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Fabrication of 3D Graphene/Gold Porous Electrode for Biosensing Applications

Rahmati, Reza | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51761 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Simchi, AbdolReza; Tamjid Shabestari, Elnaz
  7. Abstract:
  8. Today, the use of carbon nanostructures hybridized with noble metals has attracted considerable attention for the fabrication of bio-electrochemical sensors. Since the specific surface area has an immense effect on the sensing response, three-dimensional structures of graphene have a great capability to utilize in these sensors. In this research, three-dimensional graphene was provided on the porous nickel foam by chemical vapor deposition technique. By evaluation of raman spectroscopy, the time period of 20 minutes for solving of the carbon atoms into the nickel foam was selected as the main parameter of optimized conditions for the synthesis of graphene. Afterward, production of few-layer graphene was proved by X-ray diffraction method. Nickel substrate was removed and free-standing graphene foam was transferred onto the glassy carbon electrode. The step-by-step development of morphology and chemical composition of glassy carbon/three-dimensional graphene were studied utilizing scanning electron microscopy and energy-dispersive X-ray spectroscopy. After electrochemical deposition of gold nanoparticles on the graphene surface, X-ray diffraction confirmed the successful deposition of this phase. Additionally, the peaks in raman spectra of graphene foam were intensified due to the surface plasmon resonance phenomenon. The effect of the concentration of the gold acidic solution in the range between 0.1 and 10 mM on the weight percentage, size, and distribution of gold nanoparticles in the three-dimensional hybrid structure was inquired by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Subsequent to finding the optimized conditions and voltammetry method, as well as the electrode with maximum response to electro-oxidation of melatonin, resistance behavior of the engineered sensor was interpreted by electrochemical impedance spectroscopy. The charge transfer resistance of glassy carbon/three-dimensional graphene/gold nanoparticles hybride with almost 18-fold electro-active surface area and more electro-catalytic activity was decreased 87% in comparison with the unmodified electrode. The calibration curve was plotted employing differential pulse voltammetry technique. A wide linear range of 0.05-50 μM, a detection limit of 0.0082 μM (3σ/m), and a high sensitivity of 16.219 μAμM-1cm-2 were achieved. Additionally, the effects of different pH values of the supporting electrolyte as a chemical parameter and potential scan rate as an electrochemical parameter on the sensing response of the electrode were investigated. The stability with saving more than 95% and 90% of the peak current intensity after 7 and 14 days, the favorable repeatability with a relative standard deviation of 0.14% and also the proper selectivity of the designed electrode considering the probable interference of uric acid and ascorbic acid were proved. The potential application of the electrode for detection of melatonin in real pharmaceutical samples was shown. The proposed electrode hold great promise for the development of biosensors and other electrochemical devices
  9. Keywords:
  10. Biosensor ; Three Dimentional Graphene Foam ; Gold Nanoparticle ; Melatonin Hormone ; Electrochemical Investigation ; Porous Electrode

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