Crystalline Materials Research Articles

Investigating the zeolite performance in soil and water conservation after prescribed fires in degraded rangelands

Since the last decades, soil erosion and wildfires are significant threats to most societies and results in the loss of fertile layers and, consequently, in productivity. Changes in soil moisture and stability of soil grains, both in the short- and long-terms after a wildfire occurs, should be also considered as a parameter because they play a key role in plant growth and nutrition too. Adding conditioners to soil also helps to reduce runoff and nutrient losses, which is necessary for the sustainable use of water and ecosystem services. Therefore, the current research was conducted to assess the impacts of zeolite (microporous, crystalline aluminosilicate material commonly applied as commercial adsorbent and catalysts) conservation treatment with diverse amounts (0, 250, 500 and 750 g m−2; Z0 Z1, Z2 and Z3, respectively) on changes of runoff and sediment yield in burned soils with different amounts (250, 500, 750 and 1000 g m−2; F1, F2, F3 and F4, respectively) under laboratory conditions. The experiments were conducted using rainfall simulations with an intensity of 50 mm h−1. The results showed that the highest changes percent of time to runoff (s), runoff volume (l), and soil loss (g) variables after zeolite application at different rates of fire was observed in F4Z3 treatment with 114.94, 76.61 and 82.60 %, respectively. We conclude that these results can be useful for a better understanding of the relationships between the fire effects on runoff and sediment considering innovative application of control measures nin-tested to date.

Manipulating cationic ordering toward highly efficient and zero-thermal-quenching cyan photoluminescence

Developing effective design principle in crystalline materials for superior optical properties remains a critical challenge. Herein, we establish the cationic ordering strategy to build rigid framework and significantly improve phosphor performance. As a proof of concept, the NaHf2-xYx(PO4)3:Eu2+ (x = 0.05–0.2) phosphor series is constructed, which possesses absolutely cationic ordered structure and the linked outstanding photoluminescent properties. Structurally, heterovalent substitution in the lattice maintains the single-site occupancy of Na+ ions in NaHf2-xYx(PO4)3:Eu2+, as confirmed by Rietveld refinements and NMR spectroscopy. This cationic arrangement keeps the cation/vacancy ordered distribution that ensures high structural rigidity, with Debye temperature, as the indicator of rigidity, extracted from low temperature heat capacities exceeding 379 K. The resultant high structural rigidity, coupled with intrinsic defects, induces zero-thermal-quenching luminescence up to 150 °C. Moreover, the substitution of Y3+ at Hf4+ site facilitates effective Eu3+ to Eu2+ reduction, making them excellent cyan emitters with quantum efficiency exceeding 90 % and intense violet absorption. This work provides an impetus for the discovery of the currently state-of-the-art cyan phosphors for practical applications and gives insight into the structural factors influencing luminescent properties.

In-Situ Observation of DL-Alanine Crystallization from a Laser-Trapped Dense Liquid Droplet as a Heterogeneous Nucleation Site

Abstract Nucleation from an aqueous solution is an important step in crystallization which controls the physicochemical properties of crystalline materials. Although dense liquid droplets are considered as a precursor of a crystal in the two-step nucleation model, their actual role is unclear. Our in-situ microscopic observations of the crystallization of DL-alanine from a dense liquid droplet trapped by laser tweezers show that the liquid droplets play the role of a substrate facilitating heterogeneous nucleation rather than a precursor of a crystal.

Coordination assembly and NIR photothermal conversion of Metal-organic framework based on 5-(2-cyanophenoxy) isophthalic acid

