H2O Crystals Research Articles

Growth, structure and optical properties of Rb2CоCl4·2H2O crystals

Phase equilibria in the RbCl–CoCl2·2H2O–H2O system were investigated, single crystals of double rubidium–cobalt chloride dihydrate were obtained, and its structure and optical properties were studied. The regions of crystallization of compounds in the three-component system under study were delimited. Rb2CoCl4·2H2O crystals were grown by controlled decrease in the temperature of a saturated aqueous solution. Using X-ray diffraction analysis, the crystal lattice parameters of Rb2CoCl4·2H2O were obtained and the structure of the crystals was refined. The spectral characteristics of the obtained crystals and the corresponding aqueous solution were studied in the λ range 200–800 nm.

Synthesis, structure and characterizations of the first alkali-metal/alkaline-earth-metal oxalatophosphate Na4Mg3(HPO4)4(C2O4)·2H2O

The first alkali-metal/alkaline-earth-metal oxalatophosphate Na4Mg3(HPO4)4(C2O4)·2H2O with monoclinic P21/n space group was successfully synthesized by a conventional solvothermal method. Na4Mg3(HPO4)4(C2O4)·2H2O crystal exhibits a typical three-dimensional structure built by isolated [C2O4] and [HPO4] anionic groups connected by Na and Mg atoms. The HPO42− groups are linked by hydrogen bonds to form an unique one-dimensional zigzag band ∞[HPO4]2-, which exhibits a stable “Mortise-Tenon” structure configuration within the bc plane. Fourier transform infrared (FTIR) spectrum and Raman spectrum confirm the crystal structure of Na4Mg3(HPO4)4(C2O4)·2H2O. UV–visible near infrared (UV–Vis–NIR) diffuse reflectance and band structure calculation indicate that Na4Mg3(HPO4)4(C2O4)·2H2O is an indirect bandgap semiconductor with a bandgap of 4.42 eV. In addition, Na4Mg3(HPO4)4(C2O4)·2H2O shows a moderate birefringence of 0.046 at 550 nm.

In Search of Covalency Measure of Gd(III)-Ligand Interactions.

Experimental electron density distribution of the [C(NH2)3]3[Gd(EDTA)F2]·H2O crystal was determined. The derived experimental and theoretical (DFT) topological parameters such as ∇2ρc, ρc, bond degree (BD), kinetics, and potential energy were used to study the nature of Gd-O, Gd-F, and Gd-N interactions. The natural charge of the Gd is 1.86; the natural configuration of the cation is [Xe]6s0.134f7.105d0.83, and the covalency of the Gd-L bond is mainly connected with the transfer of charge from the spx ligand orbitals onto the 5d orbitals of the Gd cation. Simultaneously, the donation of charge onto the 6s and 4f orbitals occurs to a lesser extent. Moreover it was found that the donation of the ligand charges onto the Gd(III) is larger for compounds with a lower coordination number. The obtained topological parameters were analyzed in the context of the Gd(III) f-f transition properties, i.e., energy of the excited 2S+1LJ states, Judd-Ofelt intensity parameters, and luminescence lifetimes, of 18 Gd(III) compounds with various O, N, and F donor ligands (DOTA, EDTA, CDTA, DTPA, NTA, EGTA, ODA, F-, H2O, and CO32-). The calculated nephelauxetic β parameter may reflect the penetration degree of electron lone pairs of ligands inside the metal basin. Finally, it was found for the first time that the sum of the Gd(III)-L bond energy (∑EGdL) is correlated with the position of the gravity center of the 8S7/2 → 2S+1LJ transitions and increase of covalency of the Gd(III)-L bonds is associated with decrease of their bond energy. The obtained results may shed light on chemical bonding in systems containing f-elements. Such subtle differences in the covalent contribution to the Ln-L or An-L bond may tune the selectivity of the partitioning processes of lanthanides and actinides.

Enantiomer Recognition by the Difference in Adsorption Rates on the Surfaces of Chiral Crystals.

