Research On Near-infrared Electrochemiluminescence And Bismuth Film Based Ratiometric Electrochemical Sensors

Nanomaterials have excellent physical and chemical properties,demonstrating good application prospects in lots of areas.The generation of electrochemiluminescence（ECL）is an excitation process,which mainly including the radicals formation processes during the electrochemical reaction and the luminescence produced by the formation of excited states.ECL is the smart combination of chemiluminescence and electrochemistry techniques,bringing ECL for various advantages,such as high sensitivity as chemiluminescence,ease control of electrochemistric reaction.Hence,the ECL analytical technique is being developed rapidly.Anodic stripping voltammetry analysis methods offers the advantages of simple instrument,high sensitivity,fast analysis speed,ease operation,multi-component detection.The have found extensive applications in the determination of heavy metal ions and biomarkers in biometallization strategy.In this thesis,gold and silver nanoclusters were used as the near-Infrared ECL luminophores in immunoassay.By using Bi film as the current enhancer and inner reference for ratiometric measurement,several nanomaterials-based chemically modified electrodes were developed to determine heavy metal ions as well as biomarkers.The main contents are outlined below.1.Near-infrared electrochemiluminescence immunoassay with biocompatible Au nanoclusters as tagsNear infrared（NIR）ECL luminescent materials have aroused widespread interest.But only a few of NIR ECL luminescent materials with an ECL spectrum exceeding 800 nm in an aqueous medium is reported.In this work,we used methionine（Met）as a stabilizer to prepare gold nanoclusters（Met-AuNCs）as a NIR ECL luminophore.In the presence of triethanolamine（TEOA）as a co-reactant,the anodic ECL emission peak in aqueous solution achieves to 835 nm.The ECL intensity of Met-AuNCsis 75 folds of the traditional AuNCs with bovine serum albumin as capping agents.The high-efficiency NIR ECL behavior and good biocompatibility of Met-AuNCs to make it as a useful NIR ECL luminophore in the"signal on"type immunoassay.By using alpha fetoprotein（AFP）as the model analyte and Met-AuNCs as tags,the"signal on" NIR ECL immunoassay exhibited a linearity range from 3 fg m L^-1 to 0.1 ng m L^-1 with a limit of detection（LOD）of 1 fg m L^-1 as well as desired selectivity.2.Spectrum-resolved triplex-color electrochemiluminescence multiplexing immune-assay using Ag nanoclusters as near-infrared emitterSilver nanoclusters（Ag NCs）as a very promising nanomaterials have been demonstrated good potential applications in in biological analysis.In the applications as ECL luminophore,only the cathodic ECL of Ag NCs with the emission peak in the visible region is reported.The anodic ECL of Ag NCs with the emission peak in the near infrared region is absent.In this work,bovine serum albumin（BSA）-stabilized Ag NCs were prepared.By using triethanolamine as the co-reactant,BSA-Ag NCs/GCE exhibit strong anodic ECL with the spectral emission peak achieved to 904 nm.A sandwich typed NIR ECL immunosensor is constructed with the BSA-Ag NCs as tags and cardiac troponin I（c Tn I）as model analyte.To ensure the electron transfer efficiency,the composite of carbon nanotubes-Ti O2 NPs-chitosan was served as the conducting bridge between the basic electrode and the ECL luminophores labeled on the secondary antibodies and co-reactant accelerator,enhancing the ECL intensity by a factor of 16.The NIR ECL immunosensor exhibits a linearity range from 0.03 pg m L^-1 to 0.1 ng m L^-1,with the LOD of 7.4 fg m L^-1.Afterwards,the excellent NIR ECL property of BSA-Ag NCs was applied in spectrum-resolved triplex-color ECL multiplexing immunoassay by combining with Cd Se spectrum-resolution was obtained in the simultaneous determination of three biomarkers.Carbohydrate antigen 125（CA125）,carbohydrate antigen 19-9（CA19-9）and c Tn I were used as model target antigens.Cd Se QDs,Cd Te QDs and BSA Ag NCS were used as the tags in the signal second antibodies for the three antigens,respectively.The integral ECL intensities of the three ECL emitters in different wavelength regions were measured simultaneously by a spectrum-resolved