Hydrogen bonding strength of interfacial water determined with surface sum-frequency generation

No Ice-Like Water at Aqueous Biological Interfaces

“…The fit parameters reflecting the simplification of the SFG spectra upon isotopic dilution are shown in Tables 1 and 2 for the waterlipid and water-protein interfaces, respectively. This observation cannot be reconciled with the presence of two distinct sub-ensembles of strongly ('ice-like') and weakly ('liquid-like') hydrogen-bonded interfacial water [17][18][19][20][21]. If the two peaks are due to two different types of OD groups, i.e.…”

“…It is thus evident that isotopic dilution is an essential tool to identify different water species at biological aqueous interfaces [18]. In addition to isotope dilution, there are two additional SFG-based approaches that can shed additional light on the structure of water at biological interfaces.…”

The elusive silica/water interface: isolated silanols under water as revealed by vibrational sum frequency spectroscopy

“…Nonetheless, intrinsic surface specific techniques, such as vibrational sum frequency spectroscopy (VSFS) 12,13 and second harmonic generation (SHG), 14 have been able to provide information on the interfacial water in close or direct proximity to the silica surface, and in particular, upon variation of the solution pH. [15][16][17][18][19][20][21][22][23][24][25][26] The VSFS spectra of the silica/water interface are characterized by two broad bands centred at B3200 cm À1 and B3400 cm…”

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“…By general consensus, these O-H resonances are believed to mostly represent symmetric stretch of anisotropically oriented tetrahedrally hydrogen bonded water molecules (~3150 cm -1 , 'ice-like'), asymmetrically hydrogen bonded water molecules (~3400 cm -1 , 'liquid-like') and the dangling O-H stretch, free from hydrogen bonding (~3700 cm -1 , 'gas-like'). The assignation of these peaks is probably correct but not assured as Sovago et al (2008aSovago et al ( , 2008bSovago et al ( , 2009 disagree with these assignments with Shen (2008, 2009) dissenting from this view. Certainly, the model used by Sovago et al (2008aSovago et al ( , 2009, which assumes that liquid HOD behaves no differently from H 2 O in its hydrogen bonding, is open to question.…”

“…The assignation of these peaks is probably correct but not assured as Sovago et al (2008aSovago et al ( , 2008bSovago et al ( , 2009 disagree with these assignments with Shen (2008, 2009) dissenting from this view. Certainly, the model used by Sovago et al (2008aSovago et al ( , 2009, which assumes that liquid HOD behaves no differently from H 2 O in its hydrogen bonding, is open to question. The dangling O-H stretch may be further explained by making use of the infrared spectra of oxonium ion clusters (Shin et al 2004).…”