Sonochemical fabrication of gradient antibacterial materials based on Cu-Zn alloy

Abstract

At present research, we highlight ultrasonic treatment as a new way to create materials with a gradient change of chemical or physical properties. We demonstrate the possibility to fabricate novel materials with biocide activity based on simple and cheap Cu-Zn alloy. In this research, we propose a green preparative technique for the sonication of an alloy in an alkali solution. The method leads to a significant visual change and differentiation of particles into three different fractions. Due to the chemical micro gradients in media near the solid surface under intensive sonication, fast formation of specific functional groups occurs on the particles' surface. The particles were studied X-ray diffraction analysis (XRD) analysis, the field-emission scanning electron microscope (SEM) as well as electron backscatter diffraction (EBSD) mode, X-ray Photoelectron Spectroscopy (XPS), the differential pulse anodic stripping voltammetry (DPASV) technique. A strong correlation of both methods proves a redistribution of copper ions from Fraction I to Fraction III that influence for the antibacterial properties of the prepared material. The different biocidal activity was demonstrated for each separated Fraction that could be related to their different phase content and ability to release the different types of ions.

Keywords: Antibacterial properties; Metal particles; Nanostructuring; Oscillations; Sonochemistry; Ultrasonic treatment.

Graphical abstract

Fig. 1

A) the schematic illustration of ultrasound treatment of cu-zn alloy particles in 0.5 M NaOH during 30 min with 80 % of amplitude. After the sonochemical modification formed three fractions with different colors: Fraction I (yellow), Fraction II (gray), Fraction III (black) (b). c) The photos of the separated Fractions of Cu-Zn alloy. d–e) SEM images of Fraction III (d), Fraction II (e), and Fraction I (f).

Fig. 2

XRD patterns of α-brass samples before (plot 1) and after sonochemical treatment at the intensity of 87 W/cm² for 30 min (plots 2–4). Fraction I is a plot 2, Fraction II is a plot 3, Fraction III is a plot 4. Abbreviations: B – α-brass, * – γ-brass (Cu₅Zn₈), N – Na₂CO₃·H₂O, C –Cu₂O, Z – ZnO.

Fig. 3

Potentiometric titration for determining the release of copper ions (a) and zinc ions (b). Core-level XPS spectra of Cu 2p for control (c), Fraction I (d), Fraction II (e), Fraction III (f).

Fig. 4

Electron backscatter diffraction studies of initial (control) and ultrasonically treated CuZn particles. All the studied samples are represented as images in backscattered electrons (BSE), diffraction contrast (DC) and local misorientation (LM) images. Legends and distribution graphs correspond to LM images.

Fig. 5

A-e) the photo of inhibition zone diameter of three fractions and cu powder forS. aureus, E. coli, K. pneumoniae, P. aeruginosa, and E. cloacae, respectively. f) - j) Scanning electron microscopy images of bacterial cell damage. k) Ratio of inhibition zone for five bacterial strains and powders of brass, copper and zinc particles taken as controls. Error bars are s.d. values, p < 0.05. (l) The scheme of the predominant ions release from Fractions I-III.