Crystal State Research Articles

Paper test strip for fluorescence detection of iron ion based on nitrogen, zinc and copper codoped carbon dots

In this study, a test strip for fluorometric analysis of iron ion (Fe3+) was constructed based on nitrogen, zinc and copper codoped carbon dots (NZC-CDs) as fluorescence probes. NZC-CDs were synthesized by hydrothermal method. The morphology, size, components, crystal state and optical properties of NZC-CDs were characterized by transmission electron microscope (TEM), Fourier-transform infrared (FT-IR), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), UV–vis absorption and fluorescence spectroscopy techniques, respectively. NZC-CDs exhibited bright blue fluorescence under UV lamp with a quantum yield at 17.76%. The fluorescence of NZC-CDs was quenched by Fe3+ possibly due to the static quenching. The possible fluorescence quenching mechanism was also discussed. The quenching fluorescence was linear with the concentration of Fe3+ in the range of 2.5–400 μM with a low detection limit of 0.5 μM. For the convenient detection, the test strips based on filter paper were employed for Fe3+ assay. Moreover, the present approach was successfully applied in the determination of Fe3+ in real samples including black fungus, duck blood and pork liver. The sensing method had the potential application in more food analysis.

Trehalose and sodium pyrophosphate inhibit ice-induced freezing quality deterioration of surimi: A comparative study on water migration, ice crystal growth, glass transition and state diagram

Trehalose and sodium pyrophosphate inhibit ice-induced freezing quality deterioration of surimi: A comparative study on water migration, ice crystal growth, glass transition and state diagram

Fabrication of metal-organic frameworks derived Co3O4 loaded on TiO2: Influence of Fe loading on the Co3O4/TiO2 heterostructure for low-ppm benzene detection

We report the low-concentration detection of benzene using a metal–organic framework (MOF) derived Co3O4/TiO2 heterostructures loaded with 0.5–2 wt.% Fe synthesized using the co-precipitation method. The intrinsic properties of the heterostructures, such as their surface crystal structures, adsorption states, and chemical states, were examined. The sensing properties of the sensors were tested for nine (9) gases, including benzene, toluene, ethylbenzene (BTE), ethanol, acetone, carbon monoxide (CO), methane (CH4), carbon dioxide (CO2), and nitrogen dioxide (NO2) at various temperatures. The 1.0 wt.% Fe/Co3O4/TiO2 heterostructure-based sensor disclosed higher responses of ∼ 3 toward 2 ppm benzene at 175 °C. Furthermore, the sensor was able to experimentally detect benzene as low as 0.35 ppm and exhibited a low theoretical limit of detection (∼4.17 ppb) toward benzene at 175 °C, which increased at higher temperatures. The sensors were very stable in dry air and 20 % RH for 25 days. We infer that the excellent benzene detection could be associated with the loading of Fe3+ on the surface of the Co3O4/TiO2, which increased the specific surface area, narrowed the band gap, and provided numerous oxygen vacancies. Finally, the sensing mechanism linked with the loading of Fe3+ on the surface of Co3O4/TiO2 is discussed in detail.

Simultaneous removal of bisphenol A and Cr(Ⅵ) by Pd–TiO2: Significantly improve the photocatalytic activity through synergistic effect

The synergistic effect of heavy metal ions and organic pollutants can enhance the photocatalytic performance and provides a new idea for environmental governance, so it has important research value. In this work, we prepared Pd–TiO2 composites by ascorbic acid reduction method, and obtained the crystal structure, morphology and surface state information of the composites through a series of characterizations, which verified the successful preparation of the composites. It was used for simultaneous photocatalytic removal of bisphenol A (BPA) and Cr(Ⅵ), and it was found that the photocatalytic removal efficiency was significantly improved compared to their individual removal. This can be attributed to the synergistic effect between BPA and Cr(Ⅵ), where they enhance the separation efficiency of photogenerated electron-hole pairs and prolong the lifetime of photogenerated carriers. In addition, the effects of BPA concentration and Cr(Ⅵ) concentration on photocatalytic removal efficiency were also investigated. The mechanism of photocatalytic degradation of BPA by Cr(Ⅵ) coupling system was discussed by changing the experimental conditions, it is proved that the photocatalytic products of BPA can improve the removal efficiency of Cr(Ⅵ).

