Nanostructured Zn-Ti layered double hydroxides with reduced photocatalytic activity for sunscreen application
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The harmful effects of long-term UV exposure on human skin are increasingly understood these days, and therefore, the use of topical sunscreen products containing UV filters has significantly increased. Although the currently used organic and inorganic UV filters are effective UV absorbers, they may cause several problems such as high photoreactivity, photodegradation, and generation of reactive oxygen species leading to serious skin damages including skin cancer. Therefore, the development of safer, skin-compatible, photostable, and more effective photoactive ingredients is critical. In this study, a Zn-Ti layered double hydroxide (Zn-Ti LDH) was prepared using a hydrothermal method, and its properties as a sunscreen additive were evaluated and compared to those of nano-TiO2 and nano-ZnO. Physical characterization confirmed the formation of a highly stable crystalline LDH structure. Scanning electron microscopy analysis revealed the formation of two-dimensional nano-flakes and layered structure. The optical properties of Zn-Ti LDH analyzed by diffuse reflectance UV-Vis showed higher UV reflection properties and lower absorption properties in comparison to TiO2 and ZnO. Zn-Ti LDH exhibited substantially lower levels of photocatalytic activity towards the degradation of methylene blue at both 365 nm and 254 nm which indicates increased safety of Zn-Ti LDHs for use as UV filters in topical sunscreen applications.
KeywordsZn-Ti LDH Synthesis Characterization Optical and photochemical properties Nanostructured catalysts
We would like to acknowledge the help of Ms. Louise Mostert at the National Metrology Institute of South Africa (NMISA) for her XPS expertise. We acknowledge the assistance of Ms. Dina Oosthuizen for the DRUV-Vis analyses done at the University of Free State.
This work was supported by the National Research Foundation (Grant No. 100849) and Council for Scientific and Industrial Research (National Centre for Nanostructured Materials), Project HGER70P.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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