Oleg Silyukov

Saint Petersburg State University | SPBU · Institute of chemistry

The layered double hydroxides (LDHs) of transition metals are of great interest as building blocks for the creation of composite photocatalytic materials for hydrogen production, environmental remediation and other applications. However, the synthesis of most LDHs is reported only by the conventional coprecipitation method, which makes it difficult...

BaAl2Si2O8 (barium feldspar-based) materials are widely used in glass and ceramic industry due to high melting temperature, chemical resistance, low thermal expansion, low dielectric constants and attractive luminescence properties. The durability of barium feldspar ceramics strongly depends on reversible phase transitions between the low-temperatu...

Layered perovskite-like niobate CsBa2Nb3O10 has been synthesized in a pure single-phase state for the first time using both nitrates and carbonates of cesium and barium. Unlike its Ca-, Sr- and Pb-containing analogs, the niobate obtained was shown not to undergo substitution of interlayer alkali cations with protons (protonation) upon acid treatmen...

Nanosheets of layered perovskite-like oxides attract researchers as building blocks for the creation of a wide range of demanded nanomaterials. However, Ruddlesden–Popper phases are difficult to separate into nanosheets quantitatively via the conventional liquid-phase exfoliation procedure in aqueous solutions of bulky organic bases. The present st...

A protonated and hydrated Dion-Jacobson-phase HSr2Nb3O10∙yH2O was used to prepare two series of inorganic–organic derivatives containing non-covalently intercalated n-alkylamines and covalently grafted n-alkoxy groups of different lengths, as they are promising hybrid materials for photocatalytic applications. Preparation of the derivatives was car...

Two series of hybrid inorganic–organic materials, prepared via interlayer organic modification of protonated Ruddlesden–Popper phases HLnTiO4 (Ln = La, Nd) with n-alkylamines and n-alkoxy groups of various lengths, have been systematically studied with respect to photocatalytic hydrogen evolution from aqueous methanol under near-ultraviolet irradia...

Photocatalytic activity of HB2Nb3O10 perovskite nanosheets (B = Ca, Sr) has been systematically investigated in the reactions of hydrogen production, depending on the method of the photocatalyst preparation: using the pristine nanosheets in the parent suspension without reassembly, filtered nanosheets as well as nanosheets restacked by hydrochloric...

The stability of platinized n-butylamine-intercalated layered titanate H2La2Ti3O10 during the process of photocatalytic hydrogen production from aqueous methanol under UV irradiation has been thoroughly investigated by means of XRD, CHN, TG, 13C NMR, BET, SEM and GC-MS analysis. It was revealed that n‑butylamine completely abandons the interlayer s...

Nowadays, the efficient conversion of plant biomass components (alcohols, carbohydrates, etc.) into more energy-intensive fuels, such as hydrogen, is one of the urgent scientific and technological problems. The present study is the first one focused on the photoinduced hydrogen evolution from aqueous D-glucose and D-xylose using layered perovskite-...

Protonated Ruddlesden-Popper phases HLnTiO4 (Ln = La, Nd) have been used to yield two series of inorganic-organic derivatives containing non-covalently intercalated n-alkylamines and covalently grafted n-alkoxy groups with a various hydrocarbon chain length. Synthesis was carried out according to multistage schemes using both conventional benchtop...

Two series of hybrid inorganic-organic derivatives, obtained via the modification of protonated Ruddlesden–Popper phases H2Ln2Ti3O10 (Ln = La, Nd) with intercalated n-alkylamines and grafted n-alkoxy groups, have been systematically investigated in relation to photocatalytic hydrogen production from a model of 1 mol % aqueous solution of methanol f...

The paper is focused on the Fe for Co substitution effect on the redox and catalytic properties in the perovskite structure of GdFeO3. The solid oxides with the composition GdFe1−xCoxO3 (x = 0; 0.2; 0.5; 0.8; 1) were obtained by the sol-gel method and characterized by various methods: X-Ray diffraction (XRD), temperature-programmed reduction (H2-TP...

In the present work, we report the results on exfoliation and coating formation of inorganic–organic hybrids based on the layered perovskite-like bismuth titanate H2K0.5Bi2.5Ti4O13·H2O that could be prepared by a simple ion exchange reaction from a Ruddlesden–Popper phase K2.5Bi2.5Ti4O13. The inorganic–organic hybrids were synthesized by intercalat...

