Properties Of Crystals Research Articles

Facile Synthesis of Oxygen-Doped g-C3N4 Mesoporous Nanosheets for Significant Enhancement of Photocatalytic Hydrogen Evolution Performance

In this work, oxygen-doped g-C3N4 mesoporous nanosheets (O-CNS) were synthesized via a facile recrystallization method with the assistance of H2O2. The crystal phase, chemical composition, morphological structure, optical property, electronic structure and electrochemical property of the prepared O-CNS samples were well investigated. The morphological observation combined with the nitrogen adsorption–desorption results demonstrated that the prepared O-CNS samples possessed nanosheet-like morphology with a porous structure. Doping O into g-C3N4 resulted in the augmentation of the specific surface area, which could provide more active sites for photocatalytic reactions. Simultaneously, the visible light absorption capacity of O-CNS samples was boosted owing to the regulation of O doping. The built energy level induced by the O doping could accelerate the migration rate of photoinduced carriers, and the porous structure was most likely to speed up the release of hydrogen during the photocatalytic hydrogen process. Resultantly, the photocatalytic hydrogen production rate of the optimized oxygen-doped g-C3N4 nanosheets reached up to 2012.9 μmol·h−1·g−1, which was 13.4 times higher than that of bulk g-C3N4. Thus, the significantly improved photocatalytic behavior was imputed to the synergistic effect of the porous structure, the increase in active sites, and the enhancement of visible light absorption and charge separation efficiency. Our research highlights that the synergistic effect caused by element doping will make a great contribution to the remarkable improvement in photocatalytic activity, providing a new inspiration for the construction of novel catalysts.

The Influence of Varying Ar/O2 Gas Ratio with Catalyst-Free Growth by Homemade Thermal Evaporation Technique

A nanostructured zinc oxide (ZnO) with different percentages of argon and oxygen gas flow rate was deposited on a silicon wafer by a simple hot tube thermal evaporation technique. The effect of different percentages of gas flow rate on the crystal structure, surface morphology and optical properties were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and RAMAN spectroscopy, respectively. The changes of morphologies from FESEM were significant where the grown ZnO nanostructures show three different shapes which are nanotripods, nanoclusters and nanorods at 5%, 10% and 25% of oxygen gas, respectively. EDX results revealed that Zn and O elements have a major percentage in the sample indicating a composition has high purity of ZnO. XRD patterns displayed the most intense diffraction peak of ZnO at (101), which exhibited a single crystalline hexagonal structure with preferred growth orientation in the c-axis. RAMAN scattering study found that synthesized ZnO shows the high intensity of E2 mode and low intensity of E1 mode attributed to all the samples having good crystal quality containing fewer structural defects. In conclusion, the E15 sample with a 25% oxygen gas flow rate was selected as an optimum result for synthesizing a homogenous surface and high crystallinity of ZnO by using a hot tube thermal evaporation process. This work can enhance the development of ZnO production in various applications.

Valence-state mixing and reduced magnetic moment in Fe3-δGeTe2single crystals with varying Fe content probed by X-ray spectroscopy.

We present a spectroscopic study of the magnetic properties of Fe3-δGeTe2 single crystals with varying Fe content, achieved by tuning the stoichiometry of the crystals. We carried out x-ray absorption spectroscopy and analyzed the x-ray circular magnetic dichroism spectra using the sum rules, to determine the orbital and spin magnetic moments of the materials. We find a clear reduction of the spin and orbital magnetic moment with increasing Fe deficiency. Magnetic susceptibility measurements show that the reduction in magnetization is accompanied by a reduced Curie temperature. Multiplet calculations reveal that the Fe2+ state increasingly mixes with a higher valence state when the Fe deficiency is increased. This effect is correlated with the weakening of the magnetic moment. As single crystals are the base material for exfoliation processes, our results are relevant for the assembly of 2D magnetic heterostructures.&#xD.

Evidence of striped electronic phases in a structurally modulated superlattice.

