Papers by Keyword: Polythiophene

Abstract: A novel humidity sensing composite was synthesized using polythiophene (PTh) and graphene oxide by chemical oxidation process. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and investigations on humidity sensing were used to characterize the samples. XRD pattern of PTh demonstrated that it is amorphous in nature. The flaky character and more compact structure of composites were both confirmed by scanning electron microscopy. These findings show that the thiophene monomer successfully polymerized on graphene's surface. Polythiophene/graphene composites were studied for their humidity sensing performance in the relative humidity (RH) range of 11% - 97%.

Abstract: Chemical oxidation reactions were used to create composite materials made of polythiophene (PTh) and reduced graphene oxide with varying compositions. To describe the samples, Fourier transform infrared spectroscopy (FTIR) was used. The hydroxyl (OH) stretching vibrations of the -COOH functional group and adsorbed H₂O molecules are responsible for the intense bands at 3386 cm^-1 and 1302 cm^-1. O-H vibrations can be attributed to absorption at a wavelength of 1610 cm^-1. C-S bending mode of thiophene ring has produced the peak at 666 cm^-1. The dielectric constant, tangent loss, and electric modulus with the applied AC frequency for the polythiophene/reduced graphene oxide composites were studied.

Abstract: This work demonstrates an alternative organic semiconductor-based ion sensor design, and effortless that avoids the use of membranes with sensitizer and separate compartments, unlike previous architecture. Instead, we simply dope an organic semiconductor with a specific sensitizer ionophore called valinomycin into a polythiophene casting solution that is used to manufacture organic thin-film transistors. Resulting OTFTs display near-Nernstian ion sensitivity of their threshold voltage within different potassium ion concentrations. The Nernstian ion sensitivity is 52±2 mV/dec, and the limit of detection is 15±5 μM.

Abstract: Retracted papers: One of the major features of conjugated polymer is the rigid molecular conformation which is absolutely different with that of flexible polymer. In this study, the non-conjugated aggregate structure of conjugated polymers was explored for the first time by using Small Angle X-ray Scattering (SAXS). It is found that there is a large-scale non-conjugated packing structure inside the Poly (3-alkylthiophene) (P3AT), which can be attributed to loose stacked structure of rigid conjugated main chain in P3AT. Thus, a large number of pore structures with the porosity of about 10^-4 to 10^-3 are formed, and such pore structures exhibit the characteristics of a mass fractal structure.

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.

Abstract: Molecular dynamics are applied to simulate molecular motions in an aqueous solution of two soluble derivatives of a 100-ring polythiophene chain – one with sidechains terminating in a SO₃^– group, the other in NMe₃⁺. Each chain is in a helical conformation defining a water-containing central channel along whose axis the dynamics of ions from the solution to the channel’s axial electrostatic potential is simulated. The profiles of these potentials distinguish the tendencies of the two channel species to occlude water molecules on their surfaces. Invoking the conductive polymer characteristics of polythiophene that can accomplish the transfer of electrons between the aromatic rings and redox reagents in the solution, the effect of this transfer on the axial potential and migration is followed. The electrostatic potential monitors differences in the association of the solvent molecules with the two species of helical polymer and shows that while Na⁺ and Cl^– ions do not enter the channel in the absence of the redox changes, an ion with a selected charge does so spontaneously when appropriate electric charge is transferred to the channel. This enables the selected ion to travel about 10 – 20Å in the channel without the application of an external electric field.

Abstract: Polythiophene was prepared by oxidation of thiophene. It was electronically doped with organic acceptors such as TCNE, TCNQ, DDQ, Chloranil and kI-I₂. The FTIR spectra revealed only little change of intermolecular band gap of about 0.21ev of polythiophene .However, polythiophene (pure) obtained from chemical company revealed degenerate semiconducting property. The electronic doping with the organic acceptors and kI-I₂ revealed optical properties in small polaron model in the FTIR range. Thus both non-degenerate and degenerate polythiophenes were studied with 60% doping of organic acceptors.

Abstract: In the article we present a unique analytical tool for the characterization of conjugated polymers – SEC-DAD (Size Exclusion Chromatography – Diode Array Detector). The chromatographic separation is performed in a conventional SEC mode which provides narrow molecular-weight fractions of the analyzed polymer. The uniqueness of the SEC-DAD combination comes out with the utilization of DAD for the monitoring the absorption characteristics of particular fractions along the molecular weight distribution. If applied in the characterization of the conjugated polymers, SEC-DAD helps to reveal the dependencies of (i) the extent of conjugation and (ii) covalent and configuration structure of the polymer on the molecular weight.

Abstract: Polythiophene(PTP)/microcrystal muscovite conductive composites were prepared by the method of intercalating polymerization via Fe³⁺-H₂O₂ catalytic oxidation system in water. The morphology, structures, electrical conductivity and thermal stability of composites have been studied preliminary. The influence of the different synthesis conditions (temperature, monomer ratio, reaction time) on the conductivity of composite materials was explored. The results of the FTIR and XRD confirmed that thiophene (TP) inserted into the layers of microcrystal muscovite to polymerize and formed intercalation compounds. TG analysis indicated the improved thermostability of composite materials. The PTP/microcrystal muscovite composite made from 2g/ml solution of microcrystal muscovite/TP with reacting for 12h and 15°C showed the highest conductivity 3.56 ×10^-5s/cm^-1.

Abstract: Two thiophene derivatives 4,4'-di (thiophen-2-yl) biphenyl and 4,4'-di (thiophen-2-yl) -2-nitrobiphenyl ,which were used as monomers for preparing poly (4,4'-di (thiophen-2-yl) biphenyl) (DPBT) and poly (4,4'-di (thiophen-2-yl)-2-nitrobiphenyl) (DPNT) by ferric chloride oxidation polymerization, were synthesized via Suzuki reaction with 4,4'-dibromobiphenyl as the raw material. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were recorded and used for calculating the band-gap (E_g), HOMO orbital energy (E_HOMO) and LUMO orbital energy (E_LUMO) of the polymers. The calculation results indicated that attaching an electron-withdrawing group such as-NO₂ to the main chain can lower band-gap and increase the maximum absorption wavelength.