Crystal Mode Research Articles

Preparation, characterization and electrical properties of 80 PEO − 20 PVdF: x NaNO3 complexed polymer electrolyte systems

PEO (Polyethylene Oxide) and PVdF (Polyvinylidene Fluoride) based Coplexed Solid Polymer Electrolytes (CSPEs) have been prepared using solution casting method with different weight percentages of NaNO3 (Sodium Nitrate). DMF (Dimethyl Formamide) was used as common solvent. The prepared systems are characterized by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy) and DSC (Differential Scanning Calorimetry) to investigate the crystal structure, surface morphology, vibrational modes, and melting points respectively. Impedance spectroscopy is used to investigate the electrical, dielectric, and electric modulus properties of CSPE systems between temperatures of 298 K and 348 K in the frequency range of 100 Hz to 10 MHz. The ionic conductivity of polymer systems is found to increase with temperature. The maximum enhancement in conductivity (9.334x10-5 S cm−1) is observed for 5 wt% salt system, which is attributed to decrease in crystallanity and increase in the concentration of defects in space charge region formed between the host polymer and salt. Ion transport number has been calculated by using Wagner's polarization method and the maximum (0.89) is noticed for PPN-5 system.

Thermal and mechanical properties of poly(lactic acid)/poly(butylene adipate-co-terephthalate)/calcium carbonate composite with single continuous morphology

Abstract Poly(lactic acid)/poly(butylene adipate-co-terephthalate) with a content ratio of 90/10, and its calcium carbonate (CaCO3) composites with nano- and micro-sized particles were prepared by melt mixing. The dependence of thermal and mechanical properties of the composites on the particle size and addition content of the CaCO3 filler was investigated. The composite containing five parts micro-sized filler (abbreviated as 90L10B5mC, similarly hereinafter) exhibited α and α′ crystallines on cooling as 90L10B without fillers. 90L10B11mC and 90L10B11n5mC exhibited only α′ crystalline, and the others exhibited no discernible crystalline. Jeziorny method showed that the crystallization mode of poly(lactic acid) chains in different composites was close, and Mo method showed that the crystal growth mode in 90L10B11n5mC was different from others. Changes in thermal and mechanical properties were attributed to the overall connection strength which was dependent on the particle size and addition content of the CaCO3 filler. From the perspective of industrialization, 90L10B5n11mC was preferred.

Lasing Threshold of Conical Modes in 1D Photonic Crystals

Lasing Threshold of Conical Modes in 1D Photonic Crystals

Shaping the spin wave spectra of planar 1D magnonic crystals by the geometrical constraints

We present experimental and numerical studies demonstrating the influence of geometrical parameters on the fundamental spin-wave mode in planar 1D magnonic crystals. The investigated magnonic crystals consist of flat stripes separated by air gaps. The adjustment of geometrical parameters allows tailoring of the spin-wave frequencies. The width of stripes and the width of gaps between them affect spin-wave frequencies in two ways. First, directly by geometrical constraints confining the spin waves inside the stripes. Second, indirectly by spin-wave pinning, freeing the spin waves to a different extent on the edges of stripes. Experimentally, the fundamental spin-wave mode frequencies are measured using an all-optical pump-probe time-resolved magneto-optical Kerr-effect setup. Our studies address the problem of spin-wave confinement and spin-wave dipolar pinning in an array of coupled stripes. We show that the frequency of fundamental mode can be tuned to a large extent by adjusting the width of the stripes and the width of gaps between them.

Nonclassical Growth of Atomically Flat Two‐Dimensional Organic Single Crystals on a Liquid Surface through Fusion

AbstractOrganic single crystals with low defect density are key functional materials for next‐generation electronics. Classical crystallization commonly results in a high density of molecular steps, which are defects that can trap charge carriers and reduce the mobility of organic semiconductors. Herein, a novel nonclassical crystallization mechanism involving nucleation, fusion, and growth is designed. The introduction of the fusion stage changes the crystal growth mode from three‐dimensional island growth to two‐dimensional layer‐by‐layer growth and leads to large‐area two‐dimensional molecular crystals with almost no molecular steps. Therefore, the average mobility is observed to improve from 1.26 to 2.07 cm2 V−1 s−1. The nonclassical crystallization mechanism paves the way for atomically flat single crystals to probe the intrinsic optoelectronic properties of organic semiconductors.

Non-Hermitian skin effect and lasing of absorbing open-boundary modes in photonic crystals

We explore absorbing open-boundary modes in non-Hermitian photonic systems. The modes have a continuum spectrum in the infinite system-size limit and can exhibit the non-Hermitian skin effect. In contrast to the conventional non-Hermitian skin modes under the fixed-end open-boundary condition, the modes concerned exhibit a strongly size-dependent spectrum that gradually converges to the non-Bloch-band dispersion. The modes correspond to the poles of the $S$ matrix, and are closely related to the lasing. We demonstrate these properties in a two-dimensional non-Hermitian photonic crystal with gain having a point-(pseudo)gap topology.

