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Abstract

The change in resistance of polyaniline on exposure to aqueous ammonia has been utilized for the study of a prototype chemical sensor. This paper discusses various aspects of polyaniline and its suitability as a chemical sensor, particularly with reference to aqueous ammonia solution.

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... [5,[6][7][8][9][10][11] . ‫ميكانيك‬ ‫التحسس‬ ‫ية‬ [3,5,[6][7][8][9][10][11] ‫بالشكل‬ ‫موضحة‬ ‫األتي:‬ ...
... . ‫ميكانيك‬ ‫التحسس‬ ‫ية‬ [3,5,[6][7][8][9][10][11] ‫بالشكل‬ ‫موضحة‬ ‫األتي:‬ ...
Article
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Polyaniline organic Semiconductor polymer thin films have been prepared by oxidative polymerization at room temperature, this polymer was deposited on glass substrate with thickness 900nm, FTIR spectra was tested , the structural,optical and electrical properties were studied through XRD ,UV-Vis ,IR measurements ,the results was appeared that polymer thin film sensing to NH3 gas.
... Electronically conducting polymers (ECPs) characterized by their low cost, high specific capacitances, generally fast charge-discharge processes and high conductivities in their charged states, are promising materials for the realization of high specific energy/power performance pseudocapacitors. An advantageous characteristic of ECPs over carbon based electrodes is that charging takes place not only at the interface as is the case with carbon materials but through the whole mass of the active electrode film during doping-dedoping processes resulting in huge specific capacitance [13][14][15]. Ideal double layer capacitance behaviour of an electrode material expresses itself in form of a rectangular shape in a cyclic voltammetric curve. The sign of current is instantaneously reversed upon reversal of the potential sweep. ...
... Oxidative pre-treatment of graphitic carbon was undertaken to functionalise the graphite. This was done following a protocol adopted from literature [15][16][17] in which 5.0 g of graphitic carbon was weighed and sonicated for 7 h in a mixture of 150 mL conc. HNO 3 and 50 mL conc. ...
Article
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Nanostructured poly(4-styrene sulphonic acid) and tantalum (IV) oxide-doped polyaniline nanocompos-ite were synthesised and their electro-conductive properties were determined. The oxide was synthesized using a modified sol-gel method and then dispersed in acidic media through sonication and entrapped in-situ into the polymeric matrix during the oxidative chemical polymerization of aniline doped with poly(4-styrene sulphonic acid). The oxides and novel polymeric nanocomposite were characterised with TEM, SEM, EDX, XRD, FTIR, UV-visible to ascertain elemental and phase composition, successful polymer-ization, doping, morphology and entrapment of the metal oxide nanoparticles. The electro-conductivity of the nanomaterial was interrogated using scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). The material was then anchored on activated graphitic carbon and used in the design of an asymmetric supercapacitor cell using 6 M KOH aqueous electrolyte. Characteristically high specific capacitance values of 318.4 F/g with a corresponding energy and power densities of 1.57 kWh/kg and 0.435 kW/kg, respectively, were demonstrated. The cell also showed high coulombic efficiency of 94.9% with a long cycle life and good cycle stability making the nanomaterial suitable for constructing supercapacitor cell electrodes.
... [5,[6][7][8][9][10][11] . ‫ميكانيك‬ ‫التحسس‬ ‫ية‬ [3,5,[6][7][8][9][10][11] ‫بالشكل‬ ‫موضحة‬ ‫األتي:‬ ...
... . ‫ميكانيك‬ ‫التحسس‬ ‫ية‬ [3,5,[6][7][8][9][10][11] ‫بالشكل‬ ‫موضحة‬ ‫األتي:‬ ...
Article
Polyaniline organic Semiconductor polymer thin films have been prepared by oxidative polymerization at room temperature, this polymer was deposited on glass substrate with thickness 900nm, FTIR spectra was tested , the structural,optical and electrical properties were studied through XRD ,UV-Vis ,IR measurements ,the results was appeared that polymer thin film sensing to NH3 gas.
... Over the time period, with the development of nanostructures, considerable improvement in ammonia sensor fabrication has taken place with respect to sensitivity, response and recovery [23]- [26]. The formation of morphological hierarchies of polyaniline and interaction of polyaniline with other materials in composites was found to be a major factor for obtaining a tunable sensor response [27]. ...
... The redoping of the polyaniline chain with the available H + ions therefore restores the original level of the resistance. Thus, deprotonation and reprotonation of polyaniline in the presence and absence of ammonia gas, explains the sensitivity and reversibility of polyaniline based sensor for ammonia [25], [27]. ...
Article
This paper reports the wide range ammonia sensing behavior of biopolymer polyaniline composite. The agarose-guar gum-polyaniline (A-G-PANI) composite films were prepared by the in situ synthesis of polyaniline in the biopolymeric matrix. The polyaniline biocomposite exhibits an interpenetrated network structure as confirmed by field emission scanning electron microscopy. The synthesized polyaniline biopolymer composite shows an excellent ammonia sensing behavior over a wide range of 10-90 000 ppm (9%). The sensor shows high performance in terms of sensitivity factor (R-gas/R-air) ranging from 1.07 to 34.95 in the entire concentration range. The response time and recovery time of the sensor varies from 2 to 5 min and 5 to 25 min, respectively, with respect to the increase in the concentration of gas. The sensor shows selective response against H2S, ethanol, methanol, and acetone. The enhanced performance of the sensor is attributed to the presence of large number of sites provided by the interpenetrated network structure of polyaniline biocomposite. The electrical circuit model for A-G-PANI is constructed using the electrical impedance spectroscopy, and a probable mechanism is proposed for detection over a wide range.
... Polyaniline (PANI) has the potential to meet those requirements and has long been studied as an ammonia-gas-sensing material due to its unique doping/dedoping chemistry and good environmental stability [13][14][15]. In addition, PANI is a stable electrical conductor at room temperature, which is advantageous for reducing sensor power consumption and improving portability. ...
Article
Full-text available
A novel NH3 gas sensor is introduced, employing polyaniline (PANI) with a unique structure called a graft film. The preparation method was simple: polydopamine (PD) was coated on a flexible polyethylene terephthalate (PET) film and PANI graft chains were grown on its surface. This distinctive three-layer sensor showed a response value of 12 for 50 ppm NH3 in a dry atmosphere at 50 °C. This value surpasses those of previously reported sensors using structurally controlled PANI films. Additionally, it is on par with sensors that combine PANI with metal oxide semiconductors or carbon materials, the high sensitivity of which have been reported. To confirm our film’s potential as a flexible sensor, the effect of bending on the its characteristics was investigated. This revealed that although bending decreased the response value, it had no effect on the response time or recovery. This indicated that the sensor film itself was not broken by bending and had sufficient mechanical strength.
... PANI also has antibacterial characteristics i.e., it can kill Gram-positive or Gram-negative bacteria [28,29]. Due to these characteristics, it is widely used in medical and industrial fields [27,30,31]. ...
... Filem LB berasaskan polimer konduksi banyak digunakan dalam biopengesan seperti dalam pengesan ion, pengesan optik dan sebagai peralatan elektronik molekul (Alam et al. 2022). Sifatnya yang unik seperti mempunyai kestabilan dalam proses redoks kimia, mempunyai muatan kapasiti yang tinggi, mempunyai kestabilan terhadap suhu persekitaran dan mempunyai sifat elektrokimia yang baik telah menjana kepada aplikasi polimer yang lebih berkesan (Dhawan et al. 1997). ...
