Chemical sensors for the detection of organic pollutants

Detection of toxic organic vapours, has been demonstrated, using surface plasmon resonance (SPR) as a potentially inexpensive optical technique. This provides the basis for a viable sensor technology with application in the field of detection of different organic solvents present in the atmosphere in gaseous phase, as a mixture. Calixarene derivatives have been used as the sensing membranes which were deposited as thin films onto Au-coated substrates by the method of spin coating. SPR measurements have been utilised for the detection of benzene, toluene, ethylbenzene and m-xylene, with concentration in the range 5-375 ppm. Surface plasmon resonance has also been exploited for the determination of the thickness and refractive index of the calixarene spun films. Vapour detection has been realised by the shift of the whole SPR curve under the dynamic state of adsorption as well as by measuring SPR reflectivity signal at a fixed angle of incidence. Selective, fast and reversible adsorption of the vapour molecules has been observed. The increase of both film thickness and refractive index of spun films during adsorption are found to correspond to the calixarenes behaviour and may be explained by capturing of guest molecules in the film matrix, followed by their condensation. A model of the vapour registration system has been established and we also report in this paper on the extent of the selectivity, thus leading to the establishment of a sensor array.