Correlation notice on the electrochemical dealloying and antibacterial properties of gold–silver alloy nanoparticles

Galvanic replacement reaction was used in the synthesis of bimetallic gold–silver alloy nanoparticles (Au–Ag NPs), where pre-synthesized Ag nanoparticles-polyvinylpyrrolidone (AgNPs-PVP) were used to reduce the aryldiazonium tetrachloroaurate(III) salt in water. TEM images and EDS elemental analysis showed the formation of spherical Au–Ag NPs with sizes of 12.8 ± 4.9 nm and 25.6 ± 14.4 nm for corresponding Au–Ag ratios and termed as Au 0.91 Ag 0.09 and Au 0.79 Ag 0.21 , respectively, with different concentrations of the gold precursor. The hydrodynamic sizes measured using dynamic light scattering are 46.4 nm and 74.8 nm with corresponding zeta potentials of − 44.56 and − 25.09 mV in water, for Au 0.91 Ag 0.09 and Au 0.79 Ag 0.21 respectively. Oxidative leachability of Ag ion studies from the starting AgNPs-PVP in 1 M NaCl showed a significant decrease in the plasmon peak after 8 h, indicating the complete dissolution of Ag ions, however, there is enhanced oxidation resistivity of Ag from Au–Ag NPs even after 24 h. Electrochemical studies on glassy carbon electrodes displayed a low oxidation peak in aqueous solutions of 20 mM KCl at 0.16 V and KNO 3 at 0.33 V vs. saturated calomel electrode (SCE). We studied the antibacterial activity of Au–Ag alloy nanoparticles against gram-positive Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and gram-negative Escherichia coli , Salmonella typhimurium, and Pseudomonas aeruginosa . Our findings demonstrated superior antibacterial activity of Au–Ag NPs compared with AgNPs-PVP. Moreover, the nanoparticles inhibited the S. epidermidis biofilm formation. Graphical abstract