Modified Carbon Ionic Liquid Electrode Research Articles

Direct electrochemistry of guanosine on multi-walled carbon nanotubes modified carbon ionic liquid electrode

A multi-walled carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of guanosine. CILE was prepared by mixing hydrophilic ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4), graphite powder and liquid paraffin together. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of guanosine and an irreversible oxidation peak appeared at 1.067 V (vs. SCE) with improved peak current. The electrochemical behavior of guanosine on the MWCNTs/CILE was carefully studied by cyclic voltammetry and the electrochemical parameters such as the charge transfer coefficient ( α) and the electrode reaction standard rate constant ( k s ) were calculated with the result as 0.66 and 2.94 × 10 −4 s −1, respectively. By using differential pulse voltammetry (DPV) as the detection method, a linear relationship was obtained between the oxidation peak current and the guanosine concentration in the range from 1.0 × 10 −7 to 4.0 × 10 −5 mol/L with the detection limit as 7.8 × 10 −8 mol/L (3 σ). The common coexisting substances showed no interferences to the guanosine detection and the modified electrode showed good ability to distinguish the electrochemical response of guanosine and adenosine.

Direct electrochemistry of hemoglobin immobilized in polyvinylalcohol and clay composite film modified carbon ionic liquid electrode

In this paper room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoro-phosphate (BMIMPF6) was used as binder to fabricate a carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on the surface of CILE with clay and polyvinyl alcohol (PVA) composite film by layer to layer method. UV-Vis and FT-IR spectra showed that Hb in the film retained the essential features of its native structure. Electrochemical experiments indicated that a pair of well-defined quasi-reversible redox peak was obtained in pH 7.0 Britton-Robinson (B-R) buffer solution. The reduction and oxidation peak potentials were located at -0.405 V and -0.274 V (vs. SCE) with the formal potential as -0.340 V, which was contributed to the electrochemical reaction of heme Fe(III)/Fe(II) redox couples. The results suggested that the direct electron transfer of Hb in the PVA/Clay film with the CILE was accomplished. The direct electrochemical behaviors of Hb were carefully studied with the electrochemical parameters calculated. The PVA/Clay/Hb modified CILE gave excellent electrocatalytic ability to the reduction of H2O2 and the apparent Michaelis-Menten constant (KMapp) value of Hb in the PVA/Clay film was calculated as 56.26 µmol L-1.

Direct Electrochemistry of Hemoglobin on Single‐Walled Carbon Nanotubes Modified Carbon Ionic Liquid Electrode and Its Electrocatalysis

AbstractIn this article we report on the fabrication of a carbon ionic liquid electrode (CILE) by using a room temperature ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) as binder. It was further modified by single‐walled carbon nanotubes (SWCNTs) to get a SWCNTs modified CILE denoted as SWCNTs/CILE. The redox protein of hemoglobin (Hb) was further immobilized on the surface of SWCNTs/CILE with the help of Nafion film. UV‐vis and FT‐IR spectra indicated that the immobilized Hb retained its native conformation in the composite film. The direct electrochemistry of Hb on the SWCNTs/CILE was carefully studied in pH 7.0 phosphate buffer solution (PBS). Cyclic voltammetric results indicated that a pair of well‐defined and quasireversible voltammetric peaks of Hb heme Fe(III)/Fe(II) was obtained with the formal potential (E°') at −0.306 V (vs. SCE). The electrochemical parameters such as the electron transfer coefficient (α), the electron transfer number (n) and the apparent heterogeneous electron transfer rate constant (ks) were calculated as 0.34, 0.989 and 0.538 s−1, respectively. The fabricated Hb modified electrode showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) in the concentration range from 20.0 to 150.0 mmol/L with the detection limit of 10.0 mmol/L (3σ).

Fabrication of a glucose sensor based on a novel nanocomposite electrode

The direct electrocatalytic oxidation of glucose in alkaline medium at nanoscale nickel hydroxide modified carbon ionic liquid electrode (CILE) has been investigated. Enzyme free electro-oxidation of glucose have greatly been enhanced at nanoscale Ni(OH) 2 as a result of electrocatalytic effect of Ni +2/Ni +3 redox couple. The sensitivity to glucose was evaluated as 202 μA mM −1 cm −2. From 50 μM to 23 mM of glucose can be selectively measured using platelet-like Ni(OH) 2 nanoscale modified CILE with a detection limit of 6 μM (S/N = 3). The nanoscale nickel hydroxide modified electrode is relatively insensitive to electroactive interfering species such as ascorbic acid (AA), and uric acid (UA) which are commonly found in blood samples. Long-term stability, high sensitivity and selectivity as well as good reproducibility and high resistivity towards electrode fouling resulted in an ideal inexpensive amperometric glucose biosensor applicable for complex matrices.

Fabrication and Electrochemical Behavior of Hemoglobin Modified Carbon Ionic Liquid Electrode

AbstractA new hemoglobin (Hb) and room temperature ionic liquid modified carbon paste electrode was constructed by mixing Hb with 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) and graphite powder together. The Hb modified carbon ionic liquid electrode (Hb‐CILE) was further characterized by FT‐IR spectra, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Hb in the carbon ionic liquid electrode remained its natural structure and showed good direct electrochemical behaviors. A pair of well‐defined quasireversible redox peaks appeared with the apparent standard potential (E′) as −0.334 (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (α) and the heterogeneous electron transfer kinetic constant (ks) of the electrode reaction were calculated with the results as 1.2, 0.465 and 0.434 s−1, respectively. The fabricated Hb‐CILE exhibited excellent electrocatalytic activity to the reduction of H2O2. The calibration range for H2O2 quantitation was between 8.0×10−6 mol/L and 2.8×10−4 mol/L with the linear regression equation as Iss (μA)=0.12 C (μmol/L)+0.73 (n=18, γ=0.997) and the detection limit as 1.0×10−6 mol/L (3σ). The apparent Michaelis–Menten constant (KMapp) of Hb in the modified electrode was estimated to be 1.103 mmol/L. The surface of this electrochemical sensor can be renewed by a simple polishing step and showed good reproducibility.

Electrochemistry and Electrocatalysis of a Nafion/Nano‐CaCO3/Hb Film Modified Carbon Ionic Liquid Electrode Using BMIMPF6 as Binder

AbstractIn this paper a room temperature ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) was used as binder for the construction of carbon ionic liquid electrode (CILE) and a new electrochemical biosensor was developed for determination of H2O2 by immobilization of hemoglobin (Hb) in the composite film of Nafion/nano‐CaCO3 on the surface of CILE. The Hb modified electrode showed a pair of well‐defined, quasi‐reversible redox peaks with Epa and Epc as −0.265 V and −0.470 V (vs. SCE). The formal potential (E°′) was got by the midpoint of Epa and Epc as −0.368 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The peak to peak separation was 205 mV in pH 7.0 Britton–Robinson (B–R) buffer solution at the scan rate of 100 mV/s. The direct electrochemistry of Hb in the film was carefully investigated and the electrochemical parameters of Hb on the modified electrode were calculated as α=0.487 and ks=0.128 s−1. The Nafion/nano‐CaCO3/Hb film electrode showed good electrocatalysis to the reduction of H2O2 in the linear range from 8.0 to 240.0 μmol/L and the detection limit as 5.0 μmol/L (3σ). The apparent Michaelis–Menten constant (KMapp) was estimated to be 65.7 μmol/L. UV‐vis absorption spectroscopy and FT‐IR spectroscopy showed that Hb in the Nafion/nano‐CaCO3 composite film could retain its native structure.