The chirality of biopolymers remains one of the mysteries of Life. For such objects, the phenomenon of supramolecular chirality (SMC) is vital. Enantiomers can be recognized by the adsorption on surfaces with SMC. However, the mechanisms of such chiral recognition are still unknown. In this work, the adsorption kinetics of menthol test enantiomers on the surfaces of γ-glycine and NiSO4•6H2O chiral crystals was studied. It was found that the difference in adsorption was observed in nonequilibrium state more often than in equilibrium. If the enantioselectivity in equilibrium state was observed, the enantioselectivity coefficient α at nonequilibrium conditions was higher. The maximum α in nonequilibrium state was 2.44 for γ-glycine crystals and 2.12 for NiSO4•6H2O crystals. Even if no differences in adsorption were observed under adsorption-desorption equilibrium conditions, a significant enantioselectivity at nonequilibrium conditions was found. This has proved the possibility of chiral recognition on surfaces with SMC by the differences in adsorption rates. Such novel chiral recognition mechanism can provide enhanced enantioselectivity in adsorption, catalysis, chromatographic separation, and chemical sensing.

Adsorption/desorption of H2O and phase transition in crystals of cobalt(II) bis(tolylterpyridine) nitrate

Adsorption/desorption of H2O and phase transition in crystals of cobalt(II) bis(tolylterpyridine) nitrate

High-Efficiency Purification and Morphology Regulation of CaSO4·2H2O Crystals from Phosphogypsum.

Phosphogypsum is a solid waste with great environmental stockpile pressure produced by the wet production of phosphoric acid. Although there are various methods to purify and utilize phosphogypsum, the means for environmentally friendly, low energy consumption, and high value-added utilization still need to be further explored. Here, CaSO4·2H2O crystal was directly purified and regulated from phosphogypsum by using the anti-solvent method. The antisolvent can be adsorbed in the c-axis direction of the crystal and further inhibit the growth rate in this direction, resulting in a change in the morphology of the crystal. By adjusting the polarity and chain length of the anti-solvent, the morphology of CaSO4·2H2O crystal can change from butterfly-like flake crystals to hexagonal prism-like crystals. When n-propanol with long chain was used as the anti-solvent, the morphology of the CaSO4·2H2O crystal showed a hexagonal prism with a specific surface area of 19.98 m2/g and a Cu2+ loading efficiency of 52.67%. The encouraging results open up new possibilities for the application of phosphogypsum.

Microscopic analysis of mechanical anisotropy and damage evolution of 3D printed rock-like samples under uniaxial compressive tests

Three-dimensional printing (3DP) offers valuable insight into the characterization of natural rocks and the verification of theoretical models due to its high reproducibility and accurate replication of complex defects such as cracks and pores. In this study, 3DP gypsum samples with different printing directions were subjected to a series of uniaxial compression tests with in situ micro-computed tomography (micro-CT) scanning to quantitatively investigate their mechanical anisotropic properties and damage evolution characteristics. Based on the two-dimensional (2D) CT images obtained at different scanning steps, a novel void ratio variable was derived using the mean value and variance of CT intensity. Additionally, a constitutive model was formulated incorporating the proposed damage variable, utilizing the void ratio variable. The crack evolution and crack morphology of 3DP gypsum samples were obtained and analyzed using the 3D models reconstructed from the CT images. The results indicate that 3DP gypsum samples exhibit mechanical anisotropic characteristics similar to those found in naturally sedimentary rocks. The mechanical anisotropy is attributed to the bedding planes formed between adjacent layers and pillar-like structures along the printing direction formed by CaSO4·2H2O crystals of needle-like morphology. The mean gray intensity of the voids has a positive linear relationship with the threshold value, while the CT variance and void ratio have concave and convex relationships, respectively. The constitutive model can effectively match the stress–strain curves obtained from uniaxial compression experiments. This study provides comprehensive explanations of the failure modes and anisotropic mechanisms of 3DP gypsum samples, which is important for characterizing and understanding the failure mechanism and microstructural evolution of 3DP rocks when modeling natural rock behavior.

High value-added utilization of desulfurized building gypsum as self-leveling mortar: the comprehensive effect of cement.

