Chemically Modified Boron-doped Diamond Thin Film Electrode Nitrite Detect Nitrite

In this paper, chitosan modified boron doped diamond (BDD) thin film electrode and chitosan modified carbon nanotube (CNT) electrode are studied. During the experiment, the electrochemical properties of BDD electrode and CNT electrode are analyzed. The BDD electrode has a better electrochenmical stability, a wide potential window, and a very low background current. So it is the very electrode of develop potential and applicable value. CNT electrode has a better conductivity, a catalyst activity, and a large specific surface area, and these property can reduce overpotential. And it also can be used in electrochemical analysis extremely well. These two kinds of electrodes can be used as base electrodes, and their electrochemical properties could be improved to a large extent as long as they combine the advantages of high sensitivity and good selectivity of electrochemical modified electrode. In the experiment, BDD thin film is deposited on the pretreated Ta substrate by Hot Filament Chemical Vapor deposition (HFCVD). Oxidation treatment of the BDD thin film electrode which has been prepared is carried out, and BDD thin film electrode is modified by the method of covalent-bond reaction. By the radioactive of ultraviolet, both chitosan and cysteine can modify BDD electrode successfully. In the experiment, the electrochemical property of chitosan modified BDD electrode and cyclic voltammetry behavior of nitrite on the surface of the electrode. The result shows that the chitosan modified BDD electrode has better selectivity and sensitivity to nitrite in the KCl base solution of 0.1mo1/L and pH=5.0. There is a good linear relation between peak current and nitrite concentration in the concentration range of 5.0×10^-7—2.0×10^-3mol/L, and its detection limit can reach to 1.0×10^-7mol/L.As to the preparation of carbon nanotube electrode, the method of Plasma Enhanced Chemical Vapor Deposition (PECVD) is employed. Non-directly aligned Carbon nanotube is grown from methane and hydrogen gas mixture on the pretreated stainless steel (SS) substrate. This CNT/SS sheet acts as a base electrode modified chemically. In the same way, chitosan is used to modify CNT electrode by the method of covalent-bond reaction. electrochemical property of this electrode is studied by anodic voltammetry. The result is shown to be that the CS/CNT chemically modified electrode, which is used to detect nitrite, has better selectivity and adsorptivity in the 0.1 mo1/L, pH=6.0 base solution of KCl. A good linear relation between peak current and concentration emerges in the range of 2.0×10^-6—1.0×10^-3 mol/L, and its detecting limit is 3.0×10^-7 mol/L.Compare the electrochemical property of these two kinds of electrodes. The result shows that the chitosan modified BDD electrode has a better sensitivity, a wide linear range, a good stability and can analyze nitrite conveniently. This electrode also has a long useful time, and there is an excellent prospect for the application of this modified electrode in food industry.