Modified Carbon Ionic Liquid Electrode Research Articles

Simultaneous electrochemical determination of guanosine and adenosine with graphene–ZrO2 nanocomposite modified carbon ionic liquid electrode

In this paper an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was fabricated and used as the basal electrode, which was further modified by graphene (GR) and ZrO2 nanoparticle with chitosan (CTS) film to immobilize the nanocomposite. The modified electrode was denoted as CTS–GR–ZrO2/CILE and further used for the simultaneous detection of adenosine and guanosine. Electrochemical performances of the modified electrode were greatly enhanced due to the presence of GR–ZrO2 nanocomposite, and the direct electro-oxidation behaviors of adenosine and guanosine were carefully investigated. Both adenosine and guanosine exhibited an increase of the oxidation peak currents with the negative shift of the oxidation peak potentials on the modified electrode, which indicated the electrocatalytic activity of GR–ZrO2 nanocomposite on the electrode surface. Electrochemical parameters of adenosine and guanosine on CTS–GR–ZrO2/CILE were calculated respectively, and a new electroanalytical method for the simultaneous determination of adenosine and guanosine was further established with the peak-to-peak separation (ΔEp) as 0.225V. The proposed method was successfully applied to detect adenosine and guanosine in human urine samples with satisfactory results.

Facile electrocatalytic oxidation of ethanol using Ag/Pd nanoalloys modified carbon ionic liquid electrode

The electrocatalytic oxidation of ethanol in alkaline medium has been studied using Ag/Pd bimetallic nanoparticles modified carbon ionic liquid electrode (Ag/PdCILE). The electrochemical characterizations were performed using cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results show that the electrode reveals excellent characteristics such as high catalytic activity, stability, tolerance toward poisoning effects (even at very high ethanol concentrations) and capacity for electrooxidation of ethanol in alkaline medium. The results show that this electrode is very attractive for application in direct ethanol fuel cells.

Electrodeposited Graphene and Gold Nanoparticle Modified Carbon Ionic Liquid Electrode for Sensitive Detection of Rutin

A carbon ionic liquid electrode (CILE) was prepared by using ionic liquid 1-hexylpyridinium hexafluorophosphate (HPPF6) as the binder and the modifier, and then it was further decorated with gold nanoparticles and graphene (GR) using step by step electrochemical method to get a modified electrode denoted as GR/Au/CILE. Electrochemical performance of GR/Au/CILE was greatly enhanced due to the presence of nano-gold and GR. Different electrochemical methods such as cyclic voltammetry, differential pulse voltammetry and chronocoulometry were used to investigate the electrochemical behaviors of rutin on GR/Au/CILE with the electrochemical parameters calculated. Under the optimal conditions the oxidation peak current of rutin was proportional to its concentration in the range of 8.0 × 10–8-8.0 × 10–5 mol/L with the detection limit of 2.55 × 10–8 mol/L (3σ). The proposed method was applied to the analysis of rutin tablet with satisfactory results.

Nanomolar simultaneous determination of levodopa and serotonin at a novel carbon ionic liquid electrode modified with Co(OH)2 nanoparticles and multi-walled carbon nanotubes

A novel modified carbon ionic liquid electrode is prepared as an electrochemical sensor for simultaneous determination of levodopa (l-dopa) and serotonin (5-HT). The experimental results suggest that a carbon ionic liquid electrode modified with multi-walled carbon nanotubes and cobalt hydroxide nanoparticles, and coated with Nafion (Nafion/Co(OH)2–MWCNTs/CILE), accelerates the electron transfer reactions of l-dopa and 5-HT. In addition it shows no significant interferences of uric acid and ascorbic acid as electroactive coexistent compounds with l-dopa and 5-HT in biological systems. The fabricated sensor revealed some advantages such as convenient preparation, good stability and high sensitivity toward 5-HT and l-dopa determination. The DPV data showed that the obtained anodic peak currents were linearly dependent on the l-dopa and 5-HT concentrations in the range of 0.25–225 and 0.05–75μmolL−1, respectively. The applicability of the modified electrode was demonstrated by simultaneous determination of 5-HT and l-dopa in human serum.

