Influence of temperature on the physical properties and bio-activity of pure (ligand-free) EB PVD silver nanoparticles

Comprehensive studies of the influence of temperature on physical and bacteriological properties of 16 wt% Ag-NaCl condensates were performed. The selected method of electron beam physical vapour deposition allowed synthesizing pure (ligand-free) silver nanoparticles in the salt matrix, and scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), dynamic light scattering and inductively coupled plasma atomic emission spectroscopy methods enabled obtaining detailed physical parameters of silver nanoparticles: their shape, size and location in the matrix, their size distribution, element and phase composition. TGA fixed the processes of transformation in Ag–O system, but the low thermodynamic stability of silver–oxygen compounds did not allow their direct identification by TEM and XRD techniques. Preparations with silver nanoparticles, both the initial sample and samples produced at different annealing temperatures (200 °C, 400 °C, 650 °C) in concentrations of 10.0 and 20.0 mg/l, have bactericidal action on S. aureus strains already after 24 h of exposure. With all the diversity of the studied physical parameters, it was found that increase in annealing temperature leads to enhancement of bacteriostatic action of silver nanoparticles (15–20 nm) relative to bacteria of S. aureus (gram-positive) with minimum inhibiting concentration of 5 mg/l.