Interior hydroxyls of the silica gel system as studied by silicon-29 CP-MAS NMR spectroscopy

Static and dynamic properties of the water/amorphous silica interface: a model for the undissociated surface

“…[25,26] Our model yields ∼70% geminals and ∼30% vicinal silanol groups. This is in good agreement with second harmonic generation (SHG) [27] and evanescent wave spectroscopic experiments, [28] but a much higher fraction of geminals that found by NMR spectroscopy [29][30][31]. Clearly, experimental work is needed to resolve inconsistencies in experimental data,and better theoretical annealing of the silica surface is needed, both with respect to better annealing protocols and extending treatment to ab initio methods.…”

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

“…Besides, a portion of water characterized by δ H = 3-5 ppm at higher temperatures could transform to water with δ H = 1.1-1.7 ppm at lower temperatures. It should be noted that the 1 H MAS NMR signal at δ H ≈ 1.7 ppm observed in the spectra of silicas is attributed to protons in the surface hydroxyls with no the hydrogen bonds [57][58][59][60]. However, the signal shown in Fig.…”

Influence of glass composition and alteration solution on leached silicate glass structure: A solid-state NMR investigation

“…This confirms the attribution of the 6 ppm peaks to hydrogen-bonded hydroxyl groups. From the seminal work of Maciel et al (Chuang et al, 1993;Liu and Maciel, 1996;Chuang and Maciel, 1997), the narrow peak at 1.6-1.8 ppm is assigned to free hydroxyl groups (non-hydrogen bonded) and 2.8 ppm to silanols weakly hydrogen bonded to one another. These interactions are shown on DQ spectra in Figs.…”

“…Hydroxyl groups and molecular water are routinely observed in hydrated aluminosilicates such as albite (Kohn et al, 1989a) with 1 H chemical shifts approximately ranged from 0 to 20 ppm. The possibility of selectively probing surface silicon atoms via the protons has been used to characterize the hydrated silica surface (Maciel and Sindorf, 1980;Chuang et al, 1993;Liu and Maciel, 1996;Chuang and Maciel, 1997;Ai et al, 2002Ai et al, , 2004El Rassy and Pierre, 2005;Hu et al, 2005).…”