The development of new photothermal conversion materials in the field of metal-organic frameworks (MOFs) shows broad prospects, but their design synthesis and proper mechanism analysis are still full of huge challenge. Here, four novel MOFs were constructed with 5-(2-cyanophenoxy) isophthalic acid, {Ni(2-CB-IPA)(bpp)(H2O)}n (1), {Ni2(2-CB-IPA)2(bpa)2(H2O)2}n (2), {Co(2-CB-IPA)(bpp)}n (3), {Mn2(2-CB-IPA)2 (bpp)(H2O)2}n (4). (Where 2-CB-IPA = 5-(2-cyanophenoxy) isophthalic acid, bpa = 1,2-bis(4-pyridine)-ethane; and bpp = 1,3-bis(4-pyridyl)propane). The absorption peak at 730 nm in the near-infrared region indicates that different charge transfer interactions affect the photothermal conversion ability. Under laser irradiation (730 nm, 0.45 W cm−2), such compounds exhibit different and distinct warming processes (1 from 20.8 to 91.8 °C; 2 from 20.1 °C to 86.2 °C; 3 from 20.6 to 77.1 °C) except for compound 4. The excellent crystallinity of these materials after irradiation demonstrates excellent thermal stability and cycling durability. Subsequently, further research on the structure-activity relationship revealed that strong π - π interactions are also the reason for the excellent performance of NIR photothermal conversion of 1 under the premise of high NIR absorption. This work provides a visual platform for the photothermal phenomena of crystalline materials.

Application of laboratory micro X-ray fluorescence devices for X-ray topography

It is demonstrated that high-resolution energy-dispersive X-ray fluorescence mapping devices based on a micro-focused beam are not restricted to high-speed analyses of element distributions or to the detection of different grains, twins and subgrains in crystalline materials but can also be used for the detection of dislocations in high-quality single crystals. Si single crystals with low dislocation densities were selected as model materials to visualize the position of dislocations by the spatially resolved measurement of Bragg-peak intensity fluctuations. These originate from the most distorted planes caused by the stress fields of dislocations. The results obtained by this approach are compared with laboratory-based Lang X-ray topographs. The presented methodology yields comparable results and it is of particular interest in the field of crystal growth, where fast chemical and microstructural characterization feedback loops are indispensable for short and efficient development times. The beam divergence was reduced via an aperture management system to facilitate the visualization of dislocations for virtually as-grown, non-polished and non-planar samples with a very pronounced surface profile.

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems.

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

Fragment Orbitals Extracted from First-Principles Plane-Wave Calculations.

Decomposing extended structures into smaller, molecular, even functional groups or simple fragments has a long tradition in chemistry because it allows for understanding certain electronic peculiarities in truly chemical terms. By doing so, invaluable property information is chemically accessible, for example, needed to rationalize catalytic or magnetic or optical nature. In order to also follow that train of thought for periodic materials, we have developed a tool which in a straightforward manner derives fragment molecular orbitals from plane-wave electronic-structure data of whatever kind of solid-state material. We here report on the mathematical apparatus of the method dubbed linear combination of fragment orbitals (LCFO) used for that purpose, implemented within the LOBSTER code. The method is illustrated from various sorts of molecular entities contained in such crystalline materials, together with an assessment of both accuracy and robustness of the new tool.

Solvent-Responsive Nonporous Adaptive Crystals Derived from Pyridinium Hydrochloride and the Application in Iodine Adsorption.

Nonporous adaptive crystals (NACs) are crystalline nonporous materials that can undergo a structural adaptive phase transformation to accommodate specific guest via porous cavity or lattice voids. Most of the NACs are based on pillararenes because of their flexible backbone and intrinsic porous structure. Here we report a readily prepared organic hydrochloride of 4-(4-(diphenylamino)phenyl)pyridin-1-ium chloride (TPAPyH), exhibiting the solvent dimension-dependent adaptive crystallinity. Wherein it forms a nonporous α crystal in a solvent with larger dimensions, while forming two porous β and γ crystals capable of accommodating solvent molecules in solvent with small size. Furthermore, the thermal-induced single-crystal-to-single-crystal (SCSC) transition from the β to α phase can be initiated. Upon exposure to iodine vapor or immersion in aqueous solution, the nonporous α phase transforms to porous β phase by adsorbing iodine molecules. Owing to the formation of trihalide anion I2Cl- within the crystal cavity, TPAPyH exhibits remarkable performance in iodine storage, with a high uptaking capacity of 1.27 g·g-1 and elevated iodine desorption temperature of up to 110 and 82°C following the first and second adsorption stage. The unexpected adaptivity of TPAPyH inspired the design of NACs for selective adsorption and separation of volatile compound from organic small molecules. This article is protected by copyright. All rights reserved.

