Integration of substrate-gate couple p-type anatase TiO₂ for field-effect transistor based biosensors
The term “biosensor” is a short form for “biological sensor”. A biosensor is generally defined as an analytical device, which converts the biochemical responses into quantifiable electronic signal. The device is made up of a transducer and biological receptor. The transducer surface needs to be fun...
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| Format: | Thesis |
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| Language: | English |
| Subjects: | |
| Online Access: | http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/76655/1/Page%201-24.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/76655/2/Full%20text.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/76655/3/Declaration%20Form.pdf |
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| Summary: | The term “biosensor” is a short form for “biological sensor”. A biosensor is generally defined as an analytical device, which converts the biochemical responses into quantifiable electronic signal. The device is made up of a transducer and biological
receptor. The transducer surface needs to be functionalized with biological receptors such as an antibody, an enzyme or a nucleic acid. The biological receptor is employed to identify the specific target (i.e. DNA or antigen) molecule and the transducer to
transform the specific interaction of the biomolecule into electronic signal. This method allows high sensitivity, rapid response and label-free detection. In this work, the integration of substrate-gate coupling of field-effect transistor (FET) based sensor with
p-type anatase TiO₂ as a transducer material for detection of cardiac troponin I biomarker is presented. The work is initiated with fabrication of substrate-gated FET based biosensor on p-type silicon-on-insulator (SOI) wafer. Photolithography process
with three different masks are used; 1) to create 10 μm channel in between the source and drain area, 2) to expose substrate-gate electrode through the top-silicon and buried oxide (SiO₂) layer, and 3) Al metal contact deposition for source, drain and substrate gate electrodes. Next, TiO₂ that acts as a transducer material is deposited on top of the channel by using sol-gel technique, creating a thin film TiO₂ on the surface. Several characterization methods have been used to determine the TiO₂ properties such as surface morphology (AFM, SEM), material crystallinity (XRD), surface functionalization (FTIR, XPS), and electrical characteristics (SPA). The deposited TiO₂ thin film possess p-type anatase structure due to titanium vacant defect, with average grain size of 65 nm. The fabricated device with TiO₂ thin film (before functionalization and detection of biomolecule), shows that there is electrical flow with the presence of TiO₂ connecting between source and drain, and it can be modulated with substrate-gate bias. Subsequently, the TiO₂ surface is functionalized with APTES and Glutaraldehyde prior to be subjected into antibody-antigen interaction, characterized by using XPS and FTIR. It shows, the changes or the presence of peaks at each surface functionalization proved that the chemical bonding have occurred. To demonstrate the functionality and
performance of for biomolecule detection, the device is demonstrated to detection of cardiac troponin biomarker (cTnI) with concentration from 1ng/ml until 10 μg/ml. cTnI is a gold standard for diagnosis of cardiovascular disease. With the presence of
substrate-gate biasing (Vbg = - 3 V), the device demonstrated significant amplification signal with LOD of 0.238 ng/ml can be achieved. This bring to a confirmation that the p-type anatase TiO2 offers excellent interaction with cTnI biomolecule. Coupled with substrate-gated FET, enhance sensitivity of bio-sensing can be achieved due modulation of electrical conductivity along the channel. |
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