Volume 68, Issue 2

A new binuclear complex of copper2+, [LCu2+(CH3COO)2Cu2+L](CH3COO)2 where L is N,N-bis(phthalimide)ethylenediamine, was synthesised and characterised. The complex ion [LCu2+ (CH3COO)2Cu2+L]2+ was encapsulated into ZSM-5 zeolite and used to modify the surface of the glassy carbon electrode. This modified electrode, in a phosphate buffer solution at pH 7.0, exhibited an oxidation potential for dopamine (DA) and ascorbic acid (AA) at electrode potentials of 0.230 V and −0.090 V vs. Ag/AgCl respectively, a separation of 0.320 V. The electro-oxidation of DA or AA on the modified electrode is independent of each other. No interference was observed from Na+, K+, Cl−, SO42−, Mg2+, Ca2+, Zn2+, Fe2+, and glucose. The detection limits obtained were 2.91 × 10−7 M for DA and 3.5 × 10−7 M for AA.

The reaction between caprolactam and ethanol was performed in near-critical water. The primary product (ethyl-6-aminohexanoate) was identified by GC-MS. The influences of the reaction temperature, residence time, initial ratio (reactant/water), pH, and additives on the yields of ethyl-6-aminohexanoate are discussed. The results showed that the yield of ethyl-6-aminohexanoate could be as high as 98 % with SnCl2 as an additive in near-critical water. At the same time, the reaction between caprolactam and ethanol was estimated by a lumped kinetic equation as a second-order reaction in near-critical water, and the activation energy was evaluated according to the Arrhenius equation under acidic and basic conditions. Based on the results, the reaction mechanism between caprolactam and ethanol in near-critical water is proposed.

A novel vanadium dodecylamino phosphate was synthesised by an instant reaction between phosphoric acid and vanadyl acetylacetonoate using dodecylamine as the structure-directing agent at ambient temperature. The physicochemical characteristics of the material were investigated by a variety of analytical techniques. XRD studies revealed the presence of vanadium phosphate and hydrated vanadium phosphate phases in the framework of the material. The catalytic application of this material toward in the synthesis of polyhydroquinolines via Hantzsch condensation was investigated at ambient temperature. This method affords high yields within short reaction times. The influence of various reaction parameters such as different solvents, catalyst dosage, effect of aldehydes, and reusability was studied and a plausible mechanism proposed.

This paper reports on the enantioseparation of racemic phenylalanine or D-phenylalanine and Lphenylalanine via a hollow fibre-supported liquid membrane (HFSLM) and the results are compared with the mathematical model. The enantioseparation results, of 80 % and 73 %, showed the highest extraction and stripping of l-phenylalanine from the feed phase and the enantiomeric excess (% ee) of 60 % from 6 mmol L−1 of initial rac-phenylalanine in the feed solution. The optimum parameters were feed solution at pH 5, 6 mmol LL−1 of O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) as the extractant in octanol as the liquid membrane, and deionised water as the stripping solution. Equal flow-rates of feed and stripping solutions of 100 mL minL−1 were adjusted in a batch operation mode for 50 min at ambient temperature. From the calculation, the equilibrium constants of extraction (K ex) and mass transfer coefficients in the feed phase (k f) and in the liquid membrane phase (k m) were found to be 1.81 L mmol−2, 3.50 × 10−2 cm s−1, and 1.40 × 10−2 cm s−1, respectively. Finally, the change in concentrations of d,l-phenylalanine over time in the feed and stripping solutions by mathematical model were estimated and compared with the experimental results. The values thus calculated were in agreement with the experimental data with the average deviation of approximately 3 %.

The removal of natural organic matter (NOM) is a critical aspect of potable water treatment because NOM compounds are precursors of harmful disinfection by-products, hence should be removed from water intended for human consumption. Ultrafiltration using ceramic membranes can be a suitable process for removal of natural substances. Previously reported experiments were dedicated to evaluating the suitability of ultrafiltration through ceramic membrane for water treatment with a focus on the separation of natural organic matter. The effects of the membrane operating time and linear flow velocity on transport and separation properties were also examined. The experiments, using a 7-channel 300 kDa MWCO ceramic membrane, were carried out with model solutions and surface water at trans-membrane pressure of 0.2–0.5 MPa. The results revealed that a loose UF ceramic membrane can successfully eliminate natural organic matter from water. The permeability of the membrane was strongly affected by the composition of the feed stream, i.e. the permeate flux decreased with an increase in the NOM concentration. The permeate flux also decreased over the period of the operation, while this parameter did not influence the effectiveness of separation, i.e. the removal of NOM. It was observed that the increased cross-flow velocity resulted in the decrease in the membrane-fouling intensity and slightly improved the retention of contaminants.