Fabrication of 2D–0D Ti3AlC2@SmVO4 heterojunction nanocomposites for ultrasensitive electrochemical detection of sulfathiazole in environmental samples

Sonochemically combined 2D–0D Ti3AlC2@SmVO4 (TASV) nanocomposites are used for the electrochemical detection of Sulfathiazole (SFZ). TASV heterojunction composites are characterized thoroughly to understand its crystal structure, chemical composition, morphology, topography, vibrational modes and electronic states using X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Raman microscopy. The fabrication of the modified electrode is constructed by drop-casting the TASV layer onto the glassy carbon electrode (GCE). Being an excellent electrocatalyst, the TASV displayed a superior surface area. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are used to investigate the electrochemical property of TASV composites. The results show a remarkable detection range for SFZ sensing. Additionally, the determined limit of detection (LOD) for SFZ sensing is superior to other reported sensors. Subsequently, the TASV based electrochemical sensor can be advised for real-world sample analysis. River water and urine are used to investigate the performance of TASV sensors in real-world conditions, and the obtained results are highly admirable.

Design of a three-phase amplitude macro-pixel full-color complex spatial light modulator with an in-cell geometric phase retardation layer.

Complex spatial light modulation, which can simultaneously control the amplitude and phase of light, is an essential optical technology for holographic display. We propose a twisted nematic liquid crystal (TNLC) mode with an in-cell type embedded geometric phase (GP) plate for full-color complex spatial light modulation. The proposed architecture provides an achromatic full-color complex light modulation capability in the far-field plane. The feasibility and working characteristics of the design are validated through numerical simulation.

Rainbow trapping and releasing based on the topological photonic crystals and a gradient 1D array

Topological photonic crystal provides a platform for robust energy transport in photonic systems. In this letter, we propose a method for realizing rainbow trapping and releasing based on the topologically protected defect modes in dielectric photonic crystals. The photonic states of different frequencies are separated and trapped at different positions to form the topological rainbow. The all-dielectric planar nanostructures consist of deformed honeycomb lattices and a gradient 1D array, which is distinct from previous platforms where edge states appear at the interface between trivial and nontrivial crystals. Due to the simplification of the configuration, we can selectively control the stop position of the wave by modifying the bottom row of dielectric rods so that light can switch between the trapping state and releasing state. The robustness of the slowing light system is also investigated. These results are beneficial to multiple frequency tuning. The simplified structure could offer a novel method for micro-miniaturizing and applying optical communication equipment, such as optical storage and optical buffer.

Structure particularities and first, second order Raman spectra of LiNbO3:Tb near the concentration threshold

Defective structure particularities have been studied in pure non-stoichiometric (Li/Nb≠1) lithium niobate (NSLN) crystals and LiNbO3:Tb (2.24 wt%) crystal. NSLN Raman spectra contain low-intensity extra bands in the area 100-1000 cm−1 at different scattering geometries. The bands are not provided by the selection rules for LN. The bands are caused by static disorder in cation sublattice of crystals. Besides, we have established additional bands in the area 1300-2000 cm−1 of a LiNbO3:Tb (2.24 wt%) crystal Raman spectrum. The bands correspond to overtone states of crystal lattice polar fundamental modes. Second-order Raman spectrum of LiNbO3:Tb contains bands with frequencies higher than that of overtones of the highest-frequency fundamental polar modes with А1(Z) and Е(X,Y) symmetry type. The particularities are manifestation of bonded states of polar modes – bipolaritons; they convert in two entangled photons or in a bonded state – biphoton at an exit from the crystal.

Discerning the Vibrational Nature of ReS2 Raman Modes Using Solid-Angle-Resolved Raman Spectroscopy

ReS2 exhibits reduced crystal symmetry, which leads to pronounced anisotropy and intricate Raman vibrations. However, to date, the vibrational nature of ReS2 Raman modes has remained elusive, with unresolved theoretical disputes. Here, we study Raman vibrations in ReS2 crystals using solid-angle-resolved Raman spectroscopy, which allows us to leverage the full 3 × 3 Raman tensor to resolve the Ag-like and Eg-like nature of all the 18 Raman modes. Combined with pressure-dependent measurements, we observe distinct behavior in the Ag-like and Eg-like modes. Our findings show unambiguous experimental evidence for discerning the ReS2 Raman modes and can offer important insights into the vibrational nature of Raman modes in layered anisotropic crystals.

