Visible-light–active semiconductor nanoparticles with tunable structural and defect-related properties represent a versatile and promising class of materials for photocatalytic and photoelectrochemical systems, enabling enhanced performance and flexible control over functional properties. In this work, SnO2 spherical nanoparticles were synthesized via a reproducible co-precipitation method with controlled Al3+ and Fe3+ doping (11 and 33 mol

Water pollution, particularly industrial wastewater, is a major environmental issue due to its adverse effects. Sustainable wastewater treatment is one of the major challenges of this century, as well as sustainable production of polymer membranes for it. One of alternative methods is the production of polyelectrolyte complex (PEC) membranes based on aqueous phase separation approach. In this work, nanofiltration membranes from PEC of poly(sodium-p-styrenesulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) with improved transport characteristics were developed via salt-dilution induced phase separation for enhanced water treatment from food anionic dyes and heavy metal ions. The improvement was carried out by variation of monomer ratio (40-60 wt% PSS), introduction of graphene oxide (GO, 3-7 wt%) and PSS with lower molecular weight (70 kDa) in PEC, and combination of all optimal modification conditions. The structural features of PEC-based membranes were studied by FTIR, NMR, Raman, XPS spectroscopies, scanning electron and atomic force microscopies, and thermogravimetric analysis. A theoretical analysis using quantum chemical calculations was carried out to confirm the influence of polymer interactions with components on changes in membrane properties. For PEC membranes with PSS/PDADMAC monomer ratio of 40/60, modified with 5 wt% GO and with the introduction of both PSS (70 kDa) with GO, led to more than 3.5 and 5 times higher permeance, respectively, and enhanced rejection compared to the unmodified PEC membrane in nanofiltration of dye and heavy metal ion solutions.

The evaluation of histamine levels in saliva can be used as one of the diagnostic criteria for detecting many diseases. Therefore, a sensitive, simple, and low-cost method for determining histamine concentrations is needed for point-of-care diagnostics. In this work, the use of a glassy carbon disk electrode, bulk graphite composite electrode, and graphite screen-printed electrode modified with CuO nanoparticles and CuSO4 for histamine quantification by cyclic voltammetry was studied. The best results were obtained using the screen-printed sensor with the working electrode modified by a CuSO4 aqueous solution and covered with a Nafion-like polymer film. The developed sensor showed a 5 × 10–9 M detection limit with a broad linear range from 5 × 10–9 to 1 × 10–6 M of histamine in a phosphate buffer solution, providing sufficient reliability for saliva analysis after simple sample preparation. The analysis of real saliva samples revealed no significant interfering matrix effect. The total analysis time, including sample preparation, did not exceed 15 minutes.

Pervaporation membrane reactors attract much attention as a promising system, in which separation and reaction are carried out simultaneously to overcome the thermodynamic equilibrium limitation and to increase the conversion by removing one or several synthesized products. For this, in this study supported carboxymethyl cellulose (CMC) membranes modified with Zn-based metal organic frameworks (Zn(SEB), Zn(BIM), Zn(BDC)Si) were developed. Transport properties of obtained membranes were evaluated in pervaporation separation of quaternary mixtures (acetic acid (AcOH), ethanol (EtOH), ethyl acetate (EtAc), water) with various compositions. CMC/Zn(BIM) membranes, possessed optimal transport characteristics, were tested in hybrid process "reaction + pervaporation" using batch pervaporation membrane reactor and compared with data obtained in batch reactor without membrane. The changes of structure and physicochemical properties of developed membranes were studied by spectroscopic, microscopic methods, thermogravimetric analysis and measurements of contact angles. To confirm findings obtained, theoretical consideration by computational methods for the CMC/Zn(BIM) membrane was carried out. It was shown that the application of optimal CMC/Zn(BIM)(10 wt%) membrane in pervaporation-assisted esterification reactor led to the formation of more than 5 times larger amount of EtAc in the reactor with decreased AcOH conversion compared to batch reactor without membrane in the separation of esterification reaction AcOH and EtOH (1/1 M) with 5 wt% Amberlyst 15 catalyst at 60 degrees C.

