Search results for "SIO2"
showing 10 items of 43 documents
Growth of paramagnetic defects by gamma rays irradiation in oxygen-deficient silica
2005
Abstract We report an electron paramagnetic resonance (EPR) study of gamma rays irradiation effects on an oxygen-deficient silica obtained from fused quartz. We have found that three types of E′ centers, E α ′ , E γ ′ and E δ ′ , and a paramagnetic defect in a spin triplet state (S = 1) are induced. The EPR signals dependence on the microwave power have been investigated. The concentrations of these centers as a function of gamma ray irradiation show that for high dose a limit value is reached suggesting a generation process from precursors.
Isolation of the CH3˙ rotor in a thermally stable inert matrix: first characterization of the gradual transition from classical to quantum behaviour …
2014
International audience; Matrix isolation is a method which plays a key role in isolating and characterizing highly reactive molecularradicals. However, the isolation matrices, usually composed of noble gases or small diamagnetic molecules,are stable only at very low temperatures, as they begin to desegregate even above a few tens of Kelvin.Here we report on the successful isolation of CH3 radicals in the cages of a nearly inert clathrate–SiO2matrix. This host is found to exhibit a comparable inertness with respect to that of most conventionalnoble gas matrices but it is characterized by a peculiar thermal stability. The latter property is related to thecovalent nature of the host material a…
On the Relationship between Jetted Inks and Printed Biopatterns:Molecular-Thin Functional Microarrays of Glucose Oxidase
2009
Arrays of circular spots of glucose oxidase have been obtained on functionalized silicon oxide by piezoelectric inkjet printing and the enzymatic activity toward glucose recognition has been monitored. The addition of glycerol to the molecular ink allows to obtain high spot definition and resolution (tens of micrometers wide; one molecule tall), but in spite of its well-known structural stabilizing properties, in dynamic conditions it may lead to increased protein stresses. The jetting voltage and pulse length have been found to be critical factors for both activity retention and pattern definition. High voltages and pulse lengths results in stress effects along with the loss of activity, w…
WOx phase growth on SiO2/Si by decomposition of tungsten hexacarbonyl:Influence of potassium on supported tungsten oxide phases
2009
International audience; Synchrotron based photoemission spectroscopy was used to study the adsorption of tungsten hexacarbonyl on SiO2 surfaces modified by potassium. Results were compared with the ones obtained when no potassium was present. Experiments using W4f and Si2p intensities variations show that, at 140 K, the tungsten hexacarbonyl growth proceeds via a simultaneous multilayer mode for the two kinds of surfaces but with differences in compositions of growing layers. Indeed, it is evidenced that, even at cryogenic temperatures, the presence of potassium induces decomposition of a significant part of tungsten hexacarbonyl molecules through a strong interaction between tungsten and p…
Ion-Track Template Synthesis and Characterization of ZnSeO3 Nanocrystals
2022
A.I.P. thanks the Institute of Solid-State Physics, University of Latvia. ISSP UL as the Center of Excellence is supported through the Framework Program for European universities. The work was carried out within the framework of the grant AP05134367 of the Ministry Funding: The work was carried out within the framework of the grant AP05134367 of the Ministry of education and Science Science of of the Republic Republic of Kazakhstan.
Influence of SiO2 nanoparticles on relative fluorescence of plant cells
2015
Nanoparticles (nano-scale particles (NSPs)) are defined as particles with dimensions less than 100 nm. SiO<sub>2</sub> nanoparticles are one of the most widely common nanoparticles in the environment, particularly in urban areas. The sources of SiO<sub>2 </sub>nanoparticles are very different, including natural nanoparticles, anthropogenic and engineered nanoparticles. The SiO<sub>2 </sub>nanoparticles could be considered a source of different pollution effects on leaving organisms. Nevertheless, knowledge of the mechanisms, through which the SiO<sub>2 </sub>nanoparticles affect cells, is incomplete. The aim of the research was to elaborate a …
Near Room-Temperature Memory Devices Based on Hybrid Spin-Crossover@SiO2Nanoparticles Coupled to Single-Layer Graphene Nanoelectrodes
2016
The charge transport properties of SCO [Fe(Htrz)2 (trz)](BF4 ) NPs covered with a silica shell placed in between single-layer graphene electrodes are reported. A reproducible thermal hysteresis loop in the conductance above room-temperature is evidenced. This bistability combined with the versatility of graphene represents a promising scenario for a variety of technological applications but also for future sophisticated fundamental studies.
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…
Effect of oxygen deficiency on the radiation sensitivity of sol-gel Ge-doped amorphous SiO2
2008
We report experimental investigation by electron paramagnetic resonance (EPR) measurements of room temperature γ-ray irradiation effects in sol-gel Ge doped amorphous SiO2. We used materials with Ge content from 10 up to 104 part per million (ppm) mol obtained with different preparations. These latter gave rise to samples characterized by different extents of oxygen deficiency, estimated from the absorption band at ~5.15 eV of the Ge oxygen deficient centers (GeODC(II)). The irradiation at doses up to ~400 kGy induces the E'-Ge, Ge(1) and Ge(2) paramagnetic centers around g ~ 2 with concentrations depending on Ge and on GeODC(II) content. We found correlation between Ge(2) and GeODC(II) con…
Near-Infrared Emission of O2 Embedded in Amorphous SiO2 Nanoparticles
2011
We report an experimental study on the emission properties of O2 molecules loaded by a thermal diffusion process at 200 °C into high-purity silica nanoparticles with mean diameters of 7 and 40 nm. The embedded O 2 features a singlet to triplet emission band peaked at 1272 nm in agreement with the band observed for bulk silica materials. The photoluminescence excitation spectra have been determined in the visible and in the infrared range and are characterized by narrow bands peaked at 691, 764, and 1069 nm, respectively. By comparison of the transition energies, the vibrational quanta have been determined for the ground and for both the excited states; the values found are lower than the co…