Detecting organic vapors using a conductometric sensor prepared from Ardel®D-100 and graphite

The composites of graphite with Ardel^?D-100 which is a trademark of a polyester of bisphenol-A with terephthalic and isophthalic acid were used as a sensing material in a conductometric vapor sensor. The magnitudes of responses are increased in the order of benzene, isobutyl acetate, isoamyl acetate, ethyl benzene and chloro benzene. This suggests that Ardel^?D-100 can be used as a sensing material for chlorobenzene, ethyl benzene and isoamyl acetate. On the other hand, specific retention volumes of the sensed vapors on Ardel^?D-100 coated on graphite were determined by inverse gas chromatography at temperatures between 200 and 260 °C. The distribution coefficient, K _s of the vapors between stationary and mobile phases in the column was obtained. It was revealed for the first time that the logarithm of K _s of the solvents varies almost linearly with their responses based on conductometric resistance of the sensing polymer composite. Subsequently, the study suggests that gas chromatographic retention data can be used in prediction of the conductometric responses of a polymeric sensor to vapors. Correspondence: Ferdane Karaman, Department of Chemistry, Yildiz Technical University, 34220 Istanbul-Esenler, Turkey     

Polyethylenimine and tris(2-aminoethyl)amine modified p(GA–EGMA) microbeads for sorption of uranium ions: equilibrium,kinetic and thermodynamic studies

Poly(glycidyl methacrylate-ethyleneglycol dimethacrylate), p(GA–EGMA), microbeads were prepared through suspension polymerization. It was decorated with polyethylene imine (PEIM) and tris(2-aminoethyl)amine (TAEA) ligands to decorate with polyamine groups. These microbeads were used for sorption of uranium ions from aqueous solution. The maximum sorption of uranium ions on the PEIM and TAEA modified microbeads was observed at pH 6.0. The maximum sorption capacity of acid hydrolyzed p(GA–EGMA)–OH, p(GA–EGMA)–PEIM and p(GA–EGMA)–TAEA microbeads was found to be 7.21, 87.8 and 64.3 mg g^?1. The sorption process conforms to the pseudo-second order kinetic model and the Langmuir and Temkin isotherm models well.     

Gas chromatographic-mass spectrometric analysis of essential oils from Pimpinella aurea, Pimpinella corymbosa, Pimpinella peregrina and Pimpinella puberula gathered from Eastern and Southern Turkey

Essential oils from fruits, stems and leaves and roots of Pimpinella aurea DC., P. corymbosa Boiss., P. peregrina L. were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques. Fruits and aerial parts of P. puberula (DC.) Boiss were also evaluated. A total of 140 different compounds were identified, and significant qualitative and quantitative differences were observed among the samples. In fact, the main constituents of each species were different and only the oils extracted from roots shared the same principal compound, epoxy pseudoisoeugenyl-2-methyl butyrate (26.8-42.8%). The other fractions were dominated by different sesquiterpene compounds although in three of them, P. aurea stem and leaves, P. puberula fruits and P. puberula stems and leaves, monoterpene constituents also appear as main ones.     

Biodegradation of methylene blue and carbaryl by Trametes versicolor laccase preparations in the presence of a mediator compound

Laccase from Trametes versicolar was immobilized on to acrylate based microbeads carrying epoxy or carbonate groups. The amounts of immobilized enzyme on the carbonate and epoxy groups were 24.6 and 9.7?mg/g, respectively. In the presence of a mediator (i.e., acetosyringone) almost 100% biodegradation was observed for both Methylene Blue dye (MB) and Carbaryl pesticide (CP) by the immobilized laccases, while in the absence of mediator, 63 and 71%, respectively. The immobilized enzyme was operated in a fluidized bed reactor for biodegradation of MB and CP for 24?h, and the initial activity lost was only 8.0 and 2.0%, respectively. The data show that the immobilized enzyme can effectively be utilized for complete degradation of organic pollutants in wastewaters.     

Improved diode properties in zinc telluride thin film-silicon nanowire heterojunctions