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5–15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18–20 L·m−2·h−1 for the reference PPSU membrane up to 38–140 L·m−2·h−1 for 20 wt.% PPSU/10–15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5–7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR—81–89%, DRr—26–32%, DRir—10–20%, DT—33–45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR—29–38%, DRr—6–14%, DRir—74–89%, DT—88–94%).

Thin-film composite (TFC) membranes obtained by forming a selective polyamide (PA) layer on a surface of a porous membrane-substrate via interfacial polymerization (IP) technique are the most effective membranes for nanofiltration (NF). The idea of this study is that addition of polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG) block copolymers to the polyphenylsulfone (PPSU) casting solution tunes the pore structure (pore size and porosity), water contact angle and topology of the selective layer of ultrafiltration (UF) membranes. This influences the formation of PA layer via IP since membrane-substrate significantly effects the first stage of IP reaction. For the first time the effect of PEG-PPG-PEG copolymer molecular weight, content of PEG blocks and copolymer concentration in the PPSU casting solution on the structure, hydrophilicity and performance of ultrafiltration and TFC NF membranes was revealed. It was found that increase in PEG block content and PEG-PPG-PEG molecular weight led to the increase in pore size, porosity and hydrophilicity of selective layer of ultrafiltration membranes which results in the formation of thinner and more uniform PA layer with higher cross-linking degree of NF membranes via IP. It was revealed that NF membrane flux increased with the rise in the content of PEG units from 10 to 80 wt.% and increase in molecular weight of PEG-PPG-PEG block copolymer. Modification of PPSU membrane-substrate yielded the increase in selectivity of the corresponding TFC NF membranes due to the formation of more uniform and denser defect-free PA layer attributed to the rise in hydrophilicity of membrane substrate. It was found that membrane substrate modification by PEG-PPG-PEG results in the enhancement of antifouling performance toward bovine serum albumin (flux recovery ratio is 99-100%) and long-term stability during 48 h operation compared to the reference membrane. Modification of PPSU membrane substrate by F38 PEG-PPG-PEG block copolymer (Mn= 5 000 g·mol-1, PEG block content of 80 wt.%) was found to yield the TFC NF membranes with the best combination of permeation, separation and antifouling performance and long-term stability.

The electrochemical performance of gold electrode in sulfuric acid was studied with addition of different concentrations of dissolved fullerenol-d with C60(OH)24 chemical formula. Based on the cyclic voltammetry data, the conclusion of surface complexation of Au(III) with fullerenol was made. The scheme was suggested to describe the electrode process, based on catalysis of anodic Au dissolution by fullerenol molecules. The technique was suggested to detect fullerenol-d (C60(OH)24) in concentration range from 2.6·10–9 M to 2.0·10–7 M by means of cyclic voltammetry of gold in aqueous sulfuric acid solution.

Pervaporation is considered the most promising technology for dehydration of bioalcohols, attracting increasing attention as a renewable energy source. In this regard, the development of stable and effective membranes is required. In this study, highly efficient membranes for the enhanced pervaporation dehydration of ethanol were developed by modification of sodium alginate (SA) with a polyethylenimine (PEI) forming polyelectrolyte complex (PEC) and graphene oxide (GO). The effect of modifications with GO or/and PEI on the structure, physicochemical, and transport characteristics of dense membranes was studied. The formation of a PEC by ionic cross-linking and its interaction with GO led to changes in membrane structure, confirmed by spectroscopic and microscopic methods. The physicochemical properties of membranes were investigated by a thermogravimetric analysis, a differential scanning calorimetry, and measurements of contact angles. The theoretical consideration using computational methods showed favorable hydrogen bonding interactions between GO, PEI, and water, which caused improved membrane performance. To increase permeability, supported membranes without treatment and cross-linked were developed by the deposition of a thin dense layer from the optimal PEC/GO (2.5%) composite onto a developed porous substrate from polyacrylonitrile. The cross-linked supported membrane demonstrated more than two times increased permeation flux, higher selectivity (above 99.7 wt.% water in the permeate) and stability for separating diluted mixtures compared to the dense pristine SA membrane.