Article
Full-text available
The conducting polymer family is widely used in the field of polymer-based sensors. Among the polymers that are often used are polyaniline (PANI), polypyrrole (PPY) and polythiophene (PT). Sensors operate based on the production of signals by analyte molecules which then produce measurements either qualitatively or quantitatively. In addition, the use of conducting polymers in the field of biosensing has highlighted its importance, especially in the fields of biomedicine, environment, food quality control and more. Even so, there are issues that often arise such as controlling and producing signals of the materials used. Appropriate materials and methods also need to be studied. Therefore, this study was conducted to examine the conductivity effect of the deposition of Polythiophene / Polypyrrole / Polyaniline (PPY/ PT/PANI) on Indium Tin Oxide (ITO) Glass. Polyaniline monolayer (PANI) was deposited on the surface of indium tin oxide (ITO) glass using the Langmuir Blodgett (LB) technique. The monolayer surface of PANI particles has been coated with a layer of polypyrrole (PPY) and polythiophene (PT). PPY and PT were dissolved in methanol and then added with p-toluene sulfonic acid (PTSA) to give the same effect as PANI, especially on their back chain structure. The UV-Vis and FTIR spectra prove the existence of peaks resulting from the solubility and doping process against PPY and PT. It was found that the uneven size of the polymer molecules results from the PPY / PANI image because there is a probability that the existing PPY clumps with each other. When PT was applied to the PPY / PANI layer, a combination of the three polymers formed a cavity on the surface of the PT / PPY / PANI layer. It was explained by the analysis of FTIR PT / PPY / PANI which exhibits the existence of bonds between the combined polymers. The material resistance decreases when the three polymers were combined which explains the higher conductivity value obtained.
... Filem LB berasaskan polimer konduksi banyak digunakan dalam biopengesan seperti dalam pengesan ion, pengesan optik dan sebagai peralatan elektronik molekul (Alam et al. 2022). Sifatnya yang unik seperti mempunyai kestabilan dalam proses redoks kimia, mempunyai muatan kapasiti yang tinggi, mempunyai kestabilan terhadap suhu persekitaran dan mempunyai sifat elektrokimia yang baik telah menjana kepada aplikasi polimer yang lebih berkesan (Dhawan et al. 1997). ...
Article
Full-text available
ABSTRAK Keluarga polimer konduksi banyak digunakan dalam bidang pengesan berasaskan polimer. Di antara polimer yang sering digunakan adalah polianilina (PANI), polipirol (PPY) dan politiofena (PT). Pengesan beroperasi berdasarkan penghasilan isyarat oleh molekul analit yang kemudiannya menghasilkan pengukuran sama ada secara kualitatif dan kuantitatif. Selain itu, kegunaan polimer konduksi dalam bidang biopengesan telah menyerlahkan kepentingannya terutamanya dalam bidang bioperubatan, persekitaran, kawalan mutu makanan dan banyak lagi. Walaupun begitu, terdapat isu yang sering timbul seperti dalam mengawal dan menghasilkan isyarat bahan yang digunakan. Malah, bahan dan kaedah yang sesuai juga perlu dikaji. Maka, kajian ini dilakukan untuk mengkaji kesan kekonduksian pengenapan Politiofena / Polipirol /Polianilina (PPY/ PT/PANI) di Atas Kaca Indium Timah Oksida (ITO). Monolapisan polianilina (PANI) dienapkan di atas permukaan kaca indium timah oksida (ITO) menggunakan kaedah Langmuir blodget (LB). Permukaan monolapisan zarah PANI telah dilapisi dengan lapisan polipirol (PPY) dan politiofena (PT). PPY dan PT dilarutkan dalam metanol terlebih dahulu dan kemudiannya ditambah dengan asid p-toluena sulfonik (PTSA) bagi memberi kesan yang sama seperti PANI terutama pada struktur rantai belakangnya. Spektrum UV-Vis dan FTIR membuktikan kewujudan puncak yang terhasil daripada proses keterlarutan dan pendopan terhadap PPY dan PT. Didapati saiz molekul polimer yang tidak sekata terhasil daripada imej PPY/PANI kerana terdapat kebarangkalian lebihan PPY yang sedia ada bergumpal sesama sendiri. Apabila PT dienapkan ke atas lapisan PPY/ PANI, gabungan ketiga-ketiga polimer telah membentuk rongga di atas permukaan lapisan PT/PPY/ PANI. Ia dijelaskan dengan analisis FTIR PT/PPY/PANI yang mempamerkan kewujudan ikatan antara polimer gabungan tersebut. Rintangan bahan semakin berkurang apabila ketiga-tiga polimer digabungkan bersama yang menjelaskan nilai kekonduksian yang diperolehi semakin tinggi. ABSTRACT The conducting polymer family is widely used in the field of polymer-based sensors. Among the polymers that are often used are polyaniline (PANI), polypyrrole (PPY) and polythiophene (PT). Sensors operate based on the production of signals by analyte molecules which then produce measurements either qualitatively or quantitatively. In addition, the use of conducting polymers in the field of biosensing has highlighted its importance, especially in the fields of biomedicine, environment, food quality control and more. Even so, there are issues that often arise such as controlling and producing signals of the materials used. Appropriate materials and methods also need to be studied. Therefore, this study was conducted to examine the conductivity effect of the deposition of Polythiophene / Polypyrrole / Polyaniline (PPY/ PT/PANI) on Indium Tin Oxide (ITO) Glass. Polyaniline monolayer (PANI) was deposited on the surface of indium tin oxide (ITO) glass using the Langmuir Blodgett (LB) technique. The monolayer surface of PANI particles has been coated with a layer of polypyrrole (PPY) and polythiophene (PT). PPY and PT were dissolved in methanol and then added with p-toluene sulfonic acid (PTSA) to give the same effect as PANI, especially on their back chain structure. The UV-Vis and FTIR spectra prove the existence of peaks resulting from the solubility and doping process against PPY and PT. It was found that the uneven size of the polymer molecules results from the PPY / PANI image because there is a probability that the existing PPY clumps with each other.
... As their characteristic states are readily interconvertible under external stimuli, PANIs can be applied in advanced materials, including sensing devices and electrochemical catalysts. [13][14][15][16] For understanding the structure-property relationship of PANIs and/or their precise chemical modication, structurally well-dened monodisperse oligoanilines with various end functional groups have also been developed. 10,[17][18][19][20][21][22] The replacement of the benzene ring with larger moieties affects their properties. ...
Article
Full-text available
Polyaniline, which is formed by the oxidative polymerization of aniline, is a widely explored conducting polymer with several stable oxidation states, and can be applied in advanced materials, including sensing devices and electrochemical catalysts. The marriage of polyanilines with the diverse chemistry of porphyrins is expected to confer new properties, including a combination of electrical, optical, magnetic and chemical properties. Herein, we demonstrate that meso-aminodiarylporphyrin, a porphyrin analogue of aniline, undergoes oxidative oligomerization in an acidic solution under an oxygen atmosphere to yield stable oligomeric products that are analogous to fully oxidized polyanilines. The so-formed oligomers are composed of the same number of electron-rich porphyrinoid and electron-deficient quinoid moieties, and they exhibit a broad electronic absorption band in the near infrared (NIR) region, which is attributable to intramolecular charge transfer (ICT) transition from electron-rich porphyrinoid moieties to electron-deficient quinoid ones. The quinoid moieties in the oligomers could be reversibly reduced using sodium ascorbate to obtain all-porphyrinoid oligomers that resemble fully reduced polyanilines. The fully reduced oligomers do not exhibit the NIR ICT band. Furthermore, three types of partially reduced tetramers consisting of a single quinoid moiety were also obtained, among which two interconverted in solution. Their interconversion was significantly accelerated in the presence of a protic solvent. This result is consistent with the high electron conductivity of partially oxidized polyanilines following their protonation.
