Volume 66, Issue 8

Total petroleum hydrocarbons (TPH) are important environmental contaminants which are toxic to human and environmental receptors. Several analytical methods have been used to quantify TPH levels in contaminated soils, specifically through infrared spectrometry (IR) and gas chromatography (GC). Despite being two of the most used techniques, some issues remain that have been inadequately studied: a) applicability of both techniques to soils contaminated with two distinct types of fuel (petrol and diesel), b) influence of the soil natural organic matter content on the results achieved by various analytical methods, and c) evaluation of the performance of both techniques in analyses of soils with different levels of contamination (presumably non-contaminated and potentially contaminated). The main objectives of this work were to answer these questions and to provide more complete information about the potentials and limitations of GC and IR techniques. The results led us to the following conclusions: a) IR analysis of soils contaminated with petrol is not suitable due to volatilisation losses, b) there is a significant influence of organic matter in IR analysis, and c) both techniques demonstrated the capacity to accurately quantify TPH in soils, irrespective of their contamination levels.

The effects of Ag-doping on the physico-chemical, spectral, surface, and catalytic properties of the FeMgO system with various Fe2O3 loadings were investigated. The dopant (Ag) molar ratio varied between 0.01 % and 0.05 %. The techniques employed for characterisation of catalysts were TG/DTG, XRD, ESR, N2 adsorption at −196°C, and catalytic decomposition of H2O2 at 25–35°C. The results obtained revealed that the investigated catalysts consisted of nanosized MgO as the major phase, apart from the MgFe2O4 and/or Fe3O4 phases. ESR result of the FeMgO system revealed the presence of paramagnetic species as a result of Ag-doping. The textural properties including SBET, porosity and St were modified by Ag-doping. The doping process with Ag-species improved the catalytic activity of the FeMgO system. Increasing the calcination temperature from 400°C to 800°C increased the catalytic activity (k*30 °C) of 0.05 AgFeMgO in H2O2 decomposition by 21.2 times.

An efficient synthesis of multidentate polypyridine ligands, 3,5-bis(2,2′-bipyridin-4-ylethynyl)benzoic acid and 3,5-bis(2,5-bis(2-pyridyl)-pyridin-4-ylethynyl)benzoic acid, with potential application in the production of ruthenium dyes for dye-sensitised solar cells was developed. Isolation of intermediate products and final compounds is simple and the yields are very high. The ligands obtained can be used in the synthesis of dendritic analogues of well known and very efficient N3 dye and “black dye”.

This work presents a sol-gel carbon sphere template-assisted method of hollow Eu2O3 microspheres preparation. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), as well as photoluminescence (PL) were used to characterise the products. The formation of hollow structure Eu2O3 microspheres can be assigned to a sol-gel carbon template. Furthermore, this work may confirm that the precursor sol-gel can be loaded onto the inner as well as the outer surface of carbon templates similarly as ions and nanocrystals. The presented method can afford a simple and efficient technique to obtain a series of hollow structure inorganic materials with high productivity.

Environmentally acceptable lead-free ferroelectric KNbO3 (KN) or NaNbO3 (NN) and K0.5Na0.5NbO3 (KNN) thin films were prepared using a modified sol-gel method by mixing potassium acetate or sodium acetate or both with the Nb-tartrate complex, deposited on the Pt/Al2O3 and Pt/SiO2/Si substrates by a spin-coating method and sintered at 650°C. X-ray diffraction (XRD) analysis indicated that the NN and KNN films on the Pt/SiO2/Si substrate possessed a single perovskite phase, while NN and KNN films on the Pt/Al2O3 substrate contained a small amount of secondary pyrochlore phase, as did KN films on both substrates. Scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses confirmed that roughness R q of the thin KNN/Pt/SiO2/Si film (≈ 7.4 nm) was significantly lower than that of the KNN/Pt/Al2O3 film (≈ 15 nm). The heterogeneous microstructure composed of small spherical and larger needle-like or cuboidal particles were observed in the KN and NN films on both substrates. The homogeneous microstructure of the KNN thin film on the Pt/SiO2/Si substrate was smoother and contained finer spherical particles (≈ 50 nm) than on Pt/Al2O3 substrates (≈ 100 nm). The effect of different substrates on the surface morphology of thin films was confirmed.

Polyaniline (PANI) nanofibres were synthesised by the chemical oxidative polymerisation method using ammonium peroxydisulphate (APS) as an oxidant/initiator. In this work, a surfactant-assisted method without shaking and stirring was used for the synthesis of PANI nanofibres. The effect was investigated of various parameters such as monomer/oxidant ratio, polymerisation temperature, and the presence of surfactant (Triton X-100 as a non-ionic surfactant) on the morphology and electrical conductivity of nanofibres. The morphology of PANI nanofibres was characterised by scanning electron microscopy and transmission electron microscopy. The results demonstrate that the morphology of PANI nanofibres was significantly influenced by the aniline/APS mole ratio, polymerisation temperature and presence of the surfactant during synthesis. The results showed that more regular and consistent nanofibres were obtained using a monomer/oxidant ratio of 4 at ambient temperature of polymerisation. PANI nanofibres with diameters in the range of 10–100 nm and length up to several μm were obtained. PANI nanofibres were also characterised using FTIR and UV-VIS absorption spectroscopy. The electrochemical behaviour of PANI nanofibres was studied by cyclic voltammetry. It was found that the electrical conductivity of PANI nanofibres increased with the increasing monomer/oxidant ratio and decreasing polymerisation temperature, respectively.