The electronic properties of crystals can be manipulated by superimposing spatially periodic electric, magnetic or structural modulations. Long-wavelength modulations incommensurate with the atomic lattice are particularly interesting1, exemplified by recent advances in two-dimensional (2D) moiré materials2,3. Bulk van der Waals (vdW) superlattices4-8 hosting 2D interfaces between minimally disordered layers represent scalable bulk analogues of artificial vdW heterostructures and present a complementary venue to explore incommensurately modulated 2D states. Here we report the bulk vdW superlattice SrTa2S5 realizing an incommensurate one-dimensional (1D) structural modulation of 2D transition metal dichalcogenide (TMD) H-TaS2 layers. High-quality electronic transport in the H-TaS2 layers, evidenced by quantum oscillations, is made anisotropic by the modulation and exhibits commensurability oscillations paralleling lithographically modulated 2D systems9-11. We also find unconventional, clean-limit superconductivity in SrTa2S5 with a pronounced suppression of interlayer relative to intralayer coherence. The in-plane magnetic field dependence of interlayer critical current, together with electron diffraction from the structural modulation, suggests superconductivity12-14 in SrTa2S5 is spatially modulated and mismatched between adjacent TMD layers. With phenomenology suggestive of pair-density wave superconductivity15-17, SrTa2S5 may present a pathway for microscopic evaluation of this unconventional order18-21. More broadly, SrTa2S5 establishes bulk vdW superlattices as versatile platforms to address long-standing predictions surrounding modulated electronic phases in the form of nanoscale vdW devices12,13 to macroscopic crystals22,23.

Altering the optical, physical, and TL Dosimetric properties of MgSO4:Dy2O3:B2O3 transparent glass ceramic system: Evaluating the impact of roughness control and ZnO inclusion

This research examines the influence of surface roughness and the incorporation of ZnO (0.05–0.20 mol%) on the magnesium sulfate: dysprosium oxide: boron oxide (0.1 < x < 0.5) glass ceramic system for dosimeter applications. The parent glasses were prepared using the melt-quenching technique, with all samples melted at 1350 °C, except for B, which was melted at 700 °C. The crystallization, roughness, and optical properties were further determined using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and UV–Visible Spectrophotometry, respectively. The glass ceramics were exposed to 2.97 mGy of X-ray radiation ten cycles to assess specific dosimetric capabilities. Among the doped samples, MgSO4:Dy2O3-(0.2B2O3:0.05ZnO) exhibited the most promising performance as a dosimeter. Notably, the Thermoluminescence Dosimetry (TLD) readings of the pre- and post-polished 0.2MDB were 1041.96 nC and 1278.84 nC, respectively, with roughness values of 1.83 nm and 54.7 nm. Similarly, the TLD readings of the pre- and post-polished 0.05MDBZ were 1888.33 nC and 3262.63 nC, respectively, with roughness values of 17.3 nm and 19.8 nm. This work highlights that surface roughness significantly enhances trapping efficiency, underscoring the importance of dosimeter polishing as a beneficial step in enhancing their performance.

Poly(ester amide) from 6‐amino‐1‐hexanol and terephthalic acid: preparation and properties

AbstractPoly(ester amide)s (PEAs) have received extensive attention due to their unique chemical structure and excellent properties. In this paper, a novel PEA (P6T6T) was prepared through melt polycondensation of terephthalic acid (PTA) and 6T6‐diamide‐diol (6T6), which was from the amidation of 6‐amino‐1‐hexanol and PTA. The structures were characterized by nuclear magnetic resonance, fourier transform infrared, and wide‐angle X‐Ray diffraction, and the thermal properties were evaluated by differential scanning calorimetry and thermal gravimetric analysis for P6T6T. It was found that the melting point of P6T6T was 217°C, which was about 37°C lower than that of PET (254°C), while the initial decomposition temperature was maintained at about 381°C. P6T6T had a fast crystallization rate (the half time of crystallization (t1/2) range from 35 to 60 s) and great crystallization properties. The saturated water absorption of the P6T6T was measured to be 2.53 wt%, which was three times that of PET (0.83 wt%). Furthermore, the water contact angle of P6T6T was determined to be 57.3°C, much lower than that of PET (94.7°C). All these results suggest that the incorporation of amide was an efficient method to improve the water absorption of polyester fibers.

