Transduction of Amine-Phosphate Supramolecular Interactions and Biosensing of Acetylcholine through PEDOT-Polyamine Organic Electrochemical Transistors.

Organic electrochemical transistors (OECTs) are important devices for the development of flexible and wearable sensors due to their flexibility, low power consumption, sensitivity, selectivity, ease of fabrication, and compatibility with other flexible materials. These features enable the creation of comfortable, versatile, and efficient portable devices that can monitor and detect a wide range of parameters for various applications. Herein, we present OECTs based on PEDOT-polyamine thin films for the selective monitoring of phosphate-containing compounds. Our findings reveal that supramolecular single phosphate-amino interaction induces higher changes in the OECT response compared to ATP-amino interactions, even at submillimolar concentrations. The steric character of binding anions plays a crucial role in OECT sensing, resulting in a smaller shift in maximum transconductance voltage and threshold voltage for bulkier binding species. The OECT response reflects not only the polymer/solution interface but also events within the conducting polymer film, where ion transport and concentration are affected by the ion size. Additionally, the investigation of enzyme immobilization reveals the influence of phosphate species on the assembly behavior of acetylcholinesterase (AchE) on PEDOT-PAH OECTs, with increasing phosphate concentrations leading to reduced enzyme anchoring. These findings contribute to the understanding of the mechanisms of OECT sensing and highlight the importance of careful design and optimization of the biosensor interface construction for diverse sensing applications.

Electrochemical Deposition of Polypyrrole in the Presence of Silanes as Adhesion Promoters.

Polypyrrole adhesion to indium-tin oxide electrodes was improved by adding pre-hydrolyzed alkoxysilanes to the electrodeposition media. The pyrrole oxidation and film growth rates were studied by potentiostatic polymerization in acidic media. The morphology and thickness of the films were studied by contact profilometry and surface-scanning electron microscopy. The bulk and surface semiquantitative chemical composition was studied by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Finally, the adhesion was studied by scotch-tape adhesion test, where both alkoxysilanes showed a significant improvement in adhesion. We proposed a hypothesis for the improvement in adhesion, that involves the formation of siloxane material as well as in situ surface modification of the transparent metal oxide electrode.

PEDOT-Polyamine-Based Organic Electrochemical Transistors for Monitoring Protein Binding.

The fabrication of efficient organic electrochemical transistors (OECTs)-based biosensors requires the design of biocompatible interfaces for the immobilization of biorecognition elements, as well as the development of robust channel materials to enable the transduction of the biochemical event into a reliable electrical signal. In this work, PEDOT-polyamine blends are shown as versatile organic films that can act as both highly conducting channels of the transistors and non-denaturing platforms for the construction of the biomolecular architectures that operate as sensing surfaces. To achieve this goal, we synthesized and characterized films of PEDOT and polyallylamine hydrochloride (PAH) and employed them as conducting channels in the construction of OECTs. Next, we studied the response of the obtained devices to protein adsorption, using glucose oxidase (GOx) as a model system, through two different strategies: The direct electrostatic adsorption of GOx on the PEDOT-PAH film and the specific recognition of the protein by a lectin attached to the surface. Firstly, we used surface plasmon resonance to monitor the adsorption of the proteins and the stability of the assemblies on PEDOT-PAH films. Then, we monitored the same processes with the OECT showing the capability of the device to perform the detection of the protein binding process in real time. In addition, the sensing mechanisms enabling the monitoring of the adsorption process with the OECTs for the two strategies are discussed.

Thin Polymer Films by Oxidative or Reductive Electropolymerization and Their Application in Electrochromic Windows and Thin-Film Sensors.

Electrically conducting and semiconducting polymers represent a special and still very attractive class of functional chromophores, especially due to their unique optical and electronic properties and their broad device application potential. They are potentially suitable as materials for several applications of high future relevance, for example flexible photovoltaic modules, components of displays/screens and batteries, electrochromic windows, or photocatalysts. Therefore, their synthesis and structure elucidation are still intensely investigated. This article will demonstrate the very fruitful interplay of current electropolymerization research and its exploitation for science education issues. Experiments involving the synthesis of conducting polymers and their assembly into functional devices can be used to teach basic chemical and physical principles as well as to motivate students for an innovative and interdisciplinary field of chemistry.

Interfacial Characterization of Polypyrrole/AuNP Composites towards Electrocatalysis of Ascorbic Acid Oxidation.

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs' deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior.

Conducting polymers/zinc oxide-based photocatalysts for environmental remediation: a review.

