Multi-walled Carbon Nanotube Electrodes Research Articles

In situ detection of heavy metal ions in sewage with screen-printed electrode-based portable electrochemical sensors.

The rapid development of industrial technologies continuously increases the heavy metal pollution of water resources. Recently, portable electrochemical analysis-based devices for detecting heavy metal ions have attracted much attention due to their excellent performance and low fabrication costs. However, it has proven difficult to accommodate complex testing needs in a cost-effective manner. To address these limitations, we propose a new system for the in situ detection of heavy metals in wastewater using an organic light-emitting diode-based panel to display data in real time and Bluetooth to transmit data to a smartphone for rapid analysis. The fabricated device integrates an in situ signal analysis circuit, a Bluetooth chip, a photocured 3D-printed shell, and an electrode sleeve interface. In addition, a fully screen-printed functional electrode plate containing chitosan/PANi-Bi nanoparticle@graphene oxide multi-walled carbon nanotubes is utilized for the rapid detection of heavy metal ions. This device can perform wireless data transmission and analysis and in situ signal acquisition and processing. The sensor exhibits a high sensitivity (Hg2+: 88.34 μA ppm-1 cm-2; Cu2+: 0.956 μA ppm-1 cm-2), low limit of detection (Hg2+: 10 ppb, Cu2+: 0.998 ppm) and high selectivity during the detection of copper and mercury ions in tap water under non-laboratory conditions, and the results of real-time tests reveal that parameters measured in the field and laboratory environments are identical. Hence, this small, portable, electrochemical sensor with a screen-printed electrode can be effectively used for the real-time detection of copper and mercury ions in complex water environments.

Continuous Determination of Glucose Using a Membraneless, Microfluidic Enzymatic Biofuel Cell.

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM−1cm−2.

Electrochemical sensor for determination of butylated hydroxyanisole (BHA) in food products using poly O-cresolphthalein complexone coated multiwalled carbon nanotubes electrode

In this study, we have reported an electrochemical sensor for the determination of butylated hydroxyanisole (BHA) by electropolymerization of O-cresolphthalein complexone (OC) over the multiwalled carbon nanotubes (MWCNTs). In order to confirm the surface morphology, oxidation states, functional groups and charge transfer property of POC/MWCNTs electrode, the resulting POC film with MWCNTs electrode was characterized by spectroscopy, microscopy, and electrochemical techniques. The fabricated electrode was evaluated for its electrochemical performance in oxidation of BHA and the study showed that at POC/MWCNTs electrodes BHA oxidation occurred at 0.27 V. POC/MWCNTs electrode has shown a linear range for the detection of BHA from 0.33 µM to 110 µM with the detection limit of 0.11 µM (S/N = 3). Amperometric determination of BHA was also done using chronoamperometric techniques and the result was found to be linear. The real time analysis of sensors is also validated by analysing the packed potato chips samples.

Preparation of CeO2-doped carbon nanotubes cathode and its mechanism for advanced treatment of pig farm wastewater

The effluent from conventional treatment process (including anaerobic digestion and anoxic-oxic treatment) for pig farm wastewater was difficult to treat due to its low ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/CODCr) (<0.1). In the present study, electro-Fenton (EF) was used to improve the biodegradability of the mentioned effluent and the properties of self-prepared CeO2-doped multi-wall carbon nanotubes (MWCNTs) electrodes were also studied. An excellent H2O2 production (165 mg L−1) was recorded, after an 80-min electrolysis, when the mass ratio of MWCNTs, CeO2 and pore-forming agent (NH4HCO3) was 6:1:1. Results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS) showed that addition of NH4HCO3 and the doping of CeO2 could increase the superficial area of the electrode as well as the oxygen reduction reaction (ORR) electro-catalytic performance. The BOD5/CODCr of the wastewater from the first stage AO process increased from 0.08 to 0.45 and CODCr reduced 71.5% after an 80-min electrolysis, with 0.3 mM Fe2+ solution. The non-biodegradable chemical pollutants from the first stage AO process were degraded by EF. The non-biodegradable pollutants identified by LC-MS/MS in the effluent from AO process including aminopyrine, oxadixyl and 3-methyl-2-quinoxalinecarboxylic acid could be degraded by EF process, with the removal rates of 81.86%, 34.39% and 7.13% in 80 min, and oxytetracycline with the removal rate of 100% in 20 min. Therefore, electro-Fenton with the new CeO2-doped MWCNTs cathode electrode will be a promising supplement for advanced treatment of pig farm wastewater.

