Authors: Jun Abe Nobuo Hirano Noriyoshi Tsuchiya
Publish Date: 2012/06/30
Volume: 47, Issue: 23, Pages: 7971-7977
Abstract
The structure of water under high temperature–pressure conditions in mesospace was investigated by measuring the infrared spectra of water in mesoporous silica Absorption peaks attributed to OHstretching vibration of water in mesoporous silica were detected at lower wavenumbers as compared with bulk water and the absorption peak positions were dependent on pore diameter For small pore diameters 3–20 nm absorption peak positions of water were detected at lower wavenumbers ca 3300 cm−1 at 400 °C while for larger pore diameters 30–50 nm the peaks were detected at higher wavenumbers ca 3500 cm−1 We attribute these features to the effects of mesoporous silica surface structure on the structural and vibrational modes of water Furthermore absorption peak positions changed significantly at different pore sizes 20 and 30 nm indicating that the structure of water in small pores approaches a more icelike structure Based on our experimental results the structured water layer in mesoporous silica is estimated to be at least 10 nm thick which is thicker than that previously documented in molecular dynamic simulation studies where the thickness of structured water was found to be two or three layers from the surface
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