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Biomineralization is a universal process that has implications in a variety of areas, from civil engineering to medicine. While crystallization of amorphous CaCO3 formed in vitro is known to precede the vaterite-calcite/aragonite pathway, this process could be significantly altered when induced by bacteria, particularly within the extracellular matrix (ECM) of microbial cells. We used a combination of SEM, SANS, SAXS, FTIR and XRD methods to investigate the structure of CaCO3 formed during biomineralization induced by planktonic Bacillus cereus. Formation of precipitates in the presence of CaCl2 and urea was observed both during bacterial growth and in the medium devoid of bacteria and ECM (cell-free system). The pathway for polymorphic transformations of CaCO3 from the amorphous phase to vaterite and further to calcite was confirmed for the bacterium-induced mineralization and did not depend on the concentration of Ca2+ and urea. The structure of CaCO3 sediments differed when formed in cell-free and bacterial systems and varied depending on time and the medium composition. The rate of precipitation was accelerated in the presence of DNA, which had little effect on the solid phase structure in the cell-free system, while strongly affecting the structure and polymorphic composition of the precipitates in bacterial culture.

In this study, organo-inorganic nanohybrids LHGd-MTSPP with enzyme-like activity were prepared by in situ intercalation of anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin and its complexes with Zn(II) and Pd(II) (MTSPP, M = 2H, Zn(II) and Pd(II)) into gadolinium layered hydroxide (LHGd). The combination of powder XRD, CHNS analysis, FT-IR, EDX, and TG confirmed the layered structure of the reaction products. The basal interplanar distances in LHGd-MTSPP samples were 22.3–22.6 Å, corresponding to the size of an intercalated tetrapyrrole molecule. According to SEM data, LHGd-MTSPP hybrids consisted of individual lamellar nanoparticles 20–50 nm in thickness. The enzyme-like activity of individual constituents, LHGd-Cl and sulfoporphyrins TSPP, ZnTSPP and PdTSPP, and hybrid LHGd-MTSPP materials, was studied by chemiluminescence analysis using the ABAP/luminol system in phosphate buffer solution. All the individual porphyrins exhibited dose-dependent antioxidant properties with respect to alkylperoxyl radicals at pH 7.4. The intercalation of free base TSPP porphyrin into the LHGd preserved the radical scavenging properties of the product. Conversely, in LHGd-MTSPP samples containing Zn(II) and Pd(II) complexes, the antioxidant properties of the porphyrins changed to dose-dependent prooxidant activity. Thus, an efficient approach to the design and synthesis of advanced LHGd-MTSPP materials with switchable enzyme-like activity was developed.

A selective method has been suggested for the synthesis of highly dispersed powders of γ-WO3 (monoclinic) and β-WO3⋅H2O (orthorhombic) by the hydrothermal treatment of aqueous suspensions of peroxotungstic acid in temperature range 70–250°С. The hydrothermal treatment of suspensions of peroxotungstic acid leads to formation of monophase β-WO3⋅H2O at temperature up to 100°С and monophase γ-WO3 at 250°С. The hydrothermal treatment in the temperature range 120–200°С gives two-phase samples of γ-WO3 and β-WO3⋅0.33H2O (orthorhombic syngony). The obtained monophase and two-phase powders have been studied by X-ray powder diffraction, scanning electron microscopy, IR spectroscopy, thermal analysis, and diffuse reflectance spectroscopy.

The long-term (longer than 30 days) stability of dispersions in formamide of layered REE (Y, Gd, and Eu) hydroxides intercalated with dodecyl sulfate anion has been studied for the first time. It has been shown that layered yttrium, gadolinium, and europium hydroxides intercalated with dodecyl sulfate anion react with formamide to form [Ln(HCOO)3 · 2(HCONH2)] (Ln = Y, Gd, or Eu). The structure of the obtained compounds has been determined by single-crystal X-ray diffraction. Obtained data indicate that the colloidal solutions of quasi 2D crystals of layered REE hydroxides in formamide remain stable for several days.

