Polyaniline Layer Research Articles

Electrochemical Aptasensor with Layer‐by‐layer Deposited Polyaniline for Aflatoxin M1 Voltammetric Determination

AbstractMycotoxins are highly toxic metabolites of some fungi that frequently contaminate water, food and feed and hence cause several human and animal diseases. In this work, a new approach to the fast and reliable determination of aflatoxin M1 (AFM1) in water and milk has been proposed with reagent free protocol of signal measurement. For this purpose, DNA aptamer selective to AFM1 was entrapped between two thin layers of polyaniline (PANI) electrodeposited on glassy carbon electrode. The incubation of the aptasensor in the AFM1 solution results in remarkable decrease of the PANI intrinsic activity monitored by direct current voltammetry or electrochemical impedance spectroscopy. Appropriate calibration curves were linear in the range from 3 to 90 ng/L with limit of detection (LOD) 1–5 ng/L depending on the measurement mode. Mechanism of signal generation involves shielding electrostatic interactions between the PANI and aptamer in the surface layer and variation of its redox activity attributed to the emeraldine form of PANI. Selectivity of the response was proved by similar experiments with aflatoxin B1 and ochratoxin A and by comparison of the results with those obtained with non‐specific aptamer in the sensing layer. Simple protocol for milk pretreatment has been proposed for reliable detection of AFM1 on the level of its threshold limited values (20 ng/L).

PANI-Encapsulated Si Nanocomposites with a Chemical Bond Linkage in the Interface Exhibiting Higher Electrochemical Stability as Anode Materials for Lithium-Ion Batteries

A covalent linkage between polyaniline (PANI) and Si nanoparticles in PANI-encapsulated Si nanocomposites was proposed and achieved by a facile and economical synthetic strategy, in which NH2-grafted Si was first obtained via a chemical modification of Si surface and the polymerization of aniline initiated at NH2 group surface was readily accomplished to get PANI shell. The characterizations suggested that NH2 groups were successfully introduced onto Si surface and PANI-encapsulated Si nanocomposites with a core/shell structure were fabricated. Electrochemical tests showed that our proposed Si nanocomposites delivered a high initial specific capacity of 2135[Formula: see text]mAh/g and retained 848[Formula: see text]mAh/g after 100 charge/discharge cycles at a current density of 0.1[Formula: see text]A/g, which were superior than that of the normal PANI-encapsulated Si nanocomposites with the absence of chemical bonds in the interface. The enhanced electrochemical performance was ascribed to the surface chemical modification and the introduction of chemical bond in the interface. NH2 group function of Si could improve the homogeneity of encapsulated PANI shell. Additionally, PANI was tightly anchored to Si nanoparticles via a covalent bond between silicon and PANI, which would greatly inhibit the separation of PANI from Si surface during the expansion/contraction of Si particles. Thus, the structural integrity was maintained. Besides, PANI layer with a unique structure promoted the transport of both electrons and lithium ions.

Polyaniline immobilized on polycaprolactam nanofibers as a sorbent in electrochemically controlled solid-phase microextraction coupled with HPLC for the determination of angiotensin II receptor antagonists in human blood plasma.

In this research, electrospun polycaprolactam nanofibers were collected on a fine stainless steel mesh sheet without a binder, and a layer of conductive polyaniline was chemically deposited on the nanofibers. The polyaniline immobilized on the polycaprolactam nanofibers provided high electrical conductivity, acceptable mechanical stability, and a large surface area. This assembly was then used as a working electrode in electrochemically controlled solid-phase microextraction (EC-SPME), a fast and environmentally friendly method. The polymer layers were characterized by SEM and FTIR techniques. Significant factors affecting the EC-SPME efficiency were investigated, including the desorption conditions, the sorbent used, the pH of the sample solution, the extraction voltage, the extraction time, and the ionic strength. Under the optimum conditions, the limits of detection and quantification for the target analytes were 0.9-1.8μgL-1 and 3.0-6.1μgL-1, respectively. The linear dynamic range was 5-2000μgL-1, with R2 > 0.993. The method was coupled with HPLC analysis and applied to the determination of angiotensin ΙΙ receptor antagonists (ARA-ΙΙs) in human plasma, and relative recoveries of 91.1-104.3% with RSDs of ≤8.3% were obtained.

