CrystEngComm最新文献

In this study, Yb/Er/Tm-doped NaLuF₄ luminescent microcrystals were synthesised hydrothermally. Then, the upconversion spectra of these microcrystals at low temperatures (5–303 K) were investigated, and their potential for temperature sensing assessed. As the temperature decreased, the intensity of the emission peak correspondingly increased. However, the emission peak at 520 nm was not readily discernible at temperatures below 160 K. The kinetic process of luminescence decay typically increased with decreasing temperature. Furthermore, the emission peak at 539 nm exhibited a pronounced sensitivity to variations in temperature. The system's temperature-sensing capabilities, which rely on both thermally and non-thermally coupled energy states, were evaluated in low- (160–280 K) and high-temperature (333–493 K) ranges. At the lower end of the temperature scale (160 K), the maximum value of relative sensitivity was 4.29% K⁻¹, which was 4–5 times higher than that at high temperatures. These findings demonstrate the significant potential of the material for temperature-sensing applications and introduce a novel concept for such uses.

Achieving specified levels of impurities is one the key goals of crystallisation processes in manufacturing. The mode of impurity incorporation and the variation of impurity levels throughout crystal batches are key factors affecting the performance of crystallisations in terms of achieving purity specifications. Evaluation of the distribution of impurities in crystals of flufenamic acid (FFA) using a controlled partial dissolution approach is described. 2-(3-Tolylamino)benzoic acid (MeFA) and 2-((3-(tert-butyl)phenyl)amino)benzoic acid (tBuFA), analogues of FFA in which the trifluoromethyl group has been replaced by a methyl group or by a tert-butyl group respectively, were selected as the impurities. Thermal analysis suggests formation of a solid solution between FFA and MeFA isostructural to FFA form III. The stepwise dissolution approach was initially demonstrated on samples of pure FFA crystals and was then extended to evaluate the distribution of levels of MeFA and tBuFA impurities. The impurity levels are shown as varying with dissolution midpoint. Stepwise dissolution was usefully applied to FFA crystal of various morphologies, while for crystals with extremely needle-like morphology, a segmentation analysis approach was more practical. The work presented outlines a method for evaluating the distribution of impurities in crystalline materials using commonly available analytical and particle sizing methods.

To enhance the gas sensing response performance of LDH materials, this study employed a hydrothermal synthesis method using sodium citrate as an inducer and urea as a precipitant. Graphene with excellent conductivity was used as a substrate. By controlling the solution's alkalinity, sheet-like NiFe-LDHs were successfully induced and assembled on the ultra-thin graphene surface. SEM and AFM characterizations confirmed that the flower-ball morphology of the LDHs, formed by the aggregation of nanosheets, created ultra-thin nanosheets of 6–8 nm that fully covered both sides of the 3–4 nm GO, rendering the material highly porous and well ordered (specific surface area of 111.39 m² g⁻¹). At ambient temperature (RH = 26%), the sample NF/rGO2 with 0.12 g of sodium citrate exhibited extremely high sensitivity and rapid response to 100 ppm NO₂, with a response value and response/recovery time of 22.30 and 2.8/46 s, respectively. Moreover, the sensor demonstrated high selectivity and remarkable long-term stability for up to 100 days. The superior gas sensing performance can be attributed to the unique morphology of the composite material: the inhibited growth of LDHs on the graphene surface exposed numerous basic sites between layers, enhancing NO₂ adsorption capability. Additionally, the staggered and orderly arrangement of ultra-thin LDHs significantly improved the electron transport rate. Therefore, the response/recovery time of the gas sensing material was considerably shortened, enhancing the gas sensing performance of the material. This study provides a novel approach for the preparation and synthesis of high-sensitivity and high-performance NO₂ sensors at room temperature.

It is shown that periodic density functional theory (DFT) with hybrid exchange–correlation functionals can be applied to determine the chemical nature of acid–base multicomponent crystals. For a test set of experimentally assigned crystals, the energies of reference “pure” cocrystal and salt forms are calculated in an efficient numerical atomic orbital (NAO) formalism. It is found that energy differences from hybrid DFT can reliably place most of the considered crystals in their assigned chemical class. It is further discussed how DFT has reached the maturity where it may help with the interpretation of ambiguous experimental characterizations and transform how different states along the salt–cocrystal continuum are classified.

