The kesterite–stannite structural transition as a way to avoid Cu/Zn disorder in kesterites: the exemplary case of the Cu2(Zn,Mn)SnSe4

The solid solution series between Cu2ZnSnSe4, crystallizing in the kesterite type structure, and Cu2MnSnSe4, adopting the stannite type structure, i.e. Cu2(Zn1−xMnx)SnSe4, was studied by a combination of neutron and X-ray powder diffraction. Powder samples with 0 ≤ x ≤ 1 were synthesized by the solid state reaction of the pure elements and it was confirmed by wavelength-dispersive X-ray spectroscopy that each contained a homogeneous, off-stoichiometric quaternary phase. The lattice parameters and cation site occupancy factors were determined simultaneously by the Rietveld analysis of the neutron and X-ray powder diffraction data. The refined site occupancy factors were used to determine the average neutron scattering length of the cation sites in the crystal structure of the Cu2(Zn1−xMnx)SnSe4 mixed crystals, from which a cation distribution model was derived. For the end member Cu2ZnSnSe4, the disordered kesterite structure was confirmed and for Cu2MnSnSe4, the stannite structure was confirmed. The cross-over from the kesterite to stannite type structure by Zn2+ ↔ Mn2+ substitution in the Cu2Zn1−xMnxSnSe4 solid solution can be seen as a cation re-distribution process among the positions (0, 0, 0), (0, ½, ¼) and (0, ¼, ¾), including Cu+, Zn2+ and Mn2+. The Sn4+ cation does not take part in this process and remains on the 2b site. Moreover, the cross-over is also visible in the ratio of the lattice parameters c/(2a), showing a characteristic dependence on the chemical composition. The order parameter Q, the quantitative measure of Cu/BII disorder (BII = Zn and Mn), shows a distinct dependence on the Mn/(Mn + Zn) ratio. In Zn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals, the order parameter Q ∼ 0.7 and drops to Q ∼ 0 (complete Cu/BII disorder) in the compositional region 0.3 ≥ x ≥ 0.7. In Mn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals, adopting the stannite type structure, the order parameter reaches almost Q ∼ 1 (order). Thus, it can be concluded that only Mn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals do not show Cu/BII disorder. A similar trend of the dependence on the chemical composition of both Cu/BII-disorder and the band gap energy Eg in Cu2(Zn1−xMnx)SnSe4 mixed crystals was observed

Abnormalities of the Umbilical Cord

Abnormalities of the umbilical cord, related to morphology, placental insertion, number of vessels and primary tumors, can influence the perinatal outcome and may be associated with other fetal anomalies and aneuploidies. The chapter investigates the most important congenital anomalies of this structure. Single umbilical artery appears to be associated with ventricular septal defects and conotruncal anomalies, hydronephrosis, dysplastic kidneys, esophageal atresia, spina bifida, holoprosencephaly, diaphragmatic hernia, and cystic hygromas. Velamentous insertion of the cord can be associated with trisomy 21, spina bifida, ventricular septal defects, and esophageal atresia. A hypoplastic umbilical artery has an artery-to-artery diameter difference of more than 50%; described anomalies include trisomy 21, polyhydramnios, congenital heart disease, and fetal growth restriction. Pseudocysts are more common than true cysts, and they are strongly associated with chromosomal defects and other congenital anomalies, especially omphalocele, hydrops, and trisomy 18. Other benign masses are teratomas, angiomyxomas, and patent urachus. Alterations in morphology and ultrastructure of the umbilical cord should extend the investigation, since there are associations with chromosomal anomalies

The kesterite stannite structural transition as a way to avoid Cu Zn disorder in kesterites the exemplary case of the Cu2 Zn,Mn SnSe4

The solid solution series between Cu2ZnSnSe4, crystallizing in the kesterite type structure, and Cu2MnSnSe4, adopting the stannite type structure, i.e. Cu2(Zn1−xMnx)SnSe4, was studied by a combination of neutron and X-ray powder diffraction. Powder samples with 0 ≤ x ≤ 1 were synthesized by the solid state reaction of the pure elements and it was confirmed by wavelength-dispersive X-ray spectroscopy that each contained a homogeneous, off-stoichiometric quaternary phase. The lattice parameters and cation site occupancy factors were determined simultaneously by the Rietveld analysis of the neutron and X-ray powder diffraction data. The refined site occupancy factors were used to determine the average neutron scattering length of the cation sites in the crystal structure of the Cu2(Zn1−xMnx)SnSe4 mixed crystals, from which a cation distribution model was derived. For the end member Cu2ZnSnSe4, the disordered kesterite structure was confirmed and for Cu2MnSnSe4, the stannite structure was confirmed. The cross-over from the kesterite to stannite type structure by Zn2+ ↔ Mn2+ substitution in the Cu2Zn1−xMnxSnSe4 solid solution can be seen as a cation re-distribution process among the positions (0, 0, 0), (0, ½, ¼) and (0, ¼, ¾), including Cu+, Zn2+ and Mn2+. The Sn4+ cation does not take part in this process and remains on the 2b site. Moreover, the cross-over is also visible in the ratio of the lattice parameters c/(2a), showing a characteristic dependence on the chemical composition. The order parameter Q, the quantitative measure of Cu/BII disorder (BII = Zn and Mn), shows a distinct dependence on the Mn/(Mn + Zn) ratio. In Zn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals, the order parameter Q ∼ 0.7 and drops to Q ∼ 0 (complete Cu/BII disorder) in the compositional region 0.3 ≥ x ≥ 0.7. In Mn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals, adopting the stannite type structure, the order parameter reaches almost Q ∼ 1 (order). Thus, it can be concluded that only Mn-rich Cu2(Zn1−xMnx)SnSe4 mixed crystals do not show Cu/BII disorder. A similar trend of the dependence on the chemical composition of both Cu/BII-disorder and the band gap energy Eg in Cu2(Zn1−xMnx)SnSe4 mixed crystals was observed

Bioprospecting Fluorescent Plant Growth Regulators from Arabidopsis to Vegetable Crops

The phytohormone auxin is involved in almost every process of a plant’s life, from germination to plant development. Nowadays, auxin research connects synthetic chemistry, plant biology and computational chemistry in order to develop innovative and safe compounds to be used in sustainable agricultural practice. In this framework, we developed new fluorescent compounds, ethanolammonium p-aminobenzoate (HEA-pABA) and p-nitrobenzoate (HEA-pNBA), and investigated their auxin-like behavior on two main commercial vegetables cultivated in Europe, cucumber (Cucumis sativus) and tomato (Solanumlycopersicum), in comparison to the model plant Arabidopsis (Arabidopsis thaliana). Moreover, the binding modes and affinities of two organic salts in relation to the natural auxin indole-3-acetic acid (IAA) into TIR1 auxin receptor were investigated by computational approaches (homology modeling and molecular docking). Both experimental and theoretical results highlight HEA-pABA as a fluorescent compound with auxin-like activity both in Arabidopsis and the commercial cucumber and tomato. Therefore, alkanolammonium benzoates have a great potential as promising sustainable plant growth stimulators to be efficiently used in vegetable crops

ЛЮМИНЕСЦЕНЦИЯ КРИСТАЛЛОВ ЛАНТАН−ГАЛЛИЕВОГО ТАНТАЛАТА

Lanthanum−Gallium Tantalate is regarded as a perspective material for active elements of lasers. In this regard, the study of luminescent properties of these crystals are actual. In this paper, results of the first obtained luminescent properties of LGT crystals grown in different atmospheres are provided. A significant effect of the growth atmosphere on luminescent characteristics of LGT crystals is revealed.Лантан−галлиевый танталат (LGT) рассмотрен в качестве потенциального материала для изготовления активных элементов для лазерных сред. Впервые получены люминесцентные свойства кристаллов LGT, выращенных в различной атмосфере. Обнаружено существенное влияние атмосферы выращивания на люминесцентные характеристики данных кристаллов. Люминесцентные свойства исследованы при температуре 95 и 300 К

ВЛИЯНИЕ ИЗОТЕРМИЧЕСКОГО ОТЖИГА НА ОПТИЧЕСКИЕ ПАРАМЕТРЫ ЛАНТАН–ГАЛЛИЕВОГО ТАНТАЛАТА

The influence of isothermal annealing on the optical pa-rameters (transmission and diffused reflection spectra,) of La3Ga5.5Ta0.5O14 (langatate, LGT) crystals was studied. The experiment required using the polar cut {101 –0} samples made from crystals grown in athmospheres of argon (Ar), argon with oxygen (Ar + 0,5 % O2) and (Ar +2  % O2). The samples were annealed in vacuum and in air at temperatures from 500 to 1000 oC. Additional investigations were conducted using methods of optical microscopy, atomic force microcopy and diffused reflection spectroscopy. Исследовано влияние изотермического отжига на оптические параметры (спектры пропускания, диффузного отражения света, результаты оптической микроскопии) кристаллов лангатата La3Ga5,5Ta0,5O14. Изучены образцы полярных срезов {101 –0}, изготовленные из кристаллов, выращенных в различной атмосфере: аргон (Ar), аргон с кислородом (Ar + 0,5 % O2 и Ar + 2 % O2). Образцы были отожжены на воздухе и в вакууме при температуре от 500 до 1000 оС. Дополнительные исследования проведены методами оптической и атомно−силовой микроскопии, а также рентгеновской фотоэлектронной спектроскопии

STRUCTURE OF POLYMER/CLAY NANOCOMPOSITES, A MOLECULAR MODELLING PERSPECTIVE

The search for renewable biodegradable materials to replace conventional oil-based plastics is a fast-growing research area as it provides an important factor for the sustainable growth of the packaging industry. In this regard, clay-containing composite materials have numerous current and potential commercial applications. However, the interaction between clay and polymer, i.e. Poly(ethylene glycol), is influenced by many factors, such as the nature of the clay, length and nature of the polymer chain, hence, in this work polymer/clay nanocomposite is studied both ex`perimentally and theoretically. Structural and thermodynamic properties of formulated nanocomposites are probed using XRD and TGA techniques and then compared with corresponding values derived from a series of Molecular Dynamics simulations of intercalated polymer/clay nanocomposites. For the first time, the developed potential models were able to predict realistic basal spacing of poly(ethylene glycol)/clay nanocomposite. The simulation also revealed the structure of the interlayer on a molecular level, which greatly benefited the understanding of the formation of polymer/clay coatings. The swelling dynamics, energetics and structure of the clay interlayers are examined. Particular attention is paid to the behaviour of polymer and water when they coexist in the clay interlayer

Synthesis and Crystal Structures of Luminescent Mononuclear Ni(ii) and Cd(ii) Complexes with 1,10-phenanthroline

New supramolecular systems of Ni(II) and Cd(II) with 1,10-phenanthroline constructed by non-covalent interactions have been synthesized and characterized by single-crystal X-ray diffractometry. The smaller nickel(II) ion forms a cis complex with outer-sphere perchlorates, while the cadmium(II) ion forms a trans complex involving inner-sphere perchlorates. Both compoundsrevealintraligand-basedluminescentproperties