Polyaniline Solution Research Articles

Fabrication of Low Cost Conducting Papers for Miniaturized Electronic Biomedical Sensors

Paper is an important material in our daily lives. Paper is cheap, environmentally friendly, light, flexible and widespread all over the world. Paper-based sensors are attractive because they are cheap, portable, accessible everywhere, and easily destroyed after being used. Paper-based sensors have been widely used in food safety control, clinical test, and environmental detection. The fiber structure in paper, which can act like a tunnel for microfluidic liquid transport, plays an important role in paper-based sensors by providing a platform for chemical reaction of analytes. However, conventional paper-based biosensors, which usually involve colorimetry, has the limitation in sensitivity and detection limit. Besides, the quantitative analysis of optical signals usually requires expensive optical detection system. In sharp contrast, most electronic sensors can be fabricated in very low cost and display with a simple device. In our study, we present a novel idea, which turns regular paper into conductive by combining paper and conducting polymer together. By integrating this conducting paper with different sensor technologies, various sensors can be achieved with high sensitivity and accuracy, which can be attributed to the great biocompatibility of the conducting paper. Only small amount of sample is required for testing with these sensors. Because of the simple structural design and fabrication, the conducting paper can be fabricated as a cheap, efficient, and portable electronic biosensor. Previous research has shown the HRP-modified n-alkylated polyaniline (PANI) can detect hydrogen peroxide in buffer solution with a very high sensitivity, ultra-low detection limit, and very short response time. During fabrication, the PANI thin film may sometime suffer from cracks after baking the PANI layer on the silicon nitride substrate due to different thermal expansion coefficients between PANI and silicon nitride. By using a filter paper as the substitute for hard substrate, the mechanical stress of PANI after baking can be largely reduced. Figure 1 shows the schematic of the conducting paper. Propane sultone was doped in PANI. The PANI solution was then dropped on the filter paper and silver electrode is then coated on the back of the paper to contact with the PANI, extending to the front side, making it easy for probing. The current was measured from 0-1V. Figure 2 shows the current-voltage characteristics of the conducting paper. Figure 3(a) shows that the PANI layer is tightly merged with the filter paper Figure 3(b) shows the surface morphology of PANI on the paper. In summary, the conducting paper made of PANi can not only achieve electronic paper-based devices, but can also realized electronic paper-based biosensors which can provide better sensitivity and lower cost, compared to the conventional paper-based sensors. Combining it with different technologies and enzymes, it can be used to detect several kinds of analytes. The portability and flexibility of conducting paper also make it more convenient to use. Because the fabrication process is quite simple and cheap, it can be widely promoted commercially in the future. This work was partially supported by National Science Council grant (No.99B20495A & 101-2221-E-007-102-MY3) and by the research grant (100N2049E1) at National Tsing Hua University.

Enhanced thermal stability under DC electrical conductivity retention and visible light activity of Ag/TiO₂@polyaniline nanocomposite film.

The development of organic-inorganic photoactive materials has resulted in significant advancements in heterogeneous visible light photocatalysis. This paper reports the synthesis of visible light-active Ag/TiO2@Pani nanocomposite film via a simple biogenic-chemical route. Electrically conducting Ag/TiO2@Pani nanocomposites were prepared by incorporating Ag/TiO2 in N-methyl-2-pyrrolidone solution of polyaniline (Pani), followed by the preparation of Ag/TiO2@Pani nanocomposite film using solution casting technique. The synthesized Ag/TiO2@Pani nanocomposite was confirmed by UV-visible spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Ag/TiO2@Pani nanocomposite film showed superior activity towards the photodegradation of methylene blue under visible light compared to Pani film, even after repeated use. Studies on the thermoelectrical behavior by DC electrical conductivity retention under cyclic aging techniques showed that the Ag/TiO2@Pani nanocomposite film possessed a high combination of electrical conductivity and thermal stability. Because of its better thermoelectric performance and photodegradation properties, such materials might be a suitable advancement in the field of smart materials in near future.

Facile in-situ preparation of polyaniline/graphene nanocomposites using methanesulfonic acid

Polyaniline (PANI)/graphene composites were prepared by the in-situ polymerization of aniline in a 1 M aqueous solution of methanesulfonic acid (MSA) containing graphene, which was prepared separately from graphite powders by simple sonication in MSA. Graphite powders spontaneously exfoliated to form graphene (GPM), which was then quenched with excess water, filtered, and dried to produce powders. The dried graphene powders produced were re-dispersed well in a 1 M MSA aqueous solution, in which the in-situ polymerization of aniline was performed. The resulting PANI/GPM composite had a conducting emeraldine salt (ES) form, and showed good electrical and thermal properties, compared to pure PANI prepared using a 1 M HCl solution. The PANI/GPM composite could be dissolved in a MSA solution and spin-coated in a conducting ES form of PANI. In contrast, the ES form produced from a HCl solution was insoluble in organic solvents and needed to be reduced to convert it to the emeraldine base form to produce a PANI solution. Therefore, the in-situ preparation of PANI/graphene composites using MSA provides a facile means of improving the thermal and electrical properties of PANI and its processability.

Rapid Fabrication of Nanomaterial Electrodes Using Digitally Controlled Electrokinetics

We present here a new process for fabricating polymeric electrodes based on a composite solution of conductive polyaniline (PANI) particles and multiwalled carbon nanotubes (MWCNTs) using an optically induced electrokinetics (OEK) chip. Based on this method:1) polymeric electrodes with different geometric sizes can be fabricated within 1-3 min by projecting digitally generated images into an OEK chip; 2) polymeric electrodes with different electrical conductivities can be fabricated from composite solutions with different MWCNT concentrations; and 3) fabricated polymeric electrodes are used to assemble MWCNTs sensing elements via dielectrophoresis (DEP) and used for detecting ethanol. The electrical conductivity of these nanomaterial-based polymeric electrodes and the DEP-assembled sensor is analyzed before, during, and after exposure to ethanol. In summary, digitally controlled electrokinetics is demonstrated to be a novel method for rapidly fabricating polymeric sensing electrodes.

Inkjet Printed Negative Supercapacitors: Synthesis of Polyaniline‐Based Inks, Doping Agent Effect, and Advanced Electronic Devices Applications

Low frequency negative supercapacitors and high frequency negative capacitors are realized developing a polyaniline (PANI) based ink for piezoelectric inkjet printers, water based. PANI is synthesized by oxidation polymerization starting from the aniline dimer, thus avoiding the use of a toxic/mutagen substance such as aniline. In order to work in aqueous phase, the reverse addition of the dimer in the oxidative solution is made. The chlorinated emeraldine salt of PANI is produced and emeraldine base is prepared by dedoping. Two different doped PANI solutions are produced by solubilization of the emeraldine salt in dimethylsulphoxide and addition of respectively trifluorosulfonic acid and camporsulfonic acid, and then used as inks for the fabrication of inkjet‐printed tracks of different geometries. The properties of inkjet‐printed devices are characterized both in DC and AC regimes, showing very good performances under specific measurement conditions in terms of conductivity, as well as extremely interesting phenomena whose origin is still under debate, such as low frequency negative supercapacitance, high frequency negative capacitance and negative resistance. The realization of the highest negative supercapacitance realized so far, of –2.3 mF @ 30 Hz, corresponding to a specific mass capacity of –799 F g−1, is reported.

Nanostructured polyaniline rice husk composite as adsorption materials synthesized by different methods

Composites based on polyaniline (PANi) and rice husk (RH) were prepared by two methods: the first one was chemical method by combining RH contained in acid medium and aniline using ammonium persulfate as an oxidation agent and the second one was that of soaking RH into PANi solution. The presence of PANi combined with RH to form nanocomposite was clearly demonstrated by infrared (IR) spectra as well as by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Lead(II) and cadmium(II) ion concentrations in solution before and after adsorption process on those composites were analysed by atomic adsorption spectroscopy. Of the above preparation methods, the soaking one provided a composite onto which the maximum adsorption capacity was higher for lead(II) ion (200 mg g−1), but lower for cadmium(II) ion (106.383 mg g−1) in comparison with the chemical one. However, their adsorption process occurring on both composites also fitted well into the Langmuir isotherm model.

Novel vertical spinning preparation of free-standing carbon nanotube–polyaniline composite films with high electrical conductivity

A novel vertical spinning (VS) process is reported for fabricating free-standing carbon nanotube (CNT)–polyaniline (PANI) composite films with high electrical conductivity (EC). In the VS process, a high centrifugal force is exerted on the PANI solution containing CNTs to achieve a uniform dispersion of CNTs in the composites; meanwhile, the high aspect ratio of CNTs is greatly maintained to a high degree (75%). These contribute to the high EC of the CNT–PANI films since the EC benefits from both the good dispersion and the high aspect ratio of CNTs. The EC of the as-prepared composite film with the 10 wt% CNTs has a value above 150 S cm−1, which is much higher than that at the same CNT content reported previously in the literature. For the purpose of comparison, the CNT–PANI composite films were prepared via the commonly used plane casting process. Moreover, the sandwich-structured PANI–CNT–PANI composite films were synthesized via the VS process to illustrate another advantage of this process in manipulating the distribution of fillers in the composites. The CNT–PANI composite films prepared by the VS process show the highest EC. The sandwiched structure shows a reasonably high conductivity and a relatively low percolation threshold among the three composite films.

