Preparation and Anti-microbial Performance of Ni0.5Zn0.5Fe2O4@Ag Nanocomposites

Abstract

Pathogens are harmful to humans and can lead to death in severe cases. Silver nanoparticles are considered to be the most effective antibacterial materials. Therefore, the magnetic NZFO@Ag-R nanocomposites were prepared by the reduction method with magnetic Ni0.5Zn0.5Fe2O4 nanoparticles, silver nitrate, and sodium citrate as raw materials. The antibacterial performances of the materials were evaluated by the growth curve, the inhibition zone test, the minimum inhibitory concentration (MIC) test, and the minimum bactericidal concentration (MBC) test with E. coli and S. aureus as the bacterial source. The XRD, SEM, and VSM characterization results showed that the magnetic NZFO@Ag-40% nanocomposites had a spherical morphology with an average size of 23 nm. The Ag loaded had a cubic crystal structure and evenly mixed with NZFO. The mass fraction of silver was 31.34%. The saturation magnetization decreased from 63.7 emu/g to 31.6 emu/g with the increase of Ag content. The antibacterial circle test and growth curve test explained that NZFO nanoparticles had almost no antibacterial properties. When the Ag content reached 40%, the radius of the antibacterial circle was the largest and the inhibition effect of the growth curve was the most obvious. When the content raised to 50%, the antibacterial activity was not significantly enhanced. The MIC and MBC of the magnetic NZFO@Ag-40% nanocomposites for E. coli were 5 µg/mL. The MIC and MBC for S. aureus were 5 µg/mL and 10 µg/mL, respectively. The possible mechanism was proposed for the improved antibacterial activity of NZFO@Ag-R nanocomposites. NZFO@Ag-R nanocomposites were prepared for the first time and applied to the antibacterial field. The antibacterial activity was strongest when the Ag content reached 40%. Antibacterial capability test showed that NZFO@Ag-40% nanocomposite had strong antibacterial properties against both E. coli-gram-negative bacteria and S. aureus-gram-positive bacteria. The DNA damage caused by the accumulation of nanoparticles on the membrane by Ag+ and the reaction of macromolecular substances with reactive oxygen species was the main reason for the antibacterial activity of the composite materials.