Electrochemistry and Voltammetric Determination of Adenosine with N‐Hexylpyridinium Hexafluorophosphate Modified Electrode

An ionic liquid N‐hexylpyridinium hexafluorophosphate (HPPF₆) modified carbon paste electrode was fabricated for the sensitive voltammetric determination of adenosine in this paper. Carbon ionic liquid electrode (CILE) was prepared by mixing graphite powder and HPPF₆ together and the CILE was characterized by scanning electron microscopy (SEM) and electrochemical methods. The electrochemical behaviors of adenosine on the CILE were studied carefully. Compared with the traditional carbon paste electrode (CPE), a small negative shift of the oxidation peak potential appeared with greatly increase of the oxidation peak current, which indicated the presence of ionic liquid in the carbon paste not only as the binder but also as the modifier and promoter. Under the optimal conditions the oxidation peak current increased with the adenosine concentration in the range from 1.0×10^?6 mol/L to 1.4×10^?4 mol/L with the detection limit of 9.1×10^?7 mol/L (S/N=3) by differential pulse voltammetry. The proposed method was applied to the human urine samples detection with satisfactory results.     

Application of NiMoO4 Nanorods for the Direct Electrochemistry and Electrocatalysis of Hemoglobin with Carbon Ionic Liquid Electrode

In this paper NiMoO₄ nanorods were synthesized and used to accelerate the direct electron transfer of hemoglobin (Hb). By using an ionic liquid (IL) 1‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) as the basic electrode, NiMoO₄ nanorods and Hb composite biomaterial was further cast on the surface of CILE and fixed by chitosan (CTS) to establish a modified electrode denoted as CTS/NiMoO₄‐Hb/CILE. UV‐vis and FT‐IR spectroscopic results showed that Hb in the film retained its native structures without any conformational changes. Electrochemical behaviors of Hb entrapped in the film were carefully investigated by cyclic voltammetry with a pair of well‐defined and quasi‐reversible redox voltammetric peaks appearing in phosphate buffer solution (PBS, pH 3.0), which was attributed to the direct electrochemistry of the electroactive center of Hb heme Fe(III)/Fe(II). The results were ascribed to the specific characteristic of NiMoO₄ nanorods, which accelerated the direct electron transfer rate of Hb with the underlying CILE. The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron transfer number (n) as 1.08, the charge transfer coefficient (α) as 0.39 and the electron‐transfer rate constant (k_s) as 0.82 s^?1. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA) in the concentration range from 0.2 to 26.0 mmol/L with a detection limit of 0.072 mmol/L (3σ), and H₂O₂ in the concentration range from 0.1 to 426.0 µmol/L with a detection limit of 3.16×10^?8 mol/L (3σ).     

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

In 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 (k_s) 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).     

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

In 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 (k_s) 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 Biosensor Based on Carbon Ionic Liquid Electrode Modified with Nafion/Hemoglobin/DNA Composite Film

A new electrochemical biosensor was constructed by immobilization of hemoglobin (Hb) on a DNA modified carbon ionic liquid electrode (CILE), which was prepared by using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) as the modifier. UV‐vis absorption spectroscopic result indicated that Hb remained its native conformation in the composite film. The fabricated Nafion/Hb/DNA/CILE was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A pair of well‐defined redox peaks was obtained on the modified electrode, indicated that the Nafion and DNA composite film provided an excellent biocompatible microenvironment for keeping the native structure of Hb and promoting the direct electron transfer rate of Hb with the basal electrode. The electrochemical parameters of Hb in the composite film were further calculated with the results of the charge transfer coefficient (α) and the apparent heterogeneous electron transfer rate constant (k_s) as 0.41 and 0.31 s^?1. The proposed electrochemical biosensor showed good electrocatalytic response to the reduction of trichloroacetic acid (TCA), H₂O₂, NO and the apparent Michaelis–Menten constant (K_M^app) for the electrocatalytic reaction was calculated, respectively.     

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

In 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.     

A sensitive electrochemical sensor for detection of rutin based on a gold nanocage‐modified electrode

In this article, an electrochemical sensor based on a gold nanocage (AuNC)‐modified carbon ionic liquid electrode (CILE) was fabricated and applied to the sensitive rutin determination. The presence of AuNCs on the electrode surface greatly improved the electrochemical performance of the working electrode due to its specific microstructure and high metal conductivity. Electrochemical behavior of rutin on AuNCs/CILE was studied using cyclic voltammetry and differential pulse voltammetry with the related electrochemical parameters calculated. Under the optimal experimental conditions, the oxidation peak current of rutin and its concentration had good linear relationship in the range from 4.0 × 10^?9 to 7.0 × 10^?4 mol/L with a low detection limit of 1.33 × 10^?9 mol/L (3σ). This fabricated AuNCs/CILE was applied to direct detection of the rutin concentration in drug samples with satisfactory results, showing the real application of AuNCs in the field of chemically modified electrodes.     

Direct electrochemistry and electrocatalysis of hemoglobin in sodium alginate film on a BMIMPF6 modified carbon paste electrode

A room temperature ionic liquid (RTIL) modified carbon paste electrode was constructed based on the substitute of paraffin with 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF₆) as binder for carbon paste. Direct electrochemistry and electrocatalytic behaviors of hemoglobin (Hb) entrapped in the sodium alginate (SA) hydrogel film on the surface of this carbon ionic liquid electrode (CILE) were investigated. The presence of IL in the CILE increased the electron transfer rate and provided a biocompatible interface. Hb remained its bioactivity on the surface of CILE and the SA/Hb modified electrode showed a pair of well-defined, quasi-reversible cyclic voltammetric peaks with the apparent standard potential (E^0′) at about −0.344 V (vs. SCE) in pH 7.0 Britton–Robinson (B–R) buffer solution, which was attributed to the Hb Fe(III)/Fe(II) redox couple. UV–Vis absorption spectra indicated that heme microenvironment of Hb in SA film was similar to its native status. Hb showed a thin-layer electrochemical behavior in the SA film with the direct electron transfer achieved on CILE without the help of electron mediator. Electrochemical investigation indicated that Hb took place one proton with one electron electrode process and the average surface coverage of Hb in the SA film was 3.2 × 10⁻¹⁰ mol/cm². The immobilized Hb showed excellent electrocatalytic responses to the reduction of H₂O₂ and nitrite.     

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

In 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 E_pa and E_pc as ?0.265 V and ?0.470 V (vs. SCE). The formal potential (E°′) was got by the midpoint of E_pa and E_pc 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 k_s=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 (K_M^app) 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.     

Electrochemistry of adenosine-5′-diphosphate on ionic liquid modified carbon electrode and its detection

A sensitive electrochemical method was proposed for the determination of adenosine-5′-diphosphate (ADP) on an ionic liquid (IL) 1-(3-chloro-2-hydroxy-propyl)-3-methylimidazole chloride modified carbon paste electrode (CPE) in a pH 4.5 Britton-Robinson (B-R) buffer solution. Compared with CPE, IL modified CPE (CILE) showed strong electrocatalytic ability to promote the electrochemical oxidation of ADP. A well-defined irreversible oxidation peak of ADP appeared at +1.381 V with an adsorption-controlled process, which was due to the presence of high conductive IL on the electrode. The experimental conditions were optimized and the electrochemical parameters of ADP were calculated with the electron transfer coefficient (α) as 0.293, the electron transfer number (n) as 1.23, the apparent heterogeneous electron transfer rate constant (k ^s) as 3.325 × 10^?6 s^?1 and the surface coverage (Γ_T) as 0.92 × 10^?8 mol/cm². Under the optimum conditions, the oxidation peak current was linear to ADP concentration in the range from 3.0 to 1000.0 μmol/L with the detection limit as 2.78 μmol/L (3σ) by differential pulse voltammetry. The CILE also eliminated the interferences of commonly coexisting substances and was successfully applied to detect the ADP artificial samples.     

Direct Electron Transfer of Hemoglobin on a Carbon Ionic Liquid Electrode with TiO2 Nanopatricle as Enhancer

Room temperature ionic liquids (RTILs) N‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) was fabricated and applied to adsorb the hemoglobin (Hb) and TiO₂ nanoparticles on the electrode surface step by step to form a Hb modified electrode noted as TiO₂/Hb/CILE. UV‐Vis and FT‐IR spectra showed that Hb in the film retained its native conformations. Cyclic voltammetric experiments indicated that a pair of well‐defined quasi‐reversible redox peaks appeared with the formal potential (E^0′) located at ?0.251 V (vs. SCE) at pH 7.0 phosphate buffer solution (PBS), which was the characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters of the Hb in the film such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant (k_s) were estimated as 0.469, 0.87 and 0.635 s^?1, respectively.     

Application of Titanium Dioxide Nanowires for the Direct Electrochemistry of Hemoglobin and Electrocatalysis

Titanium dioxide (TiO₂) nanowires were synthesized and used for the realization of direct electrochemistry of hemoglobin (Hb) with carbon ionic liquid electrode (CILE) as the substrate electrode. TiO₂‐Hb composite was casted on the surface of CILE with a chitosan film and spectroscopic results confirmed that Hb retained its native structure in the composite. Direct electron transfer of Hb on the modified electrode was realized with a pair of quasi‐reversible redox waves appeared, indicating that the presence of TiO₂ nanowires could accelerate the electron transfer rate between the electroactive center of Hb and the substrate electrode. Electrochemical behaviors of Hb on the modified electrode were carefully investigated with the values of the electron transfer coefficient (α), the electron transfer number and the heterogeneous electron transfer rate constant (k_s) as 0.58, 0.98 and 1.62 s^‐1. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid and NaNO₂ with wider linear range and lower detection limit, indicating the successful fabrication of a new third‐generation biosensor.     

