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Synthesis and Characterization of Hybrids 3D Graphene/gold Nanostructures for Supercapacitors and Electrochemical Biosensors

Saeidi, Mohsen | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55126 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Simchi, Abdolreza
  7. Abstract:
  8. Energy conversion and storage as well as life sciences are among the areas of our daily life. Interest in carbon nanomaterials for energy storage systems such as supercapacitors has enormously risen due to their attractive electrical conductivity, chemical inertness, and charge storage capacity. Producing these nanomaterials with a simple, scalable, and cost-effective method is the major problem for commercializing them. The reduction of graphitic oxide is a versatile procedure to prepare 3D graphene. Despite many green methods, the dynamics behind ultrafast thermal graphitization have remained elusive. Here, we demonstrate an effort to understand the graphitization mechanism of graphitic oxide under ultrafast thermal reduction induced by electromagnetic radiation and probably via Ar+ cation collisions. The low photon energy (10.5 μeV) locally removes oxygen functionalities and restores the π-conjugated structures. A graphitic structure with low-defect, long-range order, and relatively high electrical conductivity (8.7 S cm−1) is attained at a short photoinduced time (15 s) and relatively low power (1000 W) after a hydrothermal reduction at 160 °C for 2 h. We demonstrate that the prepared spongy graphene structure microwaved for 13 s is an active charge storage material with a specific capacitance of 226.4 F g−1 at 1 A g−1, an ultrahigh rate capability of 85.1% in the range of 0.2−50 A g−1, and a capacitance stability of 120% after 10,000 cycles at 1 A g−1. The ultrafast photoreduction of graphitic oxide for the mass production of graphene sponges paves the way for fabricating functional materials by tailoring oxygenated functional groups for multiple applications. To develop an efficient electrochemical biosensor, three-dimensional graphene/gold nanostructures hybrids were synthesized by chemical and electrochemical reduction of gold ions. The mechanisms of nucleation and growth of various gold nanostructures were studied by a high-resolution transmission electron microscopy (HR-TEM). The results showed that the growth mechanism of gold nanostructures follows by creating twins in gold crystal planes. The prepared electrodes were used to simultaneously quantify ascorbic acid, dopamine, uric acid and folic acid species. The detection limits for these species were 0.05, 0.03, 0.06, and 0.05 µM, respectively, and the sensitivity of the designed biosensors was 0.024, 0.269, 0.202 and 0.233 mA µM-1, respectively. After that, to determine adenosine triphosphate (ATP) concentration in real samples, the designed ATP aptamers were immobilized on the 3D graphene/gold nanoparticles hybrids. The designed aptasensor exhibited a linear range of 0.1 pM-10 µM with a detection limit of 0.033 nM and a sensitivity of 0.48 mM µM-1
  9. Keywords:
  10. Microwave ; Supercapacitor ; Biosensor ; Gold Nanoparticle ; Adenosine Triphosphate (ATP) ; Energy Storage System ; Electrochemical Biosensors

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