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The temperature behaviour of 0.955 AgNbO3–0.045 LiTaO3 and AgNbO3 ceramics was studied in the range from 10 to 415 K.

We propose a simple hydrothermal synthesis of nanoflakes composed of alternating sulfide and hydroxide quasi-monolayers and their aqueous colloids, as a prospective family of novel multifunctional 2D materials.

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.

Bi4–xPrxTi3O12 (x = 0.4, 0.8, 1.2, 1.6) solid solutions have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1323 K. Their crystal structure has been determined using X-ray diffraction, and their luminescence spectra have been measured at room temperature. High-temperature heat capacity of polycrystalline substituted bismuth titanate samples has been determined by differential scanning calorimetry. The Cp(T) curves of the solid solutions with x = 0.4 and 0.8 have extrema related to phase transitions. Experimental data have been used to calculate the main thermodynamic functions of the solid solutions.

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.

Quantum size effects on interferons (electron-phonon bound states), confined in fractal silicon (Si) nanostructures (NSs), have been studied by using Raman spectromicroscopy. A paradoxical size dependence of Fano parameters, estimated from Raman spectra, has been observed as a consequence of longitudinal variation of nanocrystallite size along the Si wires leading to local variations in the dopants' density which actually starts governing the Fano coupling, thus liberating the interferons to exhibit the typical quantum size effect. These interferons are more dominated by the effective reduction in dopants' density rather than the quantum confinement effect. Detailed experimental and theoretical Raman line shape analyses have been performed to solve the paradox by establishing that the increasing size effect actually is accompanied by receding Fano coupling due to the weakened electronic continuum. The latter has been validated by observing a consequent variation in the Raman signal from dopants which was found to be consistent with the above conclusion.

Present work focuses on detailed temperature-dependent x-ray diffraction, Raman scattering, domain configuration and photoluminescence (PL) studies in the (Ba0·85Ca0.15) (Zr0·10Ti0.90)O3 (BCZT) ceramics. The comprehensive Raman spectroscopy analysis in the present work not only validates the presence of the intermediate orthorhombic phase in BCZT, but also provides evidence of another transition: rhombohedral R3c phase to R3m at low temperature. Temperature behaviour of the lowest frequency transverse optical mode (soft E (TO) phonon) and hard modes were studied. Temperature dependence of peak positions, intensities, and linewidths of Raman phonon modes signalled the presence of phase transitions near −50 ± 5 °C, 0±5 °C, 35±5 °C and 110 ± 10 °C. Evolution of domain morphology occurring with phase transitions above room temperature was studied by piezoresponse force microscopy technique. Analysis of PL spectra revealed disorder/heterogeneity in the sample and indicated the existence of self-trapped excitons. PL spectra is composed of four distinct colour components (∼2.55eV:blue, ∼2.32eV:green, ∼2.08eV:orange and ∼1.78eV:red).

Crystallization of heterovalent double (Mn,Ni)3BO5 and triple (Mn,Ni,Cu)3BO5 oxyborates with the ludwigite structure is studied in fluxes based on Bi2Mo3O12 diluted with Na2CO3 or Li2CO3 carbonates. Single crystals of five (Mn,Ni)3BO5 and three (Mn,Ni,Cu)3BO5 compounds with different cation ratios are obtained. The ion concentration is determined from the analysis of the lattice parameters by powder and single crystal XRD. The comparative analysis of the polarized Raman spectra of double and triple ludwigites is presented. The actual high nickel and small copper concentrations in the crystals are discussed. The hierarchy of chemical bonds in the fluxes used in addition to the approach involving stabilization of the manganese valence state using solvent components is estimated.

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.

In situ Raman spectroscopy is used to study the behavior of synthetic carbonate–aluminosilicate hydro-cancrinite Na6Ca2[(OH,CO3)2 Al6Si6O24]·2H2O compressed in an aqueous medium up to 1.6 GPa at 500°C. It is found that hydro-cancrinite retains its crystal structure up to 1.5 GPa and 300°C. It then amorphizes as the temperature rises, partially dissolves, and decomposes into two main products: nepheline and a scheelite-like compound.