In order to overcome the often large activation barriers in heterogeneous catalytic reactions, photocatalysis is a promising path to activate specific molecules with light at moderate temperatures. In particular, bimetallic nanoparticles combining the plasmonic properties of one metal with the high catalytic activity of another are promising antenna–reactor systems. As the nanocrystal surface structure is a major factor in steering surface electronic properties and accompanying activity and selectivity, it is of interest to control the metal nanoparticle growth and composition. The subject of this work is the synthesis of gold–platinum nanoparticles with varying architectures by controlling the growth mechanism. The selection of the reducing agent allows the regulation of the reduction rate of the platinum metal salt, which in turn affects the final morphology of the resulting bimetallic nanoparticles. This allows the synthesis of either core–shell nanocrystals with decorated nanocube corners or dendritic particles under otherwise identical reaction conditions. A dendritic structure requires the rapid deposition of platinum monomers on the surface of the gold particles. This process hinders the diffusion of platinum monomers to energetically preferred sites on the particle surface, which is possible during the formation of core–shell nanocrystals.

By adjusting the pH values, two types of heterometallic complexes originated from the same raw materials but with different structures and colors have been successfully designed and constructed. Eleven 3d–4f cobalt–lanthanoid heterometallic complexes, [Ln₂Co₂(2,5-DCB)₁₀(phen)₂] [Ln = Nd (1 and 1a), Sm (2 and 2a), Eu (3 and 3a), Gd (4), Tb (5), Dy (6), Er (7), and Yb (8)], were prepared through the self-assembly reactions of Ln(NO₃)₃·nH₂O, Co(NO₃)₂·6H₂O, 2,5-dichlorobenzoic acid (2,5-HDCB), NaOH, and 1,10-phenanthroline (phen) under solvothermal conditions. All of these complexes were characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Complexes 1 and 1a (2 and 2a, 3 and 3a) are available at different pH ranges, respectively. Their structures and colors are different from each other. Complexes 1–8 and 1a–3a are found to be isostructural, respectively. The photoluminescence properties of 3 and 3a as well as the magnetic properties of 1, 2, 1a, 2a, and 4–8 were investigated. Complexes 3 and 3a display similar characteristic luminescence of Eu(III) and different emission lifetimes. Complex 4 exhibits weak ferromagnetic coupling between the spin carriers below 10 K, and complex 6 shows a slow magnetic relaxation behavior.

Crystallization of N-chlorosaccharin with quinuclidine (QN) produced QN-Cl⁺ cations showing a covalent bond between chlorine and a tertiary nitrogen atom. Strong (supramolecular) halogen bonds between the QN-Cl⁺ and Cl⁻ anions in their 2 : 1 and 1 : 1 complexes comprise a large contribution of orbital (covalent) interactions.

A series of 4-aminopyridinium (4ap) hypodiphosphates has been synthesized and characterized by variable temperature (VT) optical microscopy, thermogravimetry (TGA-DSC) and X-ray diffraction techniques (SC-XRD, PXRD, VT μ-PXRD). Anhydrous salts (4apH)(H₃P₂O₆) (2) and (4apH)₂(H₂P₂O₆) in monoclinic (C2/c) (4), orthorhombic (P2₁2₁2₁) (5) and another monoclinic (Cc) (6) polymorphic modifications were obtained by single crystal-to-powder dehydrations of the hydrates: ionic co-crystal (4apH)₂(H₂P₂O₆)·H₄P₂O₆·2H₂O (1) and salt (4apH)₂(H₂P₂O₆)·2H₂O (3), respectively. Compound (2) was the only anhydrous form which was also obtained by a typical solution-crystallization. Destructive dehydrations strongly affected hypodiphosphate substructures, generating new structural motifs (both in PP–PP and ap–PP interactions) and new crystal architectures, thus revealing the structural diversity in organic hypodiphosphates. Dehydration gave rise to new properties, as non-centrosymmetric and polar anhydrous structures, (5) and (6) respectively, were obtained from centrosymmetric hydrate (3).

Correction for ‘Improving the grindability of rice husk-based green silica through pyrolysis process optimization employing the Taguchi method and response surface methodology’ by Shengwang Yuan et al., CrystEngComm, 2024, 26, 128–142, https://doi.org/10.1039/D3CE01016C.

Postsynthetic modification of porous organic polymers (POPs) facilitates their use to remove toxic gases, such as NH₃. This study conducted a fluorine- and sulfur-targeted postsynthetic modification of POPs to enhance their low-pressure NH₃ adsorption capacity. For the first time, F and S-targeted postsynthetic modification for NH₃ capture using porous adsorbents was demonstrated.