• Canada
• Publicationsclose
• Crystal Growth & Design close

Although internal features of a crystal play key roles in crystal growth, the relationship between crystal struc- ture and crystal shape is still an unresolved problem. In this paper, we constructed a correlation between crystallographic structure, morphological evolution, and resultant final shape of noble metal nanocrystals. The minimal stable crystal was predicted to consist of 27 unit cells, which facilitates the growth of the crystal matrix into different shapes. During the parallel grouping process, anisotropic nanocrystal with thermodynami- callyunfavorableshapeswasobservedviathesymmetryaxisand symmetry facet. The results indicate that the formation of isotropic shapes with single or multiple twinned crystal structures are still governed by the internal order of crystal structure.

To mimic the process of gibbsite nucleation on sodium oxalate crystals and their intergrowth in alumina Bayer process, such a coprecipitation process has been broken down into three distinct stages and studied by in situ AFM and ex situ SEM under static conditions. In the first stage, a solution saturated in aluminate and supersaturated in oxalate has been used for investigating the oxalate growth on its {110} face, which is controlled by a layer-by-layer mechanism. In the second stage, in a solution saturated in oxalate and supersaturated in aluminate, gibbsite secondary nucleation was preferred along macrosteps of sodium oxalate {110} faces and appeared as two-dimensional (2D) islands with pisolitic shapes. There does not appear to be a preferred epitaxial relationship at the heterointerface between gibbsite crystals and sodium oxalate substrates, indicating that the magnitude of the surface free energy for nucleation is greater than that associated with strain energy caused by lattice mismatch. In the ...

A combined crystallographic and optical properties study offers a simple model for the dichroic behavior of crystalline azobenzene chromophores, leading to a cocrystallization strategy to manipulate their solid-state arrangement and, therewith, dichroic behavior. This supramolecular strategy represents the first entry of crystal engineering into the design of dichroism in organic crystals.

A series of π-conjugated phenyl-pyrenoimidazole (Py-Im) systems were synthesized through a one-pot condensation reaction between 4,5-pyrenedione and various benzaldehyde derivatives. The single cry...

The effects of cocoa butter (CB) origin, tempering procedure, and structure on oil migration kinetics were studied using a flatbed scanner followed by image processing and analysis. The migration rate (OMR) and migration distance (I10) of stained oil were determined in tempered and nontempered CBs. Tempered matrices had 10 to 50 times lower OMRs than nontempered CBs. In addition, the lag phase observed before significant oil migration was also significantly longer in tempered CBs (12 days vs 2 days in nontempered butters). Moreover, cocoa butter origin had a strong effect on OMR. Brazilian and Nigerian CBs had the highest OMR in both tempered and nontempered samples. Malaysian CB had the third highest OMR, but this effect was only significant in untempered samples. Finally, the lowest OMRs were found in Chinese, Ecuadorian, and Ivorian cocoa butters. The amount of oleic acid and triunsaturated triglycerides (UUU) was strongly correlated to OMR (the higher the UUU concentration, the lower the resistance to...

The ideal strength of methane hydrate and ice Ih was investigated and quantified from first-principles calculations. Using density functional theory, methane hydrate was studied under uniaxial, tri...

Indium gallium nitride films with nanocolumnar microstructure were deposited with varying indium content and substrate temperatures using plasma-enhanced evaporation on amorphous SiO2 substrates. Field emission scanning electron microscopy and X-ray diffraction results are presented, showing that more crystalline nanocolumnar microstructures can be engineered at lower indium compositions. Nanocolumn diameter and packing factor (void fraction) was found to be highly dependent on substrate temperature, with thinner and more closely packed nanocolumns observed at lower substrate temperatures. © 2010 American Chemical Society.

The Gewald reaction was used to make a 2,5-diaminothiphonene that was functionalized with two styrene monomers. It was condensed with 2,5-thiophene dicarboxaldehyde to afford a conjugated azomethin...

Ionic liquid forms of biologically active molecules (e.g., active pharmaceutical ingredients or herbicides) are often designed by using weakly interacting, conformationally flexible ions. However, crystalline forms of these molecules involve strong interactions and efficient packing. The salts of biologically active molecules may completely lack the directional supramolecular synthons typically used in crystal engineering, and thus new tools must be developed to control the crystal packing without strong directional interactions and predict their structure–property relationships in advance. The crystal structures of tetrabutylammonium and phosphonium salts of two structurally related, biologically active ions, salicylate and dicamba, show systematic differences from their free acids and metal salts, which are dominated by strong directional interactions. Molecular conformation and the structure of oligomeric ions of acids and their conjugate bases are conserved across multiple structures. The use of flexi...