Capacitive Detection of Morphine via Cathodically Electropolymerized, Molecularly Imprinted Poly( p ‐aminostyrene) Films

Highly sensitive and selective detection of morphine is exhibited using a capacitive transducer coated with cathodically electropolymerized and molecularly imprinted poly(p aminostyrene). Through molecular imprinting, morphine-specific recognition sites have been fabricated throughout the film, which shows exceptional binding activity toward morphine based from electrochemical capacitance measurements. The thin film sensor has a linear response to morphine solutions with 20–40 × 10−6 m concentrations and a detection limit of 5.95 × 10−6 m. It demonstrates high selectivity toward morphine as compared to other analog molecules including nicotine and cholesterol. The formation of the polymer film is facilitated and monitored using electrochemical-quartz crystal microbalance and characterized by X-ray photoelectron spectroscopy. Infrared spectroscopy confirms the loading and removal of the analyte from the film. Based on molecular modeling calculations, strong hydrogen-bonding interactions between the monomer, cross-linker, and analyte form a stable pre-polymerization complex, which is critical in successfully imprinting morphine into the film and effective sensing of the analyte.