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A typical cyclic voltammetry (CV) curve of polyaniline in HCl (pH 1) showing two sets of redox couples. The direction of potential scan is shown with the arrows.
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One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed...
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... electrochemical behavior and the redox states of polyaniline are typically studied using cyclic voltammetry (CV). The CV response of polyaniline has been well documented [31,49,50] and some of the key results are described here. The electrochemical behavior of polyaniline is dependent on many parameters including the applied potential, the choice of material and the surface area of the electrodes, composition of the electrolyte, and temperature, among others. A typical CV curve of a synthesized polyaniline is shown in Figure 3. The CV curve shows two sets of distinct redox activity as indicated by the two pairs of anodic and cathodic current peaks. The first set of a redox couple which appears between 0 and 0.25 V vs. silver/silver chloride reference electrode (Ag/AgCl) is associated with the conversion of the fully reduced leucoemeraldine base to the partially oxidized emeraldine, and the second set of redox current peaks occurring between 0.6 and 0.8 V vs. Ag/AgCl pertains to the conversion of emeraldine to the fully oxidized pernigraniline form. The potential of the first redox couple (peaks 1 and 1’) is largely independent of the pH whereas the potential for the second redox couple (peaks 2 and 2’) is strongly dependent on the pH value. This indicates that protons are involved in the redox reaction associated with the second peaks while the redox reaction related to the first anodic peak does not require protons as part of the reaction. Another point to note is that polyaniline is more easily oxidized in less acidic solutions, and this can be experimentally verified where the peaks 2 and 2’ shift to the left as the pH increases. Irreversible degradation also occurs at the second oxidation peak especially in strong acids. A linear relationship has been observed between peak height of the redox current and scan rate in a solution containing aniline and sulfuric acid solution which is indicative of an electron transfer limited process [51]. Using the CV data and the electrochemistry, the structural formula for polyaniline as it goes through the redox process can be interpreted. The following reactions have been proposed by Focke et al. [42] and a more detailed account can be found in [31]. Since the peak position of the ...
Citations
... The redox current peaks in the second set, which occur between 0.6 and 0.8 V vs. Ag/AgCl, are related to the conversion of emeraldine to the fully oxidized pernigraniline form. While the second redox couple (peaks Ox2 and Red1) potential is highly reliant on pH, the first redox couple (peaks Ox1 and Red2) potential is mostly independent of pH [73]. Since no proton is involved, this latter reduction reaction (Equation (4)) may be defined as follows: [74]. ...
Conductive polymers, such as polyaniline (PANI), have interesting applications, ranging from flexible electronics, energy storage devices, sensors, antistatic or anticorrosion coatings, etc. However, the full exploitation of conductive polymers still poses a challenge due to their low processability. The use of compatible stabilizers to obtain dispersible and stable colloids is among the possible solutions to overcome such drawbacks. In this work, potato starch was used as a steric stabilizer for the preparation of colloidal polyaniline (emeraldine salt, ES)/starch composites by exploiting the oxidative polymerization of aniline in aqueous solutions with various starch-to-aniline ratios. The polyaniline/starch bio-composites were subjected to structural, spectroscopic, thermal, morphological, and electrochemical analyses. The samples were then tested for their dispersibility/solubility in a range of organic solvents. The results demonstrated the formation of PANI/starch biocomposites with a smaller average size than starch particles, showing improved aqueous dispersion and enhanced solubility in organic solvents. With respect to previously reported PANI-EB (emeraldine base)/starch composites, the novel colloids displayed a lower overall crystallinity, but the conductive nature of PANI-ES enhanced its electrochemical properties, resulting in richer redox chemistry, particularly evident in its oxidation behavior, as observed through cyclic voltammetry. Finally, as proof of the improved processability, the colloids were successfully integrated into a thin polyether sulfone (PES) membrane.
... To enhance its processability, diverse approaches have been explored, with two notable strategies being chemical modification, such as doped PANI, and the development of substituted derivatives of PANI. Consequently, substantial endeavors are underway to explore alternative synthesis methodologies [15][16][17]. ...
... PANI formation involves a single-electron oxidation at the amino moiety of aniline (i.e., anodic process α), followed by rearrangement of the unpaired electron to the p position of the aromatic ring [16]. This allows the dimerization of electro-oxidized aniline moieties, leading to the formation of PANI emeraldine base after propagation [16]. ...
