The first hafnium germanate with garnet-type of structure: mild hydrothermal synthesis, crystal structure and new mechanism of hydroxyl inclusion

Sodium hafnium germanate, Na3Hf1.7Ge3O10(OH)1.8, with garnet-type of structure was synthesized as a single phase, nanoparticles (100–600 nm) at mild hydrothermal conditions (230 °C) and autogenous pressure. The structure was solved ab initio from powder X-ray diffraction data and subsequently refined [Rexp: 6.10, Rwp: 7.26, Rp: 5.39, GOF: 1.19, RB: 1.50] by the method of Rietveld. The solid crystallizes in cubic space group Ia-3d (230), with a = 12.6819(2) Å, V = 2039.65(1) Å3 and Z = 8. The structure is built up of rare combination of two tetravalent (Ge4+ and Hf4+) and one monovalent (Na+) cation alternating in form corner-sharing GeO4 tetrahedra and HfO6 octahedra whose negative charge is compensated by Na+ residing in dodecahedral coordination. Unlike the typical tetrahedral site disorder in hydrogarnets (hydrogrossular, hibschite, and katoite) we found that the octahedral position of the heavy Hf4+ cation is partly vacant which reveals alternative mechanism of charge unbalance leading to incorporation of hydroxyl group. Furthermore, the synthesized material is the first hafnium germanate with garnet-type of structure and the second known sodium hafnium germanate.publishe

Deposition of silicon nitride thin films by hot-wire CVD at 100ºC and 250ºC

Silicon nitride thin films for use as passivation layers in solar cells and organic electronics or as gate dielectrics in thin-film transistors were deposited by the Hot-wire chemical vapor deposition technique at a high deposition rate (1-3 Ǻ/s) and at low substrate temperature. Films were deposited using NH3/SiH4 flow rate ratios between 1 and 70 and substrate temperatures of 100º C and 250ºC. For NH3/SiH4 ratios between 40 and 70, highly transparent (T ~ 90%), dense films (2.56 - 2.74 g/cm3) with good dielectric properties and refractive index between 1.93 and 2.08 were deposited on glass substrates. Etch rates in BHF of 2.7 Ǻ/s and 10 MV cm−1.Fundação para a Ciência e Tecnologia (FCT) - FCT/CNRS programa com o contracto no. 20798, bolsa de investigaçao e projecto PTDC-CTM-66558-200

Diethylenetriamine/diamines/copper (II) complexes [Cu(dien)(NN)]Br2: Synthesis, solvatochromism, thermal, electrochemistry, single crystal, Hirshfeld surface analysis and antibacterial activity

Two dicationic water soluble mixed triamine/diamine copper (II) complexes, of general formula [Cu(dien)NN]Br2(1–2) [dien = diethelenetriamine and NN is en = ethylenediamine or Me4en = N,N′,N,N′-tetramethylethylenediamine] were prepared under ultrasonic mode with a relatively high yield. These complexes were characterized by elemental microanalysis, UV visible IR spectroscopy, and thermal and electrochemical techniques. In addition, complex 2 structure was solved by X-ray single crystal and Hirshfeld surface analysis. The complex exhibits a distorted square pyramidal coordination environment around Cu(II) centre. The solvatochromism of the desired complexes was investigated in water and other suitable organic solvents. The results show that the Guttmann’s DN parameter values of the solvents have mainly contributed to the shift of the d–d absorption band towards the linear increase in the wavelength of the absorption maxima of the complexes. The complex 1 showed higher antibacterial activity against the studied microorganisms compared to complex 2. Both complexes revealed promising antibacterial activities.The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for its funding of this Research group NO (RG-0257-1435-1436)

Synchrotron X-ray studies on polyamide composites prepared by reactive injection molding

Semicrystalline polyamide 6 (PA6) and composites on its basis are among the most frequently used polymer materials for highly demanding applications. The performance of these composites depends on the crystalline structure of the PA6 matrix in which two crystalline forms most frequently coexist: α- and γ-polymorphs. This work reports on the crystalline structure of a variety of composite materials produced by in-mold reactive polymerization of caprolactam in specially designed semi-automatic equipment for reactive processing of nylons (NYRIM), carried out in the presence of particulate mineral reinforcements (natural or-ganically treated aluminum silicates and synthetic titanosilicates), PA6 oriented monofilaments and textile structures of glass fibers. The morphology and the crystalline structure of all composites were studied by syn-chrotron X-ray diffraction. Transcrystalline PA6 layer was observed in all fibrous PA6 laminates whose struc-ture fine crystalline structure was accessed.Fundação para a Ciência e Tecnologia; German Synchrotorn Radiation Source - DESY, Hambur

Photocatalytic degradation of Rhodamine B dye by cotton textile coated with SiO2-TiO2 and SiO2-TiO2-HY composites

This work is devoted to study the photocatalytic ability of cotton textiles functionalized with SiO2-TiO2 and SiO2-TiO2-HY composites to degrade a dye molecule. Coatings were prepared by sol-gel method and calcined at different temperatures in a range of 400–750 °C. FTIR confirmed the existence of SiOTi bounds and the band located in the region between 570 and 600 cm−1 was used to calculate the framework Si/Al ratio of HY in the SiO2-TiO2-HY composites. XRD confirmed the presence of nanosized TiO2 (anatase phase) in all calcined composites. Nitrogen adsorption isotherms showed a decrease in surface area and pore volume for higher calcination temperature. A simple mechanical process was used to impregnate the different composites on the cotton substrates. The photocatalytic activity of cotton textiles functionalized with SiO2-TiO2 and SiO2-TiO2-HY composites was tested via the degradation of Rhodamine B (RhB) dye under similar solar irradiation. The best catalytic performance was achieved with the SiO2-TiO2 and SiO2-TiO2-HY composites subjected to a calcination treatment at 400 °C, whereas SiO2-TiO2 presented a decolourization and mineralization around 94% and 89%, respectively, after 2 h of irradiation. Furthermore, the products of RhB degradation were analysed and identified by using HPLC-ESI–MS and ion chromatography techniques and a photocatalytic mechanism was proposed.The authors thank CAPES from Brazil for the financial support of this work. This work is also a result of project “AIProcMat@N2020 − Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006 and the project BioTecNorte (operation NORTE-01-0145-FEDER-000004), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work also has been funded by ERDF through COMPETE2020 − Programa Operacional Competitividade e Internacionalização (POCI), Project POCI-01-0145-FEDER-006984 − Associate Laboratory LSRE-LCM and by national funds through FCT − Fundacão para a Ciência e a Tecnologia for project PTDC/AAGTEC/5269/2014 and Centre of Chemistry (UID/QUI/00686/2013 and UID/QUI/0686/2016).info:eu-repo/semantics/publishedVersio

Simple shape-selective control of germanium pyroxene crystals

Molecular recognition at interfaces is essential approach for growth of crystals with selectively exposed facets. In general, this process is guided by impurities or solvents that favor the development of surfaces with particular reticular density. However, the specific agents that direct the crystal habit of one system often remain irrelevant for another, and thus, the control of crystal surface of many materials is still poorly known. Here we show selective resizing of prismatic crystal facets of germanium clinopyroxene (NaFeGe2O6) only by a simple switch between nitrate (Fe3+), chloride (Fe3+), and sulfate (Fe2+) sources of iron. The observed effect is explained by the combination of different rates of ion transport to the crystal surface and binding affinity of the hydrolyzed derivatives of the iron precursors that cap the crystal surface during the crystallization. Furthermore, this work reveals the first mild hydrothermal synthesis of germanium clinopyroxeneThis work was supported by the Fundaçã̧o para a Ciência e a Tecnologia (FCT) − “Investigador 2013 (IF/01516/2013)”