Electrochemical performance and electrocatalytic behavior of myoglobin on graphene tube-modified electrode

A new protein biosensing strategy based on a graphene tube (GT)-modified electrode was developed in this article. GT as a fixed material and signal amplifier was loaded on the carbon ionic liquid electrode (CILE) surface, which could provide a suitable environment for myoglobin (Mb) immobilization and promote electron transfer between Mb and the electrode. Fourier-transform infrared spectroscopy (FT-IR) of Mb before and after mixing with GT was checked and showed that the native structure of Mb was maintained. The direct electrochemistry of Mb was investigated with a pair of obtained well-defined and quasireversible redox peaks. The modified electrode (Nafion/Mb/GT/CILE) also showed excellent electrocatalytic activity for the reduction of trichloroacetic acid (TCA) and NaNO₂, which could be utilized to determine the concentrations of TCA and NaNO₂ with wide detection range and low detection limit. The biosensor was further applied to the detection of a real sample and obtained satisfactory experimental 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.     

Boron Nitride Nanosheet Modified Electrode: Preparation and Application to Direct Electrochemistry of Myoglobin

An ionic liquid modified carbon paste electrode (CILE) was prepared with 1‐hexylpyridine hexafluorophosphate (HPPF₆) and used as a substrate electrode. Then hexagonal boron nitride (BN) nanosheet, myoglobin (Mb) and Nafion were fixed on the electrode surface by coating method to get a new‐style chemically modified electrode (Nafion/Mb/BN/CILE). The morphology and crystal phase of BN nanosheet were characterized by SEM, TEM and XRD. UV‐Vis and FT‐IR results showed that Mb retained its original conformation in the composite modified film. In phosphate buffer solutions (PBS) with pH 3.0, cyclic voltammetry (CV) was performed to investigate the direct electrochemical behaviour of Mb. A pair of quasi‐reversible redox reaction peaks was obtained on the CV curve, proving that BN nanosheet had good biocompatibility and could accelerate electron transfer between Mb and electrode surface. Electrocatalytic reduction of trichloroacetic acid (TCA) was investigated, which was further applied to TCA detection. The catalytic reduction peak current at ?0.355 V depended linearly on the TCA concentration in the range of 0.2～30.0 mmol/L with the equation of Ipc (μA)=6.340 C (mmol/L)+0.305 (r=0.998), and the detection limit was 0.05 mmol/L (3 σ).     

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.     

Direct electrochemistry and electrocatalysis of hemoglobin on gold nanoparticle decorated carbon ionic liquid electrode

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM]EtOSO₃) as modifier and further gold nanoparticles were in situ electrodeposited on the surface of CILE. The fabricated Au/CILE was used as a new platform for the immobilization of hemoglobin (Hb) with the help of a Nafion film. Electrochemical experimental results indicated that direct electron transfer of Hb was realized on the surface of Au/CILE with a pair of well-defined quasi-reversible redox peaks appeared. The formal peak potential (E⁰′) was obtained as −0.210 V (vs. SCE) in pH 7.0 phosphate buffer solution (PBS), which was the characteristic of Hb heme Fe(III)/Fe(II) redox couple. The fabricated Nafion/Hb/Au/CILE showed excellent electrocatalytic activity to the reduction of trichloroacetic acid (TCA) and the reduction peak current was in proportional to TCA concentration in the range from 0.2 to 18.0 mmol/L with the detection limit as 0.16 mmol/L (S/N = 3). The proposed electrode showed good stability and reproducibility, and it had the potential application as a new third-generation electrochemical biosensor.     

Electrochemical behavior of horseradish peroxidase on WS2 nanosheet‐modified electrode and electrocatalytic investigation

In this paper, a WS₂ nanosheet was modified on the surface of a carbon ionic liquid electrode (CILE), and horseradish peroxidase (HRP) was further fixed on the electrode with a Nafion film. Direct electrochemistry and bioelectrocatalysis of HRP incorporated on the modified electrode were investigated in detail. On Nafion/HRP/WS₂/CILE, a pair of well‐defined quasi‐reversible redox peaks appeared on the cyclic voltammogram, indicating that the presence of the WS₂ nanosheet on the electrode surface could provide a specific interface with large surface area for HRP and its direct electron transfer rate was greatly enhanced. The formal potential (E⁰) obtained was –0.179 V, which was the typical feature of heme Fe(III)/Fe(II) in HRP. The electron transfer coefficient (α) and the heterogeneous electron transfer rate constant (k_s) of HRP were calculated as 0.44 and 1.01 s^–1, respectively. This HRP‐modified electrode showed excellent electrocatalytic activity for the reduction of trichloroacetic acid and NaNO₂ with a wide linear range and low detection limit. Real samples were detected by this proposed method, indicating the successful fabrication of a new third‐generation electrochemical enzyme sensor utilizing the WS₂ nanosheet.     