An analysis of suspended particulate matter, with an emphasis on the Hg chemical forms, is presented. Dust samples originating from an area highly affected by traffic pollution in the city of Prague (Czech Republic) were sampled over a period of three years from air-conditioner filters and fractioned by size. The samples were morphologically characterised by scanning electron microscopy. The main method used for the analysis of constituent mercury compounds was sequential extraction by leaching solutions in combination with thermal desorption. The total mercury content ranged from 0.37 mg kg−1 to 0.82 mg kg−1. It emerged that the mercury was distributed in a wide spectrum of forms, and various trends in the distribution of these forms among the different size classes were observed. The fraction leached by nitric acid (consisting of elemental and complex-bound mercury) was the main constituent of total mercury. The highest content of this fraction was observed in the finest particle size class. The heterogeneity of morphology of the material increased with the size fraction.

Sulphated polysaccharides (SP) were extracted from Fucus vesiculosus seaweed by using two different hydrothermal processes: microwave-assisted extraction (MAE) and autohydrolysis (AH). The extraction yields, chemical composition, and antioxidant activity of the polysaccharides extracted were determined and compared. Although both processes afforded SP with similar yields (18.2 mass % and 16.5 mass %, for MAE and AH, respectively) and l-fucose as the main monosaccharide, the heterogeneous structure of the polysaccharide recovered was significantly affected by the AH process. The SP obtained by MAE contained 53.8 mole % of fucose, 35.3 mole % of xylose, and 10.8 mole % of galactose; while the SP obtained by AH was composed of 76.8 mole % of fucose and 23.2 mole % of galactose. Both samples presented comparable values of antioxidant activity by the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (2,2-diphenyl-1-picrylhydrazyl, DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), and lipid oxidation inhibition methods, but the polysaccharide obtained by AH exhibited a higher antioxidant potential by the differential pulse voltammetry technique. This study demonstrates that the chemical composition and antioxidant activity of SP obtained from F. vesiculosus vary according to the process used for their extraction. However, the SP obtained by MAE or AH both have the potential for use as natural antioxidants in industrial applications.

A new magnesium sulfate templated by 2-methylpiperazine, (C5H14N2)[Mg(H2O)6](SO4)2, was prepared by the slow evaporation method. The obtained crystals were investigated by the Raman and FTIR spectroscopy and crystallographically characterised by single-crystal X-ray diffraction. The compound crystallises in the monoclinic system, space group P21/n. Supramolecular network of this hybrid material consists of Mg2+ cations octahedrally coordinated by six water molecules, sulfate tetrahedra and protonated and disordered diamine linked together by two types of hydrogen bonds: OW—H…O and N—H…O. Dehydration of the title compound takes place in three steps. Thermal decomposition of the anhydrous phase consists in the loss of the organic moiety and one sulfate group leading to the formation of magnesium sulfate.

The present study involves the synthesis of Ce3+ doped ZnO nanophosphors by the zinc nitrate and cerium nitrate co-precipitation method. The synthesized nanophosphors were characterized with respect to their crystal structure, crystal morphology, particle size and photoluminescence (PL) properties using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), transmission electron microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDS) and PL-spectroscopy respectively. XRD results revealed that ZnO nanophosphors are single phase and cubic type structures. Further, PL spectra of ZnO:Ce3+ nanophosphors showed green emission because of the charge transfer at single occupied oxygen vacancies with ZnO holes and red emission due to the cerium ion transitions. Intensity and fine structure of the Ce3+ luminescence and its temperature dependence are strongly influenced by the doping conditions. The formation of ZnO:Ce3+ nanophosphors was confirmed by Fourier transform infrared (FTIR) and XRD spectra.

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)3] · (NO3)3 (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.

Novel polyurethane thermoplastic elastomers were prepared from polycarbonate diols, butane-1,4-diol (chain extender) and hexamethylene diisocyanate. They differ in the kind of macrodiol used and the ratio of macrodiol to chain extender OH groups (hence, in hard segment contents). The tensile properties of the elastomers at low and elevated temperatures were determined and discussed with regard to polyurethane composition and polycarbonate diol structure.