Properties and Microstructure of a Cement-Based Capillary Crystalline Waterproofing Grouting Material

Cement grout is traditionally used for treating water leakage distress in tunnels. However, traditional cement grout has the disadvantages of a poor anti-seepage performance, long setting time, and slow strength gain. To this end, a high-performance cement-based capillary crystalline waterproofing (CCCW) grouting material was synthesized using cement, capillary crystalline material, and several admixtures. The influences of the material proportions on the viscosity, bleeding rate, and setting time of the fresh grout, as well as the permeability coefficient of the grouted aggregate and the unconfined compression strength of the hardened grout material, were systematically studied. The mineralogy and microstructure of the CCCW grouting material were examined using X-ray diffraction, industrial computed tomography, and scanning electron microscopy. The results indicated that the capillary crystalline material PNC803 was not suitable for mixing with bentonite, sodium chloride, and triethanolamine in cementitious slurries, but it can produce excellent synergistic effects with sulfate, calcium chloride, and triisopropanolamine. An analysis of the microstructure of the CCCW grouting material showed that the PNC803 and additives can promote the hydration of cement, which yields more hydration products, sealing water passage and filling micro voids and therefore leading to enhanced waterproofing and strengthening effects. These research results could improve the applicability of CCCW material in tunnel engineering.

Tuning the Optical and Photoelectrochemical Properties of Epitaxial BiVO4 by Lattice Strain

State‐of‐the‐art photoelectrodes in highly efficient photoelectrochemical (PEC) systems often comprise multilayer architectures where lattice mismatch‐imposed strain at the interfaces can perturb the material's crystalline lattice and electronic structure. Despite its inevitable presence, understanding of strain effects in semiconductor photoelectrodes is lacking, preventing rational exploitation of strain engineering to improve photoelectrode performance. In this work, we combine X‐ray structural characterization with strain tensor decomposition analysis as well as optical/photocurrent spectroscopic methods to demonstrate how volumetric lattice deformations caused by substrate‐imposed hydrostatic strain impact the optoelectronic and PEC properties of BiVO4. Utilizing single‐crystalline, epitaxial BiVO4/indium tin oxide (ITO)/yttrium‐stabilized zirconia (YSZx, x = 8% and 13% mol Y2O3) photoelectrodes as a model platform, we find that tensile hydrostatic strain that causes volumetric lattice dilation in BiVO4 results in slightly enhanced optical absorption, but it is detrimental to the internal quantum efficiencies in BiVO4. We attribute this to localization of photogenerated charge carriers, thereby leading to poor charge separation in the bulk of BiVO4 and increased recombination losses. Finally, we highlight the beneficial effects of compressive hydrostatic strain on enhancing the internal quantum efficiencies in BiVO4. Our results provide a basis for exploiting epitaxial strain engineering to optimize the performance of multilayer photoelectrodes in PEC systems.

Unveiling the Multielectron Acceptor Properties of π-Expanded Pyracylene: Reversible Boat to Chair Conversion.

In this work, the chemical reduction of a hybrid pyracylene-hexa-peri-hexabenzocoronene (HPH) nanographene was investigated with different alkali metals (Na, K, Rb) to reveal its remarkable multielectron acceptor abilities. The UV-vis and 1H NMR spectroscopy monitoring of the stepwise reduction reactions supports the existence of all intermediate reduction states up to the hexaanion for HPH. Tuning the experimental conditions enabled the synthesis of the HPH anions with gradually increasing reduction states (up to -5) isolated with different alkali metal ions as crystalline materials. The single-crystal X-ray diffraction structure analysis demonstrates that the highly negatively charged HPH anions (-4 and -5) exhibit a drastic geometry change from boat-shaped (observed in the neutral parent, mono- and dianions) to a chair conformation, which was proved to be fully reversible by NMR spectroscopy. DFT calculations show that this geometry change is induced by an enhanced interaction between the coordinated metal ions and negatively charged HPH core in the chair conformation.

