Sensor for detection of water presence in gaseous mixtures based on gold nanoparticles stabilized by sodium citrate

The adsorption properties of organic–inorganic sensitive films formed by gold nanoparticles dropped from sodium citrate solutions of different concentrations are investigated using mass-sensitive (QCM) sensors. The obtained sensitive layers, composed of discontinuous assembly of gold nanoparticles and sodium citrate film have demonstrated several special adsorption properties. The most interesting among them are (i) the reverse dependence of the sensitivity on the initial colloid solution concentration, (ii) the difference of the response value for alcohols and water (the sensitivity to water is more than one order higher than to alcohols) and (iii) the character of water adsorption curves (the presence of two stages of adsorption with different kinetics). The physical mechanism of water adsorption on the citrate–gold surface is considered to be concerned with the presence of two processes: adsorption and diffusion of water molecules along the surface of citrate to the gold nanoparticles. Gold nanoparticles in this case serve as drains for water molecules. The results obtained can be applied for the development of sensors for the detection of water presence in gaseous mixtures of different nature.