... PANI formation involves a single-electron oxidation at the amino moiety of aniline (i.e., anodic process α), followed by rearrangement of the unpaired electron to the p position of the aromatic ring [16]. This allows the dimerization of electro-oxidized aniline moieties, leading to the formation of PANI emeraldine base after propagation [16]. The emeraldine base then undergoes a reversible oxidation reaction (i.e., redox process β), thereby yielding an oxidation product with an unpaired electron, which is the emeraldine salt polaron-bipolaron [81]. ...
This study investigates potentiodynamic synthesis of polyaniline (PANI) using pencil graphite electrodes (PGEs), aiming to elucidate deposition mechanisms under simple experimental conditions. By exploring PANI electrosynthesis through electrochemical, spectroscopic, and computational approaches, valuable insights into the physicochemical aspects of aniline polymerization are gained. The proposed synthetic method was challenged for the development of a new molecularly imprinted polymer for chloramphenicol on the surface of PGEs to obtain an innovative impedimetric sensor. The sensing platform shows a linear response in the target concentration range between 0.1 and 17.5 nM, in aqueous solutions, with a limit of detection of 0.03 nM and a limit of quantification of 0.09 nM. The results obtained suggest that the synthesis method proposed provide a way to obtain stable and electroactive polyaniline film with huge potential application.
... On the reverse scan, the cathodic peak at 16 mV represents the electron transfer to the electrodeposited polyaniline film. The one at 570 mV probably corresponds to side reactions such as decomposition of the polymer [23][24][25]. ...
Monomers: gentian violet (GV), brilliant green (BG), aniline, and methyl violet (MV), as well as their copolymers, were electropolymerized and used to modify glassy carbon electrode (GCE) by enhancing the sensitivity of the electrode. This is due to their special characteristics of sensing ability of the electropolymerized polymers. The electropolymerization and characterization of these monomers and their copolymers were done using cyclic voltammetry (CV) on GCE as a working electrode against Ag/AgCl reference electrode and platinum wire as the counter electrode. The copolymers showed higher current peaks than their corresponding homopolymers. The electrochemical characterization of these polymers and copolymers was studied by scan rate effect each between 10 and 300 mV/s and pH effect between 1.56 and 5.30. After being modified by the copolymers: poly(BG-GV) and poly(BG-MV), the modified GCE showed good results in resolving the peaks of ascorbic acid and uric acid which otherwise showed an overlapped broad peak on bare GCE. The CV in bare GCE was scanned at different scan rates of 4 mM K3[Fe(CN)6] in 1 M KNO3 solution. The square root of scan rate dependence of peak current was plotted and the Randles–Sevcik equation was applied to determine the diffusion coefficient of Fe(CN)6³⁻ ion and which was 1.13 × 10–14 cm²/s. This was used to determine the area of the modified electrode after running the CV of 4 mM K3[Fe(CN)6] in 1 M KNO3 at different scan rates. Therefore, the electrochemical polymerization of organic dye polymers was able to increase the sensitivity of the electrode by increasing its area.
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... Element supplementation, such as that of carbon nanotubes (CNTs) [17,18], carbon nanofibers (CNFs) [19], or conductive polymers [20,21], could raise biomaterial scaffold conductivity. However, major drawbacks of using carbon additives or conductive polymers could arise from low conductivity under neutral pH, insolubility in water, and poor biofunctionality or biocompatibility, factors which severely limit their successful use in in vivo applications [22][23][24][25][26]. ...
Tissue engineering (TE) continues to be widely explored as a potential solution to meet critical clinical needs for diseased tissue replacement and tissue regeneration. In this study, we developed a poly(2-hydroxyethyl methacrylate-co-methacrylic acid) (pHEMA-co-MAA) based hydrogel loaded with newly synthesized conductive poly(3,4-ethylene-dioxythiophene) (PEDOT) and polypyrrole (PPy) nanoparticles (NPs), and subsequently processed these hydrogels into tissue engineered constructs via three-dimensional (3D) printing. The presence of the NPs was critical as they altered the rheological properties during printing. However, all samples exhibited suitable shear thinning properties, allowing for the development of an optimized processing window for 3D printing. Samples were 3D printed into pre-determined disk-shaped configurations of 2 and 10 mm in height and diameter, respectively. We observed that the NPs disrupted the gel crosslinking efficiencies, leading to shorter degradation times and compressive mechanical properties ranging between 450 and 550 kPa. The conductivity of the printed hydrogels increased along with the NP concentration to (5.10±0.37)×10 ⁻⁷ S/cm. In vitro studies with cortical astrocyte cell cultures demonstrated that exposure to the pHEMA-co-MAA NP hydrogels yielded high cellular viability and proliferation rates. Finally, hydrogel antimicrobial studies with staphylococcus epidermidis bacteria revealed that the developed hydrogels affected bacterial growth. Taken together, these materials show promise for various TE strategies.
