Vol 89, No 4 (2016)

Nanobiotechnology has opened a new and exciting opportunities for exploring urea biosensor based on magnetic nanoparticles (NPs) mainly Fe₃O₄ and Co₃O₄. These NPs have been extensively exploited to develop biosensors with stability, selectivity, reproducibility and fast response time. This review gives an overview of the development of urea biosensor based on Fe₃O₄ and Co₃O₄ for in vitro diagnostic applications along with significant improvements over the last few decades. Additionally, effort has been made to elaborate properties of magnetic nanoparticles (MNPs) in biosensing aspects. It also gives details of recent developments in hybrid nanobiocomposite based urea biosensor.

Ferrites-spinels of the MFe₂O₄ type (M = Co, Ni, Zn), produced by glycine-nitrate combustion were studied. A physicochemical study of ferrite samples was performed by X-ray fluorescence analysis, scanning electron microscopy, X-ray phase analysis, and X-ray spectroscopy. The average size of the coherent scanning region was found to be (nm): 28 ± 2 for CoFe₂O₄, 32 ± 2 for NiFe₂O₄, and 26 ± 2 for ZnFe₂O₄. Magnetic characteristics were determined by the NMR method. The specific residual magnetization, specific saturation magnetization, and coercive force were, respectively, 14.1 A m² kg⁻¹, 20.1 A m² kg⁻¹, 31800 A m⁻¹ for CoFe₂O₄; 4.4 A m² kg⁻¹, 23.1 A m² kg⁻¹, 6550 A m⁻¹ for NiFe₂O₄; and 5.1 A m² kg⁻¹, 18.3 A m² kg⁻¹, 3200 A m⁻¹ for ZnFe₂O₄. Their magnetic properties show that the resulting ferrospinel powders can be used in the following fields of technology: CoFe₂O₄ in those areas where heat transfer is necessary (hyperthermia) and in development of data storage media; NiFe₂O₄ and ZnFe₂O₄ in those areas where low heat exchange is necessary, ZnFe₂O₄ for fast remagnetization and NiFe₂O₄ as a core or shell for transportation of other substances. The ferrospinel samples compare well in magnetic properties with their foreign commercial analogs, which makes these compounds commercially viable.

IR spectroscopy was used to study the process of a mechanochemical interaction of glucose, sorbite, and cetyl alcohol with natural layered silicates. It was found that mechanocomposites with a chemical bond between the components are formed in the course of activation of the systems. The only exception is the mixture of cetyl alcohol and kaolinite because, being even weaker acids than water, monoatomic alcohols react similarly to water only with alkali and alkaline-earth metals. The data obtained can be used in development of medicinal cosmetic preparations.

Nonionic surfactants were synthesized at various molar ratios of propylene oxide and lauric acid. Propoxylation products were identified by a number of physico-chemical analytical methods. The tensiometric method was used to measure the surface tension of aqueous solutions of the products at interface with air, find their high surface activity, and determine certain colloidal-chemical parameters (critical micelle concentration, surface pressure, maximum adsorption, minimum cross-sectional area of a molecule, change in the Gibbs free energy in micelle-formation and adsorption processes). Laboratory studies of the oil-collecting capacity of these substances were carried out for the example of a thin oil film on the surface of water with varied degree of mineralization.

Fundamental aspects of the sorption recovery of rare-earth elements with a sulfocationite from a nitric-phosphoric acid solution formed as intermediate product in the nitric acid processing of Khibiny apatite concentrate were studied. It was confirmed that rare-earth elements can be effectively sorbed from a nitric-phosphoric acid solution without its preliminary neutralization. It was found that polyvalent metals can be sorbed from a nitric-phosphoric acid solution in the form of positively charged (possibly, single-charged) complexes containing nitrate and(or) phosphate ligands.

Possibility was examined of using sorption purification of underground water containing 246 μg dm^–3 of uranium to remove this component with zeolite and shungite of natural origin, technogenic phosphogypsum, and products of their modification under static and dynamic sorption conditions. Copper(II), nickel, and zinc hydroxides served as modifying agents. It was shown that the modified sorbents enable a substantially higher extraction of uranium into the sorbent under static and dynamic sorption conditions. The water purification reached the level satisfying the requirements of hygienic regulation GN 2.1.5.1315–03 (maximum permissible concentration of chemical substances in water of household and cultural water bodies), imposed on technical-grade water used for industrial purposes.

The possibility of using new carbon–carbon composites as supports for a copper catalyst for ethanol dehydrogenation was demonstrated. The composites, which represented carbon nanostructures (single-walled carbon nanotubes or carbon nanofibers) attached to the surface of carbon microfibers, were prepared by essentially different procedures. Copper catalysts deposited on these supports exhibited different activity in the ethanol conversion, which is associated with the distribution and size of copper particles.