In order to clarify ordering mechanisms of ferroic phase transitions in double fluoride salts (NH4)3SnF7, (NH4)3GeF7 and (NH4)3TiF7, their Raman scattering spectra have been studied in wide ranges ...

The temperature dependencies of position, width, and integral amplitude the E(TO) line near 307 cm−1 in Raman spectra in barium titanate powders with different non-hydrostatic pressure and temperature treatment were studied. It was found that parameters of the E(TO) line near 307 cm−1 are different in the crystal, the untreated powder, the powder treated by the non-hydrostatic pressure, and the powder annealed after the pressure treatment. The line width (FWHM) increase with temperature according to Klemens model. It indicates that the origin of the line broadening is the anharmonicity of the E(TO) phonons. The pressure treatment changes the anharmonicity of the phonon potential. It was found that the temperature dependence of the integral intensity of the E(TO) line is similar to that of the second optical harmonic signal and reflects the presence of the local polar regions. Thus, the E(TO) line in the Raman spectrum allows one to characterize the average polarity of local regions and their anharmonicity depending on non-hydrostatic pressures and thermal treatment.

We investigated both experimentally and numerically self-phase modulation-induced spectrum compression dynamics of negatively chirped picosecond Gaussian pulses in the low-loss dispersion-shifted telecom fiber near its zero dispersion wavelength (ZDW). It was experimentally observed linearly interpolated monotonous increase in spectrum compression ratio (SCR) with negative chirp growth of the incident pulse in the range from -5.9 to -91.9. According to numerical simulations, despite its small values in the vicinity of ZDW, fiber dispersion limits both SCR growth and spectrum compression quality expressed in terms of time-bandwidth product value and energy confinement ratio at larger chirp values (|C| > 100), in a combined action with self-phase modulation (SPM). Having optimized fiber length and pulse energy, we achieved record 49.2-fold spectrum compression of 38.3-ps, 2.08 nJ negatively chirped Gaussian pulses with compressed spectrum FWHM of 0.23 nm and ≈50% energy confinement at 1560 nm wavelength, leading to ≈13.3-times spectral brightness magnification. We believe that results obtained can be promising for ultra-short pulse laser systems development with enhanced spectral brightness.

The ion exchange sorption of the platinum(IV) chloride complexes in the presence of silver(I) chloro complexes from 2 and 4 M aqueous solutions of hydrochloric acid is studied on Purolite anion exchangers with different functional groups. The high selectivity of the investigated sorbents with respect to platinum during its recovery from individual hydrochloric acid solutions and in the presence of silver chloride complexes is determined. Since the latter are in this case virtually not sorbed in the presence of platinum(IV), they can be separated at the stage of sorption. The excellent kinetic properties of the investigated anion exchangers are revealed, allowing platinum to be eluted after its separation from silver chloro complexes in a dynamic mode.

The condensation of two soft modes has been found when studying the Raman spectra of the solid solution HoFe2.5Ga0.5(BO3)4 in the temperature range from 7 to 350 K. The first high-temperature soft ...

Single crystals of solid solutions of HoFe3–xGax(BO3)4 with x = 0, 0.5, 1, 1.5, and 3 were obtained using flux synthesis. The conditions of the synthesis are described in detail. The structural pro...

Experimental in situ observations of phase coexistence in switchable metal-organic frameworks are reported to provide a fundamental understanding of dynamic adsorbents that can change their pore structure in response to external stimuli. A prototypical flexible pillared layer framework DUT-8(Ni) (DUT = Dresden University of Technology) was studied under hydrostatic pressure by in situ Raman spectroscopy on single crystals. The closing transition of the open pore phase (op) containing DMF in the pores in silicon oil as a pressure transmitting fluid, as well as the closed pore phase (cp) to op transition under pressure in methanol, were studied. Phase coexistences during both transitions were observed.