Immobilization and Bioelectrochemistry of Hemoglobin Based on Carrageenan and Room Temperature Ionic Liquid Composite Film

A novel biopolymer/room‐temperature ionic liquid composite film based on carrageenan, room temperature ionic liquid (IL) [1‐butyl‐3‐methylimidazolium tetra?uoroborate ([BMIM]BF₄)] was explored for immobilization of hemoglobin (Hb) and construction of biosensor. Direct electrochemistry and electrocatalytic behaviors of Hb entrapped in the IL‐carrageenan composite ?lm on the surface of glassy carbon electrode (GCE) were investigated. UV‐vis spectroscopy demonstrated that Hb in the IL‐carrageenan composite ?lm could retain its native secondary structure. A pair of well‐de?ned redox peaks of Hb was obtained at the Hb‐IL‐carrageenan composite ?lm modi?ed electrode through direct electron transfer between the protein and the underlying electrode. The heterogeneous electron transfer rate constant (k_s) was 2.02 s^?1, indicating great facilitation of the electron transfer between Hb and IL‐carrageenan composite film modi?ed electrode. The modi?ed electrode showed excellent electrocatalytic activity toward reduction of hydrogen peroxide with a linear range of 5.0×10^?6 to 1.5×10^?4 mol/L and the detection limit was 2.12×10^?7 mol/L (S/N=3). The apparent Michaelis‐Menten constant K_M^app for hydrogen peroxide was estimated to be 0.02 mmol/L, indicating that the biosensor possessed high af?nity to hydrogen peroxide. In addition, the proposed biosensor showed good reproducibility and stability.     

Direct electrochemistry of hemoglobin in a nafion and CuS microsphere modified carbon ionic liquid electrode and its electrocatalytic behavior

Direct electrochemistry of hemoglobin (Hb) was realized on a Nafion and CuS microsphere composite film modified carbon ionic liquid electrode (CILE) with N-butylpyridinium hexafluorophosphate (BPPF6) as binder. Scanning electron microscopy (SEM), UV-Vis absorption spectroscopy and cyclic voltammetry were used to characterize the fabricated Nafion/CuS/Hb/CILE. Experimental results showed that a pair of well-defined quasi-reversible redox peaks appeared with the formal potential as ?0.386 V (vs. SCE) in pH 7.0 Britton-Robinson (B-R) buffer solution, which was attributed to the Hb heme Fe(III)/Fe(II) redox couples. The electrochemical parameters of Hb in the composite film were carefully investigated with the charge transfer coefficient (α), the electron transfer number (n) and the electron transfer rate constant (k _s) as 0.505, 1.196 and 0.610 s^?1, respectively. The composite film provided a favorable microenvironment for retaining the native structure of Hb. The presence of CuS microspheres showed great improvement on the electron transfer rate of Hb with the CILE, which maybe due to the contribution of specific characteristics of CuS microspheres and the inherent advantages of ionic liquid on the modified electrode. The fabricated Hb modified electrode showed good electrocatalytic ability in the reduction of H₂O₂. The proposed bioelectrode can be used as a new third generation H₂O₂ biosensor.     

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

Based 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.     

Electrodeposition CaCO3 Nanoparticles‐chitosan Composite Film on Carbon Ionic Liquid Electrode as a Platform for Hemoglobin Electrochemical Biosensor

By one‐step co‐electrodeposition CaCO₃ nanoparticles‐chitosan composite film on carbon ionic liquid electrode (CILE), and then by spreading the composition of hemoglobin (Hb) and chitosan on the nanoCaCO₃‐chi/CILE, a Hb‐chi/nanoCaCO₃‐chi/CILE was fabricated and the direct electrochemistry and electrocatalysis of Hb at the electrode was investigated. The electrochemical impedance spectroscopy of the modified electrode showed the electron transfer resistance was 1166 Ω. Investigation results of cyclic voltammetrys showed a pair of well‐defined and quasireversible redox peak of Hb with the formal potentials of ‐0.295 V (vs. SCE) in 0.1 mol·L^‐1 pH 7.0 PBS; the response time of the reduction peak currents of Hb was lower than 3s; a linear range for determination of H₂O₂ was from 5.0 μmol·L^‐1 to 1.3 mmol·L^‐1 with a detection limit of 1.6 μmol·L^‐1 (S/N = 3) and a sensitivity of 0.16 A·M^‐1·cm^‐2; the electron transfer rate constant and the apparent Michaelis‐Menten constant of Hb were 1.98 s^‐1 and 0.81 mmol·L^‐1, respectively. As a result, the case of the one‐step co‐electrodeposition and the promising feature of biocomposite could serve as a versatile platform for the fabrication of electrochemical biosensors.     

