High-Pressure Synthesis of Cubic ZnO and Its Solid Solutions with MgO Doped with Li, Na, and K

The possibility of doping ZnO in its metastable rock salt structure with Li, Na, and K intended to act as acceptor dopants was investigated. For the first time, MgxZn1-xO alloys and pure ZnO with a rock salt structure doped with Li, Na, and K metals was obtained by high-pressure synthesis from pure oxides with the addition of carbonates or acetates of the corresponding metals as dopant sources. Successful stabilization of the metastable rock salt structure and phase purity were confirmed by X-ray diffraction. Transmission electron microscopy was used to study the particle size of nanocrystalline precursors, while the presence of Li, Na, and K metals in rock salt ZnO was detected by electron energy-loss spectroscopy and X-ray photoelectron spectroscopy in MgxZn1-xO alloys. Electron paramagnetic resonance measurements revealed the acceptor behavior of Li, Na, and K dopants based on the influence of the latter on native defects and natural impurities in ZnO-MgO alloys. In addition, diffuse reflectance spectroscopy was used to derive band gaps of quenched rock salt ZnO and its alloys with MgO.

Melamine Barbiturate as a Light-Induced Nanostructured Supramolecular Material for a Bioinspired Oxygen and Organic Radical Trap and Stabilization

Use of coantioxidant systems is a prospective way to increase the effectiveness of antioxidant species in tissue repair and regeneration. In this paper, we introduce a novel scheme of a reactive oxygen species (ROS) trap and neutralization during self-assembly of supramolecular melamine barbiturate material. The performed reaction chain mimics the biological process of ROS generation in key stages and enables one to obtain stable hydroperoxyl and organic radicals in a melamine barbiturate structure. Melamine barbiturate also neutralizes hydroxyl radicals, and the effectiveness of the radical trap is controlled with ROS scavenger incorporation. The number of radicals dramatically increases during light-inducing and depends on pH. The proposed scheme of the ROS trap and neutralization opens a way to the use of supramolecular assemblies as a component of coantioxidant systems and a source of organic radicals.

Analysis of influence of background therapy for comorbidities in the period before infection on the risk of the lethal COVID outcome. Data from the international ACTIV SARS-CoV-2 registry («Analysis of chronic non-infectious diseases dynamics after COVID-19 infection in adult patients SARS-CoV-2»)

Aim      To study the effect of regular drug therapy for cardiovascular and other diseases preceding the COVID-19 infection on severity and outcome of COVID-19 based on data of the ACTIVE (Analysis of dynamics of Comorbidities in paTIents who surVived SARS-CoV-2 infEction) registry.Material and methods  The ACTIVE registry was created at the initiative of the Eurasian Association of Therapists. The registry includes 5 808 male and female patients diagnosed with COVID-19 treated in a hospital or at home with a due protection of patients' privacy (data of nasal and throat smears; antibody titer; typical CT imaging features). The register territory included 7 countries: the Russian Federation, the Republic of Armenia, the Republic of Belarus, the Republic of Kazakhstan, the Kyrgyz Republic, the Republic of Moldova, and the Republic of Uzbekistan. The registry design: a closed, multicenter registry with two nonoverlapping arms (outpatient arm and in-patient arm). The registry scheduled 6 visits, 3 in-person visits during the acute period and 3 virtual visits (telephone calls) at 3, 6, and 12 mos. Patient enrollment started on June 29, 2020 and was completed on October 29, 2020. The registry completion is scheduled for October 29, 2022. The registry ID: ClinicalTrials.gov: NCT04492384. In this fragment of the study of registry data, the work group analyzed the effect of therapy for comorbidities at baseline on severity and outcomes of the novel coronavirus infection. The study population included only the patients who took their medicines on a regular basis while the comparison population consisted of noncompliant patients (irregular drug intake or not taking drugs at all despite indications for the treatment).Results The analysis of the ACTIVE registry database included 5808 patients. The vast majority of patients with COVID-19 had comorbidities with prevalence of cardiovascular diseases. Medicines used for the treatment of COVID-19 comorbidities influenced the course of the infectious disease in different ways. A lower risk of fatal outcome was associated with the statin treatment in patients with ischemic heart disease (IHD); with angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor antagonists and with beta-blockers in patients with IHD, arterial hypertension, chronic heart failure (CHF), and atrial fibrillation; with oral anticoagulants (OAC), primarily direct OAC, clopidogrel/prasugrel/ticagrelor in patients with IHD; with oral antihyperglycemic therapy in patients with type 2 diabetes mellitus (DM); and with long-acting insulins in patients with type 1 DM. A higher risk of fatal outcome was associated with the spironolactone treatment in patients with CHF and with inhaled corticosteroids (iCS) in patients with chronic obstructive pulmonary disease (COPD).Conclusion      In the epoch of COVID-19 pandemic, a lower risk of severe course of the coronavirus infection was observed for patients with chronic noninfectious comorbidities highly compliant with the base treatment of the comorbidity.

