A review on high-throughput synthesis, deposition of thin films and properties of polyaniline

Superhydrophobic Polyaniline-Siloxane Coatings with Excellent Barrier and Active Corrosion Protection Properties for Mild Steel

Although superhydrophobic surfaces have attracted much attention in research, their high cost, poor durability, and challenging manufacturing processes have prevented their widespread application. Here, we describe a simple method of preparing superhydrophobic polyaniline (PANI) pigments and their application in protective coatings. Doping polyaniline pigments with low surface energy perfluorodecanoic acid (PFDA) allowed them to overcome their intrinsic high surface energy, and the resultant PANI-PFDA pigments showed superhydrophobicity. The superhydrophobic PANI-PFDA pigments with different weight percentages were incorporated into a polydimethylsiloxane (PDMS) coating to prepare the superhydrophobic coating. We endeavored to examine the role that hydrophobicity played in enhancing corrosion resistance and looked into the highest concentration of pigment that the coating could withstand. Additionally, studies were carried out on the coating's adherence to the metal and the stability of hydrophobicity at various pH levels. The results showed that PANI-PFDA pigments improved the hydrophobicity and corrosion resistance in the PDMS coating without compromising its robustness and durability. Electrochemical impedance spectroscopy studies revealed that 40 wt % PANI-PFDA content in the PDMS coating provided the best corrosion protection, and this coating could offer active corrosion protection when an artificial defect was made in the coating.

New Polyaniline Derivative with Two Central Ester Groups: Synthesis, Characterization, and Theoretical Study

A new polyaniline derivative was prepared to study the formation of quinoid-diimine units in its polymer. The monomer and polymer were experimentally and theoretically characterized. Both polymers have one or two electron-withdrawing groups as side substituents. The polymers' quinoid-diimine unit composition is affected by the electron-withdrawing side groups of aniline. The presence of the quinoid-diimine group diminished for the two electron-withdrawing groups of aniline. The polymer conductivity is different than with respect to polyemeraldine, associated with the quinoid-diimine units' composition. The quinoid-diimine composition is strongly increased in the polymer containing one electron-withdrawing group. Moreover, the polymer presented good solubility in organic solvents and moderate thermal stability.

High-Throughput Exploration of Triple-Cation Perovskites via All-in-One Compositionally-Graded Films

Many devices heavily rely on combinatorial material optimization. However, new material alloys are classically developed by studying only a fraction of giant chemical space, while many intermediate compositions remain unmade in light of the lack of methods to synthesize gapless material libraries. Here report a high-throughput all-in-one material platform to obtain and study compositionally-tunable alloys from solution is reported. This strategy is applied to make all Csx MAy FAz PbI3 perovskite alloys (MA and FA stand for methylammonium and formamidinium, respectively), in less than 10 min, on a single film, on which 520 unique alloys are then studied. Through stability mapping of all these alloys in air supersaturated with moisture, a range of targeted perovskites are found, which are then chosen to make efficient and stable solar cells in relaxed fabrication conditions, in ambient air. This all-in-one platform provides access to an unprecedented library of compositional space with no unmade alloys, and hence aids in a comprehensive accelerated discovery of efficient energy materials.

Conductive Polymers and Their Nanocomposites: Application Features in Biosensors and Biofuel Cells

Conductive polymers and their composites are excellent materials for coupling biological materials and electrodes in bioelectrochemical systems. It is assumed that their relevance and introduction to the field of bioelectrochemical devices will only grow due to their tunable conductivity, easy modification, and biocompatibility. This review analyzes the main trends and trends in the development of the methodology for the application of conductive polymers and their use in biosensors and biofuel elements, as well as describes their future prospects. Approaches to the synthesis of such materials and the peculiarities of obtaining their nanocomposites are presented. Special emphasis is placed on the features of the interfaces of such materials with biological objects.

Transparent Electronics for Wearable Electronics Application

Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.