Construction of PANI–cellulose composite fibers with good antistatic properties

Novel polyaniline (PANI)/cellulose filament fibers were spun from hydrophobic PANI and hydrophilic cellulose complex solution dissolved in aqueous solution containing 7 wt% NaOH/ 12 wt% urea as solvent by wet-spinning. At low PANI content, the composite fibers realized a transition from an insulator to semiconductor.

Manufacturing Technique and Property Evaluations of Conductive Nonwoven Fabrics

Conductive textiles can be used in diverse fields, such as antistatic materials, sensors, materials for electromagnetic shielding and biomedical. This study produces nonwoven fabrics with polylactic acid (PLA) and polyaniline (PAN) and the resulting PLA/PAN nonwoven fabrics are evaluated with electromagnetic shielding effectiveness (EMSE) and air permeability. Polylactic acid (PLA) and low melting point polylactic acid (LPLA) are made into nonwoven fabrics, which are then spray-coated with different amount of PAN solution to form PLA/PAN nonwoven fabrics. The fabrics are laminated with various numbers of layers, and then thermally pressed. The experiment results show that the PAN amount and lamination number are proportional to the EMSE of the PLA/PAN nonwoven fabrics.

SENSING PROPERTIES OF MNO2-DOPED POLYANILINE/POLY(VINYL ALCOHOL) BLEND

MnO 2-Doped Polyaniline/Poly (Vinyl alcohol) thin films were prepared chemical oxidative polymerization, us ing microwave oven technique on glass substrate. These thin films prep ared by using Analytical Reagent grade solutions of Polyaniline, Poly (Vinyl alcohol), MnO 2, primary dopant hydrochloric acid are mixed in stoic hiometric proportion. The solutions were kept in mi crowave for 10 sec then oxides with ammonium peroxydisulphate o xidant, then after kept in water bath to obtain the uniform thin films. Films were dries it in air medium for an hour. The electrical and gas sensing properties of these films were inve stigated. MnO 2, Doped Polyaniline/Poly(Vinyl alcohol) thin films showed better ammonia and trimethyl ammine vapour respons e as compared to undoped Polyaniline / Poly (Vinyl alcohol) thin films. The gas response was observed to be increased with the ir stoichiometric composition of films.

Nanogold/Polyaniline/Penicillin G Nanoconjugates: A Novel Nanomedicine

A novel strategy was developed for one-step synthesis of PANI/gold nanoconjugates to develop new resistant penicillin G molecules. Spherical monodispersed PANI/gold colloids were prepared by a photochemical reaction between aqueous gold chloride solution and acidic polyaniline solution. Functionalized PANI/gold colloids were then grafted to the C3 carboxyl group of the β lactam ring of penicillin in the presence of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDAC) with a conjugation yield of 175 µg mg−1. These novel gold penicillin G nanoconjugates showed a very good growth inhibition against β lactam resistant Staphylococcus aureus (gram positive). This work thus describes a novel strategy for one step synthesis of PANI/gold colloids to develop resistant antibiotic nanoconjugates as novel bactericidal materials.

Electroactive bio-composite actuators based on cellulose acetate nanofibers with specially chopped polyaniline nanoparticles through electrospinning

A dry type electro-active biopolymer actuator was newly developed with electrospun cellulose–polyaniline bio-composite membranes. Through electrospinning with the mixture of cellulose acetate and polyaniline solutions, well-defined cellulose acetate nanofibers reinforced with chopped polyaniline nanoparticles were obtained and extracellular nano-porous bio-composite membranes with a good biocompatibility were fabricated. The electro-active bio-composite actuator based on cellulose acetate nanofibers with specially chopped polyaniline nanoparticles through electrospinning shows much larger electromechanical deformations than a pure cellulose acetate actuator.

Preparation and characterization of a conductive polyaniline/polysulfone film and evaluation of the effect of co-solvent

A novel conductive dense membrane composed of polyaniline (PANI) and polysulfone (PSU) was prepared. To improve the solubility of PANI in N-methyl pyrrolidone (NMP) and consequently increase the conductivity of the eventual film, a tertiary amine (1,3-dimethyl-2-imidazolidinone, DMI) was added to the solvent as a co-solvent. Different PANI solution concentrations in NMP/DMI were used to make blend films via solution blending with PSU solution in NMP in different ratio’s of PANI/PSU. The effect of the PSU fraction on the properties of the membrane has been investigated. The electrical conductivity, doping degree, crystallinity, miscibility of the polymers and shape stability were investigated. It was observed that an increase in the PSU fraction causes a decrease in the conductivity as well as less film deformation after doping. The conductivity and shape stability of the blend film were optimized by a change in PANI concentration in the casting solution and a change in the PSU fraction. The best conductivity was achieved using 3% PANI solution in NMP/DMI and the minimum percentage of PSU, allowing good shape stability after doping, was found to be 40%.

Facile preparation of polyaniline/MnO2 nanofibers and its electrochemical application in the simultaneous determination of catechol, hydroquinone, and resorcinol

In this study, polyaniline/MnO2 nanofibers were synthesized by the simple mixing of aqueous dispersed solution of polyaniline (PANI) nanofibers and KMnO4 aqueous solution. Materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and FT-IR. The electrochemical oxidation of hydroquinone, catechol, and resorcinol was investigated using cyclic and differential pulse voltammetries at PANI/MnO2 modified electrode. PANI/MnO2 exhibited high current sensitivity for these analytes compared to MnO2 and PANI modified electrodes, which is due to the presence of highly dispersed MnO2 in PANI matrix. The performance of this material was demonstrated in the detection of hydroquinone, catechol, and resorcinol in water samples. The reliability and stability of the modified electrode provides a good possibility for applying the technique in routine analysis for a selected class of electroactive organic/bio-molecules.

Electrically conducting nylon 6,6–polyaniline short composite fibres synthesised by the solvent coagulation method

Polyaniline (PANI) was blended with nylon 6,6 in concentrated H2SO4 and HCl solutions. The solvent coagulation method was utilised to extract short composite fibres of a centimetre in length. A solution of n-butyl acetate, acetone, toluene, 1μM HCl and chloroform were used as coagulating bath to extract the fibres. The diameters of the fibres ranged from 200 to 300nm, while the length measured approximately 1cm, as determined from Scanning Electron Microscopy (SEM). The electrical conductivity varied from 10−4 to 10−2 S/cm for different mass fractions of PANI (xPANI) in the composite fibres. The percolation threshold was reached at xPANI values between 0.15 and 0.2, and further addition of PANI resulted in saturation of the conductivity of the composite fibre. To observe the effect of MWCNTs on the electrical conductivity of the nylon–PANI fibres, 0.04g, 0.08g, 0.4g and 0.5g of MWCNTs (1, 2, 10, 12.5 weight percentage, respectively) were added into the nylon–PANI solution and were extracted as fibres in the aforementioned solvents. The electrical conductivity of the short fibres increased by an order of magnitude (0.372 S/cm at 12.5wt.%) when they were extracted in the presence of the MWCNTs. PANI doped in concentrated HCl exhibited an electrical conductivity of 4.46S/cm.

Characterization of solution and solid state properties of polyaniline processed from trifluoroacetic acid

In this work are reported properties of polyaniline processed from trifluoroacetic acid. Films obtained by simple drop casting were smooth and defectless. Features like absorption in range of UV–vis-NIR, mid-IR and electrical conductivity are discussed. The highest electrical conductivity of such films was found equal to 65 S/cm. It was observed a striking feature—successive colour transition from cyan to deep green when the solvent was dried out from the cast film.

Fabrication of solid aluminum electrolytic capacitors utilizing conductive polyaniline solutions

To overcome the risk of electrolyte leakage and the shortcoming of higher impedance at high frequencies for the conventional aluminum electrolytic capacitors impregnated with electrolyte solutions, solid aluminum electrolytic capacitors employing conducting polyaniline (PANI) as a counter electrode were developed. The dodecylbenzenesulfonic acid (DBSA) doped PANI/chloroform solution, camphorsulfonic acid (CSA)–DBSA co-doped PANI/chloroform solution and DBSA doped PANI/toluene solution were synthesized by direct and inverse emulsion polymerization pathway. The capacitors using the solution of CSA–DBSA co-doped PANI/chloroform showed the best electrical properties. The performances of the PANI capacitors can be remarkably improved after secondary doping with m-cresol. The as-fabricated solid capacitors have very low impedances at high frequencies and excellent temperature characteristics as well as long shelf-life. The results can be ascribed to high conductivity and superior thermal stability for the CSA–DBSA co-doped PANI. Our strategy of using conductive PANI solution to fabricate the solid capacitors is not only compatible with the existing fabrication procedure for the conventional capacitor but also suitable for commercial mass production of low cost PANI.

