Monoclinic Lattice Research Articles

Phase Transformation, Photocatalytic and Photoluminescent Properties of BiPO4 Catalysts Prepared by Solid-State Reaction: Degradation of Rhodamine B

Polycrystalline bismuth phosphate BiPO4 was synthesized by solid-state reaction at different temperatures varying from 500 to 900 °C. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and Raman spectroscopy. The low-temperature phase of BiPO4 has monoclinic structure with a space group P21/n, and was transformed into the monoclinic phase P21/m with a slight distortion of monoclinic lattice when it was heated above 500 °C. The effect of the transformation on the structure, morphology and photocatalytic properties was examined. The photocatalytic activity of each sample, in presence of Rhodamine B (RhB) in aqueous solution, was carried out and analyzed under UV light irradiation. Photoexperiments showed that the material prepared at 500 °C is the best catalyst with degradation efficiency of the order of 96% after 12 min of reaction time under UV light irradiation. This high photocatalytic efficiency could be due to their structural and morphological changes. The photocatalytic degradation mechanism of RhB in the presence of the best photocatalyst BiP-500 °C is proposed. The stability of the catalyst was also examined by carrying out four successive tests of the degradation in the presence of BiP-500 °C. Total organic carbon (TOC) was used to further estimate the rate of mineralization in the presence of BiP-500 °C (83% TOC removal). Photoluminescence experiments performed under UV-laser light irradiation revealed emissions in the green-orange range, with optimal intensities for the mix systems observed at 550 °C.

Optical properties of composites based on polyethylene and monoclinic Y2O3:Eu3+ nanoparticles

Polyethylenem-Y2O3:Eu3+ composites (PECs) containing 0.32, 0.77, and 1.79 wt% of well-dispersed sphere-like m-Y2O3:Eu3+ nanoparticles were obtained by in situ polymerization in the presence of a titanium-magnesium catalyst (TMC). TMC was synthesized by sequential deposition of organic magnesium and TiCl4 on m-Y2O3:Eu3+ that had been previously dehydroxylated at 650 °C. Detailed photoluminescence properties of the obtained composites as a function of m-Y2O3:Eu3+ content were investigated in combination with UV–Vis and IR spectroscopy data. It was shown that Eu3+ ions in monoclinic Y2O3 lattice are responsible for the high red emission of the composites. The effect of the РЕС host on the luminescence properties of m-Y2O3:Eu3+ was revealed. The obtained chromaticity coordinates with improved red color (0.653, 0.347) and high absolute luminescence quantum yield up to 23% make РЕСs potential promising materials for luminescent applications.

Role of Gd in Enhancing the Charge Carrier Mobility of Spray–Deposited BiVO4 Photoanodes

The emergence of BiVO4 as one of the most promising photoanodes for solar water splitting is largely driven by the success in dopant introduction and optimization to improve its photoelectrochemical performance. To this end, although less commonly used, several trivalent ions (e.g., In3+, Gd3+) that substitute Bi3+ have also been demonstrated to be effective dopants, which can increase the photocurrent of BiVO4 photoanodes. However, the main factor behind such improvement is still unclear as various explanations were proposed in the literature. Herein, Gd3+ is introduced to substitute Bi3+ in spray‐deposited BiVO4 films, which enables up to a ∼2‐fold photocurrent increase. Further analysis suggests that Gd‐doping enhances the carrier separation in BiVO4 and does not affect the catalytic and optical properties. Indeed, time‐resolved microwave conductivity measurements reveal that the carrier mobility of BiVO4 is increased by 50% with the introduction of Gd, while the carrier lifetime is unaffected. This mobility increase is rationalized to be a result of a higher degree of monoclinic lattice distortion in Gd‐doped BiVO4, as evident from the X‐ray diffraction and Raman spectroscopy data. Overall, these findings provide important insights into the nature and the underlying role of Gd in improving the performance of BiVO4.

Crystal structure of donepezil hydrochloride form III, C24H29NO3⋅HCl

The crystal structure of donepezil hydrochloride, form III, has been solved with FOX using laboratory powder diffraction data previously submitted to and published in the Powder Diffraction File. Rietveld refinement with GSAS yielded monoclinic lattice parameters of a = 14.3662(9) Å, b = 11.8384(6) Å, c = 13.5572(7) Å, and β = 107.7560(26)° (C24H30ClNO3, Z = 4, space group P21/c). The Rietveld-refined structure was compared to a density functional theory (DFT)-optimized structure, and the structures exhibit excellent agreement. Layers of donepezil molecules parallel to the (101) planes are maintained by columns of chloride anions along the b-axis, where each chloride anion hydrogen bonds to three donepezil molecules each.

