Triclinic Phase Research Articles

A Facile Route to Synthesize DyF3/Bi2O3 Nanowires and Sensitive L-cysteine Sensing Properties

DyF3/Bi2O3 nanowires with orthorhombic DyF3 and triclinic Bi2O3 phases were synthesized via a facile hydrothermal route using sodium dodecyl sulfate (SDS). The composite nanowires were characterized by X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The obtained composite nanowires have the length of longer than 10 μm and diameter of about 20–100 nm. X-ray photoelectron spectroscopy confirms the composition of Dy, F, Bi and O in the composite nanowires. The formation process of the DyF3/Bi2O3 nanowires was analyzed based on the morphological and structural evolution of the products from different growth conditions. The cyclic voltammetry (CV) measurement demonstrates good electro-catalytic activity of the composite nanowires towards L-cysteine. Two pairs of CV peaks at +0.08 V, −0.43 V and −0.48 V, −0.78 V, respectively are observed at the DyF3/Bi2O3 nanowires modified glassy carbon electrode. DyF3/Bi2O3 nanowires modified glassy carbon electrode detects L-cysteine linearly over a concentration range from 0.001 to 2 mM with a detection limit of 0.25 μM. Moreover, the results show good selectivity, reproducibility and stability of the DyF3/Bi2O3 nanowires as a promising candidate for L-cysteine determination.

New designing (NH4)2SiP4O13 nanowires and effective photocatalytic degradation of Malachite green and antimicrobial properties

Recently, organic chemicals, alcohols, dyes, acids and toxic chemical wastes are directly connected with water in many places. Then this pollutant removal process has been followed by various methods and researchers are not satisfied with these methods so new methods of photocatalyst have been proposed. Therefore, authors are involved in the important dyes removal effort. Hereby, the efficiency, health problems, and reusability issues are controlled and protected in the environment. (NH4)2SiP4O13 material was synthesized by a simple chemical route, this material has low bandgap energy and this result was carried out by DRS UV Visible spectroscopy. The (NH4)2SiP4O13 nanonests were tested to various instruments such as XRD, Raman, FT-IR, FE-SEM, and HR-TEM with EDX analysis. These results are confirmed and successfully identified to triclinic phase and spider nest-like morphologies. This can be assigned to the good un-uniform shape with the ranges at 1 µm to 20 nm. The (NH4)2SiP4O13 nanonest M-O-M and M-OH and M-O modes were confirmed to the FT-IR results spectroscopy and this M-O mode was much correlated in Raman spectroscopy. (NH4)2SiP4O13 nanonest was tested in antibacterial activity with using various strains such as Gram- positive (Staphylococcus aureus (S.a)) and Gram-negative -Klebsiella pneumonia (K.p) bacteria’s. As the proposed catalyst has a higher photocatalytic efficiency and stability also monitored.

Sulfuric Acid Solutions of [Pt(OH)4(H2O)2]: A Platinum Speciation Survey and Hydrated Pt(IV) Oxide Formation for Practical Use

The systematic study of the platinum speciation in sulfuric acid solutions of platinum (IV) hydroxide {[Pt(OH)4(H2O)2], HHPA} was performed with the use of a combination of methods. Depending on the prevailing Pt form, the three regions of H2SO4 concentration were marked: (1) up to 3 M H2SO4 forms unstable solutions gradually generating the PtO2·xH2O particles; (2) 4-12 M H2SO4, where the series of mononuclear aqua-sulfato complexes ([Pt(SO4)n(H2O)6-n]4-2n, where n = 0···4) dominate; and (3) 12 M and above, where, along with [Pt(SO4)n(H2O)6-n]4-2n species, the polynuclear Pt(IV) species and complexes with a bidentate coordination mode of the sulfato ligand are formed. For the first time, the salts of the aqua-hydroxo Pt(IV) cation [Pt(OH)2(H2O)4]SO4 (triclinic and monoclinic phases) were isolated and studied with a combination of methods, including the single-crystal X-ray diffraction. The formation of PtO2·xH2O particles in sulfuric acid solutions (1-3 M) of HHPA and their spectral characteristics and morphology were studied. The deposition of PtO2·xH2O was highlighted as a convenient method to prepare various Pt-containing heterogeneous catalysts. This possibility was illustrated by the preparation of Pt/g-C3N4 catalysts, which show an excellent performance in catalytic H2 generation under visible light irradiation with a quantum efficiency up to 5% and a rate of H2 evolution up to 6.2 mol·h-1 per gram of loaded platinum.

