In this paper, we describe the facile synthesis and physicochemical characteristic of nitroxide-coated silver nanoparticles. The proposed procedure allows to obtain isolatable, devoid of Ag + impurities, longterm stable, spherical nanoparticles with an average diameter ca. 7 nm, which exhibit high antibacterial 10 activity towards both Gram-negative and Gram-positive strains. The determined Minimum Bactericidal Concentrations (MBCs) are significantly lower than the values reported for other thiolate-capped silver nanoparticles and range from 4 µg/ml (against Pseudomonas aeruginosa) to 12 µg/ml (against Staphylococcus aureus). Our studies proved that the nitroxide coverage favours antibacterial activity of silver nanoparticles, probably due to the ability of nitroxides to be oxidized by reactive oxygen species 15 (ROS) to positively charged oxoammonium ions which can interact strongly with bacterial membrane. Furthermore, the mechanism of chemisorption of disulphide bisnitroxide on silver surface has been discussed on the basis of XPS, FTIR and ESR results. 65 impurities from AgNPs suspensions on the accurate evaluation their toxicity. It is worth to point out that the comprehensive