Electrochemical DNA Biosensor Based on Graphene and TiO2 Nanorods Composite Film for the Detection of Transgenic Soybean Gene Sequence of MON89788

AbstractBased on graphene (GR), TiO2 nanorods, and chitosan (CTS) nanocomposite modified carbon ionic liquid electrode (CILE) as substrate electrode, a new electrochemical DNA biosensor was effectively fabricated for the detection of the transgenic soybean sequence of MON89788. By using methylene blue (MB) as hybridization indicator for monitoring the hybridization with different ssDNA sequences, the differential pulse voltammetric response of MB on DNA modified electrodes were recorded and compared. Due to the synergistic effects of TiO2 nanorods and GR on the electrode surface, the electrochemical responses of MB were greatly increased. Under optimal conditions the differential pulse voltammetric response of the target ssDNA sequence could be detected in the range from 1.0×10−12 to 1.0×10−6 mol/L with a detection limit of 7.21×10−13 mol/L (3σ). This electrochemical DNA biosensor was further applied to the polymerase chain reaction (PCR) product of transgenic soybeans with satisfactory results.

Silver‐Palladium Nanoalloys Modified Carbon Ionic Liquid Electrode with Enhanced Electrocatalytic Activity Towards Formaldehyde Oxidation

AbstractElectrocatalysis of the oxidation of formaldehyde on silver‐palladium‐modified carbon ionic liquid electrode (AgPd/CILE) was investigated in 0.1 M NaOH. The electrochemical performance of the AgPd/CILE was compared with those of Pd/CILE and Ag/CILE. Ag plays an important role in the catalytic performance of AgPd nanocatalyst and yields an excellent antifouling effect. Amperometric measurements showed that AgPd/CILE is a promising sensor for the detection of formaldehyde in the range of 10.0 µM–70.0 mM with a sensitivity of 240.6 µA mM−1 cm−2 and a detection limit of 2 µM. The method is free from interference of methanol, ethanol and formic acid.

Poly(methylene blue) functionalized graphene modified carbon ionic liquid electrode for the electrochemical detection of dopamine

An ionic liquid 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was used as the substrate electrode and a poly(methylene blue) (PMB) functionalized graphene (GR) composite film was co-electrodeposited on CILE surface by cyclic voltammetry. The PMB–GR/CILE exhibited better electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behavior of dopamine (DA) was further investigated by cyclic voltammetry and a pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔEp) as 0.058V in 0.1molL−1 pH 6.0 phosphate buffer solution, which proved a fast quasi-reversible electron transfer process on the modified electrode. Electrochemical parameters of DA on PMB–GR/CILE were calculated with the electron transfer number as 1.83, the charge transfer coefficients as 0.70, the apparent heterogeneous electron transfer rate constant as 1.72s−1 and the diffusional coefficient (D) as 3.45×10−4cm2s−1, respectively. Under the optimal conditions with differential pulse voltammetric measurement, the linear relationship between the oxidation peak current of DA and its concentration was obtained in the range from 0.02 to 800.0μmolL−1 with the detection limit as 5.6nmolL−1 (3σ). The coexisting substances exhibited no interference and PMB–GR/CILE was applied to the detection of DA injection samples and human urine samples with satisfactory results.