Study of redox and protonation processes of polyaniline by the differential multiwavelength Raman spectroelectrochemistry.

Polyaniline layer has been deposited at a gold electrode and subjected to differential multiwavelength Raman spectroelectrochemical study. A broad set of laser line excitation wavelengths was used, including UV (325 nm), blue (442 nm), green (532 nm), red (633 nm), and far red (785 nm). From measurements performed, potential-difference Raman spectra, related to small-step changes of electrode potential were derived, and specific spectral and structural features were obtained and analysed. Similarly, pH-difference spectra for solution pH changes were obtained. A strong resonance enhancement of Raman spectra for reduced form of polyaniline at UV and blue line excitations, and for oxidized forms at red and far red excitations was observed and analysed. The 442-nm excited potential-difference resonance Raman spectra revealed presence of intermediate oxidation state compound formed during the electrooxidation of leucoemeraldine with characteristic vibrational bands at 1622, 1187, 881, and 817 cm-1.

Further explore on the behaviors of IR electrochromism of a double layer constructed by proton acid-doped polyaniline film and ITO layer

In this study, the IR electrochromic films were constructed by dodecylbenzene sulfonate acid (DBSA)-doped polyaniline (PANI) film and an indium tin oxide glass (ITO). We used the in situ electrochemical deposition method for preparing the DBSA-doped PANI. The IR electrochromic properties of the double layer structure have been investigated minutely. We discovered two operation modes of modulation IR emissivity of the double layer structure with the increase of thickness of the PANI layer. When the thickness of the PANI film was within a certain range, its switching between leucoemeraldine (LB) and emeraldine salt (ES) modulated IR transmittance of the PANI film to realize regulation of the IR emissivity of the double layer structure (Mode Ⅰ). When the thickness of the PANI film reached a certain value, its IR transmittance was lower, the IR emissivity modulation of the double layer structure was determined mainly by the IR reflectance of the PANI film which depended on the pseudo-metallic behavior of the PANI film (Mode Ⅱ).

Enhanced electromagnetic interference shielding capability in bamboo fiber@polyaniline composites through microwave reflection cavity design

Natural, electrical insulating bamboo fiber (BBF) was selected as cost-effective frameworks to fabricate electromagnetic interference (EMI) shielding composites. The compacted polyaniline (PANI) layer was formed on the surface of BBF through an in-situ polymerization process. The formation of the continuous PANI layer was attributed to the interaction between the aniline monomers and BBF surface. Three-dimensional electromagnetic reflection cavities were facilely constructed by this unique architecture. The electromagnetic properties are extensively investigated with respect to electrical conductivity, complex permittivity and permeability, loss tangent, and Cole-Cole analysis. By manipulating the mass ratio of BBF with different size, BBF@PANI possessed a high electrical conductivity of 8.99 ± 0.43 S/cm. Combined with the results of skin depth, attenuation constant, also comparisons of experimental results and theoretical predictions, it was found that besides the conductivity and dielectric loss, the compacted microwave reflection cavity could also boost the EMI shielding effectiveness (SE). By introducing effective multiple reflections, the absorption ability was enhanced. The EMI SE could even reach 45.0 dB with only 0.4 mm thickness. The attenuation of microwave was predominantly governed by an absorption mechanism. Furthermore, the SE per unit thickness could be as high as 1125.0 dB/cm, which is much higher than those other types of PANI-based materials. With outstanding EMI shielding performance, these BBF@PANI heterostructures offer promising prospects of lightweight, cost-effective and excellent performance EMI shields. We firmly believe that this research will be an effective platform for the development of green electromagnetic attenuators in the future.

Bi2MoO6 Microsphere with Double-Polyaniline Layers toward Ultrastable Lithium Energy Storage by Reinforced Structure.