In this study, structural and optoelectronic properties and photodedection characteristics of diodes constructed from p-zinc telluride (ZnTe) thin film/n-silicon (Si) nanowire heterojunctions are reported. Dense arrays of vertically aligned Si nanowires were successfully synthesized on (1 1 0)-oriented n-type single crystalline Si wafer using simple and inexpensive metal-assisted etching (MAE) process. Following the nanowire synthesis, p-type ZnTe thin films were deposited onto vertically oriented Si nanowires via radio frequency magnetron sputtering to form three-dimensional heterojunctions. A comparative study of the structural results obtained from X-ray diffraction and Raman spectroscopy measurements showed the improved crystallinity of the ZnTe thin films deposited onto the Si nanowire arrays. The fabricated nanowire-based heterojunction devices exhibited remarkable diode characteristics and enhanced optoelectronic properties and photosensitivity in comparison to the planar reference. The electrical measurements revealed that the diodes with nanowires had a well-defined rectifying behaviour with a rectification ratio of 10⁴ at ±2 V and a relatively small ideality factor of n = 1.8 with lower reverse leakage current and series resistance at room temperature in dark condition. Moreover, an open-circuit voltage of 100 mV was also observed under illumination. Based on spectral photoresponsivity measurements, the nanowire-based device exhibited a distinct responsivity and high detectivity in visible and near-infrared (NIR) wavelength regions. The device characteristics observed here offer that the fabricated ZnTe thin film/Si nanowire-based p–n heterojunction structures will find important applications in future and will be a promising candidate for high-performance and low-cost optoelectronic device applications, NIR photodedectors in particular.     

Magnetic line source diffraction by a conductive half-plane in an anisotropic plasma

An integral theory that is associated with the scattered fields is considered for the solution of H-polarized line source diffraction by a conductive half-plane, which is surrounded by an anisotropic plasma. As the anisotropy does not affect an E-polarized incident wave, only one polarization case is considered. The cold plasma medium is characterized by the dielectric tensor. The constant external magnetic field producing the anisotropy in a cold plasma is applied parallel to the edge of the half-plane. The total, scattered, and diffracted waves are derived in terms of the Fresnel functions. Therefore, finite magnitude values at the transition boundaries are obtained. The wave behaviours are investigated numerically for different quantities of the medium.     

Ce0.8Sm0.2O1.9 synthesis for solid oxide fuel cell electrolyte by ultrasound assisted co-precipitation method

In this study, the synthesis of Ce_0.8Sm_0.2O_1.9 (SDC) solid electrolyte by the ultrasound assisted co-precipitation method was accomplished to explore the effects of ultrasound power, ultrasound pulse ratio and probe type upon the ionic conductivity of SDC as well as the lattice parameter, the microstructure and the density. Fine powders of uniform crystallite sizes (average 11.70 ± 0.62 nm) were obtained, needing lower sintering temperature. The SDC powders were successfully sintered to a relative density of over 95% at 1200 °C (5 °C min^?1) for 6 h. The micrograph of SDC pellets showed non-agglomerated and well-developed grains with average size of about 200 nm. X-ray diffraction analysis showed that the lattice parameter increased with increasing acoustic intensity and reached a maximum for the 14.94 W cm^?2. Further, a linear relationship was detected between the lattice parameter and the ionic conductivity, inspiring a dopant like effect of US on the electrolyte properties. The highest ionic conductivity as σ_800°C = 3.07 × 10^?2 S cm^?1 with an activation energy E_a = 0.871 kJ mol^?1 was obtained with pulsed ultrasound for an acoustic intensity of 14.94 W cm^?2, using 19 mm probe and 8:2 pulse ratio.     

Scattering of plane-waves by an impedance half-plane at the interface between isorefractive media

The scattering of plane waves by an impedance half-plane located at the interface of two isorefractive media is investigated. The scattered field, in addition to the diffracted and geometrical optics fields, is analyzed numerically and compared to the scattered field of perfectly conducting half-plane. The effect of the isorefractive media on the scattered field is also examined.     

A new high‐performance blue to transmissive electrochromic material and use of silver nanowire network electrodes as substrates

Synthesis of a novel, high‐performance blue to transmissive switching electrochromic material is described. The polymer (P1) was prepared by both electrochemical ( P1E ) and chemical ( P1C ) means from the corresponding monomer. The electrochemically synthesized polymer ( P1E ) revealed 64% optical contrast change (on ITO) in the visible region and very fast switching times of 0.32 s (coloration) and 0.90 s (bleaching). On the other hand, the chemically synthesized, solution processable polymer ( P1C ) also showed a high optical contrast value (49%, on ITO) with very fast switching times of 0.86 s for coloration and 0.57 s for bleaching. These high optical contrast values coupled with fast switching times place these materials along with high‐performance blue to transmissive electrochromic polymers. Significantly, these improved characteristics were achieved by side chain engineering of a known, inferior blue to transmissive polymer, PBEBT. Towards fabrication of flexible electrochromic devices, the performance of P1C was also tested on silver nanowire network electrodes. Even though the full potential of the material could not be demonstrated, a good optical contrast of 24% was achieved using these electrodes. Under the same potential range allowed by silver nanowire network electrodes, P1C on ITO showed an optical contrast of 30%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1680–1686