Using multi-walled carbon nanotubes to enhance coimmobilization of poly(azure A) and poly(neutral red) for determination of nicotinamide adenine dinucleotide and hydrogen peroxide

Coimmobilization of poly(azure A) (PAA) and poly(neutral red) (PNR) has been successfully performed and further enhanced by a multi-walled carbon nanotube (MWCNT) modified electrode. The PAA-PNR/MWCNTs hybrid composite is electroactive, pH-dependent, and stable in the electrochemical system. It shows electrocatalytic activity toward nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H₂O₂) with high current response and low overpotential. By amperometry, it shows a high sensitivity of 265.8 μA mM^-1cm^-2toward NADH (E_app.= +0.05 V). Linearity is estimated in a concentration range of 1 × 10^-6to 1.455 × 10^-3M with a detection limit of 1 × 10^-7M (S/N = 3). It shows a high sensitivity of 10.3 μA mM^-1cm^-2toward H₂O₂(E_app.= -0.25 V) with a linear concentration range of 8 × 10^-4to 1.91 × 10^-3M and a detection limit of 1 × 10^-6M (S/N = 3). By the result, it proves the coimmobilization and activity of PAA and PNR can be effectively enhanced by MWCNTs, suggesting a bifunctional sensor for determination of NADH and H₂O₂.