Electronic state dominated magnetism in CoSb single crystal

Both theoretical calculations and experiments indicate that a monolayer CoSb/SrTiO3 film has high-temperature superconductivity resembling the case of FeSe/SrTiO3. However, no superconductivity was found in the bulk CoSb, even under high pressure. Moreover, the magnetic properties of CoSb have always been controversial. Here, we have studied the electrical property, magnetic property, and X-ray photoelectron spectroscopy (XPS) of CoSb single crystals. Electrical and magnetic transportation measurements reveal that CoSb is a Pauli paramagnetic metal with non-Fermi liquid behavior. The XPS results showed that both Co and Sb in CoSb are in the zero-valence state, and they form an alloy in which the metallic bond is dominant. The Pauli paramagnetism of CoSb originates from its itinerant electrons. Therefore, unveiling the electronic states of CoSb single crystal not only help us understand its magnetic properties, but would also pave the way for searching for the possible high-temperature superconductivity.

Modifying the Electron Dynamics in High-Order Harmonic Generation via a Two-Color Laser Field

We investigate the harmonic emission from bichromatic periodic potential by numerically solving the time-dependent Schrödinger equation in the velocity gauge. The results show that the harmonic minimum is sensitive to the wavelength. Moreover, distinct crystal momentum states contribute differently to harmonic generation. In momentum space, the electron dynamics reveal a close relationship between the spectral minimum and the electron distribution in higher conduction bands. Additionally, by introducing an ultraviolet pulse to the fundamental laser field, the suppression of the harmonic minimum occurs as a result of heightened electron populations in higher conduction bands. This work sheds light on the harmonic emission originating from a solid with a two-atom basis.

Investigating the thermal robustness of soliton crystal microcombs.

Soliton crystals are a novel form of microcomb, with relatively high conversion efficiency, good thermal robustness, and simple initiation among the methods to generate them. Soliton crystals can be easily generated in microring resonators with an appropriate mode-crossing. However, fabrication defects can significantly affect the mode-crossing placement and strength in devices. To enable soliton crystal states to be harnessed for a broader range of microcomb applications, we need a better understanding of the link between mode-crossing properties and the desired soliton crystal properties. Here, we investigate how to generate the same soliton crystal state in two different microrings, how changes in microring temperature change the mode-crossing properties, and how mode-crossing properties affect the generation of our desired soliton crystal state. We find that temperature affects the mode-crossing position in these rings but without major changes in the mode-crossing strength. We find that our wanted state can be generated over a device temperature range of 25 ∘C, with different mode-crossing properties, and is insensitive to the precise mode-crossing position between resonances.

Multi-topological state via the Brillouin zone overlap for nonlinear frequency conversion.

Multiband topological edge states (TESs) or topological corner states (TCSs) in photonic crystals provide effective ways to manipulate the nonlinear frequency conversions. However, the deliberate design and the limited number of multibands lead to the difficulty of experimental realization of the topological nonlinear frequency conversion or higher harmonic generation. Here, we propose an effective method to achieve multiple TESs and TCSs by combining the Brillouin zones of multiple different systems. It is shown that the spectra of the subsystems disperse into different energy levels due to the inter-system hopping. Based on this approach, we construct a topological photonic crystal based on the Brillouin zone overlapped SSH model, which enables the overlapped TCSs to participate in nonlinear frequency conversion. Our scheme can provide a significant way to realize the topological nonlinear frequency conversion with double resonances or multiple resonances.