... Furthermore, considering the monitoring system has to work currently or intermittently for all year long, cost effective and environment-friendly are also essential elements of this system in terms of popularization and application. The poisonous agents added by such methods when testing ammonia concentration are difficult to recycle and reuse leading to another challenge to deal with the effluent disposal [13,14]. ...
Article
Full-text available
The realization of accurate and continuous detecting of dissolved ammonia was of great essential in developing smart aquaculture. The appealing properties of electrochemical sensors for ammonia provided a great technical potential in wrestling with these challenges. In this study, self-supported NiC2O4/PANI nanocomposite was successfully fabricated on nickel foam via a two-step in-situ method and employed as a sensitive electrochemical dissolved ammonia sensor. The 3D structure PANI provided fast electronic channel between NiC2O4 nanoparticles and largely reduce the internal resistance. With the help of the specific reaction of nickel oxalate with ammonia, the proposed self-supported NiC2O4/PANI electrode showed remarkable sensitivity of 41 mA µM−1 cm−2 and low detection limit of 0.83 µM. Moreover, the anti-interference ability, reusability reproducibility and stability of this sensor was investigated and exhibited decent performance. The obtained results indicated that the NiC2O4/PANI electrode was of great potential in detection of dissolved ammonia and exhibited a broad applicability for practical application.
... At higher concentration of ammonia, all the protonated sites are deprotonated completely exhibiting visual color change. Thus, deprotonation and reprotonation of polyaniline in the presence and absence of ammonia gas explain the sensitivity and reversibility of polyaniline-based sensor for ammonia (Chatterjee et al. 2013;Dhawan et al. 1997). The NH 3 -sensing response could also be attributed to the crystal structural changes of PANI after doping with HCl. ...
Article
Polyaniline–betel nut fiber (PANI/BNF) filaments have been prepared for the first time by in situ polymerization with potential application as ammonia gas sensor at room temperature. A sheath of polyaniline is formed surrounding the BNF filament, which is evident from scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. This morphological structure makes it easy enough to fit the filaments directly between electrodes for resistive ammonia gas sensor studies without the need of any other polymeric matrix, indicating novelty of the work. A red shift with increase in the amount of BNF is observed in the UV–Vis spectra. The composite exhibits increased electrical conductivity as revealed by electrochemical impedance spectroscopy (EIS), which is a requisite for resistive gas sensors. The novel PANI/BNF sensor has average ammonia-sensing response of 28.2% toward 100 ppm of ammonia with 10 ppm detection limit. The sensor fits in a linear plot of response vs. NH3 concentration from 10 to 200 ppm with good response and recovery capabilities. PANI/BNF filaments with increased conductivity, thermal stability, and ammonia-sensing properties open new scope for their application in gadgets like electrodes for supercapacitors, other gas sensors, and electromagnetic shields.
... 45 In addition to the secondary doping effect of acrylic acid, an additional site (COO -) free for conduction was induced while reacting with ammonia in the polymeric chains and consequently the conductivity. 60,61 The sensitivity of AA-PANI samples was studied over a wide range of concentrations of ammonia vapours from 1 to 600 ppm. The ∆R/R showed a linear increase up to a concentration of 58 ppm followed by saturation [ Figure 6A]. ...
Preprint
Full-text available
Monitoring the concentration of gases and volatile compounds in the environment has significant impact on sustainable human development due to global industrialization. Gas sensors are being employed since 1970's for detecting noxious gases, gas leakages, and also for observing humidity and atmospheric composition. The approach of designing miniature and portable gas/vapour sensors exhibiting rapid response and reversibility together with selectivity and sensitivity has been highly demanding. Similarly, development in the area of nanotechnology has encouraged the scientists to fabricate nanosensors. Sensor devices have been made from classical semiconductors, solid electrolytes, insulators, metals etc. However, the development of conducting polymer-based sensors has unfolded a new dimension in sensing by enabling the wide scope towards the detection of chemical/water vapours and toxic gases even in complex environment. Whereas, the metal oxide-based sensors were observed to be efficient towards the detection of toxic gases. The present review provides a concise account of our work on conducting polymers and metal-based sensors for the detection of ammonia, alcohol, chloroform, humidity, toxic gases etc. Additionally, the paper also demonstrates the challenges and future prospects of conducting polymer sensors to pave their way for enhancing their sensing efficacy.
... [12][13][14][15][16] Polyaniline (PANI) is the most attractive polymer among all the conjugated polymers owing to its controllable levels of doping, and it has been using for a broad range of industrial applications, such as sensors, anticorrosion coating, tissue engineering, and reduction of toxicity in water. [17][18][19][20][21][22][23] Carbon nanotubes offer a larger aspect ratio, high surface area per mass, lower density (*1.3 g ml À1 ) with exceptional mechanical, thermal, electrical, and optical properties, 24,25 which would make them an ideal additive to impart these multifunctional properties to polymers. The single-walled carbon nanotube (SWCNT) aerogels are the three-dimensional networks, consisting of interpenetrating pores, which are an active network for fabricating nanoporous polymer nanocomposite scaffolds. ...
Article
Full-text available
Hydrogel of single-walled carbon nanotubes and polyaniline has been used for thermopower engineering applications due to desirable thermal, electrical, and mechanical properties as well as tunable degradability. In this article, we fabricated nanoporous composite scaffolds from hydrogel of single-walled carbon nanotubes and polyaniline polymer using a standard in situ polymerization process. Our solution-based fabrication method prevented single-walled carbon nanotube aggregation which resulted in enhancing thermal, electrical, and mechanical properties with keeping optimum flexibility in the porous composite scaffold. We compared the mechanical, electrical, and thermal properties of nanoporous composites with different single-walled carbon nanotube loadings. The porous composite scaffold with a 25 wt% showed higher electrical conductivity, ultimate tensile strength, and tensile modulus. Lastly, our solution fabrication method prevents aggregation single-walled carbon nanotube and could help to build the thermoelectrical materials for flexible electronic applications.
... Synergistic and complementary properties of the composite materials based on conducting polyaniline (PANI) and graphene oxide (GO) with regard to their potential applications in sensors [1], adsorbents, supercapacitors [2], alcohol dehydration [3][4][5] and others [6][7][8] somehow have attracted much attention. PANI endures high specific capacitance, high specific flexibility, low cost, own a wide range of electrical properties controlled by the doping levels [9], ease of synthesis and environmental stability. However, the structures and properties of PANI have to deal with the synthesis conditions because of the complexities in molecular structure. ...
