Rod-shaped Crystals Research Articles

Synthesis and characterization of magnetic nanoparticle-incorporated nanohydroxyapatite and calcium and phosphate ion clusters for biomimetic remineralization of enamel and dentin

Aim: The present study aimed to synthesize and characterize magnetic nanoparticle incorporated nanohydroxyapatite (MNHAP), calcium and phosphate ion clusters (CPICs), and their combination with MNHAP. Materials and Methods: Nanohydroxyapatite (NHAP), magnetite (Fe3O4), and magnetic nanoparticle-incorporated nanohydroxyapatite (MNHAP) were synthesized using wet precipitation method, co-precipitation method, and ultrasonic-assisted mechanical stirring methods, respectively. CPIC was synthesized by centrifugation method. Their characterizations were analyzed through X-ray diffraction (XRD) crystallography, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and high-resolution transmission electron microscopy. The biocompatibility of MNHAP was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results: XRD substantiated the presence of diffraction peaks, indicating crystallinity in all synthesized samples. Functional groups in NHAP and MNHAP were confirmed through FTIR analysis. VSM analysis demonstrated superparamagnetic behavior in both MNHAP and Fe3O4. Transmission electron microscope images unveiled the needle-like crystals for NHAP, rod-shaped crystals for MNHAP, and polyhedral shapes for CPIC combined with MNHAP (CPIC + MNHAP). MNHAP exhibited biocompatibility up to 200 µg. Conclusion: Based on the findings of this study, MNHAP and CPIC + MNHAP may be suitable for the repair of initial caries lesions.

A new microcoprolite assemblage from the Upper Triassic Tiki Formation of India: ichnotaxonomy, and producer association(s)

ABSTRACT We record the first occurrence of a microcoprolite assemblage from the Upper Triassic Tiki Formation, Son – Mahanadi Basin, India. The microcoprolite assemblage has been assigned to four new ichnotaxa namely Cylindrocopros gondwanensis igen. et isp. nov., Elliptocopros rewaensis igen. et isp. nov., Convolucopros shadolensis igen. et isp. nov., and Cylindribulbocopros triassicus igen. et isp. nov. based on their external morphology, internal texture, and geochemical composition. Geochemical techniques confirm the phosphatic nature of the microcoprolites recorded from the Tiki Formation. Taken together, the associated fauna and the morphological comparisons between previously known coprolites from the Mesozoic-Cenozoic sedimentary sequences suggest that the Tiki microcoprolites were likely produced by carnivorous actinopterygians. The dentalites or biting traces observed on the external surface of the ichnotaxa recorded herein are the oldest records from the subcontinent. SEM analysis reveals the dominant presence of egg-like mineral spheres ‘microspherulites’, needle- and rod-shaped apatite crystals; however, the microcoprolites are devoid of biotic (floral and faunal) inclusions. Considering the abiotic crystals and geochemistry, we infer that the original faecal matter most likely underwent rapid precipitation during the early phase of mineralisation and had a very high potential for fossilisation.

P1-xTa8+xN13 (x=0.1-0.15): A Phosphorus Tantalum Nitride Featuring Mixed-Valent Tantalum and P/Ta Disorder Visualized by Scanning Transmission Electron Microscopy.

We report on the synthesis, crystal, and electronic structure, as well as the magnetic, and electric properties of the phosphorus-containing tantalum nitride P1-xTa8+xN13 (x=0.1-0.15). A high-pressure high-temperature reaction (8 GPa, 1400 °C) of Ta3N5 and P3N5 with NH4F as a mineralizing agent yields the compound in the form of black, rod-shaped crystals. Single-crystal X-ray structure elucidation (space group C2/m (no. 12), a=16.202(3), b=2.9155(4), c=11.089(2) Å, β=126.698(7)°, Z=2) shows a network of face- and edge-sharing Ta-centered polyhedra that contains small vacant channels and PN6 octahedra strands. Atomic resolution transmission electron microscopy reveals an unusual P/Ta disorder. Mixed-valent tantalum atoms exhibit interatomic distances similar to those in metallic tantalum, however, the electrical resistivity is quite high in the order of 101 Ω cm. The density of states and the electron localization function indicate localized electrons in both covalent and ionic bonds between P/Ta and N atoms, combined with less localized electrons that do not contribute to interatomic bonds.

