Plasma-activated multi-walled carbon nanotube–polystyrene composite substrates forbiosensing

Abstract

Carbon nanotube–polymer composites have shown to be suitable materials for thefabrication of electrochemical transducers. The exposed surface of these materials iscommonly passivated by a very thin layer of the polymer component that buries theconductive carbon particles. Working with multi-walled carbon nanotube–polystyrene(MWCNT–PS) composite structures, it was previously described how a simple low poweroxygen plasma process produced an effective etching of the composite surface,thereby exposing the conductive surface of CNTs. This work shows how thisplasma process not only gave rise to a suitable composite conductive surface forelectrochemical sensing but simultaneously exposed and created a high density ofoxygen-containing functional groups at both the CNT and the PS components,without affecting the material’s mechanical stability. These chemical groups couldbe effectively modified for the stable immobilization of biological receptors. Adetailed chemical characterization of the plasma-activated composite surface waspossible using x-ray photoelectron spectroscopy. The material reactivity towards thetethering of a protein was studied and protein–protein interactions were thenevaluated on the modified composite transducers by scanning electron microscopy.Finally, an amperometric immunosensor approach for the detection of rabbitImmunoglobulin G target analyte was described and a minimum concentration of3 ng ml−1 was easily measured.