The photocatalytic activity of layered perovskite-like oxides in water splitting reaction is dependent on the hydration level and species located in the interlayer slab: simple or complex cations as well as hydrogen-bonded or non-hydrogen-bonded H2O. To study proton localization and dynamics in the HCa2Nb3O10·yH2O photocatalyst with different hydra...

A series of hybrid inorganic–organic niobates HCa2Nb3O10×ROH, containing n-alkoxy groups of primary alcohols (R = Me, Et, Pr, Bu, Hx, and Dc) grafted in the interlayer space, has been studied for the first time in relation to photocatalytic hydrogen generation from a model 1 mol % aqueous solution of methanol under ultraviolet irradiation. Photocat...

Structures of partially and completely protonated Ruddlesden–Popper phases, H0.7Na0.3NdTiO4·0.3H2O and HNdTiO4, have been established by means of neutron and X-ray diffraction analysis and compared among themselves as well as with that of the initial titanate NaNdTiO4. It was shown that while interlayer sodium cations in the partially protonated fo...

Emerging technologies aimed to tune properties of microporous materials, including zeolitic catalysts, involve microwave processing that accelerates chemical reactions and often increases efficiency of target materials. Here we report on the results of our comprehensive study of copper-exchanged mordenites obtained from sodium mordenite with Si/Al...

The protonated perovskite-like titanate H2La2Ti3O10 has been used to produce organic-inorganic hybrids with simple organic molecules: methylamine, methanol, monoethanolamine, and n-butylamine. The optimal pathways for the preparation of such hybrids are summarized. Solid-state NMR, combined with thermal analysis, Raman, and IR spectroscopy, has bee...

The use of perovskite-type layered oxide K2La2Ti3O10 (Per) as a modifier of the Torlon® polyamide-imide (PAI) membrane has led to the formation of an specific structure of a dense nonsymmetrical film, namely, a thin perovskite-enriched layer (3–5 μm) combined with the polymer matrix (~30 μm). The PAI/Per membrane structure was studied by SEM in com...

The possibility to prepare new organic-inorganic hybrids by grafting reactions of the protonated perovskite-like oxide H2K0.5Bi2.5Ti4O13·H2O (HKBT4·H2O) with n-alcohols (with alkyl chain length nc = 1–4, 6, 10) has been studied. The reactions have been conducted by grafting using preliminarily n-butylamine and n-octylamine intercalated derivatives...

A series of hybrid niobates HCa2Nb3O10×RNH2, containing n-alkylamines (R = Me, Et, Pr, Bu, Hx, Oc) intercalated into the interlayer space, has been thoroughly studied concerning the photocatalytic hydrogen production from a model aqueous solution of methanol for the first time. All the hybrid photocatalysts were synthesized by the conventional cera...

New organic–inorganic hybrids have been synthesized by the intercalation of n-alkylamines (methylamine, ethylamine, n-propylamine, n-butylamine, n-hexylamine, and n-octylamine) into the structure of the protonated and hydrated form of the perovskite-like layered titanate H2K0.5Bi2.5Ti4O13·H2O (HKBT4·H2O). The possibility of the synthesis of the hyb...

Protonation and hydration processes of layered perovskite-like oxide KCa2Nb3O10 during the reaction with nitric acid solutions with different concentrations were studied by means of TG, STA + MS, XRD, SEM, EDX and ICP methods. It was found that despite the absence of significant changes in crystal structure, treatment of KCa2Nb3O10 with water leads...

A layered perovskite-type oxide intercalated with n-butylamine is reported as an efficient photocatalyst for hydrogen production from aqueous solutions of alcohols for the first time. The hybrid photocatalyst H2Nd2Ti3O10×BuNH2 was synthesized by solid-state ceramic method followed by protonation, intercalation of methylamine and subsequent substitu...

Protonated forms of layered perovskite-like titanates HLnTiO4 (Ln = La, Nd), relating to the Ruddlesden-Popper phases, have been used to yield inorganic-organic hybrids with the simplest representatives of amines (methylamine), alcohols (methanol), aminoalcohols (monoethanolamine) as well as n-butylamine. The possibility of the synthesis of the hyb...

To study protons localization in H1.83K0.17La2Ti3O10·0.17H2O and their motional characteristics, complementary Nuclear Magnetic Resonance (NMR) techniques have been applied. ¹H Magic Angle Spinning NMR evidences the presence of different proton containing species. By analyzing the temperature dependence of the ¹H MAS NMR spectrum we attribute the o...

