Visual sensing of picric acid in 100% aqueous media based on supramolecular polythiophene assemblies with colorimetric and fluorescent dual response

A colorimetric and fluorometric dual probe based on a water-soluble polythiophene derivative (PMTPBA) was designed and synthesized. It can be applied to determination of picric acid (PA) in 100% aqueous solution. The approach relies on the formation of supramolecular polythiophene assemblies in the presence of PA through electrostatic, charge transfer and π-π stacking interactions. This probe could be utilized for the rapid and visual detection of PA both in aqueous solution and solid support with high specificity and sensitivity. The detection limit of this sensor is as low as 5.0 × 10^-8 mol/L.     

Structural and electrochemical properties of polythiophene

Polythiophenes (PTs) were prepared by chemical oxidative polymerization method in presence and absence of three different (cationic - CTAB, anionic - SDS and non-ionic - Triton X-100) surfactants using FeCl₃ as oxidant. The prepared PTs were characterized by FT-IR, UV-Vis, XRD, SEM and cyclic voltammetry studies. The FT-IR spectra inferred the polymerization of thiophene and elucidate the corresponding functional groups of PTs. Our results on the UV-Vis spectra demonstrate the n−π* electronic transition of the conjugated molecules. Further the red shift in the absorption peak confirms the longer conjugation length of PTs. The amorphous nature of the PTs was inferred from the XRD pattern. The PTs prepared with surfactant exhibited different morphology compared to PT prepared without surfactant. The specific capacitances (SC) of the prepared PTs were calculated using cyclic voltammetry technique, the PT prepared with TRITRON X-100 exhibited higher SC of 117 F/g compared to SC of surfactant free PT (78 F/g). Hence, the PTs prepared with surfactants were found to be suitable electrode materials for redox supercapacitors.     

A study of inelastic electron-phonon interactions on tunneling magnetoresistance of a nano-scale device

In this research, we have studied the effect of inelastic electron-phonon interactions on current-voltage characteristic and tunneling magnetoresistance of a polythiophene molecule that is sandwiched between two cobalt electrodes using modified Green's function method as proposed by Walczak. The molecule is described with a modified Su-Schrieffer-Heeger Hamiltonian. The ground state of the molecule is obtained by Hellman-Feynman theorem. Electrodes are described in the wide-band approximation and spin-flip is neglected during conduction. Our calculation results show that with increase in voltage the currents increase and tunneling magnetoresistance decreases. Change in tunneling magnetoresistance due to inelastic interactions is limited in a small bias voltage interval and can be neglected in the other bias voltages.     

β-双取代和β，β＇-取代可溶性导电聚噻吩的合成与表征

自上世纪90年代，Burroughes等人首次报道导电聚合物材料PPV（poly-p-phenylene vinylene）的发光性能后，聚合物发光研究获得了迅猛的发展。聚噻吩类聚合物因具有良好的稳定性和较高的发光活性而受到了人们广泛的关注。由于取代基的不同，聚噻吩类衍生物的发光颜色和发光强度均不相同，因此合成新型材料始终是这一领域的热点和基础工作。Yoshino等人以无水FeCl3为催化剂合成可溶性取代聚噻吩的方法，因条件温和，反应易控制，产率较高而被学术界广泛采用。我们参考并改进该方法成功地合成了β-取代聚噻吩的基础上，进一步合成了β，β’-双取代聚噻吩，以期在改变聚合物链性能的同时，调控并改善聚合物光、电性能。本文介绍了其中四种材料的合成方法、表征结果及光学性能的初步研究结果。     

Stabilization of Film Morphology in Polymer‐Fullerene Heterojunction Solar Cells

Abstract

The fixation of film morphology is essential for the long‐term stability of heterojunction polymer photovoltaic (PV) cells. An epoxy‐functionalized fullerene C₆₀ derivative was synthesized for this purpose. This material can be polymerized at acidic conditions and was found to stabilize the phase‐separated morphologies within blended polythiophene–fullerene heterojunction films. The phase stability of the films was characterized by UV‐VIS spectroscopy and optical microscope. Crosslinkable polythiophene derivatives were also prepared but these materials were much less effective in stabilizing film morphology when mixed into PCBM (C61‐butyric acid methyl ester). Heterojunction polymer PV cells were prepared from these materials and their performance was compared with cells made from conventional materials.     

Some Novel Conducting Polythiophene Derivatives: Theoretical Analysis,Synthesis, Characterization and Electroreological Properties

A series of alternating phylene and symmetrically bithiophene containing repeat units and the respective homopolymers have been synthesized and characterized by combining FTIR, UV-Vis spectroscopy, four probe conductivity measurement, TGA and SEM analysis. Quantum mechanical calculations of the structures and infrared spectra of the monomers and respective dimers were compared with experimental results. The polymers are soluble in N-methyl-pyrrolidone (NMP). The samples have conductivities of 10^?5 S/cm levels. Thermal degradation analysis results indicated that poly-bithiophene derivatives have higher thermal stabilities than poly-monothiophene derivatives. All samples exhibited different surface morphologies. The electrorheological (ER) properties of polymer suspensions in silicone oil were prepared and ER behavior was investigated as a function of shear rate, electric field strength and frequency.     

Simultaneous electrochemical immunosensor based on water-soluble polythiophene derivative and functionalized magnetic material

A novel, sensitive electrochemical immunosensor for simultaneous determination of squamous cell carcinoma associated antigen (SCC-Ag) and carcinoembryonic antigen (CEA) for the combined diagnosis of cervical cancer was designed. The amplification strategy for electrochemical immunoassay was based on poly[3-(1,1′-dimethyl-4-piperidine-methylene) thiophene-2,5-diylchloride] (PDPMT-Cl) and functionalized mesoporous ferroferric oxide nanoparticles (Fe₃O₄ NPs). PDPMT-Cl dispersed in chitosan solution with enhanced electrical conductivity and solubility was used as matrices to immobilize the first antibodies. Different redox probes (thionine (Th) and ferrocenecarboxylic acid (Fca)) functionalized Fe₃O₄ NPs incubated with two kinds of secondary antibodies to fabricate the labels. Using an electrochemical analysis technique, two well-separated peaks were generated by Th and Fca, making the simultaneous detection of two analytes on the electrode possible. Under optimized conditions, this method showed wide linear ranges of three orders of magnitude with the detection limits of 4 pg mL⁻¹ and 5 pg mL⁻¹, respectively. The disposable immunosensor possessed excellent clinical value in cervical cancer screening as well as convenient point-of-care diagnostics.     

Electrochemical Characterization of Chemically Synthesized Polythiophene Thin Films: Performance of Asymmetric Supercapacitor Device

Polythiophene (PT) thin films have been prepared by chemical bath deposition (CBD) method at room temperature (300 K) via oxidative polymerization of thiophene using ammonium peroxodisulfate (APS) as an oxidizing agent. Globular particulates of PT are deposited on the stainless steel and glass substrates. The morphology and chain structure of PT are studied using scanning electron microscopy (SEM) and Raman spectroscopy techniques, respectively. The electrochemical behavior of PT electrode is studied using cyclic voltammetry and galvanostatic charge? discharge studies. PT thin film shows maximum specific capacitance of 300 F g^?1 at 5 mV s^?1 in 0.1 M LiClO₄/PC electrolyte. The asymmetric device formed with PT and graphite shows supercapacitive properties useful in the power applications.