CrystEngComm最新文献

In this study, we utilized first-principles methods to delve into defect clusters within potassium dihydrogen phosphate (KDP) crystals, focusing on (Mg_K + V_K) and (Mg_K + V_H) configurations. We examined their stability, defect formation energy, lattice distortion, electronic structures, and optical properties in both paraelectric (PE-KDP) and ferroelectric (FE-KDP) phases. In the PE phase, compensation of was accomplished via the nearest neighbor . Conversely, in the FE phase, compensation of was achieved utilizing the next nearest neighbor . Notably, the Mg–O ionic bond displayed significant changes in bond length, with a maximum alteration of 60%, as neighboring oxygen atoms moved closer to the magnesium atom. Furthermore, both structures displayed a downward shift of the conduction band minimum (CBM), primarily due to contributions from Mg 3s and O 2p orbitals, resulting in a reduction in the band gap. By analyzing the photoluminescence process alongside electron–phonon coupling phenomena, absorption and emission spectra were obtained. In the absorption spectra, peaks for PE-KDP and FE-KDP were observed at 335 nm and 386 nm, respectively, consistent with experimental observations of absorption at 355 nm. Upon exposure to a 355 nm laser, local crystal absorption led to a progressive increase in temperature, consequently lowering the damage threshold.

A facile solution method for the form-controlled synthesis of CsMgPO₄·6H₂O is reported in this work and the key factor was determined to be the pH value of the solution used. A pure hexagonal phase (P6₃mc) was obtained at a pH range of 6.9–8.0, whereas a cubic phase (F₃m) was obtained at 9.5–11.3. Compared with the cubic phase, the hexagonal phase of CsMgPO₄·6H₂O possessed a stronger second harmonic generation response of 0.82 pm V⁻¹ due to the distortion of the PO₄ motif from a regular tetrahedron. The form-controlled synthesis mechanism was identified with the aid of infrared spectroscopy: the protonation process reduced the symmetry of the PO₄ motif when the solution pH decreased, resulting in the crystallization of the hexagonal phase of CsMgPO₄·6H₂O with the distorted PO₄ tetrahedron at a lower pH range.

Regulation of the complex structure is greatly significant for the preparation of single-molecule magnets (SMMs). In this work, a multidentate ligand of N,N′-bis(3-carboxy-4-hydroxyphenyl)-1,4,5,8-naphthalenetetradicarboximide (H₄NDISA) has been synthesized and reacted with dysprosium(III) salt. By controlling the ratio of metal ions to the ligand and reaction temperature, three new dysprosium(III) complexes are obtained, namely, [Dy₂(H₂NDISA)₃(DMF)₃(H₂O)₁₀]·1.4DMF·2.6H₂O (1), {[Dy(H₂NDISA)_1.5(DMF)(H₂O)₄]·3DMF·4H₂O}_n (2), and {[Dy(HNDISA)(H₂O)₂]·4H₂O}_n (3). Their structures are determined by single crystal X-ray diffraction. Crystallographic data demonstrate that complex 1 is a dinuclear dysprosium(III) complex linked by the bidentate ligand of H₄NDISA. The intramolecular Dy(III)⋯Dy(III) distance is 23.0861(7) Å. In complex 2, the carboxyl group in one of the ligands adopts a μ-η₂:η₁ bridging mode to connect two Dy(III) ions, resulting in a Dy(III)⋯Dy(III) distance of 5.2611(5) Å. The other ligand adopts a tetradentate coordination mode to bridge two Dy(III) ions, forming an infinite one-dimensional chain structure along the c axis. Complex 3 displays a two-dimensional network structure. One carboxyl group in the ligand adopts a μ-η₁:η₁ bridging mode growing along the c axis. Another carboxyl group in the ligand adopts a μ-η₂:η₁ bridging mode. The shortest distance of Dy(III)⋯Dy(III) is 4.6138(5) Å. DC and alternating current (AC) magnetic susceptibilities of complexes 1–3 were measured. AC magnetic susceptibility measurements show that complexes 1–3 exhibit frequency-dependent ac susceptibilities.

Amorphous phases commonly accompany materials obtained through a number of methods, which often significantly change the functional properties of the materials. Thus, when present in photocatalysts, they decrease the photocatalytic performance of the materials significantly. To minimize the amorphous content in photocatalysts and increase their photocatalytic properties, hydrothermal post-treatment of amorphous photocatalysts is suggested. In this work, a series of brookite-based titania materials were obtained via the post-treatment of amorphous titania under hydrothermal conditions to determine how synthesis parameters affect the properties of the obtained TiO₂ materials. The samples were characterized via X-ray diffraction analysis, scanning and transmission electron microscopy, and low-temperature nitrogen adsorption analysis. Special attention was given to the amount of residual amorphous phases in the samples. Results indicated the possibility of selectively crystallizing titania materials with high brookite contents and enhanced photocatalytic properties from amorphous titania without significantly altering the form of the particles. This study presents the amorphous phase as a valuable precursor to obtain highly crystalline materials with vast control of phase composition.

Tin sulfide (SnS) is widely recognized as a promising material for thermoelectrics owing to its layered structure, anharmonicity, earth abundance, and minimal toxicity. This study focuses on controlling the hole concentration of SnS by substituting isovalent Zn through a vacuum melting technique. The presence of point defects, such as mass fluctuations and strain field fluctuations, along with lattice dislocations and stacking faults, results in a drop in thermal conductivity. The mass difference between Zn dopant and Sn host atoms plays a significant role in point defect scattering when Zn is substituted in the SnS lattice. Additionally, variations in size and interatomic coupling forces between Zn and Sn atoms contribute to the amplification of point defect scattering, effectively reducing the lattice thermal conductivity. Furthermore, the diminished lattice thermal conductivity of SnS samples with Zn substitution is ascribed to the decreased phonon mean free path. The synergy of multi-scale scattering results in a low thermal conductivity of 0.88 W m⁻¹ K⁻¹ at 773 K. Further, Zn substitution slightly improved the carrier concentration from 6.88 × 10¹⁵ cm⁻³ to 2.31 × 10¹⁶ cm⁻³ resulting in enhanced electrical conductivity without the drastic decrement in the Seebeck coefficient. This in turn significantly improved the power factor to 42.6 μW m⁻¹ K⁻² for the Sn_0.95Zn_0.05S sample.

