EPR monitoring of sol-gel processes

Shames, Alexander I.; Lev, Ovadia; Berkovich, Y.; Iosefzon-Kuyavskaya, Berta

doi:10.1007/bf00486251

Cited by 4 publications

(2 citation statements)

References 7 publications

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“…The same conclusion is obtained from ~ of the xerogels; re are very alike for A1, A2, and A3. It has been demonstrated that correlation times decrease with an increase in the average pore diameter of sol-gel glasses [12]. Therefore, the similar correlation times obtained can be easily explained by the result that the xerogels have the same average pore diameter as shown in Table 2.…”

Section: Methodssupporting

confidence: 69%

“…Interestingly, the solvent composition in the xerogels after 1000 h is almost the same with that in the films just prepared. Therefore, it is suggested that similar sol-gel reactions occur over different time domain in the bulk gel and thin film systems, It has been reported that the mobility of the spin probe TEMPOL decreases as the pore size of silica gels decreases [12,17]. This is due to the variation in the fraction of two types of adsorbed water (free-water and bound-water) in silica gel pores: the fraction of boundwater increases with decrease in pore size [17][18][19].…”

Section: Methodsmentioning

confidence: 93%

See 1 more Smart Citation

ESR study of a nitroxide radical in sol-gel glasses

Matsui

Kaneko

Yaginuma

et al. 1997

J Sol-Gel Sci Technol

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Abstract.A spin probe TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy) was dissolved in a tetraethyl orthosilicate sol-gel reaction system and measured by electron spin resonance spectroscopy at 295 K. The nitrogen hyperfine coupling constant was from 1.64-1.66 mT in the sol-gel solutions. The values were sensitive to the ethanol-to-water ratio of the solutions. The hyperfine coupling constant in the xerogels was 1.70 roT, which was almost the same as that in water, indicating that the probe molecules were trapped in silica pores with water adsorbed on the silica surfaces. The motion of TEMPOL in the xerogels was considerably slower than in the sol-gel solutions. The local viscosity estimated was from 70--90 cP. The ESR spectra of TEMPOL were altered during the sol-gel process, indicating that adsorbed water on the silica surfaces has an important role for trapping organic molecules in sol-gel glasses.

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Section: Methodssupporting

confidence: 69%