The Key Role of Active Sites in the Development of Selective Metal Oxide Sensor Materials

Development of sensor materials based on metal oxide semiconductors (MOS) for selective gas sensors is challenging for the tasks of air quality monitoring, early fire detection, gas leaks search, breath analysis, etc. An extensive range of sensor materials has been elaborated, but no consistent guidelines can be found for choosing a material composition targeting the selective detection of specific gases. Fundamental relations between material composition and sensing behavior have not been unambiguously established. In the present review, we summarize our recent works on the research of active sites and gas sensing behavior of n-type semiconductor metal oxides with different composition (simple oxides ZnO, In₂O₃, SnO₂, WO₃; mixed-metal oxides BaSnO₃, Bi₂WO₆), and functionalized by catalytic noble metals (Ru, Pd, Au). The materials were variously characterized. The composition, metal-oxygen bonding, microstructure, active sites, sensing behavior, and interaction routes with gases (CO, NH₃, SO₂, VOC, NO₂) were examined. The key role of active sites in determining the selectivity of sensor materials is substantiated. It was shown that the metal-oxygen bond energy of the MOS correlates with the surface acidity and the concentration of surface oxygen species and oxygen vacancies, which control the adsorption and redox conversion of analyte gas molecules. The effects of cations in mixed-metal oxides on the sensitivity and selectivity of BaSnO₃ and Bi₂WO₆ to SO₂ and VOCs, respectively, are rationalized. The determining role of catalytic noble metals in oxidation of reducing analyte gases and the impact of acid sites of MOS to gas adsorption are demonstrated.

Molecular profile of oral fluid in new coronavirus infection

Oral fluid is an alternative biological material that confirms correlations with blood parameters in various pathological conditions of the body. In order to find a non-invasive approach to stratification of patients with COVID-19 disease, molecular biomarkers of the oral fluid have been determined in patients with moderate coronavirus infection in comparison with clinically healthy individuals. It has been shown that proteomic, carbohydrate, macro- and microelement profiles of the oral fluid in coronavirus infection can be used for diagnostics. The features of protein metabolism were revealed: an increase in the content of total protein, urea; increased activity of enzymes aspartate aminotransferase, gamma glutamyl transpeptidase, creatine phosphokinase, alkaline phosphatase; changes in carbohydrate metabolism, which is expressed by an increase in glucose and lactate levels, an increase in lactate dehydrogenase activity, sodium, chloride, calcium, magnesium, iron content.

Melamine-Barbiturate Supramolecular Assembly as a pH-Dependent Organic Radical Trap Material

In the last two decades, a large number of self-assembled materials were synthesized and they have already found their way into large-scale industry and science. Hydrogen-bond-based supramolecular adducts are found to have unique properties and to be perfect host structures for trapping target molecules or ions. Such chemical systems are believed to resemble living matter and can substitute a living cell in a number of cases. Herein, a report on an organic material based on supramolecular assembly of barbituric acid and melamine is presented. Surprisingly, the structure is found to host and stabilize radicals under mild conditions allowing its use for biological applications. The number of free radicals is found to be easily tuned by changing the pH of the environment and it increases when exposed to light up to a saturation level. We describe a preparation method as well as stability properties of melamine-barbiturate self-assembly, potentiometric titration, and hydrogen ions adsorption data and EPR spectra concerning the composite.

Titania-based nanoheterostructured microspheres for prolonged visible-light-driven photocatalysis

Titanium dioxide is a widely used photocatalytic material possessing such advantages as safety, low cost, and high reactivity under the ultraviolet light illumination. However, its applicability in sunlight is limited due to the wide band gap and, as a consequence, the low quantum yield. Doping of titanium dioxide with metal or non-metal atoms and creating heterojunctions based on it are some of the most efficient ways to overcome this drawback. Herein we propose a new facile way of synthesis of nitrogen-doped TiO₂/MoO₃ and TiO₂/WO₃ microsphere-shaped nanocomposite photocatalysts, combining the advantages of these two methods. It is revealed that such structures are not only photo-active when exposed to visible light, but can also accumulate a photoinduced charge, thus allowing the catalytic reaction to be prolonged for a long time after the illumination is switched off (up to 48 h). With the help of EPR spectroscopy, paramagnetic defects in the samples were determined. The obtained results show good application prospects of the visible-light-driven TiO₂-based nanoheterostructured microspheres in the environmental purification.

Solvothermally-derived MoO3-benzotriazole hybrid structures for nanocontainer depot systems

Layered MoO₃ containing intercalated benzotriazole (up to 40 mol%) shows much promise as a container system for corrosion protection.

Enhancement of Lewis Acidity of Cr-Doped Nanocrystalline SnO2 : Effect on Surface NH3 Oxidation and Sensory Detection Pattern

Understanding ammonia oxidation over metal oxide surfaces is crucial for improving its detection with resistive type gas sensors. Formation of NO_x during this process makes sensor response and calibration unstable. Cr-doping of nanocrystalline metal oxides has been reported to suppress NO₂ sensitivity and improve response towards NH₃ , however the exact mechanism of such chromium action remained unknown. Herein, by using EPR spectroscopy we demonstrate formation of Cr(VI) lattice defects on the surface of nanocrystalline Cr-doped SnO₂ . Enhancement of Cr-doped SnO₂ surface acidity and ammonia adsorption as a result has been revealed by using in situ IR spectroscopy. Moreover, a decrease in concentration of free electrons in the conduction band has been shown as a result of substitutional Cr(III) defects formation. Weaker NO_x chemisorption during ammonia oxidation over SnO₂ surface after Cr doping has been found with the use of mass-spectrometry assisted NH₃ thermo-programmed desorption. The given example of surface acidity adjustment and electronic configuration by means of doping may find use in the design of new gas-sensing metal oxide materials.

Red-Shifted Absorptions of Cation-Defective and Surface-Functionalized Anatase with Enhanced Photoelectrochemical Properties

Manipulating the atomic structure of semiconductors is a fine way to tune their properties. The rationalization of their modified properties is, however, particularly challenging as defects locally disrupt the long-range structural ordering, and a deeper effort is required to fully describe their structure. In this work, we investigated the photoelectrochemical properties of an anatase-type structure featuring a high content of titanium vacancies stabilized by dual-oxide substitution by fluoride and hydroxide anions. Such atomic modification induces a slight red-shift band gap energy of 0.08 eV as compared to pure TiO₂, which was assigned to changes in titanium-anion ionocovalent bonding. Under illumination, electron paramagnetic resonance spectroscopy revealed the formation of Ti^III and O₂ ^- radicals which were not detected in defect-free TiO₂. Consequently, the modified anatase shows higher ability to oxidize water with lower electron-hole recombination rate. To further increase the photoelectrochemical properties, we subsequently modified the compound by a surface functionalization with N-methyl-2-pyrrolidone (NMP). This treatment further modifies the chemical composition, which results in a red shift of the band gap energy to 3.03 eV. Moreover, the interaction of the NMP electron-donating molecules with the surface induces an absorption band in the visible region with an estimated band gap energy of 2.25-2.50 eV. Under illumination, the resulting core-shell structure produces a high concentration of reduced Ti^III and O₂ ^-, suggesting an effective charge carrier separation which is confirmed by high photoelectrochemical properties. This work provides new opportunities to better understand the structural features that affect the photogenerated charge carriers.

Paramagnetic properties of carbon-doped titanium dioxide

This paper reports the experimental results on paramagnetic properties of carbon-doped titanium dioxide. The electron paramagnetic resonance study of the samples has been carried out both in dark and under illumination. The nature of defects and their dynamics under illumination of carbon-doped TiO_2 samples are discussed.

Chemical modification of a porous silicon surface induced by nitrogen dioxide adsorption

The effect of gaseous and liquid nitrogen dioxide on the composition and electronic properties of porous silicon (PS) is investigated by means of optical spectroscopy and electron paramagnetic resonance. It is detected that the interaction process is weak and strong forms of chemisorption on the PS surface, and the process may be regarded as an actual chemical reaction between PS and NO(2). It is found that NO(2) adsorption consists in forming different surface nitrogen-containing molecular groups and dangling bonds of Si atoms (P(b)-centers) as well as in oxidizing and hydrating the PS surface. Also observed are the formation of ionic complexes of P(b)-centers with NO(2) molecules and the generation of free charge carriers (holes) in the volume of silicon nanocrystals forming PS.

[Distribution of chemical elements in whole blood and plasma]

The distribution factor (Fd) of 35 elements of plasma and whole blood in 26 healthy men and women was detected by ICP-OES. Usilig this parameter the elements were subdivided in 3 pools. 9 of them have Fd higher than 1.5 ("elements of plasma"-Ag, Ca, Cu, In, Li, Na, Se, Si, Sr); 6 have lower than 0.5 ("elements of blood cells"-Fe, K, Mn, Ni, V, Zn), other 20-about 1 ("blood elements"). Fd of all elements depends on ionic radius. Elements of 2nd sub-groups of all groups of Mendeleev's periodic table ("heavy metals") depend on the similar law: "with growing of ionic radius the concentration of elements in plasma enhances". In alkaline metals Fd depends on the opposite law:" with growing of ionic radius of alkaline metal the quantity of elements in blood cells enhance". Dependence of Fd on the value of atomic mass in periods or in exterior electronic cloud (s-, p-, d-, f-) was not established. The table of distribution of all detected elements in whole blood in relation to 8 macroelements (Ca, Mg, K, Na, S, P, Fe, Zn,) is presented, as a basic diagnostic criteria in metal-ligand homeostasis disturbance.