Native and non‐native mulch resulted in increased soil moisture and reduced plant recruitment in container plant restoration of coastal sage scrub

One challenge of habitat restoration is establishing healthy native plants that survive, grow, and reproduce. The addition of mulch after initial planting is thought to enhance native plant establishment. In our efforts to restore degraded sites at Crystal Cove State Park in Southern California, we compared two experimental mulch treatments made from native and non‐native plant material to unmulched plots. We planted four different native shrub species: Eriogonum fasciculatum, Malosma laurina, Isocoma menziesii, and Diplacus aurantiacus, and measured plant size, soil moisture, and plant density in the first year. In the second year, the same measurements were taken for I. menziesii and D. aurantiacus, which had greater survivorship in the first year. Our results showed significant differences in plant height, length, and width among the species but not between mulch treatments. However, soil moisture significantly varied between treatments, with native mulch plots having the greatest volumetric water content. In addition, mulch treatments had a significant effect on naturally recruiting plant density, with both mulch treatments having fewer native and non‐native seedling densities compared to control plots. Regarding survivorship, significant differences between species and treatment were observed only in the first year. Our results confirmed that mulch effectively helped retain higher soil moisture. Both locally sourced native and non‐native mulch had this benefit, although native mulch resulted in greater increases in soil moisture. While mulch reduced non‐native plant establishment, it also limited native recruitment, leading us to recommend that mulch be used only during the initial establishment of container plants.

Amino methoxy difluoroboron diketonate as a multicolor and multi-responsive polymorphic fluorescence emitter

We here report the synthesis and stimuli-responsive fluorescence nature of amino-methoxy-difluoroboron diketonate, DFB-NH2, which was prepared via the Curtius rearrangement to introduce a primary amine on the phenyl ring. Thanks to the NH2 group, the molecule exhibits intramolecular charge transfer (ICT) nature in the ground state of the solution and crystalline phases. We observed a quinoid-like structure and a typical head-to-tail H-type dimer structure in the crystal state. The single crystal with dark-red weak emission demonstrates a blue-shifted emission after mechanical smearing, as a unique mechanofluorochromism (MFC). The drop-casted sample on a paper sheet also demonstrates significant MFC. Additionally, characteristic acid-/base-responsivity is observed in the solution phase, polymer-dispersed films, and powder samples.

Modulating P-S anions of graphene supported amorphous nickel-iron nanocomposites by plasma to optimize overall water splitting activity

Hydrogen production by electrolysis of water is a key technology that has the potential to aid in the transition towards green sources of energy. In this regard, graphene-supported bifunctional electrocatalysts have shown to promote both oxygen evolution and hydrogen evolution processes. Although they are considered as one of the most potential electrocatalysts, modulation of their morphological structures and electronic configurations is challenging. Here, an efficient bifunctional electrocatalyst of graphene-supported NiFe-LDH with phosphorus-sulfur anion coordination is prepared based on the RF plasma treatment strategy. Reasonable P and S anion ratios optimize the partial coordination environment and crystal state, and effectively regulate the adsorption of OH∗, OOH∗, and protons, which consequently enhance the OER/HER performance. Plasma treatment generates vacancy defect structures for the catalyst, which modulates the surface morphology and electronic structure. Optimized graphene-supported NiFe-LDH catalysts with phosphorus-sulfur anion modulation show excellent electrocatalytic performance with 228 mV overpotentials for OER at 100 mA cm−2, in alkaline environments with excellent stability. This study offers recommendations for designing catalysts to produce effective water splitting.

Photoinduced Polymorphism of Fluorescent Organic Molecules in Solid State

AbstractA new organic molecule is found to be able to form different fluorescent aggregation states in both single crystals and powders. When irradiated with ultraviolet light, single crystals and powders exhibit an in situ change in the fluorescence color from blue to green and then to chartreuse without changing the chemical groups. This stems from photoinduced changes in the molecular conformation and packing in the solid state. Two or three fluorescence colors can be displayed simultaneously in a single organic crystal by controlling the irradiation time. Under irradiation with intense ultraviolet light, deformations, movements and in situ welding of crystals can be achieved by utilizing the photothermal effect. This work demonstrates a new strategy for inducing different behaviors of organic solid state with stimulation by single‐wavelength light.

