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Preparation of Ag nanoparticles with high antibacterial activities and low adverse effects is urgently needed to apply to the medical and consumer products. In this study, a facile, one-step hydrothermal method has been developed to synthesize proanthocyanidins-functionalized Ag nanoparticles in aqueous solution. UV absorption spectra measurement indicated that the obtained Ag nanomaterials are mainly spherical in shape. FTIR results implied that the poly flavonoids moiety of proanthocyanidins have specific interactions with the surface of Ag nanoparticles. HR-TEM and XRD determination revealed that the Ag nanoparticles had a shell-core structure and the Ag core possessed a highly crystalline structure. Antibacterial tests demonstrated that the proanthocyanidins-functionalized-Ag nanoparticles have high bactericidal efficiency against both bacterial and fungus. Further taking into account their excellent stability, the proanthocyanidins-functionalized Ag nanoparticles in present study have the potential to be applied to the products required for the long-acting antibacterial action. [ABSTRACT FROM AUTHOR]

This study provided a facile, one-step hydrothermal method to synthesize stable Ag colloid in aqueous solution by utilizing chitosan as both reductant and stabilizer. The formation of chitosan-functionalized Ag nanoparticles was verified by UV–Vis, FTIR, TEM, AFM and XRD measurements. FTIR results revealed that the primary amine groups and amide groups of chitosan have specific interactions with the surface of Ag nanoparticles. The average diameter of the Ag nanoparticles is 10.0 ± 5.4 nm as determined by TEM. Ag nanoparticles are highly crystalline as revealed by HR-TEM and XRD measurements. The size and shape of Ag nanoparticles are also found to depend on the pH condition in the synthesis. Ag nanoparticles were the main products at pH 5.0 whereas large Ag nanotriangle and truncated triangular nanoplate were dominant at pH 4.0 in the synthesis. Due to its monodispersity and good stability, the chitosan-functionalized Ag colloid synthesized at pH 5.0 was further tested for its antibacterial activities against gram-positive bacteria, gram-negative bacteria and fungus. The results of zone of inhibition, inhibition ratio and SEM characterization revealed that chitosan-functionalized Ag nanoparticles have great bactericidal efficiency against both bacteria and fungus. [ABSTRACT FROM AUTHOR]