Self-discharge of supercapacitors based on carbon nanotubes with different diameters

The self-discharge of supercapacitors was investigated using electrodes composed of multiwalled carbon nanotubes (MWCNTs) of three different diameters: 20, 30, and 50 nm, respectively. A combined self-discharge mechanism including both ohmic leakage and diffusion-controlled faradaic reaction was employed to fit the open circuit voltage (OCV) decays of the supercapacitors. The existence of both large inter-bundle pores and small intra-bundle pores in the MWCNT electrodes led to a two-stage diffusion-controlled faradaic reaction process - while the first stage can be described as a divided diffusion-controlled (DDC) process due to the diffusion of ions from both inter- and intra-bundle pores, and the second stage corresponds to a single diffusion-controlled (SDC) process mainly due to the diffusion of ions from the intra-bundle pores. The diffusion parameters obtained based on this model were consistent with the measured self-discharge rates which increased with the size of the MWCNTs. The results of this work demonstrate that electrode materials with wide pore size distributions may be associated with more complex self-discharge processes.

Inkjet Printed Multi-Walled Carbon Nanotube Sensor for the Detection of Lead in Drinking Water

The heavy metal lead has been a pollutant in our environment for many centuries and at low concentrations, lead can damage the human central nervous system, liver, kidney, and cardiovascular system and cause physiological and neurological problems in developing children who are most susceptible to lead poisoning. Lead in drinking water is currently regulated in the United States by the Environmental Protection Agency (EPA) with a maximum contamination level (MCL) of 15 ppb and the World Health Organization (WHO) has a MCL of 10 ppb of lead. Researches have identified high levels of lead in drinking water samples across the globe and the neurological development of young children is of great concern. A need for a rapid, sensitive, selective, reproducible, and affordable sensor for the trace detection of lead in true drinking water samples is needed. The detection of Pb2+ was performed using an inkjet printed multi-walled carbon nanotube (IJP-MW-CNT) electrode employing Osteryoung square wave stripping voltammetry (OSWV) as the detection method. The MW-CNT ink was prepared in water using bile salts (BS) as a surfactant, which were washed out extensively with DI water before using the printed MW-CNTs as electrodes. The IJP-MW-CNT electrode was used as the working electrode with a platinum wire and glass capillary Ag/AgCl as auxiliary and reference electrode, respectively. The electrodes performance was optimized in 0.1 M acetate buffer (pH = 4.3) and had a linear range of 5 – 50 ppb (R2 = 0.98235) a sensitivity of 20.15 nA/ppb and a limit of detection (LOD) of 1.632 ppb for Pb2+. The analytical applicability of electrode was tested in a real drinking water sample (i.e.) Cincinnati tap water with a linear range of 15 – 70 ppb (R2 = 0.98752) a sensitivity of 2.654 nA/ppb and a LOD of 1.269 ppb for Pb2+. The IJP-MW-CNT electrode’s results are comparable between different electrodes, and reproducible using the same electrode multiple times. The electrode can be easily and quickly be fabricated without modifications or in-situ additives needed, which makes up-scale production a feasible option. The sensor has been shown to perform well in an environmental sample (Cincinnati tap water) without any sample preparation or changes.The IJP-MW-CNT electrode can be implemented for the affordable and rapid detection of lead on-site in true water samples.

Infilling of highly ion-conducting gel polymer electrolytes into electrodes with high mass loading for high-performance energy storage

Full utilization of electrodes toward high-performance energy storage is challenging in cases where electrode/electrolyte interface is significant. From a practical perspective, this is particularly important in cases where a thick electrode or one with a high mass loading is needed. Here, we report an approach to increase the electrode performance by the infilling of a highly ion-conductive organic gel polymer electrolyte (EI-GPE, ionic conductivity ∼9.2mScm−1) into a multi-walled carbon nanotube (MWCNT) electrode with high mass loadings of up to 26mgcm−2 (or significant thicknesses of up to 443μm). Typical GPE (t-GPE) with a film-forming property but moderate ionic conductivity (1.2mScm−1) is then placed over the EI-GPE-filled electrode surface, resulted in flexible supercapacitor. Infilling of EI-GPE into MWCNT electrode provides a large-ion accessible interface that affords the increase in volumetric capacitance and energy density, about sixfold greater than that of the typical supercapacitors configured by sandwiching t-GPE as both electrolyte and the separator between a pair of electrodes. Importantly, this method enables scaling of the areal capacitance with electrode thickness (or mass loading of active material). A pouch type EI-SC provides stable performance after bending, suggesting it holds the promise of flexible energy storage.

