BF3-doped polyaniline: A novel conducting polymer

We review the unusual structural, transport and magnetic properties of highly conducting polyaniline, doped with boron trifluoride. Our studies establish the unique conducting state of this system, which is in distinct contrast with the conventional proton-doped polyaniline samples.     

Electrochemical synthesis and characterization of a new conducting polymer: Polyrhodanine

An antimicrobial drug, rhodanine (Rh), was electrochemically polymerized on a Pt electrode using cyclic voltammetry (CV). The high quality and homogeneous polyrhodanine (pRh) films with a dark-purple color were obtained. The chemical structure characterization was investigated by Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy techniques. Further, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques used to investigate thermal properties of the film. It is found that thermal stability of pRh films is relatively high. It is also observed that tetrahydrofurane (THF) and N-methyl-2-pyrrolidone (NMP) are good solvents for the polymer.     

Polymerization of aniline on bacterial cellulose and characterization of bacterial cellulose/polyaniline nanocomposite films

Bacterial cellulose/polyaniline nanocomposite film was prepared by the chemical oxidative polymerization of aniline with bacterial cellulose. Polyaniline conducting polymer nanocomposite films with bacterial cellulose fibers was prepared and characterized. In nanocomposite film, the bacterial cellulose was fully encapsulated with polyaniline by direct polymerization of the respective monomers using the oxidant and dopant. These bacterial cellulose/polyaniline nanocomposite films materials exhibited the inherent properties of both components. The deposition of a polyaniline on the bacterial cellulose surface was characterized by SEM. XPS revealed a higher doping level of the nanocomposite films doped with p-TSA dopant. From the cyclic voltammetry results, the polyaniline polymer was thermodynamically stable because redox peaks of electrochemical transitions in the voltagrams were maintained in bacterial cellulose/polyaniline nanocomposite films.     

Preparation, characterization, and photocatalytic properties of silver carbonate

Silver carbonate (Ag₂CO₃) short rods were prepared using a precipitation method. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflective spectra (DRS) and photocatalytic degradation of organic pollutants and destruction of E. coli measurements. The results of DRS suggested that the optical transition of Ag₂CO₃ was indirectly allowed, and its band gap was determined to be 2.08 eV. The prepared Ag₂CO₃ displayed a high activity towards degradation of phenol and MB under visible light. The total organic carbon (TOC) value decreased during the photocatalytic process, which suggests that phenol was truly photodegraded. The stability of Ag₂CO₃ was greatly improved when Na₂CO₃ was added into the photocatalytic system. In addition, Ag₂CO₃ displayed enhanced photocatalytic activities for the destruction of E. coli due to its photogenerated electron-hole pairs.     

Preparation and characterization of Ag/ZnO composites via a simple hydrothermal route

Silver/zinc oxide (Ag/ZnO) composites were fabricated by a facile one-pot synthesis method under hydrothermal conditions. By choosing glucose as the reductant, metal Ag was fabricated from Ag₂O with the growth of the crystalline ZnO. Structure measurements revealed that obtained Ag/ZnO composites comprised wurtzite ZnO and face-centered cubic structure of nanosized Ag, which uniformly distributed in the composites. Moreover, the morphology of the ZnO was varied regularly with the formation of Ag nanoparticles from flower-like to rod-like and finally returned to flower-like. The optical properties of UV–Vis and surface-enhanced Raman scattering spectra of the composites as well as effects of the dimension of metal Ag fabricated during the prior period of reaction on the morphology of ZnO were discussed.     

Fabrication and characterization of silver/titanium dioxide composite nanoparticles in ethylene glycol with alkaline solution through sonochemical process

This paper aims to study fabrication and characterization of silver/titanium oxide composite nanoparticle through sonochemical process in the presence of ethylene glycol with alkaline solution. By using ultrasonic irradiation of a mixture of silver nitrate, the dispersed TiO₂ nanoparticle in ethylene glycol associated with aqueous solution of sodium oxide yields Ag/TiO₂ composite nanoparticle with shell/core-type geometry. The powder X-ray diffraction (XRD) of the Ag/TiO₂ composites showed additional diffraction peaks corresponding to the face-centered cubic (fcc) structure of silver crystallization phase, apart from the signals from the cores of TiO₂. Transmission electron microscopy (TEM) images of Ag/TiO₂ composites, which average particle size is roughly 80 nm, reveal that the titanium oxide coated by Ag nanoparticle with a grain size of about 2–5 nm. Additionally, the formation of silver nanoparticles on TiO₂ was monitored by ultraviolet visible light spectrophotometer (UV–Vis). As measured the optical absorption spectra of as-synthesized Ag nanoparticle varying with time, the mechanism of surface formatting silver shell on the cores of TiO₂ could be explored by autocatalytic reaction; the conversion of Ag particle from silver ion is 98% for the reaction time of 1000 s; and the activity energy of synthesizing Ag nanoparticles on TiO₂ is 40 kJ/mol at temperature ranging from 5 to 25 °C. Hopefully, this preliminary investigation could be used for mass production of composite nanoparticles assisted by ultrasonic chemistry in the future.     

