Complex χ(2) spectra of air/water interfaces in the presence charged surfactants were measured by heterodyne-detected broadband vibrational sum frequency generation spectroscopy for first time. In contrast to neat water surface, signs two broad OH bands are same surfactants. The obtained clearly showed flip-flop interfacial molecules which is induced opposite charge head group With sign β(2) theoretically obtained, absolute orientation, i.e., up/down at aqueous surfaces was uniquely...

Vibrational sum-frequency generation (VSFG) spectroscopy is a powerful tool to study interfaces. Recently, multiplex heterodyne-detected VSFG (HD-VSFG) has been developed, which enables the direct measurement of complex second-order nonlinear susceptibility [χ((2))]. HD-VSFG remarkable advantages over conventional VSFG. For example, imaginary part χ((2)) [Imχ((2))] obtained with this interferometric technique counterpart infrared [Imχ((1))] and Raman [Imχ((3))] spectra in bulk, it free from...

Lipid/water interfaces and associated interfacial water are vital for various biochemical reactions, but the molecular-level understanding of their property is very limited. We investigated structure at a zwitterionic lipid, phosphatidylcholine, monolayer/water interface using heterodyne-detected vibrational sum frequency generation spectroscopy. Isotopically diluted was utilized in experiments to minimize effect intra/intermolecular couplings. It found that OH stretch band Imχ(2) spectrum...

The energetically unfavorable termination of the hydrogen-bonded network water molecules at air/water interface causes molecular rearrangement to minimize free energy. long-standing question is how minimizes surface combination advanced, surface-specific nonlinear spectroscopy and theoretical simulation provides new insights. complex χ((2)) spectra isotopically diluted surfaces obtained by heterodyne-detected sum frequency generation dynamics show excellent agreement, assuring validity...

Cell membrane/water interfaces provide a unique environment for many biochemical reactions, and associated interfacial water is an integral part of such reactions. A molecular level understanding the structure orientation at lipid/water required to realize complex chemistry biointerfaces. Here we report heterodyne-detected vibrational sum frequency generation (HD-VSFG) studies lipid monolayer/water interfaces. At charged interfaces, governed by net charge on headgroup; anionic interface, in...

Specific counterion effects represented by Hofmeister series are important for a variety of phenomena such as protein precipitations, surface tensions electrolytes solutions, phase transitions surfactants, etc. We applied heterodyne-detected vibrational sum-frequency generation spectroscopy to study the effect on interfacial water at charged interfaces and discussed observed with relevance series. Experiments were carried out model systems positively cetyltrimethylammonium...

Discussion on the structure of water surface relies accurate determination χ(2) spectrum. For obtaining spectrum air/water interface in OH stretch region, we performed heterodyne-detected vibrational sum-frequency generation measurements with a high phase accuracy, and also examined validity amplitude calibration using different non-resonant materials. In contrast to previous reports, it was concluded that imaginary part does not exhibit noticeable positive resonance low frequency region...

Imaginary chi(2) spectra of HOD at air/charged surfactant/aqueous interfaces highly resemble the IR spectrum bulk liquid HOD, showing no indication "ice-like" structure. Clearly, hydrogen bond structures charged are not like ice but very similar to structure in bulk.

Complex χ(2) spectra of buried silica/isotopically diluted water (HOD-D2O) interfaces were measured using multiplex heterodyne-detected vibrational sum frequency generation spectroscopy to elucidate the hydrogen bond structure and up/down orientation at silica/water interface different pHs. The data show that coupling (inter- and/or intramolecular coupling) plays a significant role in determining spectral feature silica/H2O indicate doublet H2O does not represent two distinct structures...

Two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) spectroscopy is performed for an aqueous interface the first time. The 2D HD-VSFG spectra in OH stretch region are obtained from a positively charged surfactant/water with isotopically diluted water (HOD/D(2)O) to reveal femtosecond dynamics of at interface. spectrum diagonally elongated immediately after photoexcitation, clearly demonstrating inhomogeneity interfacial water. This elongation almost...

Despite recent significant advances in interface-selective nonlinear spectroscopy, the topmost water structure at a charged silica surface is still not clearly understood. This because, for interfaces, only interfacial molecules layer but also large number of electric double are probed even with second-order spectroscopy. In present study, we studied negatively silica/aqueous interface pH 12 using heterodyne-detected vibrational sum frequency generation and demonstrated that spectral...

