A Water-Stable 2-Fold Interpenetrating cds Net as a Bifunctional Fluorescence-Responsive Sensor for Selective Detection of Cr(III) and Cr(VI) Ions

Reactions of ZnSO4∙7H2O, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, [Zn(Br-1,3-bdc)(NI-mbpy-34)]n (1), under hydro(solvo)thermal conditions. Single-crystal X-ray structure analysis revealed that 1 features a three-dimensional (3-D) 2-fold interpenetrating cds (or CdSO4) net topology with the point symbol of (65·8), where the Zn(II) centers are considered as 4-connected square-planar nodes. X-ray powder diffraction (XRPD) patterns and thermogravimetric (TG) analysis confirmed that 1 shows high chemical and thermal stabilities. Notably, 1 displayed solvent dependent photoluminescence properties; the fluorescence intensity and emission maximum of 1 in different solvent suspensions varied when a solvent was changed. Furthermore, the H2O suspension of 1 exhibited blue fluorescence emission and thus can be treated as a selective and sensitive fluorescent probe for turn-on detection of Cr3+ cations through absorbance caused enhancement (ACE) mechanism and turn-off detection of Cr2O72−/CrO42− anions through collaboration of the absorption competition and energy transfer process, with limit of detection (LOD) as low as μM scale.

A Cd(II) Luminescent Coordination Grid as a Multiresponsive Fluorescence Sensor for Cr(VI) Oxyanions and Cr(III), Fe(III), and Al(III) in Aqueous Medium

Hydro(solvo)thermal reactions of Cd(NO3)2, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, {[Cd(Br-1,3-bdc)(NI-mbpy-34)(H2O)]∙2H2O}n (1). Single-crystal X-ray diffraction analysis showed that 1 features a two-dimensional (2-D) gridlike sql layer with the point symbol of (44·62), where the Cd(II) center adopts a {CdO5N2} pentagonal bipyramidal geometry. Thermogravimetric (TG) analysis confirmed the thermal stability of 1 up to about 340 °C, whereas XRPD patterns proved the maintenance of crystallinity and framework integrity of 1 in CH2Cl2, H2O, CH3OH, and toluene. Photoluminescence studies indicated that 1 displayed intense blue fluorescence emissions in both solid-state and H2O suspension-phase. Owing to the good fluorescent properties, 1 could serve as an excellent turn-off fluorescence sensor for selective and sensitive Cr(VI) detection in water, with LOD = 15.15 μM for CrO42− and 14.91 μM for Cr2O72−, through energy competition absorption mechanism. In addition, 1 could also sensitively detect Cr3+, Fe3+, and Al3+ ions in aqueous medium via fluorescence-enhancement responses, with LOD = 2.81 μM for Cr3+, 3.82 μM for Fe3+, and 3.37 μM for Al3+, mainly through an absorbance-caused enhancement (ACE) mechanism.

Assembling the Puzzle of Taxifolin Polymorphism

A large amount of the current literature dedicated to solid states of active pharmaceutical ingredients (APIs) pays special attention to polymorphism of flavonoids. Taxifolin (also known as dihydroquercetin) is an example of a typical flavonoid. Some new forms of taxifolin have been reported previously, however it is still unclear whether they represent polymorphic modifications. In this paper, we tried to answer the question about the taxifolin polymorphism. Taxifolin microtubes and taxifolin microspheres were synthesized from raw taxifolin API using several methods of crystal engineering. All forms were described with the help of spectral methods, scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), and thermal analysis (TA). SEM reveals that the morphology of the solid phase is very specific for each sample. Although XRPD patterns of raw taxifolin and microtubes look similar, their TA profiles differ significantly. At the same time, raw taxifolin and microspheres have nearly identical thermograms, while XRPD shows that the former is a crystalline and the latter is an amorphous substance. Only the use of complex analyses allowed us to put the puzzle together and to confirm the polymorphism of taxifolin. This article demonstrates that taxifolin microtubes are a pseudopolymorphic modification of raw taxifolin.

Synthesis and Rietveld refinements of new ceramics Sr2CaFe2WO9 and Sr2PbFe2TeO9 perovskites

Ceramics of Sr2CaFe2WO9 and Sr2PbFe2TeO9 double perovskites have been prepared in polycrystalline form by solid-state technique, in the air. The crystalline structure was analyzed using X-ray powder diffraction (XRPD) at room temperature. Rietveld analysis of XRPD patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a = 5.5453(1) Å, c = 7.8389(1) Å for Sr2CaFe2WO9, and a = 5.5994(15) Å, c = 7.8979(30) Å for Sr2PbFe2TeO9. A certain degree of anti-site disordering of W and/or Te and Fe on the B –sites have been detected, indicating the presence of a partial amount of W and/or Te at Fe positions and vice versa.

Evidence of interspersed co-existing CaCO3-III and CaCO3-IIIb structures in polycrystalline CaCO3 at high pressure

New experimental data are reported on high-pressure polymorphism of CaCO3. The CaCO3-III phase was stabilized using a large-volume press device and high-resolution X-ray powder diffraction (XRPD) patterns were collected from a few mm3 of powder sample. The interpretation of XRPD indicates that CaCO3-III and CaCO3-IIIb structures are present simultaneously and are in similar proportions. The lack of any unindexed peaks demonstrates that these two polymorphs are the only phases in this experiment, indicating that CaCO3-III and CaCO3-IIIb are the structures most likely to occur above 2.5 GPa. Relevant co-axial crystallographic matrix transformations from lower-pressure polymorphs to both CaCO3-III and CaCO3-IIIb are discussed to illustrate a further possible occurrence of co-existing and interspersed stable polymorphs in carbonate systems.

Heterogeneity in iron-doped titania flower-like nanocrystalline aggregates: detection of brookite and anatase/rutile size–strain modeling

Detailed investigations of Raman spectra and X-ray powder diffraction (XRPD) patterns of rutile-rich and anatase/brookite-poor flower-like nanocrystalline aggregates of Fe-doped TiO2shed new light with regard to its microstructure and heterogeneity. The brookite phase has been detected from the Raman spectra, and the presence of different phases in pure and doped samples is discussed. The phonon confinement model (PCM) was applied to Raman spectra, and the Warren–Averbach and simplified integral breadth methods were applied to XRPD patterns in order to obtain information about the nanocrystallite size and strain of rutile and anatase. The applied methods (i.e.XRPD size–strain analysis and the PCM fit of Raman spectra), when used in combination and together with other experimental techniques like high-resolution transmission electron microscopy, could be very useful in nanomaterial characterization.

XRPD patterns of opals: A brief review and new results from recent studies

A new classification of opals through X-ray powder diffraction (XRPD) methodology, by analysing 75 new samples of opal came from different worldwide areas, is introduced. A brief historical summary of the application of XRPD analysis on opals and the most important XRPD results reported in literature were compared with the newly obtained XRPD data. A simple method for the classification of opals on the basis of their degrees of structural order-disorder calculated from the diffraction data is proposed. In addition, a clear boundary, which has not been previously described by others in literature, related to the presence (or absence) of two-peak characteristic of the cristobalite phase is identified. This boundary allows for a discrimination of opals C from CT.

Optical Properties of Porphyrin Chromophores Assembled in Nano-Lamellar Zirconium Phosphate

The supra-molecular assemblies and optical properties of the symmetrical neutral porphyrin chromophore, meso-tetra(4-pyridyl)porphine, bound to a modified α-zirconium phosphate framework have been studied. The interlayer distance of the cetyltrimethylammonium zirconium phosphate framework is 39.6 Å. After the addition of meso-tetra(4-pyridyl)porphine to the framework, the X-ray powder diffraction (XRPD) patterns show that the interlayer distance of the framework is 30.3 Å, demonstrating the formation of novel assemblies. In the framework, organic chromophores are assumed to align in a canted monolayer. The interaction of organic chromophores with the frame-work causes noticeable red shifts of the Soret absorption band from 416 to 427 nm. In contrast, the luminescence peak is blue shifted from 660 nm in aqueous media to 648 nm when mesotetra(4-pyridyl)porphine is bound to the framework. Furthermore, the emission yield of the organic chromophore in the framework is dramatically enhanced compared to that of organic aqueous solutions. The spectroscopic change of meso-tetra(4-pyridyl)porphine is ascribed to the unique microenvironments of the nano-lamellar framework. The juxtaposition of the porphyrin chromophores in the framework tunes their electronic interactions. In comparison, the organic chromophores also attempted to bind with another modified α-zirconium phosphate, n-butylammonium zirconium phosphate. However, the chromophores could not enter into n-butylammonium zirconium phosphate due to its smaller interlayer distance (18.8 Å).

Simulation of X-Ray Powder Diffraction Patterns for One-Dimensionally Disordered Crystals

Software for the simulation of X-ray powder diffraction (XRPD) patterns for ultrafine-grained materials with some kinds of imperfections has been developed. These calculations are performed on the base of the model of one-dimensionally disordered (1D-disordered) crystal [1]. Such a model can describe stacking faults (SF) and other planar defects (PD) and also finite size of coherently scattering domains. Simulated XRPD pattern is compared with experimental one and can be fitted to it. Potentialities of the software are illustrated by several examples.