Exploring crystal structure-physical property relationships with pressure.

From its conception, X-ray crystallography has provided a unique understanding of the structure, bonding and electronic state of materials, which, in turn, unlocks a means of examining the properties and function of crystalline systems. Using state-of-the-art single-crystal X-ray diffraction, along with UV-Vis spectroscopy and DFT calculations, Zwolenik et al. [(2024). IUCrJ, 11, 519-527] have provided a comprehensive study of the structure-optical property relationship of 1,3-diacetylpyrene with methodologies that are increasingly accessible to non-specialist laboratories.

Enzymatic conversion of camellia seed oil into glycerol esters: Synthesis and characterization

AbstractThe conversion of triacylglycerols in edible oils into diacylglycerols (DAGs) is of great significance for obtaining products with health benefits. Camellia seed oil (C‐oil), which is rich in oleic acid and linoleic acid, is an excellent raw material for the production of DAGs. In this study, single factor optimization experiments were carried out for hydrolysis and esterification respectively. Using Lipozyme® RM IM as catalyst, the maximum percent of C‐oil hydrolysis reached 87.14% at the reaction temperature of 60°C, reaction time of 24 h, water content of 30% and enzyme addition amount of 4%. The maximum content of camellia seed oil diacylglycerol (C‐DAG) reached 62.49% under the conditions of Lipozyme® RM IM as catalyst, vacuum system, 3% enzyme addition, 2% water addition, reaction temperature of 50°C and substrate molar ratio of free fatty acid to glycerol of 1:1. The high content of DAG was obtained by a coupled method, which eliminated the purification steps and reduced production costs. C‐oil and C‐DAG have been characterized by GC, TG, DSC, and GC‐IMS. Our results showed that the enzymatic coupling method did not affect the structural of the substances, but did affect the crystallization and melting properties of the oils. Moreover, the taste of C‐DAG was more delicate than C‐oil. Finally, the reaction mechanism was analyzed using FTIR spectroscopy, revealing that C‐oil was primarily hydrolyzed into free fatty acids. C‐DAG exhibited ester C‐O stretching vibrations in the range 1280–1030 cm−1, indicating successful esterification reaction between camellia seed oil free fatty acids (C‐FFAs) and glycerol catalyzed by lipases.

Eu2+/Eu3+ co-activated Ba2La8(SiO4)6O2 phosphors for optical thermometry

The Eu2+/Eu3+ co-doped Ba2La8(SiO4)6O2 phosphors were synthesized via the high-temperature solid-state reaction method. The crystal structure and electronic properties of Ba2La8(SiO4)6O2 were investigated. Furthermore, a systematic study was conducted on the photoluminescence characteristics of Ba2La8(SiO4)6O2: Eu(2+, 3+) as well as the potential energy transfer mechanism from Eu2+ to Eu3+. Temperature sensing can be achieved through two methods, either monitoring the emission intensity of the phosphor or utilizing the fluorescence intensity ratio technique. The investigation results suggest that the synthesized phosphor exhibits promising potential as a luminescent thermometer.

Crystallization Behavior and Mechanical Property of Biodegradable Poly(butylene succinate-co-2-methyl succinate)/Cellulose Nanocrystals Composites.

Biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS)/cellulose nanocrystals (CNC) composites were successfully prepared at low CNC loadings with the aims of improving crystallization and mechanical properties and extending the practical application of PBSMS. CNC is finely dispersed in the PBSMS matrix without obvious aggregations. The low content of CNC obviously promoted the crystallization behavior of PBSMS under different conditions. The spherulitic morphology study revealed that CNC, as an effective heterogeneous nucleating agent, provided more nucleation sites during the melt crystallization process. In addition, the nucleation effect of CNC was quantitatively evaluated by the following two parameters, i.e., nucleation activity and nucleation efficiency. The crystal structure and crystallization mechanism of PBSMS remained unchanged in the composites. In addition, as a reinforcing nanofiller, CNC significantly increased Young's modulus and the yield strength of PBSMS. The crystallization behavior and mechanical properties of PBSMS were significantly improved by the low content of CNC, which should be interesting and essential from the perspective of biodegradable polymer composites.

Deep-Ultraviolet Bialkali-Rare Earth Metal Anhydrous Sulfate Birefringent Crystal.

Birefringence is an important linear optical property of anisotropic crystals that plays a significant role in regulating light polarization. A new bialkali-rare earth metal sulfate, NaRbY2(SO4)4 compound, consisting of non-π-conjugated alkali metals and rare earth metal-centered dodecahedral YO8 has been synthesized. The structure analysis suggests that the three-dimensional (3D) structure of the compound is found to be attributable to the combination of dodecahedral YO8 and tetrahedral SO4 groups with Na+ and Rb+ located in the cavities. The ultraviolet, visible, and near-infrared (UV-vis-NIR) spectra reveal that the compound exhibits transparency at a wavelength of less than 200 nm. The observed birefringence of the compound is 0.045@550 nm, which is comparatively larger than that of most deep-ultraviolet (DUV) birefringent crystals. The birefringence mainly originated from the YO8 dodecahedron, which is suggested by first-principles calculations. This research work can provide a useful perspective to explore new DUV sulfates with excellent birefringence.

Hydrophilicity and Pore Structure Enhancement in Polyurethane/Silk Protein-Bismuth Halide Oxide Composite Films for Photocatalytic Degradation of Dye.

Polyurethane/silk protein-bismuth halide oxide composite films were fabricated using a blending-wet phase transformationin situsynthesis method. The crystal structure, micromorphology, and optical properties were conducted using XRD, SEM, and UV-Vis DRS characterize techniques. The results indicated that loaded silk protein enhanced the hydrophilicity and pore structure of the polyurethane composite films. The active species BiOX were observed to grow as nanosheets with high dispersion on the internal skeleton and silk protein surface of the polyurethane-silk protein film. The photocatalytic efficiency of BiOX/PU-SF composite films was assessed through the degradation of Rhodamine B under visible light irradiation. Among the tested films, the BiOBr/PU-SF composite exhibited the highest removal rate of RhB at 98.9%, surpassing the removal rates of 93.7% for the BiOCl/PU-SF composite and 85.6% for the BiOI/PU-SF composite. Furthermore, an active species capture test indicated that superoxide radical (•O2-) and hole (h+) species played a predominant role in the photodegradation process.

A Fluorescent Organic Probe for Naked-Eye Detection of Chloromethanes.

An organic fluorescent probe (OFP-TAR) with a propeller-like structure was designed and synthesized. The photoluminescence of OFP-TAR in solution exhibited a significant red shift with the increase of solvent polarity, enabling a transition of fluorescence emission from blue (445 nm) to yellow (540 nm). The organic thin-film materials based on OFP-TAR/PMMA exhibit significant color changes upon exposure to CH2Cl2, CHCl3, and CCl4, with their maximum fluorescence wavelengths measured at 445, 471, and 494 nm respectively. The device facilitates the visual detection of chloromethanes and is capable of enduring more than 7 cycles of testing. These materials can also be prepared as binary-coded microarray data storage devices or applied in the field of anti-counterfeiting. The quantum yields of guest-loaded crystals CH2Cl2@OFP-TAR, CHCl3@OFP-TAR and CCl4@OFP-TAR are observed as 19.13%, 8.79%, and 0.83% respectively, which are consistent with the tendency of OFP-TAR in CH2Cl2 (47.30%), CHCl3 (34.27%) and CCl4 (3.10%). The fluorescence properties of OFP-TAR, OFP-TAR/PMMA, guest-loaded and guest-free crystals provided insights into the special response mechanism of OFP-TAR towards different chloromethanes.