Effective removal and immobilization of radioactive iodate from aqueous solution by iron-gallic acid@palygorskite nanohybrid

Here, we developed a new low-cost and high-efficiency adsorbent, iron-gallic acid@palygorskite nanohybrid, for removing and immobilizing radioactive IO3- from wastewater. The results show that the key factor affecting the adsorption performance of the hybrid is the reaction time, which determines the degree of coating of GA-Fe(II) nanoparticles on the palygorskite. These nanoparticles are very randomly distributed on the surface of palygorskite rod-shaped crystals or combined with a large number of rod-shaped accumulations of palygorskite. In addition to the GA-Fe(II) complex formed at a molar ratio of 1:1, there are also iron elements in the hybrid that may be fixed to the surface and lattice of the palygorskite by ion exchange and isomorphic substitution. The adsorption process conforms to the pseudo-second-order kinetic model and Langmuir isotherm model, with a maximum adsorption capacity of 78.37 mg/g. It is also a spontaneous, endothermic, and disorder-increasing process. The extremely low desorption efficiencies confirm that the GA-Fe(II) complex exhibits strong chemical adsorption with the iodate, and the positively charged sites such as ferrous and iron ions presented in the palygorskite can also be fixed to the iodate through electrostatic attraction. Therefore, this adsorbent exhibits good application potential in the treatment of radioactive iodate wastewater.

Synthesis of Zr/La-BTC Bimetallic Metal-Organic Framework (MOF) for Oleic Acid Esterification

Biodiesel plays an essential role in renewable energy as an alternative fuel to tackle the challenges of global warming, environmental degradation, and alternative fossil fuels. Oleic acid can be converted into biodiesel by the esterification process, which employs heterogeneous catalysts such as metal-organic frameworks (MOF). In this study, Zr/La-BTC MOFs were used as different kinds of catalysts to change oleic acid into biodiesel. The characterization results of Zr-BTC, La-BTC, and Zr/La-BTC using FTIR and XRD show that the MOF has been successfully formed. The crystallite sizes for La-BTC, and Zr/La-BTC MOFs are 15.7407 nm and 39.0392 nm, respectively. The surface area of Zr-BTC, La-BTC, and Zr/La-BTC MOFs are 167.101 m2/g, 12.328 m2/g, and 4.764 m2/g. The morphology of Zr-BTC MOF using SEM is irregular, La-BTC is rod-shaped crystal, and Zr/La-BTC is like a knot bond with a narrow waist. The most optimal reaction was obtained at a 5% (w/w) catalyst dosage of total oleic acid and methanol (1:60 mol), 65 °C, and a reaction time of 4 hours, producing 78.11% oleic acid conversion. GC-MS analysis identified that the biodiesel contains oleic acid, palmitic acid, methyl oleate, and methyl palmitate.

Nanoparticle-based delivery of harmine: A comprehensive study on synthesis, characterization, anticancer activity, angiogenesis and toxicity Evaluation

The effective treatment of cancer presents numerous challenges, including drug resistance and the risk of detrimental effects on normal tissues. Harmine, a beta-carboline alkaloid, has demonstrated diverse biological properties. This study aimed to synthesize and characterize harmine encapsulated in polylactic-co-glycolic acid (PLGA) nanoparticles (Ha-PLGA-NPs) to investigate their potential as agents against cancer and angiogenesis. The synthesized Ha-PLGA-NPs were thoroughly characterized, exhibiting a connected rod-shaped crystal which some retaining the spherical shape of nanoparticles with an average size of 302.96 nm. Furthermore, the nanoparticles demonstrated a dispersion index of 0.23 and a surface charge of −16.51 mV. In vitro cytotoxicity assays conducted on the breast cancer cell line (MCF-7) revealed that Ha-PLGA-NPs possessed significant cytotoxic properties, with an observed IC50 value of 87.74 μg/mL. Notably, no substantial cytotoxicity was observed in human foreskin fibroblasts, indicating a favorable selectivity towards cancer cells. Evaluation of the anti-angiogenic activity of Ha-PLGA-NPs demonstrated a concentration-dependent inhibition of angiogenesis. Mechanistic investigations indicated that the observed inhibition was mediated through the regulation of key genes involved in angiogenesis, including caspase 3, caspase 9, VEGF, and VEGF-R. In vivo studies involving dietary administration of Ha-PLGA-NPs in mice revealed improvements in weight gain, feed intake, liver enzyme levels, and redox potential. These findings underscore the potential of Ha-PLGA-NPs as a promising therapeutic agent for cancer treatment. The observed effects are attributed to their ability to induce programmed cell death and inhibit angiogenesis, thus offering a multifaceted approach to combat cancer.

