Theses & Dissertations

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

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Browsing Theses & Dissertations by Subject "Biosensor"
  • Publication
    A computational analysis of interaction between inorganic semiconductor nanowire and molecular partial charge for DNA sensor application
    ( 2015)
    Abdulmohaimen W Fagri
    This research aimed to investigate the effects of partial charge due to DNA hybridization on the conductance of the silicon nanowire through finite element calculations. A biosensor was designed with the silicon nanowire of 15 nm radius at the core and surrounded by a silicon dioxide (2 SiO) layer of 2 nm thickness. The oxide layer was surrounded by a 5 nm thick functional bio-interface layer incorporating probe ssDNA and this whole system was immersed in an electrolyte of 80 nm radius. For the purpose of modeling and simulation, each of this layers was treated as a continuum medium characterized by the corresponding dielectric constant. In order to determine the effects of hybridization on nanowire conductance, the distribution of the electrostatic potential in the nanowire and other layers were first computed using Poisson equation with Boltzmann statistics without adding target DNA in the electrolyte layer. The conductance of the nanowire in this condition was computed by integrating the effect of the potential charge carriers within the nanowire and partial charge due to probe ssDNA. Then, the potential distribution was again calculated with the target DNA in the electrolyte and the conductance of the nanowire was re-calculated. Partial charge due to hybridization between probe and target DNAs was first computed using molecular dynamics simulation and integrated into the finite element calculation. The Finite element calculations showed that the nanowire conductance depended nonlinearly on the external charge (partial charge) of the bio-interface due to the hybridization of the target DNA with probe DNA in the functional layer.
      1  52
  • Publication
    Design and fabrication of SWNT-FET based biosensor
    ( 2012)
    Mohd Syamsul Nasyriq Samsol Baharin
    Nanotubes have generated intense research activities from scientists of various disciplines because they represent a new class of materials for the study of one-dimensional physics. Single-walled carbon nanotubes (SWNTs) have many other magnificent properties and it has impressive properties in three aspects, mechanical, electrical, and biological due to ability of single-walled carbon nanotubes (SWNTs) to exhibit self-assemble monolayer (SAM0. The main objective of this project is to design and fabricate carbon nanotube based biosendor for future application medical diagnostics. The electrical transport of semiconducting single-walled carbon nanotubes with the diameter of ~1.5 nm and length of 2 μm to 6 μm for its applications as biomolecules detection was investigated. Single-walled carbon nanotubes field effect transistors (SWNT-FET) were fabricated in house using three masks designed. Initially backgated field effect transistor (FET) was formed and followed with the growth of oxide as insulation layer. Multilayer metal of platinum,Pt and gold,Au were grown on top of oxide layer and finalized with the integration of single-walled carbon nanotubes (SWNTs). The oxide thickness achieved is ~18nm and multilayer metal of platinum,Pt and gold,Au thickness is ~10nm and ~90nm respectively. The integration of single-walled carbon nanotubes (SWNTs) with field effect transistor (FET) was performed using AC dielectrophoresis nanomanipulation technique resulting promising results of integration proven via Scanning Electron Microscope (SEM). Fabricated device resulting conductance of G ~ 0.03 x 4e2/h and hole mobility of μp ~ 3060 cm2/V.s in saturation mode. This device also shows resemblances with conventional p-type metal-oxide-semiconductor FETs (MOSFETs) through IDS-VDS curve and appears to be gate voltage dependence through conductance-gate voltage curve. Thus, these results prove that fabricated device functioned as p-type metal-oxide-semiconductor FETs (MOSFETs) and can be used for the application of biomolecules detection such as protein by monitoring the device changes of IDS-VDS characteristics.
      2  36
  • Publication
    Gold nanostructures in mediating high-performance medical diagnosis of human blood disease biomarkers
    (Universiti Malaysia Perlis (UniMAP), 2020)
    Iswary Letchumanan
    The current research was carried out using three (3) different human blood disease biomarkers which were C-reactive protein (CRP), blood clotting factor IX (FIX) and squamous cell carcinoma antigen (SCC antigen). Two different types of dual probing system electrode were utilized in this research. A nano gapped electrode with the gap of ~100 nm was designed and modified to capture the target, CRP. Meanwhile, factor IX and SCC antigens were diagnosed by using an interdigitated electrode (IDE), which had finger like structure with the zinc oxide surface. In order to increase the amount of antigen to be captured a gold nanorod (GNR) of a 119 nm in length and 25 nm in width was integrated in CRP detection system. In addition, gold nano-urchins (GNUs) with 60 nm in diameter was integrated into a streptavidin-biotinylated aptamer strategy in Factor IX diagnosis technique. Whereby, dispersed and agglomerated state of gold nanoparticles with 30 nm was used in SCC antigen detection scheme. The physical characterization for the sensing surface and gold nanostructures was properly carried out atomic force microscopy, scanning electron microscopy, 3D nano-profilometry, high-power microscopy and UV–Vis spectroscopy. A comparative analysis in the existence and non-existence of gold nanostructures utilization was performed using electrical characterization. The amperometric measurement by a linear sweep voltage of 0 to 2 V at 0.01 V step voltage was implemented to study the sensitivity and specificity of the blood biomarker interaction. Current research using three different biomarkers which responsible for three different blood disease reveals a lower limit of detection as compared to real concentration of specific biomarkers in human serum. The obtained detection limit as low as pico- to femtomolar range was due to the conjugation of gold nanostructures with antibody (Probe) and the strategy used like streptavidin-biotinylated aptamer for Factor IX detection. Hence, the highlighted novelty of the research is the utilization of different gold nanostructures and also the strategy applied to enhance the detection system. Hence, gold mediated high-performance sensing able to lower the limit of detection down to pico- to femto-molar ranges and hold an outstanding performance in biosensing application.
