Synthesis Of Functionalized Graphene And Its Application In Electrochemical Detection Of NO₂^- And SO₃^2-

Excessive intake of nitrite?NO₂^-?and sulfite(SO₃^2-)poses a potential threat to human health,and emissions to the environment can cause certain damage to the ecosystem.Therefore,it is highly desirable to develop a method with high sensitivity and selectivity for the detection of NO₂^-and SO₃^2-in drinking water,food and ecosystems.Although the conventional analytical technique has high selectivity and sensitivity,it has the disadvantages of complicated pre-processing,large influence by interferents,cumbersome operation,expensive instruments,and harsh experimental conditions.The electrochemical method can overcome the above disadvantages,and has the advantages of simple operation,high sensitivity,good selectivity,low cost,fast detection,and suitable for on-site detection.Graphene?GN?has been widely used in the field of electrochemical sensors in recent years because of its excellent specific surface area,chemical stability,good electrical conductivity,and high mechanical strength.However,GN slices are easy to aggregate,so it is important to functionalize GN.In this paper,a NO₂^-and SO₃^2-electrochemical sensor was constructed based on functionalized graphene nanomaterials.The main research contents of this thesis are as follows:.We synthesized flower-like gold-molybdenum disulfide-reduced graphene nanocomposite?Au NPs-MoS₂-r GO?by one-step hydrothermal method.The morphology and composition of the nanocomposite were characterized by transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?and X-ray powder diffraction?XRD?.An electrochemical nitrite sensor was constructed based on Au NPs-MoS₂-r GO.The results show that the Au NPs-MoS₂-r GO nanocomposite combines the excellent properties of r GO,MoS₂ and Au NPs,and has synergistic enhancement on electrochemical catalysis activity toward NO₂^-.Sensitivity detection of NO₂^-was performed by chronoamperometry with a linear range of 5 ?M to 5000 ?M and a detection limit of 1 ?M.The sensor shows good reproducibility and stability in the detection of NO₂^-.For real sample detection?kimchi and ham?,the recovery is between 98.0% and 103.2%.,which indicates that the fabricated sensor can be used for detection of NO₂^-in actual samples.NiCoO/N-GN composites were synthesized by one-step hydrothermal method with nitrogen-doped graphene,nickel nitrate and cobalt nitrate used as raw materials.The morphology and composition of the composites were characterized by transmission electron microscopy?TEM?and X-ray photoelectron spectroscopy?XPS?.And the electrochemical sensor of sulfite detection was constructed on the basis of Ni Co O/N-GN.The results show that the Ni Co O/N-GN composites own superior performance than any of the individual component,such as nickel oxide,cobalt oxide and N-GE,and has an enhanced electrooxidation activity towards SO₃^2-sensing procedure.Chronoamperometry was used to quantitive detection of SO₃^2-The linear range was of 3 ?M to 1000 ?M with a low detection limit of 1.6 ?M.The sensor shows good reproducibility and stability in the detection of SO₃^2-.The recovery is between 98.0% and 104.0%.and can be used to detect SO₃^2-in tap water samples.This chapter is the summarization of the previous works.The existing problems are pointed out and the possible solutions are given.Finally,the future of electrochemical sensors in the detection of NO₂^-and SO₃^2-is prospected.