Effect of various capping agents on photocatalytic, antibacterial and antibiofilm activities of ZnO nanoparticles

• Nanoparticles were prepared by chemical co-precipitation method.
• The average size was determined to be 55 nm.
• ZnO NPs possessed excellent photocatalytic, antibacterial and antibiofilm activities.
• Capping of particles reduced the photocatalytic activity.
• Except for ZnO-PVP, all other capped particles had a lower antibacterial and antibiofilm activity than ZnO NPs.

Zinc oxide nanoparticles (ZnO NPs) are extensively used in a wide variety of commercial products including sunscreens, textiles and paints It is a known fact that ZnO NPs are not stable when dispersed in water, therefore manufacturers use several surface modifying agents to increase the stability of ZnO NPs. In the present study, ZnO NPs were synthesized via chemical co-precipitation with and without the use of surface modifying agents including ethylene glycol (EG), gelatin, polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Preliminary characterization was done by UV–Visible spectroscopy. Electron microscopic analysis showed that the particles were hexagonal in shape. The hydrodynamic size distribution was analyzed by using dynamic light scattering method and crystalline nature was determined by X-ray diffraction method. The study evaluated the photocatalytic, antibacterial and antibiofilm activities of the particles with and without the addition of surface modifying agents. The capping of the particle was confirmed by FT-IR spectroscopy. The photocatalytic activity was checked against methylene blue. Capping of the particles reduced the photocatalytic activity of the particles. The antibacterial and antibiofilm activities were checked against Staphylococcus aureus (MTCC 3160) and Pseudomonas aeruginosa (MTCC 1688). Antibacterial activity was analyzed by simple plate count method both under dark as well as light condition. Antibiofilm activity was checked in both pre- and post-biofilm formation period under both dark as well as light condition. The activity was evaluated via crystal violet staining method. All the particles showed good antibacterial and antibiofilm activities.