The accessibility to clean water is essential for humans, yet nearly 250 million people die yearly due to contamination by cholera, dysentery, arsenicosis, hepatitis A, polio, typhoid fever, schistosomiasis, malaria, and lead poisoning, according to the World Health Organization. Therefore, advanced materials and techniques are needed to remove contaminants. Here, we review nanohybrids combining conducting polymers and zinc oxide for the photocatalytic purification of waters, with focus on in situ polymerization, template synthesis, sol-gel method, and mixing of semiconductors. Advantages include less corrosion of zinc oxide, less charge recombination and more visible light absorption, up to 53%.

Recent Advances in Hole-Transporting Layers for Organic Solar Cells.

Global energy demand is increasing; thus, emerging renewable energy sources, such as organic solar cells (OSCs), are fundamental to mitigate the negative effects of fuel consumption. Within OSC's advancements, the development of efficient and stable interface materials is essential to achieve high performance, long-term stability, low costs, and broader applicability. Inorganic and nanocarbon-based materials show a suitable work function, tunable optical/electronic properties, stability to the presence of moisture, and facile solution processing, while organic conducting polymers and small molecules have some advantages such as fast and low-cost production, solution process, low energy payback time, light weight, and less adverse environmental impact, making them attractive as hole transporting layers (HTLs) for OSCs. This review looked at the recent progress in metal oxides, metal sulfides, nanocarbon materials, conducting polymers, and small organic molecules as HTLs in OSCs over the past five years. The endeavors in research and technology have optimized the preparation and deposition methods of HTLs. Strategies of doping, composite/hybrid formation, and modifications have also tuned the optical/electrical properties of these materials as HTLs to obtain efficient and stable OSCs. We highlighted the impact of structure, composition, and processing conditions of inorganic and organic materials as HTLs in conventional and inverted OSCs.

Functionalization of Conductive Polymers through Covalent Postmodification.

Organic chemical reactions have been used to functionalize preformed conducting polymers (CPs). The extensive work performed on polyaniline (PANI), polypyrrole (PPy), and polythiophene (PT) is described together with the more limited work on other CPs. Two approaches have been taken for the functionalization: (i) direct reactions on the CP chains and (ii) reaction with substituted CPs bearing reactive groups (e.g., ester). Electrophilic aromatic substitution, SEAr, is directly made on the non-conductive (reduced form) of the CPs. In PANI and PPy, the N-H can be electrophilically substituted. The nitrogen nucleophile could produce nucleophilic substitutions (SN) on alkyl or acyl groups. Another direct reaction is the nucleophilic conjugate addition on the oxidized form of the polymer (PANI, PPy or PT). In the case of PT, the main functionalization method was indirect, and the linking of functional groups via attachment to reactive groups was already present in the monomer. The same is the case for most other conducting polymers, such as poly(fluorene). The target properties which are improved by the functionalization of the different polymers is also discussed.

DNA purification using a novel γ-Fe2O3/PEDOT hybrid nanocomposite.

We report the synthesis and characterization of a new hybrid magnetic composite formed by the enveloping of magnetic iron oxide nanoparticles (γ-NP) with chains of the conductive polymer PEDOT, and its use for the efficient separation of DNA molecules from complex biological samples, allowing the high yield separation of a pure and high-quality DNA fraction. The successful formation of the γ-NP/PEDOT composite was confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, UV visible spectroscopy (UV-Vis), and magnetic hysteresis loop measurements. The nanocomposites showed an excellent capacity of DNA adsorption (Qe âˆ¼ 248 mg/g) in a model system consisting of salmon sperm DNA. When the γ-NP/PEDOT was used in protocols to extract the DNA from complex samples, the corresponding yield was in the range of 6.4 µg (blood) and 7.3 µg (bacteria), as evaluated quality by UV-Vis, PCR analysis, and electrophoresis assays. We also established that the captured DNA does not need to be detached from the nanocomposite for use as seeding material in PCR amplification experiments. These results and the simplicity of the protocols indicate that the γ-NP/PEDOT composite is a promising DNA absorbent, being competitive with the commercially available magnetic purification kits.

