Crystal Growth & Design最新文献

A series of new coordination polymers (CPs) [Zn(tr₂btd)(bdc)]_n (compound 1), {[Zn₂(tr₂btd)₂(bdc)₂]·MeCN}_n (compound 2), {[Zn₃(tr₂btd)₄(H₂O)₂(bdc)₃]·H₂O}_n (compound 3), and [Zn(tr₂btd)₂(bdc)]_n (compound 4) were prepared from the same starting materials under different reaction conditions. Compounds 1–3 demonstrated luminescent sensing properties toward Ga³⁺ cations with the limits of detection in a low micromolar range, 1.6, 6.1, and 1.8 μM, respectively. Careful comparison of the crystal structures of the four synthesized CPs suggests that the packing features and intermolecular interactions strongly influence the luminescent and sensing properties. The luminescence sensing response was attributed to the absorption enhancement upon the interaction of metal–organic framework with Ga³⁺ via the nitrogen atoms at positions 4 of 1,2,4-triazole rings.

We report our recent observations of the growth temperature and source flux dependence of the light emission, In incorporation and quantum confinement of core–shell InGaN nanowires (NWs), self-formed in the growth temperature regime of In desorption by plasma-assisted molecular beam epitaxy on Si(111). For elevated active N flux and for relatively low growth temperatures, the photoluminescence peak wavelength and the In incorporation as a function of growth temperature exhibit an unexpected maximum. With increasing In/Ga flux ratio, this maximum shifts to lower temperature. Together, the overall In content increases, the photoluminescence shifts to longer wavelengths, the In distribution becomes more uniform and the quantum confinement of electrons and holes in the In-rich nanowire core reduces. A model based on the interplay of thermally activated In desorption with thermally activated In surface diffusion on the nanowire sidewalls accounts for the experimental results for the realization of core–shell InGaN nanowires with emission wavelengths tuned to the visible red and green and the near-infrared telecom O-band.

Scheme of the growth process of core−shell InGaN Nanowires by the interplay of In surface desorption and diffusion on the m-plane NW sidewalls and c-plane NW top. In incorporation of the core−shell InGaN Nanowires first increases and further decreases with the increasing growth temperature but the temperature of maximum In incorporation shifts toward lower values for increasing In/Ga flux ratio.

The exploration of heterometallic complexes containing both 3d and 4f metal ions has been on the rise with advancements in the field of 3d–4f single-molecule magnets. The motivation stemmed from early investigations into the Cu^II–Ln^III systems, particularly the Cu^II/Gd^III one, that revealed a ferromagnetic interaction between these ions, irrespective of the complex’s topology or nuclearity. In this context, we have synthesized three new isostructural and isomorphous [CuLn(L)(NO₃)₃(H₂O)] complexes (Ln = Gd (1), Tb (2), and Dy (3)) derived from a compartmental Schiff base ligand H₂L. All three complexes were structurally characterized in which Cu^II and Ln^III ions occupy inner N₂O₂ and outer O₂O′₂ compartments of the doubly deprotonated Schiff base ligand, respectively. Moreover, another closely related complex [Cu(L)]₂[CuDy(L)(OAc)(NO₃)(H₂O)](NO₃)·5H₂O (4) has been synthesized starting from the same Schiff base ligand H₂L to examine the effect of the coordination environment around the Dy^III ion on the dynamic magnetic behavior in these systems. Variable-temperature direct-current magnetic susceptibility measurements suggest a ferromagnetic exchange interaction between Cu^II and Ln^III ions, especially in 1–3, which is further supported by DFT calculations. However, alternating-current magnetic susceptibility measurements resulted in the most interesting part of this report. Remarkably, despite the isotropic nature of the Gd^III ion, compound 1 displayed slow relaxation of the magnetization in the presence of an applied field together with its anisotropic counterparts Tb^III (2) and Dy^III (3). Based on the literature study, this is a rare system in which Cu^II–Gd^III complexes showed single-molecule magnet behavior. Moreover, theoretical calculations were also performed by means of DFT and CASSCF levels of theory to obtain precise information on the magnetic exchange coupling between Cu^II and Ln^III ions together with the distinct magnetic dynamics in these systems.