Operando optical tracking of single-particle ion dynamics in batteries.

The key to advancing lithium-ion battery technology-in particular, fast charging-is the ability to follow and understand the dynamic processes occurring in functioning materials under realistic conditions, in real time and on the nano- to mesoscale. Imaging of lithium-ion dynamics during battery operation (operando imaging) at present requires sophisticated synchrotron X-ray1-7 or electron microscopy8,9 techniques, which do not lend themselves to high-throughput material screening. This limits rapid and rational materials improvements. Here we introduce a simple laboratory-based, optical interferometric scattering microscope10-13 to resolve nanoscopic lithium-ion dynamics in battery materials, and apply it to follow cycling of individual particles of the archetypal cathode material14,15, LixCoO2, within an electrode matrix. We visualize the insulator-to-metal, solid solution and lithium ordering phase transitions directly and determine rates oflithium diffusion at the single-particle level, identifying different mechanisms on charge and discharge. Finally, we capture the dynamic formation of domain boundaries between different crystal orientations associated with the monoclinic lattice distortion at the Li0.5CoO2 composition16. The high-throughput nature of our methodology allows many particles to be sampled across the entire electrode and in future will enable exploration of the role of dislocations, morphologies and cycling rate on battery degradation. The generality of our imaging concept means that it can be applied to study any battery electrode, and more broadly, systems where the transport of ions is associated with electronic or structural changes. Such systems include nanoionic films, ionic conducting polymers, photocatalytic materials and memristors.

Influence of annealing on structure, phase and electrophysical properties of vanadium oxide films

The aim of this work was to study the effect of the parameters of deposition process and subsequent annealing on the properties of vanadium oxide VO x films deposited by the pulsed reactive magnetron sputtering of a V target in an Ar/O 2 gas mixture. The dependences of the structure, phase, temperature coefficient of resistance (TCR), resistivity p , band gap Egof the films on the oxygen concentration in Ar/O 2 gas mixture during the deposition Г O2 , and the temperature of annealing in an O 2 atmosphere were obtained. The films were found to have an amorphous structure after deposition. Crystallization processes are observed at temperatures above 275 °C. In this case, depending on the temperature, polycrystalline films with a monoclinic, cubic or mixed crystal lattice are formed and a transition occurs from the intermediate oxide V 4 O 9 to the mixed phase VO 2 /VO x /V 2 O 5 and then to the higher oxide V 2 O 5 . The character of changes in p , TCR and Egof films coming from the change in the annealing temperature is complex and largely determined by Г O2 . It was established that with the view of using VO x films as thermosensitive layers, the following conditions of deposition and annealing would be preferable: films deposited at the oxygen concentration 25 % in Ar/O 2 gas mixture and annealed at a temperature of 250–275 °C in an O 2 atmosphere for 10 min. Under these conditions VO x films with the following properties were obtained: p = (1.0 – 3.0) . 10 -2 Ohm . m, TCR = 2.05 %/°C, and E g = 3.76–3.78 eV.

One-pot in situ fabrication of Cu-coupled rugby-shaped BiVO4 sosoloid for enhancing photocatalytic activity with SPR effect via ultrasonic hydrothermal strategy

One-pot wet chemistry strategy via an ultrasonic hydrothermal in situ procedure has been applied to construct a serial of monoclinic Cu-coupled rugby-shaped hierarchical BiVO4 sosoloids with diverse Cu coupling amount. The SEM and TEM images indicate that the coupled copper content had no effect on the crystalline phase of bismuth vanadate, but it had an important effect on its morphology, which changed from seed shape to rugby shape. As demonstrated by XRD and XPS analysis, it was found parts of Cu2+ doped into the BiVO4 monoclinic lattice to make it self-assemble into a rugby-shaped solid solution and another part of Cu loaded on the surface of BiVO4 sosoloids. Under visible light illumination (>420 nm), as-obtained 1.5% Cu-BiVO4 sosoloid had a degradation rate reached 99% for RhB within 50 min, and its photodegradation activity was 5.6 times higher than that of pure BiVO4. and remained above 96% after 5 cycles. The enhanced photocatalytic efficiency of xCu-BiVO4 sosoloids may be mainly attributed to the superior Cu-coupled rugby-shaped BiVO4 sosoloid microstructures with large specific surface area. During the ultrasonic hydrothermal process, the doping Cu2+ can effectively replace V5+ ions to form a virtual energy level accompanied by V4+, which can become a trapping center and capture the excitation electrons on the conduction band. The surface plasmon resonance (SPR) effect of copper can effectively expand the range of visible light response. On the other hand, d orbital electrons of Cu can quickly transfer to the BiVO4 conduction band according to Fermi energy level, so as to promote the interfacial charge transfer process, thus inhibiting the recombination of photo-generated carriers and improving the photocatalytic activity. Based on the synergetic effects of components in degradation of organic contaminants, this study provides a promising photocatalytic material driven by visible light for environmental remediation and protection.

