Synthesis of barium and strontium carbonate crystals with unusual morphologies using an organic additive

In this paper, strontium carbonate (SrCO₃) and barium carbonate (BaCO₃) crystals were synthesized in the presence of an organic additive-hexamethylenetetramine (HMT) using two CO₂ sources. Scanning electron microscopy and X-ray powder diffractometry were used to characterize the products. The results showed that the morphologies of orthorhombic strontianite SrCO₃ transformed from branch-like to flower-like, and to capsicum-like at last, while the morphologies of BaCO₃ change from fiber-like to branchlike, and to rod-like finally with an increase of the molar ratio HMT/Sr²⁺ and HMT/Ba²⁺ from 0.2 to 10 using ammonium carbonate as CO₂ source. When using diethyl carbonate instead of ammonium carbonate as CO₂ source, SrCO₃ flowers aggregated by rods and BaCO₃ shuttles were formed. The possible formation mechanisms of SrCO₃ and BaCO₃ crystals obtained in different conditions were also discussed.     

Microporous metal organic materials: promising candidates as sorbents for hydrogen storage

Advancement in hydrogen storage techniques represents one of the most important areas of today's materials research. While extensive efforts have been made to the existing techniques, there is no viable storage technology capable of meeting the DOE cost and performance targets at the present time. New materials with significantly improved hydrogen adsorption capability are needed. Microporous metal coordination materials (MMOM) are promising candidates for use as sorbents in hydrogen adsorption. These materials possess physical characteristics similar to those of single-walled carbon nanotubes (SWNTs) but also exhibit a number of improved features. Here, we report a novel MMOM structure and its room-temperature hydrogen adsorption properties.     

Microporous organic materials from hydrophobic dipeptides

In the last few years dipeptides with two hydrophobic residues (hydrophobic dipeptides) have emerged as an unexpected source of stable microporous organic materials. Supramolecular self-assembly of the rather small building blocks is dictated by stringent demands on the hydrogen-bond formation by the peptide main chains and the aggregation of hydrophobic entities in the side chains. A systematic survey of structures derived from single-crystal X-ray diffraction studies has revealed the existence of two large classes of structures, differing in the dimensionality of the hydrogen-bonding patterns in the crystals and the nature of the channels. The present review summarizes the structural properties of the microporous dipeptides and discusses their potential applications.     

Structural basis for bending of organic crystals

Bending is observed in organic crystals when the packing is anisotropic in such a way that strong and weak interaction patterns occur in nearly perpendicular directions.     

Four organic crystals displaying distinctively different emission colors based on an ESIPT-active organic molecule

Multi-colored fluorescence which covering pure K^* emission, E^*&K^* emission and pure E^* emission was obtained by controlling the preparation conditions of a simple ESIPT-active molecule.     

Aggregation-governed oriented growth of inorganic crystals at an organic template

X-ray studies performed during the growth of CdCO(3) and MnCO(3) crystals from supersaturated aqueous solutions, at fatty acid monolayer templates, reveal that the nucleates are nearly three-dimensional powders below a threshold supersaturation. However, at higher supersaturations, the crystals are preferentially oriented with the {0 1 2} direction vertical. Scanning electron microscope images of samples transferred to substrates show discrete crystals at low concentrations, while at higher concentrations the crystals self-aggregate to form linear chains and sheets. The authors speculate that preferential alignment at the organic-inorganic interface is enhanced as a consequence of oriented aggregation of crystals. The role of monolayer-ion interactions in governing the morphologies and the resulting orientation of the inorganic nucleate is discussed.     

Microporous zinc tris[(4-carboxyl)phenylduryl]amine framework with an unusual topological net for gas storage and separation

By employment of a new tris[(4-carboxyl)phenylduryl]amine ligand to assembly with the Zn(2+) ion, a new topological net built from four coordinatively linked ths nets is first evidenced in the 2-fold-interpenetrating framework FIR-1, which shows potential applications in gas storage and separation.     

Effect of doping an organic molecule ligand on TGS single crystals

Good quality single crystals of thiourea-doped triglycinesulphate (TuTGS) a new semiorganic nonlinear optical (NLO) crystal has been successfully grown from aqueous solution by slow evaporation method. The solubilities under various solvents in different proportions have been studied. The structural characterization of the grown crystals was carried out by X-ray diffraction. The grown crystals were subjected to FTIR and Raman analyses for vibrational assignments. The optical absorption coefficient alpha was analysed and interpreted to be allowed in the direct transition. The values of allowed direct energy gap (Eg) for undoped and doped crystals were calculated. It was found that Eg values were decreased with organic molecule doping. The powder technique of Kurtz and Perry confirm the NLO property of the grown crystal.     

An unusual case of indoor air radon contamination: An unusual method for effective mitigation

In the course of routine surveillance for indoor radon in Austria, concentrations above 10,000 Bq/m³ were found in a house in the province of Carinthia, Austria. Multiple 3-day-measurements in all the rooms of the house were carried out for the next 21 months. All rooms of the house had elevated radon concentrations but radon levels decreased systematically from east to west within the house. Moreover, radon concentrations in one room of the building were found to be below 300 Bq/m³ in winter but above 12,000 Bq/m³ in summer. After installing a medium sized fan, operated only during the summer season, the semiannual summer radon levels dropped from approximately 8,000 Bq/m³ to 250 Bq/m³ at ground floor level. Note: The paper reflects the personal opinions of the authors.     

Microporous organic nanotube networks from hyper cross-linking core-shell bottlebrush copolymers for selective adsorption study

We report a synthesis of microporous organic nanotube networks (MONNs) by a combination of hyper cross-linking and molecular templating of core-shell bottlebrush copolymers.The intrabrush and interbrush cross-linking of polystyrene (PS) shell layer in the core-shell bottlebrush copolymers led to the formation of micropores and large-sized nanopores (meso/macrospores) in MONNs,respectively,while selective removal of polylactide (PLA) core layer generated mesoporous tubular structure.The size of PLA-templated mesoporous cores and porous structure both at micro-and meso-scale could be controlled by simple tuning of the ratio of core/shell or the PLA core fraction in the bottlebrush precursors.Moreover,the resultant MONNs showed a highly selective adsorption capacity for the positively charged dyes on the basis of multi-porosity and carboxylate group-rich structure.In addition,MONNs also exhibited effective performance in size-selective adsorption of biomacromolecules.This work represents a new avenue for the preparation of MONNs and also provides a new application for molecular bottlebrushes in nanotechnology.     

Dynamic disorder in the crystal structure of an organic semiconductor: an unusual phase transition involving the heat capacity

(E,E)-1-[2-(4-Nitrophenyl)ethenyl]-4-[2-(2,4-dimethoxyphenyl)ethenyl]benzene was characterised by X-ray diffraction and shown to be dynamically disordered at room temperature. The structure was re-determined over a range of temperatures to infer the thermodynamic parameters related to this disorder. A phase transition of third order according to the Ehrenfest classification scheme was discovered. To the best of our knowledge, this is the first experimentally observed phase transition of formal third order. It can be explained by the involvement of long-range lattice vibrations.     

Dual-function surfactant strategy for two-dimensional organic semiconductor crystals towards high-performance organic field-effect transistors

Two-dimensional (2D) organic semiconductor crystals (OSCs) are ideal platforms for investigating fundament materials as well as achieving high-performance organ...     

A unified theory for charge-carrier transport in organic crystals

To characterize the crossover from bandlike transport to hopping transport in molecular crystals, we study a microscopic model that treats electron-phonon interactions explicitly. A finite-temperature variational method combining Merrifield's transformation with Bogoliubov's theorem is developed to obtain the optimal basis for an interacting electron-phonon system, which is then used to calculate the bandlike and hopping mobilities for charge carriers. Our calculations on the one dimensional (1D) Holstein model at T=0 K and finite temperatures show that the variational basis gives results that compared favorably to other analytical methods. We also study the structures of polaron states at a broad range of parameters including different temperatures. Furthermore, we calculate the bandlike and hopping mobilities of the 1D Holstein model in different parameters and show that our theory predicts universal power-law decay at low temperatures and an almost temperature independent behavior at higher temperatures, in agreement with experimental observations. In addition, we show that as the temperature increases, hopping transport can become dominant even before the polaron state changes its character. Thus, our result indicates that the self-trapping transition studied in conventional polaron theories does not necessarily correspond to the bandlike to hopping transition in the transport properties in organic molecular crystals. Finally, a comparison of our 1D results with experiments on ultrapure naphthalene crystals suggests that the theory can describe the charge-carrier mobilities quantitatively across the whole experimental temperature range.     

Epitaxial etching of organic single crystals

Organic single crystals(OSCs) have received increasing interest in the last decades for their potential applications in flexible electronics. Although there are various subtractive manufacturing methods of organic electronics, the subtractive manufacturing of OSCs is still a challenge, since OSCs are assembled via weak van-der-Waals interactions which are vulnerable and cannot afford damages and suffer the degradation of performances after the process. Here, we develop an epitaxial etching strat...