Tetragonal Crystals Research Articles

Symmetry-enforced band crossings in tetragonal materials: Dirac and Weyl degeneracies on points, lines, and planes

We study the occurrence of symmetry-enforced topological band crossings in tetragonal crystals with strong spin-orbit coupling. By computing the momentum dependence of the symmetry eigenvalues and the global band topology in the entire Brillouin zone, we determine all symmetry-enforced band crossings in tetragonal space groups. In particular, we classify all Dirac and Weyl degeneracies on points, lines, and planes, and find a rich variety of topological degeneracies. This includes, among others, double Weyl points, fourfold-double Weyl points, fourfold-quadruple Weyl points, Weyl and Dirac nodal lines, as well as topological nodal planes. For the space groups with symmetry-enforced Weyl points, we determine the minimal number of Weyl points for a given band pair and, remarkably, find that materials in space groups 119 and 120 can have band pairs with only two Weyl points in the entire Brillouin zone. This simplifies the topological responses, which would be useful for device applications. Using the classification of symmetry-enforced band crossings, we perform an extensive database search for candidate materials with tetragonal space groups. Notably, we find that Ba$_5$In$_4$Bi$_5$ and NaSn$_5$ exhibit twofold and fourfold Weyl nodal lines, respectively, which cross the Fermi energy. Hf$_3$Sb and Cs$_2$Tl$_3$ have band pairs with few number of Weyl points near the Fermi energy. Furthermore, we show that Ba$_3$Sn$_2$ has Weyl points with an accordion dispersion and topological nodal planes, while AuBr and Tl$_4$PbSe$_3$ possess Dirac points with hourglass dispersions. For each of these candidate materials we present the ab-initio band structures and discuss possible experimental signatures of the nontrivial band topology.

Comparative evaluations of bulk seeded protein crystallization in batch versus continuous slug flow crystallizers

The present work evaluated for the first time the use of continuous slug flow crystallizer (CSFC) in bulk seeded protein crystallization, using lysozyme (LYZ) as the model protein. LYZ crystals pre-prepared in batch crystallizer were used as seeds. The crystallization was performed at supersaturation level below the metastable-zone-limit. The resultant crystal size distribution (CSD), CSD’s reproducibility, LYZ’s bioactivity, and crystallization efficiency as characterized by the space-time-yield (STY, mg/h·L) were determined. The results showed that the CSFC’s performance was governed by the flowrate, where a trade-off existed between crystal quality and crystallization efficiency upon varying the flowrate. At low flowrates, which reduced the shear rate and prolonged the residence time, well-defined large tetragonal crystals were produced attributed to suppressed secondary nucleation and extended crystal growth, but low STY due to difficulty in transporting the seeds/products crystals. Higher flow rates led to higher STY, but increased production of small non-tetragonal crystals that formed agglomerates. Compared to batch crystallizer, the CSFC produced LYZ crystals of similar average size, morphology, and bioactivity, but with roughly 50% lower STY, as the batch’s high-shear environment promoted secondary nucleation, hence higher crystallization rate. The CSD’s width and reproducibility was nevertheless significantly improved in CSFC.

COMPUTATION OF BOUNDS ELASTIC PROPERTIES OF POLYCRYSTALS BASED ON FAST FOURIER TRANSFORM METHOD

The present paper derives numerical bounds of the elastic properties of polycrystals. The homogenized elastic coefficients are computed from Voronoi-type unit cells. The main result of the article detemines the upper and lower bounds for a case of polycrystals made up of cubic single crystals by using the fast Fourier transform method (FFT) based on the shape function. Our method guarantees the exact solutions in comparison to the Moulinec and Suquet’s method within some uncontrolled approximations. The proposed method could be extended to account for other material symmetries such as hexagonal or tetragonal crystals.