The study is devoted to the comparison of the results of rapid urease tests (RUT) and the data obtained in histological examination. For this purpose, the semi-quantitative assessment of urease activity of two BUTs was compared: the semi-quantitative Pronto Dry (GASTREX, France) widely used in Europe and the AMA RUT Expert M test registered in Russia (AMA LLC, Russia) with the data obtained by histological and PCR analyses. High correlation of semi-quantitative indices of urease activity according to the results of both tests as well as correlation of these indices with the data obtained by histological examination and PCR analysis was established.

One of the solutions for the growing problem of water purification is photocatalytic degradation of the pollutants. Semiconductor nanoparticles are widely under study as a promising photocatalyst for this purpose. However, there is still lack of understanding of the relation between properties of nanoparticles, in their turn related with synthesis conditions, and photocatalytic efficiency, as well as of the other factors influencing the process.

Nowadays, nanofiltration is actively used for water softening and disinfection, pre-treatment, nitrate, and color removal, in particular, for heavy metal ions removal from wastewater. In this regard, new, effective materials are required. In the present work, novel sustainable porous membranes from cellulose acetate (CA) and supported membranes consisting of CA porous substrate with a thin dense selective layer from carboxymethyl cellulose (CMC) modified with first-time synthesized Zn-based metal–organic frameworks (Zn(SEB), Zn(BDC)Si, Zn(BIM)) were developed to increase the efficiency of nanofiltration for the removal of heavy metal ions. Zn-based MOFs were characterized by sorption measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The obtained membranes were studied by the spectroscopic (FTIR), standard porosimetry and microscopic (SEM and AFM) methods, and contact angle measurement. The CA porous support was compared with other, prepared in the present work, porous substrates from poly(m-phenylene isophthalamide) and polyacrylonitrile. Membrane performance was tested in the nanofiltration of the model and real mixtures containing heavy metal ions. The improvement of the transport properties of the developed membranes was achieved through Zn-based MOF modification due to their porous structure, hydrophilic properties, and different particle shapes.

Presently, water pollution poses a serious threat to the environment; the removal of organic pollutants from resources, especially dyes, is very important. Nanofiltration (NF) is a promising membrane method to carry out this task. In the present work, advanced supported poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membranes were developed for NF of anionic dyes using bulk (the introduction of graphene oxide (GO) into the polymer matrix) and surface (the deposition of polyelectrolyte (PEL) layers by layer-by-layer (LbL) technique) modifications. The effect of PEL combinations (polydiallyldimethylammonium chloride/polyacrylic acid (PAA), polyethyleneimine (PEI)/PAA, and polyallylamine hydrochloride/PAA) and the number of PEL bilayers deposited by LbL method on properties of PPO-based membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Membranes were evaluated in NF of food dye solutions in ethanol (Sunset yellow (SY), Congo red (CR), and Alphazurine (AZ)). The supported PPO membrane, modified with 0.7 wt.% GO and three PEI/PAA bilayers, exhibited optimal transport characteristics: ethanol, SY, CR, and AZ solutions permeability of 0.58, 0.57, 0.50, and 0.44 kg/(m(2)h atm), respectively, with a high level of rejection coefficients-58% for SY, 63% for CR, and 58% for AZ. It was shown that the combined use of bulk and surface modifications significantly improved the characteristics of the PPO membrane in NF of dyes.

The presented work is devoted to the study of the possibility of using planar materials consisting of ultramicroelectrode arrays for voltammetric analysis of compounds with close redox potential, but with different diffusion coefficients, which has great prospects in the analysis of various oligomers, including oligopeptides. A feature of the electrochemical behavior of materials containing arrays of ultramicroelectrodes is the realization of hemispherical diffusion, which can lead to the steady state or unsteady state regime of the electrode depending on the intersection or non-intersection of the hemispheres. There is also a transient mode of operation of electrodes at partial intersection: voltammetry diagrams obtained in this mode may contain analytical information on the concentrations of substances with one redox potential, which favorably distinguishes the approach from the classical cyclic voltammetry using macroelectrodes. The prospects of the proposed approach are confirmed by the example of analysis using ultramicroelectrode arrays of ferrocenemethanol and triglycene ferrocenemethanol ester. The results obtained prove the possibility of applying the approach to the analysis of electroactive oligopeptide derivatives.