Study on structural, electro-optical and optoelectronics properties of CuO nanoparticles synthesis via sol gel method

In this work, the popular metal oxide; Copper oxide (CuO) were prepared by well-known method; sol gel technique. The structural and morphological examination was carried out on the fabricated metal oxide and the XRD evaluation results validated the strong amalgamation of monoclinic bravais lattice system. The nano level of the Cu particles was tested and the size determined to be 52–36 nm which was found to be varied with respect to annealing temperatures. The structural modification of nanoparticle ensemble crystal by the application of temperatures was studied. The Photocatalytic ability was tested and it was evaluated by applying Tri-(chloroisopropyl) phosphate with CuO material. The optical property inducement was recognized in the material by observing UV–Visible characteristics curves. The electric operated optical response between lower and higher wavelength zones in visible region was tested by hyper polarization.

Compensation of Shallow Donors by Gallium Vacancies in Monoclinic β - Ga2O3

Knowledge of the origin of deep levels and their impact on electrical properties is critical for device applications of \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$. By annealing under an oxygen (${\mathrm{O}}_{2}$) atmosphere, the resistivity in shallow-donor (zirconium) doped \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$:$\mathrm{Zr}$ single crystals is found to increase by more than 10 orders of magnitude to (7 \ifmmode\pm\else\textpm\fi{} 4) \ifmmode\times\else\texttimes\fi{} 10 \ensuremath{\Omega} cm, which is comparable to the resistivity achieved by iron ($\mathrm{Fe}$) acceptor doping of (5 \ifmmode\pm\else\textpm\fi{} 3) \ifmmode\times\else\texttimes\fi{} 10 \ensuremath{\Omega} cm. We combine thermoelectric effect spectroscopy and positron annihilation spectroscopy (PAS), which are sensitive to deep levels and concentration of open-volume defects, with modeling of the electrical properties, to study these strongly compensated crystals. We find the compensating level in the ${\mathrm{O}}_{2}$-annealed \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$:$\mathrm{Zr}$ sample to be located at (0.727 \ifmmode\pm\else\textpm\fi{} 0.021) eV (E2*) below the conduction band, which correlates with a vacancy signal from PAS data. The defect is most likely the relaxed split $\mathrm{Ga}$ vacancy ${V}_{\mathrm{Ga}}^{i}$, rather than a simple gallium vacancy, considering theoretical predictions of a small energy barrier to relax. We observe that, due to the unique nature of these vacancies and anisotropy in the monoclinic lattice, the Doppler-broadening parameter is rather small compared with other wide-gap compounds, and in such a case the positron diffusion length is a suitable parameter to estimate the open-volume defect concentration.

Structural and optical behavior of nano-scaled luminous green-emitting Ca9Y(PO4)7:Tb3+ phosphor for competent lighting devices

Nano-sized Ca9Y(1-x)(PO4)7:xTb3+ phosphor series was synthesized via solution-combustion method for the first time. Rietveld study revealed the incorporation of Tb3+ ions into monoclinic host lattice of R3c(161) space symmetry. The diffuse reflectance spectral investigations depicted the lowering of band-gap (Eg) value from 4.44 to 4.27 eV for Ca9Y(PO4)7 and Ca9Y0.30Tb0.70(PO4)7, respectively. Under near-Ultraviolet excitation, PL spectra yielded luminous green emission at 544 nm (5D4 → 7F5). For Ca9Y0.30Tb0.70(PO4)7 system, quantum efficiency and CIE chromaticity coordinates were determined to be 96% and (0.252, 0.564), respectively. The results as-obtained predict the potential implications of Ca9Y0.30Tb0.70(PO4)7 nanophosphor as primary green component in WLEDs.

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.

