Nanomaterials Enabled Chemical Sensors: The Detection of Hydrocarbons with a High Degree of Sensitivity and Selectivity

Nanocomposite materials composed of CdSe quantum dots embedded in polymer matrices were studied for their potential development and use as highly sensitive and selective hydrocarbon sensing materials. Multi-level selectivity enhancement characteristics have been incorporated into the design of this nanocomposite system to provide the high level of selectivity required for future field measurements. This has been achieved by using a combination of stabilizing and a "surface enhancing" group attached to the surface of CdSe semiconductor quantum dots. Benzoic acid (BA), pentafluorbenzoic acid (FBA) or naphthylamine (NA) was used as the surface enhancing group. The modified QDs were embedded into a poly (methyl methacrylate) polymer film. Reversible photoluminescence changes of the QDs were observed upon exposure to toluene and xylenes vapors. A comparison of the sensitivity and selectivity of the QD-BA, FBA and NA films was made for 50 ppm toluene in N₂ and 50ppm xylenes in N₂ exposures revealed that the QD-FBA film had the best overall performance. By reducing the NA surface group coverage by a factor of 10 the detection limit of the QD-NA films was reduced by a factor of ~3.