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Samarium-sodium double sulfate crystalline hydrate NaSm(SO4)2·H2O was obtained by the crystallization from an aqueous solution containing equimolar amounts of ions. The anhydrous salt of NaSm(SO4)2 was formed by a thermally induced release of the equivalent of water from NaSm(SO4)2·H2O. The kinetic parameters of thermal decomposition were determined (Ea = 102 kJ/mol, A = 9·106). The crystal structures of both compounds were refined from the X-ray powder diffraction data. Sulfate hydrate NaSm(SO4)2·H2O crystallizes in the trigonal symmetry, space group P3121 (a = 6.91820(3) and c = 12.8100(1) A, V = 530.963(7) A3). The anhydrous salt crystallizes in the triclinic symmetry, space group P-1 (a = 6.8816(2), b = 6.2968(2) and c = 7.0607(2) A, α = 96.035(1), β = 99.191(1) and γ = 90.986(1)°, V = 300.17(1) A3). The vibrational properties of compounds are mainly determined by the sulfate group deformations. The luminescence spectra of both sulfates are similar and are governed by the transitions of samarium ions 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2 and 11/2). The anhydrous sulfate is stable up to 1100 K and undergoes an almost isotropic expansion when heated. After 1100 K, the compound decomposes into Sm2(SO4)3 and Na2SO4.

Germanate PrAlGe2O7 is obtained from initial oxides Pr2O3, Al2O3, and GeO2 via solid-phase synthesis. The crystal structure of the investigated germanate is determined via X-ray diffraction. The luminescence spectra are been determined at room temperature. The effect temperature has on the heat capacity is determined via differential scanning calorimetry. The thermodynamic properties of the complex oxide compound are calculated using the experimental data on Cp = f(T) in the temperature range of 350‒1000 K.

A double holmium-silver sulfate was obtained for the first time. The temperature intervals for the formation and stability of the compound were determined by differential scanning calorimetry. The crystal structure of AgHo(SO4)2 was determined by Rietveld method. The X-ray diffraction (XRD) analysis showed that the compound crystallizes in the monoclinic syngony, space group P21/m, with the unit cell parameters a = 4.71751 (4) A, b = 6.84940 (6) A and c = 9.89528 (9) A, β = 95.1466 (4)°, V = 318.448 (5) A3, Z = 2, RB = 1.55 %, T = 303 K. Two types of sulfate tetrahedra were found in the structure, which significantly affected the spectral properties in the infrared range. In the temperature range of 143−703 K, a negative thermal expansion along the b direction accompanied by a positive thermal expansion along the a and c directions was observed. It was established that negative thermal expansion is the result of the deformation of sulfate tetrahedra, which is affected by the movement of holmium and silver atoms. The excitation in the blue spectral range (457.9 nm) produces a luminescence in light blue (489 nm), green (545 nm) and red (654 nm) spectral ranges, and the latter two were of comparable intensity that is favorable for WLED sources. The observed luminescent band distribution is ascribed to the specific crystal field at Ho3+ ion sites rather than a variation of radiationless probability.

NdFe3(BO3)4 and NdGa3(BO3)4 crystals are of great interest due to their physical properties. For example, NdFe3(BO3)4 crystal demonstrates magnetodielectric and magnetopiezoelectric effects, and Nd...

Germanate TbGaGe2O7 has been obtained from the initial Tb2O3, Ga2O3, and GeO2 oxides by the solid-phase synthesis. The germanate structure has been established by X-ray diffraction. Room-temperature luminescence spectra of the compound have been recorded. The effect of temperature on the heat capacity of the oxide compound has been investigated by differential scanning calorimetry. The thermodynamic properties of the compound have been calculated from the experimental Cp = f(T) data.

Single crystals of SmAl3(BO3)4 were synthesized by the group growth on seeds method. The crystal structure was solved using a single-crystal experiment and the purity of the bulk material was proved by the Rietveld method. This borate crystallizes in the monoclinic C2/c space group with unit-cell parameters a = 7.2386 (3), b = 9.3412 (5), c = 11.1013 (4) Å and β = 103.2240 (10)°. IR and Raman spectroscopic analyses confirmed the monoclinic structure of SmAl3(BO3)4. Under 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2. The similarity of the luminescence spectra of the trigonal and monoclinic polymorphs is explained by the minor role of Sm—O bond distortion and the primary role of rotational distortion of SmO6 octahedra. The smaller covalency of the Sm—O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high-temperature structural phase transitions up to a temperature of 720 K.

Single crystal of HoGa3(BO3)4 has been grown using solution-melt synthesis. The optical band gap determined from the measured absorption spectrum is due to direct allowed transition and equals to 4...

