Construction Of A Dopamine Electrochemical Sensing Platform Based On Metal Sulfide Or Hydroxide Composite Membrane

Dopamine（DA,3,4-dihydroxyphenylalanine）is one of the most important neurotransmitters in the brain of humans and animals,which is crucial for maintaining the normal operation of life,improving mood and energy.Therefore,the quantitative analysis of dopamine and its related studies are crucial to ensure the health and diet safety of the public.With the development of science and technology,chromatography,spectroscopy and other traditional detection technologies,such as expensive instruments,complex sample pretreatment and time-consuming,make it difficult to meet today’s requirements for online monitoring and fast measurement.In contrast,electrochemical detection technology has the advantages of simple method,economy,high sensitivity and fast field analysis,and has been widely used in the determination of various substances.Electrode modification materials determine the performance of the electrochemical sensors.In order to realize the rapid,accurate and sensitive detection of DA,three new chemical modification electrodes are prepared,the DA electrochemical sensing platform is constructed,and the corresponding electrochemical analysis method is established.The specific research work is as follows:（1）The cobalt iron Prussian blue analog（Co-Fe PBA）was first prepared by coprecipitation and then converted into CoS₂-Fe S₂decorated hollow nitrogen-doped carbon nanotubes by high temperature vulcanization（CoS₂-Fe S₂/HNCC）.By integrating dual-phase metal sulfides and a nitrogen-doped carbon matrix,nitrogen-doped carbon materials can improve selective adsorption of dopamine and conductivity of electron,the interaction between Co²⁺and Fe²⁺can promote the charge transfer rates.This hollow nanocubic structure provides rich catalyticcenters,enhanced conductivity,large surface area,and 3D-porous channels,which all contribute to the adsorption and catalysis of dopamine.The CoS₂-Fe S₂/HNCC/GCE demonstrates excellent electrocatalytic activity for DA.Under the optimal parameters,the electrochemical sensor exhibits a wide detection range(0.05～90μmol L^-1),a low limit of detection(9.3 nmol L^-1,S/N=3),and a high sensitivity(91.6μAμmol^-1L cm^-2)along with excellent selectivity,reproducibility,reusability and stability.This method has also been applied for the detection of dopamine in human urine samples and displays satisfactory results.（2）A layered double-transition metal hydroxide nanosheet material（CoAl-LDH/CC）was synthesized on an acidified carbon cloth（CC）by a one-step solvent thermal method.Then put into a sodium hydroxide（Na OH）solution for etching,and finally potassium ferricyanide was added to partially convert the CoAl-LDH nanosheets in situ into PBA nanoparticles with three-dimensional structure.The enhanced hydrophilic of CC after nitrfication accelerates the mass transfer rate.The etched LDH surface is rough and irregular,increasing the active site.The 2D layered nanosheets can accelerate electron transfer.Meanwhile,the PBA nanoparticles effectively prevent the accumulation of 2D materials and promote the rapid diffusion of ions.Therefore,the Co-Fe PBA@LDH_e/CC modified electrodes provide more active sites for dopamine and showed good electrocatalytic properties for DA.Under the optimal parameters,DA was quantitatively detected using i-t detection technology,and the results show that the Co-Fe PBA@LDH_e/CC constructed electrochemical sensing platform has a wide detection range(0.05～110μmol L^-1),low detection limit(13.8 nmol L^-1,S/N=3),and a high sensitivity(322.2μAμmol^-1L cm^-2)along with excellent selectivity,reproducibility,reusability and stability.（3）CoAl-LDH was prepared by hydrothermal method.Then put into Na OH solution for etching,and combined with silica gold nanorod coated（Au@Si O₂）to obtain CoAl-LDH_e@Au-Si O₂material for modifying GCE.The etched two-dimensional layered nanosheets have rough and irregular surfaces and can accelerate electron transfer.The coating of Si O₂can disperse the easy aggregation of Au nanoparticles evenly,effectively prevent the aggregation of Au nanoparticles and ensure the full use of Au nanoparticles,and effectively improve the catalytic performance of CoAl-LDH_e@Au-Si O₂composites for DA.The CoAl-LDH_e@Au-Si O₂/GCE showed good electrocatalytic activity against DA.Under the optimal parameters,the electrochemical sensing platform constructed based on this CoAl-LDH_e@Au-Si O₂/GCE has a wide detection range for detecting DA(0.5～850μmol L^-1),the detection limit was 70.5 nmol L^-1（S/N=3）and the sensitivity was377.6 n Aμmol^-1L cm^-2along with excellent reproducibility,reusability,and stability.