The hydrothermal treatment of neutral and acidified KMnO4 solutions at concentration of 0.037–0.093 mol/L and temperature of 120, 170, and 220°С for 24 h leads to selective synthesis of three different manganese dioxide modifications: α-MnO2, δ-MnO2, and β-MnO2. The temperature of hydrothermal treatment and medium acidity has been shown to affect considerably the phase composition of KMnO4 reduction products and reaction yield. The obtained samples of MnO2 have been characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and diffuse reflectance spectroscopy.

The synthesis and crystal structure of the first molecular yttrium lactate complex, Y(Lac)3(H2O)2, is reported, where the coordination sphere of yttrium is saturated with lactate ligands and water molecules, resulting in a neutral moiety. In Y(Lac)3(H2O)2, hydrogen bonding between α-hydroxy groups and water molecules allows for the formation of 2D layers. A subtle variation in synthetic conditions, i.e. a slight increase in pH (5.5 instead of 4.5) promoted the formation of a semi-amorphous fibrous material with a presumed chemical composition of Y4(OH)5(C3H5O3)7·6H2O. The flattened fibres in this material are responsible for its good flexibility and foldability.

Ceric hydrogen phosphate gels possess a very unique spatial organization, being nearly amorphous materials with a fibrous structure. Using a sol–gel approach, we succeeded in preparing bulky gels containing as much as 20,000 molecules of water per cerium atom. Supercritical treatment of these gels made it possible to obtain the first ultralight monolithic noncarbonaceous aerogels with a density as low as 1 mg/cm3.

The review summarizes the data on the chemical composition, crystal structure and functional properties of layered rare-earth hydroxides (LRHs), a new family of anion-exchangeable inorganic compounds. Comprehensive information is given on methods for the synthesis of LRHs including hydrothermal and hydrothermal-microwave treatment. Particular attention is paid to the methods of chemical design of hybrid functional materials based on LRHs. Prospects for fabrication of phosphors, heterogeneous catalysts and biomedical materials based on LRHs are analyzed. The bibliography includes 295 references.

A series of structurally characterized ionic complexes, namely [Co(MeCN)6][Sm(NO3)5] (1), [Co(bpy)3][Sm(NO3)5]·xMeOH (2) and [Co(phen)3][Sm(NO3)5]·xMeCN (3) was comprehensively studied as possible simple precursors for polycrystalline SmCoO3 perovskite. Thorough study of solid-state thermolysis revealed that in the case of 1, single-phase SmCoO3 forms even under an inert atmosphere, i.e. without external Co2+ to Co3+ oxidants. On air, thermolysis of all the complexes readily affords polycrystalline SmCoO3. Corresponding samples prepared from precursors 1 and 3 were monophasic, whereas little Sm2O3 crystalline admixture is always present in samples prepared from 2. All the oxide samples were also studied by means of IR spectroscopy, SEM and EDX. As a result, the effect of the initial precursor on the composition and morphology was established. A simplicity of precursors 1–3 together with their good solubility in some common organic solvents make them promising in further development of LnCoO3-based materials in various morphologies (deposited films, etc.). To the best of our knowledge, this study is also the first comparative one within particular series of structurally characterized precursors for successful preparation of corresponding complex oxide.

The reaction of divanadium pentoxide and N,N-dimethylformamide under hydrothermal conditions at 180–250°C has been studied. Depending on the temperature and duration (1–7 days) of hydrothermal synthesis, the reaction of V2O5 and (CH3)2N–CHO has been shown to lead to single-phase powders of [(CH3)2NH2]V3O7, VO2(D), and V2O3 in a yield up to 50–85%. Variation of initial pH value of reaction mixtures within 0.5–3.7 and molar ratio V2O5 : (CH3)2N–CHO in the range 1 : 5–1 : 50 provides no considerable effect on the phase composition of synthesis products.

