89,707 research outputs found
Optical and transport properties of polyaniline films
No full textThis thesis presents the results of a comprehensive study on the transport and optical properties of polyaniline (PANI) films. The films are derived by protonation (doping) of the emeraldine base form of polyaniline, as synthesized in Durham, with either 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPSA) or 10- camphorsulfonic acid. Thus, two distinct PANI systems are obtained: PANI-CSA and PANI-AMPSA. The variation of the doping level can affect the metallic properties of the final system, so that samples close to the boundary as well as samples at either side of a disorder induced metal-insulator can be obtained. The relation between the doping level and the degree of disorder, along with the existence of an inherently metallic behaviour in PANI, are investigated through a series of experiments. Temperature dependent dc conductivity measurements ranging from 10-295 K are performed using a closed loop helium cryostat under dynamic vacuum (~10(^-5) mbar). From the conductivity data curves, typical fingerprints of the metallic behaviour are detected for certain samples and an initial estimate of the degree of disorder is implicitly attained. More specific information regarding the microscopic contributions to the transport mechanisms is obtained via low temperature (down to 1.5 K) magnetocon- ductance measurements on selected samples. The magnetic field dependence of conductivity for fields up to 14 T is measured and the suitability of the localization- interaction model for the understanding of the transport mechanism in PANI is examined. Infrared reflectivity (20-9000 cm(^-1)) measurements on samples of both PANI systems are performed. The experimental configuration permits the determination of the sample’s absolute reflectivity. The optical constants are deduced from Kramers- Kronig analysis of the reflectivity data. Typical features of metallic behaviour are examined and analysed in the context of the localization modified Drude model. The results are shown to be consistent with the transport measurements, indicating that PANI is a disordered metal close to the boundary of a disorder induced metal- insulator transition
Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization
No full textHydrogen sulfide (H2S) gas sensors in the form of thin films based on polyaniline (PAN) incorporated with various concentrations of functionalized single wall carbon nanotubes (f-SWCNT) were prepared by electrochemical polymerization of Aniline monomer with sulfuric acid in an aqueous solution. Surface morphology of the thin film nanocomposites was investigated by Field Emission Scanning Electron Microscopy (FE-SEM) and revealed that the f-SWCNTs were almost uniformly distributed on the surface of the host PANI matrix. The X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Hall effect measurements were used to characterize the synthesized PANI/f-SWCNT nanocomposites. The Hall measurements reveal the p-type conductivity. The grown FTIR band at 1145 cm−1 with the increase of the f-SWCNT content evidence a formation of charge transfers due to a remarkable interaction between PANI and f-SWCNTs. The response of this nanocomposite film towards the H2S gas was investigated by monitoring the change in the electrical resistance with the time in the presence of 30% H2S at different operating temperatures. The sensing analysis showed that the sensitivity increased with f-SWCNT content in the PANI matrix. The rapid response/recovery times toward the H2S gas, at 50 °C, was achieved for a PANI/0.01% f-SWCNT nanocomposite sample. Keywords: Conductive polymer, PANI, Nanocomposites, f-SWCNT, H2S gas senso
The synthesis of rGO/RuO2, rGO/PANI, RuO2/PANI and rGO/RuO2/PANI nanocomposites and their supercapacitors
No full textAbstract: In this work, reduced graphene oxide (rGO) was obtained by chemical reduction of graphene oxide (GO) using sodium borohydride (NaBH4). Four different nanocomposites rGO/ruthenium oxide (RuO2), rGO/polyaniline (PANI), RuO2/PANI and rGO/RuO2/PANI were chemically synthesized. In addition, PANI-based nanocomposites were synthesized by in situ polymerization technique. Nanocomposites were examined by different methods such as Fourier transform infrared spectroscopy–attenuated transmission reflectance, UV–Vis spectrophotometer, scanning electron microscopy–energy-dispersive X-ray analysis, thermal analysis (TGA–DTA) and transmission electron microscopy. TGA–DTA results show that the decomposition of rGO/RuO2/PANI nanocomposite (27.2% at 788.8 °C) was less than that of rGO (1% at 779.7 °C), which confirms the successful synthesis of nanocomposites. These nanocomposites can be used in supercapacitor applications. Supercapacitor device performances were taken by cyclic voltammetry (CV), galvanostatic constant current and electrochemical impedance spectroscopy (EIS) via two-electrode configuration. Ragone plots were drawn to observe energy and power densities of supercapacitor devices. Stability tests were taken by CV method for 1000 cycles. A ternary rGO/RuO2/PANI nanocomposite yields higher specific capacitance as Csp = 723.09 F g?1 than rGO/RuO2 (Csp = 347.28 F g?1), rGO/PANI (Csp = 159.62 F g?1), RuO2/PANI (Csp = 40.2 F g?1) and rGO (Csp = 37.5 F g?1) at 2 mV/s by CV method. A new electrical circuit model of LR(C(R(CR))) was used to analyze EIS data for rGO, rGO/PANI, rGO/RuO2, RuO2/PANI and rGO/RuO2/PANI nanocomposites. These nanocomposites demonstrate remarkable properties for use as electroactive materials for supercapacitor applications. Graphic abstract: [Figure not available: see fulltext.]. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature
Letizia Ermini Pani e l’Umbria
No full textIl contributo traccia le linee del rapporto fra Letizia Ermini Pani e l'Umbria, regione nella quale ha a lungo lavorato, e nella quale è stata promotrice di ricerche archeologiche fondamentali per ricostruirne la storia
THERMAL STABILITY AND GLASS TRANSITION BEHAVIOR OF PANI/MWNT COMPOSITES
No full textPolyaniline/multi-walled carbon nanotube (PANI/MWNT) composites were prepared by in situ polymerization. Transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) were used to characterize the PANI/MWTNT composites. Thermal stability and glass transition temperature (T(g)) were measured by thermogravimetry (TG) and temperature modulated differential scanning calorimetry (TMDSC), respectively. The TG and derivative thermogravimetry (DTG) curves indicated that with augment of MWNTs content, the thermal stability of PANI/MWNT composites increased continuously. While, T, increased and then decreased with the MWNTs content increasing from 0 to 20 mass%
The formation volume in rare earth intermetallic systems: A representation by means of atomic physical quantities
No full textThe formation of the intermetallic phases is often accompanied by large volume effects, and several interpretations of this phenomenon have been proposed following different approaches, either from a simply empirical or purely theoretical point of view. In his pioneering work, Biltz (Biltz 1934) employed the experimental density values to list the molar volumes of the elements and of numerous inorganic and organic solids, including intermetallic phases. The systematic analysis of the data allowed the scientist to estimate the effective volumes of the atoms within the compounds, making possible the application of the volume additivity. Machlin studied the effects of electronegativity on energy and volume of formation, assuming that the volume corrections depend on the Gordy electronegativity difference (Machlin 1980). Watson and Bennett obtained 82a good correlation between the volume effects shown by the phases of the transition elements and a scale resembling the Gordy electronegativity, while a cellular method was applied to estimate the volume changes in phases with alkaline and alkaline earth metals (Watson and Bennett 1982, 1984). Alonso showed that a model of a disordered binary alloy of nontransition metals explains the tendency to a negative deviation from Vegard’s law as this lowers the energy of formation (Alonso et al. 1984). In the Miedema model (Miedema and Niessen 1982), the volume contraction in metallic systems can be ascribed to a charge transfer effect, described mainly by the differences both in an electronegativity-like scale (F*) and in the electron density parameter (nWS). Moreover, in systems with atoms of different radius, a further volume contraction may arise from elastic size mismatch energy. The differences in electronegativity are ignored in the Hafner approach, based on the lowest-order pseudopotential perturbation theory (Hafner 1985). This method provides good results for extended solid solutions of homovalent systems (intra-alkaline and intra-alkaline-earth alloys) and for some intermetallics of the cited elements. A phenomenological approach was used to describe the volume effects displayed by the intermetallic compounds formed by alkaline earths (Ca, Sr, Ba) and divalent rare earths (Eu, Yb) (Merlo 1988) and by the trivalent rare earths (Merlo and Fornasini 1993), introducing a charge transfer atomic parameter, correlated with Pauling’s electronegativity. More recently, the volume contractions of the binary phases of Ca, Sr, Ba, Eu and Yb were represented by a simple equation containing the electronegativity, the compressibility and the group number (Fornasini and Merlo 2006). The most advanced method is based on the calculation of partial atomic volumes and charges as a function of composition (Baranov et al. 2007)
Preparation and comparison of two electrodes for supercapacitors: Pani/CNT/Ni and Pani/Alizarin‐treated nickel
No full textPolyaniline in emeraldine form was synthesized in the presence of multiwalled carbon nanotubes (CNTs), and the electrochemical capacitance performance of thus formed composite as electrode material has been Studied. The polyaniline/carbon nanotubes (Pani/CNT) composite is found to result in a higher specific capacitance than that of either composite constituent, attributable to the double-layer capacitance behavior of the nanotubes in the Pani/CNT system. However, once assembled into a two-electrode cell, lower than expected specific capacitance values from 1 to 20 F/g were obtained, and such reduction is most likely caused by the contact resistance between the Pani/CNT electrodes and the nickel (Ni) current collectors. To improve the situation, a chemical treatment was applied to the nickel foil, and the Pani solution is then deposited on the surface of the foil to form a coated structure (Pani/Ni). The thickness and weight of the Pani films can be controlled by adjusting the concentration of the Pani solution. The specific capacitance of the cell with electrodes made of the new Pani/Ni composite was found to reach as high as 35.5 F/g. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1070-1081, 200
Fusobacterium & Co. at the Stem of Cancer: Microbe–Cancer Stem Cell Interactions in Colorectal Carcinogenesis
No full textAdult stem cells lie at the crossroads of tissue repair, inflammation, and malignancy. Intestinal microbiota and microbe–host interactions are pivotal to maintaining gut homeostasis and response to injury, and participate in colorectal carcinogenesis. Yet, limited knowledge is available on whether and how bacteria directly crosstalk with intestinal stem cells (ISC), particularly cancerous stem-like cells (CR-CSC), as engines for colorectal cancer initiation, maintenance, and metastatic dissemination. Among several bacterial species alleged to initiate or promote colorectal cancer (CRC), the pathobiont Fusobacterium Nucleatum has recently drawn significant attention for its epidemiologic association and mechanistic linkage with the disease. We will therefore focus on current evidence for an F. nucleatum-CRCSC axis in tumor development, highlighting the commonalities and differences between F. nucleatum-associated colorectal carcinogenesis and gastric cancer driven by Helicobacter Pylori. We will explore the diverse facets of the bacteria–CSC interaction, analyzing the signals and pathways whereby bacteria either confer “stemness” properties to tumor cells or primarily target stem-like elements within the heterogeneous tumor cell populations. We will also discuss the extent to which CR-CSC cells are competent for innate immune responses and participate in establishing a tumor-promoting microenvironment. Finally, by capitalizing on the expanding knowledge of how the microbiota and ISC crosstalk in intestinal homeostasis and response to injury, we will speculate on the possibility that CRC arises as an aberrant repair response promoted by pathogenic bacteria upon direct stimulation of intestinal stem cells
FeNiS/PANI Hybrid Composite for Enhanced Electrochemical Energy Storage Performance