ECL detection system.The LOD were 35mU m L^-1（CA125）,87mU m L^-1（CA19-9）and 17 fg m L^-1（c Tn I）,respectively.3.A ratiometric electrochemical sensor for lead ion based on bismuth film coated porous siliconPorous silicon is an attractive nanomaterial with unique physical and chemical properties,especially its highly adjustable porosity,high surface area,biocompatibility and biodegradability.The ratiometric methods have unique advantages,such as built-in self-calibration features,good reliability,and high stability.They have been used in optical and electrochemical sensors.In this work,PS NPs were prepared by electrochemical etching single-crystal silicon disk in a solution containing HF,and H2O2.The as-prepared PS NPs were used to modify glassy carbon electrode（GCE）for the determination of Pb（Ⅱ）.By using Bi film as the current enhance and ratio of the peak current between Pb（Ⅱ）and Bi（Ⅲ）as the signal,a ratiomrtic electrochemical senor for Pb（Ⅱ）was developed.In a differential pulse anodic stripping voltammetry（DPASV）,the linear range of the sensor is 0.2-100mg L^-1,with the LOD of 0.09mg L^-1.After stored at 4℃ for 30 days,the current response of PS NPs/GCE to Pb（Ⅱ）is decreased by 7.4%,but the ratiometric current signal is decreased by only 2.1%,showing higher stability and repeatability.This method was used for the detection of Pb（Ⅱ）in real water samples.4.A ratiometric electrochemical sensor for multiplex detection of cancer biomarkers using bismuth as an internal reference and metal sulfide nanoparticles as signal tagsIn this work,we developed a ratiometric electrochemical sensor for the detection of multiplex cancer biomarkers.A conductive polymer film of poly（2-aminoterephthalic acid）（ATA）is electropolymerized on a GCE and doped with carbon nanotubes（CNTs）and mercaptosuccinic acid（MSA）.In the presence of Bi（Ⅲ）,the MSA-CNTs-ATA/GCE modified electrode exhibits sensitive and distinguishable voltammetric responses to Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Hg（Ⅱ）.The dissolution peak of the bismuth film is used as an internal reference for ratio measurement.Using the ratio of metal ion to Bi（Ⅲ）dissolution current peak as a signal indicator,MSA-CNTs-ATA/GCE is used to determint simultaneously Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Hg（Ⅱ）,with the LOD of 0.089,0.13,0.16 and 0.49μg L^-1,respectively.But in the normal non-ratiometric model,the LOD for Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Hg（Ⅱ）are only 0.22,0.27,0.34and 0.91mg L^-1,respectively.In addition,by using metal sulfide（Zn S,Cd S,Pb S or Hg S）nanoparticles as distinguishable signal labels,the proposed ratiometric electrochemical sensor was applied to determine the cancer biomarkers,including carcinoembryonic antigen（CEA）,AFP,CA125 and CA19-9.After the immune recognition reaction,the metal sulfide in the sandwiched immune complex was dissolved by the mixture of H2O2 and HCl.The concentrations of Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Hg（Ⅱ）in the solution were determined by DPASV method to quantify indirectly the concentration levels of CEA,AFP,CA125 and CA19-9,respectively.The LODs for CEA,AFP,CA125 and CA19-9 were 0.23 pg m L^-1,0.11 pg m L^-1,1.4m U m L^-1 and 0.68 m U m L^-1,respectively.The proposed proportional electrochemical method has the advantages of simplified experimental operations,high sensitivity and high reliability,and has a good prospect in detecting heavy metal ions and multiple cancer biomarkers while combining with biometalization.5.An electrochemical sensor based on bismuth film coated Co₃O₄ nanosheets for lead ions determinationCobalt tetroxidenanomaterial is one of the most promising metal oxide materials with a good application prospect.Due to its electrochemical catalytic performance and adsorption capacity,nanomaterials have bene used to prepare chemically modified electrodes.In this work,we developed a simple electrochemical deposition and annealing method to preparenanosheets on an indium tin oxide（ITO）substrate.The ITO electrode modified withnanosheets was used for electrochemical analysis of trace lead ions by DPASV.In the presence of Bi（Ⅲ）as the enhancer,the as-prepared electrode exhibited the linear range of 1-100mg L^-1and the LOD of 0.52mg L^-1.