New triple tungstate phosphors NaPbLa(WO4)3:Yb3+/Ho3+ (x = Yb3+/Ho3+ = 7, 8, 9, 10) are successfully fabricated by microwave assisted sol-gel synthesis and their structural and frequency upconversion (UC) characteristics are investigated. The compounds crystallized in the tetragonal space group I41/a and the NaPbLa(WO4)3 host have unit cell parameters a = 5.3927(1) and c = 11.7961(3) A, V = 343.05(2) A3, Z = 4. Under excitation at 980 nm, the phosphors have yellowish green emissions, which are derived from the intense 5S2/ 5F4 → 5I8 transitions of Ho3+ ions in the green spectral range and strong 5F5 → 5I8 transitions in the red spectral range. The optimal Yb3+:Ho3+ ratio is revealed to be x = 9, which is attributed to the quenching effect of Ho3+ ions, as indicated by the composition dependence. The UC characteristics are evaluated in detail under consideration of the pump power dependence and Commission Internationale de L'Eclairage chromaticity. The spectroscopic features of Raman spectra are discussed in terms of the superposition of Ho3+ luminescence and vibrational lines. The possibility of controlling the spectral distribution of UC luminescence by the chemical content of tungstate hosts is demonstrated.

In this work, we report on the synthesis, in-depth crystal structure studies as well as optical and magnetic properties of newly synthesized heterometallic quaternary selenides of the Eu

The process of high-temperature oxidation of EuS in the air was explored in the temperature range of 500–1000 °C. The oxidation reaction enthalpy was determined (ΔH0exp = −1718.5 kJ/mol). The study of oxidation products allowed to establish the mechanism of EuS oxidation with oxygen. At 500–600 °C, EuS is oxidized to a mixture of Eu3+-containing compounds (Eu3S4, Eu2O2S). In the range of 700–1000 °C, only europium oxysulfate Eu2O2SO4 is formed. The structure refinement for Eu2O2SO4 was performed by the Rietveld method. The luminescence intensity of europium oxysulfate Eu2O2SO4 with characteristic 4f-4f transitions from the 5D0 state was investigated as a function of oxidation temperature.

RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a = 5.13502(5), b = 18.8581(2) and c = 8.12849(7) A, V = 787.13(1) A3, Z = 4 (RB = 0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250 K. The Raman spectra were measured with the excitation at λ = 1064 and 514.5 nm. The photoluminescence spectrum is evaluated under the excitation at 514.5 nm. The absolute domination of hypersensitive 5D0→7F2 transition is observed. The ultranarrow 5D0→7F0 transition in RbEu(MoO4)2 is positioned at 580.2 nm being 0.2 nm blue shifted, with respect to that in Eu2(MoO4)3.

Mn5Ge3 films are promising materials for spintronic applications due to their high spin polarization and a Curie temperature above room temperature. However, non-magnetic elements such as oxygen, carbon and nitrogen may unpredictably change the structural and magnetic properties of Mn5Ge3 films. Here, we use the solid-state reaction between Mn and GeO thin films to describe the synthesis and the structural and magnetic characterization of Mn5Ge3(Mn5Ge3Oy)-GeO2(GeOx) nanocomposite materials. Our results show that the synthesis of these nanocomposites starts at 180°С when the GeO decomposes into elemental germanium and oxygen and the resulting Ge atoms immediately migrate into the Mn layer to form ferromagnetic Mn5Ge3 nanoclusters. At the same time the oxygen atoms take part in the synthesis of GeOx and GeO2 oxides and also migrate into the Mn5Ge3 lattice to form Mn5Ge3Oy Nowotny nanoclusters. Magnetic analysis assumes the general nature of the Curie temperature increase in carbon-doped Mn5Ge3Cx and Mn5Ge3Oy films. Our findings prove that not only carbon, but oxygen may contribute to the increase of the saturation magnetization and Curie temperature of Mn5Ge3-based nanostructures.

Eu2(SO4)3 was synthesized by chemical precipitation method and the crystal structure was determined by Rietveld analysis. The compound crystallizes in monoclinic space group С2/с. In the air environment, Eu2(SO4)3 is stable up to 670 °C. The sample of Eu2(SO4)3 was examined by Raman, Fourier-transform infrared absorption and luminescence spectroscopy methods. The low site symmetry of SO4 tetrahedra results in the appearance of the IR inactive ν1 mode around 1000 cm−1 and ν2 modes below 500 cm−1. The band intensities redistribution in the luminescent spectra of Eu3+ ions is analyzed in terms of the peculiarities of its local environment.

