Igor E. Uflyand

This paper explores the feasibility of sorption-spectrophotometric determination of a wide range of dyes using a nickel trimesinate-based metal-organic framework as a sorbent. The sorbent was synthesized by direct interaction of a metal salt and trimesic acid in water in the presence of an alkali and characterized using elemental analysis, IR spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. Sorption studies demonstrated that the proposed sorbent is capable of effectively extracting up to 224.64 mg g ^–1 of malachite green dye. The experimental data are well described by the Langmuir sorption isotherm (R ² = 0.943–0.999). The detection limit was 0.4 mg L ^–1 . The obtained results confirm the applicability of this approach for both sample preparation and preconcentration of dyes, as well as for their effective removal from wastewater with subsequent sorbent regeneration.

Nanocomposite photocatalysts are promising for removing pollutants from wastewater. Despite intensive studies, less attention is paid to toxicity of nanocomposites. In our work, we have obtained a new hetero-photocatalyst based on nanostructured CuO (1.5 μm), decorated with Ag (100 nm) and low crystallinity SnO₂. The composition and morphology were studied by XRD, SEM, EDX and AFM. The photocatalytic decomposition of the methyl orange under natural sunlight was investigated. About 84% of the dye decomposed in 120 min, in contrast to unmodified CuO (only 50%). The mechanism of photocatalysis is proposed. The degradation process corresponded to the pseudo-first order kinetics. A decrease in the optical band gap of the nanocomposite compared to unmodified CuO was noted. The nanocomposite efficiency associated with the surface increasing and the heterojunction formation. The phytotoxic effect on the aquatic plant Ceratophyllum demersum was studied. A decrease in phytotoxicity in contrast to the initial CuO was established. The nanocomposite provided a stimulating effect on the chlorophyll a concentration. The results expand the knowledge about the phytotoxicity of photocatalytic nanocomposites.

The paper describes the preparation of silver-containing nanocomposites by thermolysis of silver cinnamate and their application for the manufacture of reactive indicator paper (RIP) sensitive to iodine. The composition, structure, and properties of the obtained materials were studied using IR spectroscopy, X-ray diffraction, the gravimetric analysis method, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Optimal conditions for modifying a cellulose carrier with nanocomposites in laboratory conditions were selected, ensuring high sensitivity of RIP to iodine and uniform and reproducible distribution of the reagent. A new gas extraction colorimetric technique for determining iodide ions in the range of 0.03–1.6 mg L⁻¹ (limit of detection 0.01 mg L⁻¹) was developed, allowing iodides to be determined in multicomponent objects such as food products, pharmaceuticals, and various water bodies with minimized sample preparation. The use of iron(III) as an oxidizing agent and the use of dynamic gas extraction ensure high selectivity and good analytical performance.

The present paper reports the preparation of a nanocomposite thin film consisting of calcium itaconate and graphene oxide (GO). The composite is a black powder consisting of individual shiny prismatic crystals at varying degrees of maturity. The crystal size distribution is quite narrow: from 3.6 to 6.2 μm in length and from 0.7 to 1.1 μm in width. Thin-film-based acetone sensor made of a nanocomposite was fabricated by spin coating of calcium itaconate–GO nanoparticles on glass plates. The thin-film acetone sensor was characterized using FTIR, XRD, SEM, TEM, and the low-temperature nitrogen sorption–desorption method. The sensor response time is 7.66 ± 0.07 s (s_r = 0.92%), and the relaxation time when blowing the surface with clean air or inert gas (nitrogen, argon) is 9.26 ± 0.12 s (s_r = 1.28%). The sensing mechanism of the sensor for detecting acetone at room temperature was also is proposed based on phenomenological understanding due to the absence of direct electronic/charge-transport evidence.

The reaction of zirconium tetrachloride with 2-amino-1,4-benzenedicarboxylic acid in N,N-dimethylformamide with the addition of HCl leads to the formation of zirconium 2-amino-1,4-benzenedicarboxylate. Zirconium 2-amino-1,4-benzenedicarboxylate was characterized by elemental analysis, infrared spectrometry, X-ray diffraction, scanning electron microscopy, and volumetric nitrogen adsorption/desorption. The sample has a constant porosity with an average pore diameter of 7.97 nm and both microporous and mesoporous structure with a large surface area (820 m²/g) corresponding to the type IV adsorption. Zirconium 2-amino-1,4-benzenedicarboxylate was used for solid-phase extraction (SPE) of chlortetracycline hydrochloride from the aqueous solution. The obtained results confirmed the possibility of using the proposed analytical technique as a new, convenient approach to the extraction of chlortetracycline hydrochloride from industrial or other wastewaters, where such substance is contained in insignificant concentrations and its determination requires expensive and complex equipment. In the future, this method can be used not only for the effective removal of pollutants from industrial wastewater with subsequent regeneration of the sorbent, but also as a sample-preparation method for concentrating chlortetracycline hydrochloride from dilute solutions with its subsequent elution and analysis by available methods, for example, spectrophotometry, since the limit of detection is 0.06 mg/L. Experimental data are described by the isotherm of SPE (R² = 0.998–0.999) and show the ability of zirconium 2-amino-1,4-benzenedicarboxylate to extract up to 578 mg/g of sorbent at 5 °C under optimal conditions.

Recently, the synthesis of new gas-sensitive materials for use in resistive humidity sensors has attracted considerable interest. In the study, copper-containing metal–polymer nanocomposites were obtained by thermolysis of copper fumarate (I) and its complexes with 2,2′-dipyridyl (II) and 1,10-phenanthroline (III). The nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, elemental analysis, energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The most common particle sizes of the thermolysis products of compounds I, II, and III were 18.7, 8.3, and 20.7 nm, respectively. The manufactured sensor samples exhibited good sensitivity to the relative humidity (RH) of air: 2.48%/%RH, 3.77%/%RH, and 3.11%/%RH for the thermolysis products of compounds I, II, and III, respectively. Because of the high porosity and moisture absorption of the film, the maximum sensitivity was approximately 0.005 MΩ/%RH, which indicates fairly effective behavior of the film with respect to humidity. The response and recovery times were 23.7, and 37.3 s; 24.7, and 35.8 s; 32.4, and 58.4 s, respectively. The experiment had 88%–97% reproducibility. The fabricated sensors have great potential as humidity-sensing elements for humidity monitoring.

In this work, nanomaterials based on Fe ^III Co ^II and Fe ^III Ni ^II mixed oxides were obtained for the first time by thermal decomposition of polymer complexes of Fe and Co or Ni nitrates with acrylamide. During thermolysis, core‐shell nanomaterials are formed containing nanoparticles of FeCo and FeNi oxides uniformly distributed inside the carbon layer. These nanomaterials are characterized by high chemical and thermal stability. During thermolysis, nanoparticles of mixed oxides FeCo and FeNi were formed with an average crystallite size of 13–22 and 22–33 nm, respectively. Nanomaterials were tested as antifriction and antiwear additives to liquid industrial oil I‐20 A. The values of the friction coefficient decrease by more than 60 % when CoO⋅Fe ₂ O ₃ with a concentration of 0.05 % is added to the industrial oil I‐20 A.