The utilization of desulfurized building gypsum as raw material for gypsum-based self-leveling mortar (GSL) is limited by its low strength and poor water resistance. The objective of this study is to enhance comprehensive properties of GSL and prepare qualified desulfurized building gypsum-based self-leveling mortar that can be effectively applied in practical engineering projects. The influence of cement on water consumption rate of initial fluidity (W/M ratio), fluidity, setting time, mechanical strength, and water resistance of GSL were evaluated. Additionally, rheological parameter, heat of hydration, crystal morphology, and pore structure were also analyzed. Cement significantly improved the fluidity of slurry. Moreover, the compressive strength and softening coefficient of GSL reached 20.6MPa and 0.56 at 10% cement, respectively. Furthermore, cement reduced the 30-min-fluidity loss and improved fludity by reducing the yield stress and increasing the plastic viscosity of screed. The transformation of hydration kinetics of GSL could be due to Ca2+ and OH- released by cement, thus resulting in the shortening of initial setting time and the prolongation of the interval between initial and final setting time. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) showed that CSH gel and AFt crystal would generate on the surface of CaSO4·2H2O crystal, making the structure more compact. Mercury intrusion porosimetry (MIP) indicated that cement greatly reduced the porosity through the water reduction effect in the early stage and continuous hydration in the later stage. The continuous hydration of cement also increased the shrinkage rate. This work was expected to provide reference for promoting the application of desulfurized building gypsum as the high value-added screed.

4-Carboxyanilinium dihydrogen phosphate monohydrate, an organophosphate adducts of 4-amino benzoic acid: Structural, vibrational, thermal, and computational studies

4-Carboxyanilinium dihydrogen phosphate monohydrate (4-CAH2PO4·H2O), an organophosphate adduct, was synthesized and characterized by single-crystal X-ray diffraction, Fourier transform infrared (FTIR), Differential scanning calorimetry (DSC) and computational analysis performed using CrystalExplorer 21, Gaussian 09W and Multiwfn 3.7 software. The complex 4-CAH2PO4·H2O crystallized in the triclinic space group, P-1, with two molecules each of 4-carboxyanilinium (4-CA) cations, H2PO4– anions, and water, respectively, in an asymmetric unit. Crystal data for C7H12NO7P: triclinic, space group P-1, a = 8.5238(2) Å, b = 8.9068(2) Å, c = 14.4976(4) Å, α = 106.456(2)°, β = 90.195(2)°, γ = 92.811(2)°, V = 1054.13(5) Å3, Z = 4, T = 293 K, μ(Cu Kα) = 2.587 mm-1, Dcalc = 1.595 g/cm3, 18182 reflections measured (6.358° ≤ 2Θ ≤ 146.396°), 4149 unique (Rint = 0.1018, Rsigma = 0.0521) which were used in all calculations. The final R1 was 0.0584 (I > 2σ(I)) and wR2 was 0.1712 (all data). The organic layer containing 4-CA cations and the inorganic layer containing phosphate anions and water molecules in 4-CAH2PO4·H2O crystals are connected through a three-dimensional network of strong charge-assisted N–H···O and C-OH···O hydrogen bonds. The fingerprint plot of 4-CAH2PO4·H2O obtained indicated that the most prominent interaction corresponds to the short O···H contact, followed by the H···H and H···C contacts. The intermolecular interaction topology of 4-CAH2PO4·H2O has been quantitatively analyzed. The 4-CAH2PO4·H2O complex was optimized by density functional theory (DFT) with B3LYP/6-31G basis set and the theoretical IR vibrational spectra determined. The noncovalent interaction (NCI) and quantum theory of the atom in the molecule (QTAIM) analysis were done using Multiwfn 3.7 software. 4-CAH2PO4·H2O complex structure and its computational analysis are also compared with that of 4-carboxyanilinium dihydrogen phosphate (4-CAH2PO4).