Degeneration of topological corner, hinge, and surface states in three-dimensional photonic crystals.

The third-order topological insulators based on three-dimensional (3D) photonic crystals (PCs) have hardly been achieved because the nontrivial bandgap in 3D PCs is difficult to form. In this Letter, we elaborately construct 3D Su-Schrieffer-Heeger lattice in which the periodic modulation of refractive index is uniform in three axis directions. The high-order topological PCs are characterized by the nontrivial bulk polarizations and the mirror eigenvalues. Such a structure can achieve topological 1-codimensional surface states, 2-codimensional hinge states, and 3-codimensional corner states. More importantly, it is found for the first time, to the best of our knowledge, that the topological states exhibit a degeneration behavior, i. e., the corner, and hinge state, or corner and surface states coexist at nearly the same frequency, but maintain their own mode properties. The multiple topological states in 3D PCs as well as the degeneration of topological states will open a new window for the study of topological photonics.

Controlling the Crystallisation and Hydration State of Crystalline Porous Organic Salts.

Crystalline porous organic salts (CPOS) are a subclass of molecular crystals. The low solubility of CPOS and their building blocks limits the choice of crystallisation solvents to water or polar alcohols, hindering the isolation, scale-up, and scope of the porous material. In this work, high throughput screening was used to expand the solvent scope, resulting in the identification of a new porous salt, CPOS-7, formed from tetrakis(4-sulfophenyl)methane (TSPM) and tetrakis(4-aminophenyl)methane (TAPM). CPOS-7 does not form with standard solvents for CPOS, rather a hydrated phase (Hydrate2920) previously reported is isolated. Initial attempts to translate the crystallisation to batch led to challenges with loss of crystallinity and Hydrate2920 forming favorably in the presence of excess water. Using acetic acid as a dehydrating agent hindered formation of Hydrate2920 and furthermore allowed for direct conversion to CPOS-7. To allow for direct formation of CPOS-7 in high crystallinity flow chemistry was used for the first time to circumvent the issues found in batch. CPOS-7 and Hydrate2920 were shown to have promise for water and CO2 capture, with CPOS-7 having a CO2 uptake of 4.3 mmol/g at 195 K, making it one of the most porous CPOS reported to date.

Manganese oxides as positive electrode materials for rechargeable aluminum batteries

Three composites of carbon and amorphous MnO2, crystalline α-MnO2, or Mn2O3 were synthesized and investigated as the positive electrode materials for rechargeable Al batteries. For amorphous MnO2 and crystalline Mn2O3, the maximum discharge capacity was about 300 mAh g−1, which is the highest capacity among nonaqueous rechargeable Al batteries using manganese oxide positive electrodes. The amorphous MnO2 electrode showed a discharge capacity of more than 150 mAh g−1 even after 10 charge-discharge cycles. Crystal structure analysis and electronic state analysis suggested that crystalline Mn2O3 changed to amorphous MnO2 during the first charge process. These results suggest that the amorphous MnO2/carbon composite can be an excellent positive electrode material for rechargeable Al batteries.

Magnetic-field-induced transitions and the inverse magnetocaloric effect at liquid helium temperatures in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.80)

Magnetic field-induced phase transitions found in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.8) at T = 5 K may differ in nature and magnitude of the saturation magnetization of the initial weakly magnetic phase. These differences also affect the phenomena accompanying the transitions, specifically, the inverse magnetocaloric effect (MCE). In the current work, the mechanisms of these phenomena are analyzed within the framework of the magnetostructural model, which takes into account the difference in the limiting values of the magnetic order parameters in competing orthorhombic and hexagonal crystal structures. As follows from the analysis performed, the features observed in Mn1-xCoxNiGe can be explained by the realization at low temperatures of a metastable orthorhombic crystal state in magnetically ordered phases with a stable high-temperature hexagonal crystal structure.

