Fabrication of an electrochemical platform based on the self-assembly of graphene oxide–multiwall carbon nanotube nanocomposite and horseradish peroxidase: direct electrochemistry and electrocatalysis

A novel hybrid nanomaterial (GO–MWNTs) was explored based on the self-assembly of multiwall carbon nanotubes (MWNTs) and graphene oxide (GO). Compared with pristine MWNTs, such a nanocomposite could be well dispersed in aqueous solution and exhibit a negative charge. Driven by the electrostatic interaction, positively charged horseradish peroxidase (HRP) could then be immobilized onto GO–MWNTs at the surface of a glassy carbon (GC) electrode to form a HRP/GO–MWNT/GC electrode under mild conditions. TEM was used to characterize the morphology of the GO–MWNT nanocomposite. UV–vis and FTIR spectra suggested that HRP was immobilized onto the hybrid matrix without denaturation. Furthermore, the immobilized HRP showed enhanced direct electron transfer for the HRP–Fe(III)/Fe(II) redox center. Based on the direct electron transfer of the immobilized HRP, the HRP/GO–MWNT/GC electrode exhibited excellent electrocatalytic behavior to the reduction of H2O2 and NaNO2, respectively. Therefore, GO–MWNTs could provide a novel and efficient platform for the immobilization and biosensing of redox enzymes, and thus may find wide potential applications in the fabrication of biosensors, biomedical devices, and bioelectronics.