Understanding the Effect of Deposition Technique on the Structure-Property Relationship of Polyaniline Thin Films Applied in Potentiometric pH Sensor

The comprehension of potentiometric pH sensors with polymeric thin films for new and advanced applications is a constant technological need. The present study aimed to explore the relationship between the sensitivity and correlation coefficient of potentiometric pH sensors and the structure-property relationship of polyaniline thin films. The effect of the deposition method on the sample's properties was evaluated. Galvanostatically electrodeposited and spin-coated polyaniline thin films were used as the sensing stage. Samples were electrodeposited with a current density of 0.5 mA/cm2 for 300, 600, and 1200 s and were spin coated for 60 s with an angular velocity of 500, 1000, and 2000 rpm. The electrodeposited set of films presented higher average sensitivity, 73.4 ± 1.3 mV/pH, compared to the spin-coated set, 59.2 ± 2.5 mV/pH. The electrodeposited films presented higher sensitivity due to their morphology, characterized by a larger roughness and thickness compared to spin-coated ones, favoring the potentiometric response. Also, their oxidation state, evaluated with cyclic voltammetry and UV-VIS spectroscopy, corroborates their sensing performance. The understanding of the structure-property relationship of the polymeric films affecting the pH detection is discussed based on the characteristics of the deposition method used.

Antibacterial and biocompatible polyaniline-doped titanium oxide layers

Titanium anodization has been shown to produce crystalline oxides exhibiting photocatalytic reactions that form reactive oxygen species (ROS) when exposed to UV light. The ROS subsequently attack bacteria cells, and thus reduce bacteria attachment on titanium implant surfaces. Polyaniline (PANI) is a conductive polymer that has shown antibacterial properties when electropolymerized onto titanium. Our research group hypothesized the addition of PANI to crystalline titanium oxide surfaces would increase the available free electrons and thus increase photocatalytic activity (PCA). This research led to the development of a novel single-step anodization approach for PANI doping crystalline titanium oxide layers. The objective of the present study was to determine the proper aniline electrolyte concentration needed to maximize the PCA and reduce bacterial attachment on the formed oxides. Aniline concentrations up to 1 M were added into a 1 M sulfuric acid electrolyte. The formed oxides exhibited increased PANI surface coverage but decreased anatase and rutile crystalline titanium oxide phase formation with increasing aniline electrolyte concentrations. Despite exhibiting the lowest levels of anatase and rutile formation, the 0.75 M and 1 M aniline oxides with the greatest PANI surface coverage also exhibited the highest PCA levels. 1 M aniline oxides showed significantly higher PCA under UVA irradiation compared to oxides formed from aniline concentrations up to 0.5 M (p < 0.001). 0.75 M aniline oxides exhibited significant reductions in Staphylococcus aureus attachment with or without UVA irradiation compared to control oxides without PANI. MTT and live/dead assays confirmed cytocompatibility and nearly 100% cell viability for the PANI doped oxides.

Polyaniline-Based Infrared Dynamic Patterned Encoder with Multiple Thermal Radiation Characteristics

A high-level infrared dynamic patterned encoder (IR-DPE) possesses prospective applications for energy-harvesting and information, but a simple and reliable method for fabrication remains challenging. Herein, we first report an IR-DPE with multiple thermal radiation characteristics based on polyaniline (PANI). Specifically, the electron-beam evaporation technique is introduced to obtain the divanadium pentoxide (V2O5) coating, and then the V2O5 film acts as an oxidant to drive in situ polymerization of the PANI film. During the process, we experimentally explore the relationship between the thickness of V2O5 and the emissivity of PANI to obtain up to six emissivity levels and achieve the IR pattern integrated into multiple thermal radiation characteristics. The device shows multiple thermal radiation characteristics at the oxidized state, realizing a pattern visible with the IR camera and the same thermal radiation properties at the reduced state, leading to the pattern concealed in the IR regime. In addition, the highest emissivity tunability of the device is to be tuned from 0.40 to 0.82 (Δε = 0.42) at 2.5-25 μm. Meanwhile, the device exhibits a maximum temperature control of up to 5.9 °C. The results show the enormous potential of IR-DPEs for IR information transfer and thermal management.

Production of biologically active non-woven textiles from recycled polyethylene terephthalate

Recently, various studies have focused on the development of multifunctional non-woven polyethylene terephthalate (PT; polyester) textiles. Herein, we introduce multifunctional non-woven polyester fabrics by pad dry curing silver nitrate (AgNO₃ ) and aniline monomer into plasma-pretreated non-woven PT textile. This creates a nanocomposite layer of silver nanoparticles (AgNPs) and polyaniline (PANi) on the fabric surface. In order to prepare a non-woven fibrous mat, we applied the melt-spinning technique on previously shredded recycled PT plastic waste. On the surface of the cloth, PANi was synthesized by REDOX polymerization of aniline. Due to the oxidative polymerization, the silver ions (Ag⁺ ) were converted to Ag⁰ NPs. PANi acted as a conductor while AgNPs inhibited the growth of microorganisms. Microwave-assisted curing with trimethoxyhexadecylsilane (TMHDS) gave PT textiles with superhydrophobic properties. The morphological studies were performed using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The stiffness and breathability of finished non-woven PT textile materials were analyzed to establish their comfort levels. Both of Escherichia coli and Staphylococcus aureus were used to test the efficacy of the AgNPs-treated textiles as antimicrobial materials. Moreover, the processed polyester textiles showed excellent electrical conductivity and great ultraviolet-ray blocking.

