Solution processable carbon nanotube devices : from optoelectronics to biosensing

• Main Author: Xu, Xinzhao
• Format: Dissertation
• Language: English
• Published: Queen Mary University of London 2021

Single Walled Carbon nanotubes (SWCNTs) have attracted substantial attention due to their unique properties, such as one-dimensional architecture, excellent electrical properties, chemical stability for different modification and the easy integration into electronic circuits, which allows for the potential applications in field effect transistors, biosensors and optoelectronics. Despite these considerable achievements, it is still challenging to fabricate SWCNTs devices with low-cost processability and multipurpose capability. Herein, we propose facile, low cost, and solution processable strategies for the fabrication of SWCNT devices, which broaden the application of SWCNTs in different fields. In this work, DNA-wrapped SWCNTs were functionalised with specific and distinct aptamer sequences which were used as selective receptors to bio-analytes. These distinct SWCNT-aptamer hybrids were immobilised onto pre-patterned electrodes via dielectrophoresis (DEP) on the same chip into device configurations, forming multiplexed sensing devices. Multiplexed detection of three different analytes was successfully performed and real time detection was achieved in serum. Moreover, we reported the fabrication of protein-based biosensors, where the -lactamase binding proteins (BLIP2) were engineered with phenylazide handles at defined sites, which allowed us to control the orientations of BLIP attached to SWCNTs. Therefore, we can control the local electrostatic surface presented within the Debye length when TEM -lactamase was binding to BLIP2, thus modulating the conductance gating effect. The devices gave distinct responses depending on TEM presenting either negative or positive local charge patches. This indicates that local electrostatic properties act as the key driving force for electrostatic gating. iv Due to their nanoscale one dimensional (1D) architecture, we used SWCNTs as vector templates to fabricate devices with multiplexed metal wires. Since metal precursors were encapsulated inside the SWCNT templates, we were able to precisely control their size, shape and orientation via DEP. Multiscale characterization of the different fabrication steps revealed details of the structure and charge transfer between the material encapsulated and the carbon nanotube. Electrical measurements further demonstrated the successful fabrication of metal nanowire devices. Finally, we performed the separation of single chirality SWCNTs. By immobilised the separated (6,5), (7,5) and metallic tubes on the same chip, we demonstrated the fabrication of multiplexed single chirality SWCNT devices. Additionally, mixed chirality and single chirality SWCNTs were used to synthesize CdS-SWCNT hybrids for photodetection. The results showed that single chirality devices were more sensitive to green laser. Overall, we immobilised SWCNTs to fabricate nanoscale devices via a solution processable method. This makes the fabrication of devices processing multipurpose capability and easy processing possible, which is of importance for broadening the application of SWCNTs. We also demonstrated the applications of SWCNTs in electronics and biosensors. I hope our work can inspire others to develop SWCNT devices from theoretical research to practical applications.