Highly sensitive electrochemical detection of adenine on a graphene-modified carbon ionic liquid electrode

A new electrochemical method for the sensitive detection of adenine was established on a chitosan (CTS)- and graphene (GR)-modified carbon ionic liquid electrode (CILE). CILE was prepared by mixing 1-butylpyridinium hexafluorophosphate (BPPF6) and paraffin with graphite powder. Due to the synergistic effects of GR, CILE, and the interaction of GR with IL on the electrode surface, the electrochemical performance of CTS/GR/CILE were greatly enhanced. Electrochemical behaviors of adenine on the modified electrode was investigated with a single well-defined oxidation peak appeared. The electrochemical reaction of adenine was an adsorption-controlled irreversible process, and the electrochemical parameters were further calculated. Under the optimal conditions, the oxidation peak current was proportional to adenine concentration in the range from 1.0 nmol L−1 to 70.0 μmol L−1 with a detection limit of 0.286 nmol L−1 (3σ) by differential pulse voltammetry. The established method showed the advantages such as good selectivity, stability, and repeatability.

Electrochemical DNA biosensor for the detection of Listeria monocytogenes with dendritic nanogold and electrochemical reduced graphene modified carbon ionic liquid electrode

A new electrochemical DNA biosensor was fabricated by using a dendritic gold nanoparticles and electrochemical reduced graphene (GR) composite modified carbon ionic liquid electrode (CILE) as the platform. Ionic liquid 1-butylpyridinium hexafluorophosphate was used as the binder for the preparation of CILE and GR film was further decorated on the CILE surface by electrochemical reduction. Then the dendritic nanogold was electrodeposited on the surface of GR/CILE to get a modified electrode as Au/GR/CILE, which was further used for the formation of mercaptoacetic acid self-assembling film. The amino modified ssDNA probe sequence was covalently linked with mercaptoacetic acid to get the ssDNA modified electrode for the further hybridization. Methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction after hybridized with the target ssDNA. Under the optimal conditions the specific Listeria monocytogenes hly ssDNA sequences could be detected by measuring the differential pulse voltammetric responses of the accumulated MB molecules on dsDNA molecules. The linear concentration range was achieved from 1.0×10−12 to 1.0×10−6mol/L with the detection limit as 2.9×10−13mol/L (3σ). This electrochemical DNA sensor exhibited excellent selectivity with the good discrimination ability of one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of L. monocytogenes hly gene that extracted from deteriorated fish was successfully detected, which indicated that this electrochemical DNA sensor could be further used for the detection of specific ssDNA sequence in real biological samples.

Sensitive Electrochemical Determination of Catechol with a Graphene Modified Carbon Ionic Liquid Electrode

AbstractIn this paper a graphene (GR) modified carbon ionic liquid electrode (CILE) was fabricated and used as the voltammetric sensor for the sensitive detection of catechol. Due to the specific physicochemical characteristics of GR such as high surface area, excellent conductivity and good electrochemical properties, the modified electrode exhibits rapid response and strong catalytic activity with high stability toward the electrochemical oxidation of catechol. A pair of well‐defined redox peaks appeared with the anodic and the cathodic peak potential located at 225 mV and 133 mV (vs.SCE) in pH 6.5 phosphate buffer solution, respectively. Electrochemical behaviors of catechol on the GR modified CILE were carefully investigated and the electrochemical parameters were calculated with the results of the electrode reaction standard rate constant (ks) as 1.24 s−1, the charge transfer coefficient (α) as 0.4 and the electron transfer number (n) as 2. Under the selected conditions the differential pulse voltammetric peak current increased linearly with the catechol concentrations in the range from 1.0 × 10‐7 to 7.0 × 10−4mol L‐1 with the detection limit as 3.0 × 10−8mol L‐1 (3σ). The proposed method was further applied to the synthetic waste water samples determination with satisfactory results

Application of Fe3O4 mesoporous sphere modified carbon ionic liquid electrode as electrochemical hemoglobin biosensor

