title: Sol-to-Gel Transition in Fast Evaporating Systems Observed by in Situ Time-Resolved Infrared Spectroscopy.
abstract: The in situ observation of a sol-to-gel transition in fast evaporating systems is a challenging task and the lack of a suitable experimental design, which includes the chemistry and the analytical method, has limited the observations. We synthesise an acidic sol, employing only tetraethylorthosilicate, SiCl4 as catalyst and deuterated water; the absence of water added to the sol allows us to follow the absorption from the external environment and the evaporation of deuterated water. The time-resolved data, obtained by attenuated total reflection infrared spectroscopy on an evaporating droplet, enables us to identify four different stages during evaporation. They are linked to specific hydrolysis and condensation rates that affect the uptake of water from external environment. The second stage is characterized by a decrease in hydroxyl content, a fast rise of condensation rate and an almost stationary absorption of water. This stage has been associated with the sol-to-gel transition.
authors.affiliation: Laboratorio di Scienza dei Materiali e Nanotecnologie, DADU, Università di Sassari, Palazzo Pou Salid, Piazza Duomo 6, 07041 Alghero (Italy). plinio@uniss.it.
authors.forename: Plinio
authors.initials: P
authors.lastname: Innocenzi
authors.affiliation: Laboratorio di Scienza dei Materiali e Nanotecnologie, DADU, Università di Sassari, Palazzo Pou Salid, Piazza Duomo 6, 07041 Alghero (Italy).
authors.forename: Luca
authors.initials: L
authors.lastname: Malfatti
authors.affiliation: Laboratorio di Scienza dei Materiali e Nanotecnologie, DADU, Università di Sassari, Palazzo Pou Salid, Piazza Duomo 6, 07041 Alghero (Italy).
authors.forename: Davide
authors.initials: D
authors.lastname: Carboni
authors.affiliation: Department of Materials Science, Graduate School of Engineering and International Laboratory of Materials Science and Nanotechnology (iLMNT), Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan).
authors.forename: Masahide
authors.initials: M
authors.lastname: Takahashi
keywords: absorption; infrared spectroscopy; silica; sol-gel transitions; time-resolved analysis