Integration of ZnO nanorods with silver ions by a facile co-precipitation for antimicrobial, larvicidal, and ovicidal activity

Abstract

Background: Infectious diseases prompted by micro-organisms such as fungi, parasites, or microbes, have influenced many countries' public health causing death. Scientists declared that metal oxide composites have various advantages in the medical field such as the antimicrobial feature has freshly been revealed as well as its role in suppressing mosquito population.

Methods: In this work silver doped zinc oxide nanorods (Ag/ZnO NRs, 10 wt.%) were prepared by simple chemical route, and their microstructural characteristics were investigated by XRD, EDX, SEM, and TEM techniques. The antimicrobial, larvicidal, and ovicidal of the synthesized nanocomposites were examined.

Results: The synthesized nanocomposite exhibited binary phase of crystallite size 112 nm was calculated from Williamson-Hall method. EDX spectrum revealed the purity of the composite consists of Zn, O, and Ag elements. The SEM and TEM micrographs showed the particles in nanorods with high density on the surface. The energy gap [Formula: see text] was evaluated from the UV-Vis absorbance in the range from 2.90 [Formula: see text] 3.08 eV inside the visible spectrum. The antimicrobial activity of the nanorods was examined against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) with inhibition zones 10.5 and 14.5 mm, respectively. Whereas gram-negative bacteria (Escherichia coli, Salmonella Typhimurium, and Pseudomonas aeruginosa) were 14 and 17 mm, respectively. Further, Candida albicans was investigated with inhibition zone 7.5 mm. Besides, the insecticidal impact of the nanocomposite against Culex pipiens larvae was performed at 30 mg/l causing 100% larval mortality with LC₅₀ (11.78 mg/l). The micrograph images showed deformations in the larval body as well as egg resulting in zero egg hatchability.

Conclusion: The findings approved that synthesized nanorods have a significant impact on controlling pathogens that impart different diseases to humans and the environment.

Keywords: Ag/ZnO NRs; Antimicrobial; Co-precipitation; Energy gap; Larvicidal; Ovicidal.

Fig. 1

The scheme of impact the nanocomposite Ag/ZnO on bacteria, mosquito larvae, and egg

Fig. 2

A XRD pattern, B W–H plot, and C EDX spectrum of the synthesized Ag/ZnO nanocomposite

Fig. 3

A SEM micrograph, B TEM micrograph, C Diameter and d Length distribution diagram of Ag/ZnO nanorods

Fig. 4

A Optical absorbance and B Energy gap (E_g) plot of Ag/ZnO thin film

Fig. 5

The inhibition zones indicating the antimicrobial activity of Ag/ZnO NRs against gram positive and gram-negative bacteria

Fig. 6

Probability analysis of mortality of C. pipiens mosquito larvae by Ag/ZnO NRs

Fig. 7

Light microscope photographs of the 3rd larval instars of Cx. pipiens. A normal larval body parts, B normal thoracic and abdomen with alimentary canal, C normal respiratory siphon and gills, D treated larvae with Ag/ZnO, E accumulate of nanoparticles in larval gut, F block of respiratory opening with nanoparticles (10 × 150). SEM images of treated larvae, G the deformation of head region, H malformed thoracic and abdomen parts with NPs, I blocking siphon with NPs. (Abd: abdominal segments, G: gill, H: head, Siph: siphon, TH: thoracic)

Fig. 8

SEM micrographs of the control egg rafts mosquito Cx. pipiens A, B normal egg with cap-like circular micropylar and conical-shaped and C, D showed treated non hatched egg raft with malformed structure. (dEg: deformed egg, Mc: micropylar corolla, Tr: tubercular row)

Fig. 9

Antibacterial activity mechanism of Ag/ZnO NRs