Enhancing the Analysis of Eu3+ Photoluminescence in Coordination Compounds in the Solid State by Determining their Refractive Index

AbstractThis study is focused on determining the refractive index as a crucial parameter for evaluating the intrinsic quantum yield and the ligand sensitisation efficiency in solid‐state trivalent lanthanide coordination compounds. For this, eight trivalent europium complexes with phenyl‐terpyridine ([EuX3(ptpy)(L)], X=Cl− or NO3−, ptpy=4′‐phenyl‐2,2′ : 6′,2′′‐terpyridine, L=H2O or other molecules) were examined. Their refractive indices were determined using the Becke lines test by immersing transparent material in a series of media with known refractive indices. Using the set of media presented here, determining crystalline materials′ refractive indices from 1.41 to 1.73 with a step of 0.01 is possible. Assessment of the refractive indices of the complexes mentioned above allowed a comprehensive analysis of their photophysical properties in the solid state. Moreover, this method can be extrapolated for other solid‐state materials, offering valuable insights in the broader field of photophysics. In addition to photoluminescence investigations, the compounds presented were characterised by single‐crystal X‐ray diffraction (SCXRD), powder X‐ray diffraction (PXRD), Hirschfeld surface area analysis, UV‐Vis reflectance spectroscopy, hydrolysis sensitivity analysis, and simultaneous thermogravimetry and differential thermal analysis coupled with mass‐spectrometry (STA‐MS).

MgHg(SeO3)2(H2O)2: A magnesium mercury selenite with large birefringence

Selenite crystalline materials have been popular owing to the diverse structures and optical performances. A new mercury selenite, MgHg(SeO3)2(H2O)2, was synthesized by using a conventional hydrothermal method. It crystallizes in the monoclinic structure with a C2/c space group, MgHg(SeO3)2(H2O)2 exhibits a three-dimensional (3D) structure, which is made up of [Hg(SeO3)2]2–∞ chains and distorted MgO4(H2O)2 octahedra. Besides, it presents a large birefringence of 0.137 @ 546 nm according to experimental measurement. Synthesis, crystal structure, thermal stability, optical property measurements and theoretical studies were performed in this work.

Thickness-Driven Synthesis and Applications of Covalent Organic Framework Nanosheets.

Covalent organic frameworks (COFs) are two-dimensional, crystalline porous framework materials with numerous scopes of tunability like porosity, functionality, stability and aspect ratio (thickness to length ratio). The manipulation of π-stacking in COFs results in truly 2D materials, namely covalent organic nanosheets (CONs) adds advantages in many applications. In this review, we have discussed both top-down (COFs→CONs) and bottom-up (molecules→CONs) with precise information on thickness and lateral growth. We have showcased the research progress of CONs in few selected applications like batteries, catalysis, sensing and biomedical applications. This review specifically highlights the reports where the authors compare the performance of CONs with COFs by demonstrating the impact of thickness and lateral growth of the nanosheets. Eventually, we have provided the possible scope of exploration of CONs research in terms of inter-dimensional conversion like graphene to carbon nanotube and future technologies..

Thickness‐Driven Synthesis and Applications of Covalent Organic Framework Nanosheets

Covalent organic frameworks (COFs) are two‐dimensional, crystalline porous framework materials with numerous scopes of tunability like porosity, functionality, stability and aspect ratio (thickness to length ratio). The manipulation of π‐stacking in COFs results in truly 2D materials, namely covalent organic nanosheets (CONs) adds advantages in many applications. In this review, we have discussed both top‐down (COFs→CONs) and bottom‐up (molecules→CONs) with precise information on thickness and lateral growth. We have showcased the research progress of CONs in few selected applications like batteries, catalysis, sensing and biomedical applications. This review specifically highlights the reports where the authors compare the performance of CONs with COFs by demonstrating the impact of thickness and lateral growth of the nanosheets. Eventually, we have provided the possible scope of exploration of CONs research in terms of inter‐dimensional conversion like graphene to carbon nanotube and future technologies..

