Guangjiu Li

Fabrication of graphene-platinum nanocomposite for the direct electrochemistry and electrocatalysis of myoglobin

In this paper a platinum (Pt) nanoparticle decorated graphene (GR) nanosheet was synthesized and used for the investigation on direct electrochemistry of myoglobin (Mb). By integrating GR-Pt nanocomposite with Mb on the surface of carbon ionic liquid electrode (CILE), a new electrochemical biosensor was fabricated. UV-Vis absorption and FT-IR spectra indicated that Mb remained its native structure in the nanocomposite film. Electrochemical behaviors of Nafion/Mb-GR-Pt/CILE were investigated with a pair of well-defined redox peak appeared, which indicated that direct electron transfer of Mb was realized on the underlying electrode with the usage of the GR-Pt nanocomposite. The fabricated electrode showed good electrocatalytic activity to the reduction of trichloroacetic acid in the linear range from 0.9 to 9.0 mmol/L with the detection limit as 0.32 mmol/L (3σ), which showed potential application for fabricating novel electrochemical biosensors and bioelectronic devices.

Application of three-dimensional reduced graphene oxide-gold composite modified electrode for direct electrochemistry and electrocatalysis of myoglobin

In this paper a three-dimensional (3D) reduced graphene oxide (RGO) and gold (Au) composite was synthesized by electrodeposition and used for the electrode modification with carbon ionic liquid electrode (CILE) as the substrate electrode. Myoglobin (Mb) was further immobilized on the surface of 3D RGO-Au/CILE to obtain an electrochemical sensing platform. Direct electrochemistry of Mb on the modified electrode was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the modified electrode. The results can be ascribed to the presence of highly conductive 3D RGO-Au composite on the electrode surface that accelerate the electron transfer rate between the electroactive center of Mb and the electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.2 to 36.0 mmol/L with the detection limit of 0.06 mmol/L (3σ).

Electrochemical behavior of luteolin on a chitosan–graphene modified glassy carbon electrode and its sensitive detection

A simple and highly sensitive electrochemical method was developed for the determination of luteolin based on the chitosan–graphene (GR) modified glassy carbon electrode. Due to the specific characteristics of GR present on the electrode surface, the electrochemical response of luteolin on the modified electrode was greatly enhanced with the appearance of a pair of well-defined redox peaks. The results were attributed to the large surface area and high conductivity of GR with the considerable improvement of the redox peak current, which allowed the development of a highly sensitive voltammetric sensor for the determination of luteolin. Under the optimized conditions the oxidative peak currents increased linearly with the concentration of luteolin in the range from 2.0 nmol L−1 to 60.0 μmol L−1, with a detection limit of 5.93 × 10−10 mol L−1 (3S0/S). The analytical performance of this sensor has been evaluated for the detection of luteolin in Duyiwei capsules as a real sample with satisfactory results.

Investigation on direct electrochemical and electrocatalytic behavior of hemoglobin on palladium-graphene modified electrode

Palladium-graphene (Pd-GR) nanocomposite was acted as modifier for construction of the modified electrode with direct electrochemistry of hemoglobin (Hb) realized. By using Nafion as the immobilization film, Hb was fixed tightly on Pd-GR nanocomposite modified carbon ionic liquid electrode. Electrochemical behaviors of Hb modified electrode were checked by cyclic voltammetry and a pair of redox peaks originated from direct electron transfer of Hb was appeared. The Hb modified electrode had excellent electrocatalytic activity to the reduction of trichloroacetic acid and sodium nitrite in the concentration range from 0.6 to 13.0mmol·L-1 and from 0.04 to 0.5 mmol·L-1. Therefore Pd-GR nanocomposite was proven to be a good candidate for the fabrication of third-generation electrochemical biosensor.

Application of titanium dioxide nanowires and electroreduced graphene oxide modified electrodes for the electrochemical detection of specific tlh gene sequence from Vibrio parahaemolyticus

In this paper, an electrochemical DNA biosensor was prepared using electroreduced graphene oxide, titanium dioxide nanowires and chitosan modified carbon ionic liquid electrode as the substrate electrode, which was further used for the electrochemical detection of the specific tlh gene sequence from Vibrio parahaemolyticus. The presence of nanocomposite on the electrode surface can increase the surface area and fix the ssDNA probe sequence by electrostatic attraction. After the hybridization with the target ssDNA sequence under the selected conditions, methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction. Under the optimal conditions, the reduction peak current of MB was proportional to the concentration of tlh gene sequence in the range from 1.0 × 10−12 to 1.0 × 10−6 mol L−1 with a detection limit as 3.17 × 10−13 mol L−1 (3σ). This electrochemical DNA sensor exhibited good ability to discriminate between one-base and three-base mismatched ssDNA sequences, and the polymerase chain reaction amplification product of the tlh gene from oyster samples was further detected with satisfactory results.

Highly sensitive electrochemical sensor for dopamine with a double-stranded deoxyribonucleic acid/gold nanoparticle/graphene modified electrode

In this paper a novel electrochemical sensor was fabricated for the sensitive detection of dopamine (DA). By using a carbon ionic liquid electrode (CILE) as the substrate electrode, graphene (GR), gold nanoparticles (AuNPs) and double-stranded deoxyribonucleic acid (dsDNA) were electrodeposited on the surface of CILE step-by-step to obtain the modified electrode (dsDNA/Au/GR/CILE). Due to the presence of various modifiers on the electrode surface, the modified electrode exhibited specific synergistic effects, such as high conductivity and large surface of GR, good conductivity and biocompatibility of AuNPs, and the specific binding effect of dsDNA with the target analyte DA. Cyclic voltammetric studies indicated that a pair of well-defined redox peaks of DA appeared on dsDNA/Au/GR/CILE in pH 6.0 phosphate buffer solution and electrochemical behaviors of DA were carefully investigated. Under the optimal conditions the oxidation peak current of DA was linearly related to DA concentration in the range from 0.04 μmol L−1 to 0.6 mmol L−1 with a detection limit of 19.0 nmol L−1 (3σ). The modified electrode displayed excellent selectivity and repeatability, and was further used to detect DA content in drug samples with satisfactory results.

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.