Dynamics of collective modes in an unconventional charge density wave system BaNi2As2

BaNi2As2 is a non-magnetic analogue of BaFe2As2, the parent compound of a prototype pnictide high-temperature superconductor, displaying superconductivity already at ambient pressure. Recent diffraction studies demonstrated the existence of two types of periodic lattice distortions above and below the triclinic phase transition, suggesting the existence of an unconventional charge-density-wave (CDW) order. The suppression of CDW order upon doping results in a sixfold increase in the superconducting transition temperature and enhanced nematic fluctuations, suggesting CDW is competing with superconductivity. Here, we apply time-resolved optical spectroscopy to investigate collective dynamics in BaNi2As2. We demonstrate the existence of several CDW amplitude modes. Their smooth evolution through the structural phase transition implies the commensurate CDW order in the triclinic phase evolves from the high-temperature unidirectional incommensurate CDW, and may indeed trigger the structural phase transition. Excitation density dependence reveals exceptional resilience of CDW against perturbation, implying an unconventional origin of the underlying electronic instability.

Unraveling the reasons behind lead phthalocyanine acting as a good absorber for near-infrared sensitive devices

Lead phthalocyanine (PbPc) is well known to be used as a good near-infrared (NIR) light absorber for organic solar cells (OSCs) and photodetectors. The monoclinic and triclinic phases have been understood to absorb the visible and NIR regions, respectively, so far. In the present study, we demonstrated from the absorption spectra and theoretical analysis that the visible band considerably originates from not only the monoclinic but also the amorphous and triclinic phases, and revealed the exciton dynamics in the PbPc film from static/time-resolved photoluminescence (PL), which are first reported. By comparing the external quantum efficiency between PbPc- and ZnPc-based OSCs in relation to their structure, morphology, and optical (absorption and PL) characteristics, we unraveled the reasons behind the PbPc film used as a good absorber for NIR-sensitive devices.

Phonon-induced rotation of the electronic nematic director in superconducting Bi2Se3

The doped topological insulator ${A}_{x}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, with $A={\mathrm{Cu},\mathrm{Sr},\mathrm{Nb}}$, becomes a nematic superconductor below ${T}_{c}\ensuremath{\approx}3$--4 K. The associated electronic nematic director is described by an angle $\ensuremath{\alpha}$ and is experimentally manifested in the elliptical shape of the in-plane critical magnetic field ${H}_{c2}$. Because of the threefold rotational symmetry of the lattice, $\ensuremath{\alpha}$ is expected to align with one of three high-symmetry directions corresponding to the in-plane nearest-neighbor bonds, consistent with a ${Z}_{3}$-Potts nematic transition. Here, we show that the nematic coupling to the acoustic phonons, which makes the nematic correlation length tend to diverge along certain directions only, can fundamentally alter this phenomenology in trigonal lattices. Compared to hexagonal lattices, the former possesses a sixth independent elastic constant ${c}_{14}$ due to the fact that the in-plane shear strain doublet $({\ensuremath{\epsilon}}_{xx}\ensuremath{-}{\ensuremath{\epsilon}}_{yy},\ensuremath{-}2{\ensuremath{\epsilon}}_{xy})$ and the out-of-plane shear strain doublet $(2{\ensuremath{\epsilon}}_{yz},\ensuremath{-}2{\ensuremath{\epsilon}}_{zx})$ transform as the same irreducible representation. We find that, when ${c}_{14}$ overcomes a threshold value, which is expected to be the case in doped ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, the nematic director $\ensuremath{\alpha}$ unlocks from the high-symmetry directions due to the competition between the quadratic phonon-mediated interaction and the cubic nematic anharmonicity. This implies the breaking of the residual in-plane twofold rotational symmetry (${C}_{2x}$), resulting in a triclinic phase. We discuss the implications of these findings for the structure of nematic domains, for the shape of the in-plane ${H}_{c2}$ in ${A}_{x}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, and for the presence of nodes inside the superconducting state.

