Volume 64, Issue 1

In this study, urease was immobilized in a polymer network obtained by complexation of poly(1-vinyl imidazole) (PVI) with poly(acrylic acid) (PAA). Preparation of the polymer network was monitored by FT-IR spectroscopy. Scanning electron microscopy (SEM) revealed that enzyme immobilization had a strong effect on film morphology. Proton conductivity of the PVI/PAA network was measured via impedance spectroscopy under humidified conditions. Values of the Michaelis-Menten constant (K M) for immobilized urease were higher than for the free enzyme, indicating a decreased affinity of the enzyme to its substrate. The basic characteristics (pHopt, pHstability, T opt, T stability, reusability, and storage stability) of immobilized urease were determined. The results show that the PAA/PVI polymer network is suitable for enzyme immobilization.

Electrochemical behaviour of sulphate under anodic polarization in molten sodium chloride, cryolite and sodium fluoride was investigated by cyclic voltammetry and chronopotentiometry at the temperatures of 820°C, 1010°C, and 1000°C, respectively. Using a platinum working electrode, two waves were observed on the chronopotentiograms in the systems: NaCl-Na2SO4 and Na3AlF6-Na2SO4. The first wave was attributed to the formation of oxygen. The second wave probably originated from the reaction of oxygen with platinum, or from oxidation of SO3 decomposition products. Three waves were observed for the anodic process of sulphate ions dissolved in molten sodium fluoride. The first wave was attributed to the formation of oxygen. The second and the third wave were attributed to the formation of PtO and PtO2. This conclusion was supported by cyclic voltammetry experiments of the in-situ formed sulphide in molten NaCl at 820°C and by chronopotentiometry on a gold working electrode in the system NaCl-Na2SO4, where no anodic wave was observed.

Utilization of oils/waxes obtained from thermal cracking of individual LDPE (low density polyethylene), HDPE (high density polyethylene), LLDPE (linear low density polyethylene), PP (polypropylene), or cracking of mixed polymers PP/LDPE (1: 1 mass ratio), HDPE/LDPE/PP (1: 1: 1 mass ratio), HDPE/LDPE/LLDPE/PP (1: 1: 1: 1 mass ratio) for the production of automotive gasolines and diesel fuels is overviewed. Thermal cracking was carried out in a batch reactor at 450°C in the presence of nitrogen. The principal process products, gaseous and liquid hydrocarbon fractions, are similar to the refinery cracking products. Liquid cracking products are unstable due to the olefins content and their chemical composition and their properties strongly depend on the feed composition. Naphtha and diesel fractions were hydrogenated over a Pd/C catalyst. Bromine numbers of hydrogenated fractions decreased to values from 0.02 g to 6.9 g of Br2 per 100 g of the sample. Research octane numbers (RON) before the hydrogenation of naphtha fractions were in the range from 80.5 to 93.4. After the hydrogenation of naphtha fractions, RON decreased to values from 61.0 to 93.6. Diesel indexes (DI) for diesel fractions were in the range from 73.7 to 75.6. After the hydrogenation of diesel fractions, DI increased up to 104.9.

Synthesis of four different types of ligands Ar[COC(NOH)R]n (Ar = biphenyl, n = 1, HL1; Ar = biphenyl, n = 2, H2L2; Ar = diphenylmethane, n = 1, HL3; Ar = diphenylmethane, n = 2, H2L4; R = furfurylamine in all ligands) and their dinuclear Co2+, Ni2+, Cu2+, and Zn2+ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by 1H NMR. The results suggest that dinuclear complexes of HL1 and HL3 have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H2L2 and H2L4 have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+. The ligands show strong binding ability towards Hg2+ and Cu2+ ions.

Poly(ethylene glycol)-block-poly(γ-benzyl l-glutamate)-graft-poly(ethylene glycol) (PEG-block-PBLG-graft-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with a PEG chain. Surface morphology of the PEG-block-PBLG-graft-PEG copolymer membrane was characterized by atomic force microscopy (AFM). Mechanical and chemical properties of the PEG-block-PBLG-graft-PEG copolymer membrane were investigated by tensile testing and contact angle testing. The effects of grafting ratio on the properties of PEG-block-PBLG-graft-PEG copolymer membrane were primarilly studied.

