Interaction of single water molecules with silanols in mesoporous silica

Deep Inelastic Neutron Scattering measurements of water confined in mesoporous silica have been carried out. The experiment has been performed at room temperature on dry and on hydrated samples in order to investigate the interaction between the protons and the silanolgroups of the confining surface. With this aim we could control the hydration of the pores in such a way as to adsorb 3.0 water molecules per nm 2 , corresponding to a 1 to 1 ratio with the silanolgroups of the surface. DINS measurements directly measure the mean kinetic energy and the momentum distribution of the protons. A detailed analysis of the hydrated sample has been performed in order to separate the contributions of the protons in the system, allowing us to determine the arrangement of water molecules on the silanolgroups. We find that the hydrogen bond of the waterproton with the oxygen of the silanolgroup is much stronger than the hydrogen bonds of bulk water. DINS investigation of water confined in mesoporous silica: hydrogen momentum distribution and water-silanol bond configurations in the hydrated material.