Article
Full-text available
Polyaniline/graphene oxide (PANI/GO) composites at different wt% of GO were prepared via solution method. PANI was mixed with the GO synthesized from the improved Hummer’s method. The formation of GO was confirmed via Raman and C/O ratio. Based on the FT-IR, XRD and SEM results, it confirmed the presence of both PANI and GO characteristics at 10.9°, 25.8° and 27.8° and interactions between PANI and GO particles in PANI/GO composites at different GO loading. SEM micrographs showed a folding and wrinkled surface of GO due to the defect upon oxidation process. This means that the weak π–π interactions or the agglomeration of GO have caused PANI unable to attach on the large conjugated basal planes of GO sheets. The defective domains made GO as an insulator as it contained distortions and oxygen-containing functional groups and their local decoration. Low-conductivity domain had conquered most of the GO region which later reduced the pathway of the current flow; therefore, conductivity is affected. The wrinkled structure also resulted in the low conductivity as it weakens the interfacial interaction between PANI and GO and thus disrupted the electron movement in the composites. Due to this, the electrical conductivity reached up to 1.83 × 10−10 S/cm as the GO loading increased to 50 wt%.
... The electrical control on these materials opens a big area of research in the field of condensed matter. Also, conducting polymers (CPs) are a new class of functional materials and they have received great attention in various fields due to their excellent properties [1][2][3][4]. CPs is semiconducting in nature and has low conductivity. To improve their conductivity, composite of CPs have been intensively studied to facilitate their application in various fields. ...
... Polyaniline is a very attracting polymer for its diversifying structures and potential applications [1][2][3][4][5][6][7][8][9] in an electrochromic display, Schottky diodes, corrosion inhibitors, supercapacitors, rechargeable batteries. The basic structure of polyaniline (PAN) is shown in Fig. 1 [10,11]. ...
Article
Composite thin films of polyaniline (PAN)/ZnO are synthesized via electropolymerization (ECP) process in acidic medium on ITO (working electrode) with platinum mesh as a counter electrode and Ag/AgCl as a reference electrode. Acidic medium helps in polymerization and enhances the crystallinity of PAN. PAN films that are obtained in the presence of sulfuric acid give partial crystallinity in its high conducting form, i.e., emeraldine salt. Inorganic metal oxide–organic polymer thin film was used to get a new type of composite nanostructures. The cyclic voltammetry and chronoamperometric properties were investigated by potentiostat for different doping percentages of ZnO with a constant Molar concentration of PAN. Current conduction properties are found to be increased in the presence of ZnO particles. Optical properties were investigated using UV–Vis and photoluminescence spectroscopy. Photoluminescence shows emission in the blue, green and yellow regions. Band gap variation has also been calculated with the help of Tauc’s plot which found to be decreasing with the increase of doping percentage of ZnO.
... The discovery of intrinsically conducting polymers like polyacetylene, polyaniline, polypyrrole, polythiophene, polyindole, etc. have emerged as a active materials lead to a wide range of applications [1][2][3][4]. The useful properties of these polymers are tunable by adding inorganic nanoparticles to them [5]. ...
Article
Full-text available
Polythiophene (PTh) and cobalt nanoparticles (Co-nps) were prepared by chemical oxidation and modified polyol processes respectively. Composites were made by mixing them in the proportions, PTh1-xCox; x = 0.1, 0.2, 0.3, 0.4, 0.5. Morphology of the samples was studied by SEM technique. Dielectric properties with temperature and frequency as variables were investigated. Dielectric constant and loss factor decreased with frequency and increased with temperature. AC conductivity was estimated from the dielectric data. Ac conductivity decreased with increase of Co-nps in the composites which indicates that electrically insulating effect has been induced by Co-nps. Small polaron hopping mechanism is found to be the conduction mechanism operated. Activation energy for ac conduction decreased with increase of frequency and weight percent of Co-nps in the composites. Electric modulus was determined and its analysis leads to the estimation of dielectric relaxation time. Relaxation time decreased with increase of temperature for all the five composites. For the first time PTh-Co nanocomposites have been reported for dielectric properties and ac conductivity as a function of frequency and temperature. © 2018, Iran University of Science and Technology. All rights reserved.
... The widely researched CPs in gas sensing are polythiophene and its derivatives [332,333], polypyrrole [334], polyaniline and composites [335,336]. In addition, several CP based composite gas sensors, for example, composite of alkoxy substituted tetra-phenyl-porphyrin polymer composite films were developed to detect ammonia vapor via polypyrrole impregnated filter paper and polyaniline, respectively [337,338]. ...
Article
Food quality and safety has been a great public concern all over the globe and reliable sensors or monitoring systems has become a prerequisite to affirm quality of various food commodities, especially highly perishable foods, such as seafood, pork, beef, lamb and chicken. Food freshness chemosensors is an emerging sensing technology in the field of food industrial research and development. Although the application of chemosensors is evidently on the move and concurrently lacking commercial viability, it has tremendous potential to empower onsite monitoring of food quality and safety in the food processing industry. This review aims to (a) elaborate different classes of CPs and CPs nanocomposite based chemosensors; (b) sensor systems with special focus on innovative conjugated polymer (CPs) chemical sensors for food freshness detection; and (c) applications of highly sensitive and selective (CPs) nanocomposite based chemosensors with Active/Intelligent technologies for meat and seafood spoilage detection Via colorimetric (naked eye detection) and fluorometric “turn - on/off” response, providing new pathways of CPs based nanocomposite chemosensor-application in the food industry. Thus, this review illustrates the potential scope of such intelligent sensor systems in food spoilage detection for commercial viability, resulting as a very simple, cost-efficient, consumer approved and other multipurpose tool.
... ZnO has a significant insight into spin filters and transport media. It has a wide range of applications in solar cells, [11], piezoelectric transducers [12], transparent conductive films [13], gas sensors [14], light-emitting devices [15], and biological (antibacterial and drug delivery) and chemical sensors [16]. ZnO with doping transition metal ions outlines the oxygen deficiencies and area in heterogeneous photocatalytic activities. ...
Article
Full-text available
Thin films of pure, Mn-substituted ZnO were synthesized by dip coating technique and irradiated thin films by Li³⁺ swift heavy ions (SHIs) with fluence 5 × 10¹² ions/cm². The XRD peaks revealed that all the samples exhibit hexagonal (wurtzite phase, P63 mc group) structures. The extra peaks were observed in XRD patterns, but after SHI irradiation, peaks were disappeared due to inelastic scattering. Pure ZnO manifests large spherical grain-shaped morphology after Li³⁺ SHI irradiation with fluence 5 × 10¹² ions/cm² as compared to pristine sample. The Mn-substituted ZnO thin films showed the rod-like shape and nanowire-like configuration for 5% after SHI irradiation. Raman spectra of the SHI-irradiated samples show oxygen vacancies, and also, phonon mode shifted to the blue shift as compared to pristine sample. Electrical properties were investigated by I–V measurements, which show that enhancement in conductivity as Mn content as well as SHI irradiation increased. Optical properties have been elaborated by UV-Vis, which confirm red shifting of the absorption edge after SHI irradiation. Graphical abstractMn-doped ZnO thin films irradiated with 50 MeV Li³⁺ SHI of fluence 5 × 10¹² ions/cm². Electronic and nuclear loss is 0.010 keV/μm, and range is 206.1 μm. Electronic and nuclear losses are shown in the figure.
... There are a significant number of amine vapor sensors based on polyaniline in the literature [29,30,[41][42][43][44][45][46], since in the presence of this alkaline volatiles, polyaniline suffers from deprotonation (dedoping), passing from emeraldine base salt (conductor, green species) to emeraldine base (non-conducting, blue species) [47]. Ammonia, particularly, is one of the most studied amines because is highly toxic [27,48,49]. As seen in Fig. S2, in the copolymer the absorptions at 450 nm and at 490 nm disappeared as a result of the amine vapors. ...