Single-phase Sr1– x – yYbxEuyF2+ x + y solid solutions with an average particle size near 90 nm have been synthesized via co-precipitation from aqueous solutions, followed by high-temperature annealing. Efficient Yb3+ luminescence was observed upon excitation at a wavelength of 266 nm. The highest external quantum yield of ytterbium luminescence (2.5%) under pumping at a wavelength of 266 nm was reached for the SrF2:Yb(1.0 mol %),Eu(0.05 mol %) composition.

Rapid expansion of supercritical suspensions was used for the first time to push apart the layers in a layered metal hydroxide structure. Treatment with supercritical CO2 resulted in significant changes in interlayer distances in yttrium hydroxide intercalated with dodecyl sulfate anions. According to XRD, SEM, TEM, nitrogen adsorption and IR-spectroscopy measurements, the structure and composition of the layered material depended substantially on the pressure of supercritical CO2. Low pressure treatment (75–200 atm) resulted in a significant increase (by 20%) in the interlayer distance, while higher pressures did not affect the interlayer distance, but increased the specific surface area of the material (from ∼10 to 74 m2/g). Supercritically treated layered yttrium hydroxide exfoliated readily in toluene under ultrasonication. The re-assembly of exfoliated layers upon solvent evaporation was identified using time-resolved XRD. No effect of supercritical CO2 treatment was observed for layered yttrium hydroxide intercalated with nitrate, oleate and stearate anions.

Single-phase solid solutions based on calcium fluoride doped with ytterbium and cerium trivalent ions were synthesized by co-precipitation from aqueous solutions. According to scanning electron microscopy, the average particle size was 225 nm. Luminescence kinetics analysis has shown significant energy transfer from Ce3+ to Yb3+ under excitation at 266 nm. The lifetime of the Yb3+ luminescence in the Ce/Yb doped samples was higher in comparison to the samples having Pr/Yb double activation. At the same time, we have not been able to detect Ce3+ luminescence. Direct measurements of down-conversion Yb3+ luminescence quantum yield have been performed using an integrating sphere. The maximum quantum yield (5.6%) of ytterbium luminescence, upon 266 nm pumping, was recorded for the CaF2:Ce(0.1 mol%):Yb (10 mol%) sample.

Luminescent nanocomposite films, containing SrF 2 :Но up-conversion particles, were prepared by two different protocols from aqueous dispersions of TEMPO-oxidized cellulose nanofibrils (TOCNF) functionalized with 3-aminopropyltriethoxysilane (APS) without the use of organic solvents at pH = 4.0-4.5 and 9.0-9.5, respectively. Proposed synthetic protocols included formation of the films by drying the dispersions containing pre-hydrolyzed APS adsorbed onto TOCNF and SrF 2 :Но particles followed by heating at 105 °C. Hydrophobic (water contact angle 101 ± 2°), strong, and translucent TOCNF/SrF 2 :Но-APS films were prepared by casting from a solution at pH = 4.0-4.5. Scanning electron microscopy, energy-dispersive X-ray spectroscopy with element mapping, Fourier-transform infrared spectroscopy, X-ray diffraction methods confirmed homogeneous distribution of up-conversion particles in TOCNF matrices as well as the grafting of linear polysiloxanes via the condensation of silanol groups and OH-groups on the surface of TOCNF. Differential scanning calorimetry and thermogravimetry data confirmed an increase in thermal stability of the APS modified nanocomposite films obtained at pH = 4.0-4.5. Hydrophobic TOCNF/SrF 2 :Но-APS nanocomposite films exhibited an intense red luminescence in the visible spectrum range ( 5 I 7 level excitation of Ho 3+ ions with 1912 nm laser irradiation) as well as two-times higher laser damage threshold compared to unmodified TOCNF/SrF 2 :Но films. TOCNF/SrF 2 :Но films can be used for visualization 2 μm laser radiation in medicine and long-distance atmosphere monitoring.

