Probing Hydrogen-Bonding Interactions of Water Molecules Adsorbed on Silica, Sodium Calcium Silicate, and Calcium Aluminosilicate Glasses

Vibrational sum frequency generation (SFG) spectroscopy was used to study how hydrogen bonding interactions of physisorbed water layers vary with the glass composition and surface condition. Three different glass materials were used: amorphous silica (fused quartz), sodium calcium silicate (also called soda lime silica), and calcium aluminosilicate (boron-/fluorine-free E-glass). Two different surface conditions were compared: (i) a mechanically polished, fire-polished, and then annealed surface and (ii) an acid-leached surface (pH 1, 90 °C, 24 h). Compositional and structural information obtained by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and attenuated total reflection infrared spectroscopy were correlated with SFG spectral features. The temperature dependence of SFG spectral features revealed that regardless of the glass composition, the glass surface is free of physisorbed water at 250 °C, and during cooling in ambient air, it starts absorbing water at a temperature corresponding to a relative humidity of 1-2%. Humidity-controlled SFG measurements at room temperature showed that the hydrogen bonding interactions of water physisorbed on the glass surface cleaned with UV/O₃ are quite different depending on the glass composition and surface preparation history. This finding will be useful in understanding how surface properties of different glasses are altered by humidity in ambient air.