Tracking metal ions with polypyrrole thin films adhesively bonded to diazonium-modified flexible ITO electrodes

The Influence of Roughness on the Properties of Electroactive Polypyrrole

This study describes the properties of electroactive polypyrrole and its applications, with a focus on the roughness of the material. This parameter is crucial as it influences the applicability of coated layers, leading to highly adherent coatings or programmed wettability. The first raised aspect covers the electrodeposition procedure, which can help tailor the desired smoothness determined by roughness parameters. Features such as the deposition method, synthetic solution components, potential boundaries, substrate type, and utilized additives are evaluated. In the following section, the application aspects are discussed with a focus on modern, currently developed subjects such as medical applications, including cell-adherent coatings, antibacterial coatings, and drug delivery modules, as well as more technological fields like improved adhesion to the substrate and the improved mechanical properties of the deposited coating.

Maintaining Electrochemical Performance of Flexible ITO-PET Electrodes under High Strain

Flexible electrode materials, particularly indium tin oxide (ITO)-coated polyethylene terephthalate (PET), have attracted the attention of researchers for a wide variety of applications. However, there has been limited attention to the effects of electrode flexibility during electrochemical processes. In this research article, we studied how bending commercially available ITO-PET electrodes impacts the electrodeposition process of polyaniline (PANI). Thicker ITO layers start cracking at a normalized strain of 0.10 (bending radius of 10 mm), and cracking becomes detrimental to full deposition at a normalized strain of 0.16 or higher (bending radius of 6 mm or lower). Thinner ITO layers were evaluated as electrodes in electrochemical applications; however, the higher resistance of these electrodes prevented uniform electrodeposition of PANI. In order to overcome the issues of cracking, conductive thin films and copper tape were explored as low-cost methods for electrically bridging cracks in the electrode. While conductive thin films reduced the resistance effect, copper tape was found to fully restore the original electrochemical activity as measured by chronoamperometry and enable uniform electrodeposition at a bending radius as low as 3 mm. This strategy was then demonstrated by performing electrochromic bleaching of PANI under high-strain conditions. These studies illustrate some of the limitations of ITO-PET electrodes and strategies for overcoming these limitations for future applications that require a high degree of flexibility in a transparent electrode substrate.

Enhancing conductivity in polymers: The role of metal ions in conducting polymer systems

As metal ion inclusion has a substantial effect on conducting polymer's mechanical, optical, and electrical properties, it has attracted a lot of attention. This article delves into the complex role of metal ions in conducting polymers, explaining how they affect functionality, structural stability, and conductivity enhancement. The review starts with a synopsis of conducting polymers and doping processes before diving into the particular ways that metal ions interact with polymer matrices to alter their electronic structure and charge transport characteristics. The importance of characterization techniques in comprehending the structure–property correlations is highlighted in the discussion of metal‐ion doped conducting polymer studies. In addition, the paper looks at the uses of conducting polymers doped with metal ions in numerous sectors, including energy storage, electronics, and sensors. The difficulties in attaining accurate control over doping concentrations and guaranteeing stability over an extended period are discussed, as well as potential avenues for future development in this area. This review offers important insights into the development and optimization of functional materials for a variety of applications by thoroughly investigating the function of metal ions in conducting polymers.

The Alphabet of Nanostructured Polypyrrole

This review is devoted to polypyrrole and its morphology, which governs the electroactivity of the material. The macroscopic properties of the material are strictly relevant to microscopic ordering observed at the local level. During the synthesis, various (nano)morphologies can be produced. The formation of the ordered structure is dictated by the ability of the local forces and effects to induce restraints that help shape the structure. This review covers the aspects of morphology and roughness and their impact on the final properties of the modified electrode activity in selected applications.

Simultaneous Sensing of Cd(II), Pb(II), and Cu(II) Using Gold Nanoparticle-Modified APTES-Functionalized Indium Tin Oxide Electrode: Effect of APTES Concentration

In this work, indium tin oxide (ITO) electrodes were functionalized with varying 3-aminopropyltriethoxysilane (APTES) concentration percentages (0.5, 0.75, 1.0, and 2.0 wt %) to obtain the optimum conditions for the assembly of the as-synthesized gold nanoparticles (AuNPs). The AuNP coverage, wettability, and electrochemical performance of the modified electrodes were evaluated. The AuNP/0.75% APTES-ITO-modified electrode exhibited uniform coverage of AuNPs and high electrochemical performance for the simultaneous detection of Cd(II), Pb(II), and Cu(II) ions. Under the optimum conditions, the AuNP/0.75% APTES-ITO-modified electrode showed a linear detection range of 5-120 ppb and limit of detection of 0.73, 0.90, and 0.49 ppb for the simultaneous detection of Cd(II), Pb(II), and Cu(II) ions, respectively, via square wave anodic stripping voltammetry. The modified electrode demonstrated good anti-interference toward other heavy metal ions, good reproducibility, and suitability for application in environmental sample analysis.

