Papers by Keyword: Polypyrrole

Abstract: A gas sensor based on a multi-walled carbon nanotube (MWCNTs-OH) network was fabricated by filtration from the suspension method (FFS), and its properties were improved by coating the network with a polypyrrole conductive polymer. The polymer was prepared using the chemical oxidation method. Metallic nanoparticles of silver and copper were added separately to the polymer by the in situ chemical oxidation method. The fabricated networks were characterized using an X-ray diffractometer (XRD) and a Photoluminescent spectrometer. For the networks of (MWCNTs) with polypyrrole (PPy), (PPy: Cu), the (002) peak's widening diminishes, and the broadening increases when silver (PPy:Ag) is added to the MWCNTs networks. The crystalline size decreases for the networks coated by (PPy) as well as silver NPs (PPy:Ag), while it increases with the network coated by (PPy:Cu). Photoluminescence spectra of the networks were measured at different excitation wavelengths (340-380) nm and the networks gave the emission spectra in the range of (765-855) nm. The analysis revealed that the energy gap becomes larger for the networks coated with (PPy: Ag), (PPy: Cu) networks than for pure MWCNTs. A homemade sensing device was used to evaluate the sensitivity of the fabricated networks for gas concentration of 20 ppm at room temperature. The sensitivity of the fabricated sensor was (56.17%). After modifying the surface of the fabricated network by coating with the polypyrrole conductive polymer and polypyrrole composite with silver and copper metallic nanoparticles, the sensitivity became (59.29, 64.5, and 65.3) % respectively.

Abstract: Herein, we have synthesized polypyrrole grafted graphene oxide (GO-g-PPy) nanohybrids by a free radical emulsion graft polymerization method. GO was used as the substrate for pyrrole grafting. The parameters of the graft polymerization reaction were optimized. The optimum concentrations of surfactant, monomer and initiator were 0.25 wt. %, 3 vol.%, and 7 wt.%, respectively. The maximum grafting percentage was 989.6% at these optimal reaction parameters. The formation of the grafted nanohybrids was confirmed by Fourier transform infrared spectroscopy (FTIR) and thermal stability studies were carried out by thermogravimetric analysis (TGA). GO-g-PPy naohybrids can be used as functional additives or conductive materials for EMI shielding applications.

Abstract: Nowadays, the enhancement of electrical conductivity in natural rubber has been widely studied by incorporating conductive particles with various techniques into rubber latex. Acetylene black is one of the carbon nanoparticles known for its electrical conductivity property. However, its hydrophobicity leads to poor dispersion in rubber latex. Therefore, admicellar polymerization (AP) technique was chosen to modify particle surface without changing the molecular structure. This technique alters surface hydrophobicity by means of coating ultrathin film of polymer onto the particles. Polypyrrole, a conductive polymer, was chosen to enhance the dispersion of acetylene black. The modified acetylene black was used as the electrically conductive additives in natural rubber. There were four variables in this study: i. the carbon particle-to-surfactant ratio, ii. the agitation speed during the AP step, iii. polymerization temperature, and iv. the surfactant agent-to-monomer ratio. The morphologies of modified particles were observed by SEM and TEM. The results showed that the best conditions yielding the lowest resistivity of conductive rubber at 1:3 for the carbon particle-to-surfactant mass ratio, at 1000 rpm for the agitator speed, in AP step was 4°C for the polymerization, and 1:5 for the mass ratio of the surfactant agent-to-monomer.

