Preparation Of Modified Graphene、Carbon Nanotube Electrochemical Sensors And Their Performance Study

Electrochemical and optical sensors based on Graphene-derived materials（GDMs）and carbon nanotube have been widely developed as analytical devices in recent years since they have improved the detection and quantification of numerous food and small environmental molecules showing high sensitivity,selectivity,and lower detection limits.The detection enhancement can be possible either because GDMs or carbon nanotube offer a greater surface area for the recognition molecule attach or increase the signal-to-background ratio due to its physicochemical properties.（1）A glassy carbon electrode（GCE）decorated with TiO₂-Zn O-r GO nanocomposites prepared by UV irradiation was designed for simultaneous determination of the selectivity of quinol isomers.During UV irradiation,the photogenerated electrons in TiO₂ and Zn O are transferred into graphene oxide,which promotes the reduction of graphene oxide to reduced graphene oxide.The TiO₂-Zn O-r GO nanocomposite exhibits selectivity for hydroquinone（HQ）and catechol（CA）simultaneously and exhibits excellent sensing performance,benefiting from the functional properties of different components in the material and synergistic effects.In the presence of 40μMol L^-1 of the isomer,the selectivity assay for the two quinol isomers was linear in the range of 5-500μMol L^-1.The linear ranges for the two diphenol isomers were 0.1-100μMol L^-1 and 100-500μMol L^-1,and the detection limits for HQ and CA were 0.03μMol L^-1 and 0.05μMol L^-1,respectively.In practical water sample analysis,TiO₂-Zn O-r GO/GCE also showed good stability and recovery.（2）An efficient and environmentally friendly UV irradiation method was used to synthesize TiO₂-Ag-r GO nanocomposites for electrochemical sensing of meloxicam（MEL）.The morphology,chemical composition and structure of the material were investigated with different characterizations,and the electrocatalytic activity of MEL on the material was investigated.Due to the coordinated action of the three materials,the sensor exhibited a wide linear range(0.5-100μMol L^-1)and a low detection limit(0.152μMol L^-1),and was successfully applied to real sample determination.（3）A new and highly conductive covalent organic frameworks（COFs）was designed and synthesized by amine-aldehyde condensation reaction between 1,3,6,8-tetrakis（4-formylphenyl）pyrene and melamine.The obtained COFs were then coupled with nitrogen doped carbon nanotubes（N-CNTs）and employed as a novel sensing platform for the selective and simultaneous quantification of xanthine（XA）and hypoxanthine（HX）.A series of fundamental characterizations confirmed the surface morphology,structure,and compositional properties of the COFs/N-CNTs nanocomposites.Further electrochemical investigations showed that the COFs/N-CNTs nanocomposites modified electrode enabled simultaneous assay of XA and HX sensitively.Under the optimum experimental conditions,using differential pulse voltammetry,the low detection limits of 0.031?Mol L^-1 and 0.126?Mol L^-1 for XA and HX are achieved,respectively.The linear ranges for XA and HX are 0.1 to 100?Mol L^-1and 0.5 to 500?Mol L^-1.With excellent selectivity,repeatability and stability,the proposed method was successfully applied for the quantification of XA and HX in human urine and fish samples with recoveries of 98.2%–104.9%.The work not only provides a simple method to detect XA and HX simultaneously,but also offers insights for design and applications COFs-based materials in electrochemical sensing.