Bioelectrocatalytic platforms based on chemically modified nanodiamonds by diazonium salt chemistry

•Electrografting of Azure A diazonium salt onto NDs/gold hybrid electrodes.•Azure A covalent modified NDs/gold electrodes with catalytic activity towards NADH oxidation.•Redox active Azure A electrografted films as NADH sensing platforms.•Electrochemically driven Azure A modified NDs for ethanol biosensing. Detonation nanodiamonds immobilized onto screen-printed gold electrodes have been modified with a phenothiazine (Azure A) by electrografting of the corresponding in situ generated diazonium salt in acidic medium in the presence of nitrite. The resulting disposable electrochemical platform has been extensively characterized, confirming that is very stable and highly reactive. It shows an excellent electrocatalytic activity towards the oxidation of substances of interest and can be employed to prepare bioelectrocatalytic platforms. Hence, as proof of concept, nicotinamide adenine dinucleotide (NAD+)-dependent alcohol dehydrogenase has been directly immobilized on the Azure A electroactive film to develop an ethanol biosensor based on the measurement of the enzymatically generated β-nicotinamide adenine dinucleotide (NADH). Considering the excellent results obtained, it can be concluded that the modification of electrodes with detonation nanodiamonds can be a good strategy to generate sensing and biosensing electrochemical devices. [Display omitted]