Effect of light-dark conditions on inhibition of Gram positive and gram negative bacteria and dye decomposition in the presence of photocatalyst Co/ZnO nanocomposite synthesized by ammonia evaporation method

Environmental pollution and various bacterial strains cause severe health problems. Thus a need exists to synthesize new materials and develop new techniques which can be used against these hazardous pathogens and components. In this research work, sustainable and effective Co/ZnO nanocomposites were prepared via a new hydrothermal technique and ammonia evaporation method. The synthesized nanomaterial was analytically characterized through various techniques such as X-ray diffraction (XRD), UV-vis spectroscopy, Scanning electron microscope (SEM), High transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The as prepared nanocomposite was tested for photodegradation of methylene blue (MB). This test was performed both in visible light and in dark condition. The results demonstrate that the said material is more efficient in light compared to dark conditions and decomposed more than 80% MB dye only in 60 min. The synthesized nano material Co/ZnO was also tested against highly drug resistant bacteria Escherichia coli and Staphylococcus aureus both in light and dark. Hence, the antibacterial assessment indicates the zone of inhibition in visible light of Co/ZnO counter with Escherichia coli is 15 (+/- 0.2) and for Staphylococcus aureus is 18 (+/- 0.4) mm and in dark for Escherichia coli is 11 (+/- 0.6) and for Staphylococcus aureus is 14 (+/- 0.1) mm. Moreover, the detail mechanism, reactive oxygen species production and bacterial surface damage were also observed. We demonstrate that Co/ZnO nanomaterial is stable, eco-friendly photocatalyst shows high strength against MB degradation and also shows strong inhibition effect against pathogens in visible light.

Automated summary

In this research, sustainable and effective Co/ZnO nanocomposites were synthesized using a new hydrothermal technique and ammonia evaporation method. The synthesized nanomaterial was characterized through various techniques and tested for its photodegradation and antibacterial properties. The results showed that the Co/ZnO nanomaterial exhibited high efficiency in photodegradation of methylene blue and strong inhibition effect against Escherichia coli and Staphylococcus aureus.