Fabrication of a Sensor, Based on TiO2 Nanotubes Modified with Metal Nanoparticles and Carbon and its Application for Detection of Dopamine in Presence of Uric Acid and Ascorbic Acid

Mahshid, Sara | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42084 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Askari, Masoud; Dolati, Abolghasem
  7. Abstract:
  8. The present work describes sensing application of modified TiO2 nanotubes towards detection of dopamine. The TiO2 nanotubes electrode was prepared using anodizing method at different conditions, among which NaF/ NaHSO4 solution and voltage of 15 V was chosen as the optimum condition. In order to improve the performance, surface modification with metal nanoparticles (Pd, Pt and Au) and carbon is required using “pulse electrodeposition” and “decomposition of polyethylene glycol at 600 °C” respectively. Carbon was deposited by decomposition of polyethylene glycol in a tube furnace to improve the conductivity. In this regard two type of electrodes were proposed: Pd-Pt-Au-TiO2 and C-Ni(Pt)-TiO2. The sensing application of the modified electrodes was characterized by cyclic voltammetry and differential pulse voltammetry methods. The C-Ni(Pt)-TiO2 modified electrode displayed high sensitivity towards the oxidation of dopamine and uric acid in a phosphate buffer solution (pH 7.00). In case of C-Ni-TiO2, the electro-oxidation currents of dopamine were linearly related to the concentration over a wide range of 1.0×10−8 M to 5×10−6 M. The limit of detection was determined as 2×10−10 M for dopamine at signal-to-noise ratio of 3. The interference of uric acid was also investigated. Electro-oxidation currents of dopamine in the presence of fix amount of uric acid represented a linear behavior towards successive addition of dopamine in range of 3×10−8 M to 2×10−5 M. On the other hand, Au/Pt/Pd/TiO2 NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. Electro-oxidation peak currents of dopamine were linearly related to accumulated concentration over a wide concentration range of 5.0×10−8 to 3.0×10−5 M with slope of 3.80 µA/ µM. In presence of fixed amount of uric acid, electro-oxidation peak currents of dopamine represented 4.05 µA/ µM sensitivity over concentration range of 1×10−7 to 4.0×10−5 M. However in the same range of dopamine concentration, the sensitivity had a significant loss at Pt/Pd/TiO2 NTs electrode, suggesting the necessity of Au nanoparticles in modified electrode. The Limit of the detection was determined as 3×10−8 M for dopamine at signal-to-noise ratio equal to 3. Furthermore, in a solution containing dopamine, uric acid and ascorbic acid the overlapped oxidation peaks of dopamine and ascorbic acid could be easily separated by using both Pd-Pt-Au-TiO2 and C-Ni(Pt)-TiO2 modified electrodes. However in case of Pd-Pt-Au-TiO2 electrode, without Au nanoparticles the selectivity experienced a significant loss. It was also shown that the modified electrodes possessed a very good reproducibility and long-term stability which suggest their reliability in real conditions
  9. Keywords:
  10. Titanium Oxide ; Platinum Nanoparticle ; Carbon ; Titanium Oxide Nanotube ; Anodizing ; Dopamine

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