Voltammetric Determination of Hg2+, Zn2+, and Pb2+ Ions Using a PEDOT/NTA-Modified Electrode

A novel electrochemical sensor for determining trace levels of Hg²⁺, Pb²⁺, and Zn²⁺ ions in water using square wave voltammetry (SWV) is reported. The sensor is based on a platinum electrode (Pt) modified by poly(3,4-ethylenedioxythiophene) and N _α,N _α-bis-(carboxymethyl)-l-lysine hydrate (NTA lysine) PEDOT/NTA. The modified electrode surface (PEDOT/NTA) was prepared via the introduction of the lysine-NTA group to a PEDOT/N-hydroxyphthalimide NHP electrode. The (PEDOT/NTA) was characterized via cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The effects of scan rates on the electrochemical properties of the polymer electrode were also investigated. The electrochemical results were used to estimate the coverage of the electrode polymer surface and its electrostability in background electrolyte solutions. Several analytical parameters, such as polymer film thickness, metal deposition time, and pH of the electrolyte, were examined. Linear responses to Hg²⁺, Pb²⁺, and Zn²⁺ ions in the concentration range of 5-100 μg L^-1 were obtained. The limits of detection (LODs) for the determination of Hg²⁺, Pb²⁺, and Zn²⁺ ions were 1.73, 2.33, and 1.99 μg L^-1, respectively. These promising results revealed that modified PEDOT/NTA films might well represent an important addition to existing electrochemical sensor technologies.

Densification of Diazonium-Based Organic Thin Film as Bioelectrical Interface

Aryl diazonium chemistry generates a covalently attached thin film on various materials. This chemistry has diverse applications owing to the stability, ease of functionalization, and versatility of the film. However, the uncontrolled growth into a polyaryl film has limited the controllability of the film's beneficial properties. In this study, we developed a multistep grafting protocol to densify the film while maintaining a thickness on the order of nanometers. This simple protocol enabled the full passivation of a nitrophenyl polyaryl film, completely eliminating the electrochemical reactions at the surface. We then applied this protocol to the grafting of phenylphosphorylcholine films, with which the densification significantly enhanced the antifouling property of the film. Together with its potential to precisely control the density of functionalized surfaces, we believe this grafting procedure will have applications in the development of bioelectrical interfaces.

Polypyrrole-Wrapped Carbon Nanotube Composite Films Coated on Diazonium-Modified Flexible ITO Sheets for the Electroanalysis of Heavy Metal Ions

Highly sensitive multicomponent materials designed for the recognition of hazardous compounds request control over interfacial chemistry. The latter is a key parameter in the construction of the sensing (macro) molecular architectures. In this work, multi-walled carbon nanotubes (CNTs) were deposited on diazonium-modified, flexible indium tin oxide (ITO) electrodes prior to the electropolymerization of pyrrole. This three-step process, including diazonium electroreduction, the deposition of CNTs and electropolymerization, provided adhesively-bonded, polypyrrole-wrapped CNT composite coatings on aminophenyl-modified flexible ITO sheets. The aminophenyl (AP) groups were attached to ITO by electroreduction of the in-situ generated aminobenzenediazonium compound in aqueous, acidic medium. For the first time, polypyrrole (PPy) was electrodeposited in the presence of both benzenesulfonic acid (dopant) and ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA), which acts as a chelator. The flexible electrodes were characterized by XPS, Raman and scanning electron microscopy (SEM), which provided strong supporting evidence for the wrapping of CNTs by the electrodeposited PPy. Indeed, the CNT average diameter increased from 18 ± 2.6 nm to 27 ± 4.8, 35.6 ± 5.9 and 175 ± 20.1 after 1, 5 and 10 of electropolymerization of pyrrole, respectively. The PPy/CNT/NH₂-ITO films generated by this strategy exhibit significantly improved stability and higher conductivity compared to a similar PPy coating without any embedded CNTs, as assessed by from electrochemical impedance spectroscopy measurements. The potentiometric response was linear in the 10⁻⁸–3 × 10⁻⁷ mol L⁻¹ Pb(II) concentration range, and the detection limit was 2.9 × 10⁻⁹ mol L⁻¹ at S/N = 3. The EGTA was found to drastically improve selectivity for Pb(II) over Cu(II). To account for this improvement, the density functional theory (DFT) was employed to calculate the EGTA–metal ion interaction energy, which was found to be −374.6 and −116.4 kJ/mol for Pb(II) and Cu(II), respectively, considering solvation effects. This work demonstrates the power of a subtle combination of diazonium coupling agent, CNTs, chelators and conductive polymers to design high-performance electrochemical sensors for environmental applications.

A novel fluorescent sensor based on electrosynthesized benzene sulfonic acid-doped polypyrrole for determination of Pb(II) and Cu(II)

To develop conducting organic polymers (COPs) as luminescent sensors for determination of toxic heavy metals, a new benzene sulfonic acid-doped polypyrrole (PPy-BSA) thin film was electrochemically prepared by cyclic voltammetry (CV) on flexible indium tin oxide (ITO) electrode in aqueous solution. PPy-BSA film was characterized by FTIR spectrometry, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The optical properties of PPy-BSA were investigated by ultraviolet (UV)-visible absorption and fluorescence spectrometry in dimethylsulfoxide (DMSO) diluted solutions. PPy-BSA fluorescence spectra were strongly quenched upon increasing copper(II) ion (Cu²⁺ ) and lead(II) ion (Pb²⁺ ) concentrations in aqueous medium, and linear Stern-Volmer relationships were obtained, which indicated the existence of a main dynamic fluorescence quenching mechanism. BSA-PPy sensor showed a high sensitivity for detection of both metallic ions, Cu²⁺ and Pb²⁺ , with very low limit of detection values of 3.1 and 18.0 nM, respectively. The proposed quenching-fluorimetric sensor might be applied to the determination of traces of toxic heavy metallic ions in water samples.