Direct determination of thermal expansion coefficients from the profile fitting of a diffractogram

Abstract This paper presents a set of files for working with Topas software in order to calculate the thermal expansion coefficients of a crystal phase as a function of the temperature from a set of powder diffractograms. All the calculations and profile fittings are performed in the same run, in cascade and without interruption. Free graphics software GNUPLOT reads the output files in order to display both the characteristic three-dimensional thermal expansion surface and any section of this surface. The results are also generated as text files. The files also calculate the thermal expansion coefficients in any [u, v, w] direction and at any temperature, and the angles between the principal axes and the crystallographic axes. The user can modify the input text files to their requirements. The calculations have been checked with calculated diffractograms at different temperatures for a triclinic, monoclinic and tetragonal phase. The calculated coefficients have been compared with previous works and show good agreement. The extent to which the peak/noise ratio of the diffractogram affects the calculated thermal expansion coefficients is also discussed.

Assessment of hydrothermal parameters in the wet synthesis of α- and β-BiTaO4 by in situ synchrotron X-ray diffraction

Synchrotron X-ray diffraction was used for in situ monitoring of hydrothermal precursors calcination to obtain BiTaO4 in the orthorhombic (α) and triclinic (β) crystal phases. Different precursors were prepared varying time (24 and 48 h) and temperature (150 and 200 °C) of hydrothermal treatment. According to the results of in situ X-ray analysis during calcination of the precursors, the α- and β-BiTaO4 phases were achieved from the hydrothermal precursors treated at 200 °C. When the hydrothermal treatment time was carried out for 24 h, a precursor with Bi1−xTaxO1.5−x (fluorite structure, like δ-Bi2O3) and BiOCl phases was obtained, which evolved to Bi24Cl10O31 phase with heating. The presence of the chlorine-containing phases and the low crystallinity of the hydrothermal precursor contributed to the formation of β-BiTaO4. When the precursor is obtained with 48 h of hydrothermal treatment, only the Bi1−xTaxO1.5−x crystalline phase was identified and when heated it evolved to α-BiTaO4 phase at 550 °C. This is the first time that the pure orthorhombic phase is obtained from a wet synthesis method. All identified phases were confirmed by Rietveld refinement.

Optical absorption and resonance Raman scattering spectra of lead phthalocyanine and chloroaluminum chlorophthalocyanine thin films

The optical absorption spectra (1.2–2.5 eV) and resonance Raman spectra (100–3000 cm−1) of lead phthalocyanine (PbPc) and chloroaluminum chlorophthalocyanine (ClAlClPc) thin films with thickness of 190 and 200 nm, respectively, were studied. The films were deposited using thermal evaporation in vacuum (6.5 mPa) onto silicon substrates held at room temperature. During thermal annealing of PbPc and ClAlClPc films, the transition from monoclinic to triclinic crystal phase was observed. It is shown that the second-order Raman spectra of PbPc and ClAlClPc films are mainly formed by overtones and combinations of the first-order bands with presumed B1 symmetry.

Phase Transitions and Amorphization of M2AgF4 (M = Na, K, Rb) Compounds at High Pressure

We report the results of high-pressure Raman spectroscopy studies of alkali metal fluoroargentates (M2AgF4, where M = Na, K, Rb) combined with theoretical and X-ray diffraction studies for the K member of the series. Theoretical density functional calculations predict two structural phase transitions for K2AgF4: one from low-pressure monoclinic P21/c (beta) phase to intermediate-pressure tetragonal I42d structure at 6 GPa, and another to high-pressure triclinic P1 phase at 58 GPa. However, Raman spectroscopy and X-ray diffraction data indicate that both polymorphic forms of K2AgF4, as well as two other fluoroargentate phases studied here, undergo amorphization at pressures as low as several GPa.

