Nanocompósitos de polímero conjugado dopados com nanopartículas plasmônicas de prata e sua aplicação como sensor na detecção de pesticidas
Data
2024-12-19
Autores
Rodrigues, Rebeca da Rocha 
Orientadores
Péres, Laura Oliveira
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Este trabalho investigou filmes nanoestruturados de compósitos do copolímero conjugado poli(9,9-dioctilfluoreno-co-3,4-etilenodioxitiofeno) (PDOF-co-PEDOT) e nanopartículas de prata (AgNP), como substratos para a técnica de Espalhamento Raman Intensificado por Superfície (efeito SERS), visando detectar o pesticida clorpirifós, encontrado em concentrações inadequadas na água de consumo no Brasil. O copolímero foi sintetizado via rota de Suzuki e as AgNP, esféricas e triangulares, foram obtidas via redução do sal de prata (nitrato de prata). O material compósito contendo o nanopolímero (NCP) ou PDOF-co-PEDOT e AgNP apresentou alterações ópticas associadas à interação copolímero-AgNP, como deslocamento dos máximos de absorção e emissão para maiores comprimentos de onda devido a formação de agregados poliméricos e excímeros. Posteriormente, filmes foram preparados pelas técnicas de Spin Coating, Drop Casting e Langmuir-Blodgett. Imagens de TEM e AFM confirmaram a estruturação das dispersões e transferência bem-sucedida para substratos sólidos, embora a homogeneidade dependesse da geometria das AgNP e método de deposição. Filmes com AgNP esféricas produziram sinais SERS mais intensos devido à geração uniforme de hot spots, enquanto desafios na reprodutibilidade foram atribuídos à dificuldade de distribuição homogênea das AgNP nos filmes. A presença de PDOF-co-PEDOT ampliou o efeito SERS ao facilitar a transferência de carga entre as AgNP e o pesticida, demonstrando limites de detecção promissores de 0,0015 g L-1 e 0,0014 g L-1 (filme PDOF-co-PEDOT/AgNP e NCP/AgNP, respectivamente), porém ainda superiores ao permitido para água potável (30 g L-1). Os resultados destacam o potencial dos substratos híbridos SERS para aplicações futuras, com oportunidades de otimização para maior sensibilidade e reprodutibilidade.
This study investigated nanostructured films of composites composed of the conjugated copolymer poly(9,9-dioctylfluorene-co-3,4-ethylenedioxythiophene) (PDOF-co-PEDOT) and silver nanoparticles (AgNP) as SERS substrates for the detection of the pesticide chlorpyrifos, often found at unsafe concentrations in drinking water in Brazil. The copolymer was synthesized via the Suzuki route, while spherical and triangular AgNP were prepared by reducing silver nitrate. Films were fabricated using Spin Coating, Drop Casting and Langmuir-Blodgett techniques, exhibiting optical changes associated with interactions with the AgNP, such as red-shifting of absorption and emission maxima due to polymer aggregation and excimer formation. TEM and AFM imaging confirmed the structuring of dispersions and their successful transfer to solid substrates, though homogeneity was dependent on the AgNP geometry. Films containing spherical AgNP generated more intense SERS signals due to the uniform creation of hot spots, while challenges in reproducibility were linked to difficulties in achieving homogeneous AgNP distribution. The presence of PDOF-co-PEDOT enhanced the SERS effect by facilitating charge transfer between the AgNP and the pesticide, demonstrating promising detection limits of 0.0015 g L-1 and 0.0014 g L-1 (for PDOF-co-PEDOT/AgNP and NCP/AgNP films, respectively), although still above the permissible level for potable water (30 μg L⁻¹). These results underscore the potential of hybrid SERS substrates for future applications, highlighting opportunities for optimization to achieve greater sensitivity and reproducibility.
This study investigated nanostructured films of composites composed of the conjugated copolymer poly(9,9-dioctylfluorene-co-3,4-ethylenedioxythiophene) (PDOF-co-PEDOT) and silver nanoparticles (AgNP) as SERS substrates for the detection of the pesticide chlorpyrifos, often found at unsafe concentrations in drinking water in Brazil. The copolymer was synthesized via the Suzuki route, while spherical and triangular AgNP were prepared by reducing silver nitrate. Films were fabricated using Spin Coating, Drop Casting and Langmuir-Blodgett techniques, exhibiting optical changes associated with interactions with the AgNP, such as red-shifting of absorption and emission maxima due to polymer aggregation and excimer formation. TEM and AFM imaging confirmed the structuring of dispersions and their successful transfer to solid substrates, though homogeneity was dependent on the AgNP geometry. Films containing spherical AgNP generated more intense SERS signals due to the uniform creation of hot spots, while challenges in reproducibility were linked to difficulties in achieving homogeneous AgNP distribution. The presence of PDOF-co-PEDOT enhanced the SERS effect by facilitating charge transfer between the AgNP and the pesticide, demonstrating promising detection limits of 0.0015 g L-1 and 0.0014 g L-1 (for PDOF-co-PEDOT/AgNP and NCP/AgNP films, respectively), although still above the permissible level for potable water (30 μg L⁻¹). These results underscore the potential of hybrid SERS substrates for future applications, highlighting opportunities for optimization to achieve greater sensitivity and reproducibility.