Loading...

Synthesis of Nanocomposites based on Carbon nanotubes and Graphene/Ionic Liquid for Construction of Biosensors

Tasviri, Mahboubeh | 2011

959 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42389 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Gholami, Mohammad Reza; Ghourchian, Hedayatollah
  7. Abstract:
  8. In this project during 2 sections the synthesis and application of nanomaterials based on carbon nanotubes and graphene oxide for immobilization of Glucose oxide and Horseradish peroxidase enzymes for construction of effective biosensors were investigated. In section 1, we introduce a new nanomaterial in which TiO2-coated carbon nanotubes were functionalized with amine groups (NH2-TiO2-CNTs). This nanomaterial was fixed on a glassy carbon electrode surface and then its ability for direct electron transfer of Glucose oxidase (GOx) and Horseradish peroxidase (HRP) on the modified electrode was investigated. The direct electrochemistry of immobilized GOx and its electron transfer parameters at the modified glassy carbon electrode were reported. The apparent heterogeneous electron transfer rate constant (ks) of GOx was estimated to be 3.5 s−1, which is higher than those reported previously. Amperometric detection of glucose resulted in a rapid (3 s) and stable response in the linear concentration range from 1.8 to 266 μM. The apparent Michaelis-Menten constant was measured to be 8.59 mM, indicating that the immobilized GOx on NH2-TiO2-CNT matrix retained its native activity. The anti-interference ability and long-term stability of the biosensor were also assessed. Also, HRP was successfully immobilized on NH2-TiO2-CNTs by a convenient and efficient method. The result showed that the NH2-TiO2-CNTs greatly enhance the electron transfer between HRP and the modified electrode. Owing to the redox reaction of electroactive center of HRP, the HRP/NH2-TiO2-CNTs modified electrode exhibited a pair of quasi-reversible peak with the peak-to-peak separation (ΔEp) of 70.6 mV and the formal potential (E0') of -367.65 mV in phosphate buffer solution. The charge transfer coefficient (α) and the apparent charge transfer rate constant (ks) were obtained to be 0.34 and 2.08 s-1, respectively. The prepared biosensor responded to H2O2 with a linear range, detection limit, sensitivity and response time of 1.0×10-9 to 1.0×10-7 M, 0.786 nM, 28.4 μA nM-1 and 3 s, respectively. In section 2, the new GOx biosensor based on graphene oxide (GO) and room temperature ionic liquid, IL, (1-ethyl-3-methyl immidazolium ethyl sulfate) was fabricated using layer by layer method. The modified electrode exhibited a quasi-reversible cyclic voltammogram with a formal potential of -463 mV with the peak-to-peak potential separation (ΔEp) of 82 mV with scan rate of 100 mV s-1. The apparent charge transfer rate constant (ks) and transfer coefficient (α) for electron transfer between the electrode surface and GOx were calculated as 1.36 s-1 and 0.35, respectively. IL-GOx-GO/GC electrode shows excellent electrocatalytic activity towards glucose determination in the range of 2.5-45 nM with detection limit of 0.175 nM (S/N = 3). The modified electrode was stable for two months with no observable change (~5%) in the cyclic voltammograms
  9. Keywords:
  10. Carbon Nanotubes ; Glucosoxidase Enzyme ; Titanium NanoParticles ; Titanium Oxide ; Biosensor ; Ionic Liquids ; Horseradish Peroxidase (HPR) ; Graphene Oxide

 Digital Object List

 Bookmark

No TOC