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Carbon nanotube thin film transistor platforms for small molecule aptasensors

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dc.rights.license Author Retains All Rights en_NZ
dc.contributor.advisor Plank, Natalie
dc.contributor.advisor Ruck, Ben
dc.contributor.author Zheng, Hanyue
dc.date.accessioned 2016-02-17T23:33:58Z
dc.date.accessioned 2022-11-03T18:44:54Z
dc.date.available 2016-02-17T23:33:58Z
dc.date.available 2022-11-03T18:44:54Z
dc.date.copyright 2016
dc.date.issued 2016
dc.identifier.uri https://ir.wgtn.ac.nz/handle/123456789/29864
dc.description.abstract Network films of carbon nanotubes have shown a great deal of promise as the active channel in field effect transistors (CNT FETs) for utilisation as aptasensors. The detection of small biological molecules or ions using biosensors remains a challenge, partly due to issues of selectivity. This thesis presented CNT FET aptasensors for selectively and quantitatively detecting 17 β-estradiol (estrogen, E2) and potassium ions (K⁺) in real time. By using this device architecture, the conformational change of the aptamer upon the exposure to analytes induced electrostatic gating of electronic conduction in CNT FET aptasensors clearly demonstrate their ability as selective biosensors. Initially device fabrication and electrical characterisation of CNT FETs are presented in this thesis. CNT network films have been reproducibly fabricated on both rigid SiO₂/Si and flexible polyimide substrates via a surfactant free solution deposition route. Standard microelectronic processing is used to fabricate the devices in controlled locations. This thesis presents the dependency of electrical performances on CNT tube densities which are controlled by the CNT suspension concentrations. It is found that the tube density must reach the percolation threshold for an optimised device. The CNT FETs display reliable p-type semiconducting properties with low operating voltages (< 1 V) in liquid environments. The flexible CNT FETs on polyimide show good electrical performance with 5000 on/off current ratios and 4 cm²/V·s hole mobilities, making the platform a viable candidate for aptasensors. To fabricate an aptasensor, noncovalent functionalisation of the CNT surface with 1-pyrenebutanoic acid, succinimidyl ester (PBASE) is carried out before linking amine functionalised aptamers. It is shown that the selective tethering is required to fabricate a reliable sensor, and that non selective aptamer adsorption on the CNT surfaces blocks any analyte detection. The real time current response for the 35-mer E2 aptamer functionalised CNT FET shows a clear increase in current over the range of 50 nM to 1.6 μM of E2, using 35-mer random sequenced DNA as a control. The E2 response using the 75-mer aptamer functionalised CNT FETs where the aptamer/E2 binding occurs beyond the Debye length, shows no obvious evidence of sensing, confirming that the sensing mechanism is due to conformational changes in the aptamer structure bringing charges closer to the CNT surface. The successful realisation of CNT FET aptasensors on flexible substrates (polyimide) for detection of the K⁺ ion is also presented. Electrostatic gating is established via the specificity and the sign of the current response, and by observing its suppression when higher ionic strength decreases the Debye length at the CNT/water interface. A detection limit of 10 pM has been achieved in resistive sensing mode, and 100 pM in real time FET current response mode. Overall the research shows successful application on a CNT FET device platform for detecting E2 and K⁺ based on aptamer functionalised CNT FETs. The reliable electrical performance of flexible CNT FETs fabricated by a facile solution deposition route is an advantage of this sensing platform. The effective device architecture presented, along with the identification of clear real time response signatures, which inform the development of flexible electronic biosensors using aptamer as receptors. At the end of thesis, the plans for future work are presented. en_NZ
dc.format pdf en_NZ
dc.language en_NZ
dc.language.iso en_NZ
dc.publisher Te Herenga Waka—Victoria University of Wellington en_NZ
dc.rights Access is restricted to staff and students only. For information please contact the Library. en_NZ
dc.subject Carbon nanotube transistor en_NZ
dc.subject Aptamer en_NZ
dc.subject Biosensor en_NZ
dc.title Carbon nanotube thin film transistor platforms for small molecule aptasensors en_NZ
dc.type Text en_NZ
dc.date.updated 2016-02-14T21:06:54Z
vuwschema.contributor.unit School of Chemical and Physical Sciences en_NZ
vuwschema.subject.anzsrcfor 029999 Physical Sciences not elsewhere classified en_NZ
vuwschema.subject.anzsrcfor 100705 Nanoelectronics en_NZ
vuwschema.subject.anzsrcfor 100708 Nanomaterials en_NZ
vuwschema.subject.anzsrctoa 1 PURE BASIC RESEARCH en_NZ
vuwschema.type.vuw Awarded Doctoral Thesis en_NZ
thesis.degree.discipline Physics en_NZ
thesis.degree.grantor Te Herenga Waka—Victoria University of Wellington en_NZ
thesis.degree.level Doctoral en_NZ
thesis.degree.name Doctor of Philosophy en_NZ

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