Modified Carbon Ionic Liquid Electrode Research Articles

Electrochemistry of myoglobin on graphene–SnO2 nanocomposite modified electrode and its electrocatalysis

In this paper direct electrochemistry and electrocatalysis of myoglobin (Mb) immobilized on a graphene (GR)–SnO2 nanocomposite modified carbon ionic liquid electrode was reported. GR–SnO2 nanocomposite was synthesized by a simple solution method and further characterized by TEM and SEM, which exhibited large surface area beneficial for Mb immobilization. Spectroscopic results indicated Mb retained its native structure without denaturation after mixed with nanocomposite. Electrochemical investigation showed that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating that direct electron transfer of Mb with the underlying electrode was realized. The results could be attributed to the presence of GR–SnO2 nanocomposite that could enhance the electron transfer between the protein and the electrode. The Mb modified electrode exhibited good stability and catalytic activity to the electroreduction of NaNO2 in the concentration range from 0.2 to 350.0μmolL−1 with wider dynamic range and lower detection limit. Therefore the fabricated electrode has the potential application in the third-generation electrochemical biosensor.

Electrochemical Detection of Rutin on Mg2Al‐Cl Layered Double Hydroxide Modified Carbon Ionic Liquid Electrode

AbstractIn this paper a Mg2Al‐Cl layered double hydroxide (Mg2Al‐LDH) modified carbon ionic liquid electrode (CILE) was prepared and further used for the electrochemical detection of rutin. Cyclic voltammograms of rutin on Mg2Al‐LDH/CILE were recorded with a pair of well‐defined redox peaks appeared in pH 2.5 phosphate buffer solution, which was ascribed to the electrochemical reaction of rutin. Due to the presence of Mg2Al‐LDH on the electrode surface, the redox peak currents increased greatly and the electrochemical parameters were calculated. Under the optimal conditions the oxidation peak current was proportional to rutin concentration in the range from 0.08 μmol L‐1 to 800.0 μmol L‐1 with the detection limit on 0.0255 μmol L‐1 (3σ). The fabricated electrode showed good reproducibility and stability, which was successfully applied to rutin tablet samples determination.

Direct electrochemistry and electrocatalysis of hemoglobin on three-dimensional graphene modified carbon ionic liquid electrode

In this paper three-dimensional graphene (3D-GR) was directly formed on the surface of carbon ionic liquid electrode (CILE) by electrodeposition. By using 3D-GR/CILE as the substrate electrode, a new electrochemical biosensor was prepared by immobilization of hemoglobin (Hb) on the electrode surface with a chitosan film. Electrochemical investigation indicated that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Hb with the underlying electrode. The result can be ascribed to the porous structure of 3D-GR with high conductivity and big surface area. Based on the electrochemical data, the electron transfer coefficient (α) and the apparent heterogeneous electron transfer rate constant (ks) were calculated to be 0.426 and 1.864s−1, respectively. The modified electrode displayed good electrocatalytic activity to the reduction of trichloroacetic acid (TCA), and the catalytic reduction peak current had a good linear relationship to TCA concentration in the range from 0.4 to 26.0mmol/L with the detection limit of 0.133mmol/L (3σ). Therefore a new third-generation electrochemical Hb biosensor based on 3D-GR/CILE was constructed with good stability and reproducibility.

Application of nanosized gold and graphene modified carbon ionic liquid electrode for the sensitive electrochemical determination of folic acid

In this study a new electrochemical folic acid (FA) sensor was proposed by using gold nanoparticles (AuNPs) and graphene (GR) modified carbon ionic liquid electrode (CILE) as the working electrode. GR and AuNPs were directly electroreduced on the surface of CILE to get the modified electrode, which exhibited excellent electrochemical performances due to the specific characteristics including higher conductivity and larger surface area. The modified electrode showed excellent electrocatalytic ability to the oxidation of FA with an irreversible oxidation peak appeared at +1.05V (vs. SCE) in pH5.5 phosphate buffer solution. Electrochemical behaviors of FA on the modified electrode were carefully investigated with the electrochemical parameters calculated. Under the optimal conditions and by using differential pulse voltammetry, the oxidation peak currents were linear to FA concentration in the range from 0.01μmolL−1 to 50.0μmolL−1 with the detection limit as 2.7nmolL−1 (3σ). The proposed method was successfully applied to the FA tablet sample determination with satisfactory results.

Highly sensitive electrochemical sensor for dopamine with a double-stranded deoxyribonucleic acid/gold nanoparticle/graphene modified electrode

A highly sensitive electrochemical sensor for the detection of dopamine was realized with a double-stranded deoxyribonucleic acid/gold nanoparticles/graphene modified carbon ionic liquid electrode.