Sensitive and Simple Electrochemical Detection of Lead(II) with Carbon Ionic Liquid Electrode

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM]EtOSO₃) as the modifier and further used as the working electrode for the sensitive anodic stripping voltammetric detection of Pb²⁺. The characteristics of the CILE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In pH 4.5 NaAc‐HAc buffer Pb²⁺ was accumulated on the surface of CILE due to the extraction effect of IL and reduced at a negative potential (‐1.20 V). Then the reduced Pb was oxidized by differential pulse anodic stripping voltammetry with an obvious stripping peak appeared at ?0.67 V. Under the optimal conditions Pb²⁺ could be detected in the concentration range from 1.0 × 10^?8 mol/L to 1.0 × 10^?6 mol/L with the linear regression equation as I_p(μA) = ?0.103 C (μmol/L) + 0.0376 (γ = 0.999) and the detection limit as 3.0 × l0^?9 mol/L (3σ). Interferences from other metal ions were investigated and Cd²⁺ could be simultaneously detected in the mixture solution. The proposed method was further applied to the trace levels of Pb²⁺ detection in water samples with satisfactory results.     

Direct Electrochemistry of Myoglobin in a Nafion‐Ionic Liquid Composite Film Modified Carbon Ionic Liquid Electrode

In this paper two kinds of ionic liquids (ILs) were used for the construction of a myoglobin (Mb) electrochemical biosensor. Firstly a hydrophilic ionic liquid of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) was used as binder to prepare a carbon ionic liquid electrode (CILE), then a Nafion and hydrophobic ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆) composite film was applied on the surface of the CILE. The direct electrochemistry of Mb in the Nafion‐BMIMPF₆/CILE was achieved with the cathodic and anodic peak potentials located at ?0.345 V and ?0.213 V (vs. SCE). The formal potential (E°′) was located at ?0.279 V, which was the characteristic of Mb Fe^III/Fe^II redox couples. The electrochemical behaviors of Mb in the Nafion‐ionic liquid composite film modified CILE were carefully investigated. The Mb modified electrode showed good electrocatalytic behaviors to the reduction of trichloroacetic acid (TCA) and NaNO₂. Based on the Nafion‐BMIMPF₆/Mb/CILE, a new third generation reagentless biosensor was constructed.     

Square Wave Voltammetry for Selective Detection of Dopamine Using Polyglycine Modified Carbon Ionic Liquid Electrode

The electrochemical polymerization of glycine on carbon ionic liquid electrode (CILE) was described. The presence of ionic liquid on the surface of CILE facilitated the electropolymerization of glycine. The polyglycine modified CILE provided a valid and simple approach to selectively detect dopamine in the presence of AA in physiological environment. The proposed sensor not only decreased the voltammetric responses of AA but also dramatically enhanced the oxidation peak current of DA compared to bare CILE. Using square wave voltammetry, the modified CILE showed good electrochemical behavior to DA, a linear range of 1.0×10^?7–3.0×10^?4 M in the presence of 1 mM ascorbic acid (AA) and a detection limit of 5.0×10^?9 M was estimated (S/N=3).     

Electrodeposited Graphene and Silver Nanoparticles Modified Electrode for Direct Electrochemistry and Electrocatalysis of Hemoglobin

By using a 1‐butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the working electrode, graphene (GR) nanosheets and silver nanoparticles (Ag NPs) were step by step electrodeposited on the surface of the CILE with potentiostatic method. The fabricated Ag/GR/CILE was used as a new platform for protein electrochemistry and hemoglobin (Hb) was immobilized on its surface with chitosan (CTS) as film forming material. In 0.1 mol/L phosphate buffer solution, a pair of well‐defined and quasi‐reversible redox peaks appeared on the CTS/Hb/Ag/GR/CILE with a formal peak potential of ?0.202 V (vs. SCE) and a peak‐to‐peak separation (ΔE_p) of 68 mV, which indicated that direct electrochemistry of Hb was realized on the modified electrode. The results could be attributed to the synergistic effects of Ag NPs and GR nanosheets on the electrode surface, which provided a specific three‐dimensional structure with high conductivity and good biocompatibility. The Hb modified electrode showed excellent electrocatalysis to the reduction of trichloroacetic acid in the concentration range from 0.8 to 22.0 mmol/L with a detection limit of 0.42 mmol/L (3σ). Moreover, the modified electrode exhibited favorable reproducibility, long term stability and accuracy, with potential applications in the third‐generation electrochemical biosensor.