Nanocrystalline silver coatings on steel by electrodeposition from non-polluting aqueous baths and its antibacterial activity

Background

Antimicrobial coatings are one way that could help inhibit the spread of germs. Despite significant research into a variety of antimicrobial coatings with varied formulas, silver-based coatings appear to be the most effective. Electrodeposition is a promising technology to synthesize nanocrystalline silver coatings which have a wide range of applications such as in microelectronics, aerospace, automotive, biotechnology, nanobiotechnology, bioengineering sciences, in addition to its antimicrobial characteristics. Regrettably, cyanide electrolyte which is commonly applied in industry for silver coatings is one of the most hazardous substances, raising serious health and environmental hazards. It is important that seek high environmentally friendly electrolytes alternative to cyanide electrolytes.

Methods

The nanocrystalline silver coatings were successfully synthesized via galvanostatic deposition on stainless steel surface from an environmentally friendly novel bath. The electrochemical measurements were made utilizing linear sweep voltammetry (LCV), and cyclic voltammetry (CV). A high field emission scanning electron microscope (FESEM) and X-ray diffraction analysis (XRD) were used to characterize the obtained silver coatings.

Significant findings

Bright and adherent nanocrystalline Ag coatings (nano-size ranging between 14.8 and 67.6 nm) were synthesized by direct galvanostatic electrodeposition on SS surface from a bath free from cyanide. This environmentally friendly, cyanide-free bath is characterized by its high stability, low cost, and high cathodic current efficiency. The morphology was strongly dependent on the electrolyte composition as well as on the run circumstances. The microhardness of Ag deposited from this bath has a relatively high value (120.2–158.7 kg f mm^-2) depending on the applied current density. Furthermore, the nanocrystalline silver coatings formed by these baths are excellent antibacterial agents versus a vast spectrum of gram-positive and gram-negative bacteria, particularly Listeria and Streptococcus bacteria.