Bipolar membrane crystallization enables near zero-waste production of high-purity oxalic acid crystals

The sodium formate method is currently the predominant route for oxalic acid production but is environmentally harmful. Water splitting in bipolar membranes provides the possibility for clean production of oxalic acid. However, bipolar membrane electrodialysis(BMED) also suffers from the major drawbacks of low concentrations and low purity products. Herein, we propose the use of bipolar membrane crystallization (BMC) to achieve synergistic conversion and crystallization of oxalic acid dihydrate. The dissolution of oxalate in aqueous solution and the electromigration of oxalate through the membrane were precisely tuned under different current densities. The consecutive electromigration of oxalate could boost the dissolution of oxalate. The morphology of the H2C2O4·H2O crystals is related to the current density: a plate-like shape is obtained at 5 mA/cm2, while a needle-shaped crystal is obtained at 10 mA/cm2. The intermittent crystallization of five batches of BMC demonstrated the robustness of bipolar membrane crystallization for the near zero-waste production of oxalic acid.

Bio-sorption capacity of cadmium and zinc by Pseudomonas monteilii with heavy-metal resistance isolated from the compost of pig manure

The tolerance of Pseudomonas monteilii X1, isolated from pig manure compost, to Cd and Zn, as well as its capacity for biosorption, were investigated. The minimum inhibitory concentrations (MIC) of Cd and Zn for the strain were 550 mg/L and 800 mg/L, respectively. Untargeted metabolomics analysis revealed that organic acids and derivatives, lipids and lipid-like molecules, and organic heterocyclic compounds were the main metabolites. The glyoxylate and dicarboxylate metabolism pathway were significantly enriched under Cd2+ stress. The isothermal adsorption and adsorption kinetics experiments determined that the strain had adsorption capacities of 9.96 mg/g for Cd2+ and 23.4 mg/g for Zn2+. Active groups, such as hydroxyl, carboxyl, and amino groups on the cell surface, were found to participate in metal adsorption. The strain was able to convert Zn2+ into Zn3(PO4)2·4H2O crystal. Overall, this study suggested that Pseudomonas monteilii has potential as a remediation material for heavy metals.

Efficient Single-Phase Tunable Dual-Color Luminescence with High Quantum Yield Greater than 100% for Information Encryption and LED Applications.

In modern society, the investigation of highly efficient photoluminescent bulk materials with excitation-induced tunable multicolor luminescence and multiexciton generation (MEG) is of great significance to information security and the application of optoelectronic devices. In this study, two bulk Cu-based halide crystals of (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O, respectively, with one-dimensional structures were grown by a solvent evaporation method. Unexpectedly, (C4H10NO)4Cu2I5·I·H2O displayed excitation-induced tunable dual-color luminescence; one band is a brilliant green-yellow emission centered at 547 nm with a high photoluminescence quantum yield (PLQY) of up to 169.67%, and the other is a red emission at 695 nm with a PLQY of 75.76%. Just as importantly, (C4H10NO)4Cu2Br5·Br exhibits a strong broadband green-yellow emission at 561 nm under broad band excitation ranging from 252 to 350 nm, a long PL decay lifetime of 106.9 μs, and an ultrahigh PLQY of 198.22%. These materials represent the first two examples of 1D bulk crystals and Cu(I)-based halides that have a PLQY exceeding 100%. Combining the unusual luminescence characteristics with theoretical calculations reveals that MEG contributes to the green-yellow emission with ultrahigh PLQY > 100%, and that the red emission can be ascribed to [Cu2I5]3- cluster-centered emission. Additionally, an information encryption method was designed based on the Morse Code. The high luminescence characteristics of LED devices fabricated using the (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O crystals appear to lead to promising applications in solid-state lighting. This work extends the catalog of high-performance luminescent materials and also promotes application prospects of low-dimensional copper-based halides in optoelectronics.

The Birefringence Modulation in Short‐Wave Ultraviolet Sulfates with Functional π‐Conjugated Cations and Polymerized Heteroleptic Tetrahedral Anions

AbstractSulfates with a large bandgap are always promising optical candidates. However, due to insufficient birefringence, their applications are restricted. Here, in terms of this deficiency, two strategies are proposed to rationally modulate the optical anisotropy of sulfates by cations and anions, respectively. For the cation modulation, the [C(NH2)3]Al(SO4)2·6H2O crystal is investigated, which exhibits an unprecedented birefringence (0.098 @ 546 nm) compared with other deep‐ultraviolet transparent sulfates, resulting from the synergy of π‐conjugated [C(NH2)3]+ and non‐π‐conjugated [SO4]2− groups. For the anion modulation, a novel functional group, [S3O6]2−, with a large polarizability anisotropy, is designed. Thus, a new crystal, NaKS3O6, is obtained, which exhibits a large birefringence of 0.130 @ 546 nm with a short ultraviolet absorption cutoff edge of 215 nm. These results confirm the validity of the strategies. Therefore, the strategies play an important role in improving sulfate's birefringence and then promoting their potential applications in advanced optical systems.

