Electrochemical properties and analytical applications of Keggin-type phosphomolybdic anions in electrostatically linked 2-aminoethanethiol self-assembled monolayers

A composite film containing a heteropolyanion was prepared on a 2-aminoethanethiol (AT) self-assembled monolayer film-modified gold electrode by attaching the Keggin-type phosphomolybdic anion. The surface structures and electrochemical properties of the composite films were characterized by using ATR-FTIR, AC impedance, cyclic voltammetry and chronocoulometry. FTIR studies indicated that there was some electrostatic interaction between PMo12O427- and surface NH3+. Three reversible redox couples were observed in 1.0 mol L-1 H2SO4 in the potential range of 0-0.7 V for the composite film modified electrode, which were attributed to two-electron and two-proton electrochemical processes of PMo12O427-. The diffusion coefficient is determined to be 2.04 x 10(-7) cm(2) s(-1). The composite film shows good catalytic activities for the reduction of nitrite (NO2-) in acidic solution and the catalytic mechanisms are described. The modified electrode provides a linear response for NO2- in the concentration range of 1.0 x 10(-4) to 1.0 x 10(-7) mol L-1 by differential pulse adsorptive stripping voltammetry with a correlation coefficient of 0.9965. The detection limit (three times the signal blank/slope) was 2.0 x 10(-8) mol L-1. The modified electrode was used for the determination of NO2- in wastewater.