We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which urease was immobilized on electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode configuration. For comparison, the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP/urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate ions. Using the Michaelis-Menten kinetics equation, a K(M)(app) of 2.7 mmol L(-1) was obtained, indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties.

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In this work we present the electrical and optical characterization of polymer light-emitting diodes (PLEDs) using indium-tin oxide (ITO), polyaniline (PAni), poly( p-phenylene vinylene) (PPV) + dodecylbenzenesulfonate (DBS) and aluminum (Al). To minimize the conversion temperature and reduce the structural defects of PPV layers, we introduced the counter-ion DBS in the PPV precursor polymer. The best PLED electrical properties were achieved at the PPV conversion temperature of 150 • C. Under this condition, the ITO/PAni/PPV+DBS/Al PLED operating voltage decreases to less than a third of the value obtained with the conventional structure ITO/PPV/Al. In addition, the electrical conductivity increases and the thermal degradation decreases in the PAni layer. The line shape of the PPV electroluminescence spectrum shows no influence of the PAni layer at relatively low electrical field (12 MV m −1 ).

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