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Electrochemical Detection Of Two Kinds Of Heavy Metal Ions Using Graphene And Bio Bar Code Assay

Posted on:2016-11-08Degree:MasterType:Thesis
Country:ChinaCandidate:J L XieFull Text:PDF
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With the continuous development and progress of nanotechnology, the excellent properties of nanoparticles binding with the ability of DNA to identify molecules have been widely used in the preparation of DN A sensor and many other research areas. We chosed two common nano material like graphene and gold nanoparticles, combined with bio bar code assay and enzyme catalyzed reaction, designed a series of electrochemical DNA sensors for the detection of silver ions and mercury ion in environmental water samples, and an electrochemical sensors for hydrogen peroxide detection in food.1、A novel, wide range based on bio bae code assay and silver enhancer dual signal amplification technology to detect silver ions in aqueous solution. By gold nanoparticles labeled, surface hybridization, combined with silver enhancement technology, to achieve the electrochemical signal amplification. By controlling the time of silver enhancer, we could detect the trace of silver ions with ultra- low background peak current and a wide detection range. The method was simple and had had a high selectivity and sensitivity. Linear range from 5 p M to 50 μM, the detection limit was 3 p M(S/N = 3).2、A simple, sandwich structure based on graphene, gold nanoparticles, bio bar code assay and enzymatic dual signal amplification technology to build an electrochemical DNA sensor for detecting mercury io ns in aqueous solution. This method used graphene as a high electron transfer substrate, in the presence of mercury ions and target DNA, the thymine-mercury(II)-thymine(T-Hg2+-T) complex could make the horseradish peroxidase marked gold nanoparticles-bio bar code DNA complex specific hybridizd with target DNA to form a double-stranded, which lead the numerous horseradish peroxidase combined with the bio bar code DNA through avidin-biotin interaction to draw closer the surface of graphene. This phenomenon enhancd the catalytic signal of hydroquinone. The proposed electrochemical DNA sensors, in the case of coexistence with other metal ions, had a high selectivity and sensitivity. Linear range from 25 p M to 10 μM, the detection limit was 13 p M(S/N = 3).3、A simple, signal-off and reusable electrochemical biosensor was developed for sensitive and selective detection of mercury based on T-Hg2+-T complex and the remarkable difference in the affinity of graphene with double strand DNA(ds-DNA) and single strand DNA(ss-DNA). Our system was composed of ferrocene-tagged probe DNA and graphene. Due to the noncovalent assembly, the ferrocene-tagged probe ss-DNA was immobilized on the surface of graphene nanosheets directly and employed to amplify the electrochemical s ignal. In the presence of Hg2+, the ferrocene- labeled T-rich DNA probe hybridized with target probe to form ds-DNA via the Hg2+-mediated coordination of T-Hg2+-T base pairs. As a result, the duplex DNA complex kept away from the graphene surface due to the weak affinity of graphene and ds-DNA, and the redox current decreased substantially. Meanwhile, the graphene decorated GCE surface was released for the reusability. Under the optimal conditions, the proposed sensor showed a linear concentration range from 25 p M to 10 μM with a detection limit of 5 p M for Hg2+ detection. The strategy afforded exquisite selectivity for Hg2+ against other metal ions in real environmental samples.4、A novel nonenzymatic sensor for hydrogen peroxide(H2O2) is developed based on Nafion/Prussian blue/Ti O2-graphene nanocomposite(Nafion/PB/Ti O2-GR). PB/Ti O2-GR composite was prepared by electrodeposition of PB nanocubes on the surface of Ti O2-GR composite nanosheets and Nafion was used as a stabilizer. The Nafion/PB/Ti O2-GR composite modified glassy carbon electrode(Nafion/PB/Ti O2-GR/GC E) shows good electrocatalytic activity in the reduction of H2O2 and is used as an amperometric sensor. The sensor exhibits a linear response for H2O2 over concentrations ranging from 40 n M to 2 m M with a high sensitivity of 480.97 μA m M-1 cm-2 and a low detection limit(S/N = 3) of 8.6 n M. Additionally, the sensor exhibits long-term stability, good reproducibility and anti- interference. This study provides a new kind of nanocomposite modified electrode for electrochemical sensors.
Keywords/Search Tags:Heavy metal ion, gold nanoparticles, Graphene, Bio bar code assay, Electrochemical DNA sensor
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