Application of titanium dioxide nanowires and electroreduced graphene oxide modified electrodes for the electrochemical detection of specific tlh gene sequence from Vibrio parahaemolyticus

Electrochemical DNA biosensor was prepared using electroreduced graphene oxide, titanium dioxide nanowires and chitosan modified carbon ionic liquid electrode for the detection of the specific tlh gene sequence.

Electrochemical deoxyribonucleic acid biosensor based on electrodeposited graphene and nickel oxide nanoparticle modified electrode for the detection of salmonella enteritidis gene sequence.

In this paper a new electrochemical DNA biosensor was prepared by using graphene (GR) and nickel oxide (NiO) nanocomposite modified carbon ionic liquid electrode (CILE) as the substrate electrode. GR and NiO nanoparticles were electrodeposited on the CILE surface step-by-step to get the nanocomposite. Due to the strong affinity of NiO with phosphate groups of ssDNA, oligonucleotide probe with a terminal 5'-phosphate group could be attached on the surface of NiO/GR/CILE, which could further hybridize with the target ssDNA sequence. Methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction. Under the optimal conditions the reduction peak current of MB was proportional to the concentration of salmonella enteritidis gene sequence in the range from 1.0×10(-13) to 1.0×10(-6)molL(-1) with a detection limit as 3.12×10(-14)molL(-1). This electrochemical DNA sensor exhibited good discrimination ability to one-base and three-base mismatched ssDNA sequences, and the polymerase chain reaction amplification product of salmonella enteritidis gene sequences were further detected with satisfactory results.

Sensitive electrochemical determination of oxalic acid in spinach samples by a graphene-modified carbon ionic liquid electrode

In this paper, a new electrochemical oxalic acid (OA) sensor based on graphene (GR)-modified carbon ionic liquid electrode (CILE) was proposed. The GR nanosheets were deposited on the surface of CILE by electroreduction with graphene oxide as precursor and electrocatalytic oxidation of OA on GR/CILE was further investigated. As compared with that of bare CILE, the oxidation peak current of OA on GR/CILE were greatly improved with the decrease of the oxidation potential. Electrochemical parameters of the electrooxidation of OA were calculated. Under the selected conditions, the oxidation peak currents increased with OA concentration in the range from 8.0 μM to 6.0 mM with the detection limit as 0.48 μM (3σ). The proposed method exhibited higher sensitivity and wider linear range, which was applied to determination of OA concentration in spinach samples with satisfactory results.

Electrochemical sensor for transgenic maize MON810 sequence with electrostatic adsorption DNA on electrochemical reduced graphene modified electrode

An electrochemical DNA biosensor for the detection of ssDNA sequence related to transgenic maize MON810 was fabricated with an electrochemical reduced graphene (ERG) modified carbon ionic liquid electrode (CILE) as the working electrode and methylene blue (MB) as the hybridization indicator. The probe ssDNA sequence was immobilized on the surface of ERG/CILE through electrostatic adsorption and the presence of ERG increased the adsorption amounts of probe ssDNA sequence on the electrode, which resulted in the corresponding increase of the reduction peak current of MB. Under the optimal conditions differential pulse voltammetric responses of MB were proportional to the concentration of target ssDNA sequences in the range from 1.0×10−11 to 1.0×10−6mol/L with the detection limit as 4.52×10−12mol/L (3σ). The sensor was further used for the detection of PCR products of transgenic maize samples with satisfactory results, which exhibited the advantages including simple and rapid procedure with the practical application.

Sensitive electrochemical detection of dopamine with a DNA/graphene bi-layer modified carbon ionic liquid electrode

A DNA and graphene (GR) bi-layer modified carbon ionic liquid electrode (CILE) was fabricated by an electrodeposition method. GR nanosheets were electrodeposited on the surface of CILE at the potential of −1.3V and then DNA was further deposited at the potential of +0.5V on GR modified CILE. Electrochemical performances of the fabricated DNA/GR/CILE were carefully investigated. Then electrochemical behaviors of dopamine (DA) on the modified electrode were studied with the calculated electrochemical parameters. Under the optimized conditions, a linear relationship between the oxidation peak current and the concentration of DA was obtained in the range from 0.1μmol/L to 1.0mmol/L with a detection limit of 0.027μmol/L (3σ). The modified electrode exhibited excellent reproducibility, repeatability, stability, validation and robustness for the electrochemical detection of DA. The proposed method was further applied to the DA injection solution and human urine samples determination with satisfactory results.

