Abstract: A simple immobilized method of chloroperoxidase(CPO) was reported, that is, 1 μL CPO solution was mixed with 2 μL carboxylated SWNTs[1 mg/mL, which was dispersed in 0.5%(mass fraction) Nafion], droped onto the surface of glass carbon(GC) electrode. The electrochemical behavior of the CPO/SWNTs modified GC electrode was investigated by cyclic voltammetry. A pair of well-defined redox peaks was observed in pH 5 phosphate buffer solutions. In contrast to no peaks for bare GC in CPO solution and only SWNTs coated electrode in phosphate buffer solutions, it is suggested that SWNTs promote the direct electron transfer between the CPO and the GC electrode. The redox peak current has no change in the scan rate range from 5 to 1000 mV/s. The formal potential is -300 mV. The peak separation is about 90 mV at the scan rate of 100 mV/s. Furthermore, the CPO/SWNTs modified GC electrode was used to catalyze chlorination of monochlorodimedone(MCD). A total turnover number of 4.0×10⁵ was obtained, indication of good catalysis efficiency

Key words: Chloroperoxidase, Carboxylated carbon nanotubes, Modified electrode, Monochlorodimedone, Electrocalalysis