Quantum dot-enabled chemical sensors: The detection of hydrocarbons with a high degree of sensitivity and selectivity

Nanocomposite films comprised of cadmium selenide (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 surface-modifying groups attached to the surface of CdSe semiconductor quantum dots (QDs). Benzoic acid (BA), pentafluorbenzoic acid (FBA), or naphthylamine (NA) were used as the surface-modifying groups. The modified QDs were embedded into a poly (methyl methacrylate) polymer film. Reversible photoluminescence (PL) changes of the QDs were observed upon exposure to toluene and xylenes vapours. A comparison of the sensitivity and selectivity of the QD—BA, QD—FBA, and QD—NA films was made for 50 ppm toluene in nitrogen (N₂) and 50 ppm xylenes in N₂ exposures to reveal that the QD—FBA film had the best overall performance.