Template free synthesis of CuO nanoflakes and walnut shape CuO/CeO2 heterostructures: characterization and their role as an antibacterial materials and biofilm inhibitors

To prevent the worldwide diseases caused by the micro-organisms, the great effort has been performed to synthesize unique CuO nanoflakes (NF) and walnut shape (W-S) CuO/CeO₂ heterostructures with O vacancies by a simple precipitation technique without using any template. The morphology, structure, valance states, chemical composition and surface charge of the synthesized samples were inspected by i.e. scanning electron microscope (SEM), energy dispersive X-Ray (EDX), resolution transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential (ζ). The expected crystallite’s size was studied by XRD data i.e. for CuO NF ~5.9 nm with 0.1–0.2% error and SD is ±0.2–0.5, while for the W-S CuO/CeO₂ heterostructures it is about ~6.4 nm with 0.05–0.1% error and SD is ±0.1–0.2 respectively. Both samples were tested as an antiseptic agent against E. coli and S. aureus, and it was confirmed that they had greater antibacterial effects as compared to the control group (water) which showed no response (0%). It was predicted that the CuO/CeO₂ heterostructure showed excellent antibacterial activity (100%) verses pure CuO NF (80–90%) at the same 0.2 mg/L concentration for E. coli with SD (±0–1). While against S. Aureus strain the CuO/CeO₂ heterostructure showed (80–90%) antibacterial action at the lowest concentration (0.2 mg/L) but 100% as the concentration increases i.e. 0.5 mg/L due to difference in bacterial strain with the SD (±0–2). After remarkable antibacterial activity, the biofilm inhibition of CuO/CeO₂ heterostructure against S. aureus was also studied by crystal violet staining, and examined that the inhibition effect of the biofilm increases with the increase concentration of heterostructures. At 0.31 mg/mL, the biofilm reduced visibly and the whole structure has destroyed, indicating that it is a remarkable biofilm inhibitor.

Graphical Abstract