Thin Films of Polyaniline-Based Nanocomposites with CeO2 and WO3 Metal Oxides Applied to the Impedimetric and Capacitive Transducer Stages in Chemical Sensors

There is a recognized need for the development of cost-effective, stable, fast, and optimized novel materials for technological applications. Substantial research has been undertaken on the role of polymeric nanocomposites in sensing applications. However, the use of PANI-based nanocomposites in impedimetric and capacitive electrochemical sensors has yet to be understood. The present study aimed to explore the relationship between the sensitivity and linearity of electrochemical pH sensors and the composition of nanocomposites. Thin films of PANI/CeO₂ and PANI/WO₃ were deposited via spin coating for characterization and application during the electrochemical impedance and capacitance spectroscopy (EIS and ECS) transduction stages. The findings showed that the optimized performance of the devices was extended not only to the sensitivity but also to the linearity. An increase of 213% in the ECS sensitivity of the PANI/CeO₂ compared to the metal oxide and an increase of 64% in the ECS linearity of the PANI/WO₃ compared to the polymeric sensitivity were reported. This study identified the structure-property relationship of nanocomposite thin films of PANI with metal oxides for use in electrochemical sensors. The developed materials could be applied in devices to be used in different fields, such as food, environment, and biomedical monitoring.

Emerging Applications of Versatile Polyaniline-Based Polymers in the Food Industry

Intrinsically conducting polymers (ICPs) have been widely studied in various applications, such as sensors, tissue engineering, drug delivery, and semiconductors. Specifically, polyaniline (PANI) stands out in food industry applications due to its advantageous reversible redox properties, electrical conductivity, and simple modification. The rising concerns about food safety and security have encouraged the development of PANI as an antioxidant, antimicrobial agent, food freshness indicator, and electronic nose. At the same time, it plays an important role in food safety control to ensure the quality of food. This study reviews the emerging applications of PANI in the food industry. It has been found that the versatile applications of PANI allow the advancement of modern active and intelligent food packaging and better food quality monitoring systems.

A novel single-step anodization approach for PANI-doping oxide surfaces to improve the photocatalytic activity of titanium implants

Crystalline titanium oxides have shown photocatalytic activity (PCA) and the formation of antibacterial reactive oxygen species (ROS) when stimulated with UV light. Polyaniline (PANI) is a conductive polymer that has shown antibacterial effects. Previously, titanium oxides have been PANI-doped using a multi-step approach. In the present study, we compared PANI-doped specimens produced with a two-step method (ACV), to PANI-doped specimens produced by a novel single-step direct anodization (AAn) method, and a control group of anodized un-doped specimens. The surface morphology, oxide crystallinity, surface elemental composition, surface roughness, surface wettability, oxide adhesion, corrosion resistance, PCA, and ROS generation of each oxide group were evaluated. All groups exhibited mixed anatase and rutile phase oxides. The AAn group revealed less anatase and rutile, but more PANI-surface coverage. The AAn group exhibited significantly increased PCA after 60 minutes of direct UVA illumination compared to the ACV group, despite containing lower amounts of anatase and rutile. The ACV and AAn groups showed significant increases in ROS production after 4 hours UVA illumination while the control group showed similar ROS production. These findings suggested that PANI doping using the novel direct anodization technique significantly improved PCA even for oxides containing less crystallinity. The S. aureus attachment response to each oxide group was also compared under UVA pre-illumination, UVA direct illumination, and no illumination (dark) lighting conditions. Although no significant differences were shown in the bacterial response, both PANI-doped groups exhibited less average bacterial attachment compared to the control group. The response of MC3T3-E1 pre-osteoblast cells to each oxide group was evaluated using MTT and live/dead assays, and no evidence of cytotoxicity was found. Since many, if not most, titanium implant devices are routinely anodized as a part of the manufacturing processes, these study findings are applicable to a wide variety of implant applications.