AgGd(MoO4)2:Ho3+/Yb3+ double molybdates with five concentrations of Ho3+ and Yb3+ were synthesized by the microwave employed sol&ndash, gel based process (MES), and the crystal structure variation, concentration effects, and spectroscopic characteristics were investigated. The crystal structures of AgGd1-x-yHoxYby(MoO4)2 (x = 0, 0.05, y = 0, 0.35, 0.4, 0.45, 0.5)at room temperature were determined in space group I41/a by Rietveld analysis. Pure AgGd(MoO4)2 has a scheelite-type structure with mixed occupations of (Ag,Gd) sites and cell parameters a = 5.24782 (11) and c = 11.5107 (3) &Aring, V = 317.002 (17) &Aring, 3, Z = 4. In doped samples, the sites are occupied by a mixture of (Ag,Gd,Ho,Yb) ions, which provides a linear cell volume decrease with the doping level increase. Under the excitation at 980 nm, AGM:0.05Ho,yYb phosphors exhibited a yellowish green emission composed of red and green emission bands according to the strong transitions 5F5 &rarr, 5I8 and 5S2/5F4 &rarr, 5I8 of Ho3+ ions. The evaluated photoluminescence and Raman spectroscopic results were discussed in detail. The upconversion intensity behavior dependent on the Yb/Ho ratio is explained in terms of the optimal number of Yb3+ ions at the characteristic energy transfer distance around the Ho3+ ion.

Raman and optical absorption spectra of disordered hydrated iron fluoridotitanate (HITF) single crystal were studied. Temperature transformations of the Raman spectra indicate independent ordering processes of the [TiF6]2− and [Fe(H2O)6]2+ complexes below the structural phase transition. The absorption spectrum in the near-infrared and visible ranges includes transitions from the high spin ground state 5T2 of Fe2+ ion to the excited 5E state and a set of excited triplets. Analysis by Tanabe-Sugano method gives crystal field Dq = 490 cm−1 and Racah parameters B = 340 cm−1 and C = 1904 cm−1. Considerable decrease of B parameter as compared to the free ion value indicates a decrease of interelectron repulsion in the disordered neighborhood of Fe2+ ions.

Silver–europium double sulfate AgEu(SO4)2 was obtained by solid-phase reaction between Ag2SO4 and Eu2(SO4)3. The crystal structure of AgEu(SO4)2 was determined by Monte Carlo method with simulated ...

Polarized absorption spectra of ferroborates HoFe3(BO3)4, NdFe3(BO3)4 and Ho0.75Nd0.25Fe3(BO3)4 were measured at room temperature in spectral range 4000–24500 cm−1 (400–2500 nm). The studied single crystals were grown from solution-melts. Intensities of the f-f transitions were measured and the Judd–Ofelt parameters Ωλ of Ho3+ and Nd3+ ions in the studied crystals were calculated. It was revealed that the crystals content not strongly influences the Judd–Ofelt parameters. The Ω2 parameter for Ho3+ ion is the most sensitive to the crystal content. Linear dichroism of the hypersensitive transitions appeared to be the largest one for both rare earth ions.

The electronic structure, transport and optical properties of thin films of Mn4Si7 and Mn17Si30 higher manganese silicides (HMS) with the Nowotny “chimney-ladder” crystal structure are investigated using different experimental techniques and density functional theory calculations. Formation of new Mn17Si30 compound through selective solid-state reaction synthesis proposed and its crystal structure is reported for the first time, the latter belonging to I-42d. Absorption measurements show that both materials demonstrate direct interband transitions around 0.9 eV, while the lowest indirect transitions are observed close to 0.4 eV. According to ab initio calculations, ideally structured Mn17Si30 is a degenerate n-type semiconductor; however, the Hall measurements on the both investigated materials reveal their p-type conductivity and degenerate nature. Such a shift of the Fermi level is attributed to introduction of silicon vacancies in accordance with our DFT calculations and optical characteristics in low photon energy range (0.076–0.4 eV). The Hall mobility for Mn17Si30 thin film was found to be 25 cm2/V s at T = 77 K, being the highest among all HMS known before. X-ray photoelectron spectroscopy discloses a presence of plasmon satellites in the Mn4Si7 and Mn17Si30 valence band spectra. Experimental permittivity spectra for the Mn4Si7 and Mn17Si30 compounds in a wide range (0.076–6.54 eV) also indicate degenerate nature of both materials and put more emphasis upon the intrinsic relationship between lattice defects and optical properties.