International audience; Using ferrocenecarboxylic acid (FcCO 2 H) and triethanolamine (H 3 tea) as ligands, the isostructural heterotrimetallic complexes [Ln III 2 Cr III 2 (OH) 2 (FcCO 2) 4 (NO 3) 2 (Htea) 2 ]•2MePh•2THF (Ln = Tb (1), Dy (2), Ho (3), Er (4), and Y (5); Fc = (η 5-C 5 H 4)(η 5-C 5 H 5)Fe; H 3 tea = N(CH 2 CH 2 OH) 3) were obtained. In all of the complexes which possess a defective dicubane structure, two doubly deprotonated triethanolamine ligands chelate the chromium ions. However, during the synthesis of 1, an isomeric complex 1a in which Tb 3+ is chelated by triethanolamine as a tetradentate ligand, was also isolated as a few single crystals. Magnetic susceptibility measurements revealed dominant antiferromagnetic interactions in the {Ln III 2 Cr III 2 } cores of 1-4 leading to the formation of complexes with an uncompensated magnetic moment, while weak Cr-Cr ferromagnetic interactions were detected in the Y analogue. Complexes 1, 2, and 3 exhibit single-molecule magnet properties dominated by an Orbach-type relaxation mechanism with magnetization reversal barriers (Δ/k B) estimated around 54, 75, and 47 K, respectively. The Dy complex exhibits a magnetization hysteresis in an applied magnetic field at temperatures below 4 K. Thermolysis of the complexes was studied by TGA and DSC techniques; the final products obtained under an air atmosphere contain mixed oxide Cr 0.75 Fe 1.25 O 3 and heterotrimetallic oxide LnCr 1−x Fe x O 3 (with x ≈ 0.75) phases.

We determined compositions with high down-conversion characteristics from UV and blue spectral range to Yb luminescence based on luminescence studies, which are promising for efficiency increasing of silicon solar cells.

To date, the mechanisms of CaCO3 nucleus formation and crystal growth induced by bacterial cells still remain debatable. Here, an insight on the role of planktonic cells of Bacillus licheniformis DSMZ 8782 in the biomineralization is presented. We showed that during 14-days bacterial growth in a liquid urea/Ca2+-containing medium the transformation of CaCO3 polymorphs followed the classical pathway “ACC-vaterite-calcite/aragonite”. By microscopic techniques, we detected the formation of extracellular matrix (ECM) around the cells at the stage of exponential growth and appearance of electron-dense inclusions at 24 h after the inoculation. The cells formed filaments and created a network, the nodes of which served as sites for further crystal growth. The ECM formation accompanied with the expression of proteins required for biofilm formation, the aldehyde/alcohol dehydrogenase, stress-associated Clp family proteins, and a porin family protein (ompA ortholog) associated with bacterial extracellular vesicles. We demonstrated that urea and CaCl2 acted as denaturing agents causing matrix formation in addition to their traditional role as a source of carbonate and Ca2+ ions. We showed that CaCO3 nucleation occured inside B. licheniformis cells and further crystal growth and polymorphic transformations took place in the extracellular matrix without attaching to the cell surface. The spatial arrangement of the cells was important for the active crystal growth and dependent on environmental factors. The extracellular matrix played a double role being formed as a stress response and providing a favorable microenvironment for biomineralization (a high concentration of ions necessary for CaCO3 crystal aggregation, fixation and stabilization).

Hydrophobic up-conversion nanocomposite films have been developed based on TEMPO-oxidized cellulose nanofibrils (TOCNF) modified with alkyl ketene dimer (AKD) as a matrix and MF2:Ho (M = Ca, Sr) as a phosphor. Fabrication of homogeneous, strong and translucent TOCNF/MF2:Ho-AKD films with water contact angle of 123 ± 2° was accomplished with mild drying at 110 °C. These hydrophobic nanocomposite films demonstrated stable up-conversion luminescence in the visible spectral range upon excitation of the 5I7 level of Ho3+ ions by laser irradiation at 1912 nm both under ambient conditions and in a humid atmosphere (92 ± 2% humidity). The absence of luminescence quenching in a high humidity atmosphere for TOCNF/MF2:Ho-AKD composite films was considered to be due to the reliable shielding effect of the hydrophobic TOCNF-AKD matrix. The films show promise for visualizing 2 μm laser radiation in medicine and monitoring of the atmosphere.