Upward vibrational frequency shift due to electron–phonon polar-coupling interaction in C12H17ClN4OS·HCl·H2O crystals

Electron–phonon (e–p) polar-coupling interactions in C12H17ClN4OS·HCl·H2O crystals exhibiting an upward frequency shift with increasing temperature are investigated using terahertz and far-infrared spectroscopies, and the structural condition required for effective e–p polar-coupling interactions in crystals are uncovered. X-ray crystallography and first-principles calculations reveal that the key structure for the e−p polar-coupling interaction is an open cavity near the considered vibration. Based on the temperature-dependent frequency shift proportional to the Bose−Einstein statistical factor, the interaction strength and characteristic frequency of phonons interacting with electrons are determined at 5.3 × 10–3 cm–1 K–1 and 76.6 cm–1, respectively. From the phonon dispersion curves exhibiting LO (longitudinal optical)–TO (transverse optical) splitting, we find that the highest frequency LO phonon participates in the polar-coupling interaction.

Achieving great optical anisotropy with the well-directed alignment of π-conjugated groups due to hydrogen bonds

Looking for novel UV birefringent units with great birefringence and discovering new candidates that are constructed by them have always been a hotspot in the field of optical materials. Here, a new imidazole-based [C3N2H5]2C2O4·H2O crystal is synthesized with a cutoff edge (274 nm). According to achieve the well-directed alignment, the millimeter-sized single crystal [C3N2H5]HC2O4 is obtained and possesses a larger birefringence than [C3N2H5]2C2O4·H2O with a similar band gap. What’s more, the [C3N2H5]HC2O4 crystals can be grown by a simple aqueous solution volatilization method, and the difference in the measured refractive index of [C3N2H5]HC2O4 is 0.119@546 nm which is similar to the birefringence of the famous α-BBO crystal. The birefringence originates from the π-conjugated [C3N2H5] units and [HC2O4] units, which implies [C3N2H5]HC2O4 is promising candidates for exploring UV materials with large birefringence.

Recovery of tungsten from spent selective catalytic reduction catalyst by sulfuric acid precipitation and evaporation crystallization method

AbstractBACKGROUNDSelective catalytic reduction (SCR) can effectively handle NOx from flue gas in coal‐fired power plants. However, as the core part of the SCR method, V2O5–WO3/TiO2 catalyst has a limited operational life in the complex flue gas environment. The recovery of rare metals from spent catalyst would not only bring economic benefits but also solve environmental problems. The process of reducing acid leaching and further roasting‐water leaching could realize the efficient recycling of vanadium, tungsten and titanium.RESULTSAfter reducing acid leaching and roasting‐water leaching to treat spent SCR catalyst, the obtained solution containing tungsten was used as the raw material in this study. The optimal pH value of solution for removal of silicon and aluminum impurities was 9.2–9.5. The best tungsten precipitation conditions were shown as follows: a tungsten concentration of 30 g L−1, a sulfuric acid concentration of 8 mol L−1, reaction temperature of 70 °C and reaction time of 2 h. Under the optimal tungsten precipitation conditions, the tungsten precipitation efficiency can reach 92.53%. Finally, in order to further improve the purity of the crude H2WO4, the crude H2WO4 was fully dissolved in ammonia, followed by filtration and evaporation crystallization to obtain 5(NH4)2O.12WO3.5H2O (APT) crystals with a purity of 93.05 wt%. The crystallization efficiency of APT was 73.37% at 60 °C for 2 h with a rotor speed of 400 rpm.CONCLUSIONThese results indicated that a higher purity of APT crystals can be obtained by the steps of removing silicon and aluminum, precipitation of tungsten by sulfuric acid, ammonia dissolution and evaporation crystallization. © 2023 Society of Chemical Industry (SCI).

