The Thermal Behavior of Silanol Groups of Silica Gel as Studied by Infrared Spectroscopy. I

Abstract

The thermal behavior of the silanol of silica gel has been studied by quantitative infrared spectroscopy. Transparent and glass-like plates of silica gel of high purity, after they had been heat-treated at various temperatures below 680 °C, were used for the measurement of OH stretching vibrations ranging from 3100 to 3800 cm−1. These absorption bands were analysed into the several component bands by the simulation method using a Dupont Co. Curve Resolver. The intensity of these bands in area were proportional to the OH concentrations as measured by the thermal method. Each component band disappeared at a temperature which was roughly equal to that obtained from the dielectric and conductivity measurements. From these results, assignment was attempted on the basis of these bands.

Temperature effects on the IR absorption bands of hydroxyl and deuteroxyl groups in silica glass

“…Indeed, the profile of the SiOH stretching mode band changes when the silica samples are subjected to external stresses, such as temperature modification or irradiation [12,28,29]. We described the band using the smallest number of components necessary to correctly reproduce its profile at each examined temperature and we studied the evolution of each component, and thus of each bond configuration, as a function of temperature in the range 290-20 K. For comparison we also examined the IR absorption band of deuteroxyl groups (SiOD) in a deuterated silica sample.…”

Surface photochemistry: the effect of surface modification on the photophysics of naphthalene and pyrene adsorbed on silica gel

“…The terminal oxygen functions -the silanols -have been shown by infrared studies to be geminal, vicinal, or isolated (15)(16)(17)(18)(19)(20)(21)(22)(23). These functions, in an amorphous framework, serve to render the silica gel surface inhomogeneous.…”

“…Heat treatment of silica gel first induces loss of the physically adsorbed water molecules and, subsequently, dehydroxylation of the silanol groups. The number of hydroxyl groups on the silica gel surface depends strongly on the temperature of pretreatment of the samples studied (15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Measurements performed by Fripiat and Uytterhoeven (21), amongst others, indicate that the amount of free water rapidly decreases with increasing temperature and, for temperatures higher than about 250°C, it is ' Publication 315 from the Photochemistry Unit.…”

Organized Silica Microspheres Carrying Ferromagnetic Cobalt Nanoparticles as a Basis for Tip Arrays in Magnetic Force Microscopy

“…The surface of the microspherical silica consists of a very small proportion of free silanols and silanols heavily hydrogen bonded among themselves and adsorbed water molecules. [21][22][23] The hydrogen bonded silanols show variations such as hydrogen bonding at the oxygen end, at the hydrogen end and at both ends. These thermally removable species are present on the walls of the inner pores as well.…”

“…The weight loss patterns in the case of the substrate silica and the cobalt-coated samples demand an understanding of the nature of thermally desorbable species on the surface of the silica spheres. The surface of the microspherical silica consists of a very small proportion of free silanols and silanols heavily hydrogen bonded among themselves and adsorbed water molecules. − The hydrogen bonded silanols show variations such as hydrogen bonding at the oxygen end, at the hydrogen end and at both ends. These thermally removable species are present on the walls of the inner pores as well.…”