Self-doped Polyaniline Research Articles

A glassy carbon electrode modified with a nanocomposite consisting of molybdenum disulfide intercalated into self-doped polyaniline for the detection of bisphenol A

Thin-layered molybdenum disulfide (MoS2) was intercalated, via ultrasonic exfoliation, into self-doped polyaniline (SPAN). This material, when placed on a glassy carbon electrode (GCE), exhibits excellent electrical conductivity and synergistic catalytic activity with respect to the detection of bisphenol A (BPA). The electrochemical response of the modified GCE to BPA was investigated by cyclic voltammetry and differential pulse voltammetry. Under optimal conditions, the oxidation peak current (measured best at 446 mV vs. SCE) is related to the concentration of BPA in the range from 1.0 nM to 1.0 μM, and the detection limit is 0.6 nM.

The effect of material composition of 3-dimensional graphene oxide and self-doped polyaniline nanocomposites on DNA analytical sensitivity

Until now, morphology effects of 2-dimensional or 3-dimensional graphene nanocomposites and the effect of material composition on the biosensors have been rarely reported. In this paper, the various nanocomposites based on graphene oxide and self-doped polyaniline nanofibres for studying the effect of morphology and material composition on DNA sensitivity were directly reported. The isolation and dispersion of graphene oxide were realized via intercalated self-doped polyaniline and ultrasonication, where the ultrasonication prompts the aggregates of graphite oxide to break up and self-doped polyaniline to diffuse into the stacked graphene oxide. Significant electrochemical enhancement has been observed due to the existence of self-doped polyaniline, which bridges the defects for electron transfer and, in the mean time, increases the basal spacing between graphene oxide sheets. Different morphologies can result in different ssDNA surface density, which can further influence the hybridization efficiency. Compared with 2-dimensional graphene oxide, self-doped polyaniline and other morphologies of nanocomposites, 3-dimensional graphene oxide-self-doped polyaniline nanowalls exhibited the highest surface density and hybridization efficiency. Furthermore, the fabricated biosensors presented the broad detection range with the low detection limit due to the specific surface area, a large number of electroactive species, and open accessible space supported by nanowalls.

Photothermal tumor ablation in mice with repeated therapy sessions using NIR-absorbing micellar hydrogels formed in situ

Repeated cancer treatments are common, owing to the aggressive and resistant nature of tumors. This work presents a chitosan (CS) derivative that contains self-doped polyaniline (PANI) side chains, capable of self-assembling to form micelles and then transforming into hydrogels driven by a local change in pH. Analysis results of small-angle X-ray scattering indicate that the sol–gel transition of this CS derivative may provide the mechanical integrity to maintain its spatial stability in the microenvironment of solid tumors. The micelles formed in the CS hydrogel function as nanoscaled heating sources upon exposure to near-infrared light, thereby enabling the selective killing of cancer cells in a light-treated area. Additionally, photothermal efficacy of the micellar hydrogel is evaluated using a tumor-bearing mouse model; hollow gold nanospheres (HGNs) are used for comparison. Given the ability of the micellar hydrogel to provide spatial stability within a solid tumor, which prevents its leakage from the injection site, the therapeutic efficacy of this hydrogel, as a photothermal therapeutic agent for repeated treatments, exceeds that of nanosized HGNs. Results of this study demonstrate that this in situ-formed micellar hydrogel is a highly promising modality for repeated cancer treatments, providing a clinically viable, minimally invasive phototherapeutic option for therapeutic treatment.

Electrocatalytic activity of molybdenum disulfide nanosheets enhanced by self-doped polyaniline for highly sensitive and synergistic determination of adenine and guanine.

Recently, easy, green, and low-cost liquild exfoliation of bulk materials to obtain thin-layered nanostructure significantly emerged. In this work, thin-layered molybdenum disulfide (MoS2) nanosheets were fabricated through intercalation of self-doped polyaniline (SPAN) to layer space of bulk MoS2 by ultrasonic exfoliating method to effectively prevent reaggregation of MoS2 nanosheets. The obtained hybrid showed specific surface area, a large number of electroactive species, and open accessible space, accompanied by rich negative charged and special conjugated structure, which was applied to adopt positively charged guanine and adenine, based on their strong π-π* interactions and electrostatic adsorption. Also, the SPAN-MoS2 interface exhibited the synergistic effect and good electrocatalytic activity compared with the sole SPAN or MoS2 modified electrode.

