Preparation of Co3O4 nanoparticles in a lyotropic liquid crystal medium and their application in anti-bacterial, anti-cancer and catalytic activities

Preparation of Co 3 O 4 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 25-29°C. The NPs were prepared in this medium by reducing cobalt(II) chloride hexahydrate (CoCl 2 .6H 2 O) using sodium borohydride (NaBH 4 ) resulting in nearly spherical particles having a size of ∼ 100nm. 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 IC 50 value of 30.8 µg/mL. Additionally, the efficiency of the Co 3 O 4 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.