The role of surface boron as adsorption center for the sorption of water by porous glass

Abstract

o extinction coefficient of azomethane is small,7 we may write 70 = 7?n/[A], Plots of µ and vs. 7?n/[A] are shown in Figure 3, and the expected independence of the quantum yields with respect to pressure and intensity is evident at low intensities. The values of ho/h and ß at 180°are 1.0 ± 0.1 and (1.1 ± 0.1) X 10 ~2, respectively. The values of µ obtained by Toby and Nimoy1-5 were extrapolated to zero intensity and gave values of ho/h at 50, 100, 135, and 180°of

Infrared spectra of the interactions of aniline and porous glass surfaces

“…1 is a typical "background" spectrum of highly-degassed porous glass; the prominent features are a band at 3748 cmp' due to surface silanols and a smaller but sharp band at 3703 cm-' due to surface B-OH groups (1)(2)(3)(4)(5), hereafter termed SiOH and B-OH bands. When such a glass specimen was exposed to aniline vapor at room temperature at increasingly higher pressures from 10 to 200 p and was then degassed, the surface hydroxyl bands were altered and a series of absorptions caused by sorbed aniline were observed.…”

“…2. As previous work had shown that it is difficult to remove the adsorbed water (2,3,5) and the 3600 cm-' band could be removed relatively easily, it is unlikely that the 3600 cm-I remnant was caused by water contamination. Rather, it seems plausible that the aromatic ring of 2 was oriented in such a fashion that some n-OH interaction was possible, thus producing a weak 3600 cm-' band.…”

“…Silica and 3 % B,O, -Si02 samples were prepared from Cab-0-Sil silica (G. Cabot Co., Boston, Mass.). Most experimental details including the dehydration, deuteration, and fluoridation of specimens have been described elsewhere (1)(2)(3)(4)(5). Reagent grade (Matheson Co.) aniline was dried over Na2S04 and distilled 4 times; the final purification was done by repeated freezing and thawing in vacuo.…”

“…Recent studies have provided evidence that much of the reactivity of porous glass surfaces could be attributed to the presence of impurities (1)(2)(3)(4)(5)(6)(7). With NH, sorption on highly dehydrated porous glass (4), infrared spectra indicated that residual boron played a role in physical adsorptions, dissociative chemisorption, as well as in an undissociative chemisorption involving the coordination of NH, to boron present on the glass.…”

The influence of long additional thermal treatment of controlled porous glasses on the structuralization of their silica network

“…temperature range 400-800~ sodium and boron atoms remaining in the porous structure of the CPG diffuse from the bulk to the surface [1][2][3][4][5].…”