The adsorption of toxic ions Be(II), Bi(III), Cd(II), Cr(III), and Pb(II), and also noble metals Ag(I), Au(III), and Pd(II), from aqueous solutions is studied using carbon nanotubes (CNTs), a magnetic nanosorbent composed of CNTs and magnetic nanoparticles (CNT@MNP), and activated carbon (AC). An advantage of CNT-based adsorbents over AC in terms of capacity was demonstrated, with an increase of approximately 1.5–2 times. The adsorption capacity of the synthesized magnetic adsorbent depends on the morphology of CNTs grown on iron subgroup catalysts: nickel (CNT(Ni)), cobalt (CNT(Co)), and iron (CNT(Fe)). CNT@MNP exhibited superior performance over other carbon adsorbents in magnetic solid-phase extraction, effectively separating solid and liquid phases. Additionally, composite adsorbents containing CNT(Co) and CNT(Fe) were noted for their cost-effectiveness, as they yielded satisfactory results, surpassed those obtained with the individual CNT-based adsorbents. Procedures were developed using these carbon adsorbents and their performance in the determination of elements in aqueous solutions by arc atomic emission spectrometry was estimated.

The effect of chemically active fluorine-containing additives AlF 3 , AgF, and ZnF 2 on the nature of the evaporation of non-volatile elements, B, Be, Cr, Hf, Mo, Si, Ti, and V from aluminum oxide in a direct current arc is studied. It is found that, in the presence of these additives, the intensity of the spectral lines significantly increases and the time of complete evaporation from the electrode decreases for all elements under study, which indicates the formation of their highly volatile fluorides in the electrode crater. It is shown that zinc fluoride is the most effective additive among the studied compounds. This additive ensures the reduction of the limits of determination of highly volatile elements in aluminum oxide by one and a half to two orders of magnitude compared to the version without additives, and also the improvement of the convergence of determination results.

A piezoelectric sensor with a recognition layer based on magnetic carbon nanocomposites, including multi-walled carbon nanotubes, magnetic Fe 3 O 4 nanoparticles, and polymer nanospheres with molecular imprints of erythromycin and azithromycin, obtained by the “core–shell” method, is developed. Silicon dioxide particles are used as cores, on the surface of which a shell molecularly imprinted with macrolides is synthesized by free radical polymerization or the sol–gel method. SiO 2 particles are obtained by the Stober method by varying the ratio of reagents during the synthesis. The size of the cores and nanoparticles of molecularly imprinted polymers ( MIP ) is determined by atomic force microscopy, and the density and uniformity of the layer on the surface of magnetic carbon nanocomposites ( MCNC ) are determined by the piezoelectric quartz crystal microbalance method. The optimal ratio of the reagents (template : functional monomer : cross-monomer) is established by a spectrophotometric method during the synthesis of “core–shell” nanostructures by free radical polymerization. A thin shell of SiO 2 with imprints of an antibiotic based on organosilicon compounds used in the synthesis of the core is formed by the sol–gel method on the surface of the silicon dioxide core. The sensor recognition layer is formed under the action of an external magnetic field. The dependence of the analytical signal of the sensor based on MIP@SiO 2 /MCNC on concentration is linear in the range 5–160 µg/mL for azithromycin and 10–160 µg/mL for erythromycin, and with a recognition layer based on SiO 2 @SiO 2 /MCNC, in the concentration range 20–400 µg/mL for erythromycin.

Conditions for the formation of a recognition layer of a piezoelectric immunosensor based on magnetic carbon nanocomposites (MCNCs) under the action of an external magnetic field are studied. The effects of the size and number of magnetic nanoparticles (MNPs) in the composite on the analytical characteristics of the gravimetric immunosensor are revealed. Scanning electron microscopy is used to determine the average sizes of Fe 3 O 4 magnetic nanoparticles synthesized by coprecipitation. It is noted that the minimum weight and stability of the recognition layer were observed for the nanocomposite obtained at a ratio of carbon nanotubes and MNPs with an average diameter of 22 nm equal to 3 : 1. The formation of peptide bonds between the MCNCs and a penicillin G conjugate was established by IR spectrometry. It was shown that the use of magnetic carbon nanocomposites in the formation of a recognition layer makes it possible to significantly simplify the procedure for preparing a piezoelectric sensor for analysis and reduce its duration from 24 to 1.5 h. The range of the determined antibiotic concentrations is 1–450 ng/mL, the limit of detection is 0.5 ng/mL.