Given its competitive theoretical capacity, Bi2MoO6 is deemed as a promising anode material for the realization of efficient Li storage. Considering the severe capacity attenuation caused by the lithiation-induced expansion, it is essential to introduce effective modification. Remarkably, in this work, Bi2MoO6 microsphere with double-layered spherical shells are successfully prepared, and the polyaniline are coated on both inner and outer surfaces of double-layered spherical shells, working as buffer layers to strain the volume expansion during electrochemical cycling. Inspiringly, when utilized as anode in LIBs, the specific capacity of Bi2MoO6@PANI is maintained at 656.3 mAh g-1 after 200 cycles at 100 mA g-1, corresponding to a high capacity of 82%. However, the counterpart of individual Bi2MoO6 is only 36%. This result confirms that the polyaniline layer can dramatically promote stable cycling performances. Supported by in situ EIS and ex situ technologies followed by detailed analysis, the enhanced pseudocapacitance-dominated contributions and electron/ion transfer rate, benefiting from the combination with polyaniline, are further proved. This work confirms the significant effect of polyaniline on the ultrastable energy storage, further providing an in-depth sight on the impacts of polyaniline coating to the electrical conductivity as well as the resistances of electron/ion transport.

Polyphenylene sulfide (PPS) fibrous felt coated with conductive polyaniline via in situ polymerization for smart high temperature bag-filter

Polyphenylene sulfide (PPS) is a semi-crystalline polymer with high performance, such as heat-resistance, chemicals resistance etc. The PPS fibers are widely applied in bag-filters to remove dust for end gas of industrial coal-fired plants. The deteriorated and broken PPS bag-filter was hard to detect in a device consisting of hundreds of bags. In this research, a conductive polymer, polyaniline (PANI) was in situ polymerized and deposited on the surface of PPS fibers. The loading content of PANI were affected by dropping speed of initiator, ammonium persulfate (APS) solution and slower dropping speed resulted in higher loading rate. The morphologies and properties of resulting PPS/PANI felt were characterized by means of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), tensile tester and Keithley 6487. The PPS fiber was coated on about 1.3 μm thickness of PANI, and the PPS/PANI felt has higher breaking force and elongation at break than those of pristine PPS one after ageing for 8 h at 200 °C, which the PPS/PANI composite fiber would show longer service life. PANI layer also offered the fiber conductivity, which would be used as a pressure sensor for PPS bag-filter when running.

Core-shell structured NaTi2(PO4)3@polyaniline as an efficient electrode material for electrochemical energy storage

Sodium-ion batteries are widely suggested as next-generation electrochemical energy storage devices for various applications due to the abundance of sodium resource and environmental friendliness. Advanced anode materials with outstanding Na+ storage performances are crucial for sodium storage. Herein, core-shell NaTi2(PO4)3@polyaniline is synthesized by using a simple sol-gel route and a self-assembly process. In this material, the NaTi2(PO4)3 crystals are uniformly coated by the polyaniline layer. Such polyaniline is benefit to enhance the electronic conductivity and promote the Na+ diffusion of NaTi2(PO4)3 anode. The NaTi2(PO4)3@polyaniline presents the reversible capacities of 128.8 and 115.6 mAh g−1 at 0.1 and 5 C, and it also presents a high capacity retention of 96.9% after 200 cycles at 10 C. The results demonstrate that this new approach can be used to improve other anodes for electrochemical energy conversion and storage.

Novel approach to the synthesis of polyaniline possessing electroactivity at neutral pH

A new approach is proposed for the synthesis of polyaniline via electrochemical polymerization of aniline at a very low concentration on a modified electrode surface. The electrode was modified with a sulfonated polyaniline, poly(2-methoxy aniline-5-sulfonic acid) (PMAS), which acted as an electroactive conductive template for the aniline monomer. The electrode surface was modified with PMAS via a number of different methods including cyclic voltammetric and potentiostatic deposition as well as dip and drop casting water-soluble PMAS onto the electrode surface. Electrochemical polymerization of aniline was then carried out at the surface of the modified electrode. Effect of different variables such as PMAS concentration, volume and pretreatment of the modified electrode on the polymerization of aniline was studied. The polymer synthesized at the PMAS modified electrode was characterized by electrochemical and UV–vis spectrophotometic techniques. Electrochemical studies showed that even at very low concentration of aniline (5.0 mM), an adherent, uniform and stable polyaniline film was deposited on the electrode surface. Without any further treatment, this polyaniline layer was found to be electroactive at a neutral pH which is crucial for biosensing applications.

