Graphene Based Electrochemical Sensor And Its Application In The Determination Of Phenols

Hydroquinone(HQ, 1,4-benzenediol) and catechol(CC, 1,2-benzenediol) are two isomers of phenolic compounds. With the rapid development of industrialization, a growing number of phenolic contaminants into the soil and water systems, which greatly harm to the environment and are serious worldwide threat to human health. According to the phenols guideline value made by both the US Environmental Protection Agency and the European Union, the maximum amount of phenols in wastewater allowed is lower than 1 ppm. Therefore, it is rather necessary to develop highly sensitive and simple analytical methods for the determination of HQ and CC simultaneously. Graphene, emerging as a novel material, has received increasing attention due to its unique physicochemical properties(high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). In this thesis, we studied the methods to prepare graphene and graphene-based composite. Meanwhile, the electrochemical properties of graphene-based materials were carried out. The main points of this thesis are briefly summarized as follows:(1) Graphene oxide(GO)was synthesized from natural graphite flakes by Hummers method. Fe3O4 microspheres were synthesized by solvothermal method. The Fe3O4 microspheres were well-distributed on the GO surface after ultrasonic vibration. Meanwhile, high-quality laser reduced graphene(LRG) which is successfully prepared by a consumer-grade laser pen(< $10). Scanning electron microscopy(SEM), atomic force microscope(AFM), X-ray photoelectron spectroscopy(XPS), Raman spectrum and X-ray diffraction(XRD) were use to explore the morphology and chemical structure of GO- Fe3O4 and LRG.(2) A novel sensor for sensitive determination of HQ and CC was proposed via using Fe3O4 microspheres-graphene oxide(Fe3O4-GO) composites by which the glassy carbon electrode(GCE) was modified and further encapsulated with chitosan( Chit-Fe3O4-GO/GCE). The excellent electrocatalytic performance is probably related to the strong synergistic effect of the composites. Our proposed sensor shows a wide linear response for HQ and CC in the concentration range of 1.5 to 150 μM, 1 to 410 μM with detection limit(S/N = 3) of 20 and 250 n M, respectively. Additionally, the sensor exhibits good selectivity and stability in tap water samples.(3) A green, fast and facile approach for the preparation of graphene is proposed for constructing an electrochemical sensing platform. The fabricated platform is applied for the simultaneous determination of HQ and CC based on LRG. The performance of LRG modified electrode shows the excellent electrocatalytic activity toward the redox reaction of HQ and CC. Under the optimized condition, the calibration curves for HQ and CC were obtained in the range of 1 to 300 μM, 2 to 300 μM, with detection limits(S/N = 3) of 0.5 μM and 0.8 μM, respectively. Therefore, our study may provide a promising sensing platform for a variety of electroanalysis applications.