Optical and electro-optical properties of Tl1-xCuxGaSe2 (0 ≤ X ≤ 0.02) crystals

The anisotropy of the refractive index and the electro-optical effect in Tl1-xCuxGaSe2(0≤X≤0/02) crystals were studied. Refractive indices were shown to rise as they approach their own absorption band. The electro-optical effect in TlGaSe2 crystals was studied. It was shown that the EO effect in the case where the light and external electric field are directed along the “C” axis within the studied electric fields (up to 5 kV / cm) is quadratic. The quadratic EO effect for TlGaSe2 equals 1.3 · 10−9 CGS units. It was found that when the electric field is directed perpendicular to the “C” axis and the light is directed along the “C” axis the EO effect is linear. The results of the EO measurements are consistent with the fact that the TlGaSe2 compounds crystallize in a monoclinic lattice, with the space group Cc, but at the same time the TlGaSe2 crystals have higher symmetry than Cc.

Self-assembly of superstructures at all scales

Summary Controllable assembly of molecular and nanoscale building blocks into uniform superstructures up to bulk dimensions remains a key challenge in the next phase of nanotechnology development. Here, we report the self-assembly of superstructures at all scales by taking advantage of the partial miscibility of water and 1-butanol to generate transient aqueous emulsion droplets that can encapsulate the target materials and introduce them into template holes. Further diffusion of water into 1-butanol depletes the emulsion droplets, assembling the building blocks into one well-defined superstructure in each hole. Superstructuring of various types and shapes of nanoparticles, biomolecules, and inorganic compounds could be achieved without the need for surfactants and chemical modifications. The versatility, scalability, low-cost, and accurate positioning are crucial advantages for the future development of advanced precision manufacturing.

Люминесцентные свойства коллоидных квантовых точек Ag-=SUB=-2-=/SUB=-S для фотокаталитических приложений

The structural and optical properties of colloidal Ag2S quantum dots in various environments are investigated. With the help of transmission electron microscopy, X-ray diffraction and X-ray energy dispersion analysis, the formation of colloidal Ag2S quantum dots with an average size of 2-3 nm with a monoclinic crystal lattice, and Ag2S/SiO2 core-shell systems based on them, has been established. The change in the luminescence quantum yield of quantum dots with the change of the surface environment state is shown. The decoration of TiO2 nanoparticles of 10-15 nm in size with Ag2S quantum dots was performed and the influence of the structure of the interfaces of quantum dots and their environment (2-mercaptopropionic acid, water, ethylene glycol, SiO2 dielectric shell with a thickness of 0.6 nm and 2.0 nm) on the formation of TiO2-Ag2S heterosystems was analyzed. For Ag2S quantum dots passivated with 2-mercaptopropionic acid, signs of charge phototransfer after adsorption on TiO2 nanoparticles surface have been established. Signs of reactive oxygen species appearance due to charge phototransfer in heterosystem are enstablished, based on methylene blue photobleaching under excitation of heterosystem outside of TiO2 fundamental absorption region,

Investigating the ranges of (meta)stable phase formation in (InxGa1−x)2O3 : Impact of the cation coordination

We investigate the phase diagram of the heterostructural solid solution (InxGa1-x)2O3 both computationally, by combining cluster expansion and density functional theory, and experimentally, by means of TEM measurements of pulsed laser deposited (PLD) heteroepitaxial thin films. The shapes of the Gibbs free energy curves for the monoclinic, hexagonal and cubic bixbyite alloy as a function of composition can be explained in terms of the preferred cation coordination environments of indium and gallium. We show by atomically resolved STEM that the strong preference of indium for six-fold coordination results in ordered monoclinic and hexagonal lattices. This ordering impacts the configurational entropy in the solid solution and thereby the (InxGa1-x)2O3 phase diagram. The resulting phase diagram is characterized by very limited solubilities of gallium and indium in the monoclinic, hexagonal and cubic ground state phases respectively but exhibits wide metastable ranges at realistic growth temperatures. On the indium rich side of the phase diagram a wide miscibility gap is found, which results in phase separated layers. The experimentally observed indium solubilities in the PLD samples are in the range of x=0.45 and x=0.55 for monoclinic and hexagonal single-phase films, while for phase separated films we find x=0.5 for the monoclinic phase, x=0.65-0.7 for the hexagonal phase and x>0.9 for the cubic phase. These values are consistent with the computed metastable ranges for each phase.

The study of gadolinium tantalum niobate (Gd(NbxTa1-x)O4) by local cathodoluminescence technique

In this work, the powder and ceramic samples of gadolinium tantalum niobate (Gd(NbxTa1-x)O4) grown by the liquid-phase method were studied. Phase homogeneity and composition were determined by x-ray diffraction analysis and electron probe microanalysis. Luminescent properties were studied by local cathodoluminescence technique. All samples obtained a high phase homogeneity. It was found that the dependence of the monoclinic lattice parameters on the niobium content in the niobium-tantalum pair has monotonic character. The solid solutions were formed at synthesis temperatures from 1180 to 1400°C. The sample of pure gadolinium niobate (GdNbO4) showed the maximal cathodoluminescence intensity.

