Electrochemiluminescence Of Thiolate-protected Gold Nanoclusters And Its Analytical Application

Gold nanoclusters(Au NCs),consisting of several to hundreds of gold atoms,are a category of promising analytical material due to their prominent properties including tunable luminescence,unique electrochemical properties,high stability and biocompatibility.Compared with other ligand-protected gold clusters,thiolate-protected gold nanoclusters are favored by researchers because they have good chemical stability,high electrochemical activity and easy to preserve.In recent years,thiolate-protected Au NCs have a wide analytical application in electrochemistry,fluorescence,electrochemiluminescence(ECL)and so on.Among those applications,ECL application of Au NCs has attracted increasing attention and has become a research hotspot.Compared with other analytical methods,ECL analysis has the advantages of prompt detection,high sensitivity,low background,wide linear range,low detection limit,easy operation and so on.In this paper,the ECL properties of thiolate-protected Au NCs were studied.Thiolate-protected Au NCs were used as ECL emitter,and glassy carbon electrode(GCE)is used as working electrode.Three kinds of ECL sensors have been successfully constructed to detect metal ion and biomolecule.The research in this paper mainly includes the following three aspects:(1)Electrochemiluminescence of N-acetyl-L-cysteine-stabled gold nanocluster and its analytical application for inorganic pyrophosphatase activityIn this chapter,N-acetyl-L-cysteine(NAC)was used as stabilizer to synthesize gold nanocluster(NAC-Au NCs).We used NAC-Au NCs as ECL emitter and established a sensitive ECL sensor for pyrophosphatase activity detection.Due to a high-affinity between NAC-Au NCs and Cu²⁺,the presence of Cu²⁺would quench ECL signal of NAC-Au NCs.Pyrophosphate anion(PPi)can chelate with Cu²⁺with a stronger affinity.So,the introduction of PPi could release Cu²⁺from Cu²⁺-NAC-Au NCs system,resulting in the ECL recovery.After adding alkaline phosphatase(PPase),which can transform PPi into orthophosphate(Pi),the ECL signal of NAC-Au NCs would decrease once again.Based on the above coordination and enzymatic hydrolysis,ECL analysis for PPase activity was established.Due to the high specificity and high efficiency of PPase for PPi,this ECL sensor we constructed has good selectivity and low detection limit(LOD).It can be used to detect PPase activity in human serum.(2)Electrochemiluminescence of glutathione stabled gold nanocluster and its application for Hg²⁺detectionIn order to further improve the ECL performance of gold nanocluster,we synthesized glutathione-stabilized gold clusters(GSH-Au NCs).GSH-Au NCs have better dispersibility and electrochemical activity than NAC-stabilized Au NCs.We studied the ECL properties of GSH-Au NCs and successfully applied them to Hg²⁺detection.Due to the interaction of Hg²⁺with the Au NCs,the ECL signal of GSH-Au NCs was reduced.Based on this phenomenon,we constructed an ECL sensor to detect Hg²⁺.The detection ranged from 0.1?M to 10 m M,and the LOD was 18 n M.This method has good selectivity and stability,which can be used to detect Hg²⁺in tap water.(3)Enhanced electrochemiluminescence of gold nanoclusters via silver doping and its application for ultrasensitive detection of dopamineBased on the above work,we performed silver doping on GSH-Au NCs.we found by doping Ag to GSH-protected Au NCs to form bimetallic clusters(GSH-Ag/Au NCs),the ECL efficiency of Au NCs was greatly improved.Since DA can be oxidized to o-benzoquinone species by SO₄^·-,energy transfer between Au NCs excited state and o-benzoquinone species occurred.Therefore,DA could quench the ECL signal of GSH-Ag/Au NCs.Based on this phenomenal,we constructed a highly sensitive ECL sensor to detect DA.The quenching effect of DA to the ECL signal of GSH-Ag/Au NCs was obvious.This sensor exhibited a good linear relationship at 10 n M to 1 m M,while the detection limit was low,only 2.3 n M.What's more,the sensor we constructed can be used for DA detection in serum,which had certain practical value.