A new electrochemical hemoglobin (Hb) biosensor was constructed based on a Fe3O4 mesoporous spheres modified carbon ionic liquid electrode (CILE), which showed excellent electrocatalytic ability towards the reduction of trichloroacetic acid. CILE was prepared by using N-hexylpyridinium hexafluorophosphate (HPPF6) as the modifier and the binder in the carbon paste. Ultraviolet-visible and Fourier transform infrared spectroscopic results indicated that Hb molecules retained the native structure in the chitosan and Fe3O4 mesoporous spheres composite film. Electrochemical results indicated that a pair of well-defined redox peaks appeared in 0.1mol/L phosphate buffer solution (PBS) with the formed potential (E0′) as −0.287V (vs. SCE), indicating that the direct electron transfer of Hb in the composite film was realized. Electrochemical behaviors of Hb were carefully investigated with the electrochemical parameters such as electron transfer coefficient (α), electron transfer number (n), and heterogeneous electron transfer rate constant (ks) calculated. Due to the specific characteristics of Fe3O4 mesoporous spheres present on the electrode surface, the electron transfer rate of Hb was greatly promoted. The Hb modified electrode exhibited excellent electrocatalytic properties with wider linear range and lower detection limit.

Electrochemical oxidation of adenosine-5′-triphosphate on a chitosan–graphene composite modified carbon ionic liquid electrode and its determination

In this paper a new electrochemical method was proposed for the determination of adenosine-5′-triphosphate (ATP) based on a chitosan (CTS) and graphene (GR) composite film modified carbon ionic liquid electrode (CTS–GR/CILE). CILE was fabricated by using ionic liquid 1-butyl-3-methylimidazolium dihydrogen phosphate ([BMIM]H2PO4) as the binder, which was further modified by GR and CTS composite. The modified electrode exhibited an excellent electrocatalytic activity toward the oxidation of ATP with the increase of the oxidation peak current and the decrease of the oxidation peak potential. The electrochemical parameters of ATP on CTS–GR/CILE were calculated with the electron transfer coefficient (α) as 0.329, the electron transfer number (n) as 2.15, the apparent heterogeneous electron transfer rate constant (ks) as 3.705×10−5s−1 and the surface coverage (ΓT) as 9.33×10−10molcm−2. Under the optimal conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0×10−6 to 1.0×10−3M with the detection limit of 0.311μM (S/N=3). The proposed electrode showed excellent reproducibility, stability, anti-interference ability and further successfully applied to the ATP injection sample detection.

Voltammetric determination of norepinephrine in the presence of acetaminophen using a novel ionic liquid/multiwall carbon nanotubes paste electrode

A novel multiwall carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of norepinephrine (NP). MWCNTs/CILE was prepared by mixing hydrophilic ionic liquid, 1-methyl-3-butylimidazolium bromide (MBIDZBr), with graphite powder, MWCNTs, and liquid paraffin. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of NE. The electron transfer coefficient, diffusion coefficient, and charge transfer resistant (Rct) of NE at the modified electrode were calculated. Differential pulse voltammetry of NE at the modified electrode exhibited two linear dynamic ranges with slopes of 0.0841 and 0.0231μA/μM in the concentration ranges of 0.3 to 30.0μM and 30.0 to 450.0μM, respectively. The detection limit (3σ) of 0.09μM NP was achieved. This modified electrode exhibited a good ability for well separated oxidation peaks of NE and acetaminophen (AC) in a buffer solution, pH 7.0. The proposed sensor was successfully applied for the determination of NE in human urine, pharmaceutical, and serum samples.

Electrochemistry of horseradish peroxidase entrapped in graphene and dsDNA composite modified carbon ionic liquid electrode

In this paper, a graphene (GR) and double-stranded DNA (dsDNA) composite material was prepared and used for the immobilization of horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE). Direct electrochemistry and bioelectrocatalysis of HRP incorporated in the composite film were carefully investigated. The presence of the dsDNA–GR biocomposite film on the electrode surface could provide a specific microenvironment for HRP with its direct electron transfer rate greatly enhanced on the electrode, which could be attributed to the synergistic contributions of the materials used. Cyclic voltammetric results exhibited that a pair of well-defined quasi-reversible redox peaks was observed on Nafion/HRP–dsDNA–GR/CILE in 0.1mol/L pH 3.0 phosphate buffer solution with the formal potential (E0′) as −0.193 V (vs. SCE), which was the typical characteristics of the heme Fe(III)/Fe(II) redox couple. The electrochemical parameters, such as the electron transfer coefficient (α) and the electron transfer rate constant (ks) of HRP in the dsDNA–GR composite modified electrode were calculated with the results as 0.46 and 0.495s−1, respectively. The fabricated HRP modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid over the concentration range of 1.0–21.0mmol/L with the detection limit of 0.133mmol/L (3σ). So the modified electrode provided a potential platform for the third-generation electrochemical biosensor.

