Nanostructured Geometries Strongly Affect Fouling of Carbon Electrodes

Abstract

Electrode fouling is a major factor that compromises the performance of biosensors in in vivo usage. It can be roughly classified into (i) electrochemical fouling, caused by the analyte and its reaction products, and (ii) biofouling, caused by proteins and other species in the measurement environment. Here, we examined the effect of electrochemical fouling [in phosphate buffer saline (PBS)], biofouling [in cell-culture media (F12-K) with and without proteins], and their combination on the redox reactions occurring on carbon-based electrodes possessing distinct morphologies and surface chemistry. The effect of biofouling on the electrochemistry of an outer sphere redox probe, [Ru­(NH3)6]3+, was negligible. On the other hand, fouling had a marked effect on the electrochemistry of an inner sphere redox probe, dopamine (DA). We observed that the surface geometry played a major role in the extent of fouling. The effect of biofouling on DA electrochemistry was the worst on planar pyrolytic carbon, whereas the multiwalled carbon nanotube/tetrahedral amorphous carbon (MWCNT/ta-C), possessing spaghetti-like morphology, and carbon nanofiber (CNF/ta-C) electrodes were much less seriously affected. The blockage of the adsorption sites for DA by proteins and other components of biological media and electrochemical fouling components (byproducts of DA oxidation) caused rapid surface poisoning. PBS washing for 10 consecutive cycles at 50 mV/s did not improve the electrode performance, except for CNF/ta-C, which performed better after PBS washing. Overall, this study emphasizes the combined effect of biological and electrochemical fouling to be critical for the evaluation of the functionality of a sensor. Thus, electrodes possessing composite nanostructures showed less surface fouling in comparison to those possessing planar geometry.

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

“…The progress in the engineering of carbon nanomaterials is revolutionizing the various aspects of the scientific world whether it be energy storage, bioimaging, wearable electronics, solar cells, drug delivery, or biosensing. − Plenty of research has been performed to study the properties of different forms of carbon nanomaterials such as carbon nanotubes, carbon nanofibers, carbon nanospikes, and carbon nanotube yarns as electrode materials for the neurobiological measurements. − These forms of carbon nanomaterials have been proved to be excellent materials for sensing neurochemicals by possessing one or other of the properties such as high sensitivity, wide potential window, good stability, and reversibility. However, in comparison to other forms, carbon nanofibers stand out as a superior sensor material due to their ability to retain the vertically aligned geometry with the fiber lengths reaching from tens of nanometers to tens of micrometers, better isolation among the nanostructures, improved signal-to-noise ratio due to the presence of underlying metal layers, and decreased capacitance. , By fine-tuning the fabrication parameters, the microstructure of CNFs can be controlled, providing the immense potential of modulating their properties selectively depending upon the target application.…”

Square-Wave Voltammetry of Human Blood Serum

“…Additionally, repetitive cycling of the potential signi cantly reduces the intensity of the response. Speci cally, in the second potential scan, the anodic voltammetric peaks are barely visible, indicating electrode surface fouling [33]. Under SWV conditions, due to the speed of the technique, the blocking of the electrode surface is less signi cant.…”

Electrodeposition of Cobalt Oxides on Carbon Nanotubes for Sensitive Bromhexine Sensing

“…A constant potential of 0.75 V was chosen for carrying out a BHC calibration. This value was selected to attain a high current from the BHC oxidation while avoiding the electrode fouling that can take place over time at higher operating potentials [36]. The current response was monitored as BHC was added to a phosphate buffer pH 5.5.…”