Membrane fouling is a serious issue in membrane technology which cannot be completely avoided but can be diminished. The perspective technique of membrane modification is the introduction of hydrophilic polymers or polyelectrolytes into the coagulation bath during membrane preparation via non-solvent-induced phase separation. The influence of polyacrylic acid (PAA) molecular weight (100,000, 250,000 and 450,000 g·mol−1) added to the aqueous coagulation bath (0.4–2.0 wt.%) on the polysulfone membrane structure, surface roughness, water contact angle and zeta potential of the selective layer, as well as the separation and antifouling performance, was systematically studied. It was found that membranes obtained via the addition of PAA with higher molecular weight feature smaller pore size and porosity, extremely high hydrophilicity and higher values of negative charge of membrane surface. It was shown that the increase in PAA concentration from 0.4 wt.% to 2.0 wt.% for all studied PAA molecular weights yielded a substantial decrease in water contact angle compared with the reference membrane (65 ± 2°) (from 27 ± 2° to 17 ± 2° for PAA with Mn = 100,000 g·mol−1; from 25 ± 2° to 16 ± 2° for PAA with Mn = 250,000 g·mol−1; and from 19 ± 2° to 10 ± 2° for PAA with Mn = 450,000 g·mol−1). An increase in PAA molecular weight from 100,000 to 450,000 g·mol−1 led to a decrease in membrane permeability, an increase in rejection and tailoring excellent antifouling performance in the ultrafiltration of humic acid solutions. The fouling recovery ratio increased from 73% for the reference membrane up to 91%, 100% and 136% for membranes modified with the addition to the coagulation bath of 1.5 wt.% of PAA with molecular weights of 100,000 g·mol−1, 250,000 g·mol−1 and 450,000 g·mol−1, respectively. Overall, the addition of PAA of different molecular weights to the coagulation bath is an efficient tool to adjust membrane separation and antifouling properties for different separation tasks.

A review of new results on the application of layer-by-layer (LbL) chemical assembly procedures to the production of thin-layer structures on the surfaces of various substrates in order to develop active elements (AEs) of chemoresistive gas sensors for the determination of inorganic and organic compounds in air and controlled gas atmospheres is presented. The LbL assembly procedures and their features, such as the possibility of synthesis under the conditions of soft chemistry, the precise setting of the thicknesses of applied layers, and the production of multilayers consisting of individual layers with predicted compositions, are considered. Charge transfer between analyte molecules in the layers and oxidation–reduction centers on the AE surface is briefly discussed, and conditions for the functioning of optimal AEs are formulated. The capabilities of the LbL assembly method to precisely control the thickness of each layer in a multilayer system on the electrode surface and thus directionally change the sensor response and select a layer responsible for the best practically important characteristics are emphasized. The role of catalysts in these processes is noted. The results of original publications on the application of LbL assembly procedures to the development of a wide range of AEs for sensors are presented, and the analytical characteristics of the sensors are compared. In conclusion, the prospects for using these procedures in the manufacture of new AEs with high sensitivity and selectivity and a short response time are considered.

•Novel polyelectrolyte complex (PEC)/fullerene derivatives membranes were developed.•Effect of fullerene derivatives on membrane structure and properties was studied.•Membranes were tested in pervaporation isopropanol dehydration.•Membranes were tested in nanofiltration of heavy metals.•PEC membrane with 4 wt% fullerenol had optimal transport characteristics.

