Theses & Dissertations

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https://hdl.handle.net/20.500.14170/2003

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Browsing Theses & Dissertations by Subject "Carbon nanotubes"
  • Publication
    Development of multiwalled carbon nanotube integrated field eEffect transistor for highly sensitive HIV-1 tat protein biosensor
    ( 2019)
    Fatin Nabilah Mohd Faudzi
    Human immunodeficiency virus (HIV) has infected almost 35 million people worldwide. Various tests have been developed to detect the presence of HIV during the early stages of the disease in order to reduce the risk of transmission to other humans. The HIV-1 Tat protein is one of the proteins present in HIV that are released abundantly approximately 2 to 4 weeks after infection. Early stage detection of the disease can be achieved by detecting Tat protein in high risk individuals. This mitigates the risk of a HIV pandemic. A back gated field effect transistor (BGFET) has been developed to be a biosensor for the early detection of HIV. Tat protein has been used as the target while split RNA aptamer has been chosen as the detection probe. The binding interactions between split RNA aptamer and HIV-1 Tat protein on a biosensor device was validated using colorimetric assay. The assay successfully demonstrated the interaction occurred between split RNA aptamer and HIV-1 Tat indicated by the changes of gold nanoparticles color from pink to purple. BGFET was made biocompatible by using carbon nanomaterials like multiwalled carbon nanotube (MWCNT) as biomolecules immobilization site. Acid oxidation treatment was conducted to functionalize MWCNT with carboxyl functional groups and subsequently characterized through field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) analysis had profound ~2.91% increment in overall oxygen group and ~1% increment was noticed with a specific carboxyl content owing to C=O and O–C=O bonding. The binding interaction between split RNA aptamer and HIV-1 Tat protein was characterized by Fourier transform infrared (FTIR) binding analysis and electrical quantification of current signal (Ids) over a gate voltage (Vgs). The attainment of sensitivity with aptamer and HIV-1 Tat interaction on the fabricated device was 600 pM. To ensure the genuine interaction of aptamer with HIV-1 Tat, other HIV-1 proteins, Nef and p24 were interacted with aptamer and they displayed the negligible interferences with gate voltage shift of 3.5 mV and 5.7 mV, which shows 4 and 2.5 folds lesser than HIV-1 Tat interaction, respectively.
      9  28
  • Publication
    Reduced graphene oxide-multi walled carbon nanotubes hybrid material as electrode for DNA biosensor
    ( 2017)
    Saeed Salem Saeed Ba Hashwan
    This thesis presents a novel thin film of reduced graphene oxide-multiwalled carbon nanotubes (rGO-MWCNTs) composites as a sensing film electrode for Deoxyribonucleic acid (DNA) immobilization and hybridization detection. This project consisted of three parts, which are the rGO-MWCNTs composite thin film preparation and characterization, the device fabrication processes description, and followed by the DNA immobilization and hybridization. In the first part, the thesis describes the graphene oxide preparation from graphite powder using improved Hummers’ method. Whereas, the multiwalled carbon nanotubes (MWCNTs) was functionalized through nitric acid oxidation process. Chemical reduction process was used to obtain the reduced graphene oxide using hydrazine as reduced agent. The MWCNTs, GO, and rGO-MWCNTs materials were mechanically sprayed on the silicon dioxide (SiO2) surface of the device channel using spray technique. Chitosan solution was mixed with the materials and sprayed on the device surface in order to increase the viscosity of the materials and strengthen their adhesion with the silicon dioxide surface by changing the surface characteristic from hydrophobic to hydrophilic. The morphology of the rGO-MWCNTs composite thin films were observed by field emission scanning electron microscope. The bonding of the rGOMWCNTs were examined using Fourier transform infrared spectroscopy. The phase structure of the materials were confirmed via X-ray powder diffraction. Secondly, the design, fabrication and evaluation of the device were descripted in details. In addition, the device fabrication processes contained of oxidation process for silicon dioxide layer growing, physical vapor deposition process which was used to deposit an aluminum layer on the silicon substrate to form the source and drain, mask designed, printed, and utilized in the pattern transfer process, and photolithography process which was carried out to create the channel of the device. The operation of the electrode is based on the surface charge adsorption of the film material interface. Finally, in the DNA immobilization and hybridization section where the novelty of the research introduced, the biosensor demonstrated high sensitivity to the complementary DNA target with a linear range from 500 pM to 100 pM. Furthermore, the biosensor demonstrated good selectivity, reproducibility, and long-term stability for DNA detection. The device has shown sufficient capability to distinguish between targets complementary DNA and different DNA sequences, such as non-complementary and single-mismatched DNA. The hybridization process of the non-complementary DNA has the smallest response (39 μA) due to the double standard DNA was not effectively formed. Whereas, the singlemismatched DNA has shown less response (55 μA) comparing with the complementary DNA (65 μA) due to the single mismatched base. The device accuracy was investigated and found to be 11.28 %. Since, the biosensor responded very well and demonstrated excellent detection capabilities, it is highly recommended to be used in detecting specific biomarkers and other targeted proteins.
      2  6
  • Publication
    The optimization of multi-walled carbon nanotubes surface modification via nitric acid oxidation for DNA immobilization
    ( 2014)
    Shahidah Arina Shamsuddin
    This thesis discussed on the optimization of MWCNTs surface modification via nitric acid oxidation for DNA immobilization. After acid oxidation treatment, the impurities in multi-walled carbon nanotube (MWCNTs) such as carbonaceous and metal catalyst particles are successfully reduced as has been analyzed by energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD) and thermogravimetric analyzer (TGA). Acid oxidation will caused to the opening of MWCNTs tips and structural defects formed on the MWCNTs surface due to the acid attack. Oxygen containing functional groups, mainly, carboxylic group (COOH) has been introduced on the MWCNTs opened tips and at the defect sites which are useful to interact with other molecules, in this case, aminated-ssDNA probe. The results from fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy have shown that the COOH amount is depended on the MWCNTs structure defects. Meanwhile, cyclic voltammetry (CV) results have indicated that the immobilization current is directly proportional to the COOH amount. However, structure defect will affect to the immobilization current when ID/IG ratio is increased. The acid oxidation parameter should be optimized, thus the amount of COOH can be increased with the minimal structure defect. Therefore, the main goal to have a maximum immobilization current can be achieved. L9 Taguchi orthogonal array has been used to optimize the acid oxidation parameters. From the result, 5 M of nitric acid concentration, 120 °C of treatment temperature and 6 hours of treatment time are selected as the most optimum combination of acid oxidation parameters. The percentage influence of each main factor is also calculated to be 46% xvi 35% and 18% for nitric acid concentration, treatment time and treatment temperature, respectively. The improvement is happened to be 11.6% of increment in the immobilization current.
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