ZnO Nanostructures with Antibacterial Properties Prepared by a Green Electrochemical-Thermal Approach

Abstract

Zinc oxide (ZnO) nanostructures are widely applied materials, and are also capable of antimicrobial action. They can be obtained by several methods, which include physical and chemical approaches. Considering the recent rise of green and low-cost synthetic routes for nanomaterial development, electrochemical techniques represent a valid alternative to biogenic synthesis. Following a hybrid electrochemical-thermal method modified by our group, here we report on the aqueous electrosynthesis of ZnO nanomaterials based on the use of alternative stabilizers. We tested both benzyl-hexadecyl-dimetylammonium chloride (BAC) and poly-diallyl-(dimethylammonium) chloride (PDDA). Transmission electron microscopy images showed the formation of rod-like and flower-like structures with a variable aspect-ratio. The combination of UV–Vis, FTIR and XPS spectroscopies allowed for the univocal assessment of the material composition as a function of different thermal treatments. In fact, the latter guaranteed the complete conversion of the as-prepared colloidal materials into stoichiometric ZnO species without excessive morphological modification. The antimicrobial efficacy of both materials was tested against Bacillus subtilis as a Gram-positive model microorganism.

Antimicrobial Activity of Zinc Oxide Nano/Microparticles and Their Combinations against Pathogenic Microorganisms for Biomedical Applications: From Physicochemical Characteristics to Pharmacological Aspects

“…Meanwhile, various electrochemical processes for synthesis of ZnO NPs/MPs have been reported including electrodeposition [ 39 , 40 ], sacrificial anode electrolysis [ 41 ], and electrochemical deposition under oxidizing conditions (EDOC) [ 42 , 43 ]. Hybrid techniques of electrochemical-thermal processes were also reported in aqueous environment [ 44 , 45 ]. In electrodeposition, ZnO thin films can be produced controlling current density, applied potential, time, and electrolytic bath concentration as major operating parameters using zinc nitrate solution or zinc chloride solution as precursors [ 40 ].…”

“…In EDOC, sacrificial anodic oxidation, cathodic reduction, and oxidation processes were involved for the synthesis of spherical ZnO NPs (9 nm) [ 42 ]. Hybridizing electrochemical and thermal approaches, ZnO NPs/MPs were synthesized in aqueous sodium bicarbonate solution, generating zinc hydroxide species and further oxidized to ZnO in calcination process at >300 °C [ 44 , 45 ]. Specifically, anionic or cationic stabilizers can be used to tune physicochemical properties of ZnO NPs/MPs including morphology and particle size.…”

“…In 3D structured ZnO NPs/MPs such as antibiotic agents, flower-like ZnO MPs were synthesized using electrochemical-thermal method with poly-diallyl-(dimethylammonium) chloride (PDDA) and benzyl-dimethylammonium chloride (BAC) as a stabilizer, which were 200–500 nm or 1–2 μm long [ 45 ]. Flower-shaped ZnO NPs were also synthesized using the sol–gel method reacting with 5% zinc acetate dihydrate and 0.2 w/v % cetyltrimethyl ammonium bromide (CTAB) at pH 11.7–11.9, and 25–75 °C of near-room temperatures [ 59 ].…”

On the Efficacy of ZnO Nanostructures against SARS-CoV-2

“…Elongated submicrometer rice-grain structures (with length around 1 µm) could be obtained preparing the colloids at 80 • C with CTAB and calcining them at 300 • C [14] (Figure 2a). PDDA, after overnight drying at 120 • C, promoted the formation of wire-like microstructures, with a major length of 300-500 nm; growth lines moving along the wires suggested that these structures grew by lamellar superimposition [15] (Figure 2b). The use of PSS resulted in spheroidal NPs, with an average diameter around 50 nm, which aggregated in micron-sized clusters after calcination at 600 • C (Figure 2c).…”

Recent Progress in Antimicrobial Nanomaterials

“…Bearing in mind the recent growth in environmentally friendly and low-cost synthetic routes for nanomaterial synthesis, electrochemical techniques represent a valid alternative to biogenic synthesis. In this regard, the aqueous electrosynthesis of ZnO nanomaterials (both rod-like and flower-like structures) with different aspect ratios based on the use of alternative stabilizers such as benzyl-hexadecyl-dimethylammonium chloride (BAC) and poly-diallyl-(dimethylammonium) chloride (PDDA) has been reported [ 20 ]. The combination of UV–vis, FTIR, and XPS spectroscopies demonstrated the whole conversion of the raw colloidal materials into stoichiometric ZnO species with moderate morphological modification.…”