Design of Slidable Polymer Networks: A Rational Strategy to Stretchable, Rapid Self-Healing Hydrogel Electrolytes for Flexible Supercapacitors.

Hydrogel electrolytes are of particular interest in the fabrication of flexible supercapacitors that are able to withstand deformation and physical damage. Nevertheless, there still exists a huge space in the design of hydrogel electrolytes with comprehensive performances including high processability, conductivity, mechanical strength, and self-healability. Herein, a slidable polymer network is constructed through the cross-linking reaction among commercially available polyethyleneimine (PEI), polyvinyl alcohol (PVA), and 4-formylphenylboronic acid (Bn) to generate PEI-PVA-Bn hydrogels, which have high adaptability to various electrolytes such as LiCl, NaCl, KCl, and ionic liquids. The as formed hydrogel electrolytes not only show excellent mechanical property (elongation at break up to 1223%, strength of 34.6 kPa) and self-healability (highest strain self-healing efficiency reaches 94.3% within 2 min) but also exhibit high conductivity (up to 21.49 mS cm-1). Flexible supercapacitors constructed by sandwiching the PEI-PVA-Bn-LiCl hydrogel electrolyte between two multiwalled carbon nanotube electrodes demonstrate a broadened operating potential window of 1.4 V, specific capacitance of 16.7 mF cm-2, high cycling stability up to 10 000 charge/discharge cycles, and excellent mechanical stability.

Analysis of Chlorogenic Acids in Coffee with a Multi-walled Carbon Nanotube Electrode

An electrochemical analysis using a multi-walled carbon nanotube (MWCNT) electrode is applied to examine chlorogenic acids (3-cafeoylquinic (3CQ), 4-cafeoylquinic (4CQ), 5-cafeoylquinic (5CQ), 3,4-dicafeoylquinic (34dCQ), 3,5-dicafeoylquinic (35dCQ), 4,5-dicafeoylquinic (45dCQ), 3-feruloylquinic (3FQ), 4-feruloylquinic (4FQ), and 5-feruloylquinic (5FQ) acid), which are the main ingredients of coffee polyphenols. The MWCNT electrode shows an excellent performance in the electrochemical quantification of chlorogenic acids. Cyclic voltammetry (CV) of all the chlorogenic acids shows redox peak pairs ranging between + 0.27 and + 0.31 V that are assigned to the redox reaction of the catechol group. Changes in the current due to individual chlorogenic acids at the peak potentials are proportional to their concentrations (3CQ, 4CQ, and 5CQ: linear range 0.4–194 μM, sensitivity 1.8 μA μM−1 cm−2; 34dCQ, 35dCQ, and 45dCQ: linear range 9.5–194 μM, sensitivity 4.3 μA μM−1 cm−2; and 3FQ, 4FQ, and 5FQ: linear range 5–194 μM, sensitivity 0.094 μA μM−1 cm−2). High-performance liquid chromatography (HPLC) analysis of coffee infusions shows that chlorogenic acids are almost entirely composed of 3CQ, 4CQ, and 5CQ. The total amounts of 3CQ, 4CQ, and 5CQ in coffee infusions obtained by HPLC show good agreement with those obtained by CV using the MWCNT electrode. This result indicates that the redox peak current can quantify the total amount of chlorogenic acid in a coffee infusion.

