Graphene Modified Carbon Ionic Liquid Research Articles

A graphene modified carbon ionic liquid electrode for voltammetric analysis of the sequence of the Staphylococcus aureus nuc gene.

The authors describe a voltammetric method for the detection of the nuc ssDNA sequence originating from Staphylococcus aureus by using a carbon ionic liquid electrode modified with electrodeposited three-dimensional graphene (3DGR). Probe ssDNA was electrostatically adsorbed on the modified electrode by a potentiostatic method. The porous structure and large surface area of 3DGR greatly increase the amount of immobilized probe ssDNA on the interface, which is beneficial for the reaction with target ssDNA. By using Methylene Blue (MB) as the electrochemical probe, the reduction peak current of MB (best measured at -0.30V vs. SCE) can be used for detecting hybridization. The differential pulse voltammetric current of MB increases linearly in the 1.0 × 10-12mol L-1 to 1.0 × 10-6mol L-1 nuc concentration range, and the detection limit is 3.3× 10-13mol L-1 (at 3σ). The DNA sensor was successfully applied to the determination of the PCR product of the gene in pork. Graphical abstract Response of an electrochemical DNA biosensor based on the use of a carbon ionic liquid electrode modified with three-dimensional graphene. It enables sensitive voltammetric detection of the specific sequence of the Staphylococcus aureus nuc gene.

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.

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.

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.

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.

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.

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

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.