Asymmetric hollow fibre membranes based on ring-substituted polyaniline and investigation towards its gas transport properties

A more soluble polyaniline derivative, i.e. poly(o-anisidine), (POAn), was synthesized in-house for this study by using an ortho substituted aniline monomer. It was observed that the prepared dope solution was more homogeneous with less visible agglomerates as compared to previously prepared polyaniline (PAni) solution. Integrally skinned hollow fibre membranes were successfully prepared by dry-jet wet spinning from POAn with N-methyl-2-pyrrolidone as a solvent and a more volatile tetrahydrofuran as a co-solvent for gas separation. The spinning air-gap lengths were varied to promote the formation of the membrane skin layer. POAn membranes prepared at higher air gap were more orientated with packed structure and good gas separation characteristics. They showed selectivities of O2/N2, CO2/N2, H2/N2 and H2/CO2 of about 13, 89, 370 and 4.2, respectively with permeation rates of H2, CO2 and O2 about 10.4, 2.5 and 0.37×10−6cm3 (STP)/cm2scmHg, respectively. Presence of methoxy group in POAn showed substantial enhancement in gas permeation properties compared to previously developed PAni membranes. The H2/N2 and CO2/N2 selectivities were improved by 3 and 7 times, respectively as compared to PAni membranes. Development of hollow fibre membranes using polyaniline derivative with improved processability and excellent gas separation performance depicts their potential for industrial gas separation applications.

Polyaniline nanofiber humidity sensor prepared by electrospinning

Polyaniline (PANi) nanofiber humidity sensors were prepared by electrospinning (ES) from the N,N-dimethylformamide solution of PANi, poly(vinyl butyral) (PVB) and poly(ethylene oxide) (PEO). Morphologies of the electrospun nanofibers prepared under different ES conditions were observed by scanning electron microscopy. Formation of beads in the nanofibers was found to greatly affect their adhesion to the substrates and the nanostructures. By modulating the composition of ES solution, PANi nanofibers with beads not only showed good adhesion to the electrode and thus good electrical contact, but also maintained relatively high specific surface area. Furthermore, hydrophilicity of the nanofibers was modified by adjusting the ratio of PVB to PEO in the ES solution, which had an effect on their sensing properties. Humidity response of the nanofiber sensors was investigated by measuring their impedance at different humidity levels at room temperature. The nanofiber sensors revealed much higher sensitivity than their film counterparts (impedance changing for three orders of magnitude from 20% to 90%RH). In addition, they were featured with good sensing linearity, fast response ( t 90% of ∼8 s and 6 s for adsorption and desorption, respectively), small hysteresis (∼1%RH) and good repeatability.

Electrical characterization of heterojunction between polyaniline titanium dioxide tetradecyltrimethylammonium bromide and n-silicon

The organic/inorganic semiconductor heterojunction has been fabricated by thin film formed on n-Si semiconductor substrate using spin coating technique from the solution of polyaniline (PANI) titanium dioxide (TiO 2) composite chemically synthesized in the presence of the cationic surfactant, tetradecyltrimethylammonium bromide (TTAB). The thickness of the polymeric film coated on the n-Si substrate has been found to be 110 nm by using the profilometer. The current–voltage ( I– V) characteristics of the PANI TiO 2 TTAB/n-Si heterojunction have been measured in the temperature of 178–238 K. The I– V characteristics of the PANI TiO 2 TTAB/n-Si heterojunction have shown the rectifying behavior. The forward I– V characteristics of the device have been analyzed on the basis of the standard thermionic emission (TE) theory. An abnormal increase in the barrier height and decrease in the ideality factor with increasing temperatures has been shown. This behavior has been interpreted assuming inhomogeneity of barrier formed at the interface. The temperature-dependent I– V characteristics of the PANI TiO 2 TTAB/n-Si heterojunction have revealed a double Gaussian distribution giving mean barrier heights of 0.916 eV and 1.164 eV and standard deviations of 0.114 eV and 0.131 eV, respectively. Furthermore, the PANI TiO 2 TTAB has been characterized by using Fourier Transform Infrared (FTIR), Ultraviolet–visible (UV–vis) spectra and X-ray diffraction analysis (XRD).