Studies on the interaction between humic substances and conducting polymers for sensor application

Abstract

Neste trabalho, foi investigada a interação entre substâncias húmicas e um polímero condutor (poli-(o-etoxianilina) -POEA), ambos em solução e filmes automontados. Os resultados mostram que as substâncias húmicas dopam a POEA por protonação, isto é evidenciado por espectroscopia UV-Vis e Raman. Os estudos de microscopia de força atômica (AFM) em filmes automontados mostram haver um aumento na rugosidade do filme polimérico quando este é exposto a substâncias húmicas (ácidos húmico e fúlvico), o que evidencia a existência de interação entre a POEA e as substâncias húmicas. Esta mudança na morfologia é reversível com a lavagem dos filmes com água, em concordância com as medidas elétricas, possibilitando a aplicação em sensores. Um sistema sensor formado por um arranjo de diferentes unidades sensoriais foi capaz de distinguir substâncias húmicas em solução aquosa, como é mostrado pela análise multivariada (análise da componente principal), o que é importante para controle da qualidade de água e solo.The interaction between humic substances and poly(o-ethoxyaniline) (POEA), a conducting polymer, was investigated for both solution and self-assembled films. The results have shown that the humic substances induce a doping of POEA by protonation, as indicated by UV-Vis and Raman spectroscopies. The atomic force microscopy (AFM) studies on the self-assembled films have shown that the average roughness of the polymer film has increased after exposing it to humic substances (fulvic and humic acids), consistent with the interaction between POEA and humic substances. However, this change in morphology is reversible by washing the films with water in agreement with the electrical data allowing using this system in sensor applications. Here, the sensor formed by an array of different sensing units was able to detect and distinguish humic substances in aqueous solution, as shown by multivariate analysis (principal component analysis). The motivation to detect humic substance comes due to its importance in terms of quality control of water or soil.

Electrodeposition and characterization of polypyrrole films on copper

“…The PB is the fully oxidized form of polypyrrole and is insulating in nature [46]. The UV spectrums of PPy films synthesized on copper in sodium acetate and sodium benzoate solutions are shown in Fig.…”

Electron paramagnetic resonance characterization of a humic acid-type polymer model

“…Venancio et al 15 demonstrated that the properties of HS can be used in the fabrication of sensor arrays for use in the classification of humic substances present in aqueous systems, as well as the possibility of using HS for the production of self-assembled films. A novel and simple method electrode with rapid preparation was developed with humic acid and polypyrrole.…”

Atomic Force Microscopy Study of Conductive Polymers

“…The size of the globules is comparable to the aggregates of polymer molecules in solution. Significantly, the adsorption mechanisms and film properties for polyanilines are altered by a mere change in pH [14], which has been exploited in sensors and other applications [15].…”