New noncentrosymmetric double borate Rb3EuB6O12 was designed and synthesized by the solid state reaction method, and its crystallographic parameters were obtained by Rietveld analysis. This borate crystallizes in the trigonal space group R32 with cell parameters a = 13.4604(2) Å, c = 30.7981(5) Å, Z = 15. Its structure features a three-dimensional framework composed of the [B5O10]5− groups that are bridged by Eu-O polyhedra. The existence of B5O10 group in the structure was confirmed by vibrational spectroscopy. Rb3EuB6O12 melts incongruently at 1101 K. The second harmonic generation effect of Rb3EuB6O12 is 16 times higher than that of the α-quartz standard. In the luminescence spectrum, the domination of a single prominent narrow line from the hypersensitive 5D0 - 7F2 manifold of Eu3+ ions is observed, while the 5D0 - 7F1 manifold and ultranarrow 5D0 - 7F0 line are of comparable peak intensity. These features are explained by a specific local symmetry of the Eu3+ ion within the crystal structure of Rb3EuB6O12. Keywords: Rubidium rare earth borate, Solid state reaction, Rietveld refinement, Raman, Infrared spectroscopy, Luminescence

The crystal structure of new monoclinic molybdate BaSm 2 (MoO 4 ) 4 is refined in monoclinic unit cell C 2/ m with cell parameters a = 5.29448 A, b = 12.7232 A, c = 19.3907 A, β = 91.2812°, V = 1305.89 A 3 . The crystal structure consists of the SmO 8 square antiprism joined with each other by the edges forming a 2D layer perpendicular to the c -axis. MoO 4 tetrahedra join SmO 8 by nodes and also participate in layer formation, and Ba ions are located between these layers. The lattice dynamics is theoretically calculated on the base of the crystal structure data. The Raman spectra are recorded and analyzed in comparison with theoretical calculations. The discrepancy between the experimental and calculated Raman frequencies does not exceed 2 cm −1 for the most of Raman lines. The luminescence spectra of Sm 3+ ions, which are positioned in the lowest local symmetry site C 1 , strongly differ from those detected for another molybdate crystal, β-RbSm(MoO 4 ) 2 , with the C 2 local symmetry. The 4 G 5/2 → 6 H 9/2 band is dominating in the BaSm 2 (MoO 4 ) 4 luminescence.

Novel nanoscale bioconjugates combining unique plasmonic photothermal properties of gold nanoparticles (AuNPs) with targeted delivery using cell-specific DNA aptamers have a tremendous potential for medical diagnostics and therapy of many cell-based diseases. In this study, we demonstrate the high anti-cancer activity of aptamer-conjugated, 37-nm spherical gold nanoparticles toward Ehrlich carcinoma in tumor-bearing mice after photothermal treatment. The synthetic anti-tumor aptamers bring the nanoparticles precisely to the desired cells and selectively eliminate cancer cells after the subsequent laser treatment. To prove tumor eradication, we used positron emission tomography (PET) utilizing radioactive glucose and computer tomography, followed by histological analysis of cancer tissue. Three injections of aptamer-conjugated AuNPs and 5 min of laser irradiations are enough to make the tumor undetectable by PET. Histological analysis proves PET results and shows lower damage of healthy tissue in addition to a higher treatment efficiency and selectivity of the gold nanoparticles functionalized with aptamers in comparison to control experiments using free unconjugated nanoparticles.

Crystalline hydrate of double cesium europium sulfate [CsEu(H2O)3(SO4)2]·H2O was synthesized by the crystallization from an aqueous solution containing equimolar amounts of 1Cs+:1Eu3+:2SO42− ions. Anhydrous salt CsEu(SO4)2 was formed as a result of the thermal dehydration of the crystallohydrate. The unusual effects observed during the thermal dehydration were attributed to the specific coordination of water molecules in the [CsEu(H2O)3(SO4)2]·H2O structure. The crystal structure of [CsEu(H2O)3(SO4)2]·H2O was determined by a single crystal X-ray diffraction analysis, and the crystal structure of CsEu(SO4)2 was obtained by the Rietveld method. [CsEu(H2O)3(SO4)2]·H2O crystallizes in the monoclinic system, space group P21/c (a = 6.5574(1) Å, b = 19.0733(3) Å, c = 8.8364(2) Å, β = 93.931(1)°, V = 1102.58(3) Å3). The anhydrous sulfate CsEu(SO4)2 formed as a result of the thermal destruction crystallizes in the monoclinic system, space group C2/c (a = 14.327(1) Å, b = 5.3838(4) Å, c = 9.5104(6) Å, β = 101.979(3) °, V = 717.58(9) Å3). The vibration properties of the compounds are fully consistent with the structural models and are mainly determined by the deformation of non-rigid structural elements, such as H2O and SO42−. As shown by the diffused reflection spectra measurements and DFT calculations, the structural transformation from [CsEu(H2O)3(SO4)2]·H2O to CsEu(SO4)2 induced a significant band gap reduction. A noticeable difference of the luminescence spectra between cesium europium sulfate and cesium europium sulfate hydrate is detected and explained by the variation of the extent of local symmetry violation at the crystallographic sites occupied by Eu3+ ions, namely, by the increase in inversion asymmetry in [CsEu(H2O)3(SO4)2]·H2O and the increase in mirror asymmetry in CsEu(SO4)2. The chemical shift of the 5D0 energy level in cesium europium sulfate hydrate, with respect to cesium europium sulfate, is associated with the presence of H2O molecules in the vicinity of Eu3+ ion.

