Preparation of NiO Nanosheets in a Lyotropic Liquid Crystal Medium and Their Application in Catalytic, Anti-Cancer and Anti-Bacterial Activities

Herein, we report the preparation of nickel oxide (NiO) nanosheets in a lyotropic liquid crystal (LLC) medium via a chemical reduction method. The LLC phase exhibiting a lamellar phase was formed using a binary mixture of triton X-100 (68 wt%) and water (32 wt%) at 4 °C. The nanomaterials were prepared in this medium by reducing NiCl₂.6H₂O using a strong reducing agent, NaBH₄. The prepared nanomaterials were characterized through UV–Vis, SEM, FT-IR and XPS techniques. The NiO nanomaterials were found to exhibit good catalytic activity towards reduction and degradation reactions. An apparent rate constant (K_app) value of 1.4 × 10^–2 min⁻¹ was obtained for the reduction reaction of 4-nitrophenol to 4-aminophenol using NiO nanomaterials (300 μL of as-prepared 80 mM dispersion). The nanomaterials showed good recyclability with effective activity until 5^th cycle. Further, K_app of 0.5 × 10^–2 min⁻¹ was obtained for the degradation reaction of methylene blue. The anti-bacterial studies suggested that the NiO nanomaterials were effective against gram positive (S. aureus) bacteria and anti-cancer studies of the particles against breast cancer cells (MCF-7) showed an IC₅₀ value of 78.93 μg/mL.