The Construction Of Three-Dimensional Graphene And Its Sensing Application

Graphene is the new two-dimensional material with unique physicochemical properties,including high conductivity,high chemical stability and a very high theoretical specific surface area.Graphene oxide as the derivative of graphene has gained widespread attention.It has the advantage of dispersion in aqueous solution,easy processing,and controllability.By making full use of the excellent characteristics of each component and combining graphene oxide with other functional materials,it can be applied to the development of electrochemical sensors.However,the reduced graphene oxide prepared by using graphene oxide is prone to agglomeration.This makes the specific surface area of the reduced graphene oxide much lower than the theoretical value,which is detrimental to the adsorption of the substance to be tested and the electron transport of the electroactive substance.Constructed graphene into three-dimensional can effectively prevent graphene agglomeration,increase the specific surface area utilization,accelerate electron transfer and the adsorption of the analyte.In this thesis,graphene hydrogels were constructed by metal ion,pyrrole monomer and 3,4-ethylene dioxy thiophene monomer,then,sulfur and nitrogen atoms were doped by hydrothermal or microwave methods.The three-dimensional doped graphene was further applied to electrochemical sensors.The main contents are as follows:1.A three-dimensional sulfur/nitrogen co-doping graphene was prepared via hydrothermal method from pyrrole/Co-induced graphene oxide hydrogel.Sulfur/nitrogen co-doping occurred in the subsequent hydrothermal process and Lcysteine was used as reducing agent.The obtained 3D sulfur/nitrogen co-doped graphene was further dried through direct evaporation,without freeze-drying.This newly fabricated 3D sulfur/nitrogen co-doped graphene was used in the simultaneous detection of catechol and hydroquinone.It showed good discrimination with low detection limits of 0.28 and 0.15?M,respectively.2.Polypyrrole/graphene composite was prepared via microwave-assisted hydrothermal from pyrrole-induced graphene oxide hydrogel.Pyrrole was proved polymerized on the surface of graphene.This composite was used for the detection of dihydroxybenzene.enhanced electrochemical response and good peak separation can be obtained.The detection limit of the two dihydroxybenzenes was 0.88?M for hydroquinone and 0.69?M for the catechol,respectively.3.EDOT/Co-induced graphene oxide hydrogel was used to prepare ESNGO via microwave treatment.Where L-cysteine was used as doping/reducing agent.For comprision,pyrrole/Co-induced graphene oxide hydrogel was also ultilized.The threedimensional graphene was post-treated by natural drying and freeze-drying,respectively,and used in the detection of phoxim,showing good response.The threedimensional graphene after freeze-drying pocessess a large background current for the loose structure,which would weaken the response signal of phoxim.Under the optimal experimental conditions,the detection limits of phoxim by the obtained sensors were 0.10?M and 0.085?M,respectively.