Significance of postgrowth processing of ZnO nanostructures on antibacterial activity against gram-positive and gram-negative bacteria

Abstract

In this work, we highlighted the effect of surface modifications of one-dimensional (1D) ZnO nanostructures (NSs) grown by the vapor–solid mechanism on their antibacterial activity. Two sets of ZnO NSs were modified separately – one set was modified by annealing in an Ar environment, and the second set was modified in O 2 plasma. Annealing in Ar below 800°C resulted in a compressed lattice, which was due to removal of Zn interstitials and increased O vacancies. Annealing above 1,000°C caused the formation of a new prominent phase, Zn 2 SiO 4 . Plasma oxidation of the ZnO NSs caused an expansion in the lattice due to the removal of O vacancies and incorporation of excess O. Photoluminescence (PL) spectroscopy was employed for the quantification of defects associated with Zn and O in the as-grown and processed ZnO NS. Two distinct bands were observed, one in the ultraviolet (UV) region, due to interband transitions, and other in the visible region, due to defects associated with Zn and O. PL confirmed the surface modification of ZnO NS, as substantial decrease in intensities of visible band was observed. Antibacterial activity of the modified ZnO NSs demonstrated that the surface modifications by Ar annealing limited the antibacterial characteristics of ZnO NS against Staphylococcus aureus . However, ZnO NSs annealed at 1,000°C or higher showed a remarkable antibacterial activity against Escherichia coli . O 2 plasma–treated NS showed appreciable antibacterial activity against both E. coli and S. aureus . The minimum inhibition concentration was determined to be 0.5 mg/mL and 1 mg/mL for Ar-annealed and plasma-oxidized ZnO NS, respectively. It was thus proved that the O content at the surface of the ZnO NS was crucial to tune the antibacterial activity against both selected gram-negative ( E. coli ) and gram-positive ( S. aureus ) bacterial species.

Eco-friendly nanocomposites derived from geranium oil and zinc oxide in one step approach

“…Here, more desired functional groups are presented on the ZnO surface, which may modify its biological activity. Surface modifications of the ZnO NPs in oxidizing environments had been demonstrated to cause an important change in the antibacterial activity 69 , which can be utilized in biomaterials. For example, Galindo et al .…”

A Mini Review of Antibacterial Properties of ZnO Nanoparticles

“…The fifth method is modification by physio-chemical methods, for example, by annealing in the Ar environment at high temperatures, or plasma oxidation. With that, the effects of modification can be different: Ar annealing decreases the antibacterial activity of ZnO nanoparticles, while plasma oxidation improves antibacterial properties of ZnO nanoparticles against E. coli and S. aureus [120]. The sixth method is the use of additives causing photocatalysis of reactive oxygen species (ROS).…”

NanoZnO-modified titanium implants for enhanced anti-bacterial activity, osteogenesis and corrosion resistance

“…However, studies have suggested that electrostatic interactions are not the unique mechanism responsible for the antibacterial activity of nano-ZnO. The surface defects of nano-ZnO, such as corner defects, edge defects, and chemical defects, have a significant effect on the antibacterial activity that induces cell wall mechanical damage [ 113 , 114 ]. In the same way, the morphology of nano-ZnO also causes physical damage to bacteria [ 65 ].…”