Preparation Of Multifunctional Gold Nanoelectrode For Electrochemical Enrichment Of Detection Of Dopamine

Compared with traditional-sized electrodes,nanoelectrodes have a smaller size(<100 nm),and therefore have excellent electrochemical characteristics,such as high mass transfer efficiency,small background current,and small solution resistance.Therefore,the nanoelectrode is a preferred tool for basic electrochemical research and electrochemical sensor applications.In the past few decades,with the development of nano-electrochemical analysis,the preparation and detection methods of nanoelectrodes for analytical applications have been the subject of much research.At present,the multifunctional detection technology of nanoelectrodes and the simplicity,efficiency,and repeatability of preparation are still facing huge challenges,especially the single measurement model and technology can no longer meet the complex detection environment and ensure the comprehensive measurement.Based on that,this paper mainly introduced the deposits gold on the tips of carbon nanoelectrodes by electrochemical methods to prepare multifunctional gold nanoelectrodes of different structures and types and applied these nanoelectrodes to small neurotransmitters with electrical activity,such as the dopamine detection.The main research contents of this paper include the following four aspects:1.The gold nanoelectrode and the nanopore-gold nanoelectrode are prepared on the tip of the carbon nanoelectrode by controlling the deposition time and the deposition current of the gold deposition process.The prepared two gold nanoelectrodes have different structures.The morphology and electrochemical characteristics of these different types of gold nanoelectrodes were characterized by SEM(Scanning Electron Microscope),electrochemical CV(Cyclic Voltammetry),and DPV(Differential Pulse Voltammetry).The results show that the gold nanoelectrodes obtained by controlling the deposition current(40 pA)have good repeatability and good electrochemical performance.Besides,the nanoporegold nanoelectrode obtained by controlling the deposition time(10 s)has open a nanopore and a complete gold nanoelectrode,and which also has good electrochemical performance.The integration of the nanopore and the gold nanoelectrode makes the nanoelectrode have a multi-functional application prospect.2.The AC dielectrophoresis(AC DEP)generated by applying an AC voltage(20 MHz,20 V)on the gold nanoelectrodes is used to study the electrochemical signal changes and differential detection after the rapid enrichment of dopamine(DA)and serotonin(5-HT).The results show that using the AC DEP enrichment method can quickly achieve the enrichment of the two and enhance the electrochemical response.After enrichment of the mixture of DA and 5-HT,it was found that the adsorption rate of DA on the nanoelectrode was significantly faster than that of 5-HT,indicating that the two form a competitive adsorption electrochemical behavior under the mixture conditions.Besides,the gold nanoelectrode also has a good Raman active substrate.The introduction of silver nanoparticles(AgNPs)as capture particles and enhancement factors of DA and 5-HT,and combined with the AC DEP enrichment method,the Raman signals of DA and 5-HT were successfully enhanced and distinguished in the mixture of the two.Finally,the gold nanoelectrode can also obtain an enhanced electrochemical response after enrichment in serum.3.The nanopore-gold nanoelectrode was applied to the selective detection of DA.DA molecules are selectively enriched in the vicinity of the gold nanoelectrode through the nanopore,and the gold nanoelectrode is used to measure the electrochemical response changes before and after enrichment.The results show that the nanopore-gold nanoelectrode has a wide dynamic range of the electrochemical response to DA(0 ~ 600 nM),the Detection of Limit(LOD)be considered as low as 10 nM.Besides,using the nanopore enrichment method with applying-400 mV at the nanopore,nanopores can rapidly and selectively enrich positively charged DA molecules in a short time(5 min).In the presence of ascorbic acid(AA),the electrochemical response of DA can be enhanced in the mixture.Moreover,the nanopore-gold nanoelectrode is also suitable for Raman measurement.Both nanopore enrichment and AC DEP enrichment can enhance the Raman signal of DA,and AC DEP enrichment is more efficient than nanopore enrichment.The AgNP@DA agglomerate microspheres(the diameter is about 20 ?m)produced at the apex of the nanoelectrode demonstrate the effectiveness of the AC DEP enrichment effect.The movement state of AgNP@DA at the nanopore was detected by recording the current-time traces curves.The prepared nanopore-gold nanoelectrode has the advantages of integrating multiple detection and analysis technologies and the potential for sensitive detection of analytes.4.Based on the advantages of molecular imprinting in identifying specific molecules,the polypyrrole(as the monomer)and DA(as the template)molecule were electrochemically polymerized at the apex of the gold nanoelectrode.The preparation of polypyrrole molecularly imprinted ultramicroelectrode was applied to the selective detection of DA.The electrochemical results show that this ultramicroelectrode has good discrimination,high sensitivity,and a wide detection range(4 ~240 ?M)for DA,and the detection of limit is 0.975 ?M.The electrochemical results show that ultramicroelectrode still have good selectivity for DA in the presence of five other interfering molecules(5-HT,NE,EPI,AA,and UA).The use of electrochemical detection allows simple and rapid selective detection.Besides,the electrochemical response and the Raman signal-to-noise ratio of DA can be enhanced by applying a DC bias voltage on the electrode.The imprinting effect of DA molecules in the imprinted structure was studied by combining Raman spectroscopy.After DC enrichment,DA molecules quickly occupied the imprinted sites,which dramatically increases of the Raman signal.