The reduction of vanadium pentoxide with formamide under hydrothermal–microwave treatment at 180–210 °C allows for the selective synthesis of ammonium hexavanadate(V) (NH4)2V6O16, ammonium trivanadate(IV,V) (NH4)2V3O8 or ammonium vanadate(IV,V) with the hypothesized composition of (NH4)0.22V2O5. An increase in both the temperature of the hydrothermal reaction and the molar ratio of the reagents (HC(O)NH2:V2O5) promotes the reduction of vanadium(V) to vanadium(IV). The synthesis is time-saving and provides a sufficiently high yield of single-phase reaction products (up to 60–70%). Our data call into question the existence of a recently reported crystalline ammonium tetravanadate(IV), (NH4)2V4O9.

Praseodymium- and ytterbium-doped calcium fluoride powder samples were prepared by co-precipitation from aqueous solutions followed by annealing at 600 °C. Phase and microstructure analyses of these fluorite-type solid solution samples were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which have demonstrated the average particle size to be about 30 nm, ∼100 nm after drying at 45 °C and annealing at 600 °C, respectively. The fluorescence studies under 443 nm excitation in 3H4 – 3P2 band of Pr3+ ions allowed us to determine the optimal chemical compositions of CaF2:Yb:Pr samples with the high Pr3+->Yb3+ energy transfer efficiency exceeding 90% and down-conversion luminescence efficiency up to 50%. The optimal compositions are: Yb:Pr = 10.0:0.05; 10.0:0.1; and 5.0:0.05 mol%. This confirms that the energy transfer from praseodymium to ytterbium occurred via quantum cutting mechanism, and the optimal composition for highly efficient phosphor application appears to be CaF2:Yb(10.0 mol%):Pr(0.1 mol%).

Nanocrystalline manganese dioxide have been prepared by hydrothermal microwave treatment of mixed solutions of potassium permanganate and 2,4,6-triamino-1,3,5-triazine (melamine) in pH range 0.5–3. Phase and chemical composition and morphology of the samples was studied by XRD, Raman spectroscopy, and SEM. Conditions (solution pH and temperature) for the formation of single phase MnO2 powders (α-MnO2, γ-MnO2, δ-MnO2, and δ*-MnO2) under hydrothermal microwave treatment were determined.

The effect of polyoxyethylene ethers as surfactants on the morphology of NH4TiOF3 crystals obtained by hydrolysis of (NH4)2TiF6 in the presence of boric acid is analyzed. Depending on the molecular weight of the polyoxyethylene ether, the geometric dimensions (thickness and lateral size) of the crystals change. The obtained samples were characterized by X-ray and electron diffraction, Raman spectroscopy, and scanning electron microscopy. The heat treatment of NH4TiOF3 powders gives anatase mesocrystals retaining the initial particle morphology.

Crystalline inclusions of antimony compounds in lead glass of the nineteenth century have been investigated by means of transmission electron microscopy, scanning electron microscopy, X-ray microanalysis, electron backscatter diffraction and microcathodoluminescence. Microcrystallites of orthorhombic $$\hbox {KSbOSiO}_4$$ (KSS) with the sizes ranging from about 200 nm to several micrometers have been detected in lead–potassium glass of turquoise seed beads prone to a glass disease causing the irrecoverable deterioration of beaded articles kept in museums. The KSS crystals have high number density and tend to form large colonies. Crystallites of cubic $$\hbox {Pb}_2\hbox {Fe}_{0.5}\hbox {Sb}_{1.5}\hbox {O}_{6.5}$$ have been detected in stable yellow lead glass beads. Their number density and sizes are much less than those of the KSS particles observed in turquoise glass; they do not form large clusters. We have come to conclusion that KSS precipitates are responsible for the internal strain-induced corrosion of turquoise lead–potassium glass eventually resulting in crumbling of beads to sand particles. The following scenario explains this phenomenon: $$\hbox {K}^+$$ and $$\hbox {Sb}^{5+}$$ used for glass doping form KSS crystallites during glass melting; tensile strain arising in the glass matrix during cooling because of difference in temperature coefficients of linear expansion of glass and KSS crystals gives rise to crack formation and in course of time results in glass falling apart to heterogeneous pieces. Small crystallites of $$\hbox {Pb}_2\hbox {Fe}_{0.5}\hbox {Sb}_{1.5}\hbox {O}_{6.5}$$ cannot induce a sufficient strain to break yellow lead glass, and internal cracks do not arise in this glass during its cooling. This may explain the stability of yellow lead glass.