      5  14
  • Publication
    Synthesis and optimization of Anodic Aluminium Oxide thin film electrode for DNA sensing
    (Universiti Malaysia Perlis (UniMAP), 2021)
    Shahidah Arina Shamsuddin
    Recent years, anodic aluminum oxide (AAO) has been extensively explored as an inexpensive, portable and sensitive DNA biosensing device. Apart from their ability to self-grow into well-ordered nanoporous with high porosity and huge surface area, AAO has one special feature wherein their nanopores‘ dimension are capable to be altered and engineered by controlling the main anodizing parameters namely voltage, temperature, time and electrolyte concentration. Since sensitivity and limit of detection of AAO-DNA biosensor depends on the nanopores‘ dimension itself, therefore, many researchers have tried to understand the effect of each anodizing parameters to the nanopores‘ dimension while tried to optimize and improve the sensitivity of AAO in detecting DNA. However, those studies were only focused on the trend of single variable parameter at one time by one-factor-at-a-time method (OFAT), rather than investigating all the interactions between the anodizing parameters simultaneously. Hence, they only reported the improvement made to the sensitivity of their AAO-DNA biosensor at the particular parameter range that they have tested without providing the best of optimum combination levels of all anodizing parameters while the most critical and influential anodizing parameter is still remained unknown. As a contribution to solve these problems, Taguchi method has been proposed in this research as an optimization tool to study the existing interaction between the parameters while at the same time providing the best combination of all parameters levels to improve the AAO-DNA biosensor sensitivity at its optimum performance. Meantime, ANOVA analysis has been proposed to obtain the most influential anodizing parameter to the sensitivity of AAO-DNA biosensor. Prior to optimization, correlation study between the pores‘ dimension and resistance charge transfer (Rct) that affects the sensitivity of AAO-DNA biosensor has been conducted. For this research, AAO thin film-DNA biosensor electrode was synthesized using a single step anodization method in oxalic acid. FESEM was used to observe the AAO surface, while EIS was utilised to study the electrochemical system for DNA hybridization detection. From the first finding, sensitivity of AAO-DNA biosensor was found to be influenced by the ratio of AAO thickness to the pore size. Rct remained under 100 kΩ as long as the ratio of AAO thickness to the pore size was maintained in the range between 1:11 to 1:16. Exceeding the ratio of more than 1:25 will result to the sudden increased in Rct and hence affecting the sensitivity to be reduced. From the second finding, optimization through Taguchi method is the main novelty of this research. The optimum combinations of anodizing parameters were found at 40 V, 17 °C, 0.3 M of oxalic acid at 1 hour. A repetition in experiment was conducted to confirm the efficiency of Taguchi where the sensitivity of the optimized AAO-DNA biosensor electrode was successfully improved to 62.57 % at 0.278 kΩ/M (LOD at 6.497 x 10-15 M) compared to the nominal. From the third finding through ANOVA analysis, the sequences of the most influential anodizing parameter to the AAO-DNA biosensor sensitivity are following the order: anodizing voltage (34.13%) > anodizing time (29.85%) > temperature (20.27%) > electrolyte concentration (15.74%). At the end of this research, optimization of the synthesis of AAO thin film electrode by Taguchi method for DNA sensing was successfully achieved. Since this research had used nonspecific type of DNA target analytes for prototyping development purposed, therefore, it is targeted that this optimized and sensitivity improved AAO thin film electrode will have greater chance to be used widely in the future for detecting various types of DNA, such as dengue, E-coli, or salmonella. Besides, it is of great hope that the outcome from this research may help other researchers to synthesize AAO thin film at its optimum anodizing condition as to improve the sensitivity of the AAO-DNA biosensor
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