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The distribution of impurities within aggregates is crucial for managing overall impurity levels and enhancing product quality. However, current detection methods often fall short to provide accurate information. This paper presents a novel fluorescence-staining method for effective solvent tagging within crystals, which can enhance impurity management. [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach based on parameter β, which equals the free volume in a unit cell normalized to the van der Waals volume of the molecules. The analysis was carried out within a cluster including two-component crystals [CF1 + CF2], in which one of the components remains constant (CF1) and the other varies (CF2). Linear correlation equations, such as β(CC) = C + D·β(CF2), linking the β(CC) parameter of the two-component crystals with the similar parameter β(CF2) of the single-component crystal for the strictly fixed temperatures were derived on the basis of the crystallographic experimental data. The coefficients of the correlation equations for different clusters were analyzed. A relationship was discovered between the correlation coefficient D and the HYBOT descriptor describing the donor and acceptor interactions with the other molecules. A graphic method was developed for analyzing the β(CC) parameter for the cocrystals belonging to the same cluster relative to the β parameter values of the individual compounds β(CF1) and β(CF2). The correlation equations derived in the study give an opportunity to evaluate the unit cell volume of a hypothetical cocrystal knowing only the crystal structure of a single-component crystal of one of the cocrystal components. [ABSTRACT FROM AUTHOR]

This paper focuses on the generation and transformation of defects associated with subsurface damages (SSDs) in seed crystals during the physical vapor transport (PVT) growth of 4H-SiC crystals. SSDs in the 4H-SiC seed crystal were first revealed and labeled through photo-chemical etching. After 30 min of PVT growth on the 4H-SiC seed crystal, we found that ridge-like substances with a height ranging from 0.2 to 1.5 μm were formed in the region above the SSDs in the 4H-SiC seed crystal. Raman spectra analysis indicated that these ridge-like substances were 4H-SiC under tensile strain. We then continued the PVT growth to obtain a 4H-SiC boule and carried out a wafering process to obtain 4H-SiC single-crystal wafers. For the bottom wafer, above the 4H-SiC seed wafer, the full width at a half maximum (FWHM) of the rocking curves of the region above the SSDs of the seed wafer was higher than that in the other regions, indicating that the SSDs degrade the crystalline quality of 4H-SiC single crystal. The average value of the FWHM of the rocking curves of the top wafer became lower than that of the bottom wafer, indicating that the effect of SSDs gradually recovers. Molten-KOH etching indicated that SSDs in the 4H-SiC seed crystal give rise to the formation of low-angular grain boundaries (LAGBs) that consist of a wall of threading edge dislocations (TEDs) in 4H-SiC single crystals. [ABSTRACT FROM AUTHOR]

In general, β-Ga2O3 films with (2¯01) out-of-orientation have been widely obtained and reported on (0001) sapphire substrates by various growth methods. In this paper, the unusual (3¯10)-oriented β-Ga2O3 films have been epitaxially grown on (0001) sapphire substrates with high crystal-quality under Ga-rich conditions by halide vapor phase epitaxy (HVPE). The out-of-plane epitaxial relationship as (3¯10) β-Ga2O3//(0001) α-Al2O3 has been confirmed by XRD and HRTEM analysis. Under most growth conditions, β-Ga2O3 films exhibit the coexistence of (3¯10) and (2¯01) out-of-plane orientation domains, and increasing the growth temperatures and HCl flow-rates can enhance the growth of (3¯10)-oriented β-Ga2O3. Off-angled (0001) sapphire substrates with off-angles (Δa) toward 〈112¯0〉 have been introduced to control the in-plane domains. It was indicated that the (2¯01)-oriented domains have been gradually eliminated with increasing the off-angles, and pure (3¯10)-oriented β-Ga2O3 films with the best crystal quality reported so far have been obtained while the off-angle was ∼7°. The decrease of the domain boundaries and defects caused by the in-plane rotational domains have led to the improvement of the crystal quality of the as-grown films. [ABSTRACT FROM AUTHOR]

As an important class of natural resources, lignin and its utilization receive more and more attention. However, it is treated as waste in paper industry and causes serious pollution of natural water bodies. Meanwhile, the uncontrollable surface topography and the crystal form of natural calcium carbonate (CaCO3) severely restrict its application in the industrial field. Biomineralization may provide a perfect solution for these two issues. In this work, two types of specific crystal forms, cinnamic acid & aragonite crystal (CAAs) and cinnamic acid & vaterite crystal (CAVs) were directly synthesized in the presence of cinnamic acid. Two kinds of polymorph states were also found in the growth process of CaCO3. The structural properties of CAAs and CAVs as well as their polymorph states were characterized by FESEM, AFM, FTIR spectroscopy, XRD and TGA. The results showed that CAAs and CAVs held the crystal forms of aragonite and vaterite, respectively. The crystal forms of CaCO3 followed the growth rule that they dynamically changed from calcite to aragonite and then to vaterite. The formation mechanism is illustrated in the nucleation and crystal growth processes of CaCO3; cinnamic acid first formed various surfaces with the change in ambient conditions. These made CaCO3 to form different crystal forms and surface structures. [ABSTRACT FROM AUTHOR]

In this paper, a tetragonal LiY(MoO4)2 single crystal with a bulk size of 23 × 20 × 18 mm3 was successfully grown for the first time by a top-seeded solution growth (TSSG) method. The full-width at half maximum of the (100) and (001) crystal wafers reached 27 and 43 arcsec, respectively. The transmission spectra show that the LiY(MoO4)2 crystal possesses a wide transparency window in the range of 0.344 to 5.493 μm. The thermal property studies indicate that the LiY(MoO4)2 crystal has a relatively large specific heat of 0.735 J/(g K). The thermal conductivity coefficients were determined to be 0.935 W m−1 K−1 and 1.047 W m−1 K−1 along the a and c axes at 30 °C, respectively. It is worth noting that the crystal exhibits a comparatively small thermal expansion anisotropy of 1.35, which indicates a relatively large laser damage threshold. [ABSTRACT FROM AUTHOR]

In this paper, a concept of establishing a uniform temperature field range and a "double-layer four-stage continuous filtration circulation system (DF-CFCS)" during crystal growth have been proposed. A high-deuterium DKDP crystal with a size of 411 mm × 433 mm × 250 mm and a weight of 51 kg has been successfully grown by a rapid-growth method. The crystal is the largest-aperture high-deuterium DKDP crystal reported so far and its deuteration rate is 99.38%. The characterization results showed that the transmittance of the DKDP crystal was about 93.88% at a wavelength of 1064 nm, the root mean square (RMS) optical uniformity was 1.51 × 10−8, the data distribution of the extinction ratio was uniform, and the bandwidth was 4.84 eV. Besides, benefiting from the proposed "DF-CFCS", the laser-induced damage threshold of the crystal was increased to 40 J cm−2 (@1064 nm, 3 ns), which is of great significance for the development of ultra-intense and ultra-short laser devices with output power ≥10 PW. [ABSTRACT FROM AUTHOR]

Hirshfeld atom refinement studies of hexachloro-cyclo-triphosphazene against high-resolution experimental data revealed the possibility of nitrogen acting simultaneously as a donor and acceptor in interactions with chlorine atoms, resulting in an NCl2 unit equivalent to the X3 synthon reported for halogen (X) bonding. This paper describes the scenarios for the NCl2 unit found in crystals, its stability analysis, and the donor–acceptor features for each case. A similar analysis is also performed for NBr2 and NI2. [ABSTRACT FROM AUTHOR]

CrystEngCommrsc. li/ crystengcomm ISSN 1466- 8033 Volume 26 Number 31 21 August 2024 Pages 4123– 4250 PAPER Anhua Wu, Liangbi Su et al. Investigation of the photothermal weak absorption and laser damage characteristics of a Nd, Y: SrF 2 crystal [Extracted from the article]

CrystEngCommrsc. li/ crystengcomm ISSN 1466- 8033 Volume 26 Number 30 14 August 2024 Pages 3991– 4122 PAPER Shuai Wang and Shenglai Wang Effect of supersaturation on structural stress of rapidly growing KDP crystals studied by wide- angle conoscopic interference [Extracted from the article]

Advances and limitations in the field of growing large, high optical quality single crystals of AgGaS2 (AGS), AgGaGeS4 (AGGS), ZnGeP2 (ZGP), LiInS2 (LIS), LiGaS2 (LGS), LiInSe2 (LISe), LiGaSe2 (LGSe) and LiGaTe2 (LGT) compounds are considered in this contribution. With attendant good optical quality, all as-grown crystals of these compounds contain always some amount of native defects which adversely affect the optical and electrical properties. With the aim of overcoming this limitation, attention in this review is focused on concepts that provide a better insight into origins of non-stoichiometry and mechanism of native point defect occurrence. Among these concepts, preference is given to effective ways of determining the scale of the non-stoichiometry through the study of T–X and P–T diagrams, to promising techniques characterizing precisely phase purity, spatial chemical inhomogeneity, and amount of microstructural inclusions in grown crystals, and to measuring thermodynamic and thermochemical properties of the compounds. Utility of physicochemical characteristics for optimizing the growing process is considered. A combination of chemical information and physical properties of crystals is obligatory for clarifying the origins of defects. Attention is given to clarifying specificity of growing Li-containing crystals caused by high chemical activity of the Li component. With such content, this review paper presents status of current knowledge of non-stoichiometry and defects of crystals demanded in practice for non-linear optics. [ABSTRACT FROM AUTHOR]

Explaining the intensification of upconversion luminescence (UCL) from a single phase NIR-upconverting (UC) crystal due to non-lanthanide dopant insertion appears challenging in the absence of proper mechanistic investigation. In this paper, through extensive synchrotron based X-ray probing, we made an attempt to understand the variations in the structural attributes of UC crystals generated through non-lanthanide ion doping. The structures of the NaYF4/Yb3+/M3+ (M3+ = Er3+/Tm3+) UC crystals doped with different Li+ concentrations were primarily investigated using Rietveld refinement analysis from synchrotron X-ray diffraction (SXRD) and supported with absorption data (XAFS), where necessary. The structural investigation was also supported by TEM, HRTEM, XANES, FT-IR and Raman spectroscopy. Rietveld analysis revealed that all the generated Li+ doped NaYF4 crystals belong to the P6 space group. Most of the Li+ ions were found to be localized in octahedral voids and lattice positions, simultaneously, in the P6 crystal structures. The overall study showed that the change in the UCL intensity behavior with Li+ incorporation could not be predicted from the lattice parameters, morphology or the particle size variation. A detailed XAFS study rather suggested the possible existence of local lattice disorder, which was found to be reflected in terms of lattice strain obtained from Williamson--Hall analysis, irrespective of the activator ions. The remarkable coherence between the variation trends of UCL intensity and lattice strain indicated that the perturbation of the local symmetry field is in some way connected with the local disorder that may not always manifest through average structural attributes like lattice parameters. [ABSTRACT FROM AUTHOR]

2,4-Dichlorophenoxyacetic acid (2,4-D) is a kind of plant growth regulator which exhibits hormesis effects at low dosages, while high dosages adversely affect the exposed organisms and act as herbicide. 2,4-D has low solubility, therefore, it is a good candidate for crystal engineering research to improve its solubility. This paper presents the preparation of five new multicomponent crystals of 2,4-D, including three salts with imidazole (IMZ), 2-aminopyridine (AAP), and 3-aminopyridine (BAP), and two cocrystals with isonicotinamide (ISO) and pyrazinamide (PYM) as coformers (CCFs). The five multicomponent crystals were first characterized by single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Molecular interactions, crystal packing, and structure similarity analyses performed using Hirshfeld surface and CrystalCMP confirmed the charge-assisted H-bonding sites and structural similarity among the solved crystal structures. The stability tests show that all five multi-component crystals exhibit excellent stability within 12 weeks under accelerated storage conditions (40 °C and 75% RH). Moreover, all the five multicomponent crystals of 2,4-D exhibit increased solubility, especially (2,4-D)+(IMZ)− that increased the solubility of the resulting salt by 70 times compared to the free acid 2,4-D. From the perspective of single-crystal structure and intermolecular interaction, the reasons for these changes in physical and chemical properties are further clarified. [ABSTRACT FROM AUTHOR]

Photomechanical molecular crystals are a family of mechanically responsive materials that have been recognized as a novel type of actuator. The actuation properties of photomechanical crystals should be characterized. However, deflection and force, which are crucial for actuators, are dependent on experimental conditions such as light intensity and crystal size, and thus the number of combinations under different conditions is infinite. This causes difficulty in obtaining the relationship between the experimental conditions and actuation outputs. To solve this problem, this paper presents a machine learning-based regression approach for modeling the deflection and force of a photo-bending crystal. The deflection and force were experimentally measured for various light intensities and crystal sizes. These time-series data of deflection and force were represented by feature values via exponential fitting for bending and unbending processes. The features of the maximum value and speed of deflection and force were analyzed by polynomial regression and variable selection. Through this process, the most fitted models were constructed for deflection and force and most of them were interpreted by material mechanics. This statistical strategy will potentially be applied to control or optimize other functions of stimuli-responsive crystals. [ABSTRACT FROM AUTHOR]

For the hybrid organic–inorganic perovskites with the general formula of A2MIIX4 (A = methylammonium; MII = Mn, Cu and Co; X = Cl), the arrangement of metal ions and organic ligands leads to a delicate balance of space, spin and charge, which results in diverse properties. In this paper, we reported a group of hybrid organic–inorganic perovskite single crystals of (CH3NH3)2MnCl4, (CH3NH3)2CuCl4 and (CH3NH3)2CoCl4 grown by a simple solution evaporation method. Magnetic measurements show that all the single crystals display magnetic ordering at low temperature. Our results reveal a novel group of hybrid organic–inorganic magnetic perovskites. [ABSTRACT FROM AUTHOR]

Over the past several decades, halogen bonding has become a standard 'tool' in supramolecular chemistry and particularly in crystal engineering. Traditionally, the study of halogen bonding has primarily been focused on organic materials, but lately there has been a constant increase in interest for halogen-bonded metal–organic materials. Numerous reports and reviews dealing with halogen bonding in single-component metal–organic solids and metallate salts have been published to date. In contrast, the design of multi-component crystals involving neutral metal–organic complexes and/or neutral halogen bond donors as building blocks has been much less explored. The purpose of this paper is to give an overview of the current advances in the preparation of halogen-bonded metal–organic multi-component solids, including salts, cocrystals comprising neutral constituents as well as cocrystals comprising ionic constituents. In doing so, we shall outline the general design strategies which can be employed in the design of such materials, and suggest possible directions for further research in this fascinating field. [ABSTRACT FROM AUTHOR]

Perovskite-structured ABX3 halides are one of the most promising families of materials with many potential applications. However, the controllable growth methods of their crystal facets and the corresponding synthetic chemistry have not yet been resolved. In this paper, we report a ligand substitution strategy for the facet-tunable growth of perovskite structure KMF3 (M = Mg, Mn, Co, Ni and Zn) fluorides under mild hydrothermal conditions. The competition of the strong ligand of NH3 and weak ligand of F− in the octahedral crystal fields of M2+ results in different facet evolution routes for KMF3 samples with the M-site of empty-, partially- or fully-filled 3d orbitals. Although X-ray diffraction results indicated that all five KMF3 compounds are crystalized into the same space group (Pm3m, no. 221), the crystal shape of KMF3 with M = Mg, Mn, Co and Ni evolved from cubic shape to edge-truncated chamfer box shape, while KZnF3 evolved from cubic shape to corner-truncated cubic shape under the same set of synthetic conditions. The cubic shape habitat morphology of KMF3 crystals is enclosed by {100} facets, chamfer box {100} and {110} facets, and corner-truncated cube {100} and {111} facets. The crystal shape formation mechanism was analysed based on ligand field theory and the Bravais–Friedel–Donnay–Harker (BFDH) theory. We expect that the shape controllable synthetic method can benefit the growth of other halide material crystals, and the shape tunable crystals can find more important applications. [ABSTRACT FROM AUTHOR]

In this paper, the fundamental information on interactions in systems concerning nanocrystalline gold disperses on the shaped (octahedron-like or cube-like) Ce1−xYbxO2−x/2 (x = 0 or 0.1) support has been discussed. Four types of Au/Ce1−xYbxO2−x/2 systems with different morphology and defect level of support have been investigated. It was observed that the microstructure and structural features of the support crystals play a key role in the reaction of CO oxidation catalysed by Au/Ce1−xYbxO2−x/2 materials. The divergent influence of Yb3+ dopant on the CO reaction as a function of exposing planes of the support was observed for Ce1−xYbxO2−x/2 and Au/Ce1−xYbxO2−x/2 systems. For the undecorated oxides, the presence of Yb3+ ions in the ceria matrix increased the activity of the octahedron-like oxides, but decreased it for the cube-like ones. On the other hand, the positive effect of the Yb-dopant on the reactivity of Au/Ce1−xYbxO2−x/2 systems was observed for both morphologies. [ABSTRACT FROM AUTHOR]

It is difficult to control the stability of the 4H polytype in the growth of SiC single crystals by the PVT method. When the crucible was immovable, it was found that the temperature and the temperature gradient of the growth interface gradually increased and were almost unchanged with the crystal growth by the simulation. This resulted in the segregation of the gas composition and a variable Si/C ratio of the growth interface, due to which polytype inclusions and defects were easily formed. In this paper, we proposed a new method for stabilizing the 4H polytype of the SiC crystals by controlling the temperature field of the growth interface and gradually moving up the graphite crucible during crystal growth. The simulation results showed that the method could simultaneously reduce the range of the temperature rise and drop the temperature gradient at the growth interface. Thus, the gas phase composition was stable during the growth process, which will be useful for the stability of the 4H polytype. Finally, 4 inch SiC single crystals with 4H polytype stability and low defects were successfully obtained though this new method. Also, the quality of the as-grown SiC crystals was characterized by X-ray diffraction, Raman spectroscopy and Candela optical surface analysis. The results show that the method of slowly moving up the crucible during crystal growth is very effective in controlling the 4H polytype and improving the quality of SiC single crystals. [ABSTRACT FROM AUTHOR]

This study explores the fine structural details of the boundaries between the growth micro-sectors in a leucosapphire (pure corundum, α-Al2O3) crystal grown hydrothermally on a nonsingularly oriented (011̅2̅) seed. Numerous lamellae along the basal planes of corundum formed on the boundaries of the growth micro-sectors; the thickness of the lamellae ranges from 10 to 30 nm with a length of up to 10 μm. They are composed of an aluminum oxyhydroxide phase, best approximated by the boehmite structure compressed along the c axis by 17% of the initial value of parameter c and stretched along the a and b axes by 12 and 6%, respectively, and therefore called boehmite′. Boehmite′ of the lamellae is epitaxially intergrown with the host leucosapphire (0001)C‖ (020)B′. In some lamellae, boehmite′ undergoes a subsequent partial or full topotaxial transformation into corundum, in a twinned or identical orientation with respect to the leucosapphire host. The trigger for this retrograde transition is partial dehydration and reduction of local tensions around the lamellae. Comparison of the results with IR spectroscopic data on synthetic leucosapphire and ruby, grown under identical conditions, showed a complete analogy of sets of absorption lines in the stretch-oscillation region of OH groups. This paper analyses the differences in the internal structure of crystals of both varieties of corundum. [ABSTRACT FROM AUTHOR]

The article presents an information page of a crystals engineering journal and abstracts of papers included in the journal. The abstracts are on topics including a paper on the molecular structure of resorcinarene-based cavitands, a paper on the synthesis of two crystalline supramolecular polypseudorotoxanes, and a paper on the structure of a polymorph of sodium benzoate.

Energetic materials that can store and rapidly release large amounts of chemical energy on demand play a vital role in both military and civilian fields. Modern energetic materials should have high density, high heat of formation and possess molecular stability that allow them to be manufactured, stored and handled safely. Recently, cocrystallization technology offers a promising platform for energetic materials to achieve a desired balance between high detonation performance and low sensitivity. This paper highlights recent developments of energetic cocrystals and details intermolecular interactions, physical parameters and detonation properties. The major part of the discussion relates to the different types of energetic cocrystals including cocrystals composed of energetic molecules and solvents, 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20)-based cocrystals and azole-based cocrystals, et al. In addition, resonant acoustic mixing (RAM) technique, bead milling and spray flash evaporation technique are also introduced as means for large-scale production of nanosized energetic cocrystals. [ABSTRACT FROM AUTHOR]

The paper reports the relationship between single-walled carbon nanotube (SWNT) doping and capsulate crystal structure in RbxAg1−xI@SWNT composites. The structures of one dimensional (1D) RbI, AgI and RbAg4I5 crystals inside single-walled carbon nanotubes were established by high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy (HAADF HRSTEM), and confirmed by image simulation. Opposite to one-dimensional RbI and AgI, inheriting the structure of bulk analogues, 1D RbAg4I5 forms a new phase within a confined space of the SWNT channel, which differs from the bulk RbAg4I5 structure and can be described by a deformed cubic 1D lattice. X-ray absorption, XPS, optical absorption and Raman spectroscopies were used for comprehensive study of the composites' electronic structures. The study reveals the donor behavior of RbI capsulate and the acceptor behavior of RbAg4I5 and AgI. Quantification of doping levels indicated the prevalence of the effect of the chemical composition of the capsulate on the overall doping efficiency, while a structural effect is mostly prominent in potential distribution on nanotube walls and partial charges on SWNT atoms. [ABSTRACT FROM AUTHOR]

In this paper, tannic acid (TA) was used to assist the fabrication of spherically aggregated Cu2O–TA hybrid sub-microparticles with good chemical stability and controllable sizes. TA exhibited multiple functions in the synthesis: the reductant for the formation of Cu2O crystal seeds, the stabilizer of the primary Cu2O crystals and the protector against the oxidation of Cu2O. A probable mechanism was presumed, including 1) seed formation and TA encapsulation, 2) primary crystal nucleation and growth, and 3) aggregation into spheres. We found that pH played a key role in determining the final morphology of the product while the precursor concentration strongly influenced the size of the particles. At a suitable pH, hierarchically structured Cu2O–TA sub-microspheres with nanocrystals as building blocks were produced. The size of the spheres can be tuned from 130 to 670 nm by adjusting the precursor concentration. Cu2O–TA hybrids exhibited excellent chemical stability against water and oxygen. The method reported here possessed many advantages like cost-effectiveness, facility of preparation, environmental friendliness, chemical stability and excellent adjustability. The properties of the prepared Cu2O particles might facilitate their applications in marine antifouling paints, adsorption materials and antibacterial agents. [ABSTRACT FROM AUTHOR]

Energetic materials that can store and rapidly release large amounts of chemical energy on demand play a vital role in both military and civilian fields. Modern energetic materials should have high density, high heat of formation and possess molecular stability that allow them to be manufactured, stored and handled safely. Recently, cocrystallization technology offers a promising platform for energetic materials to achieve a desired balance between high detonation performance and low sensitivity. This paper highlights recent developments of energetic cocrystals and details intermolecular interactions, physical parameters and detonation properties. The major part of the discussion relates to the different types of energetic cocrystals including cocrystals composed of energetic molecules and solvents, 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20)-based cocrystals and azole-based cocrystals, et al. In addition, resonant acoustic mixing (RAM) technique, bead milling and spray flash evaporation technique are also introduced as means for large-scale production of nanosized energetic cocrystals. [ABSTRACT FROM AUTHOR]

This is a commentary on a paper by S. Aitipamula et al. (CrystEngComm, 2009, 11, 1823–1827) on the detailed analysis of the stability of trimorphic cocrystals involving two pharmaceutically active substances, ethenzamide and gentisic acid. [ABSTRACT FROM AUTHOR]

The photocatalysis, chromism, and sensing capabilities of nanostructured tungsten oxides, such as tungsten trioxide (WO3), its suboxides (WOx, 0 ＜ x ＜ 3) and hydrates (WO3·nH2O, n = 1/3 (0.33), 0.5, 0.75, 1, 2, etc.), tungsten bronzes MxWO3 (M = Li, Na, K, Rb, Cs and NH4), and metal tungstates (such as Bi2WO6 and CuWO4) have attracted much attention. To improve these properties, many strategies have been pursued, such as morphology control, doping, and heterostructuring. Crystal facet engineering has recently become a very important method of fine-tuning the physicochemical properties of semiconductors. The photocatalytic reactivity of a photocatalyst is significantly affected by its surface environment, including its surface electronic and atomic structures, which strongly depend on the crystal facets. It is believed that crystals with different exposed facets will have different properties, with the exposure of highly activated facets enhancing the photocatalytic and sensing properties. This article describes the syntheses of 2D WO3 crystals with the {002} facet primarily exposed, octahedral WO3 or WO3·nH2O with exposed {111} facets, and WO3 films with dominant orientations, such as orientation along the {002} facet. WO3 doping, WO3-based heterostructuring and their applications are also presented in this paper. [ABSTRACT FROM AUTHOR]

(CoxNi1−x)0.85Se nanostructures (NSs) with different shapes (i.e., sheet-like, flower-like, and urchin-like) were synthesized by a sacrificial template method. As far as we know, this paper may be the first work that used (CoxNi1−x)0.85Se NSs as catalysts for reduction of 4-nitrophenol (4-NP) by NaBH4 in aqueous solution. [ABSTRACT FROM AUTHOR]

In this paper, carboxyl graphene (GO-COOH) sheet matrices, which are heavily oxygenated and are similar to the organic matrices of molluscs, were used to construct nacre-like layered structures. The results showed that the surface of the hybrids was smooth and the cross section had a multilayer structure. Both the surface and the interlayer of the composite material generated calcium carbonate (CaCO3) crystals. Furthermore, the spontaneity of the layered structure was found to be closely related to the concentration of the CaCO3 crystals in which high concentration could inhibit the process, highlighting the determining role of the CaCO3 concentration. To better understand the mechanisms for the formation of the layered structure, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectrometry (FT-IR) were employed. This work presents an efficient and controllable way to construct nacre-like layered hybrid structures and also has great potential for promoting the application of GO-COOH in biomedical engineering, especially in the field of biomimetic materials. [ABSTRACT FROM AUTHOR]

Mechanochromic luminescence via grinding-induced crystalline-to-amorphous transition in some organic materials has been well illustrated in recent years. Here, we focus on the luminescence reversion process induced by thermal annealing crystallization of a series of tetraphenylethene analogues. Through paired comparisons, we disclosed that the mechano-stimuli can not only destroy the crystallinity of crystalline materials but can also bring a significant effect on the amorphous-to-crystalline transition of amorphous materials. That is, only when an amorphous material underwent mechano-stimuli can it crystallize by thermal annealing to recover its emission. This grinding-facilitated annealing crystallization is rationalized to originate from the twisted and rotatable intramolecular conformation that can be altered by mechano-stimuli. Besides some special usage of the material as security paper or latent memory medium, the study presents new strategies to control the crystallization of organic semiconductors. [ABSTRACT FROM AUTHOR]

Crystal materials with integrated functionalities are desirable for the miniaturization of future optical devices. In this paper, nonlinear optical crystals of Ca3TaGa3Si2O14 (CTGS) and Nd doped CTGS (Nd:CTGS) were grown using the Czochralski pulling method and explored for self-frequency-doubling applications. Based on the refractive indexes, the optimum phase matching directions for CTGS crystals were determined for type I (38.7°, 30.0°) and type II (61.1°,0°) orientations, with respective effective nonlinear optical coefficients on the order of 0.44 pm V-1 and 0.34 pm V-1. Self-frequency-doubling was realized in Nd:CTGS crystals [(38.7°, 30.0°) (type I)] for the first time, and 18.8 mW laser power at 533 nm was achieved. [ABSTRACT FROM AUTHOR]

MgO doped near stoichiometric LiNbO3 (MgOSLN) crystals have great potential for use in periodically poled structured LiNbO3 (PPLN) for doubling frequency lasers and optical parametric oscillation infrared lasers, because of their high optical damage threshold, single domain characteristics, and very low coercive field. However, few MgOSLN crystals are commercially available in the present market because of the great difficulty in growing them. This paper describes how a hanging crucible Czochralski technique with a newly-designed ship lockage type powder feeding system assisted by numerical simulation was developed for the successful growth of high quality near stoichiometric LiNbO3 (SLN) and MgOSLN (~1 mol%) crystals. The physical properties of the crystals were assessed by measuring their crystallinity, Curie temperature, optical properties, coercive field and thermal properties. These properties, including a coercive field of 1.4 kV mm-1 and a thermal conductivity of 6.61 W (m K)-1 demonstrated that the crystals meet the demands for manufacturing periodically poled crystal devices. This growth method has great potential in the mass production of SLN and other incongruently melting crystals. [ABSTRACT FROM AUTHOR]

The main aim of the studies in this paper is to gain knowledge on the path of structural transformations resulting from the photocyclization in 2-tert-butylphenylphenylmethanone crystals at low and high pressures and also to carry out a comparative analysis of the results at different pressures. This work is the first example of these types of studies in scientific literature. We determined the structure of: pure reactant crystals, i.e. only containing reactant molecules, at 0.1 MPa, 0.55 GPa, 1.27 GPa and 1.50 GPa; pure product crystals, i.e. only containing product molecules, at 0.55 GPa and 1.27 GPa; and partly reacted crystals (ten structures), i.e. containing both reactant and product molecules in various proportions to each other, at 0.1 MPa (two structures), 0.55 GPa (three structures), 1.27 GPa (three structures) and 1.50 GPa (two structures). The studies have shown that (a) there is no phase transition when an increase in pressure is imposed onto the crystals, (b) the unit cell parameters change non-linearly with an increase in pressure, (c) the photochemical reaction was conducted in a homogeneous manner in the examined crystals, (d) the reaction brings about different modes of changes in the unit cell parameters at different pressures (e) the reaction proceeds faster at the end rather than at the beginning regardless of the pressure imposed onto the crystals. [ABSTRACT FROM AUTHOR]

The triazoylketone discussed in this paper crystallises from racemic solutions as a conglomerate. Here, we report the ternary phase diagram confirming the conglomerate behaviour of this molecule. Through computation we also explore the underlying reasons for the absence of a racemic compound in this system and the evident epitaxial crystallisation leading to crystals of almost racemic compositions but which retain the crystal structure of the pure enantiomer. [ABSTRACT FROM AUTHOR]

In this paper, the fabrication and detailed evolution process of self-assembled Au droplets on diverse GaAs type-B (n11) substrates, where n is 9, 7, 5, 4, and 2, are successfully demonstrated. The evolution process is systematically investigated by variation of the annealing temperature (Ta) from 250 to 550 °C. Self-assembled Au clusters begin to nucleate at 300 °C, and wiggly nanostructures with connected geometry are formed as a transitional stage at 350 °C. Between 400 and 550 °C, self-assembled Au droplets are successfully fabricated, and they show increased average dimensions and decreased density with increasing Ta, while showing improved size uniformity above 500 °C. Throughout the Ta range, the properties of the resulting Au droplets depend on the substrates utilized, and this is systematically analyzed in relation to the root mean squared (RMS) roughness. [ABSTRACT FROM AUTHOR]

Supramolecular structures, with ever increasing size ranging from a few up to tens of nanometres, represent an intermediate stage between small molecules and biological macromolecules. Many crystal structures of these large supramolecular assemblies have been solved using dual space algorithms. However, supramolecular assemblies with a capsular shape present a particular challenge for crystallography, especially when they are chiral and composed of only light atoms. In this paper, we show that the application of "routine" macromolecular tools may be of great help in solving the crystal structures of supramolecular assemblies that are otherwise refractory to the routine methods of small molecule crystallography. Specifically, we have applied the method of molecular replacement as implemented in PHASER in order to solve the crystal structure of a chiral organic capsule, which could not be determined using direct or dual space methods. By utilizing various models consisting of well- defined supramolecular "bricks" or modelled structures, we show how model size (fraction of the asymmetric unit) and quality (root mean square deviation from target) influence the success rate of medium sized non-protein structures. The results indicate that supramolecular structures, that are still "small molecules" for macromolecular standards, can be successfully solved using even very small models, down to 25% by weight of the contents of the asymmetric unit. [ABSTRACT FROM AUTHOR]

Single domain relaxor-PT crystals are important from both fundamental and application viewpoints. Compared to domain engineered relaxor-PT crystals, however, single domain crystals are prone to cracking during poling. In this paper, based on the analysis of the cracking phenomenon in [001] poled tetragonal 0.25Pb(In0.5Nb0.5)O3-0.37Pb(Mg1/3Nb2/3)O3-0.38PbTiO3 (PIN-PMN-PT) crystals, the non-180° ferroelastic domain switching was thought to be the dominant factor for cracking during the poling process. A high temperature poling technique, by which the domain switching can be greatly avoided, was proposed to achieve the single domain relaxor-PT crystals. By this poling approach, a quasi-single domain crystal was obtained without cracks. In addition, compared to room temperature poling, the high temperature poled PIN-PMN-PT crystals showed improved electromechanical properties, i.e., a low dielectric loss, a low strain-electric field hysteresis and a high mechanical quality factor, demonstrating a beneficial poling approach. [ABSTRACT FROM AUTHOR]

Nanoindentation is a technique which can be used to measure the mechanical properties of materials with high precision, even when they are only available in small quantities. As a result of this, nanoindentation has gained the attention of the crystal engineering community, who are not only interested in measuring the properties of single crystals of organic, inorganic and hybrid structures, but also wish to correlate the measured responses with the underlying structural features and intermolecular interactions. Keeping this emerging interest in view, a brief overview of the technique, with particular emphasis on the procedures for conducting experiments and analyzing the resulting data, is presented in this Tutorial style Highlight. The precautions that need to be taken and the properties that one can measure using nanoindentation are highlighted. This paper ends with a brief summary of the recent additional features that have been added to this technique and an outlook for nanoindentation within the context of crystal engineering. [ABSTRACT FROM AUTHOR]

Lu2Ti2O7 nano-plates are successfully synthesized via a molten salt technique and first reported in this paper. The as-prepared Lu2Ti2O7 nano-plates are actually composed of single crystals with a typical cubic fluorite structure. The diameters of the fabricated Lu2Ti2O7 nano-plates range from 500–1000 nm with thicknesses up to several tens of nano-meters. The possible growth mechanism is suggested as ‘shape memory effect’, which is weakened significantly by the substitution Lu2O3 for Lu(NO3)3. Finally, we systematically investigate the photoluminescence properties of Lu2Ti2O7 nano-particles with various morphologies. [ABSTRACT FROM AUTHOR]

In this paper, GaN films were grown on an H3PO4etched MOCVD-GaN/Al2O3template (EMGA) by hydride vapor phase epitaxy (HVPE). The GaN film grown on the EMAG template showed a smaller full width at half maximum (FWHM) of the (002) and (102) reflections in the XRD measurement than that grown on the MOCVD-GaN/Al2O3(MGA) template. A stronger PL band edge emission was observed for the GaN grown on the EMGA template compared to the MGA template. Defect related yellow luminescence was observed for GaN grown on the MGA template, which did not appear for the EMGA template. The Raman results showed that the stress of the GaN grown on the EMGA is much smaller than that on the MGA template. The penetrated etch pits played an important role in the reduction of threading dislocations. These results indicate that the quality of the GaN films is improved by using an EMGA template. [ABSTRACT FROM AUTHOR]

The preparation of large MCM-41 single crystals as well as their controllable morphologies has very important meanings not only for their potential applications but also for the exploration of the new morphogenetic mechanism for some special mesoporous crystals. In this paper, a novel crystal form of hexagonal circular bicone of MCM-41 crystal, which is the combination form of thee hexagonal bipyramid and circular bicone forms, has been observed. The MCM-41 single crystals which originally remained the same can grow larger to nearly ∼10 micron viamultiple-growth in extremely diluted ammonia solution, and were characterized by SEM, POM, TEM, XRD etc.The morphology of the MCM-41 crystal can also be controllably modulated by adding alkali salts to the synthetic system. Increasing the concentration of KCl can cause the aspect ratio and the conical angle to increase consistently and the result displays monotonicity with a certain statistical deviation. A fluctuation effect has an influence on the surface energy and eventually leads to the evolution from a single crystal to one with non-crystalline characteristics. [ABSTRACT FROM AUTHOR]