Granulation of powdered materials in a drum-type high-speed granulator was studied. A mathematical model was constructed for describing the granulation in a high-speed granulator in which two processes, coagulation and disintegration, are combined. The constants of the integral transform core for coagulation and disintegration were determined from the experimental data obtained. The suggested mathematical model was shown to be adequate to the real process of granulation of a hydrophobic additive to asphalt concrete mix.

The kinetic relationships of arenesulfonation of benzoic and benzenesulfonic acid hydrazides were studied. Based on the data obtained, the conditions for synthesizing these products were optimized. The synthesis can be performed using aqueous-organic solvents containing 2-propanol, 1,4-dioxane, or tetrahydrofuran as nonaqueous component. The thermal stability of benzenesulfohydrazide and its sulfonation product was compared on the basis of data of gas chromatography–mass spectrometry. The fragmentation pathways of the reactants and target product, sulfonated benzenesulfohydrazide, were suggested.

Time–temperature–transformation diagrams are convenient forms of presenting rheokinetic data on curing of thermosetting binders. However, in curing of thick samples, because of the heat release in curing in combination with relatively low values of thermal conductivity and heat capacity of the majority of thermosetting binders, the rheokinetic features can differ significantly from those observed with thin films and small samples. The paper deals with the construction of the three-dimensional time–temperature–transformation diagram taking into account the thermal properties of the binder. The changes in curing dynamics and appearance of temperature gradients inside the sample with increasing thickness of the binder layer being cured are taken into account. The use of the extended diagram for optimizing the curing conditions for polymer matrix composites is suggested and considered.

The extraction of solketal from aqueous glycerol with AI-92 gasoline, toluene, hexane, and 1-hexene was studied. Aromatic compounds and mixtures containing them exhibit the best extracting properties. A flowsheet was suggested for recovering solketal from reaction products by extraction.

The article describes synthesis of four hydroxyethyl alkylene–double alkyl bromide through substitution of nucleophilic d iethanolamine, 1-bromododecane, and 1,4-dibromobutane. The structure of the new hydroxyl cationic surfactant (HDCS) was characterized by ¹H NMR and FTIR spectra. The aqueous solution of HDCS showed critical micelle concentration, i.e., 5.6 × 10⁻² mM, and could reduce oil/water interfacial tension to 3.28 × 10⁻³ mN m⁻¹. The surface tension measurements provided a series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), adsorption efficiency (pC₂₀), and effectiveness of surface tension reduction (Π_CMC). In addition, maximum surface excess concentration (Г_max) and minimum surface area/molecule (A_min) at the air/water interface were obtained by the Gibbs adsorption isotherm. The influence of inorganic salts (sodium chloride, calcium chloride) and organic salts (sodium benzoate) on the surface tension of HDCS in aqueous solution was investigated. For wettability alteration measurement, contact angle measurement as a quantitative method was utilized. Meanwhile, foam ability, foam stability, and emulsifying property of the synthesized surfactant were also examined at different concentration. HDCS also had excellent viscosity property.

A series of bifunctional Ni–S₂O₈²⁻/ZrO₂ (Ni_x-SSZ-T) catalysts with different Ni mass fraction (x, %) and calcintion temperature (T, °C) were prepared by impregnation method. The catalysts were characterized by XRD, FTIR, and py-FTIR. The effects of Ni content and calcination temperature on the acidic property and isomerization performance of catalyst were investigated using n-pentane isomerization as a probe reaction. The results show that the acidity of Ni_x-SSZ-T catalysts mainly derives from L acid. The addition of a suitable amount of Ni can induce the formation of more acid sites and in turn enhance the isomerization performance of Ni_x-SSZ-T catalyst. With increasing the calcination temperature from 550 to 700°C, B acid strength of catalyst weakens gradually, while the L acid strength increases first and then decreases. The Ni_x-SSZ-T catalyst with Ni content of 1 wt % and calcination temperature of 650°C exhibits the best isomerization performance. At reaction temperature of 230°C, pressure of 2. 0 MPa hydrogen /hydrocarbon molar ratio of 4: 1, and weight hourly space velocity (WHSV) of 1.0 h⁻¹ the isopentane yield reaches 57.0%.

The cyclic stability of thin films (~40 nm) of an anode material based on tin dioxide at charging voltages of 2.5, 1.5, and 0.8 V was studied. The electrodes were prepared on a Picosun R-150 installation using tetraethyltin and remote inductively coupled oxygen plasma.