Laboratory of Synthesis and Growth of single crystals of REE compounds
Head of Laboratory
Naumov, Nikolay G
Publications
173
Citations
3 028
h-index
32
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Development of methods for the synthesis of sulfide oxide rare earth compounds; the influence of dimension, structure and composition on their properties. Investigation of phase equilibria and thermodynamics of multicomponent systems based on oxides and chalcogenides of transition and rare earth metals. Development of the physico-chemical foundations for the formation of nanostructured materials from the gas phase and liquid solutions; kinetics and mechanism of the processes.
- Inorganic synthesis
Nikolay Naumov
Head of Laboratory
Maria Tarasenko
Senior Researcher
Publications and patents
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Ledneva A.Y., Naumov N.G., Kyritsakas N., Ferlay S.
The combination of cation of 1,4-diamidiniumbenzene hydrochloride (H2DAB∙Cl2) with [Re6Q8(CN)6]4– (Q = S, Se) or [Re6S8(CN)4(OH)2]4– leads to solid-state compounds of formula (H2DAB)2[Re6Q8(CN)6]∙nH2O (Q = S, n = 2.5 (1) or Q = Se, n = 2 (2)), and (HDAB)2[Re6S8(CN)4(H2O)2]∙7H2O (3). Two isostructural compounds are formed through the monohapto recognition mode between H bond donors (H2DAB2+) and H bond acceptors (the –CN moieties of the cluster anions). A 2D system involving water molecules was formed, whereas with the disordered [Re6S8(CN)4(H2O)2]2– anion, a deformed diamondoid porous compound was obtained. Moreover, amidinium cation becomes partially deprotonated (HDAB+). These are rare examples of reliable charge assisted H bonded network involving Re cyanide clusters.
Pustovarov V.A., Tavrunov D.A., Ryzhikov M.R., Tarasenko M.S., Naumov N.G.
A series of single crystals of CsLa1-хСехSiS4 monophasic solid solution (x = 0–1) has been obtained for the first time by high-temperature flux synthesis. Methods of XRD and chemical analysis, absorption and low-temperature (from T = 5 K) luminescent spectroscopy were used. The results of the band scheme calculating using density functional theory correlate with spectroscopy data. One non-elementary d → f emission band of Ce3+ ions is observed in the region of 520 nm in the luminescence spectra at room temperature at any value of the x parameter. The luminescence decay kinetics of Ce3+ ions upon excitation by a pulsed electron beam, X-ray synchrotron radiation or intracenter photoexcitation is characterized by a nanosecond component. As the parameter x increases, the decay time is reduced from 132 ns (x = 0.005) to 0.88 ns (x = 1). The luminescence decay kinetics upon photoexcitation at x = 0.005–0.12 is characterized by monoexponential decay with τ = 31.4 ± 0.2 ns. Concentration quenching of the Ce3+ ion photoluminescence is not observed up to the value of the parameter x = 0.12; it only appears at x = 1. The anomalously short decay time of the Ce3+ ions luminescence in CsCeSiS4 upon both X-ray excitation and photoexcitation is associated with concentration quenching. At temperature 5 K, new intense bands at 408 and 688 nm in addition to the Ce3+ emission band observed in the photoluminescence spectra of nominally pure CsLaSiS4 or at the lowest parameter value x = 0.005. These bands correspond to the luminescence of self-trapped excitons (STE) and defects. With increasing x parameter, the STE emission band is reabsorbed by the absorption of Ce3+ ions and is quenched due to the resonance energy transfer STE → Ce3+ center. Thermoluminescence glow curves of CsLa1-xCexSiS4 irradiated with X-ray at T = 90 K are characterized by several low temperature intense peaks, which indicates a high concentration of charge carrier traps.
Gaifulina V.K., Gaifulin Y.M., Ryzhikov M.R., Ulantikov A.A., Yanshole V.V., Naumov N.G.
Ledneva A.Y., Naumov N.G., Kyritsakas N., Ferlay S.
Two novel compounds based on [Re6Q8(CN)6]4– (Q = S, Se) and a small H-bond donor bis-amidinium dication of 2,2’-methylenediimidazolium (Cat) (Cat)2[Re6S8(CN)6]∙2H2O (1) and (Cat)2[Re6Se8 (CN)6]∙2H2O (2) are synthesized and structurally characterized. The dimensionality (2D or 3D) of the obtained network and the nature of the H-bond pattern change depending on the chalcogen atom (S or Se) in the cluster anion.
Lappi T.I., Cordier S., Gayfulin Y., Ababou-Girard S., NGAN N.T., Grasset F., Uchikoshi T., Naumov N.G., Renaud A.
The mixing of rhenium and molybdenum within the same heterometallic cluster enables to modulate optoelectronic properties of the photo-active layers. Such {Re4Mo2Q8}-based photoelectrodes appear promising for the photoelectrochemical water splitting.
Lappi T.I., Gaifulin Y.M., Sukhikh T.S., Gaifulina V.K., Yanshole V.V., Cordier S., Naumov N.G.
The influence of the metal ratio on the geometric characteristics and crystal structures of heterometallic clusters with {Re6−xMoxQ8} cores was studied. Complexes with the same apical ligands form isostructural packings and form the solid solutions.
Yarovoy S.S., Asanov I.P., Poltarak P.A., Ivanova M.N., Fedorov V.E., Naumov N.G.
Using XPS and DFT, we have studied a series of octahedral rhenium cluster compounds: ternary thiobromides Re6S4+nBr10–2n, n = 0, 1, 3, 4 and alkali metal salts of anionic complexes [Re6S4+nBr10-n]n–, n = 1–4. These two series contain [Re6S4+nBr4-n] cluster cores, which are the building blocks of both discrete complexes and polymeric compounds, and have the same coordination polyhedron of rhenium atoms. The constancy of the coordination polyhedron of Re reduces the effect of structural differences and allows to study the change in the electronic state of the rhenium atoms of the Re6 metallocluster with increasing number of less electronegative (compared to bromine) sulfur atoms in the cluster core. This change results in the decrease in the binding energy (BE) Re 4f7/2 in the series of anionic complexes [Re6S4+nBr10-n]n–. A similar dependence is observed in the series of ternary thiobromides. Re6S8Br2 falls out of this trend, which is explained by a change in the type of binding of the cluster cores. The BE S 2p3/2 of the sulfide ligands and the BE Br 3d5/2 of the bromide ligands decrease as the number of sulfur atoms in the cluster core and the charge of anionic complexes increases. The difference in BE values for the inner Bri and apical Bra bromide ligands shows that the inner ligands are more covalent and the apical ligands are more ionic. Calculated energies of the Re 4f, S 2p, Br 3d orbitals confirm the general tendency for the energy to decrease as the number of sulfur atoms in the cluster cores increases. Calculation of the atom charges for discrete complexes [Re6S4+nBr10-n]n–, showed that with increasing number of sulfur atoms in the cluster cores, the negative charge of the ligands increases, while the charge of the rhenium atoms remains unchanged. This suggests that the chemical shift of the Re4f binding energy is determined by the potentials of the surrounding atoms (Madelung potential) and that the chemical shift of the ligands depends on the charge of the atom.
Yarovoy S.S., Sukhikh T.S., Naumov N.G.
The condensation of trinuclear rhenium bromide with lead sulfide yields the (H9O4)2Re6S6Br8 octahedral cluster complex isolated from the HBr/EtOH mixture in the form of the acid. (H9O4)2[Re6S6Br8] crystallizes in the P21/c space group, a = 9.2010(2) Å, b = 9.1508(2) Å, c = 17.3759(3) Å, γ = 101.817(1)°. Thermal decomposition of the complex at a moderate temperature (350 °C) results in a metastable Re6S6Br6 compound, which is not formed in the ternary Re–S–Br system at high temperatures. This compound is X-ray amorphous; its structure is determined based on the X-ray photoelectron and Raman spectroscopy data.
Yarovoy S.S., Sukhikh T.S., Romanova T.E., Brylev K.A., Naumov N.G.
A detailed study of the Re–S–Br system in the temperature range (650 – 1150 °C) of the formation of hexarhenium thiobromides with the general formula Re6S4+nBr10–2n, has revealed the features of phase formation and the factors influencing the production of pure phases. It was found that in reactions with a given stoichiometry 6Re + nS, a mixture of products is usually formed, namely a compound based on a cluster core with the targeted Re/S stoichiometry Re6Sn, an admixture compound with Re6Sn+1 core, and a soluble by-product (3–5% of the total mass), consisting of rhenium bromides and thiobromides. It was found that the composition of the by-product (Re/S ratio) has a significant effect on the fraction of the admixture compound with higher sulfur content. The slow cooling rate of the reaction mixture, leads to the obtaining of a pure target compound with the {Re6SnBr8–n} cluster core. In the course of the study of the Re–S–Br system, the crystal structure of Re6S7Br4 was solved (space group R–3c, a = 9.5804(2) Å, c = 31.0676(10) Å, V = 2469.48(13) Å3, Z = 6). The study of the thermal behavior showed that the stability of Re6S4+nBr10–2n increases with increasing sulfur content in the cluster core. XPRD data showed that the decomposition of octahedral cluster thiobromides leads to the formation of sulfur-rich phases. This process is accompanied by the release of elemental bromine, metallic rhenium and the formation of soluble by-products with the overall composition “Re2SBrx".
Pustovarov V.A., Tarasenko M.S., Tavrunov D.A., Naumov N.G.
Ce+3 doped CsLaSiS4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5–310 K. The energy of interband transitions Eg = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d → f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS4 crystals is proposed.
Tarasenko M.S., Nikolaev R.E., Yakovleva A.M., Trifonov V.A., Sukhikh A.S., Naumov N.G.
X-ray quality crystals of solid solutions of complex borates Li6R(BO3)3 and LiR6(BO3)3O5 (R = Y, Eu) with different europium contents are grown from a Li6R(BO3)3 melt solution with an addition of 20 mol.% of an yttrium–europium oxide mixture. The structural data show that the Y/Eu distribution over independent positions in the LiR6(BO3)3O5 crystal is nonuniform; the difference between Eu occupancies reaches 80% and correlates with the Hirshfeld volumes of these sites calculated for LiR6B3O14.
