Abstract
Two types of silica glass doped by o-phenanthroline (o-phen) (S2) and without organic reagent (S1) were studied. Paramagnetic probes (Mn(II), VO(II), Cu(II)) were introduced into both systems by doping or by impregnetion. Sol-gel-xerogel transition in these systems was investigated by electron paramagnetic resonance (EPR). In the S1 system, hydrated metal ions were shown to react weakly with silanol groups during every stage of silica polymerization. The effect of sol to gel7 transition is not observed in S1 spectra. Contrary to that, EPR spectra of VO(II) ions in S2 demonstrate significant changes during sol-gel-xerogel transition. As polymerization proceeds, the signals of non-immobilized hydrated metal ion and that of mixed water-o-phen-metal complex are substituted by signals of metal-o-phen complexes immmobilized on the porous surface. After gelation, the latter signals prevail. EPR spectra provide a means to monitor in situ structural changes during the various stages of glass formation.
| Original language | English |
|---|---|
| Pages (from-to) | 105-114 |
| Number of pages | 10 |
| Journal | Journal of Non-Crystalline Solids |
| Volume | 163 |
| Issue number | 2 |
| DOIs | |
| State | Published - Nov 1993 |
Bibliographical note
Funding Information:The authorsa cknowledgues e of the EPR facilities of the laboratoryo f electron paramagnetic resonanceo f the Farcas Light Induced Center of the Hebrew University of Jerusalem. They also thank Professor Shaul Goren (Ben Gurion University of the Negev) for useful discussionsa nd friendly support.T he researchis supportedb y a grant from the MOST, Israel, and Forschungs-zentrum fur Umwelt und Gesundheit GmbH, NeuerbergG, ermanyT. he researchis undertaken in collaboratiown ith ProfessorD . Avnir and Professor M. Ottolengio f the Hebrew University.