Filmes nanoestruturados de polianilina e argila para aplicação em sensores ambientais

In this study the development of environmental sensors began from the fabrication of nanoestrutured films obtained by the technique of Layer-by-Layer (LbL). The films of obtaining a nanocomposite material composed of polyaniline (PAni) and montmorillonite clay nanoparticles using the technique mentioned above, allows a detailed study and essential for this work, wich are for subject to various characterizations, wich include ultraviolet visible spectroscopy (UV-vis), Fourier Transformed Infrared Spectroscopy (FTIR) and Raman, scanning electron microscopy (SEM), is used to visualize the morphological construction of LbL films, X-ray diffraction (XRD), wich allows for characterization and molecular atomic arrangements in solids, atomic interplanar distance and determination of crystal structure, this study uses the technique to check the spacing and thickness of the films and built specially for characterizing the intercalation of polymer and clay in order to get results showing the intercalation of polymer precisely the spaces of lamellar clay. The electrochemical sensor developed here is intend to apply for environmental control in order to detect contaminants in water, such as heavy metals (copper, lead and cadmium). The evaluation of these sensors that are made from nanostructured PAni films and nanoparticles of clay is made from the electrochemical detection by cyclic voltammetry and improved method of stripping square wave voltammetry, for such contaminants in samples of knows concentrations. The LbL films made in this work show quite interesting results, highlighting the partial intercalation of PAni in the interlamelar spaces of Clay (characterized by XRD) and the heavy metal detection by voltammetry.Universidade Federal de Minas GeraisO desenvolvimento de sensores ambientais iniciou-se a partir da fabricação de filmes nanoestruturados obtidos através da técnica de automontagem camada por camada (LbL, do inglês Layer-by-Layer). Os filmes fabricados a partir da obtenção de um material nanocompósito composto de polianilina (PAni) e nanopartículas de argila montmorilonita através da técnica LbL motivaram esse trabalho. Esses filmes foram submetidos às espectroscopias na região do ultravioleta visível (UV-vis), no infravermelho (FTIR, do inglês Fourier Transformed Infrared Spectroscopy) e Raman, microscopias eletrônica de varredura (MEV), difração de raio-X (DRX), que permite caracterizações aos arranjos atômicos e moleculares em sólidos, além de verificar a estruturação das camadas de polímero e argila, a fim de obtermos resultados que comprovem a intercalação do polímero nos espaços interlamelares da argila. O sensor eletroquímico aqui desenvolvido tem como finalidade a aplicação para controle ambiental, a fim de detectar metais pesados (cobre, chumbo e cádmio). A avaliação destes sensores obtidos de filmes nanoestruturados de PAni e nanopartículas de argilas é feito a partir da detecção eletroquímica por voltametria cíclica, além de medidas de voltametria de redissolução por onda quadrada, realizadas em soluções de concentrações conhecidas. Os filmes LbL fabricados neste trabalho apresentaram resultados bastante interessantes, principalmente no que diz respeito a intercalação parcial da PAni nos espaços interlamelares da argila (caracterizada por DRX) e a detecção dos metais pesados por voltametria

Electrical and electrochemical measurements in nanostructured films of polythiophene derivatives

Thin films from polythiophene derivatives can be fabricated by some experimental methods, including the Langmuir techniques, which are particularly suitable if some degree of molecular control is required. In this study, electrical and electrochemical measurements in Langmuir-Schaefer and spin-coated films of polythiophene derivatives were carried out in order to compare the influence of the deposition technique in these properties. Through cyclic voltammetry and UV-visible absorption measurements it was possible to estimate the energy diagrams for all the polythiophene films. Besides, electrochromic effect in the polythiophene thin films was observed. (C) 2015 Elsevier Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Nanocomposites based on LbL films of polyaniline and sodium montmorillonite clay

Layer-by-layer (LbL) films were fabricated with alternating layers of montmorillonite (Na+-MMT) and either polyaniline emeraldine salt (PAni-ES) or polyethyleneimine (PEI). Molecular-level interactions between the film components probed with FTIR and Raman spectroscopies led to distinct arrangements for the clay nanostructures. The electrostatic interaction between charged groups in PAni-ES and Na+-MMT caused aggregation with the polymer chains located around the clay sheets, while for the PEI/Na+-MMT LbL film the interlayer distance was increased owing to intercalation. The LbL films deposited onto ITO substrates were used as electrochemical sensors for detecting heavy metal ions simultaneously using electrochemical measurements by square wave anodic stripping voltammetry (SWAS). (C) 2014 Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Layer-by-Layer Films Based on Carbon Nanotubes and Polyaniline for Detecting 2-Chlorophenol

Electrochemical sensors made with layer-by-layer (LbL) films of functionalized multi-walled carbon nanotubes (MWCNT5-COO-) and polyaniline (PAni) deposited onto ITO substrates were used to detect 2-chlorophenol. Concentrations down to ppm level could be detected with square wave voltammetry (SWV), owing to synergistic effects between PAni and nanotubes, whose molecular-level interactions in the LbL films were inferred using FTIR and Raman spectroscopy. Significantly, the Raman spectra of MWCNTs-COO-/PAni LbL films indicated that the conducting properties of PAni were preserved upon adsorption on the ITO substrates, with homogeneous nanocomposites being formed according to Scanning Electron Microscopy (SEM) images.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Sao Carlos, PPG Ciencia Mat, BR-18052780 Sao Carlos, SP, BrazilUniv Estadual Paulista, UNESP POSMAT, BR-17033660 Bauru, SP, BrazilUniv Estadual Paulista, FCT, UNESP, BR-19060900 Presidente Prudente, SP, BrazilUniversidade Federal de São Paulo, Inst Ciencias Ambientais Quim & Farmaceut, BR-09910720 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Inst Ciencias Ambientais Quim & Farmaceut, BR-09910720 São Paulo, SP, BrazilWeb of Scienc