Ledneva A.Y., Ivanova M.N., Poltarak P.A., Yarovoy S.S., Kolesov B.A., Fedorov V.E., Naumov N.G.
A series of rhenium compounds with the octahedral cluster core {Re6S8-xBrx} (x = 0–4): with molecular and polymeric structure were obtained. In these compounds the cluster core composition varies monotonically, the geometry of the cluster and the rhenium coordination polyhedron are retained unchanged, while the symmetry of the cluster changes. The vibrational spectra (Raman and IR) were recorded and analyzed for compounds with all possible S/Br ratios in the cluster core. The group vibrations of clusters were attributed with the use of DFT calculations of vibrational spectra. It is shown that the set of main characteristic bands is retained in both ionic and polymeric compounds regardless of the composition and the symmetry of the cluster core while the observed vibration frequencies of these bands depend on the S/Br ratio in the cluster core. In particular, the group Re–S stretching vibrations (A1g(S8) and T2g(S8) modes) shifted to higher frequencies with the increase in the number of Br atoms in the cluster. The difference in the connectivity in polymeric compounds leads to an increase in the number of bands in the spectra and to the disappearance of the A1g(Br) modes.
Pustovarov V.A., Ogorodnikov I.N., Nikolaev R.E., Tarasenko M.S., Tavrunov D.A., Trifonov V.A., Naumov N.G.
Large-sized, high optical quality Gd2O3 single crystals were grown from a solution at T = 1145 °C using Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic (bixbyite) phase (c-phase). The absorption spectra and luminescence properties of Gd2O3 doped with Eu3+ and Tb3+ impurity ions were studied. The absorption spectrum of Gd2O3:Eu in the short wavelength region is mainly due to charge transfer transitions from O2− to Eu3+ (240–290 nm), which overlap with the Urbach tail of the host-absorption. Additionally, electronic transitions in Eu3+ (320–540 nm) and Gd3+ (245–315 nm) lanthanide ions contribute to the absorption spectrum. Intraconfigurational radiative f – f transitions in impurity ions are clearly observed upon both UV- and X-ray excitations. However, 6PJ → 8S7/2 radiative transitions in Gd3+ ions are completely unobservable. Based on the obtained spectroscopic data, the energy positions of the ground state of all di- and trivalent lanthanide ions, as well as the energies of intraconfigurational f – f and interconfigurational f – d electronic transitions in Gd2O3 crystals with a cubic structure, are calculated. The proposed electronic energy diagram is used to discuss efficient energy transfer between lanthanide ions.
Sotnikov A.V., Syrokvashin M.M., Bakovets V.V., Korotaev E.V., Gerasimov E.Y.
The Y2O3@SmS composite with a core–shell nanostructure was synthesized using the polyol sol–gel method. For the first time the oxide powder Y2O3@Sm2O3 precursor was obtained from Y2O3 and Sm(acac)3 solutions in diatomic alcohol ethylene glycol C2H4(OH)2 by the precipitation of urea (NH2)2CO. Next, the precursor was heated to 633 K in the sulfidation atmosphere and annealed at 1423 K to obtain the final Y2O3@SmS composite. It was found that Y2O3@SmS compound contains a small amount of Sm2S3 impurity phase due to the diffusion process of the sulfur atoms of SmS2 phase to the sample surface, followed by a transition of SmS2 to Sm2S3 phase. The short-range order was analyzed using both Raman and XPS spectroscopy. The obtained data showed that Y2O3@SmS composite has a core–shell structure. Y2O3 phase was considered as a core, and the SmS phase – as the shell. Using the SEM and HRTEM data it was found that synthesized sample contained a significant amount of the core–shell nanoparticles with the average size of ∼ 200 nm. The Seebeck coefficient was of –40 µV/K at 430 K. The obtained value was two times greater compared to SmS@Y2O2S and Y2O2S@SmS core–shell compounds studied previously.
Lappi T.I., Gayfulin Y.M., Renaud A., Prestipino C., Lemoine P., Yanshole V.V., Muravieva V.K., Cordier S., Naumov N.G.
A series of new cluster compounds with {Re4Mo2S8} and {Re3Mo3S8} cores has been obtained and investigated. The clusters with different Re/Mo ratios were isolated as individual compounds, which made it possible to study their spectroscopic and electrochemical properties. The geometry of the new clusters was studied using a combination of X-ray diffraction analysis, XAS and quantum chemical DFT calculations. It was shown that the properties of the new clusters, such as the number and position of electrochemical transitions, electronic structure and change in geometry with a change in charge, are similar to the properties of clusters based on the {Re4Mo2Se8} and {Re3Mo3Se8} cores described earlier.
2022
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2024
| Наумов Николай Геннадьевич
2022
—
2023
| Наумов Николай Геннадьевич
Lab address
Новосибирск, проспект Академика Лаврентьева, д. 3
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