Five new ammonium phosphinates with formula [XC6H4NHC(O)NHP(O)YO]−[H2Y]+ (Y = N(CH3)(CH2C6H5), X = H (IV), CH3 (V), NO2 (VI); Y = NH(CH2C6H5), X = H (VII), NO2 (VIII)) were synthesised by the reaction of N-arylureidophoshoryl dichlorides with N-methylbenzylamine or benzylamine in the presence of an excess amount of the corresponding amine. All new compounds were characterised by NMR and IR spectral data and elemental analysis. Their antimicrobial activity was tested against some Gram-positive and Gram-negative bacteria and fungi. Compounds IV and VIII exhibited moderate activity in vitro against Bacillus subtilis. In addition, compound VIII moderately inhibited Pseudomonas aeruginosa. The crystal structure of benzylmethylammonium(3-phenylureido)(benzylmethylamino)phosphinate (IV) was also determined. This compound crystallises in the orthorhombic system.

A mild, environmentally friendly method for reduction of aromatic nitro group to amine is reported, using zinc powder in aqueous solutions of chelating ethers. The donor ether acts as a ligand and also serves as a co-solvent. Water is the proton source. This procedure is also a new method for the activation of zinc for electron transfer reduction of aromatic nitro compounds. The reduction is accomplished in a neutral medium and other reducing groups remained unaffected. The ethers used are dioxolane, 1,4-dioxane, ethoxymethoxyethane, dimethoxymethane, 1,2-dimethoxyethane, and diglyme.

The present paper provides details of the preparation of polymeric tablets and microspheres based on piroxicam as a therapeutic active agent and the drug release study from these formulations. Tablets composed of ethylcellulose, Eudragit® or mixtures of Eudragit® and synthesised poly(oxepan-2-one) were prepared and tested. The effect of the matrix on the drug release at 37°C was studied. The drug-loaded microparticles were prepared using solvent evaporation microencapsulation. These systems were characterised by SEM and FTIR spectroscopy and the size and size distribution were also determined. The results demonstrated that the drug release could be modified by means of these formulations. Finally, piroxicam dissolution rate constants were calculated from Higuchi’s release model.

The interaction of 6-methoxyflavanone (6MF, 6-methoxy-2-phenyl-4H-1-benzopyran-4-one) with calf thymus DNA (ctDNA) was investigated by absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry in the presence and absence of β-cyclodextrin (β-CD) acting as capping agent. Molecular modelling was used to optimise the study of 6MF-β-CD and 6MF-DNA interactions. Enhancement in the fluorescence intensity of 6MF was observed due to the formation of 1 : 1 complex with β-CD. In the presence and absence of DNA, 6MF showed different characteristics such as hyperchromic effect, red shift of absorption spectra and fluorescence quenching of 6MF due to binding between 6MF and ctDNA. The nature of the binding group was found to be different for the 6MF-ctDNA and 6MF-ctDNA-β-CD systems. An increase in fluorescence intensity was observed for the 6MF-ctDNA system while varying the concentration of β-CD due to encapsulation of a part of 6MF in cyclodextrin. The results are compatible with the possibility of the interaction of dihydrobenzopyran-4-one moiety of 6MF with ctDNA as well as with β-CD. Cyclic voltammetric studies confirmed the binding interaction between 6MF and ctDNA in the absence and presence of β-CD and molecular modelling explains the site of the interaction of 6MF with cyclodextrin and ctDNA.

Inhibition of photosynthetic electron transport (PET) in spinach chloroplasts by nineteen 2-benzylsulphanylbenzimidazoles (BZA) was studied. BZA were found to inhibit photosynthetic electron transport (PET) and for their inhibitory efficiency, electronic properties of the R substituent on the benzyl moiety are decisive. The PET inhibiting activity of the studied BZA expressed as IC50 varied in the range from 28.5 μM (R = 3,5-(CF3)2) to 394.5 μM (R = 2,4-(NO2)2). For compounds with R = H, 4-CH3, 3-CH3, 3-OCH3, 4-F, 3-F, 4-Cl, 3-Cl, 2-Cl, 4-Br, 3-Br, 3,4-F2, 3,4-Cl2, 3-CF3, 3,5-(CF3)2 linear increase of the inhibitory activity with the increasing value of the substituent’s σ constant up to 0.86 was observed. Further increase of the σ constant resulted in a sharp activity decrease of the corresponding compounds (R = 2-F-6-Cl, 2-NO2, 3,5-(NO2)2, 2,4-(NO2)2). Using EPR spectroscopy and an artificial electron donor diphenyl carbazide it was found that the site of BZA action in the photosynthetic apparatus is situated on the donor side of PS 2, prior to the Z·/D· intermediate.

In this study, derivatisation followed by reductive cleavage (DFRC) were used to investigate milled wood lignin (MWL) and dioxane lignin (DL) structures of Populus nigra and Cupressus sempervirens. After the DFRC reactions, the constituents obtained from these two kinds of lignin were recognised structurally using several chromatographic and spectral methods such as 13C NMR, GC-MS, and GPC. Comparative results showed that the dominant structural components of the two kinds of lignin are obtained from the cleavage of β-O-4 bonds. The main component of DL and MWL of P. nigra is 4-hydroxy-3,5-dimethoxy-1-phenyl-γ-hydroxypropene (syringyl structures). Also, some guaiacyl structures were observed. The dominant component identified in both lignins of C. sempervirens is 4-hydroxy-3-methoxy-1-phenyl-γ-hydroxypropene (guaiacyl structures). The cleavage method has a good performance for both P. nigra and C. sempervirens and the results obtained are in good agreement with previously published data.