First Eurasian conference on nanotechnology, Baku, Azerbaijan photoelectrochemically-assisted bioanode constructed by Ru-complex and g-C3N4 coated MWCNT electrode

Abstract In this study, a novel photobioanode was constructed using a Ruthenium complex (Ru-complex) sensitized graphitic carbon nitride (g-C3N4) nanomaterial deposited on multi-walled carbon nanotubes (MWCNT). g-C3N4 coated MWCNT bearing Ru-complex acts as a platform for the immobilization of flavin adenine dinucleotide dependent glucose dehydrogenase (FADGDH). The formed photosensitive bioanode showed an enhancement in glucose oxidation current under visible light irradiation. The electrocatalytic current increase for in glucose oxidation are possibly due to the good electrical contacting of the immobilized FADGDH on the electrode surface and utilization of light energy. The spectroscopic properties of g-C3N4 and Ru-complex in dimethylformamide (DMF) were determined by UV–visible absorption spectra demonstrating the characteristic absorption peaks in the visible light region. Upon visible light illumination, the enzymatic photoanode revealed a prompt rise in photocurrent (ca. 1.44 μA cm−2) compared to the photoelectrode whithout enzyme (0.65 µA cm−2). Light irradiation of the bioanode improved the overall performance of the electrode as glucose oxidation was reinforced by photoelectrochemical (PEC) process.

Recyclable electrochemical supercapacitors based on carbon nanotubes and organic nanocrystals.

Sustainable energy storage devices are required in view of the current demand for environmentally friendly technology. We fabricated a fully recyclable electrochemical double-layer supercapacitor (EDLC), based on multiwalled carbon nanotube (MWCNT) electrodes, an organic nanocrystalline (ONC) dielectric membrane, and an aqueous electrolyte. The entire EDLC device was fabricated and recycled using simple solution processing. The pristine and recycled EDLC devices maintained high stability after 18 000 cycles in cyclic voltammetry testing. Our results advance a concept of sustainable energy storage devices that are easy to fabricate and recycle.

Self-Assembled Graphene/MWCNT Bilayers as Platinum-Free Counter Electrode in Dye-Sensitized Solar Cells.

We describe the preparation and properties of bilayers of graphene‐ and multi‐walled carbon nanotubes (MWCNTs) as an alternative to conventionally used platinum‐based counter electrode for dye‐sensitized solar cells (DSSC). The counter electrodes were prepared by a simple and easy‐to‐implement double self‐assembly process. The preparation allows for controlling the surface roughness of electrode in a layer‐by‐layer deposition. Annealing under N2 atmosphere improves the electrode's conductivity and the catalytic activity of graphene and MWCNTs to reduce the I3 − species within the electrolyte of the DSSC. The performance of different counter‐electrodes is compared for ZnO photoanode‐based DSSCs. Bilayer electrodes show higher power conversion efficiencies than monolayer graphene electrodes or monolayer MWCNTs electrodes. The bilayer graphene (bottom)/MWCNTs (top) counter electrode‐based DSSC exhibits a maximum power conversion efficiency of 4.1 % exceeding the efficiency of a reference DSSC with a thin film platinum counter electrode (efficiency of 3.4 %). In addition, the double self‐assembled counter electrodes are mechanically stable, which enables their recycling for DSSCs fabrication without significant loss of the solar cell performance.

A flexible, cost-effective, and eco-friendly solid state supercapacitor based on PVA/KCl/Carbon black nanocomposite

Much research is being done towards developing innovative materials and devices for energy production and storage. In this study, a less expensive and eco-friendly polymer nanocomposite (PNC), in combination with polyvinyl alcohol (PVA) and KCl/Carbon black (CB), at different weight percent was prepared and embedded between multi-walled carbon nanotube (MWCNT) electrodes for fabricating an all-solid-state supercapacitor (SC) device. Modification in electrode preparation and addition of KCl and CB to PVA/H3PO4 polymer electrolyte enhanced the ionic conductivity and initiated additional pseudo-reaction at electrode–electrolyte interface. Results showed that the SC with PVA/0.75 wt%KCl/0.3 wt%CB nanodielectric membrane has the highest energy storage capability for 0–1 V and reached a maximum energy density of 14.16 Wh/kg (at 1Ag−1) and power density of 1.38 KW/kg (at 5Ag−1). The PNC membrane showed excellent mechanical stability (up to 45 MPa under tensile loading). In addition, capacitance retention of 91.16% over 3000 cycles and an enhanced self-discharge of 60.63% were observed after 1000 min. The reliability of the same membrane was compared with commercially buyable Nafion®112 membrane.

Rapid detection of Salmonella enterica in raw milk samples using Stn gene-based biosensor.