Self-doped polyaniline/molybdenum oxide composite nanorods for supercapacitors

A composite film of self-doped polyaniline and molybdenum oxide (SPAN/MoOx) shows electroactivity in a wide potential range of 1.4 V from −0.6 to 0.8 V vs. SCE. The symmetric supercapacitor assembled by using SPAN/MoOx as both of the electrodes showed good rate behavior.

A novel water-based epoxy coating using self-doped polyaniline–clay synthesized under supercritical CO2 condition for the protection of carbon steel against corrosion

The synthesis of a polyaniline–clay nanocomposite (PAniC NC) was achieved using the in situ polymerization of aniline in a Cloisite® 30B nanoclay suspension in a supercritical CO2 (Sc-CO2) medium. The interfacial co-polymerization of aniline (ANI) and m-aminobenzenesulfonic acid (SAN) in the presence of Cloisite® 30B was performed in Sc-CO2/water to produce the SPANI-clay NC. The NC was then mixed with a water-based hardener. This water-based composite is developed with the goal of reducing environmental and health risks. The use of this Sc-CO2 technique produced a composite material that resulted in the enhanced protection of carbon steel against corrosion when compared to a similar composite synthesized under atmospheric conditions. The materials obtained were characterized using UV/visible spectroscopy, X-ray powder diffraction and scanning and transmission electron microscopy. The anti-corrosion performance and the adhesion properties of these coatings were evaluated using standardized tests. Electrochemical impedance spectroscopy was also used to determine the electrochemical properties of these anti-corrosion coatings. Better exfoliation and dispersion of the clay was achieved using the Sc-CO2 medium resulting in superior performances in corrosion and electrochemical tests because of the higher level of intercalation.

Construction of a thin-film immunosensor with self-doping polyaniline modified electrode for human serum albumin detection

A competitive immunosensor, based on the indium tin oxide (ITO) electrode coupling a thin film of self-doping polyaniline (SPANI), was fabricated for the detection of human serum albumin (HSA). By properly preparing the aniline doped with o-aminobenzenesulfonic acid, the morphology of the SPANI was shaped into microsphere form. When SPANI coated on the ITO glass surface as the electrode, a high conductivity, high biocompatibility and high stability sensor could be obtained attributed to the high surface area of SPANI microsphere. By coupling HSA in SPANI layer and measuring the differential pulse voltammograms, a competitive immunoassay, capable of HSA concentration determination, was constructed. To enhance the sensitivity of the immunosensor, a secondary antibody conjugated with colloidal gold were also applied. The optimal conditions for the detection were found as follows: the immobilized albumin of 250 μg/mL, the anti-albumin of 20 μg/mL and the secondary antibody conjugated with colloidal gold (CG) of 5 μg/mL. The detection has a linear range from 10 to 200 μg/mL and a detection limit of 1 μg/mL without using CG. In contrast, under the use of CG, the linear range was from 0.5 to 200 μg/mL with a detection limit of 413 ng/mL.

Conductivity of poly(2-methoxyaniline-5-phosphonic acid)/amine complex and its charge dissipation property in electron beam lithography

The present study summarizes the conductivity of the drop-cast film for various amine complexes of the novel self-doped polyanilines bearing phosphonic acid, poly(2-methoxyaniline-5-phosphonic acid) (PMAP) and poly(2-methoxyaniline-5-phosphonic acid monoethyl ester) (PMAPE). The conductivity was revealed to depend on the kind and amount of the amine base. The tendency of PMAP and PMAPE complexes was similar, but the PMAP ones exhibited the higher conductivity than the PMAPE ones. In the case of the pyridine and CF3CH2NH2 complexes of PMAP, the conductivity more than 10Sm−1 was kept even in the presence of four equivalents of the amine based on the phosphonic acid moiety. The charge dissipation property of the PMAP/pyridine (1:2) complex was also investigated qualitatively by top-coating a resist on a quartz substrate in the electron beam lithography. The obtained pattern clearly showed the charge dissipation property. Use of PMAP/{CF3CH2NH2/NH3 (4:1)} (1:3) complex made it possible with the development using only water in place of an aqueous NMe4OH solution.

Characterization of self-doped conducting polyanilines bearing phosphonic acid and phosphonic acid monoester

Novel self-doped polyanilines bearing phosphonic acid, poly(2-methoxyaniline-5-phosphonic acid) (PMAP) and poly(2-methoxyaniline-5-phosphonic acid monoethyl ester) (PMAPE) were characterized in the following properties: (1) thermostability, (2) morphology in the solid state, (3) absorption and transparency in the spin-coating film, (4) delocalization of polaron, (5) doping efficiency, and (6) chemical oxidation and reduction. The UV–vis–NIR absorption spectra of the spin-coating films of PMAP/pyridine (1:2) and PMAPE/pyridine (1:1) show the polaron band and free carrier tail, which are characteristic to the conducting polymers. The highly transparent films of them (up to ∼90% transparency) were formed by spin-coating. Concerning the property of the polaron in the polymer, the ESR spectra suggest that polaron of PMAP/pyridine (1:2) is more delocalized than that of PMAPE/pyridine (1:1). The XPS experiments indicate that the doping efficiency of PMAP is much higher than that of PMAPE, which is likely to be due to diprotic acid units derived from phosphonic acid of PMAP. Oxidation and reduction of PMAP and PMAPE were demonstrated by treatment with the corresponding oxidant {(NH4)2S2O8} and reductant (N2H4·H2O), respectively.

Effect of HAuCl4concentration on electrochemical DNA sensing behaviors of Au/nanoSPAN nanocomposite

Sensing properties of Au nanomaterials are greatly influenced by their morphology, size, and structure. Studying influencing factors to achieve controllable morphology, size and electrochemical properties is profoundly significant for further analytical applications. In this work, various Au micro-nanostructures were fabricated by varying the concentrations of HAuCl4 through a three-step electrodeposition method, in which self-doped polyaniline nanofibers (nanoSPAN) served as a supported matrix to obtain Au/nanoSPAN nanocomposite. The obtained electrodes were characterized by scanning electron microscopy, energy disperse X-ray spectroscopy and cyclic voltammetry (CV). The sulfonic acid groups and the imine units on the surface of nanoSPAN ensured the nucleation and growth of Au micro-nanostructures. Compared with other morphologies, the hierarchical and homogeneously dispersed flower-like Au microspheres (obtained in 5.0 mM HAuCl4 solution) showed high electrochemical activity in a 0.5 M H2SO4 solution and the largest electroactive areas. The next-step DNA sensing results based on various Au/nanoSPAN nanocomposites using methylene blue as electrochemical probe showed that controlling the concentrations of HAuCl4 can influence the amount of immobilized ssDNA and its sensitivity.

Electrocatalytic determination of chloramphenicol based on molybdenum disulfide nanosheets and self-doped polyaniline

In this paper, a novel molybdenum disulfide (MoS2) intercalated by self-doped polyaniline (SPAN) via ultrasonic exfoliating method was prepared to show outstanding conductivity and synergistic electrocatalytic activity using chloramphenicol (CAP) as a case. In the ultrasonic process, due to the strong π–π⁎ stacking interaction and electrostatic repulsion, the negatively charged SPAN served as an intercalator to result in few-layers MoS2 nanosheets, which were exfoliated from bulk MoS2. This nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy and differential pulse voltammetry. The obtained nanocomposite owns large conjugated structure and rich negative charge, which can improve the adsorption of conjugate structured CAP with the detection range from 0.1 to 1000μmolL−1. The results also showed that the electrocatalytic responses were further affected by the mass ratio of SPAN–MoS2 and the ultrasonication time. Our electrocatalytic platform could be further applied in the adsorption and detection of other positively charged biomolecules or aromatic molecules.