We report on the novel heterometallic quaternary sulfides SrLnCuS3 (Ln = La, Nd, Tm), obtained as both single crystals and powdered samples. The structures of both the single crystal and powdered samples of SrLaCuS3 and SrNdCuS3 belong to the orthorhombic space group Pnma but are of different structural types, while both samples of SrTmCuS3 crystallize in the orthorhombic space group Cmcm with the structural type KZrCuS3. Three-dimensional crystal structures of SrLaCuS3 and SrNdCuS3 are formed from the (Sr/Ln)S7 capped trigonal prisms and CuS4 tetrahedra. In SrLaCuS3, alternating 2D layers are stacked, while the main backbone of the structure of SrNdCuS3 is a polymeric 3D framework [(Sr/Ln)S7]n, strengthened by 1D polymeric chains (CuS4)n with 1D channels, filled by the other Sr2+/Ln3+ cations, which, in turn, form 1D dimeric ribbons. A 3D crystal structure of SrTmCuS3 is constructed from the SrS6 trigonal prisms, TmS6 octahedra and CuS4 tetrahedra. The latter two polyhedra are packed together into 2D layers, which are separated by 1D chains (SrS6)n and 1D free channels. In both crystal structures of SrLaCuS3 obtained in this work, the crystallographic positions of strontium and lanthanum were partially mixed, while only in the structure of SrNdCuS3, solved from the powder X-ray diffraction data, were the crystallographic positions of strontium and neodymium partially mixed. Band gaps of SrLnCuS3 (Ln = La, Nd, Tm) were found to be 1.86, 1.94 and 2.57 eV, respectively. Both SrNdCuS3 and SrTmCuS3 were found to be paramagnetic at 20–300 K, with the experimental magnetic characteristics being in good agreement with the corresponding calculated parameters.

Two-dimensional phenomena are attracting enormous interest at present and the search for novel 2D materials is very challenging. We propose here the layered material valleriite composed of altering atomic sheets of Cu-Fe sulfide and Mg-based hydroxide synthesized via a simple hydrothermal pathway as particles of 50-200 nm in the lateral size and 10-20 nm thick. The solid products and aqueous colloids prepared with various precursor ratios were examined using XRD, TEM, EDS, X-ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), Raman, Mössbauer, UV-vis-NIR spectroscopies, magnetic, dynamic light scattering, zeta potential measurements. The material properties are largely determined by the narrow-gap (less than 0.5 eV) sulfide layers containing Cu+ and Fe3+ cations, monosulfide and minor polysulfide anions but are strongly affected by the hydroxide counterparts. Particularly, Fe distribution between sulfide (55-90%) and magnesium hydroxide layers is controlled through insertion of Al into the hydroxide part and by Cr and Co dopants entering both layers. Room-temperature Mössbauer signals of paramagnetic Fe3+ transformed to several Zeeman sextets with hyperfine magnetic fields up to 500 kOe in the sulfide layers at 4 K. Paramagnetic or more complicated characters were observed for valleriites with higher and lower Fe concentrations in hydroxide sheets, respectively. Valleriite colloids showed negative zeta potentials, suggesting negative electric charging of the hydroxide sheets, and optical absorption maxima between 500 nm and 700 nm, also depended on the Fe distribution. The last features observed also in the REELS spectra may be due to localized surface plasmon or, more likely, quasi-static dielectric resonance. The tunable composition, electronic, magnetic, optic and surface properties highlight valleriites as a rich platform for novel 2D composites promising for numerous applications.

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.

