title: Direct electrochemistry with enhanced electrocatalytic activity of hemoglobin in hybrid modified electrodes composed of graphene and multi-walled carbon nanotubes.
abstract: 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 (ks) 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.
authors.affiliation: College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158 China. swyy26@hotmail.com
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.forename: Lili
authors.initials: L
authors.lastname: Cao
authors.forename: Ying
authors.initials: Y
authors.lastname: Deng
authors.forename: Shixing
authors.initials: S
authors.lastname: Gong
authors.forename: Fan
authors.initials: F
authors.lastname: Shi
authors.forename: Gaonan
authors.initials: G
authors.lastname: Li
authors.forename: Zhenfan
authors.initials: Z
authors.lastname: Sun
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation; D002384:Catalysis; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods*; D004566:Electrodes; D006108:Graphite / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D057230:Limit of Detection; D008855:Microscopy, Electron, Scanning; D037742:Nanotubes, Carbon; D010084:Oxidation-Reduction; D015203:Reproducibility of Results; D012977:Sodium Nitrite / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014238:Trichloroacetic Acid / Q000032:analysis / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D037742:Nanotubes, Carbon; D014238:Trichloroacetic Acid; D006108:Graphite; D006861:Hydrogen Peroxide; D012977:Sodium Nitrite