In this study, a DNA-based nanosensor using specific NH2 labeled single standard probe was developed against stn gene of Salmonella enterica in milk samples. The single-stranded DNA probe was immobilized on carboxylated multiwalled carbon nanotube and gold nanoparticle (c-MWCNT/AuNP) electrode using 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC): N-hydroxy succinimide-based cross-linking chemistry. Electrochemical characterization was performed using cyclic voltammetry (CV) and Differential Pulse Voltammetry (DPV) techniques. The electrode surface at each step of fabrication was characterized using scanning electron microscopy. The sensitivity and lower limit of detection were found to be 728.42 (μA/cm2)/ng and 1.8pg/6μl (0.3pg/ml), respectively, with regression coefficient (R 2) of 0.843 using DPV. The sensor was further validated using raw and artificial milk samples, and results were compared with conventional methods of detection. The developed sensor was found to be highly sensitive and stable up to 6months, with only 10% loss of initial peak current in CV analysis on storage at 4°C.

Peroxydisulfate activation by positively polarized carbocatalyst for enhanced removal of aqueous organic pollutants

Multi-walled carbon nanotubes (MWCNTs)/peroxydisulfate (PDS) is a green oxidative system for abatement of aqueous organic pollutants, while the powder form and poor cycling performance of the catalyst limit its practical application. To solve these problems, fabricating a MWCNT cathode (negative polarization) to coupling carbocatalysis-driven PDS activation with electrosorption of organic pollutant was previously demonstrated to be a possible solution to these problems. To further improve the activation efficiency of PDS, positive polarization of MWCNT electrode (anode) was adapted to activate PDS for removing acyclovir and phenol in this work. Under a working voltage of 1.2 V, the MWCNT anode was more efficient than the MWCNT cathode and the non-polarized MWCNT electrode for PDS activation and removal of organic pollutants, owing to the enhanced attraction between S2O82− anions and anode. Although the positive/negative polarization of MWCNT electrode doesn't alter the nonradical mechanism involved in MWCNTs/PDS system, theoretical calculations suggest that different polarization affect the electron configuration and oxidative capacity of activated S2O82− bounded to MWCNTs differently, and that the adsorbed S2O82− with stretched S–O bond and much higher oxidative capacity than that in the case of non-polarized MWCNT electrode is responsible for the MWCNTs anode, while adsorbed S2O82− with stretched O–O bond and slightly higher oxidative capacity is responsible for the MWCNTs cathode. Finally, implications of operation parameters including electrode potential, energy cost, pH, etc. on the elimination efficiency by MWCNT anode/PDS system were investigated and the results suggest that the MWCNT anode/PDS is an efficient and economical metal-free electrochemical oxidative system for organic contaminants remediation.

Creating Scalable Faradaic Carbon Nanotube Electrodes with Mild Chemical Oxidation

The advancement of novel materials to ameliorate interfacial charge transfer properties will drastically improve energy storage, heterogeneous catalysis, and various other electrochemical applications. Here we discuss a facile method that can utilize the Faradaic capabilities of residual iron nanoparticle catalysts that are captured within Multi-walled Carbon Nanotubes (MWNT) post-synthesis, thereby correcting the difficulties associated with creating hybrid nanocomposite electrodes. Non-purified MWNTs, experience a chemical oxidation procedure in an acidic environment with KMnO4 to partly “unzip” the MWNTs and reveal the redox-active iron nanoparticles to the electrolyte. A consistent redox peak affiliated with the Fe2+/3+ transition is achieved during the MWNT oxidation procedure yielding a ~350% improvement in capacitance (>300 F g-1) when compared to purified MWNT electrodes (70 F g-1). While these materials solely may be applicable as energy storage electrodes, the integration of redox species within an inert carbon electrode will also provide new opportunities to accelerate heterogeneous charge transfer reactions.

Gold Nanoparticle Embedded Modified MWCNT Electrodes for Electrochemical Detection of Arsenic in Water