Direct electrochemistry of myoglobin based on DNA accumulation on carbon ionic liquid electrode

Poly-anionic deoxyribonucleic acid (DNA) was accumulated on the positively charged surface of carbon ionic liquid electrode (CILE) with N-butylpyridinium hexafluorophosphate (BPPF₆) as binder, and then myoglobin (Mb) was immobilized onto the DNA film by electrostatic interaction to form Mb/DNA/CILE electrode. The direct electrochemistry of Mb was then investigated in detail. A pair of well-defined, quasi-reversible cyclic voltammetric peaks of Mb was obtained with the formal potentials (E⁰′) at ?0.304 V (vs. SCE) in phosphate buffer solution (PBS, pH 7.0). The Mb/DNA/CILE electrode showed excellent electrocatalytic activity to H₂O₂ and trichloroacetic acid (TCA) in the range of 1.0–160 μmol/L and 0.5–40.0 mmol/L, respectively. The apparent Michaelis–Menten constants (K_M) toward H₂O₂ and TCA were calculated as 0.42 and 0.82 mmol/L. So, the DNA/CILE had potential to study other proteins.     

Direct electron transfer of horseradish peroxidase at Co<Subscript>3</Subscript>O<Subscript>4</Subscript>–graphene nanocomposite modified electrode and electrocatalysis

In this paper, the mixture of Co₃O₄–graphene nanocomposite and horseradish peroxidase (HRP) was spread on the surface of carbon ionic liquid electrode (CILE). Then, Nafion film was used for the immobilization. The results of spectroscopy proved that HRP kept up its native structure in the complex material. Direct electrochemistry of HRP resulted in a couple of quasi-reversible redox waves on cyclic voltammograms, reflecting the realization of direct electron transfer of HRP with electrode. The improvement in electrochemical responses was due to the usage of highly conductive Co₃O₄–graphene nanocomposite with biocompatible interface. Electrochemical parameters such as the electron transfer coefficient (α) was estimated as 0.47, and the apparent heterogeneous electron transfer rate constant (k _s) was calculated as 2.90 s^?1. The HRP modified electrode exhibited good electrochemical catalytic ability toward the reduction of trichloroacetic acid and NaNO₂. As a consequence, an updated third-generation electrochemical HRP biosensor with Co₃O₄–GR/CILE was constructed successfully.     

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 myoglobin biosensor based on carbon ionic liquid electrode modified with Fe3O4@SiO2 microsphere

In this paper, a Fe₃O₄@SiO₂ core-shell structure microsphere was synthesized and used to investigate the direct electron transfer of myoglobin (Mb) with a 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the substrate electrode. The mixture of Mb and Fe₃O₄@SiO₂ microsphere could form an organic–inorganic composite, which was immobilized on the surface of CILE with a chitosan (CS) film. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared on CS/Mb-Fe₃O₄@SiO₂/CILE with the formal peak potential (E ^0′) located at ?0.31 V (vs. saturated calomel electrode), which was corresponded to the electroactive center of Mb heme Fe(III)/Fe(II) redox couples. Direct electrochemical behaviors of Mb in CS-Fe₃O₄@SiO₂ composite film were carefully investigated with the electrochemical parameters calculated. The CS/Mb-Fe₃O₄@SiO₂/CILE showed good electrocatalytic behaviors to the reduction of trichloroacetic acid in the concentration range from 0.2 to 11.0 mmol L^?1 with the detection limit of 0.18 mmol L^?1 (3σ). Based on CS/Mb-Fe₃O₄@SiO₂/CILE, a new third-generation reagentless electrochemical biosensor was constructed with higher sensitivity and reproducibility.     

Direct electrochemistry with enhanced electrocatalytic activity of hemoglobin in hybrid modified electrodes composed of graphene and multi-walled carbon nanotubes

