Quantum-Chemical Calculation of 29Si NMR Spectrum of Silicon Dioxide Fullerene-Like Molecules

Filonenko, O. V.; Kuts, V. S.; Terebinska, M. I.; Лобанов, В. В.

doi:10.15407/hftp06.02.263

Cited by 4 publications

(9 citation statements)

References 7 publications

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“…The step-by-step increase in the number of tetrahedra in oliugomers has been found to decrease the value of the deprotonation constants (pK a ) of silanol groups. The authors of [5] calculated 29 Si NMR spectra of fullerene-like hollow oligomers of silicic acid consisting of 1, 2, 4, 8, 10, and 20 siliconoxygen tetrahedra by DFT method with hybride exchange-correlation functional B3LYP and basis set 6-311+G(2d, p) with use of GIAO procedure.…”

Section: Resultsmentioning

confidence: 99%

A quantum chemical analysis of dependence of the protolytic properties of silica primary particles on their composition and spatial structure

et al. 2017

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High disperse silica is used as a sorbent and carrier of medical preparations in various branches of medicine, biotechnology etc. due to its physico-chemical properties, in particular, rather developed surface, chemical inertness, considerable adsorption capacity. The protolytic equilibrium of silica surface is to be examined, because the structure of its hydroxylic layer determines its properties. When silicic acid is polymerized, an increase in the molecular mass of the particles formed and the acidic properties of oligomers are changed.

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Section: Resultsmentioning

confidence: 99%

A quantum chemical analysis of dependence of the protolytic properties of silica primary particles on their composition and spatial structure

et al. 2017

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“…29 Si NMR peaks are tabulated in Table 4 in addition to the area contribution of each band and the corresponding Qn assignment. According to bibliography [48,49], chemical shift values from −66 ppm to −74 ppm are assigned to Q0 units in the 29 Si NMR spectrum. Bands in the range of −82 to −75 ppm correspond to Q1 units, and in the range of −86 to −84 ppm correspond to Q2 units.…”

Section: Nmr Study: Identification Of Structural Defects Responsibmentioning

confidence: 99%

Enhanced luminescence in rare-earth-free fast-sintering glass-ceramic

Fuertes

Fernández

Enríquez

2019

Optica

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One of the major challenges pursued in the luminescent materials community is to develop rare-earth-free phosphors in order to reduce the use of rare-earth elements, because of the lack of their availability and the environmental problems derived from their mining and processing. In this work, a rare-earth-free glass-ceramic-based phosphor with high photoluminescence has been designed. This novel phosphor rich in Na-rich plagioclase feldspar crystallizations presents high crystallinity, ∼94%, and a dual micro-nanostructure provided by a fast-sintering processing route. Structural disorder in Si-Al distribution favors formation of luminescent centers in the glass-ceramic material, which results in an enhancement of both the UV-blue and the red luminescence regarding natural feldspars, 1 order of magnitude and 6 times, respectively. A microstructural and structural study by means of x-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, cathodoluminescence, and nuclear magnetic resonance evidence the important role of composition in the alteration of Si-Al ordering schemes. A strong correlation between Si-Al disorder and the presence of active luminescent centers is corroborated. Our research shows a sustainable, cost-effective, innovative, and scalable material that may be considered as an alternative to rare-earth phosphors for applications such as security markers or light-emitting glasses. This novel family of rare-earth-free glass-ceramics opens a new gate through structural tailoring to enhance and tune the intrinsic luminescent emissions displayed for relevant future optical applications.

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“…[21,30] Also listed in Tables A. 4, A.5 and A.6 is the Gibbs free energy change for the condensation 120 reactions (∆ R G) that yield each cluster. A negative value for all clusters indicates that the respective condensation reactions are spontaneous.…”

Section: Energetic Analysismentioning

confidence: 99%

“…[30] This last observation is also related to the existence of hydrogen bonds, which have a stabilizing effect on the clusters, as mentioned above. The most favored cyclic 130 clusters are Q 4 2 , followed by…”

Section: Energetic Analysismentioning

confidence: 99%

“…[2] Due to their extremely low thermal conductivity (as low as 0.010 W.m −1 .K −1 ) combined with a very low density (<0.1 g.cm −3 ), these materials have now come of age in the aerospace industry, being used 5 primarily as thermal insulators for spacecraft. [2][3][4] Their high porosity (80 -99.8%) and surface area (500 -1200 m 2 .g −1 ) result in exceptional performance as adsorbents for organic pollutants and heavy metals, catalytic supports, drug delivery, among others. [5] Furthermore, the good optical properties and in particular the low refractive index presented by silica aerogels (1.007 -1.25) have, for instance, opened the route for their use in Cherenkov detectors.…”

Section: Introductionmentioning

confidence: 99%

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Organically-modified silica aerogels: A density functional theory study

Maximiano

Durães

Simões

2019

The Journal of Supercritical Fluids

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The primary particles of silica aerogels resulting from three different mixtures of precursors -50% tetramethylorthosilicate (TMOS)/50% vinyltrimethoxysilane (VMTS); 50% tetraethylorthosilicate (TEOS)/50% aminopropyltriethoxysilane and 50% TEOS/50% glycidylpropoxi -as well as aerogels of pure TMOS and VTMS, have been studied by quantum mechanics density functional theory calculations (DFT), at the B3LYP/6-311+G(d,p) level of theory). Thermo-chemical calculations have indicated that cage structures are the most favored for all materials, followed by other species (linear and cyclic) with high degrees of condensation. A vibration mode analysis based on a numerical model fitted to experimental infrared spectra, has allowed the identification of the most representative silica clusters for all the materials studied. The resulting theoretical spectra were close to their experimental counterparts. Analysis of calculated and experimental 29 Si-NMR spectral data generally corroborated the derived model.

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Quantum-Chemical Calculation of 29Si NMR Spectrum of Silicon Dioxide Fullerene-Like Molecules

Cited by 4 publications

References 7 publications

A quantum chemical analysis of dependence of the protolytic properties of silica primary particles on their composition and spatial structure

A quantum chemical analysis of dependence of the protolytic properties of silica primary particles on their composition and spatial structure

Enhanced luminescence in rare-earth-free fast-sintering glass-ceramic

Organically-modified silica aerogels: A density functional theory study

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