Polyvinylpyrrolidone-Induced Uniform Surface-Conductive Polymer Coating Endows Ni-Rich LiNi0.8Co0.1Mn0.1O2 with Enhanced Cyclability for Lithium-Ion Batteries.

The Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode has attracted great interest owing to its low cost, high capacity, and energy density. Nevertheless, rapid capacity fading is a critical problem because of direct contact of NCM811 with electrolytes and hence restrains its wide applications. To prevent the direct contact, the surface inert layer coating becomes a feasible strategy to tackle this problem. However, to achieve a homogeneous surface coating is very challenging. Considering the bonding effect between NCM811, polyvinylpyrrolidone (PVP), and polyaniline (PANI), in this work, we use PVP as an inductive agent to controllably coat a uniform conductive PANI layer on NCM811 (NCM811@PANI-PVP). The coated PANI layer not only serves as a rapid channel for electron conduction, but also prohibits direct contact of the electrode with the electrolyte to effectively hinder side reaction. NCM811@PANI-PVP thus exhibits excellent cyclability (88.7% after 100 cycles at 200 mA g-1) and great rate performance (152 mA h g-1 at 1000 mA g-1). In situ X-ray diffraction and in situ Raman are performed to investigate the charge-discharge mechanism and the cyclability of NCM811@PANI-PVP upon electrochemical reaction. This surfactant-modulated surface uniform coating strategy offers a new modification approach to stabilize Ni-rich cathode materials for lithium-ion batteries.

Facile Synthesis of Textile-Based Filter for Industrial Wastewater Treatment

In this study, cotton and polyester textile fabrics have been treated with polyaniline layer to use as smart filter for industrial wastewater treatment. The developed filters were effective to anchor the dissolved dye wastewater molecules. The polymerization of polyaniline chains on textile fabrics was assured by microscopic techniques. Also, the electrical resistance of treated samples was significantly reduced recording 20 and 40 kΩ for cotton and polyester-PANI filter respectively. The textile-based filter was tuned to be selective to negative dye molecules dissolved in water. The mass ratio of dissolved dyes was varied with developed filter and achieved 45% removal efficiency. The developed textile-based filter was characterized using various spectroscopic and microscopic techniques. The concentration of waste dyes molecules before and after treatments was determined and efficiency of filter was evaluated.

Characterization and thermal conductivity investigation of Copper-Polyaniline Nano composite synthesized by gamma radiolysis method

In this study, Copper-Polyaniline nanocomposite (Cu-PAni) has been synthesized by gamma radiolysis as a novel method and was confirmed by different analytical techniques such as Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD). The copper nanoparticle completely covered by a layer of polyaniline with different thickness. The particle mean size was determined from XRD by using the Debye-Scherrer’s formula and the particle size was found to be 21 nm. The thermal conductivity of the nanofluid has been measured at different nanofluids volume fractions of 0.2%, 0.4%, 0.6%, 0.8% and 1.0%. The effect of nanofluid temperature on the nanofluid properties is measured in the range from 10 °C to 90 °C. The thermal conductivity ratio of the Copper-Polyaniline nanocomposites water nanofluid increases 107% at nanofluid temperature of 10 °C and 159% at 90 °C for a volume fraction of 1.0%. The Cu-PAni nanocomposite is a potential material for thermal conductivity enhancement of water based nanofluid.

All Solid-State Poly (Vinyl Chloride) Membrane Potentiometric Sensor Integrated with Nano-Beads Imprinted Polymers for Sensitive and Rapid Detection of Bispyribac Herbicide as Organic Pollutant.