Structures of two novel crystal forms of Aspergillus oryzae alpha amylase (taka-amylase)

The structures of Aspergillus oryzae α-amylase were determined in a tetragonal crystal, having one molecule as asymmetric unit, and a monoclinic crystal with two molecules as asymmetric unit. Both crystal forms were obtained from trace contaminants of an old commercial lipase preparation. Structures were determined and refined to 1.65Å and 1.43Å resolution respectively. The latter crystal has a non-crystallographic (NCS) twofold axis within the asymmetric unit. Glycosylation at Asn197 is evident, and in the tetragonal crystal can be seen to include three, partially disordered sugar residues following the initial N-acetyl glucosamine (NAG). Superposition of the tetragonal crystal model on the α-amylases from Bacillus subtilis (PDB:1BAG), pig pancreas (PDB:3L2L), and barley (PDB:1AMY), show a high degree of coincidence, particularly for the (β/α)8-barrel domains, and especially within the active site. Using this structural agreement between amylases, we extrapolated the binding model of a six residue, limit dextrin found in pig pancreas α-amylase to the A.oryzae enzyme model, which predicts substrate interacting amino acid residues.

Crystal structures of β-1,4-N-acetylglucosaminyltransferase 2: structural basis for inherited muscular dystrophies.

The canonical O-mannosylation pathway in humans is essential for the functional glycosylation of α-dystroglycan. Disruption of this post-translational modification pathway leads to congenital muscular dystrophies. The first committed step in the construction of a functional matriglycan structure involves the post-translational modification of α-dystroglycan. This is essential for binding extracellular matrix proteins and arenaviruses, and is catalyzed by β-1,4-N-acetylglucosaminyltransferase 2 (POMGNT2). While another glycosyl transferase, β-1,4-N-acetylglucosaminyltransferase 1 (POMGNT1), has been shown to be promiscuous in extending O-mannosylated sites, POMGNT2 has been shown to display significant primary amino-acid selectivity near the site of O-mannosylation. Moreover, several single point mutations in POMGNT2 have been identified in patients with assorted dystroglycanopathies such as Walker-Warburg syndrome and limb girdle muscular dystrophy. To gain insight into POMGNT2 function in humans, the enzyme was expressed as a soluble, secreted fusion protein by transient infection of HEK293 suspension cultures. Here, crystal structures of POMGNT2 (amino-acid residues 25-580) with and without UDP bound are reported. Consistent with a novel fold and a unique domain organization, no molecular-replacement model was available and phases were obtained through crystallization of a selenomethionine variant of the enzyme in the same space group. Tetragonal (space group P4212; unit-cell parameters a=b=129.8, c=81.6 Å, α = γ = β = 90°) crystals with UDP bound diffracted to 1.98 Å resolution and contained a single monomer in the asymmetric unit. Orthorhombic (space group P212121; unit-cell parameters a = 142.3, b=153.9, c=187.4 Å, α = γ = β = 90°) crystals were also obtained; they diffracted to 2.57 Å resolution and contained four monomers with differential glycosylation patterns and conformations. These structures provide the first rational basis for an explanation of the loss-of-function mutations and offer significant insights into the mechanics of this important human enzyme.

Pharmacognostic Investigation of Leaves and Bark of Cochlospermum Religiosum Linn

Cochlospermum religiosum (Linn.) Alston. (Bixaceae) otherwise known as Yellow silk cotton tree.Traditionally, the plant is used in the treatment of cough, asthma, jaundice, tuberculosis, inflammation, gonorrhea, fever and dysentery. In the present studymicromorphological investigations and the physicochemical analysis of Cochlospermum religiosumleaves and stem bark were carried out.The macromorphological examination indicated simple, palmately lobed, alternate distichous leaves possessing the prominent parallel venation, acute apices and crenate margin. Similarly, smooth, fibrous, ash coloured bark containing an orange-coloured gummy exudate observed. The microscopy of leaves presented a dorsiventral lamina, long filamentous unicellular uniseriate covering trichomes, anomocytic stomata, annulated lignified xylem vessel, mucilaginous brown matter, starch grains and prisms of calcium oxalate whereas the microscopic examination of the bark indicated lignified cork cells, thick-walled lignified sclereids, bundles of lignified fibres, rounded starch grains, elongated cellulosic medullary rays, tetragonal and rosette crystals of calcium oxalate. Thequalitative analysis of inorganic elementsexhibited the presence of aluminium, sodium, calcium, chlorides and ironin leaves and the bark ofCochlospermum religiosum.The present investigation on pharmacognostic characters and analytical standards of Cochlospermum religiosumwill provide a diagnostic tool in the authentication and the assessment of its quality.