Photoinduced Single-Crystal to Single-Crystal Transformation via Conformational Change with Turn-On Fluorescence

Single-crystal to single-crystal (SCSC) transformation by phototrigger is presently attracting immense research interest in many fields such as sensors, actuators, artificial muscles, soft robotics, and energy harvesting. However, the only success of rare examples has been achieved by SCSC transformation so far, involving a change in molecular composition based on photocyclization reactions. Here, we show photoinduced SCSC transformation of 3-methylene-2-(quinolin-8-yl) isoindolin-1-one (MQIO) derivatives from monoclinic to triclinic phase via conformational change, just as “small input and big output”. UV light induces a molecular conformation change of MQIO-H with rotation (11.3°) of the carbon–nitrogen single bond. The conformational changes of MQIO-H lead to the slides of molecular packing in crystals, finally resulting in the SCSC transformation from the monoclinic to the triclinic phase. In addition, the SCSC transformation was accompanied by turn-on fluorescence and shape changes of single crystal. The shape changes of single crystals can be clearly observed by UV light triggering under an optical microscope. This work provides a strategy to achieve SCSC transformation via photoinduction.

High-energy–density carbon-coated bismuth nanodots on hierarchically porous molybdenum carbide for superior lithium storage

The use of carbon-based supports, such as graphene and porous carbon, is a well-established approach to overcome the rapid capacity fading issues associated with alloy-based anode materials in lithium-ion batteries (LIBs). However, adopting carbonaceous materials that typically exhibit a low density eventually diminishes the primary purpose of alloys as high-energy–density anode materials. In this study, we introduce three-dimensional hierarchically porous molybdenum carbide (PMC) with high energy density, robust mechanical strength, and high electronic conductivity, which make it a promising alternative support for suppressing the huge volume expansion of alloying-based materials. Carbon-coated, ultrasmall Bi nanodots with an average size of 6.4 nm are uniformly embedded on the PMC surface (denoted as C-Bi/PMC) by facilitating heterogeneous nucleation. When tested as an anode in an LIB, the C-Bi/PMC electrode exhibits a high reversible capacity of 422 mAh g−1 at 50 mA g−1, high-rate capacity of 268 mAh g−1 at 1000 mA g−1, and long-term stability of 400 mAh g−1 at 250 mA g−1 over 500 cycles followed by 0.002 mAh g−1 decay per cycle at 5000 mA g−1 over subsequent 1000 cycles. When paired with LiNi0.5Co0.2Mn0.3O2 cathode as full-cell LIBs, the C-Bi/PMC anode deliver high gravimetric and volumetric energy densities of 352 Wh kg−1 and 563 Wh L–1, respectively. In-situ X-ray diffraction patterns captured during cycling reveal that the Li+-ion insertion mechanism in the voltage plateau region at 0.7–1.0 V consists of the intercalation between Bi layers followed by the formation of triclinic LiBi phase and the subsequent transition of triclinic LiBi to cubic Li3Bi phase.

Ag doped Sn3O4 nanostructure and immobilized on hyperbranched polypyrrole for visible light sensitized photocatalytic, antibacterial agent and microbial detection process.

Ag doped Sn3O4 Nanostructure and immobilized on hyperbranched polypyrrole is investigated in this project. The product was synthesized by the hydrothermal synthesis method. The surface and structural characteristics of the product was studied by different instrumental analysis. The fabricated nanocomposites was utilized as a nano photocatalyst in the removal of methylene blue dye. The crystallography results depicts the triclinic phase of Sn3O4 with the crystallite size 36.3nm. The band gap of the Ag-Sn3O4/hyperbranched polypyrrole was found 1.50eV from kubelka-munk measurements. The specific surface area was increased in the presence of the hyperbranched polypyrrole as compared to Ag-Sn3O4 samples. The photo-catalytic activity of composites was found 100.0% degradation of CR in 30min under visible light irradiation. The catalytic kinetic was followed from the first kinetic model. Moreover, the Ag/Sn3O4/hyperbranched polypyrrole was applied as a bactericidal agent against Streptococcus pneumoniae, and Pseudomonas aeruginosa bacteria. Determination of Streptococcus pyogenes as a pathogenic bacteria was investigated by using aptamer/Ag/Sn3O4/hyperbranched polypyrrole in peroxidase activity. The detection limit of S. pyogenes was 71.0CFU/mL by using the nano-aptamer.