All-solid-state potentiometric sensors were prepared by using polyaniline (PANI) as the solid contact material. A film of PANI (thickness approximately being 0.25 µm) was deposited on a solid substrate (carbon screen printed platform). The PANI layer was subsequently coated with an ion-selective membrane (ISM) containing uniform-sized molecularly imprinted nanoparticles to produce a solid-contact ion-selective electrode (SC/ISE) for bispyribac herbicide (sensor I). In addition, aliquat 336 was also used as an ion exchanger in plasticized PVC membrane (sensor II). The proposed sensors revealed a remarkably improved sensitivity towards bispyribac ions with anionic slopes of −47.8 ± 1.1 (r2 = 0.9995) and −44.4 ± 1.4 (r2 = 0.9997) mV/decade over a linear range 1.0 × 10−2–8.6 × 10−6 M, 1.0 × 10−2–9.0 × 10−6 M and detection limits of 1.33 and 1.81 µg/mL for sensors I and II, respectively.Selectivity of both sensors is significantly high for different common pesticides and inorganic anions. The potential stability of the SC/ISEs was studied using chronopotentiometry. Electrochemical impedance spectrometry was used to understand the charge-transfer mechanisms of the different types of ion-selective electrodes studied. The impedance response of the electrodes was modelled by using equivalent electrical circuits. The sensors were used for a direct measurement of the bispyribac content in commercial herbicide formulations and soil samples collected from agricultural lands planted with rice and sprayed with bispyribac herbicide. The results agree fairly well with data obtained using HPLC method.

Rod‐Like Sb2MoO6: Structure Evolution and Sodium Storage for Sodium‐Ion Batteries

AbstractBimetallic oxides of different metal species and well‐defined nanostructure could lead to a new generation of polymetallic oxide in the energy storage field. Exceptional 1D nanostructured materials are favorable in the electronic transmission of the kinetic processes and confinement effects of electronic structures deriving from the nanoscale dimensions. In this work, an Sb2MoO6 nanorod is successfully prepared for the first time through a facile metathesis reaction process. Then, a thin polyaniline (PANI) layer is coated via the in situ oxidative polymerization of aniline. The Sb2MoO6‐based nanorods are first utilized as anode material for sodium‐ion batteries (SIBs). Benefiting from the synergistic effect of PANI coating and 1D nanostructure, the Sb2MoO6@PANI nanorod electrode presents enhanced sodium storage performances, and a reversible specific capacity of 370.2 mAh g−1 can be retained after 100 cycles. Ex situ electrochemical impedance spectra (EIS) and transmission electron microscopy (TEM) are used to study the evolution process, demonstrating that the PANI coating can alleviate the pulverization of the rod structure and reflect better cycle stability. This work reveals the sodium storage activity of novel Sb2MoO6 nanorods and proposes an efficient strategy to promote its electrochemical properties; it is in great favor of extending the development of anode materials for SIBs.

Performance enhancement of ACF anode for electro-catalytic oxidation of phenol via dual coating of polyaniline and TiO2

In this paper, highly efficient activated carbon fiber (ACF) anode was prepared for the electro-catalytic oxidation of phenol. The ACF was firstly coated with TiO2 via ship-in-a-bottle synthesis, and then loaded with polyaniline (PANI) layer by an in situ polymerization. The TiO2 coating would improve electro-catalysis activity of ACF anode and the PANI coating would enhance its conductivity, transferring more electrons for electro-catalysis process. The cyclic voltammetry (CV) results of ACF, TiO2/ACF, PANI/ACF and PANI/TiO2/ACF anodes implied that the dual coating could not only inhibit the generation of non-conductive polyphenol film on PANI/ACF anode (anti-passivation), but also obviously increase the phenol degradation efficiency of TiO2/ACF anode. The results of OH output and phenol removal rate showed that the working performance and stability of dual-coated ACF anode could be optimized through altering the modification amount of PANI and TiO2. The new mechanism of synergistic electrocatalysis of PANI/TiO2/ACF for phenol oxidative degradation was reported. The experimental results could offer a novel method to prepare highly efficient porous carbon anodic materials.

Enhanced ammonia sensitive properties and mechanism research of PANI modified with hydroxylated single-walled nanotubes