Article
For monitoring tilapia (Orechromis niloticus) freshness degree, a colorimetric method based on a copolymer of ortho-phenylenediamine and aniline, in a molar ratio of 1 to 1, was developed. The optical sensor changes color as a function of pH, therefore, it is sensitive to the presence of alkaline vapors such as the volatile amines (TVB-N) produced during fish spoilage. A kinetic approach was used to correlate the copolymer (sensor) response to the presence of ammonia, dimethylamine, and trimethylamine vapors, which are the main products generated by the bacteria during fish spoilage. The levels of TVB-N and microbial growth patterns (Pseudomonas spp), in specimens of tilapia fillets stored under refrigeration at 10 °C, correlated well with the color change of the copolymer, showing that after 48 h the specimen was no longer fit for human consumption.
... In the case of PANI, it exists in different oxidation forms built from the repeating unit of benzenoid and quinoid [10]. The oxidation level varies from the fully oxidized form to reduced form classified based on the degree of polymerization [11]. ...
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Poly(3,4-ethylenedioxyhiophene) (PEDOT), polyaniline (PANI), and polypyrrole (PPy) were prepared on indium tin oxide (ITO) substrate via potentiostatic from aqueous solutions containing monomer and lithium perchlorate. The concentration of monomers was varied between 1 and 10 mM. The effects of monomer concentration on the polymers formation were investigated and compared by using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. FTIR and Raman spectra showed no changes in the peaks upon the increment of the concentration. Based on the SEM images, the increment in monomer concentration gives significant effect on morphologies and eventually affects the electrochemical properties. PEDOT electrodeposited from 10 mM solution showed excellent electrochemical properties with the highest specific capacitance value of 12.8 mF/cm ² .
... Polyaniline (PANI) is most used conductive polymer [23]. Polyaniline has also been reported as gas sensor for the detection of methanol vapor [26,27], H 2 [28], SO 2 [29], NH 3 [30], CO 2 , NO 2 and SO 2 [31]. The response and sensitivity of polyaniline/zeolite (Y, 13X, and AlMCM41) to CO is described here. ...
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This review summarizes various zeolite/polymer composites which have been used as a sensor for different gases. In this review paper; properties of zeolite/polymer composites like simple synthesis and good electrical properties, etc. are discussed. Various strategies which affect the sensitivity of the composites are presented here. The sensitivity and response of zeolite/polymer composites to different gases are summarized.
... Among them, tungsten trioxide (WO 3 ) is considered to be one of the most interesting materials that could be used as a component of a gas sensor based on metal oxide semiconductors [8]. Porous WO 3 materials were prepared by anodization of sputtered tungsten thin films deposited on insulating substrates [9], tungsten oxide nanowires were synthesized by solvothermal method [10] and nanocrystalline tungsten oxide were obtained by the acid precipitation method [11] or sol-gel process [12]. Compared with other techniques, the aqueous chemical process is attractive because of its cost effectiveness and ease of material preparation. ...
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... Polyaniline (PANI) is one of the most favorable conducting polymer because of simple synthesis, low priced monomer, environmental stability etc [2]. Various studies have been carried out utilizing polyaniline for the detection of gases like methanol vapor [3,4], H 2 [5], SO 2 [6], NH 3 [7], CO 2 , NO 2 [1]. However, there still remain certain issues in using polyaniline as a gas or vapor sensor material: the sensitivity, the selectivity to a particular species amongst others, and its temporal response towards a target gas. ...
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... These methods include for example optical methods and methods based on changes in the electrical properties of the polymer. 26 Examples of polymers used for sensing applications include phospholipids for the detection of volatile anaesthetics, 33 polypyrrole 34 and polyaniline 35 for the detection of ammonia, and polymer nanojunctions for the detection of TNT. 36 ...
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This paper reports a novel, highly sensitive room temperature operable and reusable ammonia (NH 3) gas sensor based on Polyaniline-silver nanocomposite (PANI-Ag). The nanocomposite was synthesized by in-situ, sono-chemical oxidative polymerization methods by using ammonium persulphate. Aniline was used as a dispersant and stabilizer, D-glucose was chosen as an efficient reducing agent for the formation of Ag nanoparticles in the sol. The structural and optical properties of PANI-Ag nanocomposite were studied by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Morphological analysis of PANI-Ag nanocomposites revealed a cluster of PANI nanofibers with uniformly distributed silver nanoparticles having an average particle size of about 6 nm. The performance of PANI-Ag based sensor was evaluated at different concentrations of aqueous ammonia at room temperature. The sensor is highly sensitive at low ammonia concentration (less than 100 ppm). The sensor showed fast response and recovery time in the range of 30-120 s from 1 ppm to 100 ppm of ammonia concentration. The sensor showed an optimum response of 57% for 100 ppm ammonia. Due to excellent reversibility, reusability and long term environmental stability, PANI-Ag sensor provides a promising simple and efficient sensor system for wide-range ammonia concentration detection at room temperature.
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Chemical oxidative copolymerization has been employed for the synthesis of pyrrole and aniline copolymer at room temperature, in equal proportion. The prepared copolymer was undoped and then further doped with 10% NiCl2 using immersion method. Structural characterization of self-doped, undoped and doped copolymer was performed using FTIR, WAXD and SEM techniques. Results reveal the modifications in the original copolymer structure accompanied by various shifts in the band positions and appearance of the new bands in IR spectrum due to doping. The X-ray diffractograms reveals presence of modified and shifted peaks indicating the changes due to doping. The scanning electron micrographs of undoped and doped copolymers show globular structure due to doping when compared with that of the parent copolymer. In addition, using two probe methods the dc electrical conductivity of these samples was recorded in the temperature range of 313 K to 673 K, at a field of 27 V/cm. The log σ Versus 1/T plots of the self-doped and doped samples display the transformation of the sample at a given temperature from metallic to semi conducting and vice versa. The I-V plots for the self-doped and doped copolymer has also been plotted at a fixed temperature of 323 K which shows linear behavior of the samples. The conductivity measurements show reduction in conductivity of prepared samples thereby suggesting the presence of bipolarons as charge carrier. The results confirm the effect of doping on the copolymer properties.
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The past several decades have seen increasing concern regarding the wide distribution of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Primary toxicological data show PAHs’ persistent characteristics and possible toxicity effects. Because of this pressing global issue, electroanalytical methods have been introduced. These methods are effective for PAH determination in environmental waters, even outclassing sophisticated analytical techniques such as chromatography, conventional spectrophotometry, fluorescence, and capillary electrophoresis. Herein, the literature published on PAHs is reviewed and discussed with special regard to PAH occurrence. Moreover, the recent developments in electrochemical sensors for PAH determination and the challenges and future outlooks in this field, are also presented.
Chapter
There is an increasing need of gas sensing device for environmental monitoring and human’s health safety. Particularly, chemiresistive gas sensors having the capability to detect the chemical species (gases or vapors) at room or close to room temperature with good selectivity and high stability are very appealing. In this chapter, we present the fundamental properties of polyaniline (PANI)) responsible for chemiresistive sensing at room temperature. The sensing performance (sensitivity, response, recovery, stability, operating temperature and selectivity) of pure PANI are reviewed. Nanocomposites formed by incorporation of TiO2 nanoparticles (NPs) into PANI matrix show unique properties and offer various functionalities due to the synergic/complementary effects. These nanocomposites display high sensitivity with improved selectivity and stability, which is also discussed in this chapter.
