Electrochemical characterization of carbon black in different redox probes and their application in electrochemical sensing

• Thirteen grades of Carbon Black (N220, N234, N326, N330, N339, N375, N550, N660 and Lamp Black), including relatively newer grades (Printex®-200, Printex® G, Printex® XE-2B, Printex® Zeta) were analysed for their application in electrochemical sensors. • Carbon black coated electrode performance was studied by cyclic voltammetry using three different redox probes: ferri-/ferrocyanide (anionic probe molecules), ferrocenemethanol (neutral) and hexaamineruthenium (cationic). • Of the grades examined, N326 and Printex® XE-2B displayed the best electrocatalytic properties in terms of enhanced peak currents and lowered anodic overpotentials for the redox probes. Printex® XE-2B significantly improved the voltammetric anodic detection of reduced nicotinamide adenine dinucleotide (NADH) cofactor. • The presence of P-200 showed a statistically significant increased retention of the enzyme F-ALDH's activity, relative to that of the enzyme incubated with DMF, after 7 and 14 days' storage. • We demonstrate that the effects of modification on the electrode surface vary between both grades of carbon black and the redox probe used to study modification, indicating that characterisation with multiple redox probes should be standard practice for these studies. Carbon black - materials rich in carbon nanostructures - have been successfully applied as modifiers of electrochemical transducers, rivalling other carbon nanomaterials for cost and ease-of-use. Despite the remarkable promise of this nanomaterial, no study has yet comparatively characterised a wide range of different grades of carbon black for their utility in electrochemical sensors. Here, we explore several commonly-studied carbon black grades (N220, N234, N326, N330, N339, N375, N550, N660 and Lamp Black-101), alongside relatively newer grades (Printex®-200, Printex® G, Printex® XE-2B, and Printex® Zeta) for their application in electrochemical sensors. The effects of coating glassy carbon electrodes with carbon black on electrode performance were studied by cyclic voltammetry using three redox probes: ferri-/ferrocyanide (anionic probe molecules), ferrocenemethanol (neutral) and hexaammineruthenium (cationic). Raman Spectroscopy characterisation of the different grades associated a lower degree of graphitisation with superior electrode modifiers. Generally, modification increased the anodic peak current for ferri-/ferrocyanide probes; and lowered anodic potential for ferri-/ferrocyanide and hexaammineruthenium probes. Increases in peak current and potential observed at ferrocenemethanol are consistent with the increased tendency for this probe to adsorb to the surface of modified electrodes. N330 and Printex® XE-2B displayed the best electrocatalytic properties in terms of enhanced peak currents and lowered anodic overpotentials for the redox probes. CB grades were used to modify screen-printed carbon electrodes and the obtained sensors examined for anodic detection of reduced nicotinamide adenine dinucleotide (NADH) cofactor by cyclic voltammetry. Printex® XE-2B significantly improved the detection of NADH and was further used for chronoamperometric detection of NADH at low overpotentials. Grades N220, N375, N550 and P-G showed their suitability as enzyme scaffolds for sensor fabrication, as determined by their preservation of the activity of a NAD-dependent aldehyde dehydrogenase.