Napatsakorn Kamkrua creator Bora, Tanujjal Chairperson Noppadon Nuntawong Co-Chairperson Ricco, Raffaele Examination committee Loc Thai Nguyen Examination committee Royal Thai Government Scholarships Scholarship Donor text th Pathum Thani Asian Institute of Technology 2022 continuing eng 71 p. : ill. A common herbicide such as paraquat has been countlessly applied in agriculture, and its residues are left in water and soil. Paraquat toxicity highly damages the body, which can be lethal in a later stage. Thus, paraquat detection is important and several techniques have been developed in recent years. Raman spectroscopy facilitates herbicide detection in rapid and non-destructive ways. Furthermore, surface-enhanced Raman spectroscopy (SERS) and bioreceptors are commonly utilized to enhance the sensitivity and selectivity of molecular structure detection, respectively. This study focuses on optimizing SERS-active substrates to improve the selectivity and rapidity of paraquat detection. This work also aimed to develop the combinations of SERS and biosensors for paraquat detection by functionalizing metallic nanostructures with an aptamer that is specific to the paraquat molecule via Raman spectroscopy. Soil and water samples were used for the evaluation of optimized SERS-active substrates. The sensitivity, selectivity, and limit of detection were investigated by Raman measurement. This study optimized the ONSPEC-Prime SERS chip (AgNRs) for paraquat detection in water and soil samples. Without extraction protocol, the chip provided a sensitivity of 638.96 a.u./æM and a detection limit (LOD) of 0.1 æM for the water sample. However, in the soil samples, paraquat extraction protocol with alumina absorbent is required. Furthermore, the aptamer-based SERS chip was successfully fabricated with a sensitivity of 609.15 a.u./æM and LOD of 0.35 æM using 0.1 æM of aptamer immobilized on the ONSPEC-Lite SERS chip (AuNPs). A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Nanotechnology Thesis (M. Eng.) - Asian Institute of Technology, 2022 Raman spectroscopy Biosensors Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B18184 http://203.159.5.9/ait-thesis/detail.php?q=B18184 230203 20260818090121.0