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Electromagnetic interference (EMI) is a critical problem that originates from either outside or inside an airplane or space vehicles. In addition, EMI is an undesirable electromagnetic wave that makes trouble for electronic devices, disturbing their operation. The EMI shielding materials can show the better electromagnetic shielding performance for the various applications, including equipment and devices in various field such as aerospace‐aeronautic, electrical, electronics, military, communication, and home appliances. Low intensity radiated fields are generated from blue tooth devices, mobile phones, laptop, tablets and wireless accessories. A high intensity radiated field can either be engendered by mankind or occur naturally. There are two ways to obtain the effective shielding. One is active shielding and the other is passive shielding at low frequency electromagnetic fields. This chapter covers the topic of polymer composites for EMI shielding. It introduces the properties and characteristics of carbon nanotubes in order to describe the advantage of carbon nanotubes based polymer composites.
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Tosylcellulose stearate (TCSt) as a thermoplastic polymer has been prepared starting from microcrystalline cellulose (MCC) which was converted into a more reactive and solvent soluble tosylcellulose (TC) with degree of substitution = 0.45 under homogenous conditions. Then, tosylcellulose underwent esterification reaction through its reaction with stearic anhydride in DMF/DCM to afford tosylcellulose stearate. FT-IR, ¹³C NMR, and elemental analyses confirmed the chemical structure of both tosylcellulose and tosylcellulose stearate. TCSt fibers were used as matrix for polyaniline (PANI) which had been prepared via in situ oxidative polymerization of aniline hydrochloride using hydrochloric acid as dopant and ammonium persulfate as an oxidizing agent. PANI/TCSt composites with loading ratios of 75:25, 50:50, and 25:75 wt/wt were fabricated. The thermal stability, degree of crystallinity, and surface morphology of the prepared composites were characterized. The presence of PANI improved the thermal stability of the PANI/TCSt composites with (50:50 wt:wt). The electrical conductivity for PANI/TCSt composites was measured by Broadband Dielectric Spectrometer, and the conductivity values of PANI/TCSt composite prepared at weight ratio 75:25 wt% was coincided with those of PANI alone. Increasing the temperature from −40 to +50 °C increased the conductivity of the composites by about two orders of magnitudes for all investigated samples. The films prepared from TCSt and PANI/TCSt composite (50:50 wt:wt) displayed improved mechanical properties when compared with the films prepared from cellulose acetate (CA) and CA/PANI composite (50:50 wt:wt).
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Gas sensor devices normally use metal oxide semiconductors requiring high operating temperature, due to which the sensor often suffers from instability, response variation, poor selectivity and low sensitivity. Due to these limitations, intrinsically conducting polymers, such as polyaniline (PANI), polypyrrole, polythiophenes and their derivatives, are progressively being used as sensing layers operating at room temperature. PANI, in particular, has been extensively used due to its ease of fabrication, high stability, reversible doping/dedoping chemistry, stable electrical conduction mechanism, and high environmental stability. This chapter gives an overview of the detection of different kinds of gases, specifically ammonia and carbon monoxide, using polyaniline sensors.
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The strength of hydrogen bonds (HBs) decides water's properties and activities. It is recognized that the properties of confined liquid water, or liquid water in contact with hydrophobic surfaces, significantly differ from those of bulk liquid water. However, these unique properties of water are only found within the interfacial phase and a confined environment; thus, their applications are limited. Nowadays, environmentally friendly science, health and energy are main concerns in the world. In this review, an innovative and facile method for preparing mass-produced plasmon-activated water (PAW) with reduced HBs by letting bulk water flow through gold-supported nanoparticles (AuNPs) under resonant illumination at constant temperature is reported. The resulting stable PAW exhibits distinct properties and activities, which significantly differ from those of untreated bulk water. In addition, this PAW has the obvious advantages in environmentally friendly science, green energy, water saving and medicine. © 2017 The Korean Society of Industrial and Engineering Chemistry.
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The electropolymerization process of aniline on different electrode surfaces such as Pt, Au, RuTi and polyaniline film in nitric acid solution containing 1 M aniline was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Proposed electrical equivalent circuits were used to give a further analysis. Results show that the electrode materials accelerate the aniline electropolymerization remarkably as a catalyst, especially the electrochemical oxidation process of monomer aniline to its cation radical, which is the key step to incur the electropolymerization reaction of aniline on the electrode surface. The polymerization of aniline on RuTi electrode has the lowest reaction resistance for its adsorption sites, and the catalytic effects of these different electrodes decrease in the order: RuTi > polyaniline film > Pt > Au. The results also show that several states of polyaniline films are formed during the potential linear scan process in nitric acid solution and the corresponding oxidation and reduction reaction are reversible.
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In this paper, L-lysine based materials which are rich in amino groups were synthesized through chemical reaction. The polyaniline/polyacrylonitrile (PANI/PAN) thin film and PANI/PAN nanocomposite (NC) thin films doped with L-lysine based materials were obtained by electrospinning and in situ polymerization of aniline. The gas sensing properties of PANI/PAN thin film and PANI/PAN NC thin films doped with L-lysine based materials towards NH3, ethanol, acetone, chloroform and DMF were examined at room temperature. The experimental results reveal that PANI/PAN/ L-lysine based nanogel (4-Lys-4 nanogel) NC thin film exhibited a highly selective response toward NH3 at room temperature with improved response kinetics. The PANI/PAN/4-Lys-4 nanogel NC thin film showed the response of 5.5 with response and recovery times of 22 s and 15 s, respectively toward 100 ppm NH3, its detection limit could be 2.2 ppm. This response and recovery are quite fast compared with the reported works based on PANI doped with other materials. The enhanced response could be attributed to the large surface area, core-shell structure of the nanofibers and improved charge transfer as a result of a certain amount of amino groups doping PANI. Our results clearly indicate that PANI/PAN/4-Lys-4 nanogel NC thin film could effectively be used for the practical room temperature NH3 sensing application with quite fast response and recovery properties. At the same time, a new application of 4-Lys-4 nanogel on sensors is supplied.
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Dodecylbenzene sulphonic acid (DBSA) doped polyaniline (PANI) film have been successfully prepared by simple dispersion polymerization method. In this article stress has been given to compare the structural, morphological, spectral and gas sensing properties of DBSA doped PANI film using two different oxidising agents, namely ammonium per sulphate (APS) and potassium dichromate (PDC). The composite film oxidized by APS responses more to ammonia (NH3) vapour as compared to that prepared using PDC. Prior to vapour sensing investigation the composite film has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersion X-ray, UV–visible spectroscopy, fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) in order to investigate its structural, morphological, spectral properties and thermal stability respectively. Structure analysis shows better crystallinity nature of the APS oxidized film through the presence of sharper peaks in the XRD plot. The morphological studies, done through FESEM measurements, reveal more ordered nearly uniform one dimensional shapes in APS oxidized film. The UV–visible absorption spectra indicate better conductivity for the APS oxidized film. FTIR spectra confirm cross linking in the DBSA doped composite film from the presence of extra bands apart from those of PANI and DBSA. APS doped film is found to possess improved thermal and environmental stability as compared to the PDC oxidized film. It is observed that at room temperature (300 K), the response of the APS oxidized PANI film is found to be 63 % towards 100 ppm of NH3 gas. Also it shows better sensitivity, stability and correlations compared to the PDC oxidized film.
