Preparation and anti-ultraviolet properties of vermiculite-supported zinc-titanium layered double hydroxide composites.

Excessive ultraviolet (UV) radiation exposure carries severe hazards to human health, creating an urgent demand for high-performance UV absorbers. Herein, vermiculite (VMT)-supported zinc-titanium layered double hydroxides (ZnTi-LDHs) were prepared. Five types of VMT-based organic-inorganic UV-absorbing composites were further constructed via intercalation assembly by introducing organic UV absorbers during the in situ growth of ZnTi-LDHs on VMT. The chemical structure, micromorphology, and UV-shielding capacity of the as-prepared materials were systematically characterized. The results reveal that bare ZnTi-LDHs display microspherical morphology with diameters of 1-3 µm, and feature porous frameworks with heterogeneous pore sizes, mainly distributed at 1.07 µm. Furthermore, ZnTi-LDHs are positively charged with a potential of +33.2 mV. For the five VMT-based organic-inorganic composites, ZnTi-LDH nanosheets grow perpendicularly onto VMT lamellae, yielding a compact, homogeneous three-dimensional network. When used as functional additives in sunscreen formulations, these composites exhibit outstanding UV absorption capability. UV-vis spectroscopic measurements record a maximum absorbance of 2.74. In ex vivo UV exposure assays using porcine skin, the sunscreen prolonged the onset of obvious skin discoloration to 380 min. Hydrophobicity tests also verify that all five sunscreen formulations possess hydrophobic characteristics. Collectively, these results demonstrate that the as-synthesized composites are highly promising candidates for cosmetic applications.