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... In fact, a comprehensive understanding of the physical principles underlying surface morphology, electrical behavior, and mechanical properties are desired for the design of high-performance flexible devices using solution-processable components on flexible substrates [9][10][11][12][13] . This is the case for polyaniline (PANI)-based devices used to detect harmful gases which response depends on the type (dc or ac) electrical measurements to characterize the gas under examination [13][14][15][16][17][18][19][20] . This situation leads to measurement-tomeasurement variations [21,22] . ...
... The redox current peaks in the second set, which occur between 0.6 and 0.8 V vs. Ag/AgCl, is related to the conversion of emeraldine to the fully oxidized pernigraniline form. While the second redox couple (peaks Ox2 and Red1) potential is highly reliant on pH, the first redox couple (peaks Ox1 and Red2) potential is mostly independent of pH [73]. Since no proton is involved, this latter reduction reaction (eq. 1) may be defined as follows: [74]. ...
The processability of conductive polymers such as polyaniline (PANI) still poses a challenge due to their properties. The use of stabilizers, compatible and able to interact with PANI, to obtain dispersible and stable colloids is described in this work. To this aim, potato starch has been used as a steric stabilizer for the preparation of polyaniline (emeraldine salt, ES)/starch biocomposites, by exploiting oxidative polymerization of aniline in aqueous solutions containing different ratios of aniline and starch (% w/w). The polyaniline/starch biocomposites were subjected to structural and spectroscopic analyses, thermal analysis, morphological analysis and electrochemical analysis. The samples were then tested for their dispersibility/solubility in various organic solvents. The results showed the formation of PANI/starch biocomposites with an overall smaller size than starch particles, with improved aqueous dispersion and solubility in organic solvents. Although X-ray diffraction and differential scanning calorimetry analyses indicated a loss of crystallinity in the biocomposites, the cyclic voltammetry tests showed that all PANI ES/starch biocomposites display improved redox exchange properties.
... A higher sensor response can be achieved than using NPs due to the larger active area undergoing catalytic reactions. There are a number of research works using NPs for gas sensors [17][18][19][20][21]; however, the research related to atomic clusters for amperometric sensors is very limited [11][12][13][14][22][23][24][25][26]. In this paper, we describe how to fabricate an atomic gold cluster for gas measurement using a bulky AGS system. ...
... PANI is discovered in the mid-19th century. It is one of the oldest CPs and has been extensively studied and used in many fields due to its low cost, simple fabrication, low toxicity, biocompatibility, etc. [21,36,37]. The molecule of PANI possesses either benzenoid or quinonoid or both types [11,12,14]. ...
The Amperometric Gas Sensor (AGS) uses an electrode as the transducer element which converts its signal into a current from the electrochemical reaction of analytes taking place at the electrode surface. Many attempts to improve AGS performance, such as modifying the working electrode, applying a particular gas-permeable membrane, and selecting the proper electrolyte, etc., have been reported in the scientific literature. On the other hand, in the materials community, atomic gold has gained much attention because its physicochemical properties dramatically differ from those of gold nanoparticles. This paper provides an overview of the use of atomic gold in AGSs, both in a bulky AGS and a miniaturized AGS. In the miniaturized AGS, the system must be redesigned; for example, the aqueous electrolyte commonly used in a bulky AGS cannot be used due to volatility and fluidity issues. A Room Temperature Ionic Liquid (RTIL) can be used to replace the aqueous electrolyte since it has negligible vapor pressure; thus, a thin film of RTIL can be realized in a miniaturized AGS. In this paper, we also explain the possibility of using RTIL for a miniaturized AGS by incorporating a quartz crystal microbalance sensor. Several RTILs coated onto modified electrodes used for isomeric gas measurement are presented. Based on the results, the bulky and miniaturized AGS with atomic gold exhibited a higher sensor response than the AGS without atomic gold.
... 24,25 PANI is one of the most useful conducting polymers, because of its high absorption coefficients in visible light, intriguing redox properties, less density than metallic substances, energy storage, ease of synthesis, relatively excellent conductivity, ecologically stable compound, cheapness, beneficial optical and electrical characteristics, and ability to be reversibly converted from conduction to insulation through the use of acid-base reactions or electrochemical or chemical doping. [26][27][28][29] Conducting polymer PANI with different nanocomposites shows different application fields such as waste water treatment, biomedical applications, and electromagnetic wave absorptions. [30][31][32][33] The use of PANI-Zn-Cu ferrite materials is justified by their special set of qualities, which enable them to be used in a wide range of applications. ...