Nonadiabatic Atomic-Like State Stabilizing Antiferromagnetism and Mott Insulation in MnO

This paper reports evidence that the antiferromagnetic and insulating ground state of MnO is caused by a nonadiabatic atomic-like motion, as is evidently the case in NiO. In addition, it is shown that experimental findings on the displacements of the Mn and O atoms in the antiferromagnetic phase of MnO corroborate the presented suggestion that the rhombohedral-like distortion in antiferromagnetic MnO, as well as in antiferromagnetic NiO is an inner distortion of the monoclinic base-centered Bravais lattice of the antiferromagnetic phases.

Defect structure of TiS3 single crystals with different resistivity

A defect structure of single-crystal whiskers TiS3 with different resistivity has been studied by the high resolution scanning transmission electron microscopy. The whiskers crystallize in one monoclinic lattice, but in two variants, A and B. The high-resistivity whiskers crystallize according to the A-variant, while the crystal structure of the low-resistivity whiskers is a mixture of the A- and B-variants. All planar defects in the crystals are described in terms of twinning with the twin boundaries running parallel to the (001) plane and located in the middle of the atomic layers. Sulfur vacancies are found both in high- and low-resistivity whiskers, but the density of vacancies is noticeably higher in the low-resistivity ones. It is shown that the magnitude and temperature dependence of the resistivity are determined by the density of vacancies and the number of B-domains in the TiS3 crystals, whereas the effect of twinning on the resistivity is negligible.

Structural and optical properties of green emitting Y2SiO5:Tb3+ and Gd2SiO5:Tb3+ nanoparticles for modern lighting applications

The optical and structural properties of Tb3+-doped yttrium and gadolinium oxyorthosilicate (Y2SiO5 and Gd2SiO5) phosphors were analyzed. The samples were synthesized via sol–gel combustion method using organic fuel. The phase purity and structural properties of the samples were determined via combined approach of powder X-ray diffraction, Fourier transformation infrared (FTIR) and transmission electron microscopy (TEM). X-ray measurements revel monoclinic crystal lattice with P21/c symmetry for both M2SiO5 (pure host) and M2SiO5:Tb3+ (doped) silicates, irrespective of the nature of metal (Y or Gd), presence or absence of Tb3+ in lattice and change in calcination temperature up to 1050 °C. FTIR analysis was applied to confirm the bonding of prepared materials. The appearance of bands corresponding to SiO4 tetrahedra (880–1020 cm−1) suggest the layered structure and support the diffraction measurements. TEM micrographs confirm the synthesis of spherical nanoparticles with filled morphology, narrow size distribution and slightly agglomerated crystallites of the samples. The elemental composition of prepared materials was determined using energy dispersive X-ray spectroscopy. The spectra show peaks only for elements assimilated within the host framework. The photoluminescence (PL) emission spectra of Tb3+-doped samples show 5D4 → 7FJ (J = 3–6) transitions under 254 nm-excitation. The dominant peak at 544 nm for 5D4 → 7F5 transition is responsible for the emission of green light on ultraviolet–visible excitation in both the Tb3+-doped host matrixes. Owing to advantageous properties like intense PL and high crystallinity, these nanophosphors could possess potential applications in the mercury free lighting sources and optoelectronic devices.

Thermal expansion and heat capacities of holmium and erbium orthotantalates ceramics

AbstractMonoclinic M‐orthotantalates of holmium and erbium ceramics were obtained by co‐precipitation and annealing at 1773 K and characterized by X‐ray powder diffraction, scanning electron microscopy, and chemical analysis. Using the high‐temperature X‐ray diffraction method, the temperature dependence of the monoclinic lattice parameters of both ceramics were determined at range 298‐1273 K. The molar heat capacity of M‐HoTaO4 and M‐ErTaO4 were measured by adiabatic (7‐350 K) and differential scanning (320‐1350 K) calorimetry. Standard thermodynamic function (entropy, enthalpy change, and reduced Gibbs energy) were calculated on the smoothed values of molar capacity, without taking into account contribution of low‐temperature interval: 0‐7 K for M‐HoTaO4 and 0‐8 K for M‐ErTaO4. The general shape of the anomalous Schottky contribution to the molar heat capacity was determined.