Synthesis of nano-Fe 3 O 4 /ZnO composites with enhanced antibacterial properties and plant growth promotion via one-pot reaction

Bordeaux mixture is commonly used in agricultural production due to its certain antibacterial activity. However, it has been observed to promote plant growth at a slow pace. Therefore, it is crucial to explore an effective antibacterial agent that can enhance the antibacterial activity and promote plant growth in commercially available Bordeaux mixture, which can significantly contribute to the development of the agricultural economy. The investigation into inorganic agents with both bacteriostatic and plant-promoting properties has a broad application potential in agriculture. Fe 3 O 4 /ZnO (FZ) composites were synthesized from FeCl 3 , ZnCl 2 , and NaAc in a “one-pot approach” and analyzed using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and a vibrating sample magnetometer (VSM). To investigate the antibacterial activity and mechanism of FZ nanocomposites, Gram-negative Escherichia coli ( E. coli ) and Gram-positive Staphylococcus aureus ( S. aureus ) were used as model bacteria, and human mammary epithelial cells and model plant mung bean were used as targets to study the effects of FZ on human and plant growth. The results revealed that at 300 µg/mL for 80 min, the antibacterial efficacy of FZ composites was 99.8% against E. coli , which was 20% greater than that of Bordeaux liquid (FC), and 99.9% against S. aureus , which was 28.6% higher than that of FC. The inhibitory mechanism demonstrated that the substance could efficiently damage the bacterial cell wall of a concentration of 300 µg/mL. The IC 50 of the material to human mammary epithelial cells was 49.518 µg/mL, and it also increased mung bean germination, root growth, and chlorophyll content, indicating that the application performance was 1.5 times better than that of FC. Its exceptional performance can be used to treat agricultural diseases.