The spherical diffusion that occurs when using ultramicroelectrodes (i.e., electrodes with a characteristic size of 1–10 µm) contributes to a higher mass transfer rate. This leads to equalization of the depletion rates of the near-electrode layer due to the electrochemical reaction and to the supply of the product from the solution depth. This is the reason why, for ultramicroelectrodes, a limiting size of the spherical layer exists in which the concentration gradient is localized (diffusion layer). Thus, a stationary mass transfer mode is achieved, which is expressed in the sigmoidal CV curve’s shape. In ultramicroelectrode arrays, when the diffusion hemispheres are separated, a steady-state diffusion is realized. However, with a decrease in the interelectrode distance, which leads to the diffusion spheres intersection, a mixed regime arises, which is not fully time-independent. The resulting voltammogram’s shape change can serve as an analytical signal in the study of substances with differing diffusion coefficients, since the diffusion layer growth rate and, consequently, the area of intersection of neighboring spheres, depends on it. This work shows the applicability of voltammetry using ensembles of ultramicroelectrodes operating in the transient mode for the analysis of mixtures of electrochemically active compounds with close electrode reaction parameters, such as exchange currents and electrode potential. Ferrocenemethanol esters are used as an example. The applicability of cyclic voltammetry on the UME array for analysis of mixtures was illustrated by means of finite element modelling. The reliability of the modelling results was experimentally proved for ferrocenemethanol esters with glycine and triglycine.

Thin-film composite membranes (TFC) obtained by the formation of a selective layer on a porous membrane-substrate via interfacial polymerization (IP) are indispensable for separation procedures in reverse osmosis, nanofiltration, pervaporation, and gas separation. Achieving high selectivity and permeability for TFC membranes is still one of the main challenges in membrane science and technology. This study focuses on the development of thin film nanocomposite (TFN) membranes with a hierarchically structured polyamide (PA)/chitosan succinate (ChS) selective layer embedded with a metal–organic framework of iron 1,3,5-benzenetricarboxylate (Fe-BTC) for the enhanced pervaporation dehydration of isopropanol. The aim of this work was to study the effect of Fe-BTC incorporation into the ChS interlayer and PA selective layer, obtained via IP, on the structure, properties, and performance of pervaporation TFN membranes. The structure and hydrophilicity of the developed TFN membranes were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM), along with water contact angle measurements. The developed TFN membranes were studied in the pervaporation dehydration of isopropanol (12–30 wt % water). It was found that incorporation of Fe-BTC into the ChS interlayer yielded the formation of a smoother, more uniform, and defect-free PA ultrathin selective layer via IP, due to the amorpho-crystalline structure of particles serving as the amine storage reservoir and led to an increase in membrane selectivity toward water, and a slight decrease in permeation flux compared to the ChS interlayered TFC membranes. The best pervaporation performance was demonstrated by the TFN membrane with a ChS-Fe-BTC interlayer and the addition of 0.03 wt % Fe-BTC in the PA layer, yielding a permeation flux of 197–826 g·m−2·h−1 and 98.50–99.99 wt % water in the permeate, in the pervaporation separation of isopropanol/water mixtures (12–30 wt % water).

The application of environmentally friendly and energy-efficient membrane processes allows improvement the ecological safety and sustainability of industrial production. However, the effective application of membrane processes requires novel high-performance thin film composite (TFC) membranes based on biopolymers to solve environmental problems. In this work for the first time novel thin film nanocomposite (TFN) membranes based on biopolymer chitosan succinate (ChS) modified with the metal organic framework iron 1,3,5-benzenetricarboxylate (Fe-BTC) were developed for enhanced pervaporation dehydration. The formation of a selective layer of TFN membranes on the porous membrane-support was carried out by two methods—dynamic technique and physical adsorption. The effect of the membrane formation method and Fe-BTC content in ChS layer on the structure and physicochemical properties of TFN membranes was investigated. The developed TFN ChS-based membranes were evaluated in the pervaporation dehydration of isopropanol (12–30 wt.% water). It was found that TFN ChS-Fe-BTC membranes prepared by two methods demonstrated improved permeation flux compared to the reference TFC ChS membrane. The best transport properties in pervaporation dehydration of isopropanol (12–30 wt.% water) were possessed by TFN membranes with 40 wt.% Fe-BTC prepared by dynamic technique (permeation flux 99–499 g m−2 h−1 and 99.99% water in permeate) and TFN membranes with 5 wt.% Fe-BTC developed by physical adsorption (permeation flux 180–701 g m−2 h−1 and 99.99% water in permeate).