Free-standing ultra-thin Janus indium oxysulfide for ultrasensitive visible-light-driven optoelectronic chemical sensing

Atomically-thin Janus heterojunctions exhibit extraordinary electronic and optoelectronic properties, mainly due to their intrinsic built-in electric field. However, current investigations are limited within layered metal chalcogenides. Here, a free-standing ultra-thin Janus metal oxychalcogenide is realized from non-layered In 2 S 3 . In the presence of strong mechanical agitation in the liquid medium, the original tetragonal crystal is cleaved. Ambient oxygen atoms are subsequently diffused and incorporated into limited part of the crystal structure, forming the oxysulfide phase with the gradual transition into a hexagonal structure. While the integrity of the covalent bonding system is maintained, a tensile strain is generated as a result of the crystal coordination mismatching between the pure sulfide and oxysulfide phases, leading to a more than two orders enhancement on visible-light-driven exciton lifetime compared to that of pure In 2 S 3 . Such an impressive excitonic interaction provides the fundamentals to establish an ultra-sensitive and power-saving optoelectronic chemical sensing platform. As an example, dipoles generated by the surface adsorbed NO 2 molecules cause significant re-distribution of photoinduced charges in the anisotropic non-layered Janus structure under visible light low-power excitation, resulting in a superior sub-ppb detection limit of NO 2 gas at room temperature. • Free-standing Janus indium oxysulfide is formed from In 2 S 3 with oxygen incorporation. • Surface crystal transfer is due to the replacement of sulfur by diffused oxygen. • Deteriorated exciton binding energy and recombination rate; prolonged PL lifetime. • Visible-light-driven gas sensor is ultrasensitive to NO 2 gas at room temperature. • The limit of detection (LOD) is in parts-per-trillion (ppt) range.

Coherent crystal branches: the impact of tetragonal symmetry on the 2D confined polymer nanostructure.

The symmetry of polymer crystals greatly affects the optical, thermal con-ductivity and mechanical properties of the materials. Past studies have shown that the two-dimensional (2D) confined crystallization of polymer nanorods could produce anisotropic structures. However, few researchers have focused on understanding confined nanostructures from the perspective of crystal sym-metry. In this research, we demonstrate the molecular chain self-assembly of tetragonal crystals under cylindrical confinement. We specifically selected poly(4-methyl-1-pentene) (P4MP1) with a 41 or 72 helical conformation (usually crystallizing with a tetragonal lattice) as the model polymer. We found a coherent crystal branching of the tetragonal crystal in the P4MP1 nanorods. The unusual 45°- and 135°-{200} diffractions and the meridional 220 diffraction (from 45°-tilted crystals) have shown a uniform crystal branching between the a 1-axis crystals and the 45°-tilted crystals in the rod long axis, which originates from a structural defect associated with tetragonal symmetry. Surprisingly, this chain packing defect in the tetragonal cell can be controlled to develop along the rod long axis in 2D confinement.

Anisotropic Terahertz Microscopy of Lysozyme in Different Crystal Lattice Systems

Long-range vibrational modes of proteins at terahertz (THz) frequencies have been associated with protein function and allosteric control. The characterization of these motions has been challenging due to energy overlap with water absorption and a large vibrational density of states. Recently it has been demonstrated both experimentally and theoretically that vibrational bands can be isolated using stationary sample anisotropic terahertz microscopy (SSTAM) for oriented samples, typically realized using protein crystals [1, 2]. In those early measurements, inhibitor binding contrast was demonstrated for high symmetry tetragonal crystals. While high symmetry crystals are ideal for structural determinations, they can limit the types of vibrations observable in the ATM measurements. Here we show a survey of ATM measurements of triclinic, monoclinic and tetragonal crystals, demonstrating the unique signatures observable for the different symmetry groups, leading to a more complete determination of the vibrational hot spots that may contribute to enzymatic efficiency. The SSATM spectra indicate the presence of conserved vibrational modes near 40cm−1 and 55cm−1 for CEWL in triclinic, monoclinic and tetragonal lattice systems respectively. For CEWL in the monoclinic lattice system, a prominent band at 20cm−1 was consistently observed in the SSATM spectra but not in the triclinic or tetragonal systems. The conserved bands may represent vibrational modes that are unperturbed by crystal contact forces while the differences may be related to unique molecular orientation in different crystal systems. 1.Niessen, K., Y. Deng, and A.G. Markelz, Near-field THz micropolarimetry. Opt Express, 2019. 27(20): p. 28036-28047.2.Romo, T.D., A. Grossfield, and A.G. Markelz Persistent Protein Motions in a Rugged Energy Landscape Revealed by Normal Mode Ensemble Analysis. Accepted Journal of Chemical Information and Modeling, 2020. https://doi.org/10.26434/chemrxiv.12885203.v1.

