SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF COLLOIDAL SOLUTIONS OF BICOMPONENT Ag/CuO NANOPARTICLES STABILIZED BY RAMNOLIPID

Despite the extremely high activity of researchers in the direction of green synthesis of nano-particles of silver, copper, as well as bimetallic nanoparticles Ag/Cu-NPs, the many aspects of the synthesis of nanoparticles based on silver and copper remain unexplored, in particular, the studies on the influence of the nature of biosurfactants on the characteristics are relevant obtained nano¬particles, in particular their size, shape, etc., as well as the influence of the morphology and compo¬sition of nanoparticles on their antimicrobial properties. Therefore, the purpose of this work was to synthesize colloidal solutions of bicomponent Ag/CuO-NPs nanoparticles of different composition and to investigate their antimicrobial activity. Bicomponent Ag/CuO nanoparticles of different composition were obtained by the method of coprecipitation of Ag+ and Cu2+ cations in solution of rhamnolipid. It was found that the process of formation of monocomponent CuO nanoparticles is completed within 2.5 hours but the reduction of silver ions in aqueous solutions of RL occurs within a few minutes. The obtained Ag/CuO-NPs were studied using UV-visible spectroscopy and the method of powder diffraction of X-rays. It was found that the absorption spectra of Ag/CuO-NPs solutions are characterized by two maxima at 280 and 410 nm, which correspond to the surface plasmon resonance bands of CuO and Ag-NPs, res-pectively. Based on the obtained data, it is reasonable to assume that the obtained Ag/CuO-NPs can form core-shell structures in which the role of the core will be played by silver surrounded by a CuO shell. Taking into account the prospects of using the nanoparticles based on silver and copper as antimicrobial agents for the plant protection, the antimicrobial activity of the synthesized Ag/CuO-NPs was investigated. The gram-negative bacteria-phytopathogens were used as test microorganisms, namely Agrobacterium tumefaciens, which is the causative agent of crown gall disease of a wide range of agricultural crops and Xanthomonas campestris, which is the causative agent of the "black rot" disease in cruciferous vegetables. The antimicrobial activity of the synthesized colloidal solutions of Ag/CuO was evaluated by the minimum inhibitory concentration values. The results of the studies of antimicrobial activity of the synthesized Ag/CuO colloidal solutions showed that the obtained preparations effectively inhibit the growth of phytopathogenic bacteria Agrobacterium tumefaciens and Xanthomonas campestris and it was found that the obtained drugs are more active against the Xanthomonas campestris.