Chemical composition and barrier properties of Ag nanoparticle-containing sol–gel films in oxidizing and reducing low-temperature plasmas

Silver nanoparticle-containing silica sol–gel coatings were synthesised using tetraethylorthosilicate (TEOS), HNO3 and AgNO3 as the main precursors and 3-(2-aminoethylamino)propyl trimethoxysilane (DIAMO) as a stabiliser. The stability and the barrier properties of the coatings were studied by means of UV/Vis spectroscopy, FTIR reflection absorption spectroscopy (IRRAS), spectroscopic Ellipsometry and electrochemical impedance spectroscopy (EIS). Both the long-term stability and barrier properties of the coatings could be tailored by low-temperature O2 and H2-plasma treatments. The oxidative plasma treatment enabled the change of the matrix from organic–inorganic to silica-like and the reductive treatment led to a reduction of the formed passive film on the Ag nanoparticles within the matrix. Thereby, based on the combination of sol–gel chemistry with subsequent plasma treatment new thin film functionalities can be achieved.