Shedding light on water structure at air–aqueous interfaces: ions, lipids, and hydration

Allen, Heather C.; Casillas-Ituarte, Nadia N.; Sierra‐Hernández, M. Roxana; Chen, Xiangke; Tang, Cheng Y.

doi:10.1039/b901209e

Cited by 119 publications

(185 citation statements)

References 153 publications

(210 reference statements)

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“…1A and B to previously published surface water structure spectra of other salts reveals some interesting differences. SFG spectra of aqueous sodium halide (12,13), ammonium and sodium sulfate (13), and divalent-cation nitrate salt solutions (12) reveal enhancements in the 3; 400 cm −1 region, although the aqueous ammonium chloride salt spectrum (13) showed enhancement at 3; 300 cm −1 as is observed here for MgCl 2 . Also different than observed in Fig.…”

Section: Resultsmentioning

confidence: 60%

“…Before MgCl 2 addition, the spectrum of neat water reveals a broad continuum that spans from 3,000 to 3; 600 cm −1 and is assigned to the OH stretching modes of hydrogen-bonded water molecules. The assignments within this continuum are controversial and still under discussion (12); however, as the frequency of the OH stretching modes increases, the strength of the hydrogen bonds between water molecules decreases (12,13). This spectral region is also affected by coupling (14) and the collective nature of the vibrations (13).…”

Section: Resultsmentioning

confidence: 99%

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Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry

Casillas-Ituarte

Callahan

Tang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly in coastal urban regions. The study of the interactions of these ions with water molecules at the aqueous surface helps to elucidate the role of inorganic cations and anions in atmospheric processes. We present surface vibrational sum frequency generation (SFG) spectroscopic and molecular dynamics (MD) studies of aqueous MgCl 2 surfaces as models of marine aerosol. Spectroscopy results reveal that the disturbance of the hydrogen bonding environment of the air/aqueous interface is dependent on the MgCl 2 concentration. At low concentrations (<1 M) minor changes are observed. At concentrations above 1 M the hydrogen bonding environment is highly perturbed. The 2.1 M intermediate concentration solution shows the largest SFG response relative to the other solutions including concentrations as high as 4.7 M. The enhancement of SFG signal observed for the 2.1 M solution is attributed to a larger SFG-active interfacial region and more strongly oriented water molecules relative to other concentrations. MD simulations reveal concentration dependent compression of stratified layers of ions and water orientation differences at higher concentrations. SFG and MD studies of the dangling OH of the surface water reveal that the topmost water layer is affected structurally at high concentrations (>3.1 M). Finally, the MgCl 2 concentration effect on a fatty acid coated aqueous surface was investigated and SFG spectra reveal that deprotonation of the carboxylic acid of atmospherically relevant palmitic acid (PA) is accompanied by binding of the Mg 2þ to the PA headgroup. magnesium chloride | fatty acid | air/aqueous interface | sum frequency spectroscopy | molