Cobalt ferrite nanoparticles supported on reduced graphene oxide sheets: optical, magnetic and magneto-antibacterial studies

The development of antibacterial nanomaterials has emerged as a strategy to control bacterial activity, due to the growth and spread of antibiotic-resistant pathogen microorganisms. Graphene-based nanocarbons, as one of the most attractive materials, given their extraordinary physical and chemical properties, are promising candidate nanomaterials for biomedical applications. In this study, cobalt ferrite nanoparticles (NPs) supported on reduced graphene oxide (rGO) sheets to form metal nanocomposites (MNCs) known as CoFe₂O₄@rGO MNCs with different rGO contents (0, 10, 25 and 40 wt%) have been synthesized by a one-step process. The structures, morphology, optical, magnetic and antibacterial properties of the CoFe₂O₄@rGO were investigated by x-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy images, Raman, Fourier transform infrared (FTIR) and UV-Vis spectroscopies, vibration sample magnetometry and antibacterial tests as a function of rGO content. The particle sizes of the CoFe₂O₄ NPs supported on the different rGO contents were below 10 nm. The band gap energy of the samples decreased from about 3.1 to 1.7 eV with reducing rGO content. The results prove the effective reduction of graphene oxide to rGO and also the support of CoFe₂O₄ on rGO sheets by a one-step hydrothermal reaction. The increase in rGO content in the samples reduced their saturated magnetization from about 15 to 7 emu g^-1. The CoFe₂O₄@rGO MNCs have shown magneto-antibacterial activity against gram-negative bacteria (Escherichia coli), whose efficacy depends on the value of the rGO content. In contrast, the CoFe₂O₄@rGO MNC (25 wt% rGO) which was synthesized by the one-step hydrothermal method not only has a narrow band gap energy (for photocatalytic applications), but also significant magneto-antibacterial activity was observed.