Synthesis of nano-hematite for possible use in sunscreens

Hematite nanoparticles were synthesized for ultraviolet filtration application by the precipitation method followed by calcination at different temperatures. A range of crystallite sizes between 37 and 85 nm (as determined by the Scherrer formula) was obtained, according to the temperature used for the calcination. An increase in the absorbance with increasing crystallite size was observed over the whole ultraviolet B and A range. The experimental band gap was 2.94 eV for the sample calcined at 500 degrees C and 3.08 eV for the sample calcined at 300 degrees C. The in vitro sun protection factor and protection factor-ultraviolet A of a water-in-oil emulsion made with the sample calcined at 500 degrees C as active ingredient were 9.21 and 8.81, respectively, which is higher than the protection factor-ultraviolet A values obtained for titanium dioxide and zinc oxide at the same mass concentration. The emulsion was found to be photostable

Cerium oxide based particles as possible alternative to ZnO in sunscreens: Effect of the synthesis method on the photoprotection results

The aim of this study was to synthesize and characterize Ca-doped CeO2 nanopowder in order to determine in vitro the photoprotection efficiency of the combination – commercial TiO2/Ca-doped CeO2 – incorporated in emulsion. Cerium based particles were synthesized by two methods, co-precipitation and spray pyrolysis, in order to study the effect of the synthesis method on the photoprotection results. While both samples synthesized by co-precipitation and spray pyrolysis methods present the same crystalline structure and the same elementary composition, they differ in granulometry. The photoprotection results showed that the combinations tested are more efficient than the classical combination TiO2/ZnO in both UVB and UVA ranges. While the combination TiO2/CeO2 synthesized by co-precipitation allows an increase of the SPF of 27% compared to the classical combination, the combination TiO2/CeO2 synthesized by spray pyrolysis allows an increase of the PF-UVA of 19%