Pyrroloquinoline Quinone-Dependent Enzymatic Bioanode: Incorporation of the Substituted Polyaniline Conducting Polymer as a Mediator

One of the main technological issues with enzymatic biofuel cells and biosensors is improving the electron transfer between the enzyme and the current collector to improve current densities. In this study, we show the use of a conducting polymer to mediate pyrroloquinoline quinone-dependent enzymatic bioelectrocatalysis. A self-doped polyaniline (PANi) film is electropolymerized on a Toray carbon paper electrode surface to covalently bond enzymes to this three-dimensional interface. Sulfonic acid groups are introduced into the PANi backbone structure to increase the polymer conductivity at neutral pH via a self-doping process, and the carboxyl groups can be activated to covalently bond to enzymes. The electropolymerization of 2-methoxyaniline-5-sulfonic acid and 3-aminobenzoic acid is optimized with respect to the rate of the bioelectrocatalytic conversion of enzyme substrates. Comparing this PANi conducting copolymer enzyme immobilization technique with the hydrophobically modified Nafion encapsulation-based enzyme immobilization method showed a 9.8-fold increase in current density.

Electrocatalytic activities of Nafion/CdSe/Self-doped polyaniline composites to dopamine, uric acid, and ascorbic acid

Composites of Nafion, COOH-capped CdSe, and self-doped polyaniline (SPAN) were used to prepare novel chemical modified glassy carbon electrodes (Nafion/CdSe/SPAN/GCE). The electrocatalytic activities of the modified GCE to the redox reactions of dopamine (DA), uric acid (UA), and ascorbic acid (AA) were investigated by cyclic voltammetry (CV). CV curves revealed that the electrocatalytic activities of Nafion/CdSe/SPAN/GCE to oxidations of the analytes in solution of pH 7 were in the order of DA > UA > AA. This order was consistent with the strong-to-low extent of interactions between the modified GCE and the analytes. These interactions were consistent with the observations that the oxidation rate of DA followed a diffusion-controlled process whereas that of UA followed a surface adsorption-controlled process. The composites of casting at higher pH levels were found to exhibit better CdSe and SPAN dispersions in films and higher electrocatalytic activities. CdSe and SPAN exhibited insignificant synergistic effects on the oxidations of DA when cast from Nafion solutions of both low and high pHs whereas CdSe and SPAN exhibited much synergistic effects on the oxidations of UA when cast from the Nafion solution of high pH at 12.

Fabrication of Low-Fouling Ultrafiltration Membranes Using a Hydrophilic, Self-Doping Polyaniline Additive

A simple, scalable method for fabricating fouling-resistant ultrafiltration membranes is described. A self-doped, sulfonated form of polyaniline was blended into polysulfone (PSf) ultrafiltration (UF) membranes to enhance hydrophilicity and fouling resistance. Polyaniline in its base form was sulfonated with fuming sulfuric acid, yielding sulfonated polyaniline (SPANi) with a degree of sulfonation of ∼0.5 confirmed by XPS. The SPANi polymer was dedoped and dissolved in a solution of polysulfone in N-methylpyrollidone at varying concentrations. During phase inversion to form membranes, SPANi is redoped and precipitated within the PSf membrane films in a facile one-step process. Composite membranes containing increasing amounts of SPANi were compared to the pure PSf membranes to determine changes in performance, hydrophilicity, and antifouling characteristics. The composite membranes exhibit fluxes similar to those of the pure PSf membrane and maintain rejection properties similar to those of current UF mem...

Apparent electrocatalytic activities of composites of self-doped polyaniline, chitosan, and carbon nanotubes