Here we present Raman spectroscopy approach to monitor the spatial distribution and the magnitude of the residual mechanical stresses in ceramic after non-hydrostatic pressure treatments. The residual pressure can be found from the E-phonon line shift (∼307 cm−1) in the Raman spectra. The relationship between the non-hydrostatic pressure (up to 11 GPa) and the shift of this line has been established. It is demonstrated that the change in the Raman line position (1332 cm−1) of the diamond anvil can be used for monitoring of applied non-hydrostatic pressures. A linear dependence of residual mechanical stresses on the applied pressures is found. Micro-Raman spectroscopy shows that the residual mechanical stresses are distributed fairly uniformly in the studied BaTiO3 samples at the micron scale. In the future, the proposed Raman technique can be used for monitoring the quality of produced BaTiO3 ceramics.

There are International and Russian guidelines for the diagnosis and treatment of medullary thyroid carcinoma. There is a recommendation to determine the basal level of calcitonin for all patients with nodular thyroid disease at the all of these documents. However, this test is not performed for this category of patients routinely even in large clinics for a number of reasons, the main one, which seems to be an economic issue. Six months ago a patient addressed to our clinic who underwent surgical treatment for a papillary carcinoma (follicular variant) of the thyroid gland in the volume of thyroidectomy with pre-tracheal lymphodissection and subsequent course of radioiodine therapy at the place of residence. A relapse of the disease was suspected on the control examination at the place of residence and the patient was sent for consultation to the polyclinic of the N.N. Blokhin National Medical Research Center of Oncology. In our clinic, diagnostic studies were carried out, including a revision of the finished cytological and histological preparations and a conclusion was obtained – medullary carcinoma of the thyroid. Determination of basal level of calcitonin in serum showed a value of 1292 pg/ml. The level of basal calcitonin significantly decreased after repeated surgical treatment. This case shows that in order to avoid such mistake, which is described in our clinical case, it seems necessary to follow the national recommendations, international standards to determine the level of basal calcitonin for all patients with thyroid nodal pathology who consulted and treated in medical institutions.

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.

The Raman spectra of an Rb2KLuF6 crystal are studied in the temperature range from 8 to 375 K, which includes two phase transitions: one of which proceeds from a cubic to a tetragonal phase, while the other transition takes place from a tetragonal to a monoclinic phase. An analysis of the temperature dependences of parameters of spectral lines shows that the former transition is of the second kind, while the latter transition is of the first kind, close to the tricritical point. It is shown that the structural phase transitions in the Rb2KLuF6 double perovskite are not associated with disordering. The former transition is associated with rotations of LuF6 octahedra around the fourth-order axis, while the latter transition is related with rotations of octahedra and displacements of rubidium ions.

Raman spectra of Hg2Br2 model improper ferroelastic crystals have been investigated in a wide range of high hydrostatic pressures. Baric dependences of the phonon frequencies have been obtained; of greatest interest are the observed soft mode originating from the slowest TA1 acoustic branch at the Brillouin zone boundary (X point) of the tetragonal phase and the anomalous behavior of this mode. In the ferroelastic phase spectra, the ignition of the second acoustic TA2 from the same point has also been detected and its baric behavior has been studied. Under sufficiently high pressures, splitting of doubly degenerate phonons with the Eg symmetry has been observed and explained. The parameters of the Gruneisen constants have been determined from the baric dependences of the phonon frequencies and discussed.

The Raman spectra of Rb2KLuF6 elpasolite crystal have been studied in a wide temperature range, including two phase transitions: from the cubic phase to the tetragonal phase and then to the monocli...