Synergy between polyaniline and OMt clay mineral in Langmuir-Blodgett films for the simultaneous detection of traces of metal ions

We report on Langmuir-Blodgett (LB) films made with emeraldine salt polyaniline (PAni-ES) and organophilic montmorillonite clay mineral (OMt), where synergy between the components was reached to yield an enhanced performance in detecting trace levels of cadmium (Cd2+), lead (Pb2+) and copper (Cu2+). Detection was carried out using square wave anodic stripping (SWAS) voltammetry with indium tin oxide (ITO) electrodes modified with LB films of PAni-ES/OMt nanocomposite, whose data were compared to those obtained with electrodes coated with neat PAni-ES and neat OMt LB films. The enhanced performance in the nanocomposite may be attributed to the stabilizing and ordering effect promoted by OMt in PAni-ES Langmuir films, which then led to more homogeneous LB films. According to X-ray diffraction data, the stacking of OMt layers was preserved in the LB films and therefore the PAni-ES chains did not cause clay mineral exfoliation. Instead, OMt affected the polaronic state of PAni-ES as indicated in UV-vis, Raman and FTIR spectra, also consistent with the changes observed for the Langmuir films. Taken together these results do indicate that semiconducting polymers and clay minerals may be combined for enhancing the electrical properties of nanostructures for sensing and related applications.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Dynamic behavior of surface-enhanced raman spectra for rhodamine 6G interacting with gold nanorods: implication for analyses under wet versus dry conditions

We report the dynamic behavior of surface-enhancement Raman scattering (SERS) spectra using rhodamine 6G dye (R6G, 10–8 mol L–1) adsorbed on gold nanorods (AuNRs). SERS spectra displayed a strong time-dependence intensity in wet to dry transition states. FEG-SEM images reveal a stacking of AuNRs organization that can lead to Raman signal improvements due to the formation of a 3D hot spot matrix that acts as a trap for target molecules. AuNRs nanostructured films were efficiently employed to form SERS substrates. The independent random AuNR organization in the SERS spectra exhibits a characteristic profile of intensities due to different dielectric environmental conditions. Despite the variations observed in the spectra array, a pattern was recognized by statistical analysis. Multidimensional analysis ensured the distinction of the study’s requirements applied to the SERS response, exhibiting a silhouette coefficient of 0.92 with the least-squares projection technique. Changes in the SERS spectra profile from wet to dry state conditions of R6G dye solution can be interpreted as the dynamic behavior of R6G molecules correlated to distinct molecular adsorption and (or) surface distribution of the R6G molecules proving different plasmonic resonances. Simulations obtained from BEM calculation in experimental data corroborate that the SERS enhancement is strongly dependent on the nanoparticle coupling in nanoscale and the dielectric environment3881388147CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP150003/2016-1; 408985/2016-0; 407592/ 2016-888887.333739/2019-002013/22127-2; 2016/21070-

Investigation of the Synergistic Effect of Layer-by-Layer Films of Carbon Nanotubes and Polypyrrole on a Flexible Electrochemical Device for Paraquat Sensing

This research aims to study flexible sensors based on a poly(butylene adipate-co-terephthalate) (PBAT) biodegradable polymer and graphite. Sensors were modified through the layer-by-layer (LbL) technique to improve their electrochemical behavior for paraquat (PQ) detection. Nanostructured films were obtained by alternating layers of anionic and cationic materials, carbon nanotubes (CNTs), and polypyrrole (PPY), respectively. The devices, with and without modification, were characterized by contact angle, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Electrochemical characterization was labeled via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). PQ molecules were detected using the differential pulse voltammetry (DPV) technique in a concentration range of 0.1 to 2.1 µM. The sensor detection limit (LOD) was obtained using the analytical curve, with it being equal to 0.073 µM. The LbL film gPBAT(PPY/CNT)n sensor showed good stability, reproducibility, and repeatability, with recovery values ranging from 99.4% to 109.3% for PQ when the analyzed samples were contaminated with tap water. The produced electrodes have the advantage of being flexible, disposable, reproducible, and of low manufacturing cost, which makes them attractive for portable environmental analysis

Sensitive colorimetric assay based on peroxidase‐like activity of CEO2 nanoparticles supported on SBA‐15 mesoporous silica to determination of H2O2

We report a novel combination of nanomaterial proposed as a peroxidase‐like enzymatic mimic for detection of H2O2, where CeO2 nanoparticles dispersed on SBA‐15 through synthesis by the impregnation‐decomposition cycles method (IDC). The system displays a good peroxidase‐like activity and catalyzes to the oxidation of 3,3',5,5‘‐tetramethylbenzidine (TMB) by H2O2. KM values were calculated between 0.04 and 0.08 mM for different (CeO2/SBA‐15)x catalyst system, the results demonstrates that the combination of these materials displayed a good affinity to TMB substrate, consequently improving the colorimetric assay, due to uniform mesostructures of SBA‐15 and their high surface areas. A detailed study of synergistic effects between CeO2NPs and SBA‐15 support were held in order to understand how these effects can improve the colorimetric assay. Additionally, high resolution transmission electron microscopy (HR‐TEM), energy dispersive X‐ray spectroscopy (EDX), Raman spectroscopy, thermogravimetric analysis (TGA), small angle X‐ray scattering (SAXS) and textural properties were utilized for characterization of the prepared catalysts systems4721602167CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São PauloNão temNão tem2014/26420-9; 2013/22127-