Detecção de pesticidas em cascas de alimentos por espectroscopia Raman amplificada por superfície e quimiometria

• Ano de defesa: 2024
• Autor(a) principal: Silva, Anderson Victor
• Orientador(a): Soares, Frederico Luis Felipe
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• dARK ID: ark:/80033/0013000001z93
• Idioma: por
• Instituição de defesa: Universidade Federal do Paraná
• Programa de Pós-Graduação: Programa de Pós Graduação em Química
• Departamento: Universidade Federal do Paraná
• País: Brasil
• Palavras-chave em Português: SERS; Raman; Grafeno; Quimiometria
• Área do conhecimento CNPq: Química Analítica
• Link de acesso: https://deposita.ibict.br/handle/deposita/757

The development of efficient methodologies for detection, elimination, and control of health risks caused by harmful substances, such as pesticides, is a topic of great relevance for scientific research. In this context, this work aims to optmize the synthesis of thin film of reduced graphene oxide with silver nanoparticles (rGO/AgNPs) through the liquid-liquid interfacial route (LLIR). The optimization seeks to intensity the SERS (Surface-enhanced Raman Scattering) signal for the detection of 4-aminothiophenol (4-ATP) and, subsequently, the pesticide ametryn (AMT). 4 ATP was employed as a probe to identify and evaluate the parameters influencing the variation of the SERS signal. Thus, a fractional factorial design and, subsequently a Box-Behnken design were used to investigate the following factors: concentration and masses of reagents, reaction times, and rotation speed. The values obtained for the optimal condition were: 7.0 mg of silver nitrate, 1000 RPM, 60 minutes of dispersion time, 150 mg of sodium borohydride, 0.01 mg mL-1 of graphene oxide, and 45 minutes of reduction time. Based on the results, an empirical response surface model was constructed to determine the ideal conditions for the material synthesis. The model showed a good data fit, but the regression was not considered significant. There was an increase in the Raman scattering approximately 21,500 times greater compared of the pure 4-ATP solution. The material was characterized by scanning electron microscopy (SEM), and UV-Vis and Raman spectroscopies. The characterization techniques indicated the growth and agglomeration of AgNPs on graphene sheets, which contributes to the increase SERS intensity. After that, the SERS substrate was used to detect the herbicide directly deposited on food peels, such as apple and potato. Thus, to ensure the reproducibility of signal acquisition, hyperspectral imaging measurements of potato and apple peels with different concentrations of ametryn were performed. From the hyperspectral images, it was possible to detect ametryn at low concentrations (1.0x10-7 mol L-1) with minimal sample preparation