Complex sulfides BaDyCuS3, BaHoCuS3 and BaYbCuS3 were synthesized in a flow of sulfiding gases (CS2, H2S) at 900оC from standard solutions of lanthanide and copper nitrates, as well as from the same standard Ba(OH)2 solution. The crystal structures of BaDyCuS3, BaHoCuS3 and BaYbCuS3 were obtained by the Rietveld refinement method. All three compounds crystallize in the Cmcm space group (KZrCuS3 structural type) as predicted by the tolerance factor analysis. Their micromorphological, thermal and spectroscopic properties are evaluated. BaDyCuS3 and BaHoCuS3 melt congruently at 1376.5 °C and 1363.8 °C. BaYbCuS3 melts incongruently at 1353.3 °C. The optical band gap is 2.45 eV for BaDyCuS3, 2.37 eV for BaHoCuS3 and 1.82 eV for BaYbCuS3. The low bandgap of BaYbCuS3 is explained by the charge transfer band of Yb at the bottom of conduction band. The vibrational parameters of BaDyCuS3, BaHoCuS3 and BaYbCuS3 crystals were determined with the use of Raman and Infrared spectroscopies.

Europium doped Gd2O3 sphere-like nanoparticles with dm = 9.3 ± 3.5 nm were synthesized by cw CO2 laser vaporization technique in a flowing mixture of argon and oxygen. According to XRD data, the Eu:Gd2O3 nanoparticles crystallize in the monoclinic symmetry class (C2/m space group). High-resolution luminescence spectroscopy study showed that the ultra-narrow 5D0 → 7F0 transition of Eu3+ demonstrates only two peaks corresponding to two inequivalent Cs positions of Eu3+ ion in monoclinic Gd2O3 lattice that is explained by the peculiarities of local environment of Eu3+ ion at these sites. The hypersensitive transition 5D0 → 7F2 dominates in the spectrum and is expanded to the red part of the spectrum in comparison with cubic Eu:Gd2O3 due to intense transitions terminating at higher-lying components of the crystal-field-split 7F2 state. In the luminescence spectrum, an additional weak band with the maximum at 407 nm corresponding to the electronic transitions 4f65 d1(7FJ) → 4f7(8S7/2) of Eu2+ was detected. The obtained values of chromaticity coordinates and absolute quantum yield are (0.644; 0.325) and ca. 1%, respectively. The phase transformations have been investigated using differential scanning calorimetry and thermogravimetry (50–1400 °C). After annealing in air at 700 °C, the monoclinic symmetry class of the Eu:Gd2O3 nanoparticles is preserved and the particle size increases to dm = 17.8 ± 6.1 nm. After annealing, the chromaticity coordinates (0.659; 0.334) and absolute quantum yield (ca. 4%) can be obtained using red phosphor based on monoclinic Gd2O3:Eu3+. The lifetime of the excited 5D0 state of Eu3+ in the annealed nanoparticles is longer than that in the as-synthesized nanoparticles, due to the suppression of nonradiative decay after annealing.

This work investigates the Si/Fe flux ratio (2 and 0.34) influence on the growth of β-FeSi 2 polycrystalline thin films on Si(100) substrate at 630 °C. Lattice deformations for the films obtained are confirmed by X-ray diffraction analysis (XRD). The volume unit cell deviation from that of β-FeSi 2 single crystal are 1.99% and 1.1% for Si/Fe =2 and Si/Fe =0.34, respectively. Absorption measurements show that the indirect transition (~ 0.704 eV) of the Si/Fe =0.34 sample changes to the direct transition with a bandgap value of ~0.816 eV for the sample prepared at Si/Fe =2. The absorption spectrum of the Si/Fe =0.34 sample exhibits an additional peak located below the bandgap energy value with the absorption maximum of ~0.36 eV. Surface magneto-optic Kerr effect (SMOKE) measurements detect the ferromagnetic behavior of the β-FeSi 2 polycrystalline films grown at Si/Fe =0.34 at T=10 K, but no ferromagnetism was observed in the samples grown at Si/Fe =2. Theoretical calculations refute that the cell deformation can cause the emergence of magnetization and argue that the origin of the ferromagnetism, as well as the lower absorption peak, is β-FeSi 2 stoichiometry deviations. Raman spectroscopy measurements evidence that the film obtained at Si/Fe flux ratio equal to 0.34 has the better crystallinity than the Si/Fe =2 sample.

The employment of colloid quantum dots in a number of applications is limited by their instability under light irradiation. Additional methods of photostability enhancement of UV+visible-irradiated TGA-stabilized CdTe quantum dots are investigated. Photostability enhancement was observed via either addition of sodium sulphite in the role of chemical oxygen absorber or addition of 1% gelatin, or, finally, by additional stabilization by bovine serum albumine (BSA). The latter method is the most promising, since it not only enhances the quantum dots' photostability but also makes them more biocompatible and extends the possibilities of their biological applications.

New noncentrosymmetric rare earth borate Rb 3 NdB 6 O 12 is found in the ternary system Rb 2 O–Nd 2 O 3 –B 2 O 3 . The Rb 3 NdB 6 O 12 powder was fabricated by solid state synthesis at 1050 K for 72 h and the crystal structure was obtained by the Rietveld method. Rb 3 NdB 6 O 12 crystallized in space group R 32 with unit cell parameters a = 13.5236(4), c = 31.162(1) A, Z = 3. From DSC measurements, the reversible phase transition (I type) in Rb 3 NdB 6 O 12 is observed at 852–936 K. The 200 μm thick tablet is transparent over the spectral range of 0.3–6.5 μm and the band gap is found as E g ∼ 6.29 eV. Nonlinear optical response of Rb 3 NdB 6 O 12 tested via SHG is estimated to be higher than that of K 3 YB 6 O 12 . Blue shift of Nd luminescent lines is found in comparison with other borates. The vibrational parameters of Rb 3 NdB 6 O 12 are evaluated by experimental methods.

This study considered a process of quantum dots' self-assembly into nanostructure arrays with predefined geometry, which proceeds in the external resonant laser field. We considered the simplest case of assembling a stable structure of two particles. The problem was solved numerically using a three-dimensional model of Brownian dynamics. The idea of the method is that the attraction of the dots occurs due to the interaction of resonantly induced dipole moments, with the dots being then captured by the Van der Waals force. Finally, a three-dimensional model was considered; the average nanoparticle aggregation time as a function of the laser radiation wavelength was calculated; the probability of such structures' being formed was estimated for the calculated average aggregation time and for the laser pulse duration used in the experiment. The wavelength of the maximum probability was found to be shifted from the single particle resonance wavelength of 525 nm to the red area of 535 nm, which is in qualitative agreement with the redshift of the resonance wavelength of interacting particles.

Self-assembly remains one of the simplest and cheapest methods of nanostructuring. And the dependence of the properties of the objects obtained, not only on their composition, but also on the form, brings to the fore the question of developing methods for forming structures of a predetermined form and searching for system parameters in which the formation of a structure becomes possible. This paper is devoted to modeling the process of self-assembly of a multiparticle nanostructure of a predetermined shape in the field of laser radiation.Self-assembly remains one of the simplest and cheapest methods of nanostructuring. And the dependence of the properties of the objects obtained, not only on their composition, but also on the form, brings to the fore the question of developing methods for forming structures of a predetermined form and searching for system parameters in which the formation of a structure becomes possible. This paper is devoted to modeling the process of self-assembly of a multiparticle nanostructure of a predetermined shape in the field of laser radiation.

The crystal structure of the first-synthesized compound EuErCuS3 was determined from X-ray powder diffraction data: orthorhombic crystal system, space group Pnma, structural type Eu2CuS3: a = 10.1005(2) Å, b = 3.91255(4)Å, c = 12.8480(2) Å; V = 507.737(14) Å3, Z = 4, and ρx = 6.266 g/cm3. The temperatures and enthalpies of reversible polymorphic transitions and incongruent melting of the compound were determined by DSC: Tα↔β = 1524 K, ΔНα↔β = 2.3 ± 0.2 kJ∙mol−1; Tβ↔γ = 1575 K, ΔНβ↔γ = 0.7 ± 0.1 kJ∙mol−1; Tγ↔δ = 1602 K; ΔНγ↔δ = 1.3 ± 0.1 kJ∙mol−1 and Tcr = 1735 ± 10 K, ΔНcr = −3.5 ± 0.3 kJ∙mol−1. IR spectra were recorded in the range from 50 to 400 cm−1. The compound was found to be IR-transparent in the range 4000–400 cm−1. The compound was characterized by Raman spectroscopy. The observed spectra featured both Raman lines and luminescence. Ab initio calculations of the EuErCuS3 crystal structure and phonon spectrum were performed, the frequencies and types of fundamental modes were determined, and the involvement of constituent ions in the IR and Raman modes was assessed from an analysis of the ab initio displacement vectors. The vibrational spectra were interpreted. EuErCuS3 manifests a ferrimagnetic transition at 4.8 K. Its microhardness is 2850 MPa. The obtained data can serve as the basis for predicting the properties of EuLnCuS3 compounds. Valence states for Eu (2+) and Er (3+) are proved both by the XRD and optical methods. Optical band gap was found to be 1.934 eV from diffuse reflectance spectrum. © 2019 Elsevier B.V.