Abstract: Short Multi-Walled Carbon Nanotubes functionalized with OH group (MWCNTs-OH) were used to synthesize flexible MWCNTs networks. The MWCNTs suspension was synthesized using Benzoquinone (BQ) and N, N Dimethylformamide alcohol (DMF) in specific values and then deposited on filter paper by filtration from suspension (FFS) method. Polypyrrole (PPy) conductive polymer doped with metallic nanoparticles (MNPs) prepared using in-situ chemical polymerization method. To improve the properties of the MWCNTs networks, a coating layer of (PPy) conductive polymer, PPy:Ag nanoparticles, and PPy: Cu nanoparticles were applied to the network. The fabricated networks were characterized using an X-ray diffractometer (XRD), UV-Vis. spectrometer, and Atomic Force Microscope (AFM). XRD results revealed that the broadening for the (002) peak decreased after being coated with PPy and increased for the doped samples with MNPs, indicating on decrease in the crystalline size (MWCNTs/PPy) sample and increasing for doped ones with Ag and Cu MNPs. AFM images revealed that the surface roughness of the MWCNTs-OH network decreased after being coated with PPy, PPy: Ag, and PPy: Cu. With the help of AFM and XRD results, the CNTs contain 14 layers, while the inner and outer diameters were 18.2 nm and 27 nm receptivity. The UV-Vis. spectrum of MWCNTs showed several peaks, the highest in the 350 nm range. The coated of MWCNTs greatly affected the absorption spectrum, with many bands appearing between 300 to 450 nm and increasing the absorbance along the overall spectrum. For samples doped with Ag NPs and Cu NPs, a weak absorption peak of the plasmonic resonance frequency of the metallic nanoparticles. Analysis of Raman spectra shows that (I_D/I_G) ratios for all networks are less than one, which prove that the fabricated networks have few impurities and have good homogeneity. This work aimed to synthesize and characterize a flexible MWCNTs network and develop it by coated with a layer of conductive polymer and metallic nanoparticles for gas sensing application using quick and straightforward preparation methods.

Abstract: Based on mechanism of ECH (Electrocatalytic Hydrogenation),the Pa/PPy/Foam-Ni (Pd/PPY/Ni) prepared by electrical depositing was used as cathode to detoxifythree kinds of dichlorophenol (DCP) and improve their biodegradability. According to the dechloridation ability of electrodes prepared under different conditions, the factors were optimized. The removal efficiency of 2,4-dichlorophenol（2,4-DCP）reaches 64.45% when the supporting electrolyte is p-toluenesulfonic acid and the voltage is 0.6V and polymerizing time is 20mins. Analyzing the photograph from SEM (Scanning Electron Microscope), it shows that PPy (PolyPyrrole) changes depositing properties of Pa on foam-Ni substrate, which increases specific surface area and special ductility so as to benefit Pd to deposite on Ni substrate and improve ECH.

Abstract: Metal coating films were deposited on the surface of the pieces of non-conducting polymers, acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS) and poly (lactic acid) (PLA). These three polymers have been used since they are the main raw materials available for fusion and deposition molding equipment. In order to achieve surface metallization by electrodeposition, it was necessary to apply a pre-treatment using the chemical polymerization technique in solution with the electroconductive polymer polypyrrole (PPy) was deposited on the specimens. A uniform layer of PPy was deposited on the surface of the specimens of the ABS and HIPS polymers, while in the specimen of the polymer PLA this layer showed uniformity faults. After this pretreatment was possible to perform copper electrodeposition, creating the metallic coatings on the ABS / PPy, HIPS / PPy and PLA / PPy surfaces. This metallic coating was uniform in all specimens except the one of the PLA polymer that was not sanded. The adhesion of the coating was evaluated by the adhesion test with tape and the quality of the appearance (absence of visual defects), the morphology, the uniformity, the thickness, the conductivity and the adhesion quality of the films were analyzed.

Abstract: The in situ chemical deposition of polypyrrole (Ppy) in presence of different concentrations of salicylic acid (SA) directly at copper 99.9% surface in ethanol solution using hydrogen peroxide as catalyst was studied. In all the concentrations, 50.0, 25.0, 12.5 and 6.25 mmol L^-1 the polymerization was possible. The layer formed on the copper surface showed to be adherent and homogeneous. Its morphology presented as compact microspheres. The polarization curves showed a positive displacement in the corrosion potential of copper with undoped Ppy when compared to the polished copper surface. Copper surfaces containing doped Ppy-SA also showed an increase to the positive direction in the corrosion potential and the corrosion current density decreases more sharply in the presence of SA as dopant. These results indicated that Ppy+SA can act as a protective layer on copper surface and improve the corrosion protection. The protection efficiency of the coating was Cu surface < Cu+Ppy < Cu+Ppy+SA 50.0 < Cu+Ppy+SA 25.0 < Cu+Ppy+SA 12.5 < Cu+Ppy+SA 6.25 mmol L^-1.

Abstract: Polypyrrole nanoparticles prepared in the presence and absence of polyvinylpyrrolidone (PPy/PVP) fine black powders have been synthesized as adsorbents for the removal of copper Cu (Ⅱ) and iron Fe (Ⅲ) ions from aqueous solution. PPy and PPy/PVP were chemically prepared by using ferric chloride as an oxidant, and distillate water as a solvent with and without polyvinylpyrrolidone as a surfactant. The prepared PPy and PPy/PVP adsorbents were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area, and Fourier Transform Infrared spectroscopy (FTIR). The results display BET surface area equals 7.88 and 21.93 for PPy and PPy/PVP, respectively. The data also shows that PPy/PVP acts as flawless adsorbent for the removal of copper and iron ions from aqueous solution with sequestration percentage of 90% and 83% in 2 hours respectively.

Abstract: This research has focused on the fabrication of a urea biosensor based on electrically conducting poly (pyrrole-co-para-phenylenediamine) (PPy-co-PPD). High amount of free amino groups (-NH₂), originating from PPD, in the PPy-co-PPD structures made them suitable for chemical immobilization of urease. The PPy-co-PPD films were prepared by one-step electrodeposition of the mixture of pyrrole and PPD. It was found that the morphology and conductivity of the PPy-co-PPD films were influenced by amount of PPD in the copolymer. Increasing amount of PPD in the copolymer led to decreasing electrical conductivity. Greater particle size and less packing were observed for the copolymer with high PPD content. XPS revealed the existence of free amino groups (-NH₂) on the surface of PPy-co-PPD films. The PPy-co-PPD films were further subjected for covalent immobilization of urease, selective catalytic enzyme for urea. Potentiometric responses of the PPy-co-PPD films showed the highest sensitivity of 47.3-54.2 mV/pUrea (r² > 0.99) over the urea concentration ranging from 0.5-10.0 mM (pUrea 2.0-3.3). Detection limits and response linearity were in the normal range of urea level. Response time was approximately 10 seconds. Leaching test revealed that the PPy-co-PPD film showed 83% reduction of urease leaching out of the PPy-co-PPD film during measurement, compared to the PPy film.

Abstract: Cyclic voltammetry can be used to investigate the chemical reactivity of species ion via oxidation and reduction process. The purpose of this study is to determine the level energy of high occupied molecule orbital (HOMO) and low unoccupied molecule orbital (LUMO) in polythiophene (PT), Poly (3-thiophene acetic acid) (P3TAA), polypyrrole (PPY) and chlorophyll (Chlo) through oxidation and reduction of molecular ions by cyclic voltammetry method. PT, P3TAA, PPY and Chlo solutions were prepared in a solvent of acetonitrile at the concentration range of 10^-2 to 10^-4 M. The current-voltage measurements for these solutions are performed using cyclic voltammetry method on input voltage from -2.0 V to 2.0 V. The working electrode used is indium tin oxide (ITO). The result of voltammogram is showed that the activity of PT species were produced three oxidation and one reduction processes. The formal reduction potential, E^o_¢ is 0.83 (positive) meaning that oxidation process was dominant. So that the reaction of PT species was exhibited irreversible electrochemical behavior. The reaction of P3TAA species was exhibited reversible electrochemical behavior, where the range value of oxidation, DE_pa and reduction, DE_pc were in range of 0.825 V to 1.120 V and -0.230 V to 0.131 V respectively. PYY species reaction was exhibited irreversible electrochemical behavior where two oxidation states occur within -0.145 V to -0.202 V and 0.870 V to 1.63 V respectively. The species activity of Chlo was exhibited irreversible electrochemical behavior where only the oxidation process was obviously appeared at range of 0.80 V to 0.95 V. The LUMO energy levels of PT, P3TAA PPY and Chlo were 5.84 eV, 5.34 eV, 1.10 eV and 3.85 eV respectively, while HOMO energy levels of PT, P3TAA PPY and Chlo were 4.61 eV, 4.25eV, 3.70 eV and 5.93 eV. The average value of energy gap of PT, P3TAA, PPY and Chlo were 1.23 eV, 1.08 eV, 2.23 eV and 1.10 eV respectively.