Antimony Doping Enabled Photoluminescence Quantum Yield Enhancement in 0D Inorganic Bismuth Halide Crystals.

Owing to the exterior self-trapped excitons (STEs) with adjustable fluorescence beams, low-dimensional ns2-metal halides have recently received considerable attention in solid-state light-emitting applications. However, the photoluminescence (PL) mechanism in metal halides remains a major challenge in achieving high efficiency and controllable PL properties because the excited-state energy of ns2 conformational ions varies inhomogeneously with their coordination environments. Here, a novel zero-dimensional (0D) lead-free bismuth-based Rb3BiCl6·0.5H2O crystal was reported as a pristine crystal to modulate the optical properties. By doping Sb3+ ions with 5s2 electrons into Rb3BiCl6·0.5H2O crystals, bright orange emission at room temperature was obtained with a photoluminescence quantum yield of 39.7%. Optical characterizations and theoretical studies show that the Sb3+ doping can suppress the strong exciton-phonon coupling, optimize the electronic energy band structure, improve the thermal activation energy, soften the structural lattice of the host crystals, deepen the STE states, and ultimately lead to strong photoluminescence. This work manifests a fruitful manipulation in ripening bismuth-based halides with high-efficiency PL properties, and the PL enhancement mechanisms will guide future research in the exploration of emerging luminescent materials.

H2O2(s) and H2O2·2H2O(s) crystals compared with ices: DFT functional assessment and D3 analysis.

The H2O and H2O2 molecules resemble each other in a multitude of ways as has been noted in the literature. Here, we present density functional theory (DFT) calculations for the H2O2(s) and H2O2·2H2O(s) crystals and make selected comparisons with ice polymorphs. The performance of a number of dispersion-corrected density functionals-both self-consistent and a posteriori ones-are assessed, and we give special attention to the D3 correction and its effects. The D3 correction to the lattice energies is large: for H2O2(s) the D3 correction constitutes about 25% of the lattice energy using PBE, much more for RPBE, much less for SCAN, and it primarily arises from non-H-bonded interactions out to about 5 Å.The large D3 corrections to the lattice energies are likely a consequence of several effects: correction for missing dispersion interaction, the ability of D3 to capture and correct various other kinds of limitations built into the underlying DFT functionals, and finally some degree of cell-contraction-induced polarization enhancement. We find that the overall best-performing functionals of the twelve examined are optPBEvdW and RPBE-D3. Comparisons with DFT assessments for ices in the literature show that where the same methods have been used, the assessments largely agree.

Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate based on low-field NMR

Free water plays a crucial role in the hydration process of β-calcium sulfate hemihydrate (β-HH) based plaster. To further understand the hydration mechanism of β-HH, this study monitored water consumption and pore structure evolution of plaster prepared by different water/β-HH (W/H) ratios using low-field NMR. The hydration characteristics were jointly analyzed using X-ray diffraction (XRD), thermogravimetric (TG), and isothermal calorimetry. In addition, the pore structure of the plaster was characterized by BET and MIP. Results indicated that during early hydration (0–10 min), free water migrated from macropores to micropores in β-HH samples. The specific surface area and free water content of β-HH based plaster decreased during rapid hydration period. It is also found that increasing the W/H ratio accelerated free water consumption but resulted in larger pore diameter. Furthermore, signal intensity and transverse relaxation time were found to be exponentially related (y = Ae(-x/B) + y0) to the CaSO4∙2H2O crystal content, hydration degree, and heat release. These correlations suggest that low-field NMR correlated well with other measurements and could be viable method to characterize the plaster hydration process.

CoCl2·6H2O crystal growth and its spectral characteristics

For the first time, a crystal of cobalt (II) chloride hexahydrate has been obtained, the size and quality of which have made it possible to study its faceting and spectral characteristics. The temperature dependence of the cobalt chloride solubility has been determined in the temperature range 29–44 °C. The temperature range of the transition area of change in the composition of equilibrium crystalline hydrates of cobalt chloride from CoCl2·6H2O to CoCl2·2H2O has been established. A CoCl2·6H2O crystal has been grown from a water solution, and its main transmission bands in the wavelength range of λ = 200–1400 nm and thermal stability have been estimated.