研究目的
To study the structural changes during the gel to glass transition of silica xerogels using the fluorescence properties of Dy3+ ions and to characterize the effect of metal cation co-dopants on the state of aggregation of rare earth ions in silica sol gel.
研究成果
Dy3+ doped silica matrices prepared via sol-gel process exhibit enhanced fluorescence properties with heat treatment, indicating embedding in an asymmetric glassy network. Co-dopants inhibit rare earth ion clustering and promote dispersion, with effectiveness correlating to cation field strength. This allows control over aggregation and cross-relaxation, making the materials promising for optical applications.
研究不足
The study is limited to Dy3+ ions in silica sol-gel systems; other rare earth ions or matrices were not explored. The heat treatment range (up to 1000 °C) and specific co-dopants (Li+, Na+, K+, Ag+) may not cover all possible conditions. The opacity of gels with 0.5 mol % Dy2O3 upon heat treatment restricted further analysis for that concentration.
1：Experimental Design and Method Selection:
The study utilized the sol-gel process to prepare Dy3+ doped silica matrices, with fluorescence spectroscopy employed to analyze structural changes and the effects of co-dopants. The fluorescence intensity ratio (Y/B) and full width half maximum (FWHM) were used as indicators of symmetry and disorder in the Dy3+ ion environment.
2：Sample Selection and Data Sources:
Silica sols containing 2 equivalent mol % Dy2O3 were prepared from tetraethylorthosilicate (TEOS), Dy(NO3)3·9H2O, deionized water, HNO3, and NH4OH. Co-dopants (10 equivalent mol %) were added as their nitrates (e.g., Li+, Na+, K+, Ag+). Samples were heat-treated at temperatures from 200 to 900 °C.
3：List of Experimental Equipment and Materials:
Equipment includes a spectrophotophotofluorimeter (Shimadzu-RFPC 5301) for optical spectra, a programmable furnace for heat treatment, and materials such as TEOS (Fluka pure grade), Dy(NO3)3·9H2O (Merck, India), and various nitrates for co-dopants.
4：Experimental Procedures and Operational Workflow:
Sols were prepared with specific molar ratios, pH adjusted to 3, cast in petri dishes, gelled at room temperature for 1 week, dried at 60 °C for 14 days, and heat-treated at 3 °C/h. Fluorescence and absorption spectra were recorded at laboratory temperature.
5：Data Analysis Methods:
Data analysis involved calculating fluorescence intensity ratios (Y/B), FWHM, and comparing spectra to assess symmetry, covalency, and clustering effects. Statistical analysis was based on spectral measurements and comparisons with known oxide systems.
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