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This study is aimed to synthesize zinc oxide nanoparticles (ZnO NPs) from Aloe barbadensis Miller leaf extract using the green synthesis method at room temperature. The biosynthesized NPs are characterized by X‐ray diffraction (XRD), UV–vis spectroscopy (UV–vis), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM). The XRD pattern has revealed the hexagonal wurtzite structure with a crystallite size of 16 nm for synthesized ZnO NPs. The FTIR results display the formation of ZnO NPs and the presence of other functional groups. The UV–vis absorption spectrum shows an absorption band at 347 nm and the value of the bandgap is found to be 3.75 eV. The surface morphology of synthesized NPs is visualized by SEM images, it is observed that most of the NPs are needle in shape. Further, these NPs will find applications in biosensing and photocatalytic activity. [ABSTRACT FROM AUTHOR]

The study compared the antibacterial activity of synthesized ZnO nanoparticles (NPs) from fresh leaf and fresh stem bark aqueous extracts of Carica papaya against five selected microbes: Staphylococcus aureus, (Gram positive (+ve)), Escherichia coli (Gram negative (-ve)), Acinetobacter baumanni (Gram-ve), Exiguobacterium aquaticum (Gram+ve), and Klebsielia pneumonia (Gram +ve). The morphological features of the biosynthesized ZnO NPs were analyzed using transmission electron microscope (TEM) and scanning electron microscope (SEM); the Fourier-transform infrared spectrometer (FTIR) technique was used to observe the surface functional groups. The experimental results indicated that ZnO NPs were successfully synthesized using modified hydrothermal technique, which showed agglomerated flake-like or petal-like shapes with the organic extract surrounding the formed particles. The average particle size of the synthesized ZnO nanoparticles determined by SEM ranged between 54-97 nm with the width and length of the petal-like structures been 30 nm and 62 nm respectively. The average ZnO NPs from fresh stem bark extract of Carica papaya with higher concentrations (100-1000 ppm) demonstrated a higher antibacterial activity than the fresh leaf extracts. On the other hand, ZnO NPs from fresh leaf extracts of lower concentrations (25-50 ppm) rather showed a suitable result than the fresh stem bark. In general, ZnO NPs showed a positive antibacterial result towards the selected microbes. This shows that, the synthesized ZnO NP can be a substitute to chemical methods. [ABSTRACT FROM AUTHOR]