The Preparation And Its Aplications Of Polyaniline Chemically Modified Electrodes

Since Diaz first reported that polypyrrole could be obtained from pyrrole by electrochemical oxidation on electrode in 1979, conductive polymers have been widely used in modified electrode. conductive polymers consist of conjugated electronic structures, which makes them having unique characters such as rigid chain structure, inmeltable, insoluble and environmentally stable. So they also were named one-dimension conductive polymers. Electronic conductivity of conductive polymer can raise more than 10 orders of magnitude by dope, showing metallicity. Electronic conductivity polyaniline can be reversibly altered by both oxidation/reduction and acid/base chemistries, so it have received considerable attention lately. Polyaniline have been utilized as chemical sensors, including biomolecular sensor, small organic molecule sensors and gas sensor. However, polyaniline and polyaniline membranes are not widely used as sensors for metal ions. In this thesis, we have done some work in this field and the main results are expressed as follows:1. 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 in the range between 6.0×10-10 mol·L-1 and 1.0×10-6 mol·L-1, with a detection limit of 4.0×10-10 mol·L-1. The high sensitivity, selectivity, and stability of this LB/PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag+ in natural water samples. 2. A novel mercury-free voltammetric sensor of Ti4+ was fabricated by Polyaniline doped with p-toluenesulfonic acid named PAn-PTSA/GCE. The electrochemical properties of this PAn-PTSA/GCE in solution containing Ti4+ were studied using Cyclic Voltammetry and Chronoamperometry. The electrode reaction mechanism of titanium on PAn-PTSA/GCE was discussed. The PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ti4+ at pH 4.0 using Differential Pulse Voltammetry. Under the optimal experimental conditions, the peak currents were proportional to the Ti4+ concentration in the range of 8.0 X 10-9 mol·L-1 and 4.2×10-7 mol·L-1, with a detecting limit of 4.0×10-9 mol·L-1. The high sensitivity and selectivity of this PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ti4+ in synthetical water samples.