Fabrication of ionic polymer actuator with graphene nanocomposite electrodes and its characterization

In the present study, a novel ionic polymer actuator employing a graphene nanocomposite (GN) as its electrodes was fabricated. By a conventional solvent mixing of a graphene nanopowder and polystyrene, a GN solution was prepared. The solution was then utilized in a dip coating process of an ionic polymer membrane, forming a thin liquid GN layer on the surfaces of the ionic polymer membrane. After removing the solvent from the coated film, the solidified conducting GN layer could be obtained, which was used as the electrodes in the ionic polymer actuator. An electrical property of the GN layer formed by the present method was characterized, confirming the possibility of the present GN in the actuator applications. Simple and reverse bending motions of the fabricated actuator were also investigated, verifying the usefulness of both the GN layer and the present simple fabrication method.     

A new visible photoluminescence in the conducting Ta-Si-N nanocomposite thin films

The conventional visible photoluminescence (PL) behavior at room temperature (RT) is observed in the semiconducting or insulating nanostructured materials with large bandgaps. Here, we have demonstrated the visible-color PL behavior at RT of the conducting Ta-Si-N thin films nanocomposite using simple magnetron sputtering without any post annealing. X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) depth profile results evidence that the microstructure of conducting Ta-Si-N with a low resistivity of 220-375 μΩ cm exhibits (Ta_x,Si_y)N nanocrystalline grains embedded in an amorphous matrix, which can emit the distinct PL intensity from 390 to 750 nm wavelengths. No PL is detected in the coarse-grain polycrystalline films. Qin's extended quantum confinement/luminescence center model [G.G. Qin, Mater. Res. Bull. 33 (1998) 1857-1866] was adopted and modified to discuss the RT PL mechanism in the conducting Ta-Si-N films using three types of competitive photoexcitation/photoemission processes.     

Critical current in silver clad Y-Ba-Cu-O superconducting wires

Silver clad wires of highT _c superconductor Y₁Ba₂Cu₃O_7−x have been fabricated through the powder metallurgy technique. The reacted wires show a midpointT _c of 84K. A critical current density of 26·4 A cm⁻² (77K, 0T) is obtained in these wires. The wires, however, turn complete normal only at a current density of 280 A cm⁻². The reasons for low critical current density obtained in these wires are discussed.     

Transport, structural and thermal studies on nanocomposite polymer blend electrolytes for Li-ion battery applications

Nanocomposite polymer electrolytes (NCPEs) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP) as a host polymer, Poly(vinyl acetate) (PVAc) as an additive, Ethylene Carbonate (EC) as a plasticizer, Lithium Perchlorate as dopant salt and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. Thermal stability of the sample having maximum ionic conductivity was found using TG/DTA analysis. Nano composite polymer electrolytes were subjected to ac impedance analysis spectra for acquiring the ionic conductivity values at different temperature. Surface structure of the sample was analysed using scanning electron microscope and the complexations of samples were analysed using X-ray diffraction analysis. It was noted that the polymer electrolyte contains 8 wt. % of BaTiO₃ showed maximum ionic conductivity than the other ratios of BaTiO₃.     

AC conductivity and relaxation behavior in ion conducting polymer nanocomposite

We report the ac conductivity and relaxation behavior analysis for a heterogeneous polymer–clay nanocomposite (PNC) having composition (polyacrylonitrile)₈LiCF₃SO₃ + x wt.% dodecylamine modified montmorillonite. Charge transport behavior in an ionically conducting PNC has been analyzed systematically and correlated with the macroscopic parameters like polymer glass transition temperature and available free mobile charge carriers. Intercalation of cation coordinated polymer into the nanometric clay channels has been confirmed by high-resolution transmission electron microscopy. The electrical properties of the intercalated PNC films have been studied using complex impedance/admittance spectroscopy. Excellent correlation of relaxation behavior with polymer glass transition temperature (T _g) confirmed the objectives of the work. An analysis of dielectric relaxation indicates that PNC films are lossy when compared with polymer–salt film. This result is a direct outcome of faster ion dynamics leading to strong electrode polarization effect due to the accumulation of charge carriers at the interface.     

Optical investigations of conducting polypyrrole under pressure

Abstract

The changes in the characteristics of vibrational and optical properties of the conducting form of polypyrrole under pressure is studied.     

