| Dopamine(DA)is an electroactive catecholamine neurotransmitter,which can directly act on the central nervous system of the human body and regulate a variety of physiological functions.Electrochemical sensors have high sensitivity and fast response time in monitoring neurochemicals.The development of a sensitive and efficient electrochemical sensing platform for the determination of DA is of great significance for the development of clinical and biomedical fields.Three-dimensional(3D)structure is a new form of two-dimensional(2D)planar graphene.In the field of electrochemistry,while maintaining the inherent characteristics of graphene,3D graphene prevents the agglomeration of graphene sheets,so that it has a wealth of mass transfer and conductive channels,which is conducive to the full contact between the analyte and graphene and amplify the electrochemical signals.Therefore,electrochemical sensors based on 3D graphene materials can selectively detect and quantitatively analyze trace amounts of electrochemically active neurotransmitters.In this thesis,spray-drying technology was employed to assemble graphene sheets into 3D microsphere structure.In this process,the polystyrene(PS)spheres and carbon black(CB)nanoparticles were introduced into the graphene sheets by the way of the precursor solution premixing,respectively.The performance of the two kinds of microspheres for DA detection was also investigated.This work mainly includes the following contents:(1)Dopamine electrochemical sensor based on hollow graphene microspheresThe mixed solution of PS and GO was used as the precursor to obtain PS-GO composite microspheres by spray-drying.The PS template was removed by high temperature calcination.At the same time,GO was reduced to obtain 3D-rGO that has porous structure.Subsequently,this material was modified on Pt electrode,which was donated as 3D-rGO.Compared with unassembled rGO nanosheets,the mass transfer and electrical conductivity of 3D-rGO/Pt were greatly improved.In addition,the influence of the mass ratio of PS to GO in the precursor solution on the morphology and electrochemical properties of the microspheres was investigated.The results show that the smaller the ratio is,the more folds are on the surface of the microspheres,and the performance of DA sensing is further improved with the increase of specific surface area.Under the optimal ratio(0.5),the detection range of the DA sensor is 0.5～777μm,and the detection limit is 0.145 μm(S/N=3).Under the coexistence of Glu,UA,AA and other interferences,the sensor can selectively detect DA with good stability,reproducibility and practicability.(2)Dopamine electrochemical sensor based on polydopamine-coated graphene-based composite microspheresA highly sensitive and selective electrochemical sensor based on polydopamine(PDA)-coated material was prepared for the amperometric detection of DA.The coated material is CB-GO(CG)composite microspheres prepared by introducing CB nanoparticles into GO sheets through spray-drying.CB nanoparticles as spacers provide more conductive channels and larger specific surface area,while PDA as modification layer provides more active sites as well as hydrophilicity and stability.The synergistic effect makes the PDA-CG/Pt display excellent electrocatalytic performance towards sensing DA.The linear range of DA detection is 0.2～63 μm,and the detection limit is 0.048 μm(S/N=3).The sensor has good selectivity,excellent reproducibility and stability.In addition,it has been applied to the determination of DA in human serum with satisfactory results. |
