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Synthesis of Carbon Nanostructure-Metal Nanoparticles Composites and Investigate their Application as a Modifier in Electrochemical Mesurments

Hosseininassab, Niloufar | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46089 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry Science
  6. Advisor(s): Shahrokhian, Saeed
  7. Abstract:
  8. In the first part, metallic nanoparticles were synthesized on the different carbon nanostructers platform such as nanodiamond and graphene sheet using electrochemical and chemical methods. The prepared composite film were characterized by electron microscopy, spectroscopy and electrochemical techniques. The synthesized nanocomposite were applied as a modifier in order to prepare electrochemical sensors for determination trace amount of important pharmaceutical and biological compounds.In the first work, Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was synthesized with chemical method. The surface morphology and the nature of the composite were investigated. The sunthesized composite (AgNPs-NDG) was used for modification the surface of PGE for voltammetric determination of thioridazine (TR). A remarkable enhancement in the microscopic area of the electrode together with strong adsorption of TR on the surface of electrode resulted in a considerable increase in the peak current of TR. Under the optimal conditions, the modified electrode showed a wide linear response to the concentration of TR in the range of 0.08–100mM with a detection limit of 0.01mM.In the second work, a simple electrochemical method by applying constant potential were used to symthsize graphene nanosheets and carbon nanospheres (GNS–CNS) nanocomposite from graphite rods. After studying the morphology of the composite, Pt nanoparticles (PtNPs) were simply electrodeposited onto the GNS–CNS-coated glassy carbon electrode. Scanning electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry (LSV) techniques were used to characterize the prepared modified electrode. By the aim of cyclic voltammetry techniques, the electro-oxidation of cefepime was investigated on the surface of prepared sensor. The effect of the electrodeposition conditions, such as salt concentration and deposition time, on the response of the electrode was studied. Under optimal conditions, the modified electrode showed high sensitivity (b(CP)= dIp,a(CP)/d[CP] =1747.2 nA nM-1), a low detection limit (LOD (CP)=1.2 nM, S/N=3) and a wide linear dynamic range (8 nM to 6mM) for the voltammetric determination of CP. The prepared electrode was successfully applied for the accurate determination of trace amounts of CP in pharmaceutical and clinical samples.In the tired work, a glassy carbon electrode (GCE) was modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The scanning electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry (LSV) techniques were used for the characterization of the prepared modified electrode. The modified electrode was used for determination ceftriaxone in the presence of lidocaine. Cause, the efficiency of proposed method was highly affected by experimental factors, a factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01–10.00μM with a detection limit of 9.01 nM. The results prove that the modified electrode is also suitable for the determination of CFX in pharmaceutical and clinical preparations.
    In the fourth work, graphene oxides sheets were synthesized and investigated with different techniques. The BSA was immobilized on the surface of GCE which was modified with the thin layer of graphene oxides sheets. The presence of graphene oxide sheets caused a remarkable increase in the surface area of the electrode. Consequently, a huge amount of BSA can be loaded on the surface of the electrode. The proposed biosensor was used for impedimetric determination of ibuprofen. The enhancement in electron-transfer resistance (Ret) values was linearly proportional to the concentration of IBP in a wide dynamic range of 0.01- 100 nM, and the limit of detection was 0.75 pM in phosphate buffer solution (PBS). The prepared electrode was successfully employed for accurate determination of trace amounts of IBP in pharmaceutical and aqueous samples.In the fifth work, the nanopipttes were pulled from quartz capillaries with laser puller. The surface of nanopipette was polymerized to prepared suitable platform for immobilizing the protein molecules. The protein molecules can be attached covalently to the nanopipettes through amid binds with carboxylic groups of the polymer. The prepared biosensor was applied to study the antibody- antigen interaction.
  9. Keywords:
  10. Nanodiamond ; Ceftriaxone ; Cefepime ; Thioridazine ; Platinum Nanoparticle ; Silver Nanoparticles ; Carbon Nanotubes ; Linear Sweep Voltammetry ; Electrochemical Impedance Spectroscopy

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