Application of ZnAl layered double hydroxides for the formulation of stable and safe cosmetic pigments

PurposeThis study aims to produce composite pigments, including SHS/ZnAl-LDHs, IDS/ZnAl-LDHs and SNND/ZnAl-LDHs, with improved coloration, enhanced photostability and thermostability and biocompatibility.Design/methodology/approachThe chemical structures of the composite pigments were characterized by X-ray diffraction spectroscopy and Fourier transform infrared spectroscopy. Photostability and thermal stability were assessed using ultraviolet-visible spectroscopy and colorimetry. The coverage of the dyes was determined through black-and-white tile testing, and specific RGB values were used to indicate color expressiveness. Finally, a four-color eyeshadow was formulated, and safety tests were conducted via human patch test and cellular assays to confirm the safety and reliability of the samples.FindingsThe experimental results demonstrate an enhancement in the photo and thermal stability of the SHS/ZnAl-LDHs, IDS/ZnAl-LDHs and SNND/ZnAl-LDHs composites, along with their superior performance in terms of covering power and color saturation. These composite pigments also exhibit high safety, making them well-suited for cosmetic applications.Practical implicationsThe composite pigments based on hydrotalcite can be used in the cosmetic industry without causing any harm to the environment and human health.Originality/valueThe addition of hydrotalcite enables better application of pigments in cosmetics.