Identification of grown-in dislocations in protein crystals by digital X-ray topography

X-ray topography is a useful and nondestructive method for direct observation of crystal defects in nearly perfect single crystals. The grown-in dislocations from the cross-linked seed crystal in tetragonal hen egg-white lysozyme crystals were successfully characterized by digital X-ray topography. Digital X-ray topographs with various reflections were easily obtained by reconstruction of sequential rocking-curve images. The Burgers vector of the dislocation is different from those reported previously. Interestingly, one of the dislocations had a bent shape. The preferred direction of the dislocation line was analysed by the estimated dislocation energy based on the dislocation theory. The dislocation energy can be estimated by the dislocation theory even in protein crystals composed of macromolecules.

Hydrothermal synthesis of star-shaped Bi5O7Br catalysts with strong visible light catalytic performance

Micron star-shaped Bi5O7Br catalysts were synthesized, with Bi(NO3)3·5H2O and cetyltrimethylammonium bromide (CTAB) as raw materials, by using a simple hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and UV–visible diffuse reflectance spectroscopy (UV–vis DRS) were used to characterize the samples. It was found that tetragonal star-shaped Bi5O7Br crystals with high crystallinity could be obtained as pH value of the solution was about 9. Compared with flaky BiOBr particles, the star-shaped Bi5O7Br sample displayed red-shift in the UV–visible absorption edge, whereas the band gap was reduced to 2.57 eV and the specific surface area was increased. Among all samples, the star-shaped Bi5O7Br had the highest photocatalytic efficiency. After visible light irradiation for 10 min, the degradation rate of the rhodamine B (RhB) solution with a concentration of 10 mg·L−1 was almost 100%. Also, its photocatalytic activity was nearly unchanged after five cycles. It is believed that such Bi5O7Br could be used as stable and effective visible light catalysts.

Microstructural and elastic properties of stable aluminium-rich TiAl and TiAl2 formed phase Intermetallics

We studied aluminium-rich Ti-Al (Ti32Al68 and Ti40Al60) binary alloys that were composed of TiAl and TiAl2 lamellar microstructures. The law of mixtures was employed in calculating the theoretical Young’s moduli. The lattice parameters of the alloys showed that both were tetragonal crystals. In the computational study, we made use of our modified method for the stress–strain calculation of elastic constants. The alloys at the respective chemical compositions were modelled by creating titanium (Ti) supercells, which were then doped by replacing some of the Ti atoms with aluminium atoms. The values of elastic moduli were verified by the ab initio calculation in this work, which showed a perfect agreement. The Pugh’s ratio showed that both the alloys are ductile.

Influence of alumina addition on structural and catalytic properties of sulphated zirconia in isomerization of n-hexane

New binary catalytic systems based on sulphated zirconia-alumina were synthesized by controlled hydrolysis of alkoxides using relative molar ratios of constituents 1:1, 1:2 and 1:3 in favour of zirconia. The obtained differences in the final catalytic material?s properties may be related to organic precursor memory effect, the applied calcinations temperatures and used alumina contents. The addition of alumina to zirconia affected the structural and surface properties stabilizing bare zirconia by means of slower phase transformation of tetragonal zirconia crystal phase into monoclinic one, further resulting in smaller crystallites sizes and higher surface density of acidic function (sulphates). The best alumina impact on physico-chemical properties was achieved when the highest amount of alumina (e.g. 50%) and lower calcination temperature (500?C) were used, causing relatively high steady-state activity in isomerization of n-hexane at reaction temperature 250 ?C. On the other hand, higher calcination temperature (600 ?C) played a role in the genesis of greater sulphate density. Catalytic activity and selectivity are expressed as a complex synergistic function of relative density of acid sites together with positive status of other optimized physico-chemical properties of the catalytic material (by activation and calcination temperatures).

Effect of molarity on Structural, Morphological, optical and the photocatalytic property of (Cu1-X-Cox)-TiO2 nanoparticles synthesized via hydrothermal method

Copper and cobalt co-doped TiO2 nanoparticles (NPs) [(Cu1-x-Cox)-TiO2 for x = 0.1 M and 0.9 M] have been synthesized through the hydrothermal method in the current investigation. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and UV–vis spectrophotometer have characterized the structural, optical, morphological, and compositional of all prepared samples. Analysis of XRD showed that all prepared nano powders were nanocrystalline and had new [(Cu1-x-Cox)- TiO2 ], rutile and anatase phase depending on the molarity. Further studies have shown that the arrangement of tetragonal and rhombohedral crystals for TiO2 and (Cu1-x-Cox)- TiO2 for x = 0.1 M and 0.9 M respectively, with an average crystallite size of 7.362 nm for TiO2 and 27 nm for (Cu1-x-Cox)- TiO2 for x = 0.1 M and 0.9 M . The SEM analysis shows that the NPs for pure is spherical in form and doped TiO2 have an irregular shape with an average grain size of 168 nm and 223 nm. Analysis of the EDS confirms the chemical composition of the Ti and O elements of the NPs. The difference in the indirect band gap of 3.07 eV, 2.74 eV and 3.58 eV for TiO2 NPs, (Cu0.9-Co0.1)-TiO2 NPs and (Cu0.1-Co0.9)-TiO2 NPs is shown by Tauc’s plots. Here it is noted that the maximal absorption (λm) showed a red shift in the UV–vis absorption spectrum due to doping. Photocatalytic activity was assessed by monitoring Eriochrome Black T (EBT) degradation under UV light. The EBT dye photocatalytic degradation results were 57.75%, 73.7% and 73 %for TiO2 NPs, (Cu0.9-Co0.1)-TiO2 NPs and (Cu0.1-Co0.9)-TiO2 NPs for 110 min, respectively, under UV irradiation. These findings indicate that doping with copper and cobalt improves TiO2’s photodegradation quality.

The crystallization enthalpy and entropy of protein solutions: microcalorimetry, van't Hoff determination and linearized Poisson-Boltzmann model of tetragonal lysozyme crystals.

During a first-order phase transition, a thermodynamic system releases or absorbs latent heat. Despite their fundamental importance, the heat or enthalpy change occurring during protein crystallization has been directly measured only in a few cases, and the associated entropy change can only be determined indirectly. This work provides an experimental determination and theoretical analysis of the dependence of the molar crystallization enthalpy of lysozyme solutions, ΔHxtal, on the physicochemical solution parameters. Its value is determined directly by isothermal microcalorimetry and indirectly by a van't Hoff analysis of solubility data, which quantitatively agree. This suggests a two-state crystallization process, in which oligomeric intermediates play a minor role. ΔHxtal is found to be negative on the order of few tens of the thermal energy per molecule. It is independent of protein concentration and stirring speed, but weakly depends on salt (NaCl) concentration and solution pH. Assuming that crystals are electrostatically neutral, these trends are explained by a linearized Poisson-Boltzmann theory. In addition, the molar crystallization entropy, ΔSxtal, is analyzed. The dependence of the van't Hoff entropy on salt concentration and pH is captured by the model, complementing the analysis of crystallization thermodynamics.

Broad bandwidth emission and in situ electric field modulation of photoluminescence in Nd-doped ferroelectric crystals.