Probing the Band Splitting near the Γ Point in the van der Waals Magnetic Semiconductor CrSBr.

This study investigates the electronic band structure of chromium sulfur bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis on the PL data robustly unveils energy splittings, band gaps, and excitonic transitions across different thicknesses of CrSBr, from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal splitting in both the conduction and valence bands but also highlight a significant advance in our understanding of the interplay between the optical, electronic, and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals.

Morphology and Microstructural Optimization of Zeolite Crystals Utilizing Polymer Growth Modifiers for Enhanced Catalytic Application

Rationally controlling the morphology and microstructure of the zeolite crystals could play a significant role in optimizing their physicochemical properties and catalytic performances for application in various zeolite-based heterogeneous catalysis processes. Among different controlling strategies, the utilization of zeolite growth modifiers (ZGMs), which are molecules capable of altering the anisotropic rates of crystal growth, is becoming a promising approach to modulate the morphology and microstructural characteristics of zeolite crystals. In this mini-review, we attempt to provide an organized overview of the recent progress in the usage of several easily available polymer-based growth modifiers in the synthesis of some commonly used microporous zeolites and to reveal their roles in controlling the morphology and various physicochemical properties of zeolite crystals during hydrothermal synthesis processes. This review is expected to provide some guidance for deeply understanding the modulation mechanisms of polymer-based zeolite growth modifiers and for appropriately utilizing such a modulation strategy to achieve precise control of the morphology and microstructure of zeolite crystals that display optimal performance in the target catalytic reactions.

Ferroelastic Control of the Multicolor Emission from a Triply Doped Organic Crystal.

Emission from crystalline organic solids is often quenched by nonemissive energy-transfer deexcitation processes. While dispersion of fluorophores in polymers or other hosts has been used to enhance the emission intensity, this strategy results in randomization of guest orientation and optical losses at grain boundaries. Here, we report the doping of inherently nonemissive single crystals of anilinium bromide with three fluorescent organic molecules. The doping process equips the crystal with emission characteristics that tune from blue to deep orange. The emission intensity can be reversibly modulated by ferroelastic twinning, which causes the material to function as a multiemissive force sensor. This approach opens up new pathways in the manipulation of emissive properties in organic crystals and may have substantial implications for optoelectronic devices and sensors.

Dynamic Dipole Moment of Luminescent Liquid Crystals Enabled Highly Efficient Active Waveguide Materials Design and Synthesis

AbstractOrganic optical waveguide materials have attracted considerable attention for their promising applications in photonic and optoelectronic devices. However, for most materials, excellent light‐loss properties at high temperature cannot be obtained due to many factors. Consequently, realizing efficient optical waveguide materials that perform well at elevated temperatures remains a significant challenge. In this study, relying on the luminescent properties and self‐assembly properties of luminescent liquid crystals (LLCs), successfully fabricated materials are present for highly efficient active optical waveguides. A systematically synthesized set of LLCs with different structures is named according to the substituent type and the position of the cyano group, namely α‐DECN, α‐DEEOCN, β‐DECN, and β‐DEEOCN. Notably, α‐DECN and β‐DECN reveal hexagonal columnar phase, while α‐DEEOCN and β‐DEEOCN exhibit smectic phase. Optical waveguide experiments have revealed that the obtained LLCs showed highly efficient optical waveguide behavior, where the lowest light loss reached 0.15 dB mm−1 at room temperature. Remarkably, these LLCs show even lower light loss at high temperatures, with the light loss reaching 0.11 dB mm−1 as the lowest point. Further experimental results indicate that this phenomenon is attributed to the change in the dipole moment of these molecules. This research forms a significant groundwork for advanced exploration in optical waveguide material.

