Investigation of electrical and colorimetric sensing properties of polymer-nanomaterial composites
Date of Issue2017-05-31
School of Materials Science and Engineering
Over the past few decades several biosensor and chemosensor technologies have been investigated for environmental monitoring and diagnostic applications. Among all the developed sensing platforms, optical (colorimetric) and electrical sensors are the most commonly adopted analytical platforms for biosensor/chemosensor fabrication. This thesis is focusing on investigation of colorimetric and electrical properties of polymer-nanomaterial composite. This thesis used conjugated polymers (polyelectrolyte) such as polythiophene (PT) and polydiacetylene (PDA) as optical transducer and carbon nanotubes (CNT) as electrical transducer. The first half part of thesis is to improve the colorimetric response and specificity of polymeric material. The typical way to achieve this goal is to modify the side group of polymer. A simple and alternative way was proposed in this thesis: tuning the composition between polymeric materials. This hypothesis was firstly tested in Al3+ assay using two water soluble PT monomers. The proposed methodology showed selective and sensitive detection for Al3+ in analytically relevant concentration ranges compared to the homopolymers. Instead of tuning the composition between two monomers, incorporating other polymeric materials with PDA could be an alternative strategy for achieving higher sensitivity and selectivity. Volatile organic compounds (VOCs) are applied for validation of the hypothesis. The result shows significantly improved sensitivity based on the strategy of tuning the composition between PDA and matrix polymer. The second half of this thesis is to develop multi-parametric sensing platform. PTs with five different combinations/compositions of pendant groups are incorporated with CNT and evaluated as chemiresistors for analysis of VOCs. Another multi-parametric sensing platform based on PDA is fabricated via centrifuge technique, CNT/PDA/matrix polymer incorporated membranes showed higher responses than CNT incorporated membranes. The proposed sensing platform demonstrated better limit of detection (LOD) (approaching to 10 ppm) at low concentrations of VOC vapor.