Abstract A kind of NH3 gas sensors based on hydroxylated single-walled carbon nanotubes (SWCNTs-OH)/polyaniline (PANI) composites were fabricated by a simple in-situ chemical oxidative polymerization method. The microstructure characterization showed uniform PANI layer wrapped around the external walls of the SWCNTs-OH bundles, and the thickness of the PANI layer decreases with increasing of SWCNTs-OH content in composites. The FTIR and Raman analysis suggested that the presence of hydroxyl groups on SWCNTs-OH further enhanced the interaction between SWCNTs-OH and PANI via hydrogen bonding. The test results toward NH3 showed that response values of all SWCNTs-OH/PANI composites based sensors were higher than that of PANI. It could be attributed to the formation of a more massive conjugated structure due to the hydrogen-bonds between SWCNTs-OH and PANI, which enhanced spatial delocalization of p–type carrier holes in the composites, thus increased probability of NH3 molecules interacted with protons in SWCNTs-OH/PANI composites. However, the response values didn't increase all the time with increasing of SWCNTs-OH content in composites, and the SWCNTs-OH/PANI composites with 15 mg SWCNTs-OH based sensor exhibited the maximum response value when compared to the others. Its response value was about 50.03 times than that of the pure PANI based one at 800 ppm concentrations of NH3. It might be related to a balance between the number of active sites and the density of pores in composites, which both associated with the thickness of the wrapped PANI layer.

Electrochemical DNA Sensors with Layered Polyaniline-DNA Coating for Detection of Specific DNA Interactions.

A DNA sensor has been proposed on the platform of glassy carbon electrode modified with native DNA implemented between two electropolymerized layers of polyaniline. The surface layer was assembled by consecutive stages of potentiodynamic electrolysis, DNA drop casting, and second electrolysis, which was required for capsulation of the DNA molecules and prevented their leaching into the solution. Surface layer assembling was controlled by cyclic voltammetry, electrochemical impedance spectroscopy, atomic force, and scanning electron microscopy. For doxorubicin measurement, the DNA sensor was first incubated in the Methylene blue solution that amplified signal due to DNA intercalation and competition with the doxorubicin molecules for the DNA binding sites. The charge transfer resistance of the inner layer interface decreased with the doxorubicin concentration in the range from 1.0 pM to 0.1 μM (LOD 0.6 pM). The DNA sensor was tested for the analysis of spiked artificial urine samples and showed satisfactory recovery in concentration range of 0.05–10 μM. The DNA sensor developed can find application in testing of antitumor drugs and some other DNA damaging factors.

Monocrystal Cu3Mo2O9 Confined in Polyaniline Protective Layer: an Effective Strategy for Promoting Lithium Storage Stability

AbstractAttributed to the high theoretical capacity and abundant reserve, Cu3Mo2O9 has been considered as a potential anode material for lithium‐ion batteries. Nevertheless, the severe capacity fading caused by structure collapse and particle aggregation seriously hinders its practical application. In this work, Cu3Mo2O9 coated with homogeneous polyaniline layer is obtained through oxidative polymerization of aniline on the surface of Cu3Mo2O9. The lithium storage performance is investigated systematically. As a result, a high reversible specific capacity of 800.2 mA h g−1 at a current density of 100 mA g−1 is delivered in Cu3Mo2O9@PANI anode even after 200 cycles, which is much higher than that of pristine Cu3Mo2O9 anode (373.8 mA h g−1). Furthermore, a high capacity of 675 mA h g−1 at a high current density of 1 A g−1 is achieved even after 700 cycles. This result evidences that the introduction of a polyaniline protective layer is an effective way to improve the structural stability of the Cu3Mo2O9 anode and further enhance cycling durability. This strategy is a starting point for the preparation and stabilization of other binary metal oxide composite materials for applications in lithium‐ion batteries.

Red and NIR laser line excited Raman spectroscopy of polyaniline in electrochemical system

Polyaniline has been electrodeposited at a gold electrode, and subjected to Raman spectroelectrochemical study at a red (633 nm) and NIR (785 nm) laser line excitations at electrode potentials varying from −0.5 V to 0.8 V, and different solution pH values ranging from 1 to 9. The results obtained are compared with 532 nm excitation spectra. Some new phenomena have been observed and discussed. The 1620 cm−1 Raman band diminishes in its intensity with a positive potential shift at a green excitation, whereas a maximum of intensity for this band around 0.6 V was observed for the red excitation. Adversely, a positive potential shift causes an increase of intensity for 1585 cm−1 band for both these excitation wavelengths. For NIR excitation, both these bands grow in intensity by positive potential shift. This behavior, as well as increase of spectral intensity with a progressive oxidation of polyaniline layer, were interpreted based on the differences of optical absorption and its changes with changing electrode potential. For the most Raman bands, the shift of the onset potential for their intensity growth to less positive values has been observed by increasing of solution pH.