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Synthesis of Aligned Carbon Nanotubes and Their Modification with Noble Metallic Nanoparticles as Organic Analytes Biosensors

Fayazfar, Haniyeh | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45263 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah; Dolati, Abolghasem
  7. Abstract:
  8. An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition (CVD). By varying CVD parameters, aligned CNTs (A-MWCNTs) with diameter between 20-100 nm and length of some micrometers with bamboo-like shapes were produced. Free-standing MWCNTs arrays were functionalized and purified through electrochemical oxidation. Then in order to improve the performance, facile template-free electrochemical routes were developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, sheet and rod on A-CNTs at room temperature. The results showed that the nanoparticles with the range of 10-100 nm in diameter, nanorods with the diameter of 50-100 nm and the length of 100 to 1 μm, nanopin dendrites with the lengths of the main dendrite trunks between 4–7 μm, and the branch trunk range from 300 nm to 4 μm were produced. These modified electrodes were used for the sensitive determination of the drugs, simvastatin (SV) and cefazolin (CFZ) and also monitoring the sequence-specific DNA hybridization events related to TP53 gene by linear sweep and cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the A-MWCNT/ dihexadecyl hydrogen phosphate/Ta modified electrode to detect SV showed a wide linear range from 0.01 to 5 μM with a detection limit of 0.01 nM. The sensitivity of the electrode was 0.001 A cm-2 μM-1. The highly sensitive A-MWCNT/Au nanoparticles/Ta modified electrode for determination of CFZ showed a wide linear range from 50 pM to 50 μM with a sufficiently low detection limit of 1pM and sensitivity of 458.2 μAcm-2μM-1. Also, direct determination of CFZ and SV in pharmaceutical dosage forms as real pharmaceutical samples using the standard addition method, indicated the successful applicability, adequate precision and accuracy of the proposed strategy for the clinical applications. It was also shown that the modified electrodes possessed a very good reproducibility, long-term stability and good selectivity which suggest their reliability in real conditions. Finally, EIS was used to monitor the sequence-specific DNA hybridization events related to TP53 gene, one of the most popular genes in cancer research, by using the A-MWCNT/AuNPs/Ta modified electrodes. The change of charge transfer resistance was found to have a linear relationship with respect to the logarithm of the complementary oligonucleotides sequence concentrations in the wide range of 1.0×10−7–1.0×10-15 M, with a detection limit as low as 1.0×10−17 M. The significant improvement in sensitivity, great stability and reusability of the proposed sensor illustrates that Au nanoparticle with the A-MWCNT arrays represents a promising platform for achieving ultrasensitive biosensor for fast mutation screening related to most human cancer types
  9. Keywords:
  10. Carbon Nanotubes ; Biosensor ; Electrodeposition ; Electrochemical Oxidation ; Gold Nanostructure

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