Layer-by-layer assembled film based on chitosan/carbon nanotubes, and its application to electrocatalytic oxidation of NADH

Multilayer films of multiwalled carbon nanotubes (MWNTs) were homogeneously and stably assembled on a glassy carbon (GC) electrode using the layer-by-layer (LBL) method based on electrostatic interaction between MWNTs (negatively charged) and a biopolymer chitosan (CHIT) (positively charged). Scanning electron microscopy (SEM) image of the resulting {CHIT/MWNTs}(9) film indicated that the substrate was mostly covered with MWNTs in the form of small bundles or single nanotubes. The multilayer film was used to study the electrocatalytic oxidation of NADH. The assembled {CHIT/MWNTs}(9)/GC electrode could decrease the oxidation overpotential of NADH by more than 350 V. The {CHIT/MWNTs}(9)/GC electrode exhibited a wide linear response range of 8 x 10(-7) to 1.6 x 10(-3) mol center dot L-1 with a correlation coefficient of 0.997 for the detection of NADH. The response time and detection limit (S/N = 3) were determined to be 3 s and 0.3 x 10(-6) mol center dot L-1, respectively. Another attractive characteristic was that the method was simple and the assembled {CHIT/MWNTs}(9)/GC electrode was highly stable.