Electrocatalytic Discrimination between Dopamine and Norepinephrine at Graphite and Basal Plane HOPG Electrodes

Abstract

Understanding the regulatory mechanisms of neurotransmission is impossible without in vivo monitoring of neurotransmitters’ (NTs) transformation in the brain, and that can be performed by a variety of electrochemical methods. Close redox potentials of such NTs as catecholamines, however, impede their specific analysis in systems where they do co‐exist. Here, we studied the kinetics of dopamine and norepinephrine redox transformations on glassy carbon, micro‐structured spectroscopic graphite, and basal plane HOPG electrodes. We showed that in contrast to the “positive electrocatalysis” on porous microstructured graphite electrodes, “negative electrocatalysis” at the HOPG electrodes, displayed through slowing down of the reaction rate, allowed a ca. 0.1 V separation between dopamine and norepinephrine oxidations and individual detection of dopamine in the artificial cerebrospinal fluid. Dopamine could be detected within the 50 nM to 4 μM range with no interference from excesses of norepinephrine and ascorbic acid. The results suggest a new approach for design of the electrodes for specific analysis of dopamine in mixtures of structurally related NTs.

Electrocatalytic Oxidation of Water by OH−‐ and H2O‐Capped IrOx Nanoparticles Electrophoretically Deposited on Graphite and Basal Plane HOPG: Effect of the Substrate Electrode**

“…Thus, the analysis of the effect of capping ligands on the electrocatalytic performance of NPs-modified electrodes is apparently complicated by the nature of the conductive substrate support, which was already discussed to strongly contribute not only to the NP Fermi level but also to the surface dispersion and aggregation of NPs on the electrode surface. [38] The lower wettability (i. e., higher hydrophobicity) of spectroscopic Gr in combination with its highly micro-structured surface composed of graphitic flakes [54,55] enable electrophoretic deposition of IrO x NPs minimally aggregated and with a maximal specific electrocatalytic activity. Independently of the time of deposition, no solid IrO x NPs films could be formed on the Gr electrodes.…”

“…In the present work, electrocatalytic properties of IrO x NPs electrophoretically deposited onto two types of substrate electrodes, spectroscopic Gr that somehow approaches in its properties the edge-plane highly ordered pyrolytic graphite (HOPG), and basal plane HOPG, representing a stack of graphene layers and often considered as a first-approximation electrochemical 3D model of graphene, [49] were investigated. These electrode materials have distinctly different surface properties with respect to hydrophilicity/hydrophobicity, sur-face reactivity [50][51][52][53][54] and surface structural roughness. [55] While the atomically flat surface of HOPG is extremely useful as a substrate for AFM studies, [52,56,57] its reactivity is also very attractive for electrochemical applications.…”

“…[55] While the atomically flat surface of HOPG is extremely useful as a substrate for AFM studies, [52,56,57] its reactivity is also very attractive for electrochemical applications. [51][52][53][54] Cheap and easily renewable spectroscopic Gr, widely used in electroanalysis of small molecules and proteins due to its high-surface area enabling a higher surface coverage with adsorbates, [14,[58][59][60][61][62] has been already used for fabrication of IrO x nanocomposite electrodes. [31] These electrodes demonstrated the hitherto highest electrocatalytic current densities, of 43 mA cm À 2 at 1 V and pH 7, in OER.…”

Intercalation Lithium Cobalt Oxide for the Facile Fabrication of a Sensitive Dopamine Sensor

“…Various materials have been developed and immobilized on the surface of electrodes, including metal oxides or metal oxide-based nanoparticles and nanocomposites, [9,13,14] carbonbased nanomaterials (i. e. carbon nanotubes, [15,16] graphenes, [17][18][19][20] carbon fibers, [21,22] and HOPG [23,24] et al), polymeric materials [25,26] and ionic liquids [27,28] et al, exploring new materials which may have the adsorptive or catalytic behavior for the electrochemical detection of dopamine is still a trend. In addition, the controlled integration of some nanoparticles creates a class of multifunctional nanomaterials that are powerful for various applications, including in the fields of electrocatalysis and sensing.…”

Affinity of Electrochemically Deposited Sol–Gel Silica Films towards Catecholamine Neurotransmitters

“…It is widely-accepted that a suitable strategy to improve the selectivity of electrochemical detection could involve the use of modified electrodes able to interact more specifically with neurotransmitters. For this purpose it has been reported the use of polypyrrole films [ 10 ], nickel oxide nanoparticles, or carbon nanotubes within dihexadecylphosphate films [ 11 ], as well as carbon-modified electrodes [ 12 , 13 ]. To our knowledge, the use of silica-based materials for neurotransmitter detection has been restricted to their integration with carbon nanoparticles to enhance sensitivity [ 14 ].…”