The electric field modulation of photoluminescence in ferroelectric-optical materials as a novel in situ, non-damaging and real-time controllable method has drawn much research focus. The broad bandwidth emission of 33 nm and a tuneable luminescence contrast of 28% were achieved in Nd-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Nd:PMNT) tetragonal ferroelectric-optical crystals arising from spontaneous polarization. The study of Nd:PMNT ferroelectric crystals under a cyclic, triangular alternating current voltage wave showed that the change in the photoluminescence intensity subjected to an electric field is mainly related to the 180° domain distribution, rather than the 90° domain. The physical process of electric field tuning luminescence is to control the 180° domain distribution using the external electric field, which thereby effectively tunes the luminescence. This finding restricts the limitation of a specific phase change region, which greatly increases the range of materials used and has guiding significance for research in the electric field modulation of luminescent technology.

The effect of lanthanum (La3+) addition on the fabrication of Ba0.90La0.10TiO3 and Ba0.85La0.15TiO3

• The addition of La 3+ caused crystallite size and grain size to decrease from BaTiO. • The addition of La 3+ on BaTiO 3 can decrease band gap energy. • Ba 1-x La x TiO 3 had response to the light and the photovoltaic effect The fabrication of Barium Titanate with the Lanthanum addition (Ba 1-x La x TiO 3 ) were prepared by using Chemical Solution Deposition (CSD) method. The addition of La 3+ were 10% and 15% on 0.5 M solubility. Spin coater was used in deposition process of thin films with speed 4000 rpm for 30 s. The sandwich-structured of Ba 1-x La x TiO 3 thin films were grown on a quartz substrate. Thin films were annealed at 850 °C with holding time of 1,5 h. X-Ray Diffraction (XRD) analysis showed the formation of tetragonal crystal (ICDD data base PDF # 831880). The addition of La 3+ caused crystallite size to decrease from BaTiO 3 . The crystallite size of BaTiO 3, Ba 0.90 La 0.10 TiO 3 and Ba 0.85 La 0.15 TiO 3 were 24 nm; 19 nm; 13 nm respectively. It is proportional to diffraction intensity values. The morphology of thin film was obtained from Scanning Electron Microscopy (SEM) characterization. The average of film thickness was 404 nm. The result of UV–Vis characterization showed that the addition of La 3+ increased the transmittance values at absorption edge area. The optical band gap was calculated and the values found for BaTiO 3, Ba 0.90 La 0.10 TiO 3 and Ba 0.85 La 0.15 TiO 3 were about 3.3 eV; 3.125 eV; and 3.125 eV respectively. Therefore, it could be concluded that the addition of La 3+ on BaTiO 3 can decrease band gap energy. The result of I-V characterization showed that Ba 1-x La x TiO 3 thin films had a response to the light and the photovoltaic effect under illumination 1000 W/m 2 .

Synthesis and properties of Sm<sup>3+</sup> doped NaLa(WO<sub>4</sub>)<sub>2</sub> single matrix white phosphors

<sec>Single ion doped single phase white emitting phosphors have some special advantages and great potential applications in the field of high quality LED lighting. This type of phosphors can effectively solve the problem of uneven particle dispersion and sedimentation in the white light scheme obtained by UV chip plus trichromatic phosphor, and solve the problems of the luminescence and reabsorption between phosphors and the regulation of trichromatic ratio. A comparison of the single-ion doping luminescent material with the multi-ion doping system shows that the single-ion doping luminescent material is simpler in both preparation process and luminescence color adjustment, which can achieve higher color rendering index, more easily controlled color temperature and closer to the color coordinates of white light. </sec><sec>According to the principle of colorimetry and luminescence, light of two or more wavelengths may be combined to obtain white light emission. Under the UV excitation, the Sm<sup>3+</sup> ions emit relatively strong green, yellow, orange and red light at 580–670 nm. Under UV excitation, the broadband spectrum of <inline-formula><tex-math id="Z-20210831172528">\begin{document}${\rm{WO}}_{4}^{2-} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210493_Z-20210831172528.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210493_Z-20210831172528.png"/></alternatives></inline-formula> self-activated emission covers almost the whole visible region, but the blue-green light is strong in the short wavelength region and the yellow-orange-red light is weak in the long wavelength region. When Sm<sup>3+</sup> ions are doped into tungstate, Sm<sup>3+</sup> ions’ luminescence can effectively supplement the weak luminescence intensity of tungstate in the long-wave region, and white light can be obtained. Under the excitation of 250 nm, the phosphor emits cold white light, and warm white light under the excitation of 403 nm. The experimental results show that Sm<sup>3+</sup> ions have a significant effect on the correlated color temperature adjustment of self-activated luminescence of NLW phosphors. All the prepared samples are crystallized into the tetragonal crystal phase structures and that their morphologies present rhombic sheet. By analyzing the experimental data, the type of energy transfer between Sm<sup>3+</sup> ions is determined to be electrical dipole–electrical dipole interaction. The NLW: <i>x</i>Sm<sup>3+</sup> phosphor has high stability and can be effectively excited by ultraviolet/near-ultraviolet light, which can be used as a potential candidate of single matrix single-ion doped white phosphors.</sec>

