Antibacterial properties and chemical stability of superhydrophobic silver-containing surface produced by sol–gel route

Superhydrophobic surface with and without nano-sized silver particles (AgNPs) using a sol–gel technique were prepared for antibacterial and chemical stability tests and electrochemical characterization. Antibacterial tests showed that the surface with AgNPs reduced the number of the bacteria. However, to be used in long-term industrial applications, the surfaces are required to have sufficient chemical stability in the operation environment. This is why the stability of the produced surfaces was studied as a function of pH value of the solution. According the results, the produced surfaces are stable in neutral environments but release silver ions at high rates and dissolve or undergo other structural changes in strongly acidic and alkaline environments during a timeframe of few weeks. Chemical stability of the produced surfaces may be monitored by electrochemical measurements in addition to straight-forward contact angle measurements. Open circuit potential monitoring effectively revealed the presence of silver on both unexposed and exposed coatings, due to the noble character of the element. Electrochemical impedance spectroscopy yielded information on the overall degradation mechanism of the superhydrophobic silver-containing coating, although its use requires calibration by the use of model systems involving different combinations of all included surface layers and relatively complex data modelling.