Surface waves and bulk Ruderman mode of a bosonic superfluid vortex crystal in the lowest Landau level

We determine and analyze collective normal modes of a finite disk-shaped two-dimensional vortex crystal formed in a compressible bosonic superfluid in an artificial magnetic field. Using the microscopic Gross-Pitaevskii theory in the lowest Landau level approximation, we generate vortex crystal ground states and solve the Bogoliubov-de Gennes equations for small amplitude collective oscillations. We find chiral surface waves that propagate at frequencies larger than those of the bulk Tkachenko modes. Furthermore, we study low frequency bulk excitations and identify a torsional Ruderman mode, which we find is well-described by a previously developed low-energy effective field theory.

High Quality Quasinormal Modes of Phononic Crystals for Quantum Acoustodynamics

High Quality Quasinormal Modes of Phononic Crystals for Quantum Acoustodynamics

High pressure Raman study of LiClO4

Lithium perchlorate (LiClO4), as one of the new high-energy oxidizers, is chosen for high pressure Raman research to gain a better understanding of the structure and stability, which is very important for the performance of an explosive. Raman spectra of LiClO4 crystal have been measured from ambient to 25.07 GPa with diamond anvil cells (DACs) at room temperature to investigate the structural stability of this system. Raman vibrational modes of LiClO4 crystal at ambient pressure were resolved comprehensively on the basis of our experimental and calculated results. Upon increase of pressure on LiClO4 crystal sample to 1.96 GPa, it was found that the LiClO4 crystal exhibited a pressure-induced first-order phase transformation behavior. The occurrence of a second phase transformation of LiClO4 crystal induced by pressure was observed at about 5.09 GPa. Both phase transformations were demonstrated based on the detailed spectroscopic analysis of the variations in the number of lattice modes, splitting of Raman bands and frequency jumps of the Raman vibrational modes of LiClO4 crystal.

Tunable properties of the defect mode of a ternary photonic crystal with a high T C superconductor and semiconductor layers

Abstract The tuning of a defect mode in a photonic crystal (PC) is of high significance for filter and sensor applications. We here investigate the tuning of the defect mode of a defective ternary PC with a semiconductor and high critical-temperature superconductor layers. A ternary photonic crystal with the heterostructure (semiconductor/superconductor/dielectric) is assumed. The transfer matrix method is employed to investigate the transmission of transverse electric waves. The refractive indices of the semiconductor and superconductor layers can be tuned by changing the operating temperature and the hydrostatic pressure. The defect mode and transmission properties can be controlled by using the hydrostatic pressure, operating temperature, frequency and thicknesses of the heterostructure layers. The analysis is performed in the frequency range of 20–65 THz. The proposed structure can be utilized as a biosensor and a narrowband transmission peaks filter.

Stimulated polariton scattering in an Yb laser pumped lithium niobate based continuous-wave singly resonant optical parametric oscillator

The effective refractive index of a dielectric medium modifies in the infrared spectral band due to a significant contribution from the vibrational modes by virtue of the presence of heavy ions. The coupling between electromagnetic (EM) modes and transverse optical (TO) vibrational modes is the underlying principle behind such a modification. This interaction manifests through the generation of polariton modes that can be observed in the Raman spectrum. However, they do not coincide with the peaks associated with the Raman scattering process. In the present work, we show that the polariton modes can be excited in a lithium niobate based continuous-wave singly resonant optical parametric oscillator (SRO) pumped by a single-frequency, near-infrared Yb-doped fiber laser. The stimulated polariton scattering process is triggered by a strong interaction between the mid-infrared resonant SRO signal beam and TO phonon modes of a lithium niobate crystal, which leads to generation of Stokes mode(s). Such mode(s) can be observed as side peak(s) in the SRO signal spectrum. The generated low energy polariton mode exhibits a dominant EM character, and this provides a plausible route to generate narrow linewidth far-infrared (FIR) or terahertz radiation by utilizing the high intra-cavity signal power in the SRO. In addition, the off-axis FIR generation process assists in reducing the thermal load on the lithium niobate crystal at high pump powers.

Photoinduced Split of the Cavity Mode in Photonic Crystals Based on Porous Silicon Filled with Photochromic Azobenzene-Containing Substances

Phototunable photonic structures based on electrochemically etched silicon filled with four photochromic azobenzene-containing compounds, a bent-shaped low-molar-mass substance and side-chain polymethacrylates and a copolyacrylate, were prepared, and their photo-optical properties were studied. It was found that irradiation of these composites with polarized blue light results in spectral changes in the photonic band gap (split of the cavity mode) associated with cooperative photo-orientation of azobenzene moieties inside silicon pores in the direction perpendicular to the polarization plane of the incident light. Kinetics of the photoinduced split is studied. The observed photoinduced split is completely reversible, and heating of the composites to temperatures above isotropization or glass transitions fully recovers the initial spectral shape of the photonic band gap. Thermal and temporal stabilities of the obtained photoinduced split were comparatively studied, and it was found that for composites with a bent-shaped substance and polymethacrylate shape of the reflectance spectra do not change over time at room temperature. The prepared composites have a high potential for the different applications in photonics.

