Mesoporous silica nanoparticle film as sorbent for in situ andreal-time monitoring of volatile BTX (benzene, toluene and xylenes)

A strategy is described for the real time and selective monitoring of benzene, toluene and xylenes (BTX)in air. Rapid preconcentration and recovery have been achieved with films made of mesoporous silicananoparticles assembled on a quartz plate. The resulting nanoparticle films displayed high transmittanceand allowed the detection of toluene up to 1 ppm within a minute and a regeneration of the sensor inless than 30 s. The sensor response increased while increasing the concentration of benzene (detectionat 252 nm), toluene (detection at 267 nm) or p-xylene (detection at 274 nm) in the polluted air from 1to 100 ppm. The order of sensitivity, i.e. p-xylene > toluene > benzene, was correlated with their respec-tive molar extinction coefficients. The BTX adsorption on mesoporous silica nanoparticle films has beenanalyzed with the Freundlich adsorption model. The repeatability of the detection was good in intraday(2%) and extra-day (4%) experiments with a given sensor. The ability to detect toluene in the presenceof volatile compounds often encountered in working environments (i.e., methyl ethyl ketone, ethanol,acetone and cyclohexane) has been shown. The introduction of a gas dryer before the measurement cellallowed application of the sensor in humid atmosphere. This sensor could be used to alert if permissiblevalues of exposure to toluene and xylenes have been reached during work.