A protonated form of the n = 4 layered bismuth containing perovskite-like titanate K2.5Bi2.5Ti4O13 belonging to Ruddlesden-Popper phases was prepared via ion exchange reaction of interlayer K⁺ with protons. Its composition was investigated by TG ICP and EDX analysis was found to be H2K0.5Bi2.5Ti4O13·H2O. The thermal behavior of the obtained phase w...

New hybrid organic-inorganic derivatives HLnTiO4 · CH3NH2 (Ln = La and Nd) are obtained via the intercalation of methylamine into the interlayer space of protonated layered perovskite-like titanates HLnTiO4. The existence of three stable methylamine derivatives, namely, α-, β-, and γ-forms, is found for each of the titanates. The thermal stability...

The effect of isovalent cation substitution of lanthanum atoms in the structure of La2SrAl2O7 oxide, and phase equilibria (solidus-liquidus curves) in the binary system La2SrAl2O7-Nd2SrAl2O7 were studied. It was found that Nd3+ substitution for La3+ has effect on the structure of La2SrAl2O7 in respect of the character of cation distribution in the...

The possibility of synthesizing protonated derivatives of layered perovskite-like titanates Bi4Ti3O12, ABi4Ti4O15, (A = Ba, Sr, Ca) and K2.5Bi2.5Ti4O13 is experimentally investigated. It is established that in the case of Bi4Ti3O12 and ABi4Ti3O15, single-phased protonated derivatives cannot be obtained by treating the compounds with acid solutions,...

The Rb 2 La 2 Ti 3 O 10 layered oxide was synthesized by the solid-state method. Three phases with different protonation degrees and intercalated water contents were obtained from the initial compound by the treatment with distilled water and hydrochloric acid. The obtained samples were characterized by powder X-ray diffraction, SEM, X-ray microana...

The synthesized 1,2,4-thiadiazole derivative displaying biological activity has low aqueous solubility and dissolution rate. Novel oral formulations of thiadiazole with β- and hydroxypropyl-β-cyclodextrins were obtained by grinding and freeze-drying methods with the purpose to improve the aqueous solubility. Complex formation of 1,2,4-thiadiazole d...

Reactions of layered perovskite-like oxides K2La2Ti3O10, NaLaTiO4 and corresponding protonated oxides H2La2Ti3O10, HLaTiO4 with vanadyl sulfate aqueous solution have been studied. It was revealed that the exchange reaction of interlayer alkali cations in K2La2Ti3O10 and NaLaTiO4 by with vanadyl cations, which was reported in the literature previous...

The K2La2Ti3O10 layered oxide was synthesized by high-temperature technique. Ion exchange properties of K2La2Ti3O10·H2O were investigated by continuous potentiometric titration of its suspension in KOH with HCl. The shape of the titration curve indicates that the ion-exchange reaction of interlayer K⁺ to H⁺ proceeds at pH 7.5–8.5 at the rate as hig...

Complex formation of α-, β- and γ-cyclodextrins with 1,2,4-thiadiazole derivatives, which are structural isomers displaying an activity in the treatment of Alzheimer’s disease, was examined by the use of 1H NMR and UV-spectroscopy. Stability constants of the complexes formed between cyclodextrins and thiadiazoles in two different buffers (pH 1.2 an...

Pharmacologically important properties of two structurally related biologically active 1,2,4-thiadiazole derivatives were investigated in phosphate buffer and biorelevant media FaSSIF simulating the intestinal fluid. Solubility and distribution coefficients of thiadiazoles were found to be substantially higher in FaSSIF than in blank buffer. On the...

In NaLnTiO4 (Ln = La, Nd) layered perovskite-like compounds, the mobility of sodium ions was studied using impedance spectroscopy and simulated by the molecular dynamics approach. NaLnTiO4 was prepared via a high-temperature solid-state reaction with final annealing at 900 °С. The conductivity was measured using the complex impedance technique betw...

New 1,2,4-thiadiazole derivative displaying neuroprotective potential and high activity in the treatment of Alzheimer’s disease has been synthesized. The objective of this study was to improve the aqueous solubility of this drug-like compound by means of complex formation with native and hydroxypropylated β-cyclodextrins. To this end, aqueous solub...

Effect of cyclodextrins on aqueous solubility of 1-[5-(3-chloro-phenylamino)-1,2,4-thiadiazol-3-yl]-propan-2-ol (I), which was synthesized and proposed for the treatment of Alzheimer’s disease, was studied. First of all, inclusion complex formation of I with different cyclodextrins was studied in aqueous solutions. Formation of more stable complexe...

