| Gold nanoparticles(AuNPs) possess excellent optical properties and strong surface adsorption. They have many properties such as strong surface plasmon resonance, surface plasmon resonance fluorescence, surface enhanced Raman, and can be used for a wide range of Biomarkers, Molecular recognition, genetic detection and metal ions detection. Electrochemical biosensing of DNA hybridization is a novel technique with the advantages of being simple, reliable, cheap, sensitive and selective for genetic detection, and it can be compatible with DNA biochip, and they are expected to have a broad prospect of application in clinic examination of inherited diseases and drug screening.Colorimetry methods for detection of metal ions were widely used because of its fast detection, ease of operation, and low cost. Gold nanoparticles have special properties, are idle materials in colorimetry methods for detection metal ions.Core-shell alloy nanoparticles have special chemical, optical and electrical properties for its difference in composition, size and structure and are thus widely used in electronic, catalytic, isolation and biologic diagnosis areas.Combining these aspects, this thesis use gold nanopartical based ion transducer to detect metal ions and DNA, and alloy nanoparticles of Au@SiO2and Fe3O4@SiO2was prepared.The concrete research work of this dissertation can be divided into three chapters as follows:Chapter2. A method employing electric-chemical sensor for detection DNA was developed. This method use bio-barcode system to amplify and transfer target DNA signal to mercapto-DNA that can be modified to electrodes. RuHex cations work as electrical-chemical active agent and can be absorbed to anionic phosphate of DNA strands through electrostatic effect. Through DNA hybridization and in the presence of DNA functionalized gold nanoparticles the mercapto-DNA was reconstructed which resulted in a great increase in the amount of DNA loaded on the electrode and thus more RuHex cations were absorbed. This method first amplify DNA signal through bio-barcode system and further amplify the signal through nano self-assemble, which substantially increase the DNA detection limit. The result showed that this method can detect DNA of1pM. This method combined the advantage of bio-barcode system and electrical-chemical technique and has potential for future applications.Chapter3. We have developed two sensors for detecting metal ions. Both sensors showed good water-soluble and stability.1-Gold nanoparticles(AuNPs) exhibited high selectivity to Hg2+and can detect Hg2+with the concentration of1μM by naked eye, the limit of detection can be further enhanced to400nM by ultraviolet-visible(UV-vis) spectra. Under naked eye,2-AuNPs had a distinct colour change after metal ions (Hg2+, Fe3+, Al3+, Fe2+and Cr3+)(100μM) was added respectively. When the concentration of metal ion is less than10μM,2-AuNPs also exhibited high selectivity to Hg2+and can detect Hg2+with the concentration of1μM by UV-vis spectra. Thorough investigation indicated that the mechanism of the colorimetric responses was mainly coordination effect of the modified organic molecules with metal ions and had little relationship with the change of ionic strength and pH value.Chapter4. Core-shell nanoparticles of Au@SiO2and Fe3O4@SiO2were prepared. Hydrothermal synthesis of Fe3O4magnetic nanoparticle through controlling the substrate concentration, reaction temperature and reaction time yields two kinds of uniform sized products of170nm and220nm. Using modified Stober method the Fe3O4surface was coated with SiO2, through optimization of water-ethanol ratio, pH, TEOS amount, substrate concentration and reaction time the thickness of SiO2layer was controlled. Different sized gold nanoparticles was prepared through chemical method and seeding method, hydrolyzed through TEOS, and coated with SiO2. The thickness of the SiO2layer was controlled through optimization of the water-ethanol ratio, pH, TEOS amount, substrate concentration and reaction time. |
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