A descrição matemática da detecção eletroquímica da ergina, assistida pelos novos derivados triazólicos, dopados pelo íon amavadina / The mathematical description for the ergin electrochemical detection, assisted by amavadin ion doped triazolic derivatives / Descripción matemática de la detección electroquímica de ergina, asistida por los nuevos derivados de triazol, dopados por el ión amavadina

RESUMO Introdução: Pela primeira vez, o processo eletroanalítico da detecção da ergina (LSA) sobre um elétrodo, modificado por um derivado triazólico, dopado pelo íon amavadina, tem sido descrito teoricamente. Métodos: O modelo matemático, correspondente ao desempenho do sensor, tem sido desenvolvido e analisado do ponto de vista da teoria de estabilidade linear. Foi mostrado que a amavadina pode servir de modificador eficiente para a detecção eletroanalítica da ergina. Outrossim, a presença de um material orgânico no modificador reforça a capacidade da ergina de polimerizar-se, formando um compósito polimérico. Resultados: Os comportamentos oscilatório e monotô-nico são mais prováveis que no caso mais comum, haja vista a formação-deformação de compostos iônicos aquando da detecção eletroanalítica.

SUMMARY Introduction: For the first time, the electroanalytical process of ergin (LSA) determination over an electrode, modified by triazolic derivative, doped by an amavadin-ion, has been theoretically described. Methods: The mathematical model, correspondent to the sensor function, has been developed and analyzed by means of linear stability theory. It has been shown that the amavadin may serve as an efficient electrode modifier for the electroanalytical detection of ergin. Moreover, the presence of an organic material as electrode modifier reinforces the possibility of ergin polymerization, yielding a polymer composite. Results: The oscillatory and monotonic behavior is more probable than in the common case, considering the formation and destruction of the ionic compounds during the electroanalytical detection.

RESUMEN Introducción: Por primera vez se ha descrito teóricamente el proceso eletroanalítico de detección de ergina (LSA) en un electrodo, modificado por un derivado triazólico, dopado por el ión amavadina. Métodos: El modelo matemático, correspondiente al rendimiento del sensor, ha sido desarrollado y analizado desde el punto de vista de la teoría de la estabilidad lineal. Se ha demostrado que la amavadina puede servir como un modificador eficaz para la detección eletroanalítica de ergina. Además, la presencia de un material orgánico en el modificador refuerza la capacidad de la ergina para polimerizar, formando un compuesto polimérico. Resultados: Los comportamientos oscilatorios y monótonos son más probables que en el caso más común, dada la formación-deformación de compuestos iónicos durante la detección eletroanalítica.

CVD Conditions for MWCNTs Production and Their Effects on the Optical and Electrical Properties of PPy/MWCNTs, PANI/MWCNTs Nanocomposites by In Situ Electropolymerization.

In this work, the optimal conditions of synthesizing and purifying carbon nanotubes (CNTs) from ferrocene were selected at the first stage, where decomposition time, argon fluxes, precursor amounts, decomposition temperature (at 1023 K and 1123 K), and purification process (HNO3 + H2SO4 or HCl + H2O2), were modulated through chemical vapor deposition (CVD) and compared to commercial CNTs. The processing temperature at 1123 K and the treatment with HCl + H2O2 were key parameters influencing the purity, crystallinity, stability, and optical/electrical properties of bamboo-like morphology CNTs. Selected multiwalled CNTs (MWCNTs), from 1 to 20 wt%, were electropolymerized through in-situ polarization with conductive polymers (CPs), poly(aniline) (PANI) and poly(pyrrole) (PPy), for obtaining composites. In terms of structural stability and electrical properties, MWCNTs obtained by CVD were found to be better than commercial ones for producing CPs composites. The CNTs addition in both polymeric matrixes was of 6.5 wt%. In both systems, crystallinity degree, related to the alignment of PC chains on MWCNTs surface, was improved. Electrical conductivity, in terms of the carrier density and mobility, was adequately enhanced with CVD CNTs, which were even better than the evaluated commercial CNTs. The findings of this study demonstrate that synergistic effects among the hydrogen bonds, stability, and conductivity are better in PANI/MWCNTs than in PPy/MWCNTs composites, which open a promissory route to prepare materials for different technological applications.

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules.

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers.

O estudo teórico do desempenho dos polímeros condutores dos corantes azoicos na detecção eletroquímica de indigo-carmim / The theoretical study of the function of conducting polymers of the azo-dyes in the electrochemical detection of indigo-carmine

RESUMO O desempenho dos polímeros condutores dos corantes azoicos durante a detecção eletroquímica de indigo-carmim foi investigado do ponto de vista teórico, sendo o modelo, correspondente ao caso, descrito e analisado mediante a teoria de estabilidade lineal e da análise de bifiircações. Foi mostrado que o sistema eletroanalítico depende fortemente do pH, pois as concentrações excessivas dos prótons levam à ineficiência eletroanalítica, haja vista o bloqueio dos centros ativos da reação. No entretanto, malgrado o supracitado, os polímeros dos corantes azoicos são modificadores eficientes para determinação do indigo-carmim. A possibilidade das instabilidades oscilatória e monotônica também foi verificada.