We studied the effect of chemically active fluorine-containing additives AlF3, BaF2, and ZnF2 on the character of evaporation of some low-volatile elements from a refractory matrix in the crater of a DC arc electrode in the analysis of zirconium by atomic emission spectrometry. The additives cause the formation of volatile fluorides of low-volatile elements and their fractional evaporation with respect to the base element evaporation. Impurity fluorides rapidly and completely evaporate during the first 30 s of arcing, and only after that the intensive evaporation of the base begins. Such fractionation increases significantly the intensity of the spectral lines of impurities, decreases the background intensity, and, consequently, improves the limits of determination of low-volatile elements in zirconium oxide. Zinc fluoride is the most effective of the studied additives. Using zinc fluoride, we lowered the limits of determination of low-volatile elements by two orders of magnitude compared to the limits of determination in zirconium oxide without additives and improved the reproducibility of the results of determinations.

A piezoelectric immunosensor with a recognition layer based on magnetic carbon nanocomposites is developed for the determination of ciprofloxacin. The receptor coating of the sensor is formed by the action of a magnetic field on magnetic particles located on the surface of carbon nanotubes modified with a ciprofloxacin conjugate. The sizes of magnetic particles in the composition of the nanocomposite are determined by scanning electron microscopy. A dependence of the mass of the recognition coating on the size of magnetic particles on the surface of carbon nanotubes is shown. A detection cell with a sensor located above a neodymium magnet is proposed. The analytical characteristics of the immunosensor are determined, the limit of detection for ciprofloxacin is 2 ng/mL, and the linear range of determined concentrations is 5–400 ng/mL. The use of magnetic carbon nanocomposites in the creation of a recognition layer ensures the reduction of the time of sensor preparation to analysis from 24 to 1.5 h and extends its service life. The sensor is tested in the detection of antibiotics in milk and meat.

Using an example of the adsorption of Ag(I), Au(III), and Pd(II) ions from aqueous solutions, we studied the dependence of the adsorption capabilities of MNP@CNT magnetic adsorbents on the ratio of their components: magnetite nanoparticles (MNPs) and carbon nanotubes (CNTs) synthesized by the catalytic pyrolysis of ethanol vapors using various catalysts of the iron group. The adsorption capacity of all types of composites increases with the concentration of CNTs in them relative to MNPs. The component ratio of 10 : 1 was optimal for the composites with all CNTs obtained with various catalysts and having different morphologies. At this ratio, the composite has the maximum adsorption capacity for the studied ions, which is 6.5, 6.1, and 5.5 mg/g for Ag(I), Au(III), and Pd(II), respectively, and sufficient magnetization for phase separation in a magnetic field. The modification of CNTs with magnetic nanoparticles enables using the resulting composite in both batch and dynamic versions of solid-phase extraction; previously, individual CNTs obtained with cobalt and iron catalysts did not demonstrate proper results. In the dynamic mode, large volumes of test solutions can be used; higher preconcentration factors are achieved compared to the batch mode; lower limits of element determination are obtained after the evaporation of the eluates from the graphite powder. For all types of composites, a comparative metrological evaluation of the results of element determination by arc atomic emission spectroscopy was performed. The obtained limits of determination for elements are n × 10 –7 wt % ( K preconc = 200).

We studied the effect of chemically reactive additives of AlF 3 , ZnF 2 , and SrF 2 on the character of boron evaporation from a crater in a DC arc electrode in the analysis of graphite. The introduction of fluorinating additives contributes to a rapid, complete, and stable evaporation of boron. Zinc fluoride is the most effective among the studied compounds. The use of this additive made it possible to lower the limits of quantification of boron in graphite to 5 × 10 –6 wt % and to double the reproducibility of the results. The use of zinc fluoride also eliminated the systematic error due to the difference in the evaporation patterns of boron oxide and carbide, which improved the reliability of the determination results.

The performance of a magnetic composite sorbent consisting of magnetic nanoparticles and carbon nanotubes (CNTs) in sorption of toxic metal ions [Be(II), Bi(III), Cd(II), Cr(III)] was studied in relation to the conditions of preparing the composite and its constituents. The pH dependence of the sorption of the metal ions was studied, and the sorption capacity of the composites containing CNTs of different morphology was determined. Be(II) and Cr(III) are taken up from aqueous solutions at pH 6, and Cd(II) and Bi(III), at pH 4.0–5.0. The composite containing CNTs prepared by catalytic pyrolysis of ethanol vapor on the Ni catalyst, CNT(Ni), exhibits the highest, and the sorbent containing CNTs synthesized on the Fe catalyst, CNT(Fe), the lowest sorption capacity. The sorption capacity of the composite containing CNTs prepared on the Co catalyst, CNT(Co), is intermediate. The dependence of the sorption ability of the composite on the ratio of its constituents was studied. The minimal content of magnetic nanoparticles ensuring the magnetism required for the efficient phase separation is 10% relative to the total sorbent weight. At this composition, the sorption capacity of the composite for Be(II), Bi(III), Cd(II), and Cr(III) is the highest: 8.0, 7.0, 6.2, and 6.7 mg g −1 , respectively. Despite lower sorption capacity of magnetic sorbents based on CNT(Fe) and CNT(Co), they can also be successfully used for removing toxic elements from aqueous media by static magnetic solid-phase extraction both in sample preparation for analysis and in treatment of various water reservoirs.