Indomethacin: The Interplay between Structural Relaxation, Viscous Flow and Crystal Growth.

Non-isothermal differential scanning calorimetry (DSC) was used to study the influences of particle size (daver) and heating rate (q+) on the structural relaxation, crystal growth and decomposition kinetics of amorphous indomethacin. The structural relaxation and decomposition processes exhibited daver-independent kinetics, with the q+ dependences based on the apparent activation energies of 342 and 106 kJ·mol−1, respectively. The DSC-measured crystal growth kinetics played a dominant role in the nucleation throughout the total macroscopic amorphous-to-crystalline transformation: the change from the zero-order to the autocatalytic mechanism with increasing q+, the significant alteration of kinetics, with the storage below the glass transition temperature, and the accelerated crystallization due to mechanically induced defects. Whereas slow q+ led to the formation of the thermodynamically stable γ polymorph, fast q+ produced a significant amount of the metastable α polymorph. Mutual correlations between the macroscopic and microscopic crystal growth processes, and between the viscous flow and structural relaxation motions, were discussed based on the values of the corresponding activation energies. Notably, this approach helped us to distinguish between particular crystal growth modes in the case of the powdered indomethacin materials. Ediger’s decoupling parameter was used to quantify the relationship between the viscosity and crystal growth. The link between the cooperativity of structural domains, parameters of the Tool-Narayanaswamy-Moynihan relaxation model and microscopic crystal growth was proposed.

Electron microscopy and histopathological examination of canine papilomavirus

Diagnosis of canine papillomavirus (CPV) infection by histopathology, transmission and scanning electron microscopy is presented. The study is based on data obtained by examining nonregressing papillomas (warts) from naturally infected dogs with clinical manifestations of CPV infection. Papules on the mouth and lips were common bilaterally in all dogs. Confirmatory diagnosis of sick dogs was made by clinical findings, histopathology, transmission and scanning electron microscopy. Histopathological examination of hematoxylin and eosin stained papillomas revealed lymphoplasmocytic cell infiltration and fibrosis, parakeratosis in the dermis, papillary proliferation and intranuclear vacuole degeneration in the stratum spinosum. Electron microscopy demonstrated viral icosahedral capsid formation and non-enveloped viral structure of CPV. Transmission electron microscopy demonstrated viral particles and virions in the nuclei of infected cells, viral crystal mode formation in the nucleus. Scanning electron microscopy demonstrated virions and virus-like particles budding in the infected tissue. The findings of the study reveal that electron microscopy and histopathology are effective and sensitive methods in the diagnosis of CPV infection. Electron microscopy is the only imaging technique that allows direct visualization of viruses, along with affected tissues and cells, due to its nanometer-scale resolution. This study reveals the intracellular and extracellular viral pathogenesis, viral ultra structure and structural components of CPV. Present findings indicate canine papillomavirus causes canine papillomatosis, inclusion bodies are common in nonregressive infection, papillomavirus induces cytopathic effect and pathogenesis, viral particles located in the cell and forms crystal mode in nuclear space.

Tunable Plasmonic Devices by Integrating Graphene with Ferroelectric Nanocavity

AbstractGraphene plasmons can become the fundamental of novel conceptual photonic devices, resulting from their unique characteristics containing excitation at room temperature and tunable spectral selectivity in different frequencies. The pursuit of efficiently exciting and manipulating graphene plasmons is necessary and significant for high‐performance devices. Here, the graphene plasmon wave propagating in ferroelectric nanocavity array is investigated. It has been experimentally shown that the periodic ferroelectric polarizations can be used for doping graphene into desired spatial carrier density patterns. Based on a theoretical model that considers periodic ununiform conductivity across graphene sheet, the simulation results show surface plasmon polaritons (SPP) in graphene can be excited by an incident light in a similar way to the excitation of photonic crystal resonant modes. The graphene SPP resonance can be tuned from ≈720 to ≈1 000 cm−1 by rescaling the ferroelectric nanocavity array, and from ≈540 to ≈780 cm−1 by dynamically changing the applied gate voltage. This strategy of graphene carrier engineering to excite SPP offers a promising way for large‐scale, nondestructive fabrication of novel graphene photonic devices.