Coupling between atoms and localized modes in a defect-free quasiperiodic photonic crystal

In this study, the evolution spectrum and emission dynamics of atoms in a defect-free quasiperiodic photonic crystal are studied. Quasiperiodic photonic crystal have advantages over periodic photonic crystal in terms of abundant and strong localized modes due to the quasiperiodic and self-approximation structures of quasiperiodic photonic crystal. The localized modes exhibit extremely large local density of states and high-quality factors in the quasiperiodic photonic crystal. The frequencies of the large local density of states of the localized modes do not depend on the polarization and the position in a particular area in the quasiperiodic photonic crystals. Due to the extremely large local density of states in the defect-free quasiperiodic photonic crystal, strong coupling between the atom and the localized mode in the quasiperiodic photonic crystal can easily occur. Correspondingly, the population of the excited state displays Rabi oscillation, and the emission spectrum of the atom splits into two peaks. Moreover, the Rabi oscillation and the evolution spectrum of the dressed atom depend on the radiation linewidth.

Non-Local Q-Tensor Approach for Description of Elastic Deformations of Nematic Liquid Crystals at Sub-Micron Scale

Within the framework of phenomenological approach, a generalized concept of a non-local order parameter, that have the form of a traceless correlation tensor function or a tensor integral operator, is introduced. The main relationships, which determine the equilibrium orientational states and the phase transitions of a deformed nematic liquid crystal, are described. The resulting expression for the free energy is quadratic with respect to the gradients of the order parameter tensor. The limiting transition of the non-local order parameter to the local one leads to an expression that complements the classical Oseen–Frank theory of elasticity. The considered model includes eight independent elastic constants. Three of them relate to "bulk" constants analogous to Frank constants, another three ones relate to "surface" constants, and the remaining two constants determine the anisotropic effect of the gradient of the scalar order parameter on the director field. The constants are necessary for the consideration of a liquid crystal state near defects, as well as for the description of orientation effects caused by the inhomogeneity of order parameter. It is shown that in the free energy expression, the "surface" terms contribute to the director orientation in the case of a non-constant scalar order parameter, even in the approximation of rigid boundary conditions.

Crystal structure and solution state of the C-terminal head region of the narmovirus receptor binding protein.

Genetically diverse paramyxoviruses are united in their presentation of a receptor-binding protein (RBP), which works in concert with the fusion protein to facilitate host-cell entry. The C-terminal head region of the paramyxoviral RBP, a primary determinant of host-cell tropism and inter-species transmission potential, forms structurally distinct classes dependent upon protein and glycan receptor specificity. Here, we reveal the architecture of the C-terminal head region of the RBPs from Nariva virus (NarV) and Mossman virus (MosV), two archetypal rodent-borne paramyxoviruses within the recently established genus Narmovirus, family Paramyxoviridae. Our analysis reveals that while narmoviruses retain the general architectural features associated with paramyxoviral RBPs, namely, a six-bladed β-propeller fold, they lack the structural motifs associated with known receptor-mediated host-cell entry pathways. This investigation indicates that the RBPs of narmoviruses exhibit pathobiological features that are distinct from those of other paramyxoviruses.

Effects of structure parameters on kink states of two-dimensional valley photonic crystals

We construct graphene-like valley photonic crystals (VPCs) by breaking spatial inversion symmetry in two-dimensional (2D) all-dielectric photonic crystals with honeycomb lattice. By tuning sizes of two scattering rods in unit cell, variations of topological band gaps of VPCs are investigated in detail. Further, valley-locked kink states and their unidirectional propagations are numerically studied by constructing two kinds of zigzag waveguide interfaces between two VPCs with opposite valley Chern number. Our results show that changing structure parameters of VPCs can effectively tune topological band gaps, adjust configurations of valley kink states, and control their unidirectional propagations, and particularly in some cases, resonant structures along waveguide interface can even destroy the valley-locked unidirectional propagations of kink states. We also investigate transverse localizations of kink states and reveal their robustness as they propagate along the interfaces. Our research gives further understandings on properties of VPCs, provides detailed regulation of kink states with change of structure parameters and paves the way for design of photonic devices based on VPCs.