Monoclinic–triclinic phase transition induced by pressure in fergusonite-type YbNbO4

We have carried out a high-pressure study on monoclinic fergusonite-type YbNbO4. Synchrotron powder x-ray diffraction experiments and density-functional theory simulations have been performed. We found a gradual increase of symmetry under compression, with calculations predicting a second-order monoclinic–tetragonal transition at 15 GPa. However, experiments provided evidence of a transition at 11.6 GPa to a triclinic structure, described by space group . The appearance of the triclinic phase, which according to calculations is dynamically unstable under hydrostatic conditions, seems to be related to the presence of non-hydrostatic stresses. The triclinic high-pressure phase remains stable up to 31.9 GPa and the phase transition is not reversible. We have determined the pressure dependence of unit-cell parameters of both phases and calculated their room-temperature equation of state. For the fergusonite-phase we have also obtained the isothermal compressibility tensor. In addition to the high-pressure studies, we report ambient-pressure Raman and infrared spectroscopy measurements which have been compared with density-functional theory calculations.

Unique multiferroics with tunable ferroelastic transition in antiferromagnet Mn2V2O7

Multiferroics have received considerable interest over the last decade due to the fascinating fundamental phenomena and potential use in various applications, such as low-power electronics and spintronics. Among those, investigations have focused on the coexistence of ferroelectric and ferromagnetic materials. Here, we report the rare case that the para-to ferroelastic ordering transition in antiferromagnet Mn2V2O7 occurred at TS = 260–280 K, verified by temperature-dependent magnetization measurements, dielectric, differential scanning calorimetry, and macroscopic strain-stress hysteresis loops. Furthermore, this transition was accompanied by a structural transition from the high-temperature C2/m monoclinic phase (β-phase) to a low-temperature P1¯ triclinic phase (α-phase), as identified by temperature-dependent X-ray diffraction. Consequently, TS can be successfully increased by Co- and Ni-doping and decreased by Ca-doping. Thus, the phase diagram was established for the structural stability of (Mn1-xAx)2V2O7 (A = Co, Ni, and Ca). In addition, the physical and chemical pressure effects were applied on (Mn1-xCax)2V2O7 to correlate the ferroelastic (TS) and antiferromagnetic (TN) orderings. Consequently, the magnetoelastic coupling was revealed, and a unique multiferroic material (Mn2V2O7) with a ferroelastic and antiferromagnetic ordering was obtained.

A DFT study of perovskite type halides KBeBr3, RbBeBr3, and CsBeBr3 in triclinic phase for advanced optoelectronic devices

The structural, electronic, magnetic, optical, vibrational, thermodynamic and mechanical properties of beryllium based perovskite type halides KBeBr3, RbBeBr3, and CsBeBr3 in triclinic phase have been investigated by utilizing PBE + GGA functional based on density functional theory in CASTEP simulation code. The determined lattice constants for considered perovskite type halides are listed as 5.7125 Å, 5.7202 Å and 5.9533 Å for KBeBr3, RbBeBr3, and CsBeBr3, respectively. The electronic properties have been determined and it is observed that these materials show insulator type character. The observed energy band gaps are in the order of 4.0 eV, 4.2 eV, and 4.7 eV for KBeBr3, RbBeBr3, and CsBeBr3, respectively as calculated by hybrid HSE06 functional. The optical properties like dielectric function, absorption coefficient, conductivity, extinction coefficient etc. also predict that the studied perovskite type halides are the potential candidate for optoelectronic devices. Additionally, the dynamic vibrational stability has been calculated and the determined phonon energy dispersion curves predict that these compounds are dynamically stable. Also, the thermodynamic parameters including enthalpy, free energy and temperature time's entropy have been investigated. Moreover, the mechanical and elastic properties of considered materials are also calculated to check their reliability, stability and easy handling for optoelectronic applications. This first principle investigation of computational properties of the novel materials implement an advance route to the theorists and experimentalists for the new potential applications in the renewable and advanced optoelectronic devices.

Prediction of ternary superconducting YCH12 using a novel solid hydrogen source under high pressure

Hydride superconductor YCH12, which can be formed using a new hydrogen source adamantine, was explored using DFT calculations. The results revealed a maximal Tc ∼112 K in the triclinic phase at 180 GPa attributed to a strong electron–phonon coupling around 3.80.