Crystal structure, properties and pressure-induced insulator-metal transition in layered kagome chalcogenides

Layered materials with kagome lattice have attracted a lot of attention due to the presence of nontrivial topological bands and correlated electronic states with tunability. In this work, we investigate a unique van der Waals (vdW) material system, A 2 M 3 X 4 (A = K, Rb, Cs; M = Ni, Pd; X = S, Se), where transition metal kagome lattices, chalcogen honeycomb lattices and alkali metal triangular lattices coexist simultaneously. A notable feature of this material is that each Ni/Pd atom is positioned in the center of four chalcogen atoms, forming a local square-planar environment. This crystal field environment results in a low spin state S= 0 of Ni2+/Pd2+. A systematic study of the crystal growth, crystal structure, magnetic and transport properties of two representative compounds, Rb2Ni3S4 and Cs2Ni3Se4, has been carried out on powder and single crystal samples. Both compounds exhibit nonmagnetic p-type semiconducting behavior, closely related to the particular chemical environment of Ni2+ ions and the alkali metal intercalated vdW structure. Additionally, Cs2Ni3Se4 undergoes an insulator-metal transition (IMT) in transport measurements under pressure up to 87.1 GPa without any structural phase transition, while Rb2Ni3S4 shows the tendency to be metalized.

Peroxymonosulfate-activated photocatalytic degradation of norfloxacin via a dual Z-scheme g-C3N5/BiVO4/CoFe − LDH heterojunction: Operation and mechanistic insights

The design of novel dual Z-scheme heterojunction plays a significant path in eradicating organic contaminants via enriched charge carrier separation. Herein, a wet chemical method was used to synthesize ternary g-C3N5/BiVO4/CoFe–LDH (CBCF) nanocomposites, and their corresponding abilities were characterized as follows: crystal phases, optical properties, surface morphologies, and compositions. The g-C3N5/BiVO4/CoFe–LDH-30% (CBCF-3) sample optimized the removal efficiency of norfloxacin (NOR) by up to 95.3% through peroxymonosulfate (PMS) activation in a visible light medium. The combined effects from the Vis/PMS/CBCF-3 catalytic system led to 7-times higher degradation efficiency than visible light only system. This improved performance was attributed to the generation of reactive radical species because of higher PMS utilization and an effective Z-charge transfer process from well-oriented band structures. Moreover, scavenging tests and electron spin resonance analysis revealed the production of active radical and non-radical species, namely •OH, SO4•−, •O2−, and 1O2. Based on the appropriate experimental analysis, the expected NOR degradation mechanism and possible pathways were proposed. Then, the toxicity evaluation results revealed that the intermediate products may not have an adverse effect on the aquatic ecosystems. This research study provides a positive outcome for wastewater remediation using enriched dual Z-scheme mechanism.

Predicting the Color Polymorphism of ROY from a Time-Dependent Optimally Tuned Screened Range-Separated Hybrid Functional.

Polymorphism is a well-known property of molecular crystals, which allows the same molecule to form solids with several crystalline structures that can differ significantly in physical properties. Polymorphs that possess different optical absorption properties in the visible range may exhibit different perceived colors, a phenomenon known as color polymorphism. One striking example of color polymorphism is given by 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, known as ROY for its red-orange-yellow colors. First-principles prediction of color polymorphism may help in polymorph assignment and design but has proven to be challenging. Here, we predict the absorption spectra and simulate the colors of 12 ROY polymorphs using the general, nonempirical method of time-dependent (TD) optimally tuned screened range-separated hybrid (OT-SRSH) functional. For 5 ROY polymorphs with known experimental absorption spectra, we show that the TD-OT-SRSH approach predicts absorption spectra in quantitative agreement with experiment. For all polymorphs, we show that an accurate simulation of the colors is obtained, paving the way to a fully predictive, low-cost calculation of color polymorphism.