The crystal structures of the first-synthesized compound EuScCuS3 and previously known SrScCuS3 are refined by Rietveld analysis of X-ray powder diffraction data. The structures are found to belong to orthorhombic crystal system, space group Cmcm, structural type KZrCuS3, with a ​= ​3.83413(3) A, b ​= ​12.8625(1) A, c ​= ​9.72654(8) A (SrScCuS3) and a ​= ​3.83066(8) A, b ​= ​12.7721(3) A, c ​= ​9.7297(2) A (EuScCuS3). The temperatures and enthalpies of incongruent melting are the following: Тm ​= ​1524.5 К, ΔHm ​= ​21.6 ​kJ•mol−1 (SrScCuS3), and Тm ​= ​1531.6 К, ΔHm ​= ​26.1 ​kJ•mol−1 (EuScCuS3). Ab initio calculations of the crystal structure and phonon spectrum of the compounds were performed. The types and wavenumbers of fundamental modes were determined and the involvement of ions participating in the IR and Raman modes was assessed. The experimental IR and Raman spectra were interpreted. EuScCuS3 manifests a ferromagnetic transition at 6.4 ​K. The SrScCuS3 compound is diamagnetic. The optical band gaps were found to be 1.63 ​eV (EuScCuS3) and 2.24 ​eV (SrScCuS3) from the diffuse reflectance spectra. The latter value is in good agreement with that calculated by the DFT method. The narrower band gap of EuScCuS3 is explained by the presence of 4f-5d transition in Eu2+ ion that indicates a possibility to control the band gap of the chalcogenides by the inclusion of Eu. The activation energy of crystal structure defects, being the source of additional absorption in the NIR spectral range, was found to be 0.29 ​eV.

In order to synthesize single crystals of europium-silver double sulfate monohydrate, a hydrothermal reaction route was used. It was found that the crystallization cannot be performed under standard conditions. The compound AgEu(SO4)2·H2O crystallizes in the trigonal crystal system, space group P3221 (a ​= ​6.917(1), c ​= ​12.996(2) A, V ​= ​538.53(17) A3). The structure consists of triple-capped trigonal prisms [EuO9], in which one oxygen atom belongs to crystalline water, silver octahedra [AgO6], and sulfate tetrahedra [SO4]. The hydrogen bonds in the system additionally stabilize the structure. The electronic band structure wasstudied by density functional theory calculations which show that AgEu(SO4)2·H2O is an indirect band gap dielectric. Temperature dependent photoluminescence spectroscopy shows emission bands of transitions from the 5D0 state to the spin-orbit components of the 7FJmultiplet (J ​= ​0–6).The ultranarrow transition 5D0 - 7F0 shows a red shift with respect to other europium-containing water-free sulfates that is ascribed to the presence of OH group in the crystal structure in the close vicinity of the Eu3+ ion. An effect of abnormal sensitivity of the Ω4 intensity factor to minor distortions of the local environment is detected for the observed low local symmetry of C2.

NaSrLa 1−x (WO 4 ) 3 :Ho 3+ /Yb 3+ ternary tungstates were synthesized via microwave sol-gel route. Well-crystallized particles with particle sizes of 2–5 µm were obtained after heat-treatment at 900 °C for 16 h. Under the excitation at 980 nm, the particles showed yellow emissions based on the strong 545 and 655 nm emission bands. The preferable Yb 3+ :Ho 3+ ratio was obtained to be 9:1. Raman spectra of the doped particles indicated the presence of strong Ho 3+ luminescence lines. The pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated.

A possibility of creating a stable hybrid coating based on the hybrid of a reduced graphene oxide (rGO)/Ag quasi-periodic mesh (q-mesh) coating has been demonstrated. The main advantages of the suggested method are the low cost of the processes and the technology scalability. The Ag q-mesh coating is formed by means of the magnetron sputtering of silver on the original template obtained as a result of quasi-periodic cracking of a silica film. The protective rGO film is formed by low temperature reduction of a graphene oxide (GO) film, applied by the spray-deposition in the solution of NaBH4. The coatings have low sheet resistance (12.3 Ω/sq) and high optical transparency (82.2%). The hybrid coatings are characterized by high chemical stability, as well as they show high stability to deformation impacts. High performance of the hybrid coatings as electrodes in the sandwich-system «electrode–electrochromic composition–electrode» has been demonstrated. The hybrid electrodes allow the electrochromic sandwich to function without any visible degradation for a long time, while an unprotected mesh electrode does not allow performing even a single switching cycle.

