Free-standing Graphene/Poly(methylene blue)/AgNPs Composite Paper for Electrochemical Sensing of NADH

Highly flexible graphene/poly(methylene blue)/AgNPs composite paper was successfully prepared for amperometric biosensing of NADH. For this purpose, a dispersion including graphene oxide (GO), methylene blue (MB) and silver nanoparticles (AgNPs) was prepared and GO/MB/AgNPs paper was acquired by vacuum-filtration of this dispersion through a suitable membrane. After peeling it off from membrane, it was transformed to rGO/MB/AgNPs paper by performing reduction with hydriodic acid. In a three-electrode cell, which is containing 0.1M phosphate buffer solution (pH: 9.0), rGO/MB/AgNPs paper was used as working electrode and rGO/poly(MB)/AgNPs composite paper was generated by surface-confined electropolymerization of MB using successive cyclic voltammetry approach in a suitable potential window. Characterization of this composite paper was carried out by using scanning electron microscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction spectroscopy, Raman spectroscopy, four-point probe conductivity measurement and cyclic voltammetry techniques. Flexible rGO/poly(MB)/AgNPs composite paper has demonstrated high sensitivity, wide linear range and low detection limit for amperometric quantification of NADH.