Article
The amperometric ammonia sensors based on Pt (electroplating) and Pt-Ir (electroplating)/Pt(sputtering)/porous ceramic plate (Pt(E)/Pt(S)/PCP and Pt-Ir(E)/Pt(S)/PCP) electrodes have been fabricated to detect the concentration of ammonia in 1.0 M KOH aqueous solution. The morphologies, crystallinities, and compositions of the sensing electrodes were analyzed by scanning electron microscope, X-ray diffraction, and electron probe micro-analyzer, respectively. The analysis results indicated that both the deposited Pt and Pt-Ir layers exhibited amorphous type. The sensitivities of the amperometric ammonia sensor for 0 similar to 155.5 ppm NH3 were obtained to be 8.31 +/- 0.03 and 7.86 +/- 0.02 mu A ppm(-1) cm(-2), respectively, when the Pt(E)/Pt(S)/PCP and Pt-Ir(E)/Pt(S)/PCP were used as the sensor electrodes, respectively. While the Pt(E)/Pt(S)/CP and Pt-Ir(E)/Pt(S)/CP electrodes were reactivated at -0.8 V for detecting every level of NH3, the sensitivities of the amperometric NH3 sensor would separately increase by 32.5 +/- 0.12% and 26.9 +/- 0.09%.
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In this work a molecular modeling method, which is capable of representing protonic acid doping of the emeraldine base polyaniline as a chemical sensing material, is presented. Validation of the atomistic models has been achieved by calculating physical parameters, such as densities, solubility parameters, and radial distribution function, of the polymers which has been shown to be in good agreement with the literature-reported experimental data. Via this simulation method, various relationships including pKa/pH, doping percentage/pH, charge carrier density/pH, and conductivity/pH of the protonated emeraldine salt are predicted and discussed. Comparisons with the measured data from Chiang and MacDiarmid confirm the authenticity and accuracy of our methodology. An approximate ~103 fold increase of charge carrier density in the variable range of pH 1.3-3.4 is observed and firstly reported. The molecular modeling methodology represented in this chapter that can be used to design and evaluate conductive polymers as chemical sensing materials for pH-based chemical sensors.
Article
Wire-like polyaniline (PANI) films were successfully electrodeposited onto an indium tin oxide (ITO) substrate using a pulse galvanostatic method (PGM) in a reverse micelle electrolyte. The as-prepared PANI films were electrochemically analyzed by cyclic voltammetry and electrochemical impedance spectroscopy in 1 mol·L−1 HClO4 solution. It is found that the as-prepared PANI films are highly porous, exhibit the diameters of approximately 100 nm and the lengths exceeding 3 μm, and have favorable electrochemical activities. Furthermore, the as-prepared wire-like PANI films show a good linear relationship of the potentiometric response curve over the pH value range of 3–10 with a slope of 74.13 mV·pH−1 in 0.5 mol·L−1 K2HPO4 basal solutions. The results demonstrate that the prepared wire-like PANI films are promising pH sensors. © 2015, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.
Article
For the first time we report a novel hybrid polyurethane synthesized from tetraaniline-diol (TAni-(OH)2) and hexamethylene diisocyanate (HMDI) with pendant tetraaniline units on the back bone. The striking property of this unprecedented polyurethane is its electrochemical sensing of ascorbic acid and self assembly into core-shell type microstructures (microcapsules) in presence of aqueous acetic acid/n-octane interface. These microcapsules exhibited a wide range of pH responses in their absorption spectrum. The synthesized polyurethane containing pendant tetraaniline units showed good surface conductivity to the tune of 3.4 × 10-4 S/cm. The electrochemical investigation showed two single electron oxidations and two single electron reductions reversibly. We also investigated electrochemical sensing details of carbon paste electrode (CPE) fabricated with conducting polyurethane (TANI-PU) as ascorbic acid sensor (vitamin C, AA) in 0.2 M and pH 7 phosphate buffer solution. The fabricated electrode is useful in sensing as low as 1 mM of ascorbic acid. Self-assembly property was probed by optical and TEM studies which established the core-shell structure of the assembled species. The self assembled microcapsules exhibited pH dependent doping and dedoping processes as established by UV-Vis study.
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Details of the growth properties of polyaniline (PA) have been studied employing electrochemical techniques (potential cycling method) and the results are reported. The electrochemical growth may be characterized as autocatalytic, and the growth rate is first order in aniline concentration. The growth rate is also dependent on the amount of PA film on the electrode as well as the number of potential cycles. The highest oxidized PA, attacked by an aniline molecule, grows to a longer chain, and a net reduction of the PA film upon aniline addition would render the film conducting. This mechanism explains why the film continues to grow at potentials where only passivating behavior would be predicted. In addition, the growth was divided into regions of well‐defined and poorly defined (amorphous) phases; at longer oxidation times during growth, side reactions seem to play more important roles compared to the earlier phase of the growth process.
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A method is described to graft conducting polyaniline onto glass fabric, glass wool and nylon cloth to impart flexibility and mechanical strength to the polyaniline, which is otherwise powdery and untracable. These flexible conductive surfaces can find application as antistatic shields.
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Conducting polymers may be used as sensitive layers in chemical microsensors leading to new applications. They offer the potential for developing material properties that are critical to the sensitivity, selectivity and fabrication of chemical sensors. The advantages and limitations of the use of thin-polymer layers in potentiometric sensors are discussed.
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Molecular recognition principles are being increasingly used as the basis for analytical technologies. The combination of a molecular recognition approach with conducting polymer materials has been beneficial, particularly in the field of electrochemical sensing. The electrochemical sensing process usually consists of two steps: analyte recognition and signal generation. Conducting polymers are versatile materials in which molecular/analyte recognition can be achieved in a number of different ways, including the incorporation of counter ions that introduce selective interactions, using the inherent and unusual ion-exchange properties of the conducting polymers; the addition of functional groups to the monomers; and the codeposition of metals within the polymer. Specific examples of these approaches are provided. The molecular recognition properties of conducting polymers can be further refined by the application of appropriate electrochemical potentials, which can induce either large or small changes in the chemical interactions that occur at the polymers. This electroactivity, as well as their conducting properties, also provides the basis for the signal generation steps. A number of electronic signals relating to some chemical or electrochemical change within the polymer can be measured. These include the faradaic electron transfer typically used for electrochemical sensing, the catalysis of the analytically useful electron transfer by the polymer or the analyte, the change in capacitance signals induced by the analyte species and changes in the polymer resistance which can be measured by a recently developed technique. These features, combined with the molecular recognition properties, make conducting polymers a very promising material for electrochemical sensing technology.
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The effect of different solvents on the electronic properties of Polyaniline (PANI) films in the solid state has been investigated. The electrical conductivity and spin number varies with the concentration of water, alcohols and acetonitrile in the gas phase in contact with the polymer. The immobilisation of Adenosine Tri-Phosphate (ATP) and lactate in Polypyrrole (PPy) films and the properties of these materials was studied. These investigations demonstrate the possible applications of PANI and PPy films as sensor materials.
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A secondary battery of the type , carbon is described. The polymer was electrodeposited on porous carbon rods, in the form of consistent, rather thick, highly porous, and low‐resistance layers. The battery was assembled in a configuration similar to that of the classical R‐6 dry cell. The performance of the battery has been studied, and it shows characteristics comparable to those of conventional systems: moderate specific energy (50–100 Wh · kg−1), very good coulombic efficiency (70–100%), low self‐discharge rate (<1% day), and excellent cyclability at high current densities.