In a wide range of applications, from consumer electronics to cutting‐edge industrial and scientific equipment, high dielectric permittivity ( ε ′) polymers are crucial for maximizing the performance and efficiency of electrical and electronic systems. Researchers strive to create and perfect these materials to meet the changing demands of modern technology. It is generally known that freestanding bare polymers cannot achieve high dielectric values; however, the mixing of multiple materials that are distinct is an effective technique for developing high dielectric hybrids. Polymer‐based nanoarchitectures are particularly beneficial for use in the storage of energy due to characteristics such as excellent mechanical strength, noncorrosive nature, lightweight, affordability, versatility, thermal and electrical shielding. The primary aim of this investigation is to prepare copper ferrite, zinc ferrite, and copper 0.5 zinc 0.5 ferrite (CuFe 2 O 4 , ZnFe 2 O 4 , and Cu 0.5 Zn 0.5 Fe 2 O 4 ) nanoparticle (NP) via combustion technique using egg albumen as a fuel and these NPs were separately dispersed in polyaniline (PANI) matrix by the method of ex situ polymerization of aniline with an objective to enhance the electrical properties for energy storage and electromagnetic wave applications. Flexible freestanding films were casted via solution casting technique. X‐ray diffractogram of 5 wt.% NP dispersed PANI films confirmed the presence of NPs in the PANI matrix. Scanning electron micrograph images show the homogeneous dispersion of NPs into PANI matrix. Rather than the pure ferrite NPs, mixed ferrite highly enhance the permittivity of PANI films without much increasing its loss factor, the obtained values of ε ′ of all the three ferrite added films are higher than polyvinylidene fluoride (PVDF)/(Mn 0.2 Zr 0.2 Cu 0.2 Ca 0.2 Ni 0.2 )Fe 2 O 4 nanofiller. In this work notably for 5 wt.% Cu 0.5 Zn 0.5 Fe 2 O 4 dispersed film shows the highest value of ε ′ (7291) for 100 Hz at 150°C with ultralow loss factor (0.08) which is the key characteristic of an energy storage material. Thus, this present study leads the formation of a cost effective, flexible, high dielectric material, which can be a potential alternate to replace PVDF/(Mn 0.2 Zr 0.2 Cu 0.2 Ca 0.2 Ni 0.2 )Fe 2 O 4 and polyvinyl alcohol/Ni 0.65 Cu 0.35 Fe 2 O 4 polymer blends for energy storage applications.
... 15 American Nobel laureate Mac Diannid proposed the most authoritative PANI molecular structure model. PANI chains consist of two structural units, a reduced [-B-NH-B-NH-] repeat unit and an oxidized [-B-N]Q]N-] repeat unit, in which B and Q respectively denote the C 6 H 4 rings in the benzenoid and quinonoid forms, as shown in Fig. 2. 16,17 Different redox states can be converted to each other through specic redox reactions. Only the PANI in the intrinsic state can obtain conductive properties by doping, such as proton acid doping. ...
An overview of nanostructured PANI gas sensors and chemiresistive or heterojunction-based PANI composite gas sensors.
... Moreover, water-based acrylic resins are biodegradable and environmentally friendly, having high-mechanical strength and transparency. 3,4 However, the TE efficiency of polyaniline is still lower than inorganic compounds. Superior properties in OTE can be achieved by two mechanisms: doping of the conjugated polymers or mixing with different types of filler materials based on carbon, such as graphene (GR). ...
Thermoelectric (TE) materials have attracted attention for offering a green option for power generation, due to their ability to convert thermal energy into electricity. In recent years, a promising way to achieve efficiency in TE properties has been proposed based on composites of conjugated polymers, such as polyaniline (PANI), and carbon nanomaterials such as graphene (GR). Since polyaniline and GR composites are promising fillers for organic thermoelectric materials (OTE), we expanded their investigations for a ternary system (TS), providing materials with multiple functionalities, and high performance. In this research work, a TS based on an acrylic matrix (ACR), GR, and PANI was successfully prepared through the combination of in situ polymerization of aniline in contact with GR and mechanical mixture of the resulting hybrid with an ACR. Structural and morphological characterization confirmed that GR affected PANI morphology and crystallinity. The band gap determination by Tauc's relation indicated the occurrence of π‐π interaction between the chains and an increase of the electrical conductivity of the composites allowed to infer a synergistic effect. The measured Seebeck coefficient reached a maximum value of −17.02 μVK⁻¹ and the highest power factor obtained was 4.94 μWm⁻¹ K⁻² for the ACR/PANI sample, indicating a material with promising thermoelectric properties.
