ZnAl layered double hydroxides impregnated with eucalyptus oil as efficient hybrid materials against multi-resistant bacteria

Bacterial contamination poses a serious hazard for human health. The use of bactericidal materials, such as layered double hydroxides, might constitute a way to reduce the risk of diseases. In this work, ZnAl layered double hydroxides were synthesized by microwave irradiation at different pH values and various metal molar ratios to be tested against multi-resistant bacteria. The synthesis conditions were chosen to form, in some cases, a composite containing zincite (ZnO), as both materials, zincite as well as the layered double hydroxide, are well known to be efficient antimicrobials. Eucalyptus extracted oil, which is a bactericidal compound, was extracted from eucalyptus leaves and used to impregnate some layered double hydroxide zincite composites. The materials were characterized by X-ray diffraction, infrared spectroscopy, nitrogen physisorption and scanning electron microscopy. The samples were tested against Staphylococcus sp. and Pseudomonas aeruginosa, which are multi-resistant bacteria. It was found . that Zn/Al molar ratio, pH and inclusion of eucalyptus oil in the layered double hydroxides synthesis determined the bactericidal activity. The best performing samples were those containing eucalyptus oil, which, at very low concentrations, were able to kill Staphylococcus sp. and inhibit the Pseudomonas aeruginosa growth.