Understanding the behavior of organic electrolytes of lithium-ion batteries is ubiquitous to help overcome the adverse impact of their freezing in cold conditions on impacting the reversibility and durability of lithium-ion batteries. Fundamental studies of the popular, yet corrosive solvent/additive fluoroethylene carbonate (FEC) appear to be few in number outside electrochemical characterization. This powder diffraction study forms what we believe to be the first to specifically probe the nature of its crystalline solid state. The crystal structure was determined ab initio with simulated annealing of powder diffraction data supported by Density Functional Theory calculations. Phase and thermal expansion behavior between 90 and 275 K were studied. Comparison powder diffraction data were obtained from the related ethylene carbonate (EC) and vinylene carbonate (VC). No solid–solid phase transitions were observed in the temperature range studied for any of the samples. FEC was found to form a three-dimensional network structure comprising hydrogen-bonded dimers as opposed to the more layered nature of the EC and VC crystal structures. The weak attractive and repulsive intermolecular interactions in the final crystal structures were examined using the Non-Covalent Interaction method and Bader partial charges.

Low temperature in situ diffraction techniques have yielded valuable insights into the crystalline structures of EC, VC, and FEC. A detailed analysis of Van der Waals interactions, dipole–dipole interactions and the factors that promote these interactions as the impact of thermal expansion on intermolecular distances was conducted in real space using the Non-Covalent Interaction (NCI) index. These interactions play a crucial role in determining the structure and thermodynamics of the crystalline phase.

Trehalose as a cryoprotectant has been studied by using cells that express a trehalose transporter (TRET1). In this study, we examine the freeze–thaw cycle survival fraction (viability) of cells using the trehalose-TRET1 system during one year of storage at 193, 213, and 235 K. To examine the possible influence of ice recrystallization on viability during such storage, we also observe the crystal grain sizes of thin ice sample. Both sets of experiments are run with and without the antifreeze glycoprotein (AFGP) as an ice-recrystallization inhibiting (IRI) agent as well as with and without the trehalose. Without the trehalose, we find that no cryopreservation occurs even with added AFGP, indicating that AFGP is not a cryoprotectant under the experimental conditions. In contrast, the viability with trehalose remains high for 1 year at 193 K. However, at the two higher temperatures, the viability with trehalose decreases rapidly at least in the first 2 months. In this initial period, ice recrystallization occurs even when AFGP is added, although AFGP exhibits IRI activity. This indicates that both intra- and extracellular ice grow in this period. As a result, we argue that the viability decrease is caused by intracellular recrystallization, mainly during the first 2 months of storage.

Two-dimensional (2-D) Bi₂Se₃ nanostructures have emerged as fine candidates due to their appealing performance toward energy conversion and storage applications. In view of this, a simple and economically viable method for their preparation is highly desirable. Herein, we present the synthesis, characterization, and structural elucidation of a new air-stable Bi-nicotinamide selenolate complex: [Bi{SeC₅H₃(3-CONH₂)}₃] (1). This complex serves as an efficient single-source molecular precursor (SSP) for the facile preparation of phase-pure Bi₂Se₃ nanostructures. The as-prepared Bi₂Se₃ nanostructures were characterized using microstructural analyses such as powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDS), and electron microscopy techniques to assess their phase purity, elemental composition, crystal structure, and morphology. This study also attempts to understand the effect of reaction conditions on the crystallinity, size, and morphology of nanostructures. The optical band gap of the nanostructures was tuned within the range of 1.9–2.0 eV, which is blue-shifted with respect to the corresponding bulk band gap and is suitable for energy conversion applications. Liquid junction photoelectrochemical cells fabricated from the as-prepared Bi₂Se₃ nanostructure exhibit good photoresponsivity and decent photostability, which project them as amenable candidates for alternative photon absorber materials.

Metal–organic frameworks (MOFs) exhibit attractive performance in fields such as luminescence sensors and catalysis. We here developed a new MOF ({Cu₂(DPQ)₂(OBPBI)}_n), briefly named Cu-MOF, which has been facilely obtained through the self-assembly of 4, 4′-(quinoxaline-2, 3-diyl)dibenzoic acid (H₂DPQ), 1, 1′-[oxybis(4, 1-phenylene)]bis(1H-imidazole) (OBPBI), and CuCl₂·2H₂O under solvothermal conditions. Cu-MOF contains a paddle-wheel and binuclear copper oxygen cluster unit and forms a 2, 2, 6-connected two-dimensional (2D) net with the point symbol of {4²·8⁸·12⁵}{4}₂{8}. Luminescence investigations indicate that Cu-MOF has a selective fluorescent response to Fe³⁺ and Cr³⁺ ions in water, with detection limits low to 10^–8 M, at least three times reusability, and a wide pH applicable scope. A combined logic gate INHIBIT has been built based on the different signal inputs of Fe³⁺ and Cr³⁺ ions and emission intensity signal outputs, providing great potential for distinguishing Fe³⁺ and Cr³⁺ ions. Moreover, Cu-MOF has been successfully applied for the catalytical conversion of CO₂ to cyclic carbonates under solvent-free and mild conditions (0.1 mol % Cu-MOF, 3 mol % TBAB, 1 atm of CO₂, 15 h, 85 °C), with up to 98% yield, 99% selectivity, and three times reusability.

Ternary cocrystals are an interesting and important topic of multicomponent crystals in crystal engineering. Although some cases of ternary cocrystals and strategies have been reported, the number remains limited, and the related principles are not yet well developed. Herein, 4-chloro-3-sulfamoylbenzoic acid and 2,4-dichloro-5-sulfamolybenzoic acid were selected as model materials, and pyridine carboxamides (picolinamide, nicotinamide, and isonicotinamide) and lactams (2-hydroxy-3-methylpyridine, 2-pyridone, and 2-hydroxy-6-methylpyridine) were used as coformers for synthesizing ternary cocrystals. With the help of powder X-ray diffraction, thermal analysis, and nuclear magnetic resonance spectra, four new ternary cocrystals were found, and the single crystal structures of three of them were successfully analyzed. The functional group position in coformers is found to have two effects on ternary cocrystals. On the one hand, it affects the tendency to generate binary products. On the other hand, there is a certain match between the two types of coformers. Further theoretical calculations show that geometrical recognition among the three components is more important for the formation of ternary cocrystals than the lattice energy.

In this study, we report the syntheses of two new coordination polymers (CPs) of Mn(II) and Co(II), [Mn(4-avp)₂(adc)(H₂O)]·(solvent)_x (1) and [Co(4-avp)₂(adc)(CH₃OH)₂] (2), respectively, using relatively less explored linear linker acetylenedicarboxylic acid (H₂adc) and polyaromatic hydrocarbon (PAH)–based monodentate N-donor ligand 4-[2-(9-anthryl)vinyl]pyridine (4-avp). CP1 creates a two-dimensional (2D) structure in this instance, while CP2 is made up of a 1D chain polymer. It is of interest that CP1 and CP2 exhibit semiconducting behavior and behave as Schottky barrier diodes. However, CP1 exhibits higher conductivity and better Schottky diode formation when compared to CP2, which relates to the charge transportation through space via π···π interactions present in CP1. The experimental results are well validated by theoretical density functional theory (DFT) prediction based on band gap and density-of-state (DOS) calculations. It is noteworthy that fabrication of Mn/Co-based Schottky devices appears to be inadequate in the literature. Thus, this work showcases a new direction for the development of electronic device fabrication.

Investigating the low-temperature crystallization behavior of liquid polysiloxanes poses a significant challenge. To address this issue, a custom low-temperature chamber with specialized sample holders was meticulously constructed and integrated with a laboratory X-ray diffraction apparatus, enabling time-resolved wide-angle X-ray diffraction (WAXD) measurements of linear poly(dimethylsiloxane) (PDMS) oil and cross-linked PDMS film during cooling and heating. Under vacuum pumping and capillary confinement, the linear silanol-terminated PDMS oil demonstrates significant crystalline orientation at low temperatures when the crystalline index surpasses 10%, with the recorded 2D diffraction patterns showing heterogeneous azimuthal intensity distributions. The presence of crystallographic anisotropy is strongly influenced by the experimental vacuum pumping rather than the millimeter-scale capillary confinement. Unlike the strain-induced alignment of crystalline planes observed in stretched PDMS film, the vacuum-pumping-induced crystallographic anisotropy in linear PDMS oil measured within a capillary only results in a minimal or partial lamellar orientation. This alignment will cause crystalline chain segments to pack parallel to the incident X-ray beam direction and fold within the a-c plane. These findings are expected to enhance low-temperature X-ray analysis techniques for liquid samples and facilitate future crystallographic investigations of polysiloxane materials.