| Electrochemical sensors have the advantages of simple construction andoperation, low cost, high sensitivity, fast analysis and easy miniaturization etc., so itget a very wide range of applications in the fields of clinical medicine testing, foodindustry, industrial process control, agriculture and the environment, pharmacy. Inrecent years, nanomaterials were widely used in building the electrochemical sensinginterface because of its large surface area, high catalytic efficiency, easy tofunctionalize and other physical and chemical properties, which can improve thesensitivity and response speed, extend sensor life. After enormous literature research,we choose the low-dimensional carbon nanomaterials (carbon nanotubes graphene) assignal amplification in consideration of the easy preparation, low cost,environmentally friendly and excellent electrochemical properties. Combining withnanotechnology, nanomaterial fabrication, electrode functionalized modification andmolecule recognition sensing technology, we developed series of highly sensitiveelectrochemical sensing method, which expand the role of low-dimensional carbonnanomaterials in electrochemical sensors as signal enhancement, the main work arelisted as follows:1. A highly sensitive electrochemical assay for silver ion detection based onun-labeled C-rich ssDNA probe and controlled assembly of MWCNTsWe developed a highly sensitive and selective electrochemical sensing methodfor Ag+detection based on Ag+-induced conformational change of cytosine-richsingle stranded DNA(C-rich ssDNA) probe and the controlled assembly of MWCNTs.In the protocol, the gold electrode was firstly modified with a dense16-mercaptohexadecanoic acid self-assembled monolayer (MHA/SAM) film. Thehydrophobic and dense MHA/SAM film isolated the electrode from the electroactiveindicator in the aqueous solution, which resulted in the electronic transmissionblocking. It was eT OFF state. In the presence of Ag+, C–Ag+–C coordination inducedthe conformational change of C-rich ssDNA probe from random-coil structure to foldinto a hairpin structure, which cannot wrap on the surface of the MWCNTs. Then the“naked” MWCNTs can be assembled on the MHA/SAM gold electrode, mediating theelectron transfer between the electrode and the electroactive indicator. It generatedmeasurable electrochemical signals (eT ON). When without Ag+, the ssDNA wrapedMWCNTs can not be assembled on the MHA/SAM electrode for the electrostatic repulsion effect between ssDNA and MHA. The resulting change in electron transferefficiency was readily measured by differential pulse voltammetry at target Ag+concentrations as low as1.3nM for the signal amplification of MWCNTs, the widelinear response range for Ag+detection can be from10to500nM. Moreover, it hasgood selectivity to other environmentally relevant metal ions in real sample detection.Therefore, the developed electrochemical assay is an ideal method for Ag+detectionwith some advantages including sensitivity, selectivity, and simplicity, and low-cost.2. A highly sensitive label-free electrochemical aptasensor for interferon-γ detectionbased on graphene controlled assembly and nuclease cleavage-assisted targetrecycling amplificationWe report here a highly sensitive and label-free electrochemical aptasensingtechnology for detection of interferon-gamma (IFN-γ) based on graphene controlledassembly and enzyme cleavage-assisted target recycling amplification strategy firstly.In this work, in the absence of IFN-γ, the IFN-γ binding aptamer was stronglyadsorbed on the graphene due to the strong π-π interaction. Then the aptamer depersedgraphene could not be assembled onto the16-mercaptohexadecanoic acid (MHA)modified gold electrode because of the electrostatic repulsion effect. Thus theelectronic transmission was blocked (eT OFF). However, the presence of target IFN-γand DNase I leaded to the desorption of aptamer from the graphene surface andfurther cleavage of the aptamer, thereby releasing the IFN-γ. The released IFN-γcould then re-attack other aptamers on the graphene, resulting in the successiverelease of the aptamers from the graphene. At the same time, the “naked” graphenecould be assembled onto the MHA modified gold electrode with hydrophobicinteraction, mediating the electron transfer between the electrode and theelectroactive indicator. Then, measurable electrochemical signals were generated (eTON), which was related to the concentration of the IFN-γ. By taking advantages ofgraphene and enzyme cleavage-assisted target recycling amplification, the developedlabel-free electrochemical aptasensing technology showed a linear response toconcentration of IFN-γ range from0.1to0.7pM. The detection limit of IFN-γ wasdetermined to be0.065pM. Moreover, this aptasensor shows good selectivity towardsthe target in the presence of other relevant proteins.3. β-cyclodextrin polymer functionalized reduced graphene oxide hybrid nanosheets:application for electrochemical determination of amantadine.We developed a simple method for highly sensitive and selective electrochemicaldetection of amantadine based on selective enrichment capability of β-cyclodextrin polymer and good electrochemical properties of reduced graphene. First,β-cyclodextrin polymer (β-CDP) was prepared by the polymerization ofepichlorohydrin and β-cyclodextrin, then, after further chemical reduction in solution,β-CDP/rGO composite was formed. Then the electrochemical active moleculemethyene blue was trapped in the cyclodextrin cavity through hydrophobic interaction.Methyene blue/β-CDP/rGO modified electrode was fabricated for the detection ofamantadine. When in the presense of amantadine, amantadine can take place ofmethylene blue from the cyclodextrin cavity for its better binding ability;electrochemical signal is decreased, so as to realize the detection of the amantadine.In the concentration range of2×10-6~5.0×10-4mol/L, current peak intensity andthe logarithmic of amantadine concentration has a good linear relationship, thedetection limit is2.818×10-7mol/L, The detection method was simple, fast andsenstivie, which further realize the detection of amantadine in complex sample withgood electrochemical response.4. One pot synthesis of Ru(bpy)32+immobilized graphene oxide-silica compositesfilms for constructing of high performance solid-state electrochemiluminescent sensorThe Ru(bpy)32+immobilized graphene oxide (GO)-silica composites wasprepared using one pot synthesis method at room temperature for constructing highperformance solid-state electrochemiluminescent sensor. Tetraethylorthosilicate(TEOS) can hydrolyze and condense on the GO surface through Si-O-Si bond in thewater–alcohol solution of GO and Ru(bpy)32+under sonication at room temperature.During the process, large amounts of Ru(bpy)32+were immobilized inside grapheneoxide-silica composites through electrostatic interaction and physical entrapmen t. Theas prepared Ru(bpy)32+doped GO-Silica composite film (Ru/GO-SiCF) modifiedglass carbon electrode (GCE) showed excellent electrochemiluminescence (ECL)activity, good solubility and stability for the determination of tri-n-propylamine(TPA), which gave a good linear range over1×1011to1×105M with a detectionlimit14.58pmol L1(S/N=3). It was further successfully applied in highly sensitivedetection of dopamine for its ECL quenching to the system. |
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