Fabrication of Fe-oxide@Silica@Gold (core/shell/shell) in Order to Development of Biomarkers

Mohammad-Beigi, Hossein | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41293 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Yaghmaei, Soheyla; Arpanaei, Ayyoob; Roosta Azad, Reza
  7. Abstract:
  8. The aim of this work is fabrication of magnetite@silica@gold particles. Study of the effect of pH showed that increasing pH from 9 to 12 resulted in a decrease in the size of magnetite nanoparticles from 7.9±1.38 nm to 5±0.64 nm. The TEM results indicated that modifying magnetic nanoparticles with sodium citrate prior to coating with silica leads to a narrow particle size distribution (275±16.1nm) and less number of silica nanoparticles without any magnetite core. Three methods were applied for attachment of gold nanoparticles seeds onto the silica surface: 1) use of an electrostatic interaction between positively-charged aminated silica and negatively-charged gold nanoparticles surfaces, 2) use of a covalent bond between thiol groups on the silica surfaces and gold nanoparticles, 3) and finally use of formation of an amide bond between amine groups on the silica and carboxyl groups on the gold nanoparticles surfaces. In order to attach gold nanoparticles, silica surface was functionalized with amine or thiol groups. The highest increase in zeta potential value (more positive charges on the surface) was obtained under condition in which the concentration of 90 mM EDS was used compared to that with 25 to 180 mM.When a high concentration of EDS (180 mM) was applied a non-homogeneous coverage of gold nanoparticles on the surface and a tendency of formation of aggregates by gold nanoparticles on some specific regions of magnetite silica spheres was observed. Higher coverage and aggregation of gold nanoparticles over silica surfaces were observed at a lower pH in study of the effect of pH (pH values of 7, 5 and 3) on attachment of gold nanoparticles onto aminated surface of magnetite@silica nanocomposite. Optical properties and TEM results on synthesized nanocomposites revealed that the first method (use of the electrostatic interaction) is more effective than two other methods to attach gold nanoparticles on the silica surface. Finally, the Au shell was formed onto the magnetite@silica@Au-seeds particles. The absorption peak of Au shell particles shifted to the NIR region
  9. Keywords:
  10. Nanoparticles ; Magnetite ; Silica ; Gold ; Core-Shell Nanostructure

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