Preparation of urease/nano-structured polyaniline-Nafion®/Au/Al2O3 electrode for inhibitive detection of mercury ion

The level of mercury ion in the aqueous solution was detected based on the inhibition of urease/NSPN/Au/Al2O3 (urease/nano-structured PANi-Nafion®/Au/Al2O3) sensing electrode. When the NSPN composite film/Au/Al2O3 was prepared at 60 μA/cm2 and used as the sensing electrode, the maximum sensitivity for monitoring the level of NH4+ in PBS was obtained to be 2980.3 μA/mM/cm2 due to the dense composite film with exiguous crevices. The detection limit and the sensitivity of amperometric urea biosensor based on urease (2.12 U)/NSPN/Au/Al2O3 obtained at pH 7.0 and 25 °C were 0.005 mM and 4397.5 μA/mM/cm2, respectively. The sensitivities to monitoring mercury ion were 2397.5 and 2884.0 μA/ppm/cm2 for the Hg2+ concentration in the range of 0–0.1 ppm with the urease loadings of 1.06 and 2.12 U. The detection limit of the amperometric mercury ion sensor based on the urea biosensor was found to be 0.01 ppm. The sensing properties of the amperometric mercury ion biosensor were significantly affected by the concentration of urea in the solution.