Synthesis and characterization of ZnO nanoparticles for antibacterial paints

A hydrothermal method was selected for the synthesis of ZnO nanoparticles from zinc salts, namely NO 3 − , SO 4 2− , CO 3 2− , C 2 H 3 O 2 − and Cl, at different pHs and heat treatment modes (Oven drying, microwave reactions or sonolysis of mixtures containing surfactants or polymers) under continuous addition of NaOH. The substitution has been reinforced by introduction of tetramethyl ammonium hydroxide (TMAH) or hexamethylenetetramine (HMTA) which act as separator for the isolation of ZnO particles. The synthesized powders were characterized by X-ray diffraction (XRD), laser granulometry and scanning electron microscopy (SEM). The XRD pattern revealed that the synthesized ZnO crystallizes in the wurtzite structure with an average particles size of 190 nm. The SEM analysis showed that the surface morphology of ZnO is in the form of the fibers. In addition, a new antibacterial paint based on nanoparticles with a formulation ten times less than in the classic paint has been developed and tested. Its physico-chemical characteristics (viscosity, density and covering power) are similar to those of conventional paint based on micrometric ZnO with an improved stability and whiteness at a lower percentage. The antimicrobial activity of classic and nanoparticles ZnO paints was examined against Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacteria. Both ZnO powders showed an activity against the two tested germs. A change in the diameter of the inhibition zone was noted as a function of the bacteria concentration. The results obtained highlighted the role of surfactants and polyelectrolytes such as polyethylene glycol and polyethylenimine in the nanoparticles synthesis by the hydrothermal technique. In addition, the antibacterial effect of the new nanoparticles-based paint was found to be more effective.