A facile procedure was developed for the production of Al2O3 aerogels modified with tris(8-hydroxyquinolinato)aluminum complex (AlQ3). The addition of 8-hydroxyquinoline during the stage of alumina lyogel formation was found to increase gelation duration. The translucent monolithic aerogels were obtained by supercritical drying of lyogels in CO2. The composition and properties of aerogels were analyzed using low-temperature nitrogen adsorption, helium pycnometry, IR spectroscopy, UV–visible spectroscopy, luminescence spectroscopy, powder X-ray diffraction, scanning and transmission electron microscopy, and thermogravimetry combined with mass spectrometry. The obtained aerogels had low density (0.15–0.18 g cm−3), high specific surface area (480–550 m2/g), high porosity (90–95%), and showed bright luminescence upon excitation in the UV range.

Ytterbium-doped single crystals of the high-temperature hexagonal sodium sulphate modification are grown by the Czochralski method. It is found by energy dispersive analysis that the crystallisation occurs congruently. The Yb : Na2SO4 crystals have additional (with respect to Yb3+ ions) absorption bands in the regions of 650, 850 and 1150 nm, which obviously belong to colour centres. The luminescence spectrum of the Yb : Na2SO4 single crystal noticeably differs from the luminescence spectrum of Yb : YAG crystals by the presence of a broad band without a prominent peak. The luminescence decay curve for the powder is single-exponential with a time constant of 1175 μs, which is somewhat larger than that for the Yb : YAG crystal. The lifetime of the ytterbium excited state does not change during storage of the samples in air for a week.

A new facile method is proposed for the preparation of aqueous sols of highly crystalline tungsten trioxide with a particle size of 60–150 nm, containing no organic stabilizers/surfactants. These sols possess high sedimentation stability, which is quite unusual for inorganic colloidal systems containing relatively large particles, with a rather high density (ρ c(WO3) = 7.3 g/cm3). The method is based on the thermal decomposition of ammonium paratungstate, followed by dispersing the resulting powders in water under ultrasonic treatment. Thermal decomposition of ammonium paratungstate, and the composition and structure of the resulting tungsten trioxide and its aqueous dispersions, were investigated with thermal analysis combined with the mass spectrometry of gaseous thermolysis products, powder X-ray diffraction, scanning electron microscopy, low-temperature nitrogen adsorption, IR spectroscopy and dynamic light scattering. It has been demonstrated that the high sedimentation stability of WO3 results from electrostatic stabilization, which might be caused by the formation of tungstic acid on the surface of WO3 particles when they come into contact with water. The nanocrystalline WO3 obtained can be used to produce gas sensors for ammonia.

It has been shown for the first time that the use of hydrogen peroxide allows precipitation of rare earth orthophosphates (La–Tb) from phosphoric acid solutions at temperatures below 100°C. Either anhydrous or hydrated orthophosphates with monazite or rhabdophane structure, respectively, can be obtained depending on rare earth element position in lanthanide series and precipitation conditions (orthophosphoric acid and hydrogen peroxide concentration). Hydrated orthophosphates with rhabdophane structure can be prepared by precipitation with hydrogen peroxide for all studied rare earth elements.

The first member, Y2(OH)5.46(B12H12)0.23Cl0.08·4.98H2O, of a new family of boron-containing substances, closo-dodecaborate intercalated layered rare-earth hydroxides, was synthesized using a microwave-assisted hydrothermal method. The structure and composition of this compound were studied by X-ray diffraction, transmission and scanning electron microscopy, thermal analysis, inductively coupled plasma mass spectrometry, IR spectroscopy, and X-ray photoelectron spectroscopy. The title compound had the composition Y2(OH)5.46(B12H12)0.23Cl0.08·4.98H2O and crystallized in a form of plate-like, aggregated particles less than 10 nm thick. The coordination of closo-dodecaborate anions with yttrium hydroxide host layers was demonstrated.

