A highly sensitive electrochemical sensor made of a glassy carbon electrode (GCE) coated with a Langmuir-Blodgett film (LB) containing polyaniline (PAn) doped with p-toluenesulfonic acid (PTSA) (LB/PAn-PTSA/GCE) has been used for the detection of trace concentrations of Ag+. UV-vis absorption spectra indicated that the PAn was doped by PTSA. The surface morphology of the PAn LB film was characterized by atomic force microscopy (AFM). The electrochemical properties of this LB/PAn-PTSA/GCE were studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The LB/PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ag+ at pH 5.0 using linear scanning stripping voltammetry. Under the optimal experimental conditions, the stripping current was proportional to the Ag+ concentration over the range from 6.0 x 10(-10) mol L-1 to 1.0 x 10(-6) mol L-1, with a detection limit of 4.0 x 10(-1)0 mol L-1. The high sensitivity, selectivity, and stability of this LB/PAn-FTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag+ in water samples. (C) 2009 Elsevier Ltd. All rights reserved.