Modulating the Geometry of the Carbon Nanofiber Electrodes Provides Control over Dopamine Sensor Performance

Abstract

One of the major challenges for in vivo electrochemical measurements of dopamine (DA) is to achieve selectivity in the presence of interferents, such as ascorbic acid (AA) and uric acid (UA). Complicated multimaterial structures and ill-defined pretreatments have been frequently utilized to enhance selectivity. The lack of control over the realized structures has prevented establishing associations between the achieved selectivity and the electrode structure. Owing to their easily tailorable structure, carbon nanofiber (CNF) electrodes have become promising materials for neurobiological applications. Here, a novel yet simple strategy to control the sensitivity and selectivity of CNF electrodes toward DA is reported. It consists of adjusting the lengths of CNF by modulating the growth phase during the fabrication process while keeping the surface chemistries similar. It was observed that the sensitivity of the CNF electrodes toward DA was enhanced with the increase in the fiber lengths. More importantly, the increase in the fiber length induced (i) an anodic shift in the DA oxidation peak and (ii) a cathodic shif t in the AA oxidation peak. As the UA oxidation peak remained unaffected at high anodic potentials, the electrodes with long CNFs showed excellent selectivity. Electrodes without proper fibers showed only a single broad peak in the solution of AA, DA, and UA, completely lacking the ability to discriminate DA. Hence, the simple strategy of controlling CNF length without the need to carry out any complex chemical treatments provides us a feasible and robust route to fabricate electrode materials for neurotransmitter detection with excellent sensitivity and selectivity.

Enhancing electrocatalytic activity in metallic thin films through surface segregation of carbon

“…We used DA and AA as analytes as we have studied the electrochemical activity of these biomolecules on carbon nanofibers grown on similar systems containing these adhesion layers in previous reports. 8,16 Both Cr/Si and Ti/Si before annealing could not detect either ascorbic acid or dopamine on their surface. After annealing, Ti/Si does not show any electrochemical activity (Fig.…”

Ni Drastically Modifies the Microstructure and Electrochemistry of Thin Ti and Cr Layers

“…The cyclic voltammograms for AA oxidation on CrNi and TiNi electrodes exhibited a peak around 465–500 mV, indicating the oxidation reaction from ascorbic acid to dehydroascorbic acid. The oxidation potential of AA is fairly anodically shifted than the observed oxidation peak position for CNFs . Similarly in the case of DA, a small peak at approximately 350 mV suggests a limited contribution from the CrNi and TiNi surfaces to the oxidation of DA to DAQ, with no corresponding reduction peak (Figure A,D).…”

“…The uncompensated resistance (Ru) was determined for each electrode in phosphate-buffered saline (PBS). The composition of PBS solution is given elsewhere . To evaluate the electrochemical activity of the electrodes in the PBS solution, dopamine hydrochloride (Sigma-Aldrich) and ascorbic acid (AA) from Merck were used.…”

“…Thin layers of Cr and Ti as adhesion layers covered by Ni as catalyst layer are among the commonly used interfacial metal stacks for growing carbon nanofibers (CNFs), graphene, nanowires, and semiconductor nanoparticles finding applications in various areas. − For growing carbon nanofibers, Ni provides the growth and nucleation sites through its surface step-edge sites acting as preferential growth centers for graphene layers and is known to act best as a catalyst at 600–700 °C. , Ti and Cr provide better adhesion capability by chemically binding with the substrate and through electrical contact owing to their partially filled d-orbital . Well known for their remarkable electrochemical sensing properties of biomolecules, , CNFs facilitate chemical interactions with the target molecules (ISR probes); nonetheless, the electrode’s electrochemical activity originates from both CNFs and interfacial metal layers. Unfortunately, the role of the interface in determining the electrochemical performance of CNF (and other) electrodes is often overlooked, with the electrochemical properties of the electrodes typically associated only with those of CNFs.…”

Correlation between microstructure and surface chemistry of carbon nanofibers grown using different adhesive layers

“…In conclusion, we have shown that (1) the microstructure of CNFs is strongly affected by the adhesive layer metallurgy, and (2) these structural changes have observable effects on the surface chemistry. Finally, this work provides a foundation for tailoring the features of CNFs for electroanalytical chemistry, which we have described in a separate work [42].…”