Probing the surface chemistry of different oxidized MWCNT for the improved electrical wiring of cytochrome c nitrite reductase

•Thermal and chemical treatments of CNT modulate electrode interactions with ccNiR.•The complex cyclic voltammetry of ccNiR is partially deconvoluted.•Electrocatalytic activity is improved with lower oxygen surface coverages.

This work reports the evaluation of a set of multi-walled carbon nanotubes (MWCNT) presenting different surface chemistries, as interfaces for the direct electrochemistry of the multihemic nitrite reductase (ccNiR) from Desulfovibrio desulfuricans ATCC27774 (Dd). The carbon nanotubes (CNT) dispersions were prepared in aqueous media and deposited on pyrolytic graphite macroelectrodes, following a layer-by-layer methodology. The resulting MWCNT bed was coated with ccNiR and studied by cyclic voltammetry. Interestingly, although small non-catalytic cathodic waves were detected in all CNT bioconjugates, the complexity of these electrochemical signals was partially deconvoluted in some materials, the less acidic ones emphasizing the contribution of the catalytic centre. Consistently, these MWCNT were the most favourable for enzyme catalysis, highlighting the importance of the surface oxide functionalities to enzyme reactivity.

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