Xylene sensing properties of aryl-bridged polysilsesquioxane thin films coupled to gold nanoparticles

Surface plasmon resonance gas sensors based on organic-inorganic hybrid thin films coupled to gold nanoparticles were fabricated and tested against the detection of xylene at the concentration of 30 ppm. Such nanocomposites are prepared either by dispersing Au nanoparticles inside an aryl-bridged polysilsesquioxane system, synthesized via a sol-gel process, or by depositing an aryl-bridged polysilsesquioxane film on Au nanoparticle sub-monolayers. Ultra-high-vacuum temperature programmed desorption of xylene on both the aryl-bridged polysilsesquioxane films and the nanocomposite Au/hybrid system was investigated, resulting in an interaction energy between the sensitive film and the gas molecules in the 38-139 kJ mol(-1) range. The functional activity of the nanostructured composites as xylene gas optical sensors was tested monitoring gold localized surface plasmon resonance, and was shown to be reversible. The detection sensitivity was calculated in 0.1 ppb through a calibration procedure in the 16-30 ppm range, and a threshold limit of detection of 265 ppb xylene was estimated as three standard deviations of the baseline noise. Typical response and regeneration times are of one min and about one ten of minutes, respectively.