Surface Modification of Polymeric Substrates and Its Application in Textile Graphene-Based Smart Gas Sensors

Rapid urbanisation and industrialisation demand flexible and wearable air-quality monitoring technologies. This thesis reports the development of textile-based chemiresistive gas sensors using hand-embroidered silver interdigitated electrodes on nylon substrates and rGO/metal-oxide sensing inks for room-temperature detection of NO₂, NH₃, and CH₂O. Unlike conventional MOx gas sensors that rely on rigid substrates and elevated operating temperatures, the proposed approach enables low-temperature operation, mechanical flexibility, and textile compatibility. Oxygen plasma treatment was systematically investigated as a surface modification strategy for polymer substrates. On PTFE, plasma pressure–dependent changes in wettability, morphology, and surface chemistry were analysed using contact angle measurements, SEM, and FTIR, revealing ageing behaviour governed by competing morphological roughening and chemical functionalisation. Three ageing regimes were identified: morphology-dominated hydrophilicity, chemistry-controlled hydrophobic recovery, and eventual surface stabilisation. On nylon textiles, plasma treatment induced a transition from hydrophobic to superhydrophilic behaviour, with partial hydrophobic recovery dependent on exposure time. Enhanced rGO/CuO adhesion on plasma-treated nylon was confirmed by SEM/EDS mapping. Graphene-based nanomaterials were synthesised for sensing applications, including graphene oxide, graphene quantum dots, and reduced graphene oxide hybridised with metal oxides. While GQDs exhibited size-dependent quantum behaviour, limited yield restricted their applicability. rGO/CuO and rGO/CuO/SnO₂ nanocomposites was successfully synthesized for gas sensing. Textile gas sensors fabricated using rGO/CuO exhibited reliable responses to NO₂, NH₃, and CH₂O at low-ppm concentrations, with a minimum detectable NO₂ level of 6 ppm. Further enhancement of NO₂ sensitivity was achieved using dual metal oxide functionalisation (rGO/CuCoOₓ), highlighting the critical role of sensing material composition in device performance. Overall, this thesis demonstrates a feasibility of the new approach fo flexible, and textile based gas sensor development that avoids the need for advanced fabrication facilities. By integrating surface-engineered textiles with graphene-based hybrid sensing materials, the work presents a viable pathway toward distributed and indicative gas monitoring in industrial and resource-limited environments, with potential for future adaptation to indoor air-quality monitoring following further sensitivity optimisation.