Abstract
This research investigated the effect of synthesis temperature on the size and shape of zinc oxide (ZnO) nanoparticles (NPs) synthesized using pineapple peel waste and antibacterial activity of ZnO NPs in starch films. Zinc oxide NPs synthesized at different temperatures were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Micrographs of ZnO NPs synthesized at 28 and 60 °C showed that synthesis temperature affected the sizes and shapes of ZnO NPs. The non-heated (28 °C) condition resulted in NPs with diameters in the range of 8–45 nm with a mixture of spherical and rod shapes, whereas the heated (60 °C) condition led to NPs with diameters in the range of 73–123 nm with flower rod shapes. The ZnO–starch nanocomposite films incorporated with 1, 3, and 5 wt.% ZnO NPs were prepared via a film casting method. The antibacterial activity of the films against Gram-positive and Gram-negative bacteria was investigated using the disc diffusion method. The results showed an increase in the inhibition zone for Gram-positive bacteria, particularly Bacillus subtilis, when the concentration of ZnO NPs incorporated in the film was increased from 1 to 5 wt.%.
Highlights
Zinc oxide (ZnO) has drawn the attention of numerous researchers because of its morphology and its significant antibacterial/antifungal activity toward various bacterial/fungal species [1]
The zinc oxide (ZnO) NPs were successfully synthesized from pineapple peel extract which acted as a natural reducing agent in the bioreduction process
The Fourier transform infrared (FTIR), EDX, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) showed differences in particle structure, size, morphology, and chemical constituent of ZnO NPs synthesized at 60 ◦C and 28 ◦C
Summary
Zinc oxide (ZnO) has drawn the attention of numerous researchers because of its morphology and its significant antibacterial/antifungal activity toward various bacterial/fungal species [1]. ZnO has numerous biological applications, because it is environmentally friendly, easy to prepare, non-toxic, bio-safe, and biocompatible [2]. Researchers have actively investigated the green synthesis approach, which is an environmentally friendly method that is safe for materials that contact food and biomedical applications, where it generates fewer adverse effects than physical and chemical methods [3]. The numerous methods for ZnO NPs production, including hydrothermal synthesis, precipitation the microemulsion method, vapor deposition and the sol-gel process, enables obtaining particles with a variety of structures, sizes, and shapes [4,5,6]. According to Ma et al [7], the simplest route is an acid–base precipitation method which was widely used to obtain ZnO nanoparticles for either biological or coating application. An aqueous precipitation process was employed using precursors, such as zinc acetate (Zn(CH3COO)2) [8], zinc nitrate (Zn(NO3)2) [9] or zinc sulfate (ZnSO4) [10], and an alkaline aqueous solution, such as sodium hydroxide (NaOH), are usually prepared in deionized/distilled water
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