Large quantum anomalous Hall effect in spin-orbit proximitized rhombohedral graphene

The quantum anomalous Hall effect (QAHE) is a robust topological phenomenon that features quantized Hall resistance at zero magnetic field. We report the QAHE in a rhombohedral pentalayer graphene-monolayer tungsten disulfide (WS 2 ) heterostructure. Distinct from other experimentally confirmed QAHE systems, this system has neither magnetic element nor moiré superlattice effect. The QAH states emerge at charge neutrality and feature Chern numbers C = ±5 at temperatures of up to about 1.5 kelvin. This large QAHE arises from the synergy of the electron correlation in intrinsic flat bands of pentalayer graphene, the gate-tuning effect, and the proximity-induced Ising spin-orbit coupling. Our experiment demonstrates the potential of crystalline two-dimensional materials for intertwined electron correlation and band topology physics and may enable a route for engineering chiral Majorana edge states.

Catalog of topological phonon materials

Phonons play a crucial role in many properties of solid-state systems, and it is expected that topological phonons may lead to rich and unconventional physics. On the basis of the existing phonon materials databases, we have compiled a catalog of topological phonon bands for more than 10,000 three-dimensional crystalline materials. Using topological quantum chemistry, we calculated the band representations, compatibility relations, and band topologies of each isolated set of phonon bands for the materials in the phonon databases. Additionally, we calculated the real-space invariants for all the topologically trivial bands and classified them as atomic or obstructed atomic bands. We have selected more than 1000 “ideal” nontrivial phonon materials to motivate future experiments. The datasets were used to build the Topological Phonon Database.

Cryo-EM combined with image deconvolution to determine ZIF-8 crystal structure

Abstract Metal-organic frameworks (MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1, 2] It is challenging to visualize MOFs with transmission electron microscopy (TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy (cryo-EM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7 Å and enhancing its critical electron dose to around 20 e-/Å2. In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images is modulated by contrast transfer function (CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.

Synthesis of Stable 2D Conductive Lanthanide Organic Frameworks (Lu‐HHTP) for High‐Performance Humidity Sensors

Two‐dimensional conductive metal‐organic frameworks (MOFs) featuring structural diversity and high porosity represent promising platforms for chemiresistive humidity sensing. The precise control of the structure of lanthanide‐based MOFs and an exploration of its impact on charge transport and sensing applications have consistently been focal points for researchers. In this study, we present the synthesis and characterization of Lu‐HHTP (HHTP = 2,3,6,7,10,11‐hexahydroxytriphenylene) as highly crystalline and conductive porous materials. The polymeric framework of Lu‐HHTP encompasses 1D hexagonal channels and exhibits interlayer π‐π stacking, resulting in a material with a high surface area and uniform rod‐like microstructure. Benefiting from its elevated electrical conductivity, the Lu‐HHTP‐based humidity sensor exhibited commendable sensing properties within the relative humidity range of 33% to 95% at room temperature (25°C), achieving a response value as high as 19 at 95% relative humidity. Furthermore, the sensor displayed superior repeatability, characterized by rapid response and recovery speeds in the presence of moisture. These findings indicate that Lu‐HHTP holds substantial promise as a material for humidity sensors.

Photochemical and Patternable Synthesis of 2D Covalent Organic Framework Thin Film Using Dynamic Liquid/Solid Interface.

2D covalent organic frameworks (COFs) are highly porous crystalline materials with promising applications in organic electronics. Current methods involve either on-surface synthesis (solid surface) or interfacial synthesis (liquid/liquid, liquid/gas interface) to create thin films for these applications, each with its drawbacks. On-surface synthesis can lead to contamination from COF powder or unreacted chemicals, while interfacial synthesis risks damaging the film during post-transfer processes. These challenges necessitate the development of alternative synthesis methods for high-quality 2D COF films. This study presents a novel approach for synthesizing homogeneous 2D COF thin films by combining photochemistry and a liquid-flowing system. Leveraging previous work on liquid flow systems to prevent contamination during solvothermal synthesis, this approach to the photochemical method, resulting in the synthesis of high-crystalline 2D COF films with tunable thickness is adopted. The photochemical approach offers spatially controllable energy sources, enabling patternable COF synthesis. Notably, it is successfully fabricated ultrasmooth patterned 2D COF films on hexagonal boron nitride, offering a streamlined process for optoelectronic device fabrication without additional pre, post-processing steps.