Studies Of Electrochemical Sensors Based On Graphene Nanocomposites

As a new type of carbon nanomaterials, graphene has many excellent properties such as fast electron transportation, zero band gap and large specific surface area. It is excepted that grapheme had extensive applications in electrochemical detection and catalysis. As a new kind of detection tool, electrochemical sensors have advantages of simple preparation, rapid response, high sensitivity and low cost. Electrochemical sensors are widely used in food security, clinical diagnostics and environmental monitoring. Nanomaterial, a nanometer sized material, is different from common sized material on magnetic, optical, thermal, electrical, mechanical properties. For the preparation of sensors, nanomaterial can significantly enhance the performance of the sensors. This thesis focus on the graphene and studies the application of graphene-based nanocomposites in electrochemical sensors. The main contents of this paper have been described as follows:1. Graphene (GR) was synthesized by chemical oxidation-reduction method. The graphene was added into chitosan (CS) solution for preparing CS-dispersed GR. The CS-dispersed GR modified electrode adsorbed a layer of gold nanoparticles (AuNPs), and then hemoglobin (Hb) was immobilized on the modified electrode. Due to the good biocompatibility of GR, CS and AuNPs, Hb immobilized on the modified electrode retained its native structure well and successfully realized the direct electrochemistry. A high performance hydrogen peroxide sensor was fabricated by the direct electrochemistry of Hb. The introduction of AuNPs effectively improve the performance of the hydrogen peroxide sensor. The fabricated sensor exhibited good electrocatalytic activity for the detection of hydrogen peroxide with a high sensitivity of347.1mAcm-2M-1and a wide linear range from2to935μM. Meanwhile, the sensor showed good stability.2. A novel nanocomposite was prepared by combining graphene (GR), gold nanoparticles (AuNPs) and P-cyclodextrin (P-CD) via a simple sonication-induced assembly. The nanocomposite modified electrode can be used to detect dopamine (DA) and uric acid (UA). The modified electrode combined the benefits of GR, AuNPs and β-CD had large specific surface area and superior electron transfer ability, and the electrode can realize the sensitive detection of DA and UA. Under the optimized conditions, the fabricated electrode exhibited linear responses to DA and UA in the ranges0.2-33μM and0.1-22μM, with detection limits of0.08μM and0.04μM (S/N=3), respectively. Meanwhile, the electrode could be used for the detection of UA in real samples. 3. This chapter studied the electrochemical behaviours of p-Nitrophenol (p-NP) and o-Nitrophenol (o-NP) on graphene-chitosan (GR-CS) nanocomposite film modified glassy carbon electrode (GR-CS/GCE). Due to the introduction of graphene, GR-CS/GCE showed good electrocatalytic activity towards the reduction of p-NP and o-NP. Under the optimized condition, the peak-to-peak separation for two isomers was81mV, which indicated that the two nitrophenol isomers can be distinguished effectively at GR-CS/GCE. The linear ranges of the calibration curves were0.1μM to140μM for p-NP and1μM to240μM for o-NP, with the detection limits of0.09μM and0.2μM, respectively (S/N=3). Thus, the GR-CS is expected to be a promising electrode material for detecting nitrophenol isomers.