Synthesis and utilization of Co3O4 doped carbon nanofiber for fabrication of hemoglobin-based electrochemical sensor.

In this paper cobalt oxide (Co3O4) nanoparticles were mixed with polyacrylonitrile to prepare Co3O4 doped carbon nanofiber (CNF) composite by electrospinning and carbonization, which was further used to modify on carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on Co3O4-CNF/CILE surface with Nafion acted as the protective film to fabricate an electrochemical biosensor (Nafion/Hb/Co3O4-CNF/CILE). Electrochemical behavior of Hb on the electrode was investigated with a pair of quasi-reversible redox peak appeared on cyclic voltammogram and electrochemical parameters were calculated. Moreover, this biosensor had good analytical capabilities for electrocatalytic reduction of different substrates including trichloroacetic acid, potassium bromate and sodium nitrite with wider detection range from 40.0 to 260.0 mmol L-1, 0.1 to 48.0 mmol L-1 and 1.0 to 12.0 mmol L-1 by cyclic voltammetry, respectively. The proposed method showed excellent anti-interferences ability with good selectivity and was successful used for quantitative detection of real samples, which displayed the potential applications to develop into a new analytical device.

A biomass-derived porous carbon-based nanocomposite for voltammetric determination of quercetin.

Porous carbon was prepared from wheat flour by alkali treatment and carbonization. The resulting biomass-derived porous carbon (BPC) was employed to prepare a Pt-Au-BPC nanocomposite by a hydrothermal method. The material was then placed on the surface of a carbon ionic liquid electrode (CILE). The Pt-Au-BPC was characterized by SEM, XPS, and the modified CILE by electrochemical methods. They revealed a porous structure, a large specific surface with high conductivity. Pt-Au-BPC/CILE was applied to the sensitive determination of quercetin. Electrochemical response was studied by cyclic voltammetry and differential pulse voltammetry (DPV). Under optimized experimental conditions, the oxidation peak current (measured at 0.48 V vs. Ag/AgCl by DPV) increases linearly in the 0.15 to 6.0 µM and in the 10.0 to 25.0 µM quercetin concentration range. The detection limit is 50.0 nM (at 3σ). The Pt-Au-BPC/CILE was applied to the direct determination of quercetin in ginkgo tablets sample and gave satisfactory results. Graphical abstract A Pt-Au-BPC nanocomposite modified carbon ionic liquid electrode was applied to differential pulse voltammetric determination of quercetin. BPC: biomass-derived porous carbon.

Myoglobin- and Hydroxyapatite-Doped Carbon Nanofiber-Modified Electrodes for Electrochemistry and Electrocatalysis.

In this paper, a hydroxyapatite (HAp)-doped carbon nanofiber (CNF)-modified carbon ionic liquid electrode (CILE) was prepared and used for the investigation on the direct electrochemistry and electrocatalysis of myoglobin (Mb). HAp nanoparticles were mixed within a polyacrylonitrile (PAN) solution, and a HAp@PAN nanofiber was synthesized by electrospinning process, which was further controlled by carbonization at 800 °C for 2 h in a nitrogen atmosphere to get a HAp@CNF nanocomposite. Various techniques were used to check the physicochemical properties of HAp@CNF. Mb was mixed with a HAp@CNF dispersion solution and casted on the surface of CILE to obtain an electrochemical sensing platform. The direct electrochemistry of Mb on the modified electrode was checked when a pair of enhanced redox waves appeared, indicating the direct electron transfer of Mb. HAp@CNF exhibited high conductivity, good biocompatibility, and large surface area, which was beneficial for Mb immobilization. The modified electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid and sodium nitrite, which was further used to establish a new electroanalytical method. Real samples were analyzed by the proposed method with satisfactory results.

Electrochemical performance of myoglobin based on TiO2-doped carbon nanofiber decorated electrode and its applications in biosensing.

A new biosensing strategy based on a TiO2-doped carbon nanofiber (CNF) composite modified electrode was developed. TiO2@CNF was prepared by electrospinning with further carbonization, before being characterized by various methods and used for electrode modification on the surface of carbon ionic liquid electrode (CILE). Myoglobin (Mb) was further immobilized on the modified electrode surface. The results of ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR) spectroscopy showed that Mb maintained its native structure without denaturation in the composite film. Direct electron transfer and the electrocatalytic properties of Mb on the electrode surface were further investigated. A pair of quasi-reversible redox peaks appeared on the cyclic voltammogram, indicating that direct electrochemistry of Mb was realized in the nanocomposite film. This could be attributed to the specific properties of TiO2@CNF nanocomposite, including a large surface-to-volume ratio, good biocompatibility and high conductivity. Nafion/Mb/TiO2@CNF/CILE exhibited an excellent electrochemical catalytic ability in the reduction of trichloroacetic acid, NaNO2 and H2O2. All results demonstrated potential applications of TiO2@CNF in third-generation electrochemical biosensors.

Three-dimensional reduced graphene oxide aerogel modified electrode for the sensitive quercetin sensing and its application.

Quercetin belongs to flavonoid drug that has favorable properties such as antiviral, anticancer, anti-allergic and anti-tumor. Therefore a sensitive method is highly required for quercetin determination. In this paper, a three-dimensional reduced graphene oxide aerogel (3D-rGA) with excellent porous framework was synthesized via one-step hydrothermal technique. The characteristics and performances of 3D-rGA were checked by SEM, TEM, BET, XRD, Raman, FT-IR, XPS and electrochemical methods, which exhibited good properties including unique porous structure, large surface area and excellent conductivity. 3D-rGA was further used as the modifier on carbon ionic liquid electrode (CILE) to construct a modified electrode, which was applied to sensitive and selective determination of quercetin. Electrochemical responses of quercetin were accelerated with a pair of symmetrical cyclic voltammetric peaks in good shape appeared and the electrochemical parameters were calculated. The sensitive oxidation response of quercetin from differential pulse voltammetry was verified. Under the selected conditions, electroanalysis of quercetin was established by plotting the oxidation peak currents against quercetin concentrations with linear regression analysis. A wider linear range from 0.1 µmol/L to 100.0 µmol/L was obtained with a detection limit of 0.065 µmol/L (3S0/S). This as-explored approach could be successfully utilized for quercetin detection in Ginkgo tablets.