In this proposed work, zinc oxide nanoparticles (ZnO-NPs) were synthesized using an environment friendly biosynthesis method by employing leaf extract from Azadirachta indica (AI), Cocos nucifera (CN) and Jatropha gossypifolia (JG). The resulting NPs were labelled as Al-ZnO-NPs, CN-ZnO-NPs and JG-ZnO-NPs, respectively. The X-ray diffraction (XRD) analysis confirmed the crystalline hexagonal wurtzite structure of ZnO. The mean crystallite sizes were determined to be 74 nm, 55 nm and 39 nm for AI-ZnO-NPs, JG-ZnO-NPs and CN-ZnO-NPs, respectively. The Fourier-transform infrared (FTIR) analysis confirmed the existence of Zn–O bonds in the plant-mediated ZnO-NPs, along with functional groups corresponding to phytochemicals that act as capping and bio-reducing agents during the synthesis method. The FTIR peak height of Zn-O bond is found to be optimum in CN-ZnO-NPs, an indicate of strong dipole moment change. The scanning electron microscopy (SEM) micrographs revealed the coexistence of spherical and rod like morphologies, with comparatively smaller spherical particles observed in the CN-ZnO-NPs. The Energy dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of Zn and O elements in the ZnO-NPs. The Ultraviolet-visible (UV-Vis) absorbance studies verifies sharp UV peak with band-gap of 3.26 eV, 3.32 eV and 3.26 eV for CN-ZnO-NPs, AI-ZnO-NPs and JG-ZnO-NPs. The photoluminescence (PL) spectra exhibited two peaks in UV region. The peak around 368 nm is associated with excitonic transitions, while the peak around 382 nm can be attributed to variations in particle size distribution and/or the presence of surface defects/shallow energy levels. The photocatalytic performance of plant extract mediated ZnO-NPs was evaluated using Rhodamine B (Rh-B) as a model. The CN-ZnO-NPs have shown, an impressive and optimum photodegradation efficiency of 79% under UV light in 60 min as compared to AI-and JG-ZnO-NPs. The superior performance of CN-ZnO-NPs can be attributed to their smaller crystallite spherical particle sizes, strong dipole moments, the presence of polar surfaces, a greater number of active sites, and efficient electron–hole pair separation. The re-usability test demonstrated that CN-ZnO-NPs are reusable up to 3 cycles. Furthermore, it’s evident from the radical trapping tests that • OH is major contributor to photocatalytic activity. Furthermore, the antibacterial efficacy of CN-ZnO-NPs is estimated against Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa and Streptococcus pyogenes . Remarkably, this work provides first evidence on biofilm inhibition activity of biosynthesized CN-ZnO-NPs, which effectively supressed biofilm formation with a maximum inhibition rate of 91%. Thus, the CN-ZnO-NPs can be considered potential candidates for photocatalytic applications and also as promising alternatives for antibacterial agents, particularly effective in inhibiting bacterial growth and biofilm formation.
M et al. (Mon,) studied this question.