Triple molybdate NaCaLa(1−x−y)(MoO4)3:xEr3+,yYb3+ (x = y = 0, x = 0.05 and y = 0.45, x = 0.1 and y = 0.2, x = 0.2 and y = 0) phosphors were successfully synthesized for the first time by the microwave sol–gel method. Well-crystallized particles formed after heat treatment at 900 °C for 16 h showed a fine and homogeneous morphology with particle sizes of 2–3 μm. The structures were refined by the Rietveld method in the space group I41/a. The optical properties were examined comparatively using photoluminescence emission and Raman spectroscopy. Under excitation at 980 nm, the NaCaLa0.7(MoO4)3:0.1Er3+,0.2Yb3+ and NaCaLa0.5(MoO4)3:0.05Er3+,0.45Yb3+ particles exhibited a strong 525 nm emission band, a weaker 550 nm emission band in the green region, and three weak 655 nm, 490 nm and 410 nm emission bands in the red, blue and violet regions. The pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated in detail.

Ternary sulfides BaPrCuS3 and BaSmCuS3 are first synthesized by the sulphidation reaction of a mixture of related oxides and metal Cu in a flow of (CS2, H2S) at 1170 K. The crystal structures of BaPrCuS3 and BaSmCuS3 are obtained by Rietveld method. BaPrCuS3 crystallizes in space group Pnma with unit cell parameters a = 10.56074(6), b = 4.11305(2) and c = 13.42845(7) A, V = 583.289 (5) A3, Z = 2 (structure type Eu2CuS3). BaSmCuS3 crystallizes in space group Cmcm with unit cell parameters a = 4.07269(4), b = 13.4499(1) and c = 10.3704(1) A, V = 568.06 (1) A3, Z = 2 (structure type KZrCuS3). The structural model is proposed for the Cmcm→Pnma transition in ABCX3 (X = S, Se) compounds for the sequence Sm-Pm-Nd-Pr. The dimensionless tolerance factor t = IR(A) × IR(C)/IR(B)2 is suggested to control the boundary between the Cmcm and Pnma structures. The micromorphological, thermal and spectroscopic properties are evaluated for BaPrCuS3. The compound melts incongruently at Tmelt = 1580.9 K. In BaPrCuS3, the band gap is estimated to be 2.1 eV. The vibrational parameters of BaPrCuS3 and BaSmCuS3 are comparatively observed by Raman spectroscopy.

The process of aggregation of two colloidal quantum dots in the field of quasiresonant laser radiation is investigated via computer simulation. The cases of either completely deterministic movement of particles or the movement with the account for random forces are considered. The conditions of pair formation are determined in dependence on initial interparticle distance, on laser wavelength, and on their initial orientation with respect to polarization plane of laser radiation. It is shown that despite velocity of thermal motion dominates over the velocity of directional diffusion of quantum dots, the account for random forces weakly influences on the probability of pair formation, the latter being close to results obtained in the deterministic case. The reason for this weak influence of Brownian movement is the resonant increase of electrodynamics attraction force during certain time interval within the laser pulse.

New ternary molybdate NaPbLa(1-x-y)(MoO4)3:xEr3+,yYb3+ (x = y = 0, x = 0.05 and y = 0.35, 0.4, 0.45 and 0.5) phosphors were successfully fabricated by the MSG (microwave sol-gel) method, and the microstructural and spectroscopic properties were characterized. The crystal structure of NaPbLa(MoO4)3 (NPLM) was defined by Rietveld analysis in space group I41/a with unit cell parameters a = 5.3735(2) and c = 11.8668(4) A, V = 342.65(3) A3, Z = 4 (RB = 6.64%). The unit cell volume of NaPbLa(MoO4)3 (NPLM) was intermediate between those of NaLa(MoO4)2 and PbMoO4. Under the 980 nm excitation, upconverted yellowish-green emissions at transitions from 2H11/2 and 4S3/2 were observed. No concentration quenching in the subsystem of donor ions at the content up to 50 at.% and no cross-relaxation losses in the subsystem of acceptor ions at the concentrations as high as 5 at. % were verified. The individual chromaticity points for the NaPbLa(MoO4)3:Er3+,Yb3+ phosphors, corresponding to the equal-energy point in the standard CIE diagram, revealed yellowish-green emissions.

Europium doped Y2O3spherical nanoparticles with the diameter ~10 nmobtained via cw laser vaporization are shown to crystallize in monoclinic symmetry class (C2/m space group). The size of nanoparticles established via HRTEM coincides with coherent scattering region established by XRD. Luminescence spectrum in the vicinity of ultranarrow transition demonstrates three peaks consistent with three inequivalent positions of Eu3+ ion in monoclinic Y2O3 lattice. Hypersensitive transition dominates in the spectrum, admitting the lack of inversion symmetry at Cs sites occupied by Eu3+. The spectrum of hypersensitive transition is expanded to the red part of spectrum due intense transitions terminating at higher-lying components of crystal-field-split 7F2 energy level. Obtaining chromaticity coordinates (0.669, 0.331)and absolute quantum yield (~21%) is possible using red phosphor based on monoclinic Y2O3:Eu3+.