. When the Zn(OH)2 precipitates are calcined at 373 K for 10 min, the crystalline phases comprise the major phase of Zn(OH)2 and the minor phase of ZnO. XRD pattern shows that only ZnO is present and no other phase is detected when the Zn(OH)2 precipitates calcined at 413 K for 10 min. The nanocrystallite size of ZnO increases slightly from 32.3 to 44.3 nm when the calcination temperature increases from 413 to 873 K. The activation energy of ZnO nanocrystallite growth is 2.02 kJ/mol, which reveals that the nanocrystalline ZnO is easily grown at low temperature. The UV transmission of ZnO nanocrystallites in the wavelength range from 290 to 375 nm is about 35%, indicating that the ZnO nanocrystallites have an excellent UV-absorbing capability.