Electrochemical detection of rutin on nitrogen-doped graphene modified carbon ionic liquid electrode

In this paper nitrogen-doped graphene (NG) was synthesized and applied to modify an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). The fabricated NG/CILE exhibited excellent electrochemical performances. Electrochemical behaviors of rutin on NG/CILE were carefully investigated with a pair of well-defined redox peaks appeared, which was attributed to the presence of NG with electrocatalytic activity. Electrochemical parameters of rutin on NG/CILE were calculated with the values of charge transfer coefficient (α), electron transfer number (n) and electrode reaction standard rate constant (ks) as 0.57, 1.76 and 1.24s−1, respectively. Under the optimal conditions rutin could be detected in the concentration range from 7.0×10−10 to 1.0×10−5mol/L with the detection limit as 0.23nmol/L (3σ) by differential pulse voltammetry. The proposed method was further applied to the determination of rutin tablet samples with satisfactory results.

Application of N-doped graphene modified carbon ionic liquid electrode for direct electrochemistry of hemoglobin

Nitrogen-doped graphene (NG) was synthesized and used for the investigation on direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode as the substrate electrode. Due to specific characteristics of NG such as excellent electrocatalytic property and large surface area, direct electron transfer of Hb was realized with enhanced electrochemical responses appearing. Electrochemical behaviors of Hb on the NG modified electrode were carefully investigated with the electrochemical parameters calculated. The Hb modified electrode exhibited excellent electrocatalytic reduction activity toward different substrates, such as trichloroacetic acid and H2O2, with wider dynamic range and lower detection limit. These findings show that NG can be used for the preparation of chemically modified electrodes with improved performance and has potential applications in electrochemical sensing.

A novel electrochemical sensor based on a silver nanoparticle modified carbon ionic liquid electrode for selective and sensitive determination of levetiracetam in pharmaceutical tablets and blood plasma samples

An electrochemical sensor based on a silver nanoparticle (AgNP) modified carbon ionic liquid electrode (CILE) was prepared for the determination of ultra trace levels of levetiracetam (LEV) in human plasma and pharmaceutical tablets. The AgNPs were electrodeposited on the CILE surface using a double pulse potentiostatic technique, which can suitably control the size and morphology of AgNPs electrodeposited on the electrode. The AgNPs deposited on the CILE surface revealed an excellent electrocatalytic activity towards the oxidation of LEV. The sensor exhibited a fast response towards LEV with a linear concentration range of 1–300 ng mL−1 and a limit of detection of 0.7 ng mL−1. The possible interference from several common ions and drugs that usually accompany LEV was tested. The method was successfully applied to the determination of LEV content in real samples such as tablets and human plasma samples with good recovery, and the obtained results were checked by HPLC. The proposed sensor is suitable for routine analysis of LEV in plasma samples to monitor the therapeutic or toxic levels of LEV and for drug pharmacokinetic studies.

Electrocatalytic behaviors of silver–palladium nanoalloys modified carbon ionic liquid electrode towards hydrogen evolution reaction

Electrocatalytic activity of Ag/Pd bimetallic nanoparticles modified carbon ionic liquid electrode (Ag/Pd/CILE) has been studied towards the hydrogen evolution reaction (HER). The electrochemical characterizations were performed using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results showed that when Ag/Pd nanoalloys are used in the electrode structure, the overpotential for the HER shifts to more positive values compared to the case when pure Pd is present. It was also observed that both charge transfer resistance for HER and hydrogen adsorption resistance decreased with increasing the Ag content in Ag/Pd alloy up to 20%. The best result was obtained when Ag/Pd(20:80)/CILE was used. Also, incorporation of ionic liquid into the electrode structure improves the electrocatalytic behavior of Ag/Pd nanoalloys toward HER.

High sensitive simultaneously electrochemical detection of hydroquinone and catechol with a poly(crystal violet) functionalized graphene modified carbon ionic liquid electrode

By using potentiostatic method a poly(crystal violet) (PCV) and graphene (GR) composite was electrodeposited on the surface of carbon ionic liquid electrode (CILE) to obtain the modified electrode (denoted as PCV-GR/CILE). Due to the synergistic effects of PCV and GR, the fabricated electrode exhibited good electrochemical performances with increased conductivity and decreased interfacial resistances. Electrochemical behaviors of hydroquinone (HQ) and catechol (CC) were investigated on PCV-GR/CILE by cyclic voltammetry, which gave the separation of the oxidation peak potential of 112mV in pH 2.0 phosphate buffer solution. So the modified electrode was suitable for simultaneous electrochemical determination of HQ and CC in the mixture. Under the optimal conditions, the oxidation peak currents were proportional to the concentration of HQ in the range from 0.02μmol/L to 600.0μmol/L with the detection limit as 0.0062μmol/L (3σ), and to that of CC in the range from 0.04μmol/L to 600.0μmol/L with the detection limit as 0.013μmol/L (3σ). When simultaneously changing the concentration of the two isomers, the linear range was from 0.12μmol/L to 600.0μmol/L for HQ and 0.36μmol/L to 600.0μmol/L for CC with the detection limit as 0.033μmol/L (3σ) and 0.097μmol/L (3σ), respectively. The fabricated PCV-GR/CILE was further used to detect HQ and CC in artificial water sample with satisfactory results.

