Volume 234, Issue 5

For the first time, we determined the detailed crystal structure of Na 3 Sm(PO 4 ) 2 using single crystal X-ray diffraction and established the commensurately modulated structure model using the superspace formalism. The structure adopts a (3+1)-dimensional superspace group Pca 2 1 (0 β 0)000 with the modulation vector q=1/3b*. At the same time, the photoluminescent properties of Na 3 Sm(PO 4 ) 2 sintered at different temperatures between 800 and 1200°C were studied. Under near-UV excitation (402 nm), Na 3 Sm(PO 4 ) 2 shows intense characteristic emission bands of Sm 3+ (561, 596, 642 nm) with the CIE coordinate of (0.5709, 0.4282), corresponding to orange color. The excitation spectrum covers a wide range from 350 nm to 470 nm, which indicates that Na 3 Sm(PO 4 ) 2 can be efficiently activated by near-UV or visuable LED ship.

A new approach to the problem of coordination sequences of periodic structures is proposed. It is based on the concept of layer-by-layer growth and on the study of geodesics in periodic graphs. We represent coordination numbers as sums of so called sector coordination numbers arising from the growth polygon of the graph. In each sector we obtain a canonical form of the geodesic chains and reduce the calculation of the sector coordination numbers to solution of the linear Diophantine equations. The approach is illustrated by the example of the 2-homogeneous kra graph. We obtain three alternative descriptions of the coordination sequences: explicit formulas, generating functions and recurrent relations.

Explorations on a mixed metal phosphatoantimonate system led to the discovery of two new anhydrous phosphatoantimonates, namely, Cs 4 MSb 6 P 4 O 28 (M=Mg, Zn), which represent the first examples of quinary A I – M II –Sb V – P V – O systems. Single-crystal structure analysis reveals that the two title compounds crystallize in the tetragonal space group I 4 1 / a (No. 88). Their structures feature complicated 3D frameworks with interesting tunnel structures comprised of corner sharing MO 4 tetrahedra, SbO 6 octahedra and PO 4 tetrahedra, with the Cs + cations sitting in the tunnels to balance the valence. Optical reflectance spectrum measurements show that these two compounds are insulators with band gaps of about 4.5 eV.

Zinc oxide nanoparticles had been synthesized and encapsulated using Curcumin nanoemulsions, Zn(Cur)O NPs, under subcritical water conditions. The effects of temperature (120, 140 and 160 °C) and pH values of the reaction solution (4, 7 and 10) on the particle size, grain size, cristallinity, specific surface area, band gap, Urbach energy, morphology, photocatalytic activity and antibacterial properties of the prepared Zn(Cur)O NPs were evaluated using XRD, FT-IR, SEM, EDX and UV-Vis spectroscopy analysis. The obtained results indicate that the prepared spherical and rod shapes Zn(Cur)O NPs had a crystallite size distribution of 10–100 nm. Furthermore, the results reveal that most uniform Zn(Cur)O NPs with highest photocatalytic activity, quantum yield (0.161 mol·m −2 s −1 ), specific surface area (242 m 2 /g), minimum band gap (2.62 eV) and Urbach energy (0.125 meV) were formed at 160 °C and natural pH. The highest antibacterial activities against both Gram positive and negative bacteria strains, were achieved using the synthesized Zn(Cur)O at 160 °C and basic pH(10).

Twins in micas are difficultly identified due to mica’s hexagonal pseudosymmetry. Many theoretic studies on mica twins have been reported but experimental observations are very limited. In this paper, we present an electron backscattered diffraction analysis to identify twins in the muscovite in a quartz schist occurring in the UHP-HP metamorphic rock belt in Dabie Mountain, China. A trilling twin with twin law <310>/{110} is common in the muscovite. A six-couplet twin consisting of two trilling twins related by twin laws <110>/{130} and <001>/{001}(or <100>/{100}) has been discovered. This six-couplet twin contains many cross-twin relationships among the most common mica twin laws <310>/{110}, <110>/{130} and <001>/{001}. The composition plane for twin laws <110>/{130} and <001>/{001} is {001} which is reasonable in mica structure to form a twin by rotation around twin axes, and that for twin law <310>/{110} is irregular based on EBSD resolution. A possible misindexation of a trilling twin or a 3T polytype during EBSD test is discussed, which is helpful to distinguish a twin from a polytype in micas. The occurring frequency of twin law <310>/{110} is higher than that of twin laws <110>/{130} and <001>/{001}, which is consistent to the deducing result from mica structure analysis. This research provides a convenient and effective EBSD method to identify mica twins and an experimental method to distinguish a twin from a polytype in micas, which is a problem confusing researchers for many years.

The crystal and molecular structures of two homoleptic morpholine-derived dithiocarbamates of zinc, binuclear {Zn[S 2 CN(CH 2 CH 2 ) 2 O) 2 ] 2 } 2 ( 1 ), and cadmium, one-dimensional coordination polymer {Cd[S 2 CN(CH 2 CH 2 ) 2 O) 2 ] 2 } 2 ( 2 ), are described. In 1 , a centrosymmetric binuclear molecule is found as there are equal numbers of chelating and bidentate bridging dithiocarbamate ligands; weak transannular Zn···S interactions are found within the resultant eight-membered {···SCSZn} 2 ring which has the form of a chair. The resultant 4+1 S 5 donor set is highly distorted with the geometry tending towards a square-pyramid. By contrast, a square-planar geometry is found in centrosymmetric 2 defined by symmetrically chelating dithiocarbamate ligands. The presence of Cd···S secondary bonding in the crystal of 2 leads to a distorted 4+2 S 6 octahedron and a linear coordination polymer, which is unprecedented in the structural chemistry of cadmium dithiocarbamates. The analyses of the Hirshfeld surfaces for 1 and 2 show the dominance of H···H, S···H/H···S and O···H/H···O contacts to the surface, i.e. contributing around 90 and 80%, respectively.

Powder samples of the intermediate phase between sodalite and cancrinite (INT) have been synthesized hydrothermally. The formation of the INT phase was proved by both PXRD and TGA analysis and its stoichiometric composition was found to be |Na 6.95(1) (CO 3 ) 0.48(2) (H 2 O) 6.18(6) |[AlSiO 4 ] 6 . The comparison of the intensity ratios of PXRD data with a SCXRD measurement indicates the formation of a comparable phase with the typical strong stacking disorder. The hexagonal lattice parameters with a =1266.3(2) pm and c =1586(1) pm and the unit cell setting were determined by Pawley fits. The average lattice and the stacking disorder along c axis could be confirmed by the reconstruction of three-dimensional ADT data. The average structure of INT was modeled considering only the combination of naturally existing (zeolitic) cages, restricted by the actual number of layers per unit cell. The possible combinations were further reduced by considering the amount of incorporated species. Through the comparison of simulated electron diffraction pattern to measured data the modeled framework could be confirmed. Using relative positions of the incorporated species in the natural cages as well as electron densities calculated by using only the framework of INT the positions of these species could be described.