проблем технологии микроэлектроники и особо чистых материалов РАН

Изучены условия формирования распознающего слоя пьезоэлектрического сенсора на основе углеродных нанотрубок для высокочувствительного определения рактопамина в прямом формате иммуноанализа. Показано, что предварительная обработка углеродных нанотрубок концентрированными азотной и серной кислотами, а также активация карбоксильных групп карбодиимидным методом обеспечивают их прочное связывание с аминогруппами подложки на основе 2-меркаптоэтиламина и аминогруппами моноклональных антител к рактопамину, применяемых в качестве распознающих элементов сенсора. Установлены концентрации коллоидных растворов двух видов углеродных нанотрубок в диметилформамиде, обеспечивающие максимальные значения концентрационной чувствительности пьезоэлектрического сенсора при определении рактопамина. Диапазон определяемых содержаний рактопамина с помощью пьезоэлектрического сенсора составляет (нг/см3 ) 0.09-25, предел обнаружения 0.03.

Magnetic sorbent MNP@CNT was synthesized on the basis of magnetic nanoparticles of magnetite (MNPs) and carbon nanotubes (CNTs). The sorbent was studied in extraction of toxic elements from aqueous media and its synthesis conditions were optimized. Isotherms of sorption of the metal ions under study from aqueous solutions were plotted in relation to their concentrations and solution pH values. The optimal conditions for extraction of Pb(II), Cr(III), and Bi(III) at pH 6 and Cd(II) at pH 4.5–5.0 were found. It was shown that the sorption capacity of the MNP@CNT sorbent for the elements under study is comparable with the capacity of carbon nanotubes, being 4.0, 3.8, 3.5, and 3.5 mg g–1 for Bi(III), Pb(II), Ct(III), and Cd(II), respectively. An important advantage of the magnetic composite sorbent over carbon nanotubes is the simple separation of the liquid and solid phases, compared with the conventional column variation of the solid-phase extraction. The resulting composite magnetic sorbent can be used both for analytical purposes, to preliminarily concentrate impurities, and for purification of various technological media and water basins in the environment to remove toxic elements.

Изучены условия получения распознающего слоя пьезоэлектрического сенсора на основе многостенных углеродных нанотрубок (УНТ) для высокочувствительного определения фторхинолонов в прямом и конкурентном форматах иммуноанализа. Установлено, что использование на стадии иммобилизации УНТ способствует увеличению присоединенной массы и концентрационной чувствительности сенсора, вследствие возникновения 3D граничного слоя, повышающего связывающую способность поверхности электрода, и, следовательно, эффективности аффинных взаимодействий для анализируемых фторхинолонов. Показано, что применение УНТ при формировании распознающего слоя расширяет диапазон определяемых содержаний фторхинолонов в конкурентном (10-350 и 10-370 нг/см3 для левофлоксацина и ципрофлоксацина) и прямом форматах анализа (30-650 и 25-670 нг/см3 для левофлоксацина и ципрофлоксацина).

The influence of fluorinating additives (ZnF2 , AlF3) and NaCl additive on the character of evaporation of some semi-volatile and rare-earth elements from the crater of the electrode of DC arc (direct current arc) and reproducibility of the results of their determination in graphite powder is studied. It is found that due to more rapid and complete evaporation of the elements from the electrode in the presence of fluorinating additives the reproducibility of the results of determination is improved two or three-fold.

The influence of the nature of sorption phases on the microweighing parameters of volatile organic compounds sorbed from gases and vapors is investigated using microstructural methods. The mechanism of interaction between nitrogen-containing compounds and universal polymeric and solid-phase specific sorbents is found. The roughness parameters of piezoelectric-resonator electrodes are estimated before and after the deposition of thin sorbent films and during the sorption and desorption of nitrogen-containing compound vapors. Recommendations on how to employ piezoelectric resonators with films for identifying different compounds of gas and air mixtures are presented.

С применением микроструктурных исследований изучено влияние природы сорбционных фаз на параметры микровзвешивания сорбированных органических легколетучих соединений из паров и газов. Установлен механизм взаимодействия азотсодержащих соединений с полимерными универсальными и твердофазными специфическими сорбентами. Оценены параметры шероховатости электродов пьезорезонаторов до и после нанесения тонких пленок сорбентов, а также во время сорбции и десорбции паров азотсодержащих соединений. Даны рекомендации по применению пьезорезонаторов с пленками для определения различных соединений в газо-воздушных смесях.