Fiber optic sensors based on laser-induced graphene for potential application in aquaculture

• Autor(a) principal: Gomes, Hugo Coutinho
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/39497
• topic: Fiber optic sensors; Polyimide; Fabry-Perrot cavities; Laser-induced graphene (LIG); Cortisol

Cortisol and ammonia are key indicators for the efficient and healthy development of aquaculture cultures. With this in mind, this work proposes the application of a laser-induced graphene (LIG) based sensor for the potential quantification and monitoring of cortisol and ammonia in aquaculture waters. The developed sensors were created from the Fabry-Pérot cavity principle. The cavities were filled with polyimide and in some cases mixed with gold nanoparticles. The interferometers were tested for strain, temperature, and refractive index, being observed an increase in the sensitivity to the refractive index due to the addition of the nanoparticles. The next step was to evaluate the best laser parameters to create a layer of LIG around the interferometers. It was observed that for a power of 10% and an inscription speed of 100 mm/s, the formed LIG was quite porous, homogeneous, and had a leafy texture. Using a pulsed CO₂ laser, the polyimide was then irradiated and transformed into LIG, creating a second cavity within the interferometer. Due to this, the spectral response of the interferometers resembled the Vernier effect. The refractive index behavior was again evaluated, showing improvements in sensitivity up to 153 times due to the creation of the LIG cavity. The interferometers were then functionalized to achieve an affinity to cortisol, this being a novel approach, obtaining sensitivities of -4.1±0.2 nm/log(ng/mL) and -34±5 nm/log(ng/mL) for two interferometers without and with gold nanoparticles mixed into the polyimide, respectively. The increased sensitivity in these interferometers is justified by the presence of these gold nanoparticles in the polyimide. It was also possible to observe that the sensors are immune to interference from substances such as glucose, sucrose, fructose, and ascorbic acid. Regarding ammonia arrest, sensitivities of -80±10 nm/ppm were obtained for sensors where oxazine 170 perchlorate was mixed in the polyimide.