A new symmetrical disulfide containing a diacetylenic unit and bearing a fluorescent carbazolyl end-group forming polymerizable self-assembled monolayers on metallic nanostructures has been synthesized. Suitable modifications of the synthetic steps involved in the synthesis of such derivatives were made in order to assure better synthetic pathway. Conversion of the tosylated derivative into the final symmetrical disulfide is carried out using sodium hydrosulfide (NaSH).

A number of poly(lactic acid-co-glycolic acid)/polyurethane (PLGA/PU) blend films with various PU mole contents were prepared by casting the polymer blend solution in chloroform. The surface morphologies of the PLGA/PU blend films were studied by scanning electron microscopy (SEM). The thermal, mechanical and chemical properties of the PLGA/PU blend films were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile tests and surface contact angle tests. The results revealed that the introduction of PU could markedly modify the properties of PLGA films.

Current cancer treatments lead to insufficient distribution of therapeutic agents in tumor cells due to their lack of selectivity often causing adverse effects in the normal cell uptake of the drug. The challenge is to design therapeutic drugs able to maximize the treatment of malignant cancers while minimizing their adverse effects. In this study, 10B incorporation in the B chronic lymphocytic leukemia cell line MEC-1 was investigated. The cells were treated with l-p-10borophenylalanine (10BPA) and 10boron immuno-nanoparticles (BNPs) loaded with 10BPA with or without the anti-CD20 monoclonal antibody for different contact times. The uptake of 10B by the cells was determined by the inductively coupled plasma mass spectrometry (ICP-MS) after acid mineralization. To obtain accurate and consistent data, the analytical procedure was optimized using factorial experimental design. It was observed that BNP loaded with 10BPA and anti-CD20 represents the best carrier system for 10B in B cells for long time (>10 h) whereas 10BPA seems to be the top drug for short time (< 4 h) procedures.

The molecular parameters of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and some compounds based on triphenylformazans (TPFs) — resulting from the enzymatic transformation of TTC, were subjected to comparative investigation on the basis of semi-empirical quantum-chemical simulations, revealing some changes in dipole moment and polarisability in the TPFs in comparison with TTC. Chemical shift due to substituents was discussed using electronic absorption bands in the UV-VIS range recorded for diluted solutions in various solvents as well as the absorption spectra recorded in the infrared range for KBr dispersions. The correlation of the spectral shift of the electronic absorption bands with a specific function on the solvent refractive index, as recommended by theoretical studies focused on solute-solvent interactions, revealed the major role played by dispersive and induction forces. For several solvents, a different behaviour could be assigned to specific interactions overlapping with universal solute-solvent interactions.

The structural characterisation of the molecule 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl] benzene obtained through Knoevenagel condensation is reported. The single crystals, as light brown rods, were cultured from a chloroform solution using a slow evaporation method at ambient temperature. The compound crystallised in the monoclinic system belonging to the C2/c space group with a = 26.4556(9) Å, b = 3.73562(10) Å, c = 18.4230(6) Å, β = 109.841(4)° and the asymmetric unit comprising Z = 4. The structure is ordered and the molecules of the title compound exhibited a lattice with water molecules located at sites of inversion and two-fold axial symmetries. Thus, only halves of the molecules are symmetrically independent. The lattice is reported and contrasted with X-ray single-crystal diffraction and theoretical calculations of 1,4-bis(1-cyano-2-phenylethenyl)benzene. By using density functional theory (DFT) and second order Moller-Plesset (MP2) theoretical calculations, the ground state geometry in the whole molecule at the B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) theory levels, respectively, were optimised. The DFT calculations showed a quasi-planar structure of the molecule, whereas the wave function-based MP2 method afforded a non-planar optimised structure with significant torsion angles between the pyridine and phenyl rings.

A theoretical study was performed on the 1,3-dipolar cycloaddition between 2,3-dihydrofuran and substituted phenyl azide using Density Functional Theory (DFT) in combination with a 6-311++G(d,p) basis set. The optimum geometries for reactant, transition state and product, as well as the kinetic data, rate constants and reaction constant (ρ) were investigated to rationalise the substitution effects and reaction rates of the 1,3-dipolar cycloaddition process in various solvents. The DFT calculation and Frontier Molecular Orbital (FMO) theory as well as the atomic Fukui indices show that the electron-withdrawing substituents enhance the reaction constant (ρ > 0), especially in polar aprotic solvents. Consequently, small changes in the rate constant of the reaction in various solvents and geometric similarity between reactants and transition state structures were suggested as the early transition state mechanism for electron-withdrawing substituents. In addition, the slope of the Hammett plot and susceptibility of the reaction to electron-withdrawing substituents in various solvents confirmed the mechanism.