SUMMARY The function of the conducting polymers of azo-dyes during the indigo-carmine electrochemical detection has been investigated from the theoretical point of view. The correspondent model has been described and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that the electroanalytical system depends strongly on pH, as the excessive protons concentrations drive the system to the electroanalytical inefficiency, as they block the reaction active sites. Nevertheless, despite of the mentioned, the azo-dyes conducting polymers are efficient modifiers for indigo-carmine electrochemical determination. The possibility of oscillatory and monotonic instabilities has also been verified.

Synthesis and Characterization of LiFePO4-PANI Hybrid Material as Cathode for Lithium-Ion Batteries.

This work focuses on the synthesis of LiFePO4-PANI hybrid materials and studies their electrochemical properties (capacity, cyclability and rate capability) for use in lithium ion batteries. PANI synthesis and optimization was carried out by chemical oxidation (self-assembly process), using ammonium persulfate (APS) and H3PO4, obtaining a material with a high degree of crystallinity. For the synthesis of the LiFePO4-PANI hybrid, a thermal treatment of LiFePO4 particles was carried out in a furnace with polyaniline (PANI) and lithium acetate (AcOLi)-coated particles, using Ar/H2 atmosphere. The pristine and synthetized powders were characterized by XRD, SEM, IR and TGA. The electrochemical characterizations were carried out by using CV, EIS and galvanostatic methods, obtaining a capacity of 95 mAhg-1 for PANI, 120 mAhg-1 for LiFePO4 and 145 mAhg-1 for LiFePO4-PANI, at a charge/discharge rate of 0.1 C. At a charge/discharge rate of 2 C, the capacities were 70 mAhg-1 for LiFePO4 and 100 mAhg-1 for LiFePO4-PANI, showing that the PANI also had a favorable effect on the rate capability.

Extraction of plasmid DNA by use of a magnetic maghemite-polyaniline nanocomposite.

We describe the use of a hybrid magnetic nanocomposite (HMNC) for the extraction and purification of plasmid DNA (pDNA) from Escherichia coli aqueous solutions. The HMNC, which was synthesized via emulsion polymerization, was characterized by transmission electron microscopy, scanning electron microscopy, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering and magnetic measurements. The results confirmed the incorporation of polyaniline (Pani) in its conducting form onto a core formed by the magnetic iron oxide, with the hybrid particles presenting an average size of (95 ±â€¯30) nm and a saturation magnetization of 30 emu/g. The yield, purity and quality of the pDNA purified by using the Pani HMNC were evaluated by UV-Vis spectroscopy, agarose gel electrophoresis, and Polymerase Chain Reaction (PCR), respectively. An average yield of ~6.9 µg was obtained in the DNA extraction process, with the collected material presenting a good purity (a ₳260/280 ratio in the 1.68-1.82 range) and an excellent quality, as confirmed by subsequent PCR assays. Hence, this HMNC appears as a promising material for use in pDNA purification protocols, and we suggest that this novel HMNC-based methodology can be of general interest and find widespread application in different biomedical procedures.

A novel nucleic acid fluorescent sensing platform based on nanostructured films of intrinsically conducting polymers.

When fluorophores attach to nanostructured films of intrinsically conducting polymers (ICPs), a quenching of their fluorescence may occur. We have exploited these characteristics for the development of polymeric films that can be used in a simple and efficient molecular diagnosis protocol based on the selective detection of nucleic acids. Our procedure rests on the fact that the fluorescence of 6-carboxyfluorescein-labeled single-stranded DNA (FAM-ssDNA) probes is quenched upon their immobilization on nanostructured ICP - polypyrrole (PPY) and polyaniline (PANI) - films deposited on polyethylene terephthalate (PET) substrates. Hybridization occurs whenever a sample with the complementary sequence is brought in contact with the immobilized probe, with the newly formed ds-DNA chains detaching from the flexible polymeric film and causing the restoration of the fluorescence. This sensing system exhibits a low background signal that depends on both the thickness and hydrophobicity of the films. As a model system, we used a FAM-ssDNA probe specific for the Leishmania infantum parasite. The results confirm this procedure as a simple, fast and highly sensitive scheme for the recognition of the target DNA, with a detection limit of the 1.1 nM and 1.3 nM for the PPY/PET and PANI/PET films, respectively. In addition, this biosensor has excellent stability and exhibits a good and reproducible performance even when used for the direct detection of ssDNA in relatively complex biological samples.