SDS-Stabilized CuInSe2/ZnS Multinanocomposites Prepared by Mechanochemical Synthesis for Advanced Biomedical Application.

The CuInSe2/ZnS multiparticulate nanocomposites were first synthesized employing two-step mechanochemical synthesis. In the first step, tetragonal CuInSe2 crystals prepared from copper, indium and selenium precursors were co-milled with zinc acetate dihydrate and sodium sulfide nonahydrate as precursors for ZnS in different molar ratios by mechanochemical route in a planetary mill. In the second step, the prepared CuInSe2/ZnS nanocrystals were further milled in a circulation mill in sodium dodecyl sulphate (SDS) solution (0.5 wt.%) to stabilize the synthesized nanoparticles. The sodium dodecyl sulphate capped CuInSe2/ZnS 5:0-SDS nanosuspension was shown to be stable for 20 weeks, whereas the CuInSe2/ZnS 4:1-SDS one was stable for about 11 weeks. After sodium dodecyl sulphate capping, unimodal particle size distribution was obtained with particle size medians approaching, respectively, 123 nm and 188 nm for CuInSe2/ZnS 5:0-SDS and CuInSe2/ZnS 4:1-SDS nanocomposites. Successful stabilization of the prepared nanosuspensions due to sodium dodecyl sulphate covering the surface of the nanocomposite particles was confirmed by zeta potential measurements. The prepared CuInSe2/ZnS 5:0-SDS and CuInSe2/ZnS 4:1-SDS nanosuspensions possessed anti-myeloma sensitizing potential assessed by significantly reduced viability of multiple myeloma cell lines, with efficient fluorescence inside viable cells and higher cytotoxic efficacy in CuInSe2/ZnS 4:1-SDS nanosuspension.

Extreme values of Young’s modulus of tetragonal crystals

The extreme values of Young’s modulus for six- and seven-constant tetragonal crystals are found using the necessary and sufficient conditions for the extrema of the functions of two variables. Theoretical and numerical analyzes of stationary and extreme values are performed based on experimental data on elastic constants collected in the Landolt–Börnstein reference book. Five such Young’s moduli are formed in the case of six-constant and seven-constant tetragonal crystals. It is found how the stationary and extremal values of Young’s modulus depend on three anisotropy coefficients that disappear in the limit of an isotropic material. Simple analytical dependences of some stationary and extreme values of Young’s moduli of six-constant crystals are obtained. In the case of stationary values of Young’s modulus of seven-constant tetragonal crystals, the coefficients included in the sufficient conditions for the extremum of the function of two variables are estimated numerically. Tetragonal crystals (Hg2I2, Hg2Br2, Hg2Cl2, TeO2, (NH2)2CO, LiY0.5Tb0.5F4 and C(CH2OH)4) with a large difference between the maximum and minimum values of Young’s modulus are revealed. It is shown that six-constant tetragonal crystals may have a greater difference between global extrema than seven-constant tetragonal crystals. It is found that six-constant tetragonal crystals with a large difference between the global extrema of Young’s modulus have a negative Poisson’s ratio. In the case of seven-constant tetragonal crystals, such relationship has not been identified. A classification scheme based on the dependence of three stationary values of Young’s modulus on two dimensionless parameters is proposed.