Preconcentration of mercury using duolite GT-73 in the analysis of water samples by inductively coupled plasma atomic emission spectrometry.

Duolite GT-73 resin was used for the preconcentration of Hg(II) from hydrochloric acid media as well as separation of the analyte from diversity of the co-existing metal ions (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) in off-line column operation. Due to the high affinity of the resin to the transition metals, Hg was adsorbed alongside with the foreign metals investigated. A complete release of the concomitant metals from the resin without the desorption of Hg was carried out using solutions of HCl and HNO3. A quantitative recovery of Hg was obtained by digestion of the resin using a H2SO4 and H2O2 mixture in an open-vessel system. An enrichment factor of 40 was achieved. The devised procedure was applied for the determination of Hg(II) in tap-water samples.     

Tunable negative index metamaterial employing in-plane switching mode at terahertz frequencies

We analysed the response of a tunable liquid crystal metamaterial transducer in the terahertz frequency range. Tunability of scattering parameters is achieving by an in-plane switching (IPS) effect. The metamaterial structure is based on Ω-shape resonators. A full-wave analysis technique based on the finite-difference time-domain (FDTD) method was performed using the QuickWave 3D electromagnetic solver. Terahertz transmission properties of the metamaterial structure can be controlled by the director of the liquid crystal layer. The effective refractive index for operation frequency varies from negative to positive values. A novel approach to switching of metamaterial transducer by IPS mode is presented.     

Resistance of composite materials based on BaCeO3 against the corrosive effects of carbon dioxide and water vapour at intermediate fuel cell operating temperatures

The objective of this work is to analyse the chemical stability of BaCe_0.85Y_0.15O_3?δ –Ce_0.85Y_0.15O_2?δ (BCY15–YDC15) composite materials at 600 °C and to compare the aforementioned chemical stability with that of pure BCY15. The composite powders were obtained by mixing together powders of BCY15 and YDC15 in the following volume fractions: 90 % BCY15 + 10 % YDC15, 70 % BCY15 + 30 % YDC15, 30 % BCY15 + 70 % YDC15, 20 % BCY15 + 80 % YDC15 and 10 % BCY15 + 90 % YDC15. After that both powders and sintered samples of the BCY15 and the BCY15–YDC15 composites were saturated in two different atmospheres at 600 °C: CO₂/H₂O (3.1 mol% H₂O) and N₂/H₂O (46.8 mol% H₂O). The effects of the previously mentioned atmospheres on the physicochemical properties of the samples were investigated via differential thermal analysis (DTA) combined with thermogravimetric analysis (TG). Furthermore, mass spectrometry was used to analyse the chemical composition of the gases released from the samples during the DTA–TG heating process. The surface and cross-section morphology of the samples were examined by scanning electron microscopy. Moreover, the phase composition of each sample was studied via X-ray Diffraction. From the combined analysis, it can be concluded that the addition of YDC15 in the composite samples leads to an increase in resistance against the corrosive effects of CO₂. Furthermore, it was determined that all samples maintain stability in the presence of H₂O at 600 °C.     

Design simulations for a biogas purification process using aqueous amine solutions

Using the simulation program CHEMCAD, performance characteristics, design optimization, and costs of an absorption/stripping system used to purify 100 kg h^?1 of biogas in a biogas power plant were investigated. Potential absorbents used in the chemical absorption process were the following aqueous solutions: pure diglycolamine, diglycolamine/piperazine, and diglycolamine/methyldiethanolamine/piperazine. Mixtures for agricultural biogas purification to below 1 vol. % of CO₂ and 4 × 10^?4 mass % of H₂S were determined via a simulation in the above mentioned program. The chosen mixtures were then entered into an absorption/desorption system and simulations for each unit were provided by CHEMCAD. From the simulation results, the design parameters were calculated and entered into each unit??s ??cost estimation?? section in the aforementioned program to estimate the purchase costs of the apparatuses. Taking into account the installation, maintenance, as well as other additional costs, the actual machine purchase costs were multiplied by the Lang factor. Costs of additional streams were also calculated by multiplying the ten-year utility losses by their respective cost factors. From these calculations, the absorbent mixture, allowing biogas production at the lowest estimated costs for ten years, was found.     

Interaction between rhodanine and silver species on a nanocolloidal surface and in the solid state

This paper discusses and compares molecular interactions of rhodanine (Rd), the heterocyclic compound containing N, S, and O atoms, with two forms of silver species, i.e. Ag(I) ions and silver nanocolloidal particles. Vibrational spectroscopic and powder crystallography studies on coordination of Ag(I) ions in the solid state, supported by density functional theory, clearly indicate complexation through the nitrogen (the deprotonated imino group) and exocyclic sulfur atoms. Molecules of the complex are arranged in a one‐dimensional infinite polymeric chain structure that intertwines to give a helix motif. On the other hand, adsorption geometry of Rd on the silver surface was determined by using surface‐enhancement Raman scattering (SERS) spectroscopy. Observed differences between the SERS and the normal Raman spectra of Rd suggest that Rd adsorbs on the silver species after the rearrangement of the keto‐thione form into the enol‐thiol tautomer in acidic and neutral solutions. This leads to adsorption on this silver species through the thiolate ion. On the other hand, the alkaline pH forces first N‐deprotonation of Rd, and, in consequence, the obtained anion of the keto‐thione form interacts with the silver surface as a result of the presence of lone pairs of nitrogen and sulfur atoms, similar to the case discussed for the solid state. Copyright © 2009 John Wiley & Sons, Ltd.     

Properties of polyethylene glycol supported tetraarylporphyrin in aqueous solution and its interaction with liposomal membranes

5,10,15,20-Tetrakis(4-hydroxyphenyl)porphyrin was functionalized by covalent attachment of poly(ethylene glycol) (PEG) chains of various molecular weights, 350, 2000, and 5000 Da. The properties of PEG-functionalized tetraarylporphyrins in aqueous solution and their interactions with liposomes have been studied. Electronic absorption spectroscopy, dynamic light scattering, atomic force microscopy, and fluorescence quenching were used to monitor aggregation of porphyrin chromophores and behavior of the attached PEG chains in the aqueous solution. The tendency for aggregation of porphyrin chromophores in aqueous solution and the efficiency of fluorescence quenching by KI decrease with increasing length of PEG chain linked to the porphyrin ring. The experimental results indicate that polymer clusters are present in aqueous solution of all pegylated porphyrins. The interactions between the pegylated porphyrins and phosphatidylcholine liposomes in the aqueous solution were studied using the fluorescence methods. The apparent binding constants of porphyrin chromophores to liposomes were determined. The degree of binding was found to be dependent on the molecular weight of the attached polymer.