Email of corresponding author: dipban@iitg.ac.in : We focus on electrochemical detection of arsenite and/or arsenate in water using different kinds of electrodes made from gold nanoparticle embedded on substituted multiwall-carbon-nanotubes (MWCNT). The CNTs were functionalised with thiol groups by reaction with cysteamine. Following this, three different electrodes were fabricated using thiol substituted MWCNTs, gold nanoparticle (Au NP) embedded thiol substituted MWCNTs, and magnetite doped Au NP embedded MWCNTs. Subsequently, effect of Au NPs on the electrodes in the selectivity and sensitivity of the sensor was studied. The aforementioned experiments suggest that the affinity of the arsenite ions towards the thiol groups were found to be magnified by the integration of an optimal amount of Au NPs. Further, addition of magnetite particles in the CNT matrix made the sensor more sensitive towards arsenic detection. The working principles, mainly the change of the surface potential, of the electrodes were characterized by surface potential microscopy (SPOM) study using atomic force microscopy (AFM). The study helped in the miniaturization of the arsenic sensor using screen printed commercial electrode system with a modification of the working electrode based on requirement as stated before. Interestingly, we extracted the electrochemical response using an open source Arduino UNO based potentiostat unit, as shown in Fig. 1, to translate the concept into a portable electrochemical arsenic sensor. Keywords: Arsenite/Arsenate sensor, electrochemical, Screen printed electrode, Gold nanoparticle, Arduino UNO. Figure 1

Deposition of nickel hydroxide on water-dispersible multi-walled carbon nanotubes for enhanced electrochemical performance

Nanoparticles of Ni(OH)2 are deposited on multi-walled carbon nanotubes (MWNTs), via a hydrothermal reaction of Ni2+ in aqueous alkaline solution. In order to enhance the hydrophilicity of MWNTs and make MWNTs stably dispersed in water, MWNTs were modified by graphene quantum dot (GQD) via π―π interactions. The electrostatic interaction between Ni2+ and carboxyl group on GQD improves the combination between Ni2+ and MWNT, and the Ni(OH)2 nanoparticles are homogenously deposited on the GQD-modified MWNT (GQDMWNT). The Ni(OH)2/GQD·MWNT hybrids illustrate enhanced electrochemical performances compared with Ni(OH)2/MWNT. As a sensor, the Ni(OH)2/GQD·MWNT electrode exhibits the low detection limit of 0.2 μM to glucose with a wide linear concentration range. These results open the new way to the preparation of inorganic/carbonous nanohybrids with excellent electrochemical performance.

Creating Faradaic Carbon Nanotube Electrodes with Mild Chemical Oxidation

AbstractThe development of new materials to improve interfacial charge transfer characteristics will drastically improve energy storage, heterogeneous catalysis, and many other electrochemical applications. Here, we report a simple procedure that can harness the Faradaic nature of residual iron nanoparticle catalysts that endure within multi‐walled carbon nanotubes (MWNT) post‐synthesis, thereby alleviating the challenges associated with forging hybrid nanocomposite electrodes. Non‐purified MWNTs, undergo a chemical oxidation process in acidic conditions with KMnO4 to partially “unzip” the MWNTs and expose the redox‐active iron nanoparticles to the electrolyte. A stable redox peak associated with the Fe2+/3+ transition is achieved during the MWNT oxidation process yielding a ∼350 % increase in capacitance (&gt;300 F g−1) relative to purified MWNT electrodes (70 F g−1). While these materials solely may be pragmatic as energy storage electrodes, the integration of redox species within an inert carbon electrode will also provide new opportunities to accelerate heterogeneous charge transfer reactions.

Highly sensitive and selective detection of dopamine using overoxidized polypyrrole/sodium dodecyl sulfate-modified carbon nanotube electrodes

Dopamine (DA), an organic chemical neurotransmitter in the human brain, plays important roles in neuronal reward, motor control, and decision making. Thus, accurate quantification of DA concentration is essential for the investigation of various dopaminergic neural circuits and diagnosis of neurological diseases. Herein, we report an overoxidized polypyrrole/sodium dodecyl sulfate (SDS)-modified multi-walled carbon nanotube (OPPy/SDS-CNT) electrode which allows detection of DA with high resolution and selectivity. By using SDS as a dopant and sodium hydroxide (NaOH) as an oxidizing agent, highly sensitive detection of DA down to 5nM with a detection limit of 136pM is achieved. Moreover, due to the strong electrostatic interaction between the negatively-charged electrode and the positively-charged DA molecules, selective electrochemical detection of DA is successfully demonstrated in the presence of ascorbic acid (AA) and glucose (Glc). Lastly, by demonstrating in vitro detection of DA secreted from dopaminergic cells (PC12 cells) and examining biocompatibility of the electrode, we show the potential of our OPPy/SDS-CNT electrode as a promising candidate for a functional neural interface for in vitro and in vivo monitoring of DA concentrations.