Properties of methyl radical trapped in amorphous SiO2 and in natural SiO2-clathrate Melanoflogite

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Abstract

We report an experimental investigation by electron paramagnetic resonance (EPR) on methyl radical (CH3 • ) observed in γ-ray irradiated high-purity amorphous silicon dioxide (a-SiO2) and in a polycrystalline sample of Melanophlogite, a rare natural form of SiO2-clathrate. From the analysis of the EPR spectra we estimate the correlation time of the hindered rotational motion of CH3 • molecules at T=77 K in the two different materials. This physical quantity gives a quantitative measure of the freedom of motion of CH3 • molecules trapped in the two solid systems, putting forward relevant information on the properties of the cavities/interstices inwhich the radicals are confined. In particular, our data suggest that in a-SiO2 the CH3 • molecules are trapped in interstices with diameter significantly lower than about 5.7 Å, which is the size of the smaller cavity involved in the crystalline structure of Melanophlogite.
Lingua originaleEnglish
pagine (da-a)9-12
Numero di pagine4
RivistaJournal of Non-Crystalline Solids
Volume361
Stato di pubblicazionePublished - 2013

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clathrates
interstices
Molecules
Paramagnetic resonance
electron paramagnetic resonance
molecules
cavities
Amorphous silicon
Silicon Dioxide
Gamma rays
amorphous silicon
purity
Silica
gamma rays
silicon dioxide
estimates
methyl radical

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Condensed Matter Physics
  • Ceramics and Composites

Cita questo

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title = "Properties of methyl radical trapped in amorphous SiO2 and in natural SiO2-clathrate Melanoflogite",
abstract = "We report an experimental investigation by electron paramagnetic resonance (EPR) on methyl radical (CH3 • ) observed in γ-ray irradiated high-purity amorphous silicon dioxide (a-SiO2) and in a polycrystalline sample of Melanophlogite, a rare natural form of SiO2-clathrate. From the analysis of the EPR spectra we estimate the correlation time of the hindered rotational motion of CH3 • molecules at T=77 K in the two different materials. This physical quantity gives a quantitative measure of the freedom of motion of CH3 • molecules trapped in the two solid systems, putting forward relevant information on the properties of the cavities/interstices inwhich the radicals are confined. In particular, our data suggest that in a-SiO2 the CH3 • molecules are trapped in interstices with diameter significantly lower than about 5.7 {\AA}, which is the size of the smaller cavity involved in the crystalline structure of Melanophlogite.",
keywords = "Methyl radical; Electron paramagnetic resonance; Radiation effects; Clathrate; Silica",
author = "Roberto Boscaino and Gelardi, {Franco Mario} and Simonpietro Agnello and Gianpiero Buscarino",
year = "2013",
language = "English",
volume = "361",
pages = "9--12",
journal = "Journal of Non-Crystalline Solids",
issn = "0022-3093",
publisher = "Elsevier",

}

TY - JOUR

T1 - Properties of methyl radical trapped in amorphous SiO2 and in natural SiO2-clathrate Melanoflogite

AU - Boscaino, Roberto

AU - Gelardi, Franco Mario

AU - Agnello, Simonpietro

AU - Buscarino, Gianpiero

PY - 2013

Y1 - 2013

N2 - We report an experimental investigation by electron paramagnetic resonance (EPR) on methyl radical (CH3 • ) observed in γ-ray irradiated high-purity amorphous silicon dioxide (a-SiO2) and in a polycrystalline sample of Melanophlogite, a rare natural form of SiO2-clathrate. From the analysis of the EPR spectra we estimate the correlation time of the hindered rotational motion of CH3 • molecules at T=77 K in the two different materials. This physical quantity gives a quantitative measure of the freedom of motion of CH3 • molecules trapped in the two solid systems, putting forward relevant information on the properties of the cavities/interstices inwhich the radicals are confined. In particular, our data suggest that in a-SiO2 the CH3 • molecules are trapped in interstices with diameter significantly lower than about 5.7 Å, which is the size of the smaller cavity involved in the crystalline structure of Melanophlogite.

AB - We report an experimental investigation by electron paramagnetic resonance (EPR) on methyl radical (CH3 • ) observed in γ-ray irradiated high-purity amorphous silicon dioxide (a-SiO2) and in a polycrystalline sample of Melanophlogite, a rare natural form of SiO2-clathrate. From the analysis of the EPR spectra we estimate the correlation time of the hindered rotational motion of CH3 • molecules at T=77 K in the two different materials. This physical quantity gives a quantitative measure of the freedom of motion of CH3 • molecules trapped in the two solid systems, putting forward relevant information on the properties of the cavities/interstices inwhich the radicals are confined. In particular, our data suggest that in a-SiO2 the CH3 • molecules are trapped in interstices with diameter significantly lower than about 5.7 Å, which is the size of the smaller cavity involved in the crystalline structure of Melanophlogite.

KW - Methyl radical; Electron paramagnetic resonance; Radiation effects; Clathrate; Silica

UR - http://hdl.handle.net/10447/70563

M3 - Article

VL - 361

SP - 9

EP - 12

JO - Journal of Non-Crystalline Solids

JF - Journal of Non-Crystalline Solids

SN - 0022-3093

ER -