Eco-inspired synthesis of ZnO/CuO nanocomposites using Phyllanthus niruri: unveiling superior photocatalytic, antibacterial efficacy against Escherichia coli and Staphylococcus aureus, and latent fingerprint studies

The current study focuses on the facile green synthesis of ZnO/CuO nanocomposites (NCs) mediated by Phyllanthus niruri leaf extract as a capping agent and fuel. The characterization of the synthesized NCs in comparison with the pure ZnO and CuO NPs was conducted using XRD, FT-IR, SEM-EDAX, HR-TEM, UV–Vis DRS, and PL studies. XRD analysis revealed their crystalline nature with an average crystallite size of 25 nm. SEM images showed particle agglomeration, and EDAX confirmed the elemental composition of the pure phase. HR-TEM images elucidated the presence of spherical and hexagonal shapes. The presence of bond vibrations such as Zn − O and Cu − O was confirmed by FT-IR analysis. The optical energy bandgaps were determined to be 3.27, 2.8, and 2.7 eV for ZnO, CuO NPs, and ZnO/CuO NCs respectively. PL studies of the synthesized NCs showed a blue emission with a peak position at 493 nm. The photocatalytic activity of ZnO/CuO NCs exhibited a degradation efficiency of 97.93% against methylene blue dye and 53% towards the Rose Bengal dye. Furthermore, the investigation of antibacterial activity by 96-well microtiter plate method against two bacterial strains, Escherichia coli and Staphylococcus aureus, revealed significant zones of inhibition, and when compared to the common antibiotic ciprofloxacin, the MIC values were 3.90 µg/mL for both Staphylococcus aureus and Escherichia coli, while the MBC values were 2.05 µg/mL for Staphylococcus aureus and 2.19 µg/mL for Escherichia coli. The prepared materials were additionally tested for latent fingerprint activity. The NCs displayed excellent properties, producing visible, clear images of latent fingerprints. Thus, the ZnO/CuO nanocomposites (NCs) synthesized using Phyllanthus niruri leaf extract could be a desirable catalyst for wastewater treatment and a potent antimicrobial agent against the bacteria and can be used for latent fingerprint applications.

Graphical Abstract