Electrocatalytic oxidation and sensitive detection of cysteine at layer-by-layer assembled carbon nanotube-modified electrode

Electrocatalytic oxidation of cysteine (CySH) at multilayer films of carbon nanotube (CNT)-modified electrode was studied. The CNT-modified electrode was fabricated through layer-by-layer electrostatic deposition of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged shortened multi-walled carbon nanotubes (MWNTs) on glassy carbon (GC) electrode surface. The multilayer film was characterized by scanning electron microscopy and cyclic voltammetry. Effect of scan rate on CySH oxidation was also investigated. Sensitive detection for CySH at (PDDA/MWNT)5/GC electrode in 0.16 mol L−1 phosphate buffer solution (pH 7.4) was carried out. A linear calibration curve was observed in the range of 20 μmol L−1 to 1.3 mmol L−1 with differential pulse voltammetry (DPV). The detection limit (signal/noise, 3) of 0.3 μmol L−1 was obtained at 0.8 V in steady-current response.