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Direct Electron Transfer Kinetics of Peroxidase at Edge Plane Sites of Cup-Stacked Carbon Nanofibers and Their Comparison with Single-Walled Carbon Nanotubes

Komori, Kikuo, Tatsuma, Tetsu, Sakai, Yasuyuki
Langmuir 2016 v.32 no.36 pp. 9163-9170
biosensors, carbon nanofibers, carbon nanotubes, electron transfer, energy conversion, graphene, hydrogen peroxide, microbial fuel cells, peroxidase, sodium dodecyl sulfate, surfactants
Electron transfer kinetics at the graphene edge site is of great interest from the viewpoints of application to sensing and energy conversion and storage. Here we analyzed kinetics of direct electron transfer of horseradish peroxidase (HRP) adsorbed through surfactant sodium dodecyl sulfate at cup-stacked carbon nanofibers (CSCNFs), which provide highly ordered graphene edges, and compared it with that at single-walled carbon nanotubes (SWCNTs), which consist of a rolled-up basal plane graphene. The heterogeneous electron transfer rate constant of the Fe²⁺/³⁺ couple of the HRP reaction center at CSCNFs (ca. 34.8 s–¹) was an order of magnitude larger than that at SWCNTs (ca. 4.7 s–¹). In addition, the overall rate constant of the electron transfer reaction from CSCNFs to HRP oxidized by H₂O₂ was higher than that from SWCNTs by a factor of 3. CSCNFs also allowed enhancement of the complex-formation reaction rate of HRP with H₂O₂, in comparison with that at SWCNTs. CSCNFs would therefore be applied to not only biosensors but also biofuel cells with enhanced performance.