A Review on Polyaniline: Synthesis, Properties, Nanocomposites, and Electrochemical Applications

The development in the use of polyaniline (PANI) in advanced studies makes us draw attention to the presented research and combine it into one study like this one. The unique composition of PANI qualifies it for use in electrochemical applications in addition to many other applications whose use depends on its mechanical properties. Based on this, it is necessary to limit the reactions that produce PANI and the cheapest cost, and then limit the current uses in the formation of nanocomposites with metals, their oxides, and/or carbon nanocomposites in order to determine what is missing from them and work on it again to expand its chemistry. The development in the use of PANI in advanced studies makes us draw attention to the research presented on PANI and combine it into one study. One of the very important things that made PANI possess a very huge research revolution are preparation in a variety of ways, easy and inexpensive, from which a daily product can be obtained with very high purity, as well as its distinctive properties that made it the focus of researchers in various scientific departments. The unique structure of PANI, which is easy to prepare in its pure form or with various chemical compounds including metals, metal oxides, and carbon nanomaterials (such as carbon nanotubes, graphene, graphene oxide, and reduced graphene oxide), qualifies it for use in electrochemical applications. The various studies reviewed showed that PANI gave good results in the applications of super capacitors. In some of the studies mentioned later, it gave a specific capacitance of 503 F/g, cycle stability 85% at 10,000 cycles, energy density 8.88 kW/kg, and power density 96 W h/kg. It was also noted that these values improved significantly when using PANI with its nanocomposites. Because of its good electrical conductivity and the possibility of preparing it with a high surface area with nanostructures in the form of nanowires, nanofibers, and nanotubes, PANI was used as a gas sensor. We have noticed, through the studies conducted in this field, that the properties of PANI as a basic material in gas sensors are greatly improved when it is prepared in the form of PANI nanocomposites, as explained in detail later. From this review, we tried with great effort to shed light on this attractive polymer in terms of its different preparation methods, its distinctive properties, its nanocomposites, and the type of polymerization used for each nanocomposites, as well as its applications in its pure form or with its nanocomposites in the supercapacitor and gas sensor applications.

High specific surface area triphenylamine-based covalent organic framework/polyaniline nanocomposites for supercapacitor application

Covalent organic frameworks (COFs) possess extraordinary porosity, structural diversity, and good electrochemical performance, and have broad application prospects in the field of energy storage. However, the low conductivity of COFs limits its further development. In this paper, the electrochemical performance of triphenylamine-based COFs (TPA-COFs) was improved by compounding with highly conductive polyaniline (PANI) using solvothermal synthesis process. The highly conductive polyaniline fibers can act as conductive path in the composite to accelerate the charge transfer rate of TPA-COFs. The π-π interaction between TPA-COFs and PANI effectively decreases the agglomeration degree of PANI. The good dispersion of composite results in that the specific surface area of TPA-COFs/PANI-20 is high as 1233.9 m2 g−1, which provides rich diffusion channels for electrolyte ions. Moreover, the strong π-π structure in the composites ensures the stability of the material skeleton. Thus, TPA-COFs/PANI composite exhibits excellent rate characteristics and cycling stability.

Mediation of water-soluble oligoaniline by phenol in the aniline-persulfate system under alkaline conditions

Although synthesis of oligoaniline (OANI) by persulfate and aniline has been investigated in the recent years, the impact of phenol on the synthesized soluble OANI is still not clear. In this study, our results indicate that phenol and pH mediate the production of the blue water-soluble OANI (OANI_blue) in the reaction between sodium persulfate (SPS) and aniline under alkaline conditions, and the yields of OANI_blue increase with increasing concentrations of phenol and pH values. Quenching experiments rule out the contributions of SO₄˙^- and ˙OH to aniline oxidation and imply that the non-radical activation of SPS is an important pathway in the formation of OANI_blue. MALDI-TOF-MS analysis indicates that phenol apparently inhibits the polymerization degree of aniline in that the molecular weights of OANI_blue gradually decrease from 1586.4 to 684.6 when phenol is increased from 0 to 2.0 mM. FTIR and Raman analyses confirm the structure of aniline oligomers in OANI_blue and indicate that phenol inhibits the phenazine-like structure in OANI_blue and facilitates the transformation of benzenoid rings to quinoid rings in the oxidation products. However, simultaneous activation of SPS by phenol and aniline is likely to occur in the reaction system with the formation of PhNH˙, as indicated by DFT calculations. The high scavenging reactivity of phenol towards both PhNH₂˙⁺ and PhNH˙ implies that PhNH₂˙⁺ and PhNH˙ are not the intermediates in the formation of OANI_blue. DFT calculations also reveal that apart from the one-electron transfer pathway between aniline and SPS, the two-electron transfer pathway is also likely to occur in the presence of phenol, resulting in the formation of PhNH⁺/PhN˙˙ without producing PhNH₂˙⁺ and PhNH˙. The produced PhNH⁺/PhN˙˙ intermediates then couple with aniline, PhNH⁺, aminophenyl sulfate and its hydrolysate to form dimers, trimers, oligomers, and eventually OANI_blue. This study not only describes a novel method to prepare water-soluble OANI, but also gives new insight on the importance of phenol in the production of OANI_blue.

