Chemical sensors of monocyclic aromatic hydrocarbons based on sol–gel materials: kinetics of trapping of the pollutants and sensitivity of the sensor

We report the study of the trapping process of benzene and toluene in porous, hybrid organic–inorganic materials prepared via the sol–gel process. In particular, the kinetics of diffusion of the pollutants within the matrices are studied as functions of the composition, polarity and thickness of the matrix. The concentrations of the pollutants in the air are directly measured via their absorbance in the UV, using three different protocols of exposure of the sensor to the pollutants. A threshold of detection of 60 ppb is achieved when the sensor is a monolith of hybrid TMOS/MeTMOS of stoichiometry 9/1.