Electrochemical detection of hydroquinone with a gold nanoparticle and graphene modified carbon ionic liquid electrode

An ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified carbon paste electrode was fabricated and used as the substrate electrode. Then a gold nanoparticle and graphene (GR) composite film was co-electrodeposited on the carbon ionic liquid electrode (CILE) surface by immersing CILE in the graphite oxide and tetrachloroauric acid dispersion solution with cyclic voltammetric reduction. The fabricated Au–GR/CILE exhibited good electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behaviors of hydroquinone (HQ) were further investigated on the modified electrode by cyclic voltammetry and differential pulse voltammetry. A pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔEp) as 0.077V in 0.1mol/L pH 2.5 PBS, indicating a fast quasi-reversible electron transfer process. The result could be attributed to the presence of high conductive Au–GR nanocomposites on the electrode surface. The electrochemical parameters of HQ on the Au–GR/CILE were calculated and the experimental conditions were optimized. Under the optimal conditions, the linear relationship between the oxidation peak current of HQ and its concentration can be obtained in the range from 0.06μmol/L to 800.0μmol/L with the detection limit as 0.018μmol/L (3σ). The coexisting catechol exhibited no interference and Au–GR/CILE was applied to the detection of HQ in synthetic wastewater samples with satisfactory results.

Electrochemically reduced graphene modified carbon ionic liquid electrode for the sensitive sensing of rutin

In this paper a graphene (GR) modified carbon ionic liquid electrode that was obtained by one-step potentiostatic electroreduction of a graphene oxide solution was described. The resulting electrode displayed excellent electrochemical performance due to the formation of highly conductive GR film on the electrode surface. Electrochemistry of rutin was carefully studied with a pair of well-defined redox peaks appeared in pH 2.5 buffer solution. Rutin exhibited a diffusion-controlled two-electron and two-proton transfer reaction on the modified electrode with the electrochemical parameters calculated. The reduction peak currents are linearly related to rutin concentration in the concentration range from 0.070 to 100.0μmol/L with a detection limit as low as 24.0nmol/L (3σ). The modified electrode displayed excellent selectivity with good stability, and was applied to the determination of rutin content in tablet, human serum and urine samples with satisfactory results.

Voltammetric detection of bisphenol a by a chitosan–graphene composite modified carbon ionic liquid electrode

In this paper 1-ethyl-3-methylimidazolium tetrafluoroborate based carbon ionic liquid electrode (CILE) was fabricated and further modified with chitosan (CTS) and graphene (GR) composite film. The fabricated CTS-GR/CILE was further used for the investigation on the electrochemical behavior of bisphenol A (BPA) by cyclic voltammetry and differential pulse voltammetry. A well-defined anodic peak appeared at 0.436V in 0.1mol/L pH 8.0 Britton–Robinson buffer solution, which was attributed to the electrooxidation of BPA on the modified electrode. The electrochemical parameters of BPA on the modified electrode were calculated with the results of the charge transfer coefficient (α) as 0.662 and the apparent heterogeneous electron transfer rate constant (ks) as 1.36s−1. Under the optimal conditions, a linear relationship between the oxidation peak current of BPA and its concentration can be obtained in the range from 0.1μmol/L to 800.0μmol/L with the limit of detection as 2.64×10−8mol/L (3σ). The CTS-GR/CILE was applied to the detection of BPA content in plastic products with satisfactory results.