Autogenous Oxidation/Reduction of Polyaniline in Aqueous Sulfuric Acid

In this work, we have shown through open circuit potential experiments that in aqueous sulfuric acid solutions, a thick polyaniline film undergoes autogenous oxidation when reduced below a threshold potential and autogenous reduction when oxidized above the threshold potential. This phenomenon is associated with the high resonance stability of polarons in long polyaniline chains present in thicker films. We have determined the rates of these reactions using a linear sweep chronopotentiometry technique. We propose that the oxidation reaction of polyaniline produces polarons with a concomitant reduction of hydrogen ions to hydrogen radicals, which further combine with each other to produce the hydrogen molecule in the absence of dissolved oxygen. On the other hand, at high potentials polarons are reduced with the concomitant oxidation of water to hydroxyl radicals. Both the radicals are stabilized due to the interaction of their unpaired electrons with pi-electrons of the aromatic rings of the polymer backbone. At the equilibrium value of the open circuit potential, both the hydrogen radicals and hydroxyl radicals are generated at equal rates and react with each other to form water.

Recent advances in the utilization of polyaniline in protein detection: a short review

Attachment of biomolecules to polyaniline.

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%.

Peculiarities of Oxidative Polymerization of Diarylaminodichlorobenzoquinones

New oxidative polymerization monomers-diarylaminodichlorobenzoquinones were synthesised by alkylating aniline, m-phenylenediamine and methanilic acid with chloranil. Oxidative polymerization of diarylaminodichlorobenzoquinones was studied for the first time in relation to the concentration of the monomer, acid, and oxidant/monomer ratio. It was found that the synthesized monomers are highly active in the polymerization reaction, and the oxidation rate grows with the increase in the acid concentration. Only one arylamine group is involved in the polymerization reaction. The optimal oxidant/monomer ratio is stoichiometric for one arylamine group, despite the bifunctionality of the monomers. It was shown that the type of the substituent in the aniline ring (electron donor or electron acceptor) determines the growth of the polymer chain and the structure of the resulting conjugated polymers. A mechanism for the formation of active polymerization centers for diarylaminodichlorobenzoquinones was proposed. FTIR-, NMR-, X-ray photoelectron spectroscopy, and SEM were used to identify the structure of the synthesized monomers and polymers. The obtained polymers have an amorphous structure and a loose globular morphology. The frequency dependence of the electrical conductivity was studied.

Preparations, Properties, and Applications of Polyaniline and Polyaniline Thin Films-A Review

Polyaniline (PANI) is a famous conductive polymer, and it has received tremendous consideration from researchers in the field of nanotechnology for the improvement of sensors, optoelectronic devices, and photonic devices. PANI is doped easily by different acids and dopants because of its easy synthesis and remarkable environmental stability. This review focuses on different preparation processes of PANI thin film by chemical and physical methods. Several features of PANI thin films, such as their magnetic, redox, and antioxidant, anti-corrosion, and electrical and sensing properties, are discussed in this review. PANI is a highly conductive polymer. Given its unique properties, easy synthesis, low cost, and high environmental stability in various applications such as electronics, drugs, and anti-corrosion materials, it has attracted extensive attention. The most important PANI applications are briefly reviewed at the end of this review.

Electrochemical Dopamine Biosensor Based on Poly(3-aminobenzylamine) Layer-by-Layer Self-Assembled Multilayer Thin Film