Detoxification of toxic nerve agent sarin utilizing cupric oxide functionalized activated carbon fabric composite for advanced NBC Protective Clothing

ABSTRACT This investigation delves into the development of cupric oxide functionalized activated carbon fabrics (ACF@CuO) as a filter material for self-decontaminating protective clothing designed to counter chemical warfare agents (CWAs). Three variants of samples were developed by controlling functionalization levels (7.5%, 13.0%, 16.0% w/w) through optimized precursor concentrations, integrating CuO particles onto ACF surfaces. Comprehensive analysis using techniques like FTIR, BET surface area, SEM, EDX, STEM, XRD, TGA, and XPS explored the material’s properties. The studies concentrated on evaluating the performance through kinetic studies of self-detoxification of CWA Sarin (GB) using developed ACF@CuO materials analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). ACF@CuO with 16% w/w functionalization exhibited superior self-decontamination against GB, achieving 92.87% efficiency within 18 hours, in contrast to 26.55% for ACF alone. Additionally, materials were tested for tensile strength, air-permeability, and Sulfur Mustard breakthrough time (HDBTT) as per IS 17377:2020 standard. The material with 13% w/w functionalization emerged as the recommended filter layer for CWA protective clothing designed for defense and civilian safety applications. The significant improvements in the self-decontamination efficiency of the material were attributed to the synergistic effects of ACF’s adsorption capabilities combined with the decontamination properties of CuO rod-shaped crystals embedded in the surface of ACF.

Rod-Shaped Hemoglobin Crystals: Clues to the Diagnosis of Hemoglobin C Disease.

The typical rod-shaped HbC crystals in the peripheral blood smear often provide the diagnostic clue to the HbC disease. This case highlights that a careful review of blood film morphology may be helpful to detect HbC disease, although this case's routine blood test is normal and do not meet the rules of re-examinations.

Fluorinated liquid crystals and their mixtures giving polar phases with enhanced low-temperature stability

ABSTRACT The fluid ferroelectrics, called ferroelectric nematics (NF), have recently become available by incorporating strong polarity into rod-shaped liquid crystal molecules. Its unprecedented electro-optic properties have created significant excitement in soft matter research. The further progression from the NF phase to the antiferroelectric smectic Z (SmZA) phase, and ultimately to the ferroelectric Smectic A (SmAF) phase, represents a remarkable journey in emerging polar liquid crystal states. Nevertheless, the limitation of NF liquid crystal materials remains one of the prominent obstacles to physical property optimization and optoelectronic device development. In this work, we synthesized a series of fluorinated liquid crystal molecules with large dipole moments and systematically investigated their phase behavior. We designed them with a similar fluorinated aromatic skeleton and varied the structures of the terminal group and bridging bond. We found that the dipole moment density and shape anisotropy significantly affect the phase behavior. Notably, diverse polar liquid crystal phases, including NF, SmZA, and SmAF were observed. Through a multi-component mixing strategy, we successfully achieved a much-expanded temperature window and improved low-temperature stability not only in the NF phase but also in the SmZA and SmAF phases.

Study of the solvent-dependent crystal shape of theophylline using constant chemical potential molecular dynamics simulations.

