Electrical field influence on molecular mass and electrical conductivity of polyaniline

We have described the primary studies on the conductivity and molecular weight of polyaniline in an electric field as it is used in a field effect experimental configuration. We report further studies on doped in-situ deposited polyaniline. First we have chemically synthesized polyaniline by ammonium peroxodisulfate in an acidic solution, with aqueous, organic and emulsion conditions at different times. Next, we measured mass and conductivity and obtained the best time of polymerizations. Then, we repeated these reactions under different electrical fields in constant time and measured mass and conductivity. The polyaniline is characterized by gel permeation chromatography (GPC), UV-visible spectroscopy and electrical conductivity. Polyanilines with high molecular weight are synthesized under electric field M _w = (5.2–6.8) × 10⁵, with M _w/M _n = 2.0–2.5. The UV-visible spectra of polyanilines oxidized by ammonium peroxodisulfate and protonated with dodecylbenzenesulfonic acid (PANi-DBSA), in N-methylpyrolidone (NMP) show a smeared polaron peak shifted into the visible. Electrical conductivity of polyaniline has been studied by four-probe method. The conductivity of the films of emeraldine protonated by DBSA cast from NMP is higher than 500 S/cm under (10 kV/cm² of potential) electric field and shows an enhanced resistance to ageing. Next, we carried chemical polymerization at the best electric field at different times. Finally, the best time and amount of electric field were determined. Polymers synthesized under an electric field probably have better physical properties regarding the existence of less branching and high electric conductivity.     

Comprehensive study of nanostructured supports with high surface area for Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure γ-alumina, single wall carbon nanotubes (SWNTs), and the hybrid of SWNTs/nanostructure γ-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer-Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions (220–240 °C, 15–25 bar, H₂/CO ratio of 2, GHSV of 900–1400) in order to study the effects of temperature, pressure and gas hourly space velocity (GHSV) changes on hydrocarbon selectivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP), hydrogen (H₂) chemisorption and temperature-programmed reduction (TPR). The results showed that the yield of hybrid supported catalyst (55.4%) is higher than that of nanostructure γ-alumina supported catalyst (55.0%) and lower than that of SWNTs supported cobalt catalyst (71.0%). The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selectivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.     

Development of deep eutectic solvent–based microwave-assisted extraction combined with temperature controlled ionic liquid–based liquid phase microextraction for extraction of aflatoxins from cheese samples

In this study, for the first time, a deep eutectic solvent-based microwave-assisted extraction was combined with ionic liquid–based temperature controlled liquid phase microextraction for the extraction of several aflatoxins from cheese samples. Briefly, the analytes are extracted from cheese sample (3 g) into a mixture of 1.5 mL choline chloride:ethylene glycol deep eutectic solvent and 3.5 mL deionized water by exposing to microwave irradiations for 60 s at 180 W. The liquid phase was taken and mixed with 55 μL 1-hexyl-3-methylimidazolium hexafluorophosphate. By cooling the solution in the refrigerator centrifuge, a turbid state was obtained and the analytes were extracted into the ionic liquid droplets. The analytes were determined by high-performance liquid chromatography equipped with fluorescence detector. Low limits of detection (9–23 ng kg^–1) and quantification (30–77 ng kg^–1), high extraction recovery (66%–83%), acceptable enrichment factor (40–50), and good precision (relative standard deviations ≤ 5.2%) were obtained using the offered approach. These results reveal the high extraction capability of the method for determination of aflatoxins in the cheese samples. In this method, there was no need for organic solvents and it can be considered as green extraction method.     

Synthesis of imidazo[1,2-a]pyridine-6-carbohydrazides and 1H-pyrido[1,2-a]pyrimidine-7-carbohydrazides

The one-pot, multicomponent synthesis of imidazopyridine and pyridopyrimidine fused heterocyclic systems from readily available diamines, l,l-bis(methylthio)-2-nitroethene, cyanoacetohydrazide and aromatic aldehydes in good to high yields is described. This protocol has the advantages of simple work-up, mild reaction conditions, absence of catalyst and provides an entry point to fused heterocyclic structures.     

Band structure of tetragonal BaTiO <Emphasis Type="Bold">3</Emphasis>

The electronic structure, total density of states DOS and electronic density in ferroelectric tetragonal crystal BaTiO₃ are studied using WIEN2k package. This employs the full potential-linearized augmented plan wave FP-LAPW method in the framework of the density functional theory DFT with the generalized gradient approximation (GGA). The results show an indirect band gap of 2.30 eV at the Γ point in the Brillouin zone. The calculated band structure and density of states of BaTiO₃ agree with the previous experimental and theoretical results, as do the charge distribution and the prediction of the nature of the chemical bonding. Received 11 December 2002 / Received in final form 3 February 2003 Published online 1st April 2003 RID="a" ID="a"e-mail: salehihamid@yahoo.com     

Effect of ion and negative ion temperatures on KdV and mKdV solitons in a multicomponent plasma

The formation of ion-acoustic solitons (IASs) in an unmagnetized plasma with negative ions has been investigated through the KdV equation in both the situations \(Q^{\prime}\left( { = m_{j} /m_{i} = {\text{negative}}\;{\text{to}}\;{\text{positive}}\;{\text{ion}}\;{\text{mass}}\;{\text{ratio}}} \right)\) less and greater than one and the mKdV equation only for \(Q^{\prime} > 1\). The existence of both KdV and mKdV solitons has been established for \(\alpha \left( { = {\text{ion}}\;{\text{to}}\;{\text{electron}}\;{\text{temperature}}\;{\text{ratio}}} \right)\; > \;\beta \left( { = {\text{negative}}\;{\text{ion}}\;{\text{to}}\;{\text{electron}}\;{\text{temperature}}\;{\text{ratio}}} \right)\) and \(\alpha < \beta\), which is the new outcome of the current investigation. Furthermore, the existence of both compressive and rarefactive solitons for \(Q^{\prime} > 1\) and \(Q^{\prime} < 1\) has been demonstrated.

     

Linking Composition,Structure and Thickness of CoOOH layers to Oxygen Evolution Reaction Activity by Correlative Microscopy

The role of β-CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X-ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure–activity relationships of various faceted β-CoOOH formed on a Co microelectrode under OER conditions. We reveal that ≈6 nm β-CoOOH(01 0), grown on [ 0]-oriented Co, exhibits higher OER activity than ≈3 nm β-CoOOH(10 3) or ≈6 nm β-CoOOH(0006) formed on [02 - and [0001]-oriented Co, respectively. This arises from higher amounts of incorporated hydroxyl ions and more easily reducible Co^III−O sites present in β-CoOOH(01 0) than those in the latter two oxyhydroxide facets. Our correlative multimodal approach shows great promise in linking local activity with atomic-scale details of structure, thickness and composition of active species, which opens opportunities to design pre-catalysts with preferred defects that promote the formation of the most active OER species.