Search results for "Orthosilicate"
showing 10 items of 27 documents
Genetic, biological and structural hierarchies during sponge spicule formation: from soft sol–gels to solid 3D silica composite structures
2012
Structural biomaterials are hierarchically organized and biofabricated. Although the structural complexity of most bioskeletons can be traced back from the millimeter-scale to the micrometer- or submicrometer-scale, the biological and/or genetic basis controlling the synthesis of these skeletons and their building blocks remained unknown. There is one distinguished example, the spicules of the siliceous sponges, for which the principle molecules and molecular-biological processes involved in their formation have been elucidated in the last few years. In this review, recent data on the different levels of molecular, biological and structural hierarchies controlling the synthesis of the pictu…
Synthesis of large-pore ordered mesoporous silicas containing aminopropyl groups
2005
Ordered mesoporous silicas with large-pore diameters incorporating aminopropyl groups in variable quantity have been synthesized via the co-condensation of tetraethyl orthosilicate (TEOS) and 3-tert-butyloxycarbonylaminopropyltriethoxysilane templated with nonionic surfactant P123 under acidic conditions. The deprotection of amino groups was then quantitatively achieved either by thermal treatment or acid hydrolysis followed by Et3N treatment, both routes leading to exactly the same materials. We showed that the free amino centers are fully accessible, by using the condensation of the amine function with benzaldehyde.
Electron paramagnetic resonance study of exchange coupled Ce3+ ions in Lu2SiO5 single crystal scintillator
2016
Abstract The Ce 3+ ions incorporation inside lutetium oxyorthosilicate (Lu 2 SiO 5 ) single crystals was studied by electron paramagnetic resonance. Already known Ce1 and Ce2 centers originating from the lattice peculiarity allowing two lutetium sites coordinated by different number of the oxygen ions were detected. Remarkably, for the Ce2 center, the determined g 2 tensor is asymmetric and could not be diagonalized as compared to the Ce1 center, for which the three principal values and corresponding axes orientation have been determined and reported previously. Besides, the much weaker resonance lines found in spectra close to those coming from the Ce1 and Ce2, and following them under cry…
Modulation of folic acid bioaccessibility by encapsulation in pH-responsive gated mesoporous silica particles
2015
[EN] A study on the controlled release of folic acid (FA) from pH-responsive gated mesoporous silica particles (MSP) is reported. The MCM-41 support was synthesized using tetraethyl orthosilicate (TEOS) as hydrolytic inorganic precursor and the surfactant hexadecyltrimethylammonium bromide (CTAB) as porogen species. Calcination of the mesostructured phase resulted in the starting solid. This solid was loaded with FA to obtain the initial support S0. Moreover, this FA-loaded material was further functionalized with 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (N3) in order to obtain the gated polyamine-functionalised material S1. Solids S0 and S1 were characterized using standar…
Designing solid optical sensors for in situ passive discrimination of volatile amines based on a new one-step hydrophilic PDMS preparation
2016
Abstract We reported an optimal material for embedding chemoresponsive dyes based on modified commercial PDMS. A new approach to impart hydrophilicity to H-PDMS in an unique step was developed by addition of tetraethyl orthosilicate (TEOS) and in absence of basic or acid aqueous mixtures or hydroxyl-compounds during the PDMS coating process. This incorporation significantly enhances the performance of PDMS-based devices for sensing applications. New colorimetric sensors for passive detection and in situ discrimination of volatile amines have been obtained. The limit of detection achieved was 1.5 mg m −3 for both, dimethylamine and methylamine, suitable to control real working atmospheres. T…
Epoxidation of dibenzocycloalkenes on Ti–Ge-MCM-41 and Ti-SBA-15 catalysts
2005
Abstract Epoxidation of a series of dibenzocycloalkenes: phenanthrene, 5H-dibenzo[ a , e ]cycloheptene, 5H-dibenzo[ a , c ] cycloheptene, 5,6-dihydrodibenzo[ a , e ]cyclo-octene, and dibenzo[ a , e ]cyclooctene with hydrogen peroxide was investigated on Ti- and Ge-modified Ti-incorporated-type mesoporous catalysts including MCM-41 and SBA-15 structures looking for the effect of the porous texture and Ge-promoting on both activity and selectivity to epoxide and H 2 O 2 efficiency. Ti–Ge-MCM-41 catalysts (Si/Ti = 43; Si/Ge = 85 and Si/Ti = 41; Si/Ge = 62) were prepared by a one-pot surfactant-assisted procedure based on the use of a cationic surfactant (CTAB, cetyltrimethylammonium bromide), …
Litiju saturošu keramiku cietfāžu sintēze un raksturošana
2021
“Litiju saturošu keramiku cietfāžu sintēze un raksturošana”. Seņko M., darba vadītājs vadošais pētnieks Dr. chem. Zariņš A. Zinātniskie konsultanti pētniece, Mg. chem. Avotiņa L. un pētniece, Mg. chem. Trimdale A. Bakalaura darbs, 45 lapas, 31 attēls, 5 tabulas, 54 literatūras avoti, 5 pielikumi. Latviešu valodā. Literatūras apskatā apkopota informācija par procesiem kodoltermiskās sintēzes reaktoros, litiju saturošu savienojumu īpašībām un sintēzes metodēm, raksturotas darbā izmantotās analīžu metodes. Eksperimentālajā daļā ar cietfāžu sintēzes metodi ieguva vairākus litiju saturošus savienojumus, izmantojot dažādus sintēzes parametrus. Fāžu sastāva un termisko īpašību noteikšanai izmantoj…
Luminescence of X-ray induced radiation defects in modified lithium orthosilicate pebbles with additions of titanium dioxide
2017
The authors greatly acknowledge the technical and experimental support of O. Leys, M. H. H. Kolb, and R. Knitter (Karlsruhe Institute of Technology, Germany). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Economics”.
Tritium release from breeding blanket materials in high magnetic field
2007
Abstract Under the operating conditions of a fusion reactor, the blanket materials: ceramic and Be pebbles will be at a high temperature (up to 1123 K), under action of intense radiation (up to 10 19 n m −2 s −1 ) and magnetic field (MF) up to 7–10 T. In order to introduce action of radiation and MF in post-irradiation investigations of the tritium release from the blanket materials, a special rig for thermo-annealing of pre-irradiated samples at a high temperature up to 1120 K under irradiation with fast electrons of 5 MeV and dose rate 14 MGy/h in MF up to 1.7 T was used for this study. A delay of the tritium release in MF of 2.4 T at thermo-annealing of the lithium orthosilicate Li 4 S…
Improving the On-Line Extraction of Polar Compounds by IT-SPME with Silica Nanoparticles Modified Phases
2018
In the present work the extraction efficiency of in-tube solid-phase microextraction (IT-SPME) for polar herbicides has been evaluated using extractive capillaries coated with different polymeric sorbents. For this purpose, aqueous solutions of herbicides with a wide range of polarities, including some highly polar compounds (log Kow < 1), have been directly processed by IT-SPME coupled on-line to capillary liquid chromatography with UV-diode array detection. For extraction, commercially available capillary columns coated with polydimethylsiloxane (PDMS) and polyetilenglicol (PEG)-based phases have been used, and the results have been compared with those obtained with a synthesized tetra…