Previously synthesized 1,2,4-thiadiazole derivatives displayed an activity in the treatment of Alzheimer’s disease; however, these compounds are poorly soluble in aqueous solutions. Inclusion complex formation with cyclodextrins is proposed for the development of water-soluble dosage forms of 1,2,4-thiadiazoles under study. To this end, binding of...

Novel 1,2,4-thiadiazole derivatives as potent neuroprotectors were synthesized and identified. Their ability to inhibit the glutamate stimulated Ca²⁺ uptake was investigated. The solubility of thiadiazoles was measured in a buffer solution (pH 7.4) at 298 K. The distribution coefficients in 1-octanol/buffer (pH 7.4) and 1-hexane/buffer (pH 7.4) imm...

The article presents results of the complex study of hydration and protonation processes of promising photocatalysts K2Nd2Ti3O10, belonging to the family of perovskite-type layered Ruddlesden–Popper phases. K2Nd2Ti3O10 was synthesized by solid-state method and was monitored using powder X-ray diffraction. The behavior in water has been studied by m...

Synthesis of A-site deficient perovskite-type compound La2/3TiO3-δ was carried out using a hydrothermal treatment and a combination of sol-gel method, followed by combustion and heat treatment. The structure, morphology and particle size of the synthesized compounds were characterized by X-ray diffractionand scanning electron microscopy. It was sho...

Layered HLnTiO4 (Ln=La, Nd) compounds belonging to Ruddlesden-Popper phases were found to form partially hydrated compounds Ln2Ti2O7∙xH2O during thermal dehydration as well as defect oxides Ln2□Ti2O7 as final products. Further heating of metastable defect Ln2□Ti2O7 substances leads to the formation of pyrochlore-type oxides Ln2Ti2O7 (p), with subse...

In the present work protonic forms of layered n = 1,3 Ruddlesden-Popper oxides HLnTiO(4) and H(2)Ln(2)Ti(3)O(10) (Ln = La, Nd) were used as the starting point for soft chemistry synthesis of two series of perovskite-like compounds by acid leaching and exfoliation, promoted by vanadyl sulfate. The last route leads to the nanostructured VO2+ containi...

In the present work protonic forms of layered n=1 Ruddlesden-Popper oxides HLnTiO(4) (Ln=La, Nd) were used as starting point for synthesis of three series of the perovskite-like compounds. Characterization by SEM, powder XRD and TGA has been performed for the determination of the structure and composition of synthesized oxides.

The behavior in aqueous solutions of the two types of layered perovskite-like structures, NaLnTiO4 titanates (Ln = Nd, La) belonging to the family of Ruddlesden–Popper phases and ANdTa2O7 tantalates (A = Na, Cs, H) belonging to the family of Dion–Jacobson phases, has been studied by means of thermogravimetric analysis and powder X-ray diffraction....

Layered perovskite-type oxides A2Ln2Ti3O10 (A = Li, Na, K; Ln = La, Nd) prepared by solid-phase synthesis and their hydrated forms were characterized by the methods of TGA, XRD, and by UV-Vis spectroscopy. Photocatalytic activity of A2Ln2Ti3O10 oxides in reaction of hydrogen evolution from aqueous alcoholic suspensions irradiated by UV-light was st...

The catalytic activity of the perovskite-like layered oxides NaNdTiO4, LiNdTiO4, and HNdTiO4 in the reaction of the methyl orange dye decomposition under the action of UV irradiation was studied. Rate constants of the pseudo-first order were determined. It was found that in the series NaNdTiO4, HNdTiO4, and LiNdTiO4 the photocatalytic activity of t...

The behavior of perovskite-like NaNdTiO4 complex oxide in acid aqueous solutions was studied. By the X-ray and thermogravimetry analyses the instability of NaNdTiO4 in aqueous solutions was found, which is determined by the sodium cation exchange for protons and by water molecules intercalation into the interlayer space of the crystal structure. Th...

The processes of phase formation in the Na2CO3-TiO2 and Na2CO3-TiO2-Nd2O3 systems are investigated in the temperature range 600–900°C. The high-temperature solid-phase reactions underlying the process of formation of complex oxide NaNdTiO4 are studied. It is established that the synthesis of the NaNdTiO4 compound occurs through the reaction of the...