Composites of self-doped polyaniline (SPAN), chitosan (CS), and carbon nanotubes (CNT) (or COOH-functionalized CNT, denoted by fCNT) were cast on glassy carbon electrodes (GCE) via different casting procedures for investigations on their apparent electrocatalytic activities in buffer solutions of pH 2, 7, and 11 using the Fe(CN)63-/4- redox couple as a probe by cyclic voltammetry (CV). CV curves revealed that the cast CS–CNT and CS–fCNT composites both exhibited apparent electrocatalytic activities to the reactions of the probe at pH 2 and 7. The SPAN was found to exhibit synergistic effects with (f)CNT on the apparent electrocatalytic activity, with CNT exhibiting higher synergism than fCNT. SPAN in the outer layer of the SPAN/CS–(f)CNT/GCE exhibited more enhanced apparent electrocatalytic activity than that in the inner layer of the CS–(f)CNT/SPAN/GCE or that being mixed in the CS–(f)CNT–SPAN/GCE. At pH 7, the layered SPAN/CS–CNT/GCE and CS–CNT/SPAN/GCE that exhibited fairly high apparent electrocatalytic activities to the redox reactions of the probe exhibited also high apparent electrocatalytic activities to the oxidation reactions of dopamine (DA) and uric acid (UA) and were suitable for their detections. The layered SPAN/CS–fCNT/GCE and CS–fCNT/SPAN/GCE, and the non-layered CS–(f)CNT–SPAN/GCE exhibited low anodic peak current densities and were not suitable for the detections of both analytes.

Platinum nanoparticle/self-doping polyaniline composite-based counter electrodes for dye-sensitized solar cells

In this study, we developed a series of platinum nanoparticle (PtNP)/self-doping polyaniline (SPANI) composite-based counter electrodes for dye-sensitized solar cells (DSSCs). The SPANIs with nanospherical (S-SPANI) and nanotube (T-SPANI) structures were respectively self-assembled on the indium–tin oxide glass substrate via the in situ oxidation polymerization. The S-SPANI and T-SPANI were prepared by the copolymerization of self-doping monomer o-aminobenzenesulfonic acid and aniline in different molar ratios. The PtNP/SPANI composite-based counter electrodes were further prepared through the reduction of Pt ions on the SPANI layer using reduction agents of formic acid and sodium borohydride (NaBH4). The SPANI can serve as the proposed supports to disperse PtNPs. The particles sizes of formic acid-reduced nano-platinum (F-PtNPs; 5–15 nm) were smaller than those of the NaBH4-reduced nano-platinum (S-PtNPs; 15–25 nm). Moreover, the distribution of F-PtNPs on the surface of SPANIs was more uniform than that of the S-PtNPs on the surface of SPANIs. The effects of SPANI morphology and PtNP size/distribution on the electro-chemical behavior and photovoltaic performance of these PtNPs/SPANI counter electrodes-based DSSCs were studied. The highest short-circuit current density (14.87 mA cm−2), fill factor (64.2 %), and photoenergy conversion efficiency (4.77 %) were obtained for the DSSC based on the F-PtNP/S-SPANI counter electrode.

Large-area, three-dimensional interconnected graphene oxide intercalated with self-doped polyaniline nanofibers as a free-standing electrocatalytic platform for adenine and guanine.

In this work, we prepared large-area, three-dimensional interconnected graphene oxide (GNO) intercalated by self-doped polyaniline nanofibers (SPAN, a copolymer of aniline and m-aminobenzenesulfonic acid) through a simple adsorption and intercalation route via sonication of the mixed dispersions of both components. The strong π-π* stacking between the backbones of SPAN and the GNO basal planes, and the electrostatic repulsion between the negatively charged SPAN and graphene oxide sheets yield a unique free-standing, three-dimensional interconnected nanostructure. The nanocomposite possesses a large specific surface area and maintains a homogenous and stable dispersion with SPAN, which endows it with a high conductivity and good electrocatalytic activity. Because the negative charge and specific structure of the nanocomposite can prompt the adsorption of positively charged guanine and adenine via strong π-π* interactions or electrostatic adsorption, the hybrid was adopted as an excellent sensing platform for highly sensitive determination of guanine and adenine. The electrocatalytic platform exhibited some advantages, such as high sensitivity, good reproducibility and long-term stability.

