Construction And Application Of Dopamine Electrochemical Sensor Based On Conductive MOFs/Carbon Composites

Dopamine（DA）is an essential neurotransmitter in the human central system,and its abnormal concentration has been associated with a variety of neurological diseases.Therefore,it is of great significance to explore a simple,sensitive and accurate method for the determination of DA concentration.Among them,electrochemical analysis technique as an effective means to detect DA,has the advantages of good selectivity,high sensitivity,fast analysis and easy operation,etc.However,the bare glassy carbon electrode has low sensitivity and poor selectivity,which often cannot meet the requirements of practical applications.Therefore,it is urgent to develop new materials to construct electrochemical sensors with high sensitivity and selectivity for DA detection.Among them,electrically conductive metal organic frameworks（ECMOFs）have changed the shortcomings of poor conductivity of conventional metal organic frameworks（MOFs）,which have abundant active sites,large specific surface area,controllable and diverse structures,and good conductivity.These characteristics provide new ideas for the design and construction of higher performance DA electrochemical sensors.Although MOFs can be used as electrode modifiers alone,they suffer from poor water stability,easy to fall off the electrode surface,and weak anti-interference ability,which make it difficult to meet the requirements of trace determination of dopamine in complex samples.In view of this,two kinds of DA electrochemical sensors based on conductive MOFs/carbon-based nanomaterials were designed and constructed in this paper to improve the selectivity and stability of analytical detection.The details of the study are as follows:（1）The conductive MOF material（Cu₃（HITP）₂）was prepared based on the synthetic2,3,6,7,10,11-hexaiminotriphenylene（HITP）ligand.The Cu₃（HITP）₂/MWCNTs nanocomposites were synthesized by recombination of Cu₃（HITP）₂and multi-walled carbon nanotube（MWCNTs）.The structure and morphology of Cu₃（HITP）₂/MWCNTs were characterized by XPS,XRD,SEM and FTIR.The results show that Cu₃（HITP）₂has excellent electrical conductivity,large specific surface area and good crystallinity.Compared with a single MOF material,the addition of MWCNTs significantly improved the dispersibility and stability of Cu₃（HITP）₂/MWCNTs in water.The electrochemical performance of the sensor was studied by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）.The results show that the sensor has good electrocatalytic performance for the oxidation of ascorbic acid（AA）,dopamine and uric acid（UA）,and can be used for the simultaneous detection of three biomolecules.Under the optimal experimental conditions,the linear ranges of AA,DA and UA were 5～1000μM,0.5～450μM and 1～500μM,and the detection limits were 1.5μM,0.18μM and 0.49μM（S/N=3）,respectively.In addition,the designed electrochemical sensor has good reproducibility and anti-interference ability,and can be used for the simultaneous detection of AA,DA and UA in human serum and urine samples.（2）Cu₃（HITP）₂/GO nano-composite was prepared by the combination of conductive Cu₃（HITP）₂and graphene oxide（GO）.Cu₃（HITP）₂/GO/GCE was prepared by modifying Cu₃（HITP）₂/GO on the surface of glass carbon electrode.Then,the GO in the composite was converted to reduced graphene oxide（ERGO）by electrochemical reduction method,and Cu₃（HITP）₂/ERGO/GCE was obtained.The materials were characterized by EDS and FTIR.The large conjugated system formed by theπ?πinteraction between conductive Cu₃（HITP）₂and ERGO significantly accelerated the electron transport rate and provided sufficient catalytic active sites.The electrochemical performance of the sensor was investigated by CV and DPV.The results show that Cu₃（HITP）₂/ERGO/GCE has good electrocatalytic performance on the oxidation of dopamine and acetaminophen（ACOP）.Under the optimal experimental conditions,the sensor realizes the selective detection of DA and ACOP,with wide detection ranges（DA:0.05～150μM;ACOP:0.1～100μM）,low detection limit（DA:9n M;ACOP:14 n M）,strong anti-interference ability and high stability.This proposed sensor has been successfully applied to the simultaneous determination of DA and ACOP in human serum samples.