Electrochemical immunoassay based on gold nanoparticles and reduced graphene oxide functionalized carbon ionic liquid electrode

In this paper, a gold nanoparticle, reduced graphene oxide (R-GO) and poly(l-Arginine) composite material modified carbon ionic liquid electrode (CILE) was used as the platform for the construction of a new electrochemical carcinoembryonic antigen (CEA) immunosensor. The poly(l-Arginine)/R-GO composite film was used to modify CILE to fabricate Arg/R-GO/CILE through electropolymerization of l-Arginine on R-GO/CILE. Gold nanoparticles (AuNPs) were adsorbed on the modified electrode to immobilize the CEA antibody and to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). By combining the specific properties such as the biocompatibility and big surface area of AuNPs, and the excellent electron transfer ability of R-GO and the high conductivity of CILE, the synergistic effects of composite increased the amounts of CEA antibody adsorbed on the electrode surface and then resulted in the great increase of the electrochemical responses. Under the optimal conditions, differential pulse voltammetric responses of [Fe(CN)6]3−/4− were proportional to CEA concentration in the range from 0.5 to 200ngmL−1 with the detection limit as 0.03ngmL−1 (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, and acceptable stability.

Electrochemistry and electrocatalysis of myoglobin on carbon coated Fe3O4 nanospindle modified carbon ionic liquid electrode

In this paper, carbon coated Fe3O4 nanospindles (C@Fe3O4 NSs) were synthesized by partial reduction of monodispersed hematite nanospindles with carbon coatings and applied to investigate the direct electrochemistry of myoglobin (Mb). A novel modified electrode was prepared by applying carbon coated Fe3O4 nanospindles, Mb, ionic liquid (IL), 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM]EtOSO3) and chitosan (CTS) step by step onto the surface of a carbon ionic liquid electrode (CILE) with another ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), as the binder. UV-Vis absorption and FT-IR spectra results indicated that Mb retained its native structure in the composite film. The electrochemical behavior of the CTS/IL/Mb/C@Fe3O4/CILE was investigated and a pair of well-defined redox peaks appeared, which indicated that the direct electron transfer of Mb was realized with the underlying electrode. The fabricated CTS/IL/Mb/C@Fe3O4/CILE showed good electrocatalytic activity in the reduction of trichloroacetic acid (TCA) with a linear range from 1.0 to 20.0 mM, which showed potential applications for fabricating novel electrochemical biosensors and bioelectronic devices.

Application of chitosan/Fe3O4 microsphere–graphene composite modified carbon ionic liquid electrode for the electrochemical detection of the PCR product of soybean Lectin gene sequence

In this paper a Fe3O4 microsphere, graphene (GR) and chitosan (CTS) nanocomposite material modified carbon ionic liquid electrode (CILE) was used as the platform for the construction of a new electrochemical DNA biosensor. The single-stranded DNA (ssDNA) probe was immobilized directly on the surface of the CTS/Fe3O4–GR/CILE, which could hybridize with the target ssDNA sequence at the selected conditions. By using methylene blue (MB) as the electrochemical indicator the hybridization reaction was investigated with the reduction peak current measured. By combining the specific properties such as the biocompatibility and big surface area of Fe3O4 microspheres, the excellent electron transfer ability of GR, the good film-forming ability of CTS and the high conductivity of CILE, the synergistic effects of nanocomposite increased the amounts of ssDNA adsorbed on the electrode surface and then resulted in the greatly increase of the electrochemical responses. Under the optimal conditions differential pulse voltammetric responses of MB were proportional to the specific ssDNA sequences concentration in the range from 1.0×10−12 to 1.0×10−6mol/L with the detection limit as 3.59×10−13mol/L (3σ). This DNA biosensor showed good stability and discrimination ability to one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction (PCR) product of soybean Lectin gene sequence was detected by the proposed method with satisfactory result, suggesting that the CTS/Fe3O4–GR/CILE was a suitable sensing platform for the sensitive detection of specific gene sequence.