Dopamine (DA) is an important neurotransmitter which indicates the risk of several neurological diseases. The selective determination with low detection limit is necessary for early diagnosis and prevention of neurological diseases associated with abnormal concentration of DA. The purpose of this study is to fabricate a poly(3-aminobenzylamine)/poly(sodium 4-styrenesulfonate) (PABA/PSS) multilayer thin film for use as an electrochemical DA biosensor. The PABA was firstly synthesized using a chemical oxidation method of 3-aminobenzylamine (ABA) monomer with ammonium persulfate (APS) as an oxidant. For electrochemical biosensor, the PABA/PSS thin film was fabricated on fluorine doped tin oxide (FTO)-coated glass substrate using the layer-by-layer (LBL) self-assembly method. The optimized number of bilayers was achieved using SEM and cyclic voltammetry (CV) results. The electroactivity of the optimized LBL thin film toward detection of DA in neutral solution was studied by CV and amperometry. The PABA/PSS thin film showed good sensitivity for DA sensing with sensitivity of 6.922 nA·cm-2·µM-1 and linear range of 0.1-1.0 µM (R2 = 0.9934), with low detection limit of 0.0628 µM, long-term stability and good reproducibility. In addition, the selectivity of the PABA/PSS thin film for detection of DA under the common interferences (i.e., ascorbic acid, uric acid and glucose) was also presented. The prepared PABA/PSS thin film showed the powerful efficiency for future use as DA biosensor in real sample analysis.

Colorimetric determination of acid phosphatase activity and inhibitor screening based on in situ polymerization of aniline catalyzed by gold nanoparticles

A colorimetric assay for acid phosphatase (ACP) was constructed that is based on in situ polymerization of aniline catalyzed by gold nanoparticles (AuNPs). Aniline can be polymerized by ammonium persulfate (APS) in acidic condition and form gold-polyaniline core-shell nanoparticles (Au@PANI NPs) in the presence of AuNPs with the assistance of sodium dodecyl sulfate (SDS). AuNPs were also found to accelerate the polymerization process of aniline and thus shorten the reaction time. Upon the introduction of ascorbic acid (AA), the oxidant APS was consumed via the redox reaction. That led to the suppression of the formation of PANI. Consequently, ACP activity can be supervised on the basis of hydrolysis of 2-phospho-L-ascorbic acid trisodium salt (AAP) catalyzed by ACP to release AA. With the increase of ACP activity, the intensity ratio of the absorbance at λ₇₀₅ nm (A₇₀₅) and the absorbance at λ₅₃₀ nm (A₅₃₀) gradually decreased and the color gradually changed from dark-green to light-green to blue-gray to purple and eventually to pink. This method for ACP determination worked in the range 0.40 to 2.00 U·L^-1. The detection limit is 0.043 U·L^-1. The assay was applied to determine ACP in human serum. The recovery ranged from 81.0 to 104.6%. Relative standard deviation was less than 5%. This suits the request for biological sample analysis. Graphical abstract Schematic presentation of the colorimetric determination of acid phosphatase activity and inhibitor screening based on in situ polymerization of aniline catalyzed by gold nanoparticles. : acid phosphatase (ACP); : gold nanoparticles (AuNPs); : gold-polyaniline core-shell nanoparticles (Au@PANI NPs); ascorbic acid (AA); 2-phospho-L-ascorbic acid trisodium salt (AAP).

Impact of Acidity Profile on Nascent Polyaniline in the Modified Rapid Mixing Process-Material Electrical Conductivity and Morphological Study

Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet-visible light (UV-Vis) spectroscopy was used for the polaronic band and the p-p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π-π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher doping level for this polymer. For final powder products, particle size distributions were also estimated, proving that PANI (5.0 M) is characterized by a larger number of small particles; however, these particles can more easily agglomerate and form larger structures. The X-ray diffraction (XRD) patterns revealed an equilibrium between the amorphous and semicrystalline phase in the doped PANI. A higher electrical conductivity value was measured for polymer synthesized in a higher acid concentration. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis showed that the molecular composition of the polymers was the same; hence, the difference in properties was a result of local ordering.

The First Stages of Chemical and Electrochemical Aniline Oxidation—Spectroscopic Comparative Study

There are several types of aniline oligomers that can be formed in the early stages of aniline oxidation: linear oligomers with repeating units joined in para positions, and various branched and polycyclic oligomers, being the two most important groups. The fraction of these different oligomeric groups depends upon the reaction conditions of aniline oxidation. The aim of this study was to analyze the first products of the chemical and electrochemical oxidation of aniline at the (starting) pH 1 and 7, in order to specify the conditions of the formation of phenazine-like oligomers, and to test the theory that they have an important role in polyaniline film formation. We have confirmed that phenazine-like oligomers do not form at pH 1, neither in the chemical nor the electrochemical oxidation of aniline; however, they form in both chemical and electrochemical oxidation of aniline at pH 7. Phenazine-like oligomers are thus definitely not necessary intermediates for PANI film formation, not even in the chemical polymerization of aniline. Finally, the redox behavior of phenazine-like oligomers was demonstrated in a medium at pH 1.