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An attempt was undertaken to prepare polyaniline with a fine linear structure in aqueous media. Comparable electrochemical polymerization was carried out in solutions of the following acids: hydrochloric, sulfuric, perchloric and tetrafluoroboric. Spectroelectrochemical measurements have revealed the presence of an intermediate product (nitrenium cation) in the initial stage of aniline polymerization carried out in these media. The polymerization starts after an induction period which depends on the final potential for cyclic voltammetry and the nature of the medium. The number of spins as a function of the applied potential was a criterion to determine the linearity of the polymer chain. In polymers with linear structure (without ortho-bindings and cross-linking effects), polarons formed during the doping process in the presence of double-charged anions undergo a recombination process to form bipolarons. As a result no EPR signal is observed between the two redox systems of polyaniline. This kind of polymer can be formed only by voltammetric polymerization in a 5 M solution of tetrafluoroboric acid. The other media mentioned lead to formation of more or less cross-linked chains. The measurements performed suggest that the mechanism of aniline polymerization in aqueous media is analogous to that in non-aqueous solutions for a eutectic mixture of NH4F; 2.35 HF.
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This report describes the synthesis and redox behaviour of polyaniline in aqueous solutions of benzene sulphonic acid and 4-toluene sulphonic acid. The characterization of the polymer was carried out by electronic spectra, FTIR studies and 1HNMR in DMSO-d6.
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Anodic growth of polyaniline films on a Au microelectrode array has been carried out to add to the characterization of polyaniline and to fabricate polyaniline-based microelectronic devices, diodes and transistors, that function when the polyaniline-functionalized microelectrode array is immersed in an electrolyte solution. The microelectrode array is a set of eight Au electrodes, 0.1 μm thick, 4.4 μm wide, and 50 μm long, each individually addressable and separated from each other by 1.7 μm. Polyaniline can be deposited in controlled amounts by electrochemical oxidation of aniline. When the polyaniline is deposited in sufficient amounts, two or more of the eight Au microelectrodes can be connected in the electrical sense. Current can pass between two connected microelectrodes when there is an applied potential between them. The magnitude of the current at a given applied potential depends on the electrochemical potential of the polyaniline. In 0.5 M NaHSO4/H2O the current (at a fixed applied potential) is maximum at an electrochemical potential of ∼+0.4 V vs. SCE and declines by a factor of > 106 upon reduction to +0.1 or oxidation to +0.7 V vs. SCE. Owing to the large change in resistance upon change in electrochemical potential, the functionalized microelectrodes can function as diodes or transistors. The small spacing between the microelectrodes is crucial to device function, owing to the limited conductivity of the polyaniline. The switching time of a transistor-like device is faster than 0.1 s.
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The results of investigations of the chemical and electrochemical polymerization of aniline in sulphamic acid medium and its characterization by electrochemical and spectroscopic techniques are presented. The investigations reveal that sulphamic acid medium affects, not only the polymerization process, but also its electrochemical characteristics.
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The charge-discharge characteristics of polyaniline (PAn)-Nafion-PAn composite films used as rechargeable batteries were investigated. The batteries were formed chemically by sandwiching Nafion between two thin layers of PAn-Nafion composite in equilibrium with various electrolytes. It was found that cells with LiClO4 in propylene carbonate as electrolyte showed the highest capacity. The charge and discharge performance of the battery was almost independent of the choice of anions but was significantly affected by cation size. This may indicate that the insertion or removal of charge-compensating electrolyte cations from the composite layer was responsible for the redox of PAn during the charge and discharge cycles.
Article
Results of the investigation of the chemical and electrochemical polymerization of aniline in 5-sulfosalicylic acid medium and its characterization by electrochemical and spectroscopic techniques are presented. The investigation reveals that 5-sulfosalicylic acid as a dopant not only enhances electrochemical stability of polyaniline at higher potentials but also yields a polymer which is soluble to the extent of 11 g/l in DMSO. The characterization of conducting polyaniline thus obtained was carried out by electronic and vibrational spectra, 1H NMR in DMSO-d6, X-ray powder diffraction, thermal analysis and by electrochemical techniques.
Article
Absorption spectra are presented for polyaniline in dilute solution in concentrated sulfuric acid and in the form of spin-cast films (spun from sulfuric acid solution and subsequently washed with water). The results from samples prepared with different molecular weights and with different degrees of protonation (in the case of the films) are compared. For the emeraldine salt, we observed three absorption features, at 1.0 eV (with a tail extending deep into the infrared), 1.5 eV and 3.0 eV. The relative intensities of the 1.0 and 1.5 eV absorptions are strongly dependent on both the molecular weight and the protonation level, with important differences for the solid film and the solution spectra. The results imply that the 1.0 eV absorption is the principal signature of the intrachain (free carrier) excitations, and that the 1.5 eV absorption arises from interchain excitation. A method to prepare stable fully oxidized polyaniline in concentrated sulfuric acid is presented; the spectrum of the charged bipolaron lattice of fully oxidized polyaniline exhibits a strong absorption band centered at 2.2 eV and a weaker absorption at 4 eV. The available data provide the basis for an understanding of the electronic structure of the four principal forms of polyaniline: the fully reduced leucoemeraldine, the emeraldine base, the oxidized and fully protonated emeraldine salt, and the fully oxidized bipolaron lattice.
Article
In the field of research on soluble conducting polymers, the poly(o-alkylanilines) are very interesting because we can expect them to give more soluble polymers and new properties. Like poly(o-propylaniline) (POP), which is more soluble than polyaniline (PANi), poly(o-hexylaniline) (POH) appears to be more soluble in organic solvents than POP because of the longer alkyl groups in the 2-position. The higher solubility confers better processability on this new polymer, and because of this solubility, an NMR study in solution became possible.The nitration of hexylbenzene and the reduction of the resulting product to o-hexylaniline were performed according to the literature. The chemical polymerization was easy and it is possible to produce this polymer in large quantities.The polymerization carried out in anhydrous NH4F, 2.35 HF medium and in 5 M perchloric acid gave a polymer with almost quantitative yield. The electrochemical behaviour of POH displayed faster electron transfers than PANi in organic solvents, depending on the acido-basicity level of the aqueous solutions. Unlike PANi, fractal growth was not observed.
Article
The application of four different conducting polymers (polypyrrole, poly-N-methylpyrrole, poly-5-carboxyindole and polyaniline) as sensors for organic vapours has been investigated.The sensors are formed by the electrochemical polymerization of the appropriate monomers across a 12 μm gap between two gold microband electrodes. Upon exposure to vapours the polymers show conductivity changes that are rapid and in general reversible at room temperature.Of the four polymers investigated, under the deposition conditions employed and for the vapours used (methanol, ethanol, acetone, ether and toluene), poly-5-caboxyindole is found to give the most stable, reproducible behaviour and to be the most promising material for sensor applications. The use of these materials in intelligent gas sensors is discussed.
Performance study of Zn/ZnC12
  • F Trinidad
  • M C Montemayer
  • E Fatas
F, Trinidad, M.C. Montemayer and E. Fatas, Performance study of Zn/ZnC12, NH4C1/polyaniline/carbon battery, d. Eleetrochem. Soe., 138 (1991) 3186-3189.
Conducting polymers and the biological sciences: new tools for biomolecular communications
  • Adelojn
Solubilizing effect of organic acids on polyaniline
  • Dhawan