A number of Eu-doped layered yttrium hydroxides intercalated with various benzenedicarboxylate (phthalate, isophthalate and terephthalate) and sulphobenzoate (2-, 3- and 4-sulphobenzoate) anions were obtained using hydrothermal microwave (HTMW) treatment. For the first time, phthalate, isophthalate and sulphobenzoate anions were intercalated into layered rare-earth hydroxides (LRHs). Two approaches for the synthesis of intercalated layered yttrium hydroxides were used: ion exchange reactions and homogeneous hydrolysis of rare-earth cations in the presence of intercalated anions. Ion-exchange reactions between layered rare-earth hydroxides and a series of benzenedicarboxylic and sulphobenzoic acid salts were performed under the conditions of HTMW treatment, which significantly increased the rate of intercalation. The structure of the first representative of layered rare-earth hydroxides intercalated with sulphobenzoate-type anions, namely layered yttrium hydroxide intercalated with 4-sulphobenzoate of the composition Y3(OH)7(C7H4O5S)·H2O, was solved. Intercalation of benzenedicarboxylate and sulphobenzoate anions into Eu-doped layered yttrium hydroxides led to a substantial sensitization of Eu3+ luminescence. The local symmetry of Eu3+ was greatly decreased by intercalation of benzenedicarboxylate and sulphobenzoate anions.

A new selective method for the synthesis of nanocrystalline manganese dioxide (α-, β-, and γ-MnO2) based on the reaction of potassium permanganate with 2,4,6-triamino-1,3,5-triazine (melamine) under hydrothermal conditions has been proposed. Effect of synthesis conditions on the phase composition of the products has been revealed. A new manganese-containing phase with layered structure has been prepared.

It has been proposed to conduct the synthesis of cerium(III) orthophosphates by reacting cerium(IV) compounds with hydrogen peroxide in the presence of concentrated orthophosphoric acid at ambient temperature. It has been shown that the reaction of H2O2 with CeO2 suspensions in H3PO4 medium produces CePO4 · xH2O (rhabdophane structure), while that with CeO2 solutions in concentrated H3PO4 results in CePO4 (monazite structure).

The down-conversion luminescence under UV excitation was demonstrated in single-phase Ba4Y3F17 solid solution nanoparticles codoped with Ce3+/Yb3+. The complex photodynamic processes occurred in the samples including excited state absorption, excitons and color centers formation. The Yb doping suppressed the solarization effect. The efficiency of down-conversion from UV to near IR luminescence of Yb3+ appeared to be high due to Ce4+-Yb2+ charge transfer mechanism responsible for energy transfer between Ce3+ and Yb3+ ions. The direct measurements of down-conversion luminescence quantum yield by means of integrating sphere and calculations of energy transfer efficiency from luminescence spectra data were carried out. The down-conversion luminescence quantum yield reached the maximum value of about 1% for the sample with 0,1 mol.% of Ce3+ and 5,0 mol.% of Yb3+ ions contents, whereas energy transfer coefficient reached its maximum of about 6,3% for 0,05 mol.% of Ce3+ and 5,0 mol.% of Yb3+ ions.

