Synthesis and characterization of coated cerium phosphates with organic compounds

Full text: Ultraviolet radiation (UV), depending on the intensity and exposure time, may cause damage to health, thus the use of UV protection filters is necessary to avoid these damages. According to researchers, the cerium phosphate (CePO₄) has a great potential to replace the actual UV protection filters, due to your low photo catalytic activity and high absorptivity in the UV region1. However, the CePO₄ in a formulation has not a good dispersion, because they aggregate leading to an inefficient filter. Thus, to improve the dispersibility of CePO₄ in a formulation, the nanoparticles may be coated, once the surface can be considerable changed, resulting in an improvement of the UV filter. Following this concept, synthesis of CePO₄ along with oleic acid (OA) were performed in order to coat it with these organic compound. The coated phosphate were synthesized in ethanolic medium, in open and closed (reflux) system. In these syntheses was used dihydrogen ammonium phosphate ((NH₄)H₂PO₄), cerium nitrate (Ce(NO₃)₃.xH₂ O) and oleic acid. Stable suspensions containing CePO₄ coated with OA were obtained. The IR spectra and XRD patterns showed the formation of cerium orthophosphate. Through the light scattering analyzes, a good dispersion of the material was observed. SEM showed that the nanoparticles have the size and morphology dependent on the synthesis methodology. Lastly, through the diffuse reflectance spectrum was noticed a good absorptivity of the materials in the UV region. The obtained results indicate that the coated formation of CePO₄ is better dispersed in cosmetic formulation without losing the characteristic of being an excellent UV filters. Reference: Lima, J. F.; Serra, O. A. Cerium Phosphate Nanoparticles with Low Photocatalytic Activity for UV Light Absorption Application in Photoprotection. Dyes and Pigments 97 291-296 (2013). (author)