Preparation of Co₃O₄ Nanoparticles in a Lyotropic Liquid Crystal Medium and Their Application in Anti-bacterial, Anti-cancer and Catalytic Activities

Preparation of Co₃O₄ nanoparticles (NPs) via a chemical reduction method at room temperature in a lyotropic liquid crystal (LLC) medium is described. A mixture of triton X-100 and water in the ratio 2.1:2.9 (wt%) exhibited LLC having a hexagonal structure in the temperature range of 25–29 °C. The NPs were prepared in this medium by reducing cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) using sodium borohydride (NaBH₄) resulting in nearly spherical particles having a size of ∼ 100 nm. The LLC medium facilitated a controlled growth of the NPs and also provided stabilization for the NPs by preventing their aggregation. The anti-bacterial activity of the particles indicated a significant activity towards gram-negative bacteria. Anticancer activity against breast cancer cell line MCF-7 showed an impressive IC₅₀ value of 30.8 µg/mL. Additionally, the efficiency of the Co₃O₄ NPs as catalyst for the reduction of 4-nitrophenol and degradation of a dye named methylene blue was evaluated; the apparent rate constant values calculated for these reactions were 1.8 × 10⁻² min⁻¹ and 3.1 × 10⁻² min⁻¹ respectively. Besides, particles displayed efficient activity till 5^th cycle.