Chemically reduced electrospun polyacrilonitrile–carbon nanotube nanofibers hydrogels as electrode material for bioelectrochemical applications

Nanosized fibers containing carbon nanotube (CNT) were produced by electrospinning from a DMF solution containing CNT and polyacrilonitrile (PAN). The resulting fibers form a felt like fiber tissue that was used as an electrode. The nitrile groups of these fibers were chemically reduced to amines groups that were protonated at pH 5. The resulting positively charged nanofibers swell in aqueous solutions increasing the exposed surface of CNT and facilitating the diffusion of small molecules and ions to the conducting CNTs. The electrochemical behavior and the morphology of as prepared and reduced nanofibers were characterized by cyclic voltammetry and scanning electron microscopy (SEM) respectively. In addition, the influence of the reduction process determining the amount of amino groups, was investigated. The biofunctionalization of the nanofiber tissue electrodes was carried out by activation of the amino groups via incubation in glutaraldehyde vapor. Then, an enzyme model, polyphenol oxidase (PPO), was chemically grafted onto the nanofiber surface. The efficient covalent binding of PPO onto PAN–NH2–CNT electrodes (1 × 1 cm size), was exemplified through the electro-enzymatic detection of catechol. The resulting sensitivity and maximum current values at saturated catechol concentration are 118 mA mol−1 L and 10.66 μA respectively, with a detection limit of 0.9 μmol L−1.