Nanopore-array-dispersed semiconductor quantum dots as nanosensors for gas detection

CdSe quantum dots (QDs) and anodic aluminum oxide (AAO) nanopore arrays were integrated to form an optically active element for chemical vapor detection. The introduction of porous AAO as a platform for QD dispersion is found to have twofolds of merit for QD based chemical sensing. First, AAO intensifies QD photoluminescence (PL), thus increasing the measurable responses, due both to redistributing high intensity near-fields for efficient excitation of QDs and introducing strong scattering effects for enhanced extraction of the resulting QD emission. Second, the nanopores of AAO retard film-wetting effects which occur at higher target chemical exposures and result in an inverted PL response as seen from QDs or QD-polymer films cast on nonporous substrates. The PL and response sensitivity of QDs on AAO is further increased through the use of an Au coated silicon support which increases the overall reflectivity of the composite material stack. These strategies enable QD-based materials to be used for sensitive detection of chemical vapors with monotonic trends across large concentration ranges, for example, 10-9400 ppm xylenes. This method is readily extendable to other systems and opens the door to the development of QD-based optical or optoelectronic devices.