ZnO-Cu/NiFe2O4 magnetic nanocomposite with boosted photocatalytic and antibacterial activity against E. coli.

Abstract

A novel ZnO-Cu/NiFe2O4 hybrid nanocomposite with increased photocatalytic and antibacterial activities was synthesized by solid-state mixing of NiFe2O4 with Cu-doped ZnO (ZnO-Cu) and subsequent thermal processing. Various characterization techniques, like X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), Raman spectroscopy, vibrating-sample magnetometry (VSM) and Brunauer-Emmett-Teller (BET) analysis, have been used to study and characterize the synthesized nanomaterial. The XRD results demonstrated a hexagonal wurtzite phase of the ZnO nanoparticles and a reduction in the average crystallite size with doping and composite formation. The average crystallite size was found to be 32.36 ± 0.25 nm for ZnO, 29.87 ± 0.28 nm for ZnO-Cu and 24.73 ± 0.21 nm for the ZnO-Cu/NiFe2O4 nanocomposite. FESEM analysis revealed that the synthesized nanoparticles possess a nearly spherical morphology and average particle sizes of about 89 ± 1.8, 78 ± 1.9 and 63 ± 1.6 nm for the ZnO, ZnO-Cu and ZnO-Cu/NiFe2O4 samples, respectively. ZnO and ZnO-Cu/NiFe2O4 nanocomposite exhibit specific surface area of 6.67 and 12.38 m2/g, respectively, as observed from BET analysis. FTIR analysis indicated the enhancement of carboxylate and hydroxyl groups with doping and nanocomposite formation. The retentivity (Mr ∼ 0.243 emu/g), coercivity (Hc∼ 98.1 Oe) and saturation magnetization (Ms∼ 3.048 emu/g) values of the ZnO-Cu/NiFe2O4 nanocomposite, obtained from VSM analysis, confirm its superparamagnetic characteristics. To comprehend the photocatalytic activity of the prepared nanocomposite, dye degradation was also investigated. Here, we have shown that the ZnO-Cu/NiFe2O4 nanocomposite is capable of achieving the highest photocatalytic activity of 94.2% compared to ZnO (56.2%) and ZnO-Cu (86.4%). The antibacterial activity on Escherichia coli (E. coli) was investigated and the observed zones of inhibition for ZnO, ZnO-Cu and the ZnO-Cu/NiFe2O4 nanocomposite were 20.1 ± 0.21, 20.9 ± 0.20 and 27.3 ± 0.24 mm, respectively. Assuming the antibacterial activity of control ampicillin as 100%, the ZnO-Cu/NiFe2O4 nanocomposite has shown the maximum antibacterial activity of 107.5 ± 0.94% as compared to the other samples. According to our observations, the ZnO-Cu/NiFe2O4 hybrid nanocomposite exhibits the highest level of inhibition among all the samples and has the potential to be used in various environmental, biological and industrial applications.