Imprinted Poly(acrylic acid) Films on Cadmium Selenide. A Composite Sensor Structure that Couples Selective Amine Binding with Semiconductor Substrate Photoluminescence

Molecularly imprinted films of poly(acrylic acid) (PAA) have been coated onto n-CdSe in order to make the band-edge photoluminescence (PL) of the semiconductor respond selectively to the imprinting analyte. This strategy has been implemented using PAA films deposited in the presence of ammonia and trimethylamine analytes. PAA films have been characterized by IR spectroscopy, which indicates that binding of either analyte nearly reversibly deprotonates the polymer carboxylic acid groups. PL measurements suggest that the imprinted PAA coatings serve as sieves for selective surface binding: In contrast to the bare CdSe surface, which responds both to ammonia and trimethylamine with reversible enhancements in PL intensity, CdSe coated with ammonia-imprinted PAA (AI−PAA) films exhibits reversible PL changes toward ammonia but no response to trimethylamine. The PL changes for the AI−PAA films can be fit to a dead-layer model that indicates that ammonia binding reduces the CdSe depletion width by ∼100 A, an eff...