Ammonium dioxothiotungstate was synthesized using different tungsten sources and characterized in detail by powder X-ray diffraction, energy dispersive X-ray spectrometry, transmission electron microscopy, nitrogen adsorption, and temperature-programmed sulfidation. It was found that tungsten oxide nanobelts are superior to ammonium metatungstate as tungsten source for the synthesis of ammonium dioxothiotungstate due to a time-consuming aging step being excluded from the synthesis route. Moreover, detailed characteristic data reveal that, when tungsten oxide nanobelts are used, the physical and chemical properties of the resulting ammonium dioxothiotungstate including particles size, specific surface area, and sulfidation pattern were improved. Also, the hydrodesulfurization measurements showed higher catalytic activity and balanced selectivity of the resulting ammonium dioxothiotungstate.

This study is focused on Raman spectroscopy investigations of differently deposited diamond-like carbon (DLC) layers due to varying: (i) Ar and/or N2 flow rate, (ii) number of impulses, and (iii) bias voltage during the growth process. Samples were prepared by a physical vapor deposition method in a pulse arc system. It is shown that Ar and N2 flow rates as well as the bias voltage influence the morphology and chemical composition of the deposited DLC layers. By changing the number of impulses, the number of carbon atoms sputtered from target in the vacuum chamber changes, which is reflected in the thickness and morphology of the DLC layers. Visible light Raman spectroscopy of 632 nm excitation wavelength was used for deep analysis of the deposited layers.

Inhibition effect of imidazole derivative 1,7′-dimethyl-2′-propyl-1H,3′H-2,5′-bibenzo[d]imidazole (DPBI) against mild steel corrosion in 1 M HCl solutions was evaluated using the conventional mass loss method, potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy. The mass loss results showed that DPBI is an excellent corrosion inhibitor; electrochemical polarizations data revealed the mixed mode of inhibition; and the results of electrochemical impedance spectroscopy showed that the change in the impedance parameters, charge transfer resistance, and double layer capacitance with the change in the concentration of the inhibitor is due to the adsorption of the molecule leading to the formation of a protective layer on the surface of mild steel. The inhibition action of this compound was assumed to occur via adsorption on the steel surface through the active centers of the molecule.

Conditions of polyaniline (PANI) nanotubes preparation were analyzed. Aniline was oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. There are two subsequent oxidation steps and the products were collected after each of them. At pH > 3, neutral aniline molecules are oxidized to non-conducting aniline oligomers. These produce templates for the subsequent growth of PANI nanotubes, which takes place preferably at pH 2–3. At pH < 2, granular morphology of the conducting PANI is obtained. High final acidity of the medium should be avoided in the preparation of nanotubes, e.g., by reducing the amount of sulfuric acid which is a by-product. Reduction of the peroxydisulfate-to-aniline mole ratio was tested for this purpose in the present study. Lowering of the reaction temperature from 20°C to −4°C had a positive effect on the formation of nanotubes.

N-Substituted derivatives of 2-benzothiazolesulfenamides give high yields of 1-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene and 1,1-bis-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene in a reaction with acetone in the temperature range from 56°C to 70°C and in the presence of a small amount of water. The α-sulfenylated carbonyl product, 2′-benzothiazolylthiopropan-2-one, is supposed to be an intermediate of this one-pot synthesis. 1,1-Bis-(2′-benzothiazolylthio)-2-tert-butylaminoprop-1-ene has been proved an accelerator of sulfur curing of rubber composites with high processing safety.

Reactivity of 2-hydroxy-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde (I) towards N- and C-nucleophiles was described. A series of new enaminones II–III, Schiff’s base IV, and hydrazinomethylenediketones V–VIII and X were prepared in good yields. Cyclization of compounds X was achieved by an action of acetic acid to give pyrazolo[3,4-d]pyrido[1,2-a]pyrimidines XI. Base catalyzed Knoevenagel condensation of aldehyde I with some active methyl and methylene compounds led to a series of chalcone-like derivatives XII, XV, XVII, XX, XXIII, XXV, XXVII, XXIX, XXXI, XXXII, and XXXV, in fair yields. Cyclization of enones XII, XV, and XX with hydrazine gave novel heterocyclyl substituted pyrazoles XIII, XVII, and XXI, respectively. Pyrano[2,3-d]pyrido[1,2-a]pyrimidine-2,5-diones XXXIII, XXXIV, and XXXVI derivatives were obtained via cyclization of their respective enone derivatives.

In this study, the release of lidocaine hydrochloride was assessed considering the use of both the ionic and the non-ionic polymeric carrier at temperatures of 22°C, 32°C, and 42°C; temperature of 32°C was chosen as the reference surface body temperature. The obtained release rates and respective amounts of lidocaine hydrochloride loaded both to methylcellulose beads and polyacrylic acid beads were compared with respective viscosity, pH and conductivity of the studied systems. The release of lidocaine hydrochloride from the methylcellulose system is influenced by temperature; with the increase of temperature the release rate decreases whereas the viscosity increases. In the polyacrylic acid system, release rates are lower, however, in the first stage they are slightly increasing with the increase of temperature. The final amount of released drug after 24 h increases with the temperature of the release process environment, and it is higher in case of a methylcellulose system. The maximum differences between the released amounts for methylcellulose were in the range of 15 %, whereas in case of polyacrylic acid, the difference was approximately 12 %. Thus, this research is important for patients with differentiated skin surface temperature conditions to whom a local analgesic is to be applied.

The influence of concentration conditions and acidity on the phase separation in non-ionic surfactants Triton X-100 solutions in the presence of phenol was investigated. It was shown that the addition of small amounts of phenol results in the decrease of the cloud point temperature of Triton X-100 solutions. On the other hand, the addition of phenol into the investigated system resulted in the decrease of the hydration values of surfactant-rich phases and the increase of their hydrophobicity. The extraction degree and distribution coefficient of phenol between the water and the surfactant-rich phases were studied. On the basis of data obtained the molar parts of water, phenol and Triton X-100 in the non-ionic surfactant-rich phases formed at different concentration conditions were calculated. Possibilities of the application of phenol-induced micellar extraction for microcomponents preconcentration were estimated.

The occurrence of surfactant-rich phases in aqueous sodium dodecylsulfate solutions in the presence of salicylic acid was investigated. The effect of acidity, electrolyte and salicylic acid concentrations on the parameters of phase formation were studied. Optimal conditions for microcomponent preconcentration were found. The features of solubilization efficiency changes of organic substances depending on their charge and hydrophobicity were established. High efficacy of preconcentration of strongly hydrophobic, positively charged substrates by low-temperature surfactant-rich phases obtained in the sodium dodecylsulfate-salicylic acid-sodium chloride ternary system is shown.

This paper presents some unexpected features related to the solution of equations containing a high-order derivative of pressure with respect to volume equated to zero. For pure components, such equations define, in the pressure-temperature plane, nodal curves similar in shape to mixture spinodal curves. The analysis was made for a general form of two-parameter cubic equations of state and various numerical aspects for the Redlich-Kwong equation of state are exemplified.

Electrochemical copolymerization of N 1,N 3-bis(thiophene-3-ylmethylene)benzene-1,3-diamine (TMBA) with 3,4-ethylenedioxythiophene (EDOT) was carried out in a CH3CN/LiClO4 (0.1 M) solvent-electrolyte via potentiodynamic electrolysis. Chemical structure of the monomer was determined by nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectroscopy. The resulting copolymer was characterized by cyclic voltammetry (CV), FTIR, scanning electron microscopy (SEM), and thermogravimetry analyses (TGA). Conductivity measurements of the copolymer and PEDOT (poly(3,4-ethylenedioxythiophene)) were carried out by the four-probe technique.

New materials were prepared by intercalation reactions between layered zirconium glycine-N,N-dimethylphosphonate (ZGDMP) and non-aromatic heterocyclic amines: piperazine, piperidine, and morpholine. X-ray powder diffraction patterns showed that the entrance of piperazine, piperidine, and morpholine caused an interlayer expansion of 0.40 nm, 0.66 nm, and 0.67 nm, respectively. The infrared spectra were in agreement with an acid-base reaction, involving layered acid host COOH of ZGDMP and basic center atoms of guest molecules. Thermogravimetric curves revealed thermal stability of the intercalation compounds and content of the inserted amine molecules. These results indicate that non-aromatic heterocyclic amines were intercalated into the galleries of host ZGDMP.

Catalytic Meerwein-Ponndorf-Verley (MPV) reduction of various aliphatic, aromatic, and unsaturated aldehydes and ketones to corresponding alcohols (analyzed by GC-MS) in the presence of boron triethoxide (B(OEt)3) were studied. Kinetics of this reduction reaction was also studied and the respective rate constants were determined. It was found that B(OEt)3 catalyzes the reduction of aliphatic aldehydes and ketones to alcohols at room temperature while aromatic aldehydes and ketones were not reduced under the same conditions. In addition, MPV reduction using B(OEt)3 was found to be chemoselective as unsaturated aldehydes and ketones afforded the corresponding alcohols without affecting unsaturated groups. The mechanism proposed involves a six-membered transition state in which both the alcohol and the carbonyl are coordinated to the same boron centre of a boron alkoxide catalyst.