Preparation and antibacterial effect of silver-hydroxyapatite/titania nanocomposite thin film on titanium

The composite which contains Ag⁺ and nanosized hydroxyapatite with TiO₂ was deposited onto titanium by dipping method. The morphology, chemical components and structures of the thin film were characterized by XRD, scanning electronic microscope (SEM) and energy dispersive X-ray analysis (EDX). Staphylococcus aureus and Escherichia coli were utilized to test the antibacterial effect. XRD results demonstrated that the films have characteristic diffraction peaks of pure HA. EDX results showed that the deposited films consisted of Ca, P, Ti, O and Ag, all of which distribute uniformly. With regard to the antibacterial effect, 98% of S. aureus and more than 99% of E. coli were killed after 24 h incubation and pictures of SEM showed obviously fewer cells on the surface with coating.     

Fabrication of silver nanoparticles deposited on boehmite sol for surface enhanced Raman scattering

The composite consisting of silver nanoparticles deposited on boehmite hybrid was synthesized by NaBH₄ reduction technique. The morphology of the composite was studied by TEM, UV/Vis spectrophotometer and particle sizer. The size of the silver nanoparticles deposited on the surface of the boehmite ranged from 10 nm to 100 nm. The contact of silver nanoparticles increased by means of deposition of silver nanoparticles on the boehmite sol and the aggregation of the composites. This leads to the appearance of a shoulder at 450 nm in the UV-Vis absorption spectra with the addition of 0.15 mg and 1.5 mg boehmite. It was found that the intensity of the SERS in the case of the composite was higher than for silver colloids consisting of a concentration of silver greater than 3.2 mM.     

Preparation of silver nanoparticles by laser ablation in polyvinylpyrrolidone solutions

We performed laser ablation of a silver plate in polyvinylpyrrolidone (PVP) aqueous solutions to prepare silver nanoparticles. Secondary laser irradiation onto the prepared colloidal solutions was also carried out. It was revealed that the formation efficiency was increased by addition of PVP as well as the stability of nanoparticles. The result of shadowgraph measurements suggested that the increased ablation efficiency by PVP is attributable to increased secondary etching efficiency by the solvent-confined plasma toward the silver plate. On the other hand, the size decrease of the nanoparticles by addition of PVP was more remarkable during the secondary irradiation process than in the laser ablation (nanoparticle preparation) process. This result indicates that emitted materials interact less sufficiently with PVP molecules in the laser ablation process than in the secondary laser irradiation process.     

Preparation and photocatalytic properties of silver nanoparticles loaded on CNTs/TiO2 composite

In this study, new nanoscale photocatalyst based on silver and CNTs/TiO₂ was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO₂ was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO₂ increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO₂ for dye degradation was nearly 1.2 times than that of CNTs/TiO₂, which indicated decorating Ag nanoparticles on CNTs/TiO₂ could enhance the photocatalytic ability.     

Preparation of poly-o-phenylenediamine/TiO2/fly-ash cenospheres and its photo-degradation property on antibiotics

A series of poly-o-phenylenediamine/TiO₂/fly-ash cenospheres(POPD/TiO₂/fly-ash cenospheres) composites have been prepared from o-phenylenediamine and TiO₂/fly-ash cenospheres under various polymerization conditions. The properties of the samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), specific surface area (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance spectrum (UV-vis DRS). Photocatalytic activity was studied by degradation of antibiotics waste water under visible light. The results indicate that the photo-induced method is viable for preparing modified photocatalysts, and the modified photocatalysts have good absorption in visible light range. The photocatalysts of POPD/TiO₂/fly-ash cenospheres which have good performance are prepared at pH 3 and 4, and the polymerized time around 40 min. When the photocatalysts are prepared under the conditions of pH 3 and polymerized time 40 min, the degradation rate of roxithromycin waste water could reach near 60%, and it indicates that the way of POPD modified TiO₂/fly-ash cenospheres to degrade the antibiotics waste water is viable.     

Preparation and characterization of SiO2/ZrO2/Ag multicoated microspheres

A new type of multicoated silica/zirconia/silver (SiO₂/ZrO₂/Ag) core-shell composite microspheres is synthesized in this paper. In the process, ZrO₂-decorated silica (SiO₂/ZrO₂) core-shell composites were firstly fabricated by the modification of zirconia on silica microspheres through the hydrolysis of zirconium precursor. Subsequently, on SiO₂/ZrO₂ composite cores, silver nanoparticles were introduced via ultrasonic irradiation and acted as “Ag seeds” for the formation of integrate silver shell by further reduction of silver ions using formaldehyde as reducer. The resulting samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared, energy-dispersive X-ray, and UV-vis spectroscopy, indicating that zirconia and silver layers were successfully coated on the surfaces of silica microspheres.     

高压下某些导电高分子色散关系的研究

利用晶格动力学方法,研究在高压下几种导电高分子具有不同晶格链时的色散关系及其曲线的变化.链间耦合作用的减弱使横波与纵波的ω差值相应增大,且在BZ边界处拉开一个间隙,这是维度作用的结果.