Multistage Structural Ordering and Crystallization of Poly(trimethylene terephthalate) during Sub-Tg Stretching: Synergetic Effects of Chain Orientation and Conformational Transition

Crystallizable glassy polymers can undergo multistage structural evolutions and form multiple types of ordered phases (e.g., mesomorphic and crystalline phases) during stretching below their glass transition temperatures (Tg). However, the structural evolution of polymers during sub-Tg stretching and the associated molecular mechanisms have not been well understood. In this work, we investigated the multistage structural ordering of glassy polymers and the related mechanisms during stretching below Tg by studying poly(trimethylene terephthalate) (PTT) as a model system. Roles of chain orientation and conformational transition on the multistage structural evolution of melt-quenched PTT were elucidated through a loading–unloading experiment. When stretched below Tg (e.g., 25 °C), the orientation of polymer chains and the stacking of phenylene rings lead to an intermolecular ordering, which induces the generation of a smectic C-like mesomorphic phase. The orientation degree of chains in such a mesomorphic phase increases with further stretching. This highly oriented mesomorphic phase transforms into a triclinic crystalline phase when the applied stress is unloaded. Stretching at a higher temperature (e.g., 40 °C) results in the formation of a more ordered mesomorphic phase and facilitates the induced crystallization due to the enhanced chain mobility. Fourier transform infrared results demonstrated that the unloading-induced crystallization of stretched PTT is originated from the trans-gauche conformational transition.

Domain Wall Dynamics in a Ferroelastic Spin Crossover Complex with Giant Magnetoelectric Coupling.

Pinned and mobile ferroelastic domain walls are detected in response to mechanical stress in a Mn3+ complex with two-step thermal switching between the spin triplet and spin quintet forms. Single-crystal X-ray diffraction and resonant ultrasound spectroscopy on [MnIII(3,5-diCl-sal2(323))]BPh4 reveal three distinct symmetry-breaking phase transitions in the polar space group series Cc → Pc → P1 → P1(1/2). The transition mechanisms involve coupling between structural and spin state order parameters, and the three transitions are Landau tricritical, first order, and first order, respectively. The two first-order phase transitions also show changes in magnetic properties and spin state ordering in the Jahn–Teller-active Mn3+ complex. On the basis of the change in symmetry from that of the parent structure, Cc, the triclinic phases are also ferroelastic, which has been confirmed by resonant ultrasound spectroscopy. Measurements of magnetoelectric coupling revealed significant changes in electric polarization at both the Pc → P1 and P1 → P1(1/2) transitions, with opposite signs. All these phases are polar, while P1 is also chiral. Remanent electric polarization was detected when applying a pulsed magnetic field of 60 T in the P1→ P1(1/2) region of bistability at 90 K. Thus, we showcase here a rare example of multifunctionality in a spin crossover material where the strain and polarization tensors and structural and spin state order parameters are strongly coupled.

Polymorphism in Na2(Co/Zn)P2O7 and Na2(Co/Fe)P2O7 Pyrophosphates: A Combined Diffraction and 31P NMR Study

Pyrophosphates of the general formula A2BP2O7 (A = alkali metal and B = transition metal) find applications in several technological fields, including rechargeable Na-ion batteries. They present a rich polymorphism vs composition, which may strongly influence their functional properties. Therefore, to selectively obtain a specific structure is crucial for applications. Here, we combine structural investigation techniques (solid-state NMR, X-ray and neutron diffraction, and DFT calculations) to investigate the crystal chemistry of the series Na2(M/M’)P2O7 with couples M/M’ = Co/Zn and Co/Fe. For both the series, a phase transition vs composition is observed. A tetragonal to orthorhombic phase transition is found for the Zn/Co series, and an orthorhombic to triclinic phase transition is found for the Co/Fe series. Such changes are interpreted in view of the different electronic structures of the transition metal ion. In addition, with the support of modeling, short- and long-range structural analysis, we show that the coexistence of two polymorphs for a given composition is possible, suggesting that the final structures may be strongly dependent upon the synthesis procedure.