The crystal habit of an organic crystalline material impacts its properties, processing, and performance, especially in pharmaceuticals. In solution crystallization, solvents play a crucial role in modulating the crystal habits by interacting with the different growing facets - either enhancing or inhibiting the growth of specific facets. Thus, an in-depth understanding of the role of the solvent in crystal shape selection is of paramount importance for the design and growth of crystals. In this work, we used constant chemical potential molecular dynamics (CμMD) to simulate the growth of theophylline crystals in solvents with decreasing polarity, i.e. water, isopropyl alcohol, and dimethylformamide. Our results indicate that as the polarity of the solvent increases, theophylline crystallizes into rod-shaped crystals; the aspect ratio is modulated by the relative growth of the (001) and (010) facets. Furthermore, solvent profile analyses revealed that the desolvation of the crystal facets plays a major role in the growth process.

Synergetic Effect Of Ternary Mixture Of Nano Silicon Carbide-Polyvinyl Alcohol-Lithium Sulfate On Early Strength Of Cement

T o solve the problems of low compressive strength and unstable sealing capability of traditional hole sealing materials in the early stage of underground coal mines, a new cement-based sealing material was developed in this study by mixing ordinary Portland cement with nanomaterial, water-soluble polymer and lithium salt as additives. The early strength and the microstructure evolution of the as-prepared cement material were investigated with uniaxial compression test, scanning electron microscope (SEM), thermogravimetric analysis and X-ray diffraction (XRD). The results show that the ternary composite material (nano silicon carbide, polyvinyl alcohol and lithium sulfate) can effectively improve the early strength of cement. The 1-day compressive strength increased from 8.56 to 14.21 MPa, pointing out an improvement rate of 66.00%. It can be seen from the SEM images that a large number of fibrous C-S-H crystals and rod-shaped AFt crystals formed in the ternary composite cement sample. The nanosized silicon carbide (SiC) can accelerate the generation of hydration products through forming nucleation sites. As a dispersing agent polyvinyl alcohol (PVA) can effectively prevent the agglomeration of SiC nanoparticles and the formation of cement particle flocculation structure. On the other hand, the lithium cations and the sulfate anions of lithium sulfate could penetrate the hydration film structure and react with the hydration product Ca(OH)2, respectively, which promotes the hydration reaction. The promotion effect of the ternary composite material on the formation of hydration products results in a clearly improved early strength of the new cement-based sealing material.

Nanocrystalline solid dispersions: an emerging approach for oral bioavailability enhancement of anticancer drugs using lapatinib ditosylate as the case drug

The bioavailability of lapatinib ditosylate, an active anticancer agent against breast neoplasms, is constrained by its poor bioavailability due to poor aqueous solubility. So, the study’s objective was to develop its nanocrystalline solid dispersion (NSD) in order to improve its oral bioavailability. The process of wet media milling followed by lyophilization was used to prepare NSDs of the drug. Using polyvinyl pyrrolidone (PVP), and sodium dodecyl sulfate (SDS) as combination stabilizers, the resultant NSD demonstrated the smallest particle size and a sufficient stability during formulation screening. Differential scanning calorimetry, and powder X-ray diffraction techniques confirmed the crystalline state of the dispersion. Scanning electron microscopic analysis of optimized NSD revealed evenly distributed rod-shaped crystals of lapatinib ditosylate. The molecular-level interaction in the formulated dispersion was confirmed by NMR analysis. The formulated NSD has enhanced aqueous solubility of lapatinib ditosylate, by 3.68 folds. It also exhibited improved drug release as well as enhanced in vitro anticancer activity in the MCF-7 cell line. Similar findings were derived from in vivo pharmacokinetic investigations, where, compared to pure drug, the maximum plasma drug concentration (Cmax), and area under the curve (AUC), of formulated NSD, increased by 2.45, and 2.56, times respectively for lapatinib ditosylate. All these pharmacokinetic parameters were found to be improved in formulation LP, when compared to the marketed formulation, Tykerb. Thus, this study demonstrated a commercially viable method for increasing the oral bioavailability of anticancer drug, lapatinib ditosylate through the screening and optimization of stabilizers in nanocrystalline solid dispersion.

In situ synthesis of TiB2 rod crystal reinforced PcBN mechanical properties: First-principles calculations and experimental study

In this work, a combination of first-principles calculations and experiments is used to not only reveal the growth mechanism of hexagonal rod-shaped crystals TiB2 and its theoretical influencing factors, but also to experimentally regulate the growth of TiB2 rod-shaped crystals to obtain polycrystalline cubic boron nitride (PcBN) composites with excellent comprehensive mechanical properties. The calculation results reveal that under Ti-rich or B-rich conditions, both the surface energies of (0001) and (101̄0) are lower than the surface energy of (112̄0). The growth of TiB2 is interpreted at the atomic level as being composed of (0001) and (101̄0) surfaces, and it preferentially grows as rod crystals along the (0001) crystal plane. The calculations further indicate that the hexagonal morphology of TiB2 is determined by the atomic concentration within the melt. It exhibits a higher propensity for nucleation under Ti-rich conditions than under B-rich conditions. And it is predicted that a lower relative concentration of Ti atoms promotes the growth of TiB2 into hexagonal rod crystals. In addition, PcBN composites with TiB2 reinforced phase are synthesized in situ by modulating the Ti-Al molar ratio. The experimental results demonstrate that as the concentration of Ti atoms decreases, the nucleation of TiB2 decreases, while the growth of TiB2 rod crystals increases, which aligns with the predicted calculations. Moreover, the presence of rod crystals greatly enhances the densities and flexural strength of PcBN composites. When the Ti-Al molar ratio is adjusted to 1:2, a substantial quantity of high-quality TiB2 rod crystals are cultivated, leading to PcBN composites exhibiting outstanding mechanical properties.

Enhanced dechlorination of 2,4-dichlorophenol using nanorod palygorskite-loaded Fe/Ni nanoparticles: Performance evaluation, influencing factors and action mechanism of Fe and Ni

The basic structural unit of palygorskite (P) consists of rod-shaped crystals with a diameter ranging from 20 to 70 nm. However, due to strong hydrogen bonding and electrostatic forces, most palygorskite rod crystals tend to aggregate, limiting its nanomaterial properties in practical application. To address this limitation, the study focused on dissociating palygorskite aggregates and incorporating them into nanorod palygorskite-loaded Fe/Ni bimetallic nanoparticles (nP-nFe/Ni) synthesis. This approach facilitated the dissociation of palygorskite aggregates and enabled the dispersion of Fe/Ni nanoparticles by palygorskite nanorods. The results revealed that the BET specific surface area of nP-nFe/Ni was significantly higher at 86.17 m2/g compared to 33.62 m2/g for nFe/Ni. Consequently, the dechlorination efficiency of nP-nFe/Ni for 2,4-dichlorophenol (2,4-DCP) at 120 min was 22.4% higher than that of nFe/Ni, despite nP-nFe/Ni containing only 35.1% of the Fe content found in nFe/Ni at the same dosage. Moreover, it was observed that acidic conditions favor maximum dichlorination, while higher temperatures enhance the dechlorination rate. The action mechanism of Fe was identified as the generation of H2, which is catalyzed by Ni to form active hydrogen (H*) that attack the C-Cl bonds of 2,4-DCP for hydrodechlorination. Ni played a vital role in catalyzing H2 conversion to H* , accelerating H2 production by Fe, and inhibiting Fe passivation. These findings are crucial for the application of nano iron technology and nano-scale palygorskite in water and wastewater treatment.

INVESTIGATION OF MICROSCOPIC STRUCTURE, TRANSLUCENCY PARAMETERS, AND FRACTURE TOUGHNESS OF TWO PRESSABLE LITHIUM DISILICATE GLASS-CERAMIC MATERIALS.

To investigate the microscopic structure and fracture toughness of two pressable glass-ceramics-GC Initial LiSi Press (LiSi) and IPS e.max Press (e.max)-with different levels of translucency. Two groups each of LiSi and e.max, with medium opacity and high translucency levels, were examined. The crystal morphology of acid-etched specimens was observed under a scanning electron microscope (SEM). Six specimens in each group were fabricated in a square shape (12 ' 12 ' 1.5 mm) to measure translucency parameters (TP) using a spectrophotometer. Ten bar-shaped specimens in each group with dimensions of 23 x 2 x 4 mm were used to determine the fracture toughness (KIc) by a surface crack in flexure (SCF) using a universal testing machine. One-way ANOVA and Scheffe post-hoc tests were used for statistical analysis. LiSi showed fine dense crystals 1 to 1.5 μm in size, while e.max showed long rod-shaped crystals 3 to 4 μm in size. The TP values of all specimens coincided with their translucency levels. There was no statistical difference in the KIc between different translucency for both ceramics (P < .05). However, the KIc of e.max was significantly higher than that of LiSi at both translucency levels. As a result of larger and longer crystals, e.max provided better crack deviation mechanism to resist the fracture. Within the limitations of this study, the translucency levels of both lithium disilicate ceramics did not affect the fracture toughness of the materials. The fracture toughness of e.max was statistically higher than LiSi.

Synthesis and mesomorphic properties of novel multi-arm side-chain liquid crystal polymers with different terminal substituents

ABSTRACT In this study, two novel aromatic ester multi-arm liquid crystal monomers M 1 and M 2 with different terminal substituents centred on 3,4,5-trihydroxybenzoic acid, and a rod-shaped chiral liquid crystal monomer N were designed and synthesised. The synthesised liquid crystal monomers M and N were grafted and copolymerised with polymethylhydrosiloxane (PMHS). The structural characterisation of the synthesised liquid crystal compounds was carried out by FT-IR and 1H-NMR. The mesomorphic properties of the synthesised liquid crystal compounds were characterised by POM and DSC, and the results showed that the multi-arm liquid crystal monomers M 1 and M 2 are typical enantiotropic nematic liquid crystal compounds and N is typical thermotropic enantiotropic cholesteric liquid crystal. Polymers P 1 and P 2 are both cholesteric liquid crystal polymers. The glass transition temperatures and liquid crystal isotropic transition temperatures of polymers P 1 and P 2 series both tend to increase with the increase of multi-arm liquid crystal monomer M.

Mesomorphic property and gelation ability of rod-shaped compounds having a coumarin skeleton

ABSTRACTRod-shaped liquid crystal materials with a lactone group at the terminal position of the molecule were designed, synthesised and their mesomorphic properties in bulk state and gelation ability in several organic solvents were examined. The effects of perfluoroalkyl chain and chemical structure on liquid crystal property and gelation ability were investigated. These compounds showed smectic A phase in bulk state and gelation ability in polar organic solvents. It was found that the presence of perfluoroalkyl chain and the direction of orientation of the esters had a great effect on these properties.

&lt;sup&gt;7&lt;/sup&gt;Li Diffusion in Thin Disks of Single-Crystal Garnet LLZO-Ta Studied by PFG-NMR Spectroscopy

Pulsed field-gradient (PFG) NMR spectroscopy was applied to thin disk samples (0.5, 1 and 2 mm thick, 4 mm diameter) of LLZO-Ta (Li&lt;sub&gt;6&lt;/sub&gt;La&lt;sub&gt;3&lt;/sub&gt;Zr&lt;sub&gt;1.5&lt;/sub&gt;Ta&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt;) single crystal. We have measured the diffusion of &lt;sup&gt;7&lt;/sup&gt;Li in thin pellets (0.5 to 3 mm thick) of NASICON-type LAGP powder and found that the Li&lt;sup&gt;+&lt;/sup&gt; diffuses preferentially in the thicker direction. In this study, we placed 1 mm thick, 4 mm diameter disk-shaped single crystals vertically, i.e., parallel to the PFG direction. We found that &lt;sup&gt;7&lt;/sup&gt;Li ions diffuse similarly as in rod-shaped single crystals. The &lt;sup&gt;7&lt;/sup&gt;Li diffusion is slow (diffusion coefficient; ~2 × 10&lt;sup&gt;-13&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt;s&lt;sup&gt;-1&lt;/sup&gt;) at Δ ≥ 100 milliseconds and gradually becomes faster to ~1 × 10&lt;sup&gt;-11&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt;s&lt;sup&gt;-1&lt;/sup&gt; at Δ ≤ 10 milliseconds at 28°C. A diffraction pattern was observed in the echo decay plots, which was not observed in well-prepared single crystal rod samples. The diffraction patterns are often observed in powder inorganic electrolytes (LLZOs, LLTO, LAGP, and (Li&lt;sub&gt;2&lt;/sub&gt;S)&lt;sub&gt;x&lt;/sub&gt;(P&lt;sub&gt;2&lt;/sub&gt;S&lt;sub&gt;5&lt;/sub&gt;)&lt;sub&gt;y&lt;/sub&gt;). In this study, edge effects are assumed for the diffraction pattern of the vertically placed thin disk of the single crystal. For horizontally placed disks, at long observation times (Δ ≥ 100 milliseconds), the diffusion coefficients of &lt;sup&gt;7&lt;/sup&gt;Li agreed with those of the rod-shaped samples. However, as Δ became shorter, contrary to the vertically placed disk, the diffusion of &lt;sup&gt;7&lt;/sup&gt;Li decreased and the plots became less linear. Surprisingly, as Δ became shorter (Δ ≤ 15 milliseconds), sinusoidal patterns were observed in the real and imaginary elements of the echo attenuation plots,. The pattern is reproducible and the first example of sinusoidal real and imaginary components of the echo attenuation plot was observed, but an adequate explanation has not been obtained.

Unusual In Situ Transformation of Metastable Co-Crystal Forms into a Stable Form, in Solution and Solid State, and the [2 + 2] Photochemical Reactivity in the Crystalline Forms

Isolation of multiple composition co-crystals from a one-pot crystallization flask and in situ transformations of the crystals are not common phenomena. We describe, herein, thoroughly characterized three unusual co-crystals of citric acid (CA) and 1,2-bis(4-pyridyl)ethene (bpyee) with different molecular compositions (1:1, α; 2:2, β; and 2:3, γ) that were obtained from a one-pot crystallization flask of a CH3OH solution with equimolar co-formers. The three co-crystals can be distinguished by their morphology and appearance at various stages of the crystallization process. In the first instance, needle-shaped (β) crystals are formed on the edge of the flask, followed by plates (γ) in the bulk of the solution, and finally, the entire flask with only rod-shaped crystals (α), indicating the in situ conversion of β- and γ-forms into α-form. Interestingly, in the solid state, isolated crystals are observed to undergo conversion, but in a different way than solution growth, as characterized by in situ variable-temperature powder X-ray diffraction, with β- and α-forms converting into γ-form. Furthermore, all of the forms undergo [2 + 2] photochemical reactivity upon UV irradiation due to the favorable Schmidt’s photoreactive distance between the adjacent bpyee molecules in α- and γ-forms, with the former following a single-crystal-to-single-crystal transformation process also, while β-form, despite having bpyee molecules separated by 7.68 Å, through conversion into γ-form.

Experimental study on calcium carbonate phase transition from amorphous to crystalline forms in a reverse emulsion

Calcium carbonate (CaCO3) nanoparticles for lubricant additives are typically manufactured in reverse emulsion. The amorphous form is sterically stabilised in oil to create the so-called, ‘overbased detergents’, for motor engine oils, whilst crystalline CaCO3 nanoparticles are produced for specific applications, like lubricating greases. Here, the phase transition of amorphous calcium carbonate to crystalline forms in a reverse water/oil emulsion was studied in a 23L jacketed batch reactor equipped with agitator, temperature and pressure control. During the process, several acids, such as acetic, alkylaryl and 12-hydroxystearic (HSA), were added. The impact of acid type and HSA quantity were studied with all other aspects constant. The amorphous to crystalline phase transition kinetics were measured, the crystal habits were observed and the solid forms were characterized. With no HSA, a more acidic environment resulted in faster transition kinetics from amorphous CaCO3 to calcite. However, the presence of HSA tended to slow down the transition kinetics. Indeed, calcite crystal growth was asymmetrically inhibited by HSA, leading to elongated rod-shaped crystals. Finally, a very high HSA concentration leads to the formation of vaterite crystals, vaterite being a less stable phase than calcite.