Mn3O4 was synthesized by a co-precipitation method. 0.22 M of manganese chloride tetrahydrate (MnCl2.4H2O) along with 1.37 mM hexadecyl trimethyl-ammonium bromide (CTAB) was stirred constantly. 0.44 M sodium hydroxide (NaOH) solution was prepared separately and added dropwise to the first solution and was kept under constant stirring for 24 hours. The final precipitate was filtered and washed with DI water and then ethanol for several times. The material was dried in the oven at 80°C overnight.