Effect of solution pH and ionic strength on the stability of poly(acrylic acid)-encapsulated multiwalled carbon nanotubes aqueous dispersion and its application for NADH sensor.

The optimal conditions to prepare water-soluble, stable poly(acrylic acid)-wrapped multiwalled carbon nanotubes (PAA-MWNTs) complex is presented. PAA-MWNTs shows high stability within weak acid to weak basic pH condition. The complex also shows good endurance to moderate ionic strengths in the buffer solution. The PAA-MWNTs complex film-covered electrode demonstrates stable, excellent electrocatalytic activity to oxidize NADH, which makes it possible to prepare NADH sensor at a low potential of approximately 0.13 V (versus Ag/AgCl) with the linear range of 4-100 microM by differential pulse voltammetry.