Switchable pillared layer metal–organic frameworks M2(2,6-ndc)2(dabco) (DUT-8(M), M = Ni, Co, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]octane, DUT – Dresden University of Technology) were synthesised in two different crystallite size regimes to produce particles up to 300 μm and smaller particles around 0.1 μm, respectively. The textural properties and adsorption-induced switchability of the materials, obtained from both syntheses, were studied by physisorption of N2 at 77 K, CO2 at 195 K and n-butane at 273 K, revealing pronounced differences in adsorption behavior for Ni and Co analogues. While the smaller nano-sized particles (50–200 nm) are rigid and show no gating transitions confirming the importance of crystallite size, the large particles show pronounced switchability with characteristic differences for the two metals resulting in distinct recognition effects for various gases and vapours. Adsorption of various vapours demonstrates consistently a higher energetic barrier for the “gate opening” of DUT-8(Co) in contrast to DUT-8(Ni), as the “gate opening” pressure for Co based material is shifted to a higher value for adsorption of dichloromethane at 298 K. Evaluation of crystallographic data, obtained from single crystal and powder X-ray diffraction analysis, showed distinct geometric differences in the paddle wheel units of the respective MOFs. These differences are further disclosed by solid-state UV-vis, FT-IR and Raman spectroscopy. Magnetic properties of DUT-8(Co) and DUT-8(Ni) were investigated, indicating a high-spin state for both materials at room temperature. Density functional theory (DFT) simulations confirmed distinct energetic differences for Ni and Co analogues with a higher energetic penalty for the structural “gate opening” transformation for DUT-8(Co) compared to DUT-8(Ni) explaining the different flexibility behaviour of these isomorphous MOFs.

We obtained Raman spectra of (NH4)3GeF7 crystals with a wide range of frequencies (10–3400 cm−1) and temperatures (8–300 K), including phase transition, which was accompanied by a symmetry increase with a temperature decrease. The internal vibrations of the GeF62− group were classified by the positional symmetry method. Considerable transformations of the Raman spectra were observed at the lower frequency range of lattice vibrations and the ranges of the internal vibrations of the ammonium ions. In contrast, the internal modes of the GeF62− groups changed only slightly due to their resonance splitting in the multiplied unit cell, which agreed well with the proposed phase transition mechanism induced by ammonium group ordering.

The pillared layer framework DUT-8(Zn) (Zn2(2,6-ndc)2(dabco), 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane, DUT = Dresden University of Technology) is a prototypical switchable MOF, showing characteristic adsorption and desorption induced open phase (op) to closed phase (cp) transformation associated with huge changes in cell volume. We demonstrate switchability strongly depends on a framework-specific critical particle size (dcrit). The solvent removal process (pore desolvation stress contracting the framework) significantly controls the cp/op ratio after desolvation and, subsequently, the adsorption induced switchability characteristics of the system. After desolvation, the dense cp phase of DUT-8(Zn) shows no adsorption-induced reopening and therefore is non-porous for N2 at 77 K and CO2 at 195 K. However, polar molecules with a higher adsorption enthalpy, such as the polar molecules such as chloromethane at 249 K and dichloromethane (DCM) at 298 K can reopen the macro-sized crystals upon adsorption. For macro-sized particles, the outer surface energy is negligible and only the type of metal (Zn, Co, Ni) controls the DCM-induced gate opening pressure. The framework stiffness increases from Zn to Ni as confirmed by DFT calculations, X-ray crystal structural analyses, and low frequency Raman spectroscopy. The partial disintegration of the Zn based node hinges produces an overall increased stabilization of cp vs. op phase shifts the critical particle size at which switchability starts to become suppressed to even lower values (dcrit < 200 nm) as compared to the Ni-based system (dcrit ≈ 500 nm). Hence, the three factors affecting switchability (energetics of the empty host, (Eop-Ecp) (I), particle size (II), and desolvation stress (III)) appear to be of the same order of magnitude and should be considered collectively, not individually.

Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature changes were minimal, which required a significant improvement in the resolution and stability of Raman measurements. The anomalies in the behaviour of the spectra at about 178 K, 235 K, 255 K, 278 K, 296 K, 398 and 412 K were observed. The structural phase transition at 398 K is irreversible. This transition is associated with the release of water molecules from nanochannels. The irreversible phase transition has a temperature range of about 10 K. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. Russian Foundation for Basic Research, RFBR: 18-02-00754 Fundação para a Ciência e a Tecnologia, FCT: CENTRO-01-0145-FEDER-031679 Türkiye Bilimsel ve Teknolojik AraÅ tirma Kurumu, Tà BITAK: UIDB/50011/2020, 115F227, UIDP/50011/2020 Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN Fundação para a Ciência e a Tecnologia, FCT Funding: This research was funded by the Russian Foundation for Basic Research grant number 18-02-00754, F.S. thanks Scientific and Technological Research Council of Turkey for support under Grant Number 115F227. S.Kopyl and A.Kholkin thank the joint project Portugal-Turkey TUBITAK/0006/2014. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC. S.Kopyl, P.Z. and A.Kholkin were partly supported by FCT (Portugal) through the project “BioPiezo”-PTDC/CTM–CTM/31679/2017 (CENTRO-01-0145-FEDER-031679). Part of this work was funded by national funds (OE), through FCT—Fundação para a Ciência e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 July.

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.

A bias-dependent in situ Raman scattering and UV–Vis absorption spectroscopic change has been correlated with the corresponding color change of an electrochromic device in an attempt to explain how to understand the relationship between actual perceived color and its absorption/transmittance spectra. For this, the bias across an electrochromic device was increased gradually, rather than abruptly turning ON and OFF, to see subtle variations in Raman and absorption spectra due to bias. Raman scattering establishes that viologen changes its oxidation state reversibly between two redox species (EV2+ to EV+•) as a result of bias-induced dynamic redox process. A gradual variation in Raman and absorption spectra, which shows maximum absorption corresponding to the yellow light, accompanies similar variation in color change of the device as visible by naked eye. These spectroscopic results are correlated with the perceived blue color, in the reflected light, by the eye to understand the actual reason behind this. Maximum absorption of yellow light by the device resulting in blue appearance has been explained using the concept of additive and subtractive primary colors.

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.

Thin films have been produced via a spray method from commercially available single-walled carbon nanotubes (SWCNTs). A SWCNT film thickness has ranged from ~10 to ~80 nm. The SWCNT diameter has accepted values of 1.6–1.8 nm. The existence of SWCNTs longer than 10 μm is established. The optimal thickness of a SWCNT thin film is found to be ~15 nm at which the transmittance exceeds 85%. The specific resistance of SWCNT thin films goes from ~1.5 × 10–3 to ~3 × 10–3 Ohm cm at room temperature. The pioneering study of the temperature dependences of the Seebeck coefficient and surface resistance is performed for this type of SWCNT. A surface resistance is found to increase with rising temperature. Furthermore, the Seebeck coefficient of SWCNT thin films weakly depends on temperature. Its value for all samples is evaluated to be ~40 μV/K. According to the sign of the Seebeck coefficient, thin films exhibit hole-type conductivity. Moreover, the power factor of a 15-nm thin SWCNT-film decreases with a temperature increase to 140◦C from the value of approximately ~120 to ~60 μW m–1 K–2. A further rise in temperature has led to a gain in the power factor.

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 ...

The sorptive extraction of palladium(II) chloride complexes in the presence of silver(I) chloride complexes from 2 and 4 M aqueous solutions of HCl with a series of Purolite anionites with different functional groups is studied. An anion exchange mechanism of sorption is identified from Raman spectroscopy data. Kinetic properties that are inherent to the investigated ionites and allow the elution of palladium(II) and silver(I) after their extraction in a dynamic mode are revealed.

The structural phase transitions in diphenylalanine microtubes caused by an increase in the non-hydrostatic pressure have been examined. Raman scattering investigations have been carried out and the results obtained have been interpreted and analyzed. Spectral variations in the ranges of phenyl ring vibrations and high-frequency oscillations of NH and CH groups have been analyzed. Under pressures of up to 9.8 GPa, four spectral anomalies indicative of the occurrence of phase transitions have been observed. The transitions under pressures of 1.7 and 4 GPa are shown to be reversible. The transition at 5.7 GPa is accompanied by partial sample amorphization.