A descrição matemática da análise eletroquímica do fármaco hidroxizina em soluções ácidas sobre um ácido sulfônico, baseado num polímero condutor / The mathematical description for the electrochemical analysis of hydroxyzine drug in acid solution over a conducting-polymer based sulfonic acid

RESUMO Um caso interessante da aplicação dos polímeros condutores funcionalizados na análise do fármaco hidroxizina em soluções ácidas vem sendo descrito do ponto de vista teórico. Um modelo matemático, correspondente ao caso, é desenvolvido e analisado mediante a teoria de estabilidade linear e da análise de bifurcações. Foi detectado que o uso de um polímero condutor de natureza ácida no processo pode deixar o uso das soluções menos ácidas do fármaco sem prejuízo para a eficiência eletroanalítica. Outrossim, foi avaliada a influência para o processo do comportamento dos grupos amina. A possibilidade das instabilidades oscilatória e monotônica também foi verificada.

SUMMARY An interesting case of the application of the functionalized conducting polymer in the analysis of hydroxyzine drug in acid solutions is described from the theoretical point of view. A mathematical model, correspondent to the case, is developed and analyzed by means of linear stability theory and bifurcation analysis. It was detected that the use of an acid conducting polymer may permit the use of less acid solution without mischief of the electroanalytical efficiency. Moreover, the influence of the aminogroups' behavior to the process was also evaluated. The possibility of the oscillatory and monotonic instabilities has also been verified.

An All-Plastic Field-Effect Nanofluidic Diode Gated by a Conducting Polymer Layer.

The design of an all-plastic field-effect nanofluidic diode is proposed, which allows precise nanofluidic operations to be performed. The fabrication process involves the chemical synthesis of a conductive poly(3,4-ethylenedioxythiophene) (PEDOT) layer over a previously fabricated solid-state nanopore. The conducting layer acts as gate electrode by changing its electrochemical state upon the application of different voltages, ultimately changing the surface charge of the nanopore. A PEDOT-based nanopore is able to discriminate the ionic species passing through it in a quantitative and qualitative manner, as PEDOT nanopores display three well-defined voltage-controlled transport regimes: cation-rectifying, non-rectifying, and anion rectifying regimes. This work illustrates the potential and versatility of PEDOT as a key enabler to achieve electrochemically addressable solid-state nanopores. The synergism arising from the combination of highly functional conducting polymers and the remarkable physical characteristics of asymmetric nanopores is believed to offer a promising framework to explore new design concepts in nanofluidic devices.

O mecanismo do desempenho de poli-2-mercaptobenzimidazol na detecção eletroquímica de colesterol e as suas representações eletroquímica e matemática / The mechanism of electroanalytical function of 2-mercaptobenzimidazole in cholesterol electrochemical detection and its mathematical and chemical evaluations

O desempenho de poli-2-mercaptobenzimidazol na detecção eletroquímica de colesterol foi avaliado fenomenológica e matematicamente. O modelo matemático correspondente foi desenvolvido e analisado por meio de teoria de estabilidade lineal e análise de bifurcações. Os dados teóricos foram comparados com os experimentais e com os teóricos para os sistemas análogos.

The electroanalytical function of poly-2-mercaptobenzimidazole in cholesterol electrochemical detection was evaluated phenomenologically and mathematically. The corresponding mathematical model was developed and analyzed by linear stability theory and bifurcation analysis. The theoretical data were compared with the experimental data and with theoretical data for analogous systems.

Descripción matemática del desempeño electroanalítico de nanopartículas de derivados de níquel en la determinación cualitativa y cuantitativa de metanol / The mathematical description for the electroanalytical action of Ni-containing nanoparticles by quantitative and qualitative methanol determination

En este trabajo se desarrolló y se analizó, por medio de la teoría de estabilidad lineal y del análisis de bifurcaciones, el modelo matemático con que fue descrito el desempeño de nanopartículas de los derivados de níquel (solas y en compositos con el polímero conductor) en la determinación de metanol en el medio alcalino. Mediante el modelaje matemático, se derivaron las condiciones de estabilidad del estado estacionario, e inferidas las causas generales del comportamiento oscilatorio y monotónico. Los resultados del modelaje se compararon con los datos experimentales.

In this work, the mathematical model for the electroanalytical action of Ni-containing nanoparticles (by themselves and in a composite with a conducting polymer) in electrochemical qualitative and quantitative methanol detection in alkaline media is developed and analyzed by using of linear stability theory and bifurcation analysis. By the mathematical modeling, the steady-state stability conditions (the most exact sensing action requirements) and the causes for oscillatory and monotonic instabilities are derived. The result of the modeling is compared with the experimental data.