No full textThis study focuses on developing FeNiS/PANI composites for supercapacitor applications, leveraging the individual benefits of iron–nickel sulfide (FeNiS) and polyaniline (PANI). FeNiS offers high electrical conductivity and energy density, while PANI contributes enhanced flexibility and pseudocapacitive behavior. The goal is to create a composite with superior electrochemical performance. Synthesis involved chemical oxidative polymerization for PANI and an in situ method for FeNiS, followed by integration. Characterization techniques like XRD, SEM, and EDS confirmed the successful formation and homogeneous elemental dispersion of the composite, showing that PANI formed an interconnected network that improved charge transport. Electrochemical analysis demonstrated significant improvements. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests revealed that the FeNiS/PANI composite exhibited a doubled discharge time (159 s vs. 72 s for FeNiS) and a higher specific capacitance (113.5 F/g vs. 51.42 F/g). These results highlight the promise of FeNiS/PANI as an advanced material for efficient and sustainable energy storage
KARAKTERISTIK KOMPOSIT PANI/GO SEBAGAI ELEKTRODA SUPERKAPASITOR: Keywords: electrode, electrodeposition, GO, PANi, supercapacitor
No full textAbstrak
Superkapasitor adalah salah satu perangkat penyimpanan energi yang dapat menyimpan energi lebih banyak dibandingkan kapasitor dan menyalurkan energi dengan keluaran yang lebih tinggi dibandingkan baterai. Komponen superkapasitor meliputi elektrolit, elektroda, pemisah (separator), dan pengumpul arus. Elektroda merupakan salah satu komponen penting dalam superkapasitor, maka pemilihan bahan elektrodan dan fabrikasinya sangat penting dalam meningkatkan kinerja superkapasitor. Penelitian ini bertujuan untuk menganalisis karakteristik komposit PANi/GO sebagai elektroda superkapasitor dan menganalisis pengaruh massa GO terhadap kapasitansi elektrokimia komposit PANi/GO. Pembuatan elektroda menggunakan metode elektrodeposisi untuk membentuk lapisan komposit PANi/GO pada substrat stainless steel. Selanjutnya hasil sintesis elektroda komposit PANi/GO dikarakterisasi dengan SEM-EDX, FTIR, uji LCR Meter, dan uji CV. Hasil penelitian menunjukkan bahwa karakteristik komposit PANi/GO sebagai elektroda superkapasitor dapat dilihat melalui nilai konduktivitas listrik dan nilai kapasitansi spesifiknya. Nilai konduktivitas yang dihasilkan berada pada rentang 3,22 x 10-2 hingga 11,11 x 10-2 S/cm dan nilai kapasitansi spesifik yang dihasilkan berada pada rentang 61,250 hingga 11,857 F/g. Selain itu, variasi massa GO yang digunakan memiliki pengaruh terhadap kapasitansi elektrokimia komposit PANi/GO yaitu dengan adanya penambahan massa GO dapat mengakibatkan turunnya nilai apasitansi spesifik dari elektroda.
Kata Kunci: elektroda, elektrodeposisi, GO, PANi, superkapasitor
Abstract
Supercapacitors are one of the energy storage devices that can store more energy than capacitors and distribute energy with higher output than batteries. Supercapacitor components include electrolytes, electrodes, separators, and current collectors. Electrodes are one of the important components in supercapacitors, so the selection of electrode materials and their fabrication are very important in improving supercapacitor performance. This study aims to analyze the characteristics of PANi/GO composites as supercapacitor electrodes and analyze the effect of GO mass on the electrochemical capacitance of PANi/GO composites. The electrodes were made using the electrodeposition method to form a PANi/GO composite layer on a stainless steel substrate. Furthermore, the results of the synthesis of PANi/GO composite electrodes were characterized by SEM-EDX, FTIR, LCR Meter tests, and CV tests. The results showed that the characteristics of PANi/GO composites as supercapacitor electrodes can be seen through their electrical conductivity and specific capacitance values. The resulting conductivity values ??are in the range of 3,22 x 10-2 to 11,11 x 10-2 S/cm and the resulting specific capacitance values ??are in the range of 61,250 to 11,857 F/g. In addition, the variation of the GO mass used has an effect on the electrochemical capacitance of the PANi/GO composite, namely that the addition of GO mass can result in a decrease in the specific capacitance value of the electrode.
Keywords: electrode, electrodeposition, GO, PANi, supercapacito
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