A graphene (GR) and multi-walled carbon nanotubes (MWCNT) hybrid was prepared and modified on a 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on GR-MWCNT/CILE surface with Nafion as the film forming material and the modified electrode was denoted as Nafion/Hb-GR-MWCNT/CILE. Spectroscopic results revealed that Hb molecules retained its native structure in the GR-MWCNT hybird. Electrochemical behaviors of Hb were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks obtained, which indicated that direct electron transfer of Hb was realized in the hybrid modified electrode. The result could be attributed to the synergistic effects of GR-MWCNT hybrid with enlarged surface area and improved conductivity through the formation of a three-dimensional network. Electrochemical parameters of the immobilized Hb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.03, the charge transfer coefficient (a) as 0.58 and the electron-transfer rate constant (k_s) as 0.97 s⁻¹. The Hb modified electrode showed good electrocatalytic ability toward the reduction of different substrates such as trichloroacetic acid in the concentration range from 0.05 to 38.0 mmol L⁻¹ with a detection limit of 0.0153 mmol L⁻¹ (3σ), H₂O₂ in the concentration range from 0.1 to 516.0 mmol L⁻¹ with a detection limit of 34.9 nmol/L (3σ) and NaNO₂ in the concentration range from 0.5 to 650.0 mmol L⁻¹ with a detection limit of 0.282 μmol L⁻¹ (3σ). So the proposed electrode had the potential application in the third-generation electrochemical biosensors without mediator.     

Direct Electrochemistry and Electrocatalysis of Myoglobin with Ionic Liquid through Multilayers Film on Carbon Ionic Liquid Electrode

Multilayers of myoglobin (Mb) with ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM]BF₄) was assembled on carbon ionic liquid electrode (CILE) based on the electrostatic attraction between the negatively charged Mb and the positively charged imidazolium ion of IL. The CILE was fabricated with 1‐ethyl‐3‐methylimidazolium ethylsulfate ([EMIM]EtOSO₃) as the modifier, which exhibited imidazolium ion on the electrode surface. Then Mb molecules were assembled on the surface of CILE step‐by‐step to get a {IL/Mb}_n multilayer film modified electrode. UV‐Vis adsorption and FT‐IR spectra indicated that Mb remained its native structure in the IL matrix. In deaerated phosphate buffer solution (pH 7.0) a pair of well‐defined quasi‐reversible redox peaks appeared with the apparent formal potential (E^0′) as ‐0.212 V (vs. SCE), which was the characteristic of Mb heme Fe(III)/Fe(II) redox couples. The results indicated that the direct electron transfer of Mb was realized on the modified electrode. The {IL/Mb}_n/CILE displayed excellent electrocatalytic ability to the trichloroacetic acid reduction in the concentration range from 2.0 to 22.0 mmol/L with the detection limit of 0.6 mmol/L (3σ). The proposed method provides a new platform to fabricate the third generation biosensor based on the self‐assembly of redox protein with ILs.     

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).     

Electrochemistry and electrocatalysis of hemoglobin in Nafion/nano-CaCO3 film on a new ionic liquid BPPF6 modified carbon paste electrode

Room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to construct a new carbon ionic liquid electrode (CILE), which exhibited enhanced electrochemical behavior as compared with the traditional carbon paste electrode with paraffin. By using the CILE as the basal electrode, hemoglobin (Hb) was immobilized on the surface of the CILE with nano-CaCO3 and Nafion film step by step. The Hb molecule in the film kept its native structure and showed good electrochemical behavior. In pH 7.0 Britton-Robinson (B-R) buffer solution, a pair of well-defined, quasi-reversible cyclic voltammetric peaks appeared with cathodic and anodic peak potentials located at -0.444 and -0.285 V (vs SCE), respectively, and the formal potential (E degrees') was at -0.365 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The formal potential of Hb shifted linearly to the increase of buffer pH with a slope of -50.6 mV pH-1, indicating that one electron transferred was accompanied with one proton transportation. Ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR) spectroscopy studies showed that Hb immobilized in the Nafion/nano-CaCO3 film still remained its native arrangement. The Hb modified electrode showed an excellent electrocatalytic behavior to the reduction of H2O2, trichloroacetic acid (TCA), and NaNO2.     

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.     

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 immobilized in the sodium alginate and SiO2 nanoparticles bionanocomposite film on a carbon ionic liquid electrode

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using a room temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) as binder. By using the CILE as basal electrode, the hemoglobin (Hb) molecule was immobilized on the surface of CILE with a sodium alginate (SA) hydrogel and SiO₂ nanoparticles organic-inorganic composite material. The direct electrochemical behaviors of Hb in the bionanocomposite film were further studied in a pH 7.0 Britton-Robinson (B-R) buffer solution. A pair of well-defined quasi-reversible cyclic voltammetric peaks of Hb was obtained on SA/nano-SiO₂/Hb/CILE with the formal potential (E^0’) at -0.355 V (vs. SCE), which was the characteristic of heme Fe(III)/Fe(II) redox couples. The formal potential of Hb Fe(III)/Fe(II) couple shifted negatively with increasing pH of solution with a slope of -45.2 mV/pH, which indicated that a one electron transfer accompanied with one proton transportation. The immobilized Hb showed good electrocatalytic manner to the reduction of trichloroacetic acid (TCA).     

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.     

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.     

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

In 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.