Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry

•AgNPs-EPS are biosynthesised under aerobic and anaerobic conditions.•The oxidation state of Ag present in the AgNPs is assessed by SECM measurements.•The Ag(I) species released are monitored by combining SECM and ASV measurements.

Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide