Nitrogen-Containing Paramagnetic Centers in Vitreous Silica
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- Radtsig, V.A. Kinet Catal (2005) 46: 578. doi:10.1007/s10975-005-0112-x
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The results of a study on the structure and spectral characteristics of nitrogen-containing paramagnetic defects in vitreous silicas are presented. The UV irradiation, γ-irradiation, and mechanical destruction of nitrogen-doped vitreous silicas, which were synthesized using a plasma-chemical SPCVD technology, were used for the generation of paramagnetic centers. Another technique for producing nitrogen-containing paramagnetic centers was the target-oriented chemical modification of the surface defects of silica with the use of NH3 (ND3) molecules. Paramagnetic centers with free valences at silicon [(≡Si-O-)2Si· (-NH2) and (≡Si-O-)2Si· -N(-Si≡)2] and nitrogen atoms [≡Si-N· -H and ≡Si-N· -Si≡] were detected. The reactivity of nitrogen-centered radicals toward H2 and CO molecules was studied. Quantum-chemical calculations of model systems were employed in the interpretation of the experimental data. The strengths of Si-O and Si-N bonds in vitreous silica were compared.