Increasing requirements for environmental protection have led to the need for the development of control systems for exhaust gases monitored directly at high temperatures in the range of 300–800 °C. The development of high-temperature gas sensors requires the creation of new materials that are stable under these conditions. The stability of nanostructured semiconductor oxides at high temperature can be enhanced by creating composites with highly dispersed silicon carbide (SiC). In this work, ZnO and SiC nanofibers were synthesized by electrospinning of polymer solutions followed by heat treatment, which is necessary for polymer removal and crystallization of semiconductor materials. ZnO/SiC nanocomposites (15–45 mol % SiC) were obtained by mixing the components in a single homogeneous paste with subsequent thermal annealing. The composition and microstructure of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The electrophysical and gas sensing properties of the materials were investigated by in situ conductivity measurements in the presence of the reducing gases CO and NH3 (20 ppm), in dry conditions (relative humidity at 25 °C RH25 = 0) and in humid air (RH25 = 30%) in the temperature range 400–550 °C. The ZnO/SiC nanocomposites were characterized by a higher concentration of chemisorbed oxygen, higher activation energy of conductivity, and higher sensor response towards CO and NH3 as compared with ZnO nanofibers. The obtained experimental results were interpreted in terms of the formation of an n–n heterojunction at the ZnO/SiC interface.

We synthesized MF 2 :Yb:R (M = Ca, Sr; R = Pr, Ce, Eu) powders by a different kind of precipitation techniques. We determined optimal compositions with a quantum efficiency of photon transfer about 190 % (quantum cutting). In finally, we approached quantum cutting phenomenon. It’s useful for increasing of crystalline silicon solar cell efficiency.

The influence of ultrasonic treatment on the micro􏰀 and mesostructures and fractal characteristics of amorphous powders of yttrium and aluminum basic salts (precursors for the synthesis of neodymium􏰀acti􏰀 vated yttrium–aluminum garnet, Nd:YAG, which were coprecipitated from aqueous solutions by different precipitants, namely, aqueous solutions of ammonia and ammonium bicarbonate) is studied. It is established that ultrasonication applied during the precipitation of the aforementioned powders does not significantly change the structure of the obtained materials but always leads to the formation of structures with a less homogeneous nuclear density, i.e., a more developed surface area. Moreover, the ultrasound􏰀assisted precip􏰀 itation of the hydroxocompounds by ammonium hydrocarbonate results in a certain increase in the surface fractal dimension and the degree of aggregation for mass􏰀fractal aggregates of particles.

Crystallization processes in the Bi2O3-Fe2O3-NaOH system upon microwave-assisted hydrothermal synthesis have been studied to reveal the effect of the mineralizer concentration, temperature, degree of filling of the autoclave, and the preparation of precursors on the phase composition and the morphology of the reaction product. Submicron powders of bismuth ferrite Bi2Fe4O9 have been synthesized.

A stable yttrium peroxo compound containing 6.7% active (peroxide) oxygen is prepared by reacting layered yttrium hydroxonitrate Y4(OH)10(NO3)2 · xH2O with 12% or 87% aq. H2O2 at 0°C. The active oxygen in this compound is in the form of HO 2 - - and O 2 2- - groups as probed by IR and Raman spectroscopy. The thermolysis of the yttrium peroxo compound yields nanosized (6 nm) yttrium oxide.

In the present work, we have studied for the first time the combined effect of both sonication and precipitation pH on the structure of amorphous zirconia gels synthesized from zirconium(IV) propoxide. The techniques of small-angle neutron and X-ray scattering (SANS and SAXS) and low temperature nitrogen adsorption provided the integral data on the changes in the microstructure and mesostructure of these materials caused by ultrasonic (US) treatment. Amorphous ZrO2.xH2O synthesized under ultrasonic treatment was found to possess a very structured surface, characterized by the surface fractal dimension 2.9-3.0, compared to 2.3-2.5 for the non US-assisted synthesis, and it was also found to possess a higher specific surface area, while the sizes of the primary particles remain unchanged.

The reaction between yttrium nitrate and potassium hydroxide solutions was conducted at 25 and 50°C and at the boiling point of the reaction mixture, and the reaction products were studied. The Schreinemakers method, X-ray diffraction and crystal-optical analyses, IR spectroscopy, and electron microscopy demonstrated that X-ray amorphous yttrium hydroxide Y(OH)3 and basic yttrium nitrate Y(OH)2.5(NO3)0.5 · H2O are formed at 25 and 50°C as a poorly crystallized precipitate depending on the ratio between the initial reagents. Keeping the reaction products at the boiling temperature gives rise to a well-crystallized sample of basic yttrium nitrate.