ZnFe2O4 and CuFe2O4 Nanocrystals: Synthesis, Characterization, and Bactericidal Application

An easy mechanochemical and eco-friendly method was employed to obtain nanocrystals with an average size of about 9 nm of zinc ferrite (ZnFe 2 O 4 ) and copper ferrite (CuFe 2 O 4 ). Their corresponding X-ray diffraction (XRD) patterns reveal a cubic crystal structure for ZnFe 2 O 4 , whereas in CuFe 2 O 4 the tetragonal and cubic crystal phases coexist, the latter being the majority phase. The transmission electron microscopy (TEM) images of these nano ferrites corroborate the formation of nanocrystals with dimensions consistent with those obtained from the XRD patterns. Furthermore, their corresponding Raman spectra confirm the structure and composition of nano ferrites. In addition, both nano ferrites show an electron paramagnetic resonance (EPR) spectrum with a wide band with g ~ 2.0, characteristic of ferromagnetic oxides. Besides, the antibacterial effect of ZnFe 2 O 4 and CuFe 2 O 4 nanocrystals against two opportunistic pathogens, Staphylococcus epidermidis (ATCC 14,990) and Pseudomonas aeruginosa (ATCC 43,636), was tested. The minimum bactericidal concentration (MBC) results showed that ZnFe 2 O 4 was more effective against S. epidermidis , while CuFe 2 O 4 was for P. aeruginosa . On the other hand, when 27 mg/mL of nano ferrites were dispersed in the agar plates, the growth of S . epidermidis was 100% inhibited, whereas ZnFe 2 O 4 and CuFe 2 O 4 inhibited 67% and 78% of P. aeruginosa growth, respectively.