Bi-based materials can retain massive amounts of sodium ions through alloying and conversion reactions, resulting in excellent theoretical capacity. However, during the sodiation/desodiation process, there is always a significant volume change in the alloying reaction. In this work, TiO₂-coated hexagonal-phase topological insulator (TI) Bi₂Te₃ composites grown on carbon cloth (CC) were prepared using a solvothermal reaction and an atomic layer deposition process (TiO₂/Bi₂Te₃/CC) as anode materials for sodium-ion batteries without the need for a binder. Compared to the pure Bi₂Te₃ electrode, the optimized TiO₂/Bi₂Te₃/CC composite exhibits a superior specific capacity of 450 mA h g⁻¹, a high rate performance of 0.1 A g⁻¹, and a high cycling stability of 100 cycles due to the inherent properties of TIs, contributed by the effective TiO₂ cladding layer and large interfacial spacing of Bi₂Te₃. The enhanced reversible capacitance, rate capability, and cycling performances can be attributed to the heterointerfaces and excellent mechanical properties of TiO₂, which balance the electronic structure of the building blocks and inhibit the detaching of Bi₂Te₃ due to large internal stresses. The amorphous TiO₂/Bi₂Te₃/CC composite was treated in a tubular furnace to obtain crystalline TiO₂/Bi₂Te₃/CC, and the electrochemical performance of the heterostructures formed by the TiO₂ coating layer with different properties was compared. This work demonstrates the enormous potential for enhancing the sodium-ion storage capabilities of alloy electrode materials by constructing heterostructures.

CO₂ is considered the primary contributor to greenhouse gases in the atmosphere and is responsible for several global environmental and energy-related disasters, causing serious concerns because of its adverse impacts on the deterioration of the global ecosystem. Thus, it is now crucial to develop efficient strategies for capturing CO₂ and its conversion into desired products. It is anticipated that this will greatly improve the stability of the ecosystem and encourage sustainable expansion in the energy industry. In this case, metal organic frameworks (MOFs) are becoming increasingly popular nowadays as a result of their appealing features including large internal surface area, structural homogeneity, and flexible porosity. This review critically examines the current advancements and real-world applications of metal–organic frameworks for CO₂ fixation and its conversion into useful chemical products. Considering this, the contemporary trends and developments in CO₂ conversion into cyclic carbonates, formic acid, olefins, methane, carbon monoxide, heterocycles, etc. via cycloaddition, hydrogenation and carboxylation processes are comprehensively deliberated.

Switching from positive (PTE) to negative thermal expansion (NTE) in a molecular crystal is a rare phenomenon. Here we report the switching of PTE to NTE in 1,1′-(octa-1,3,5,7-tetrayne-1,8-diyl)dicyclopentanol (1) along the crystallographic a-axis. Small PTE has been observed from 100 K to 200 K due to zigzag packing arrangement and then the large transverse vibration overpowers the PTE resulting in NTE after 200 K.

The development of low-cost, efficient, and stable bifunctional electrocatalysts is very important for the development of renewable energy. Layered double hydroxides (LDHs) are considered to be promising electrocatalysts due to their flexible ion exchange, abundant structural adjustability, excellent thermal stability, and easy functionalization with other materials. In this work, nickel-cobalt layered double hydroxide (NiCo-LDH) nanosheet arrays are prepared by a simple hydrothermal method. Four samples Ni₁Co₄-LDH, Ni₂Co₃-LDH, Ni₃Co₂-LDH and Ni₄Co₁-LDH are obtained by adjusting the Ni/Co ratio (5 − x : x). Among them, the Ni₂Co₃-LDH samples show excellent HER and OER properties. At a current density of 50 mA cm⁻² in a 1.0 M KOH electrolyte, the overpotentials of the HER and OER are 227 mV and 303 mV, respectively. In addition, as a bifunctional electrocatalyst for water splitting, the sample provides a voltage of 1.83 V and long-term stability at 50 mA cm⁻².

New cesium cerium(IV) iodate Cs₂Ce(IO₃)₆ was successfully prepared by applying a hydrothermal technique from starting reagents CsF, CeO₂, H₅IO₆ and HIO₃ at 230 °C. Cs₂Ce(IO₃)₆ was analyzed via single crystal and powder XRD, EDX, IR spectroscopy and thermal analysis. The new compound crystallizes in the monoclinic space group C2/c with a = 14.0652(3) Å, b = 8.1890(2) Å, c = 17.7211(4) Å, β = 103.601(2)°, V = 1983.99(8) ų, and Z = 4. The crystal structure of Cs₂Ce(IO₃)₆ consists of CeO₈ square antiprisms sharing their apexes and edges with trigonal pyramidal IO₃⁻ groups to form layers [Ce(IO₃)₆]²⁻ parallel to the ab plane. These layers are further stabilised by a 12-vertex polyhedron, CsO₁₂, situated in their voids. The IR spectrum of Cs₂Ce(IO₃)₆ displays iodate group bands. According to DTA analysis, cesium cerium(IV) iodate exhibits high thermal stability in the air at temperatures up to 414 °C.