Electrochemical DNA Biosensor Based on Partially Reduced Graphene Oxide Modified Carbon Ionic Liquid Electrode for the Detection of Transgenic Soybean A2704‐12 Gene Sequence

AbstractIn this work a partially reduced graphene oxide (p‐RGO) modified carbon ionic liquid electrode (CILE) was prepared as the platform to fabricate an electrochemical DNA sensor, which was used for the sensitive detection of target ssDNA sequence related to transgenic soybean A2704‐12 sequence. The CILE was fabricated by using 1‐butylpyridinium hexafluorophosphate as the binder and then p‐RGO was deposited on the surface of CILE by controlling the electroreduction conditions. NH2 modified ssDNA probe sequences were immobilized on the electrode surface via covalent bonds between the unreduced oxygen groups on the p‐RGO surface and the amine group at the 5′‐end of ssDNA, which was denoted as ssDNA/p‐RGO/CILE and further used to hybridize with the target ssDNA sequence. Methylene blue (MB) was used as electrochemical indicator to monitor the DNA hybridization. The reduction peak current of MB after hybridization was proportional to the concentration of target A2704‐12 ssDNA sequences in the range from 1.0×10−12 to 1.0×10−6 mol/L with a detection limit of 2.9×10−13 mol/L (3σ). The electrochemical DNA biosensor was further used for the detection of PCR products of transgenic soybean with satisfactory results.

Electrodeposited nanogold decorated graphene modified carbon ionic liquid electrode for the electrochemical myoglobin biosensor

In this paper, a carbon ionic liquid electrode (CILE) was fabricated using ionic liquid 1-hexylpyridinium hexafluorophosphate as modifier, which was further in situ electrodeposited with graphene (GR) and gold nanoparticles step by step to get an Au/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the Au/GR/CILE surface with Nafion film to get the modified electrode denoted as Nafion/Mb/Au/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH 3.0 phosphate buffer solution with the formal potential (E 0′) located at −0.197 V (vs. saturated calomel electrode), which was the typical characteristics of Mb heme Fe(III)/Fe(II) redox couples. Thus, the direct electron transfer rate between Mb and the modified electrode was promoted due to the high conductivity and increased surface area of Au/GR nanocomposite present on electrode surface. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb-modified electrode showed excellent electrocatalytic activities towards the reduction of trichloroacetic acid and H2O2 with wider linear range and lower detection limit. Using GR and Au nanoparticles modified CILE, a new third-generation electrochemical Mb biosensor was constructed with good stability and reproducibility.

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

Abstract A carbon ionic liquid electrode (CILE) was prepared by using ionic liquid 1-hexylpyridinium hexafluorophosphate (HPPF6) as the binder and the modifier, which was further decorated with gold nanoparticles and graphene (GR) through 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 along with the electrochemical parameters calculated. Under the optimal conditions the oxidation peak current of rutin was proportional to its concentration in the range from 8.0 × 10−8 M to 8.0 × 10−5 M with the detection limit of 2.55 × 10−8 M (3σ). The proposed method was further applied to the rutin tablet samples detection with satisfactory results.

Nanomolar simultaneous determination of levodopa and melatonin at a new cobalt hydroxide nanoparticles and multi-walled carbon nanotubes composite modified carbon ionic liquid electrode

A novel modified carbon ionic liquid electrode (CILE) is prepared as an electrochemical sensor for simultaneous determination of levodopa (l-Dopa) and melatonin (Mel). The experimental results suggest that a carbon ionic liquid electrode modified with multi-walled carbon nanotubes and cobalt hydroxide nanoparticles accelerates the electron transfer reactions of l-Dopa and Mel. The fabricated sensor revealed some advantages such as convenient preparation, good stability and high sensitivity. The DPV data in 0.1M phosphate buffer solution (PBS) (pH 7.5) allowed a method to be developed for the determination of l-Dopa and Mel concentrations in the ranges 0.1–300 and 0.01–50μM, with the detection limits of 0.075 and 0.004μM, respectively. The proposed method was successfully applied to determinations of these compounds in some pharmaceutical and human urine samples.

Direct Electrochemistry and Electrocatalysis of Myoglobin with CoMoO4Nanorods Modified Carbon Ionic Liquid Electrode

nanorods and CTS. Electrochemical behaviors of Mb on theelectrode were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks from theheme Fe(III)/Fe(II) redox center of Mb appeared, which indicated that direct electron transfer between Mb andCILE was realized. Electrochemical parameters such as the electron transfer number (n), charge transfercoefficient ( α) and electron transfer rate constant ( k