Conjugated self-doped polyaniline–DNA hybrid as trigger for highly sensitive reagentless and electrochemical self-signal amplifying DNA hybridization sensing

In very recent years, polyaniline or its derivatives have been adopted to efficiently immobilize probe DNA via π-π interaction between conjugated interface and DNA bases. In this work, self-doped polyaniline (SPAN)-DNA hybrid was adopted as the platform to construct a DNA biosensor with label-free, reagentless and electrochemical self-signal amplifying features. This was achieved by the π-π interaction between conjugated SPAN and DNA bases, also the intrinsic differences between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The tightly cross-linked hybrid was tethered to Au electrode, which had been anchored by p-aminothiophenol (PATP) self-assembled monolayer (SAM) previously, based on the phosphoramidate bond between PATP and ssDNA. SPAN in the recognition surface exhibited well-defined redox signals under neutral conditions. Due to the intrinsic property differences between ssDNA and dsDNA, such as rigidity, π-stacked bases, charge distribution and long-range electron transfer, SPAN-DNA underwent a major conformational change after hybridization. The redox behaviors of SPAN were modulated by DNA, which served as signals to monitor hybridization. As an example, the gene fragment related to one of the screening genes for the genetically modified plants, cauliflower mosaic virus 35S gene was satisfactorily detected with this strategy. Under optimal conditions, the dynamic range for the DNA assay was from 1.0 × 10(-14) mol L(-1) to 1.0 × 10(-8) mol L(-1) with the detection limit of 2.3 × 10(-15) mol L(-1). This work presents the construction of a recognition surface for the highly-sensitive electrochemical DNA hybridization detection via the self-signal amplifying procedure of conjugated SPAN-DNA hybrid. Unlike most signal amplifying processes using outer indicators, complex labels or other reagents, this procedure possesses simplicity and convenience.

Preparation of polyaniline and self-doped polyaniline–clay nanocomposites in supercritical CO2: Synthesis and conductivity study

Supercritical CO2 (ScCO2) was used as processing medium to prepare polyaniline (PANI) and self-doped polyaniline (SPANI)–clay nanocomposites. Interfacial copolymerization of aniline (ANI) and m-aminobenzene sulfonic acid (SAN) in the presence of Cloisite 30B nano-clay powder was performed in ScCO2/water to produce PANI and SPANI–clay nanocomposites. Different ratio of aniline to SAN was used and the temperature profile during copolymerization was measured to monitor the copolymerization process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and UV–vis spectroscopy were used to characterize the morphology and the structure of the resultant nanocomposites. SEM and TEM results reveal that nano-clays are fully dispersed in the ScCO2 synthesized nanocomposites, while in the atmospheric synthesize ones the nano-clays have tightly bonded agglomerated and are still stack to each others. FTIR and UV–vis results revealed that the products are in high conductive emeraldine salt state. The influences of clay loading on the conductivity of resulting nanocomposites were studied. It was found that the conductivity of nanocomposites is slightly lower than pristine polymers and decreases by nano-clay loading. Conductivity of compressed pellets of pristine PANI and SPANI were measured during the storage for different periods of times to evaluate aging properties. It was found that resulted SPANI has stable conductivity compare to the PANI nanocomposite.

Investigation of deep-level defects in conductive polymer on n-type 4H- and 6H-silicon carbide substrates using I-V and deep level transient spectroscopy techniques

The current-voltage (I–V) characteristics of Au/sulfonated polyaniline (SPAN)/n-SiC heterojunctions have been investigated in detail over a wide range of temperatures between 20 and 440 K. The measured I–V characteristics of all devices show a good rectification behavior at all temperatures. The room temperature rectification ratios (forward to reverse currents ratio, IF/IR) at 0.6 V for SPAN/n-type 4H-SiC and SPAN/n-type 6H-SiC heterojunctions are 2 × 104 and 7 × 106, respectively. The value of rectification of SPAN/6H-SiC heterojunction is four orders of magnitutude higher than the state-of-the art sulfonated polyaniline thin films deposited on n-type silicon substrates. A self-assembly technique and copolymerization were used to fabricate a self-doped polyaniline films on SiC substrates. The experimental I–V data were analysed using the Werner model, which includes the series resistance of the heterojunctions. The diode parameters such as the ideality factor and the barrier height are determined from the experimental data using I–V analysis method. The effect of the temperature on these parameters is presented. Deep level transient spectroscopy (DLTS) and Laplace DLTS techniques were used to investigate the electrically active defects present in these heterostructure devices.