Crystal Solid State Research Articles

Comparison of solid-state crystallization of boron polymorphs at ambient and high pressures

Here we report the systematic study of solid-state phase transformations between boron polymorphs: α -B12, β -B106, γ -B28, T-B52 and amorphous boron (am-B). It is evident that the Ostwald rule of stages plays an important role during phase transformations not only of amorphous boron, but also of crystalline forms. We have observed the crystallization of tetragonal boron T-B52 from amorphous phase of high purity (99.99%), which, however, cannot be easily distinguished from B50C2 boron compound. Many factors influence the transformations of amorphous phase, and it is possible to observe not only well-known am-B → α -B12 and am-B → β -B106 transformations, but also am-B → T-B52, never reported so far. At ∼14 GPa, the crystallization order becomes β -B106→α -B12→γ -B28, while at ∼11 GPa the intermediate crystallization of T-B52 still was observed. This unambiguously indicates that α -B12 is more thermodynamically stable than β -B106 at high pressures (HPs) and renders possible to transform, at least partially, common β -phase of high purity into α -B12 at very HPs and moderate temperatures (below 1600 K), i.e. outside the domain of its stability.

High efficiency luminescent liquid crystal: aggregation-induced emission strategy and biaxially oriented mesomorphic structure

Rational combination of aggregation-induced emission active luminogens and mesogens generates high solid-state efficiency luminescent liquid crystals, thus resolving the problem of aggregation-caused quenching normally occurs in the fabrication of luminescent mesomorphic films.

Synthesis and properties of oxide ion conductor Pr2Mo2O9 with La2Mo2O9 structure

Polycrystalline Pr2Mo2O9 samples have been prepared by solid-state synthesis and single crystals of this compound have been grown. Pr2Mo2O9 is unstable in the temperature range 700–900°C and partially decomposes with the formation of Pr2Mo3O12 at these temperatures, but upon further heating to 1000–1050°C, Pr2Mo2O9 is recovered. At room temperature, the structure, polymorphism, and physical properties of Pr2Mo2O9 are similar to those of the known oxide ion conductor La2Mo2O9. Pr2Mo2O9 exhibits a reversible first-order phase transition to the cubic phase in the temperature range 520–540°C. The electric conductivity of Pr2Mo2O9 is close to that of La2Mo2O9 and amounts to 3.5 × 10−2 S/cm at 700°C. The conductivity of Pr2Mo2O9 is described by the Arrhenius law in the low-temperature phase and by the Vogel-Fulcher-Tammann equation in the high-temperature phase.

Solid-State Structure and Crystallization in Double-Crystalline Diblock Copolymers of Linear Polyethylene and Hydrogenated Polynorbornene

Double-crystalline diblock copolymers of linear polyethylene (LPE) and hydrogenated polynorbornene (hPN) are synthesized, and their crystallization behavior and morphology are examined using small-angle (SAXS) and wide-angle X-ray scattering (WAXS). In symmetric hPN/LPE diblocks with molecular weights above 50 kg/mol, the hPN block has previously been shown to crystallize first and set the solid-state microstructure. Two-dimensional WAXS on hand-drawn fiber specimens reveals that the LPE crystals formed in confinement stack orthogonally to the hPN crystals. By adjusting total molecular weight, the order of block crystallization may be reversed, even while holding the block length ratio fixed. At a diblock molecular weight of 20 kg/mol, simultaneous time-resolved SAXS/WAXS reveals that the LPE block crystallizes first, even when LPE is the minority component, and restricts hPN to crystallize between the LPE lamellae. The relative orientation of the LPE and hPN crystals in the lower molecular weight diblocks is examined by modeling changes in the SAXS primary peak intensity on cooling two diblocks through the hPN crystal–crystal transition, where hPN densifies as it adopts a rotationally ordered crystal structure. Only a perpendicular stacking of hPN and LPE crystals consistently yields the large reduction in primary SAXS peak intensity observed for both diblocks. Thus, even though the templating block switches from hPN to LPE as the diblock molecular weight is reduced, the orthogonal stacking motif is retained for both high- and low-molecular-weight copolymers.

Crystal growth of Cu3−xZnxMo2O9 by continuous solid-state crystallization method

A new technique that employs a temperature gradient and a mechanical drive system in an image furnace, has been developed for the solid-state crystallization. A crystal is continuously grown from a polycrystalline feed rod by scanning the heating area along the length direction using a conventional floating zone furnace. This technique differs from the floating zone method since the grain growth is realized without a melt zone. Using this technique, we have succeeded in growing large single crystals of Cu3−xZnxMo2O9, with their size reaching Ø6mm×65mm.

Effects of Carbon Atom Parity and Alkyl Side Chain Length on the Crystallization and Morphology of Biscarbamates, A Set of Model Compounds for Polyurethanes

Solid state morphology and crystallization behavior of a homologous series of biscarbamate molecules having varying alkyl side chain lengths with different carbon atom parity were investigated. These are model compounds for polyurethanes. We synthesized a set of biscarbamates with double hydrogen bonding motifs separated by a (CH(2))(6) spacer and with alkyl side chains of various lengths ranging from C(3) to C(18) at the ends. Thermal analysis showed an odd-even alternation in their melting temperatures and heats of fusion, with the odd number of carbon atoms in the side chain having higher melting temperatures and heats of fusion than the even numbered ones, in contrast to the case of n-alkanes. The effect of carbon atom parity in the alkyl side chains on the spherulite size, spherulite growth rate, and isothermal crystallization kinetics was studied. Although the spherulite size increases with the alkyl side chain length, the maximum is seen at an intermediate length and not with a short or long alkyl chain for both the odd and even series. Along this series of molecules, a maximum in spherulite size, spherulite growth rate, and rate of crystallization is seen for C(7)C(6) (odd series) and C(8)C(6) (even series) biscarbamates. There is a significant difference in spherulite size with respect to carbon atom parity in the alkyl side chains as well as sample preparation protocol. Hence the length of the alkyl side chain, carbon atom parity in the alkyl side chains, and the sample preparation protocol (i.e., quenching versus slow cooling) play an important role in the morphology of these molecules. We rationalize this behavior with the relative contributions of hydrogen bonding and van der Waals forces as discerned from IR spectroscopy. While the van der Waals interaction increases with the alkyl side chain length in this series, the hydrogen bond contribution remains invariant. The rate of crystallization follows the trend seen with the spherulitic growth. The Avrami exponent is significantly smaller than 3, varying from 1.6 to 2.5 depending on the side chain length, which indicates that the crystallization is not truly three-dimensional. This study on the influence of alkyl side chains shows that while hydrogen bonding enables self-assembly the van der Waals interactions play a significant role in the crystallization and morphology of such self-assembled structures.

Power scalability and frequency agility of compact terahertz source based on frequency mixing from solid-state lasers

We investigate power scalability and frequency agility of a terahertz (THz) source by mixing two frequencies generated by solid-state lasers in a nonlinear crystal. They are made possible by introducing two solid-state laser crystals sharing the same Q switch and output coupler with the same laser beams decoupled to each other by a polarizer. Following the optimization, we have improved the THz output power nearly fivefold at 1.64 THz. By replacing one of the neodymium-doped lithium yttrium fluoride crystals with a neodymium-doped yttrium aluminum garnet crystal, we have produced 2.1 μW at 2.98 THz.

Programming the Supramolecular Helical Polymerization of Dendritic Dipeptides via the Stereochemical Information of the Dipeptide

Many natural biomacromolecules are homochiral and are built from constituents possessing identical handedness. The construction of synthetic molecules, macromolecules, and supramolecular structures with tailored stereochemical sequences can detail the relationship between chirality and function and provide insight into the process that leads to the selection of handedness and amplification of chirality. Dendritic dipeptides, previously reported from our laboratory, self-assemble into helical porous columns and serve as fundamental mimics of natural porous helix-forming proteins and supramolecular polymers. Herein, the synthesis of all stereochemical permutations of a self-assembling dendritic dipeptide including homochiral, heterochiral, and differentially racemized variants is reported. A combination of CD/UV-vis spectroscopy in solution and in film, X-ray diffraction, and differential scanning calorimetry studies in solid state established the role of the stereochemistry of the dipeptide on the thermodynamics and mechanism of self-assembly. It was found that the highest degree of stereochemical purity, enantiopure homochiral dendritic dipeptides, exhibits the most thermodynamically favorable self-assembly process in solution corresponding to the greatest degree of helical order and intracolumnar crystallization in solid state. Reducing the stereochemical purity of the dendritic dipeptide through heterochirality or by partially or fully racemizing the dendritic dipeptide destructively interferes with the self-assembly process. All dendritic dipeptides were shown to coassemble into single columns regardless of their stereochemistry. Because these columns exhibit no deracemization, the thermodynamic advantage of enantiopurity and homochirality suggests a mechanism for stereochemical selection and chiral amplification.

Dependence of microstructures and melt behaviour of polypropylene/fullerene C60 nanocomposites on in situ interfacial reaction

Polypropylene (PP)/fullerene C60 nanocomposites, in which the interfacial reaction between two components was in situ mediated by peroxide, were prepared by a melt mixing method. Structural characterization showed that the interfacial reaction strongly affected the microstructures of PP/C60 nanocomposites at different scales, such as improving the dispersion state of C60 nanoparticles and forming long chain branched structures in which C60 acts as a branching point. This was ascribed to the ability of C60 (as a reactive nanoparticle) for preferentially trapping carbon-centred macroradicals of PP to in situ form long chain branched structures of PP on the surface of C60 during melt mixing. As a result, the shear-responsive sensitivity of the nanocomposite melts in low shear frequency regions was dramatically enhanced compared to parent PP and the nanocomposites without interfacial reaction. The nanocomposites also showed high melt strength. In addition, the transition from the melt state to solid state (crystallization process) occurred at higher temperature after the interfacial reaction between PP and C60 took place.

Solid-State Crystallization Behavior of Tetrabenzoporphyrin Organic Semiconductors

The kinetics of the solid-state conversion and crystallization of metal tetrabicycloporphyrins (M-CPs) to metal tetrabenzoporphyrins complexes (M-TBPs) were analyzed by using the Avrami-type equation, and the value of the indices (n) was found to depend on the central atom in M-CP: n = 3 for M = H (TBP), n = 2 for M = Zn, and n = 3 at low temperatures and n = 2 at high temperatures for M = Ni. The heat of crystallization was similar for the M-TBPs, but the activation energy of crystallization varied with the type of central atom. For Ni-TBP and Zn-TBP, metastable phases were first forms, which were then converted into a stable phase, while no such metastable phase was formed in the case of TBP. In addition, the crystallization behavior of TBP was different from that in the thin film state (reported previous study). The crystallization onset temperature varied with the heating rate, although the true temperatures obtained by extrapolating the different heating rates data to zero heating rate were the same. Finally, from the PXRD data, the crystal grains of M-TBPs were found to grow isotropically in the three different directions.

Reversible solid-state structural conversion between a three-dimensional network and a one-dimensional chain of Cu(ii) triazole coordination polymers in acidic/basic-suspensions or vapors

New Cu(II) triazole coordination polymers with a 3D network were synthesized and reversible structural conversion between a 3D network and a 1D chain with color change was realized by pH controlled acidic and basic-suspensions or vapors. For each conversion process of decreasing and increasing pH, conversion was accomplished with high yield, in which the crystal before conversion played the role of a solid-state crystal template.

Silver indium diphosphate, AgInP2O7

Polycrystalline material of the title compound, AgInP2O7, was synthesized by traditional high-temperature solid-state methods and single crystals were grown from the melt of a mixture of AgInP2O7 and B2O3 as flux in a platinium crucible. The structure consists of InO6 octa­hedra, which are corner-shared to PO4 tetra­hedra into a three-dimensional network with hexa­gonal channels running parallel to the c axis. The silver cation, located in the channel, is bonded to seven O atoms of the [InP2O7] framework with Ag–O distances ranging from 2.370 (2) to 3.015 (2) Å. The P2O7 diphosphate anion is characterized by a P—O—P angle of 137.27 (9) and a nearly eclipsed conformation. AgInP2O7 is isotypic with the M IFeP2O7 (M I = Na, K, Rb, Cs and Ag) diphosphate family.

Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

Microwave (MW) assisted synthesis and solid state structural characterizations of novel lithocholyl amides of 2-, 3-, and 4-aminopyridine are reported. It is shown that the MW technique is a proper method in the preparation of N-lithocholyl amides of isomeric aminopyridines. It offers many advantages compared to conventional heating. The molecular and crystal structures as well as the polymorphic and hydrated forms of prepared conjugates with their thermodynamic stabilities have been characterized by means of high resolution liquid- and solid-state NMR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Owing to the many biological functions of bile acids and amino substituted nitrogen heterocycles, knowledge of the crystal packing of these novel conjugates may have relevance for potential pharmaceutical applications.

2,9-Dibromopentacene: Synthesis and the role of substituent and symmetry on solid-state order

We have developed an effective synthetic route for 2,9-dibromopentacene, opening up new possibilities for future derivatization of pentacene. We also present the fundamental properties. Thin-film and single-crystal field-effect transistor results demonstrate a decrease in apparent charge transport efficiency with decreasing symmetry. The trend in symmetry was further correlated to single-crystal structural analysis, which implied that reduction in symmetry also reduced solid-state order. It is likely that this reduction in order is responsible for the diminished performance in the solid-state films and crystal, despite a reduction in overall tilt angle of the molecules relative to one another. Combined with previous studies, this work provides a more complete perspective on the interplay of symmetry, energetic, and intermolecular interactions in the macroscopic properties of solid-state organic electronic materials.

ChemInform Abstract: Crystal and Molecular Structures of Ring-Substituted Methyl Phenyl Sulfoxides: An X-Ray and Molecular Orbital ab initio Investigation

The solid-state crystal and molecular structure of a number of ring-substituted methyl phenyl sulfoxides, containing mainly fluorine substituents, has been obtained by X-ray analysis. The conformation found for the molecules has geometrical features very close to those of the most stable conformer(s) predicted by ab initio molecular orbital calculations. In those compounds without ortho substituents the SO bond is only slightly twisted from being coplanar with the ring plane, while a larger twist is present when both ortho positions are substituted. In the presence of one ortho substituent the SO bond adopts an anti orientation and is almost coplanar with the ring. With the unsymmetrically substituted derivatives two conformers are possible and in the case of ortho substitution the energy difference (18–24 kJ mol–1) is large enough to have crystals only of the lower energy conformer. When the ortho positions are both free, the energy difference is quite low (0.6 kJ mol–1) and both conformers are found in the same crystal.

Thin films of the Heusler alloys Cu2MnAl and Co2MnSi: recovery of ferromagnetism via solid-state crystallization from the x-ray amorphous state

X-ray amorphous thin films of the Heusler alloys Cu2MnAl and Co2MnSi have been prepared by magnetron sputter deposition at room temperature. In the amorphous state the Cu2MnAl phase is non-ferromagnetic; Co2MnSi is weakly ferromagnetic with a ferromagnetic Curie temperature of 170 K. By solid-state crystallization at high temperatures strong ferromagnetic order and high Curie temperatures are established in both alloys. The saturation magnetization of the Co2MnSi alloy reaches 5.1μB/f.u. at 4 K, corresponding to 100% of the theoretical value; for Cu2MnAl we obtain 2.8μB/f.u. at 4 K, which corresponds to 87.5% of the theoretical value. In samples of the Co2MnSi phase with optimum saturation magnetization Bragg reflections as indicators of a long-range chemical order are missing, whereas for the Cu2MnAl phase Bragg reflections confirm epitaxial quality and long-range L21 order.

Influence of magnetic field on electronic conduction of (Bi,Pb)–Sr–Ca–Cu–O granular superconductors

Granular superconductors are composed of superconducting grains between a few and hundreds nanometres in size, embedded in an insulating, semiconducting or metallic matrix. Their properties are very interesting thanks to the presence of Coulomb effects, electron tunnelling and Josephson coupling between granules. The presence of a magnetic field may cause either a decrease or increase in the material's resistivity. In this paper the electrical properties of (Bi,Pb)–Sr–Ca–Cu–O granular superconductors obtained by the solid state crystallization method were studied. The granules were in the range from 10 nm to 30 nm. All the studied materials below the transition temperature contained granules in the superconducting state. They showed positive magnetoresistance. The hopping conductivity model with the exponential temperature dependence of resistivity was applied. The obtained values of the exponents were lower than those typical for granular systems, but they increased with an increase in the magnetic field.

Control of Morphology and Orientation of a Thin Film Tetrabenzoporphyrin (TBP) Organic Semiconductor by Solid-State Crystallization

The grain morphology of tetrabenzoporphyrin (TBP) after solid-state crystallization by annealing from tetrabicycloporphyrin (CP) was found to be influenced by the annealing temperature, but the grain orientation was not significantly changed by the temperature. From the thin film XRD measurements, the b axis, which is the most favorite direction to enhance the carrier mobility, was found to grow in parallel to the substrate, but at high temperatures, the growth direction was slightly inclined from the substrate surface. The FET performance showed dependency on the annealing temperatures, showing that the carrier mobility was three times higher for the film prepared at lower temperature compared to that at higher temperatures.

A novel ZnO nanostructure: rhombus-shaped ZnO nanorod array

A facile scalable two-step approach based on a low-temperature aqueous electrodeposition and a solid-state crystal phase transformation process was developed to grow rhombus-shaped ZnO nanorod arrays which showed markedly improved hydrogen storage capacity.

First principles determination of structural, electronic and lattice dynamical properties of a model dipeptide molecular crystal

We present the results of ab initio calculations of the structural, electronic and lattice dynamical properties of the solid-state crystal of the glycyl-l-alanine dipeptide. Intramolecular bond lengths are found to be in good agreement with experimental values; lattice constants are in reasonable agreement, although it is found that discrepancies do exist. A hierarchy of hydrogen bond strengths is found, with those between (oppositely-charged) amine and carboxy functional groups being strongest. The crystal is found to be an indirect-bandgap material, with indirect bandgaps ≈4.95 eV, compared to a direct bandgap of 5.00 eV. Analysis of the electronic structure reveals that the electronic states in the near vicinity of the energy gap arise from carboxylate and amide oxygen atoms. The arrangement of both molecules and hydrogen bonds in the unit cell is found to manifest itself in increased bandwidth along specific reciprocal space directions, reflecting coupling brought about by hydrogen bonds. Determination of the zone-centre lattice dynamical behaviour permits the IR absorption spectrum to be explained. Intermolecular hydrogen bonds are found to couple intramolecular motions in adjacent moelcules, revealing the importance of an accurate treatment of intermolecular interactions, even for high-frequency vibronic modes.