The silica/water interface is one of the most abundant charged interfaces in natural environments, and elucidation water structure at essential. In present study, we measured interface-selective vibrational (χ

The elucidation of the energy dissipation process is crucial for understanding various phenomena occurring in nature. Yet, vibrational relaxation and its timescale at water interface, where hydrogen-bonding network truncated, are not well understood still under debate. In present study, we focus on OH stretch interfacial air/water interface investigate by femtosecond time-resolved, heterodyne-detected sum-frequency generation (TR-HD-VSFG) spectroscopy. temporal change vibrationally excited...

Elucidation of the vibrational relaxation process interfacial water is indispensable for understanding energy dissipation at aqueous interface. In this study, dynamics hydrogen-bonded OH (HB OH) stretch vibration was investigated air/isotopically diluted (HOD-D2O) interface by time-resolved heterodyne-detected sum frequency generation (TR-HD-VSFG) spectroscopy. We observed temporal change excited-state band (v = 1 → 2 transition), which enables a reliable determination T1 time water. The...

The interface-sensitive spectroscopic method, sum frequency generation (SFG), has been used to investigate the interfacial water structure on a fused quartz surface modified by an octadecyltrichlorosilane (OTS) self-assembled monolayer in phosphate buffered solutions at various pHs. experimental results demonstrate that molecules quartz/OTS flip while OTS maintain their orientation when solution pH is changed from neutral acidic. show most of silanol groups still exist even after silane...

Two-dimensional heterodyne-detected vibrational sum-frequency generation (2D HD-VSFG) spectroscopy is applied to study the ultrafast dynamics of water at positively charged aqueous interfaces, and 2D HD-VSFG spectra cetyltrimethylammonium bromide (CTAB)/water interfaces in whole hydrogen-bonded OH stretch region (3000 cm(-1) ≤ ωpump 3600 cm(-1)) are measured. spectrum CTAB/isotopically diluted (HOD-D2O) interface exhibits a diagonally elongated bleaching lobe immediately after excitation,...

Abstract Interfacial water in the vicinity of lipids plays an important role many biological processes, such as drug delivery, ion transportation, and lipid fusion. Hence, molecular‐level elucidation properties at interfaces is utmost importance. We report two‐dimensional heterodyne‐detected vibrational sum frequency generation (2D HD‐VSFG) study OH stretch HOD charged interfaces, which shows that hydrogen bond dynamics interfacial differ drastically, depending on lipids. The data indicate...

Ultrafast vibrational dynamics of hydrogen bond network at the air∕water interface is revealed by two-dimensional heterodyne-detected sum frequency generation (2D HD-VSFG) spectroscopy. Three diagonal peaks are clearly observed in 2D HD-VSFG spectrum, which correspond to negative and positive hydrogen-bonded OH stretch bands "free" band steady-state spectrum. A diagonally elongated bleaching lobe 0 ps indicates that it partly inhomogeneously broadened. This elongation vanishes a few hundred...

Heterodyne-detected vibrational sum frequency generation spectroscopy was applied to the water surface for measuring imaginary part of second-order nonlinear susceptibility (Im χ(2)) spectrum in bend region first time. The observed Im χ(2) shows an overall positive band around 1650 cm–1, contradicting former theoretical predictions. We further found that NaI aqueous solution exhibits even larger band, which is apparently contrary flip-flop orientation water. These unexpected observations are...

The interfacial water structures at surfaces of an as-prepared TiO2 and the after UV irradiation were investigated by sum frequency generation (SFG) spectroscopy quartz crystal microbalance (QCM). It was shown that illumination led to increase in amount not only adsorbed as a whole but also ordered on surface, confirming hydrophilicity surface.

Hydrated electrons are the most fundamental anion species, consisting only of and surrounding water molecules. Although hydrated have been extensively studied in bulk aqueous solutions, even their existence is still controversial at surface. Here, we report observation characterization air/water interface using new time-resolved interface-selective nonlinear vibrational spectroscopy. With generation by ultraviolet photoirradiation, observed appearance a strong transient band OH stretch...

Femtosecond vibrational dynamics at the air/water interface is investigated by time-resolved heterodyne-detected sum frequency generation (TR-HD-VSFG) spectroscopy and molecular (MD) simulation. The low- high-frequency sides of hydrogen-bonded (HB) OH stretch band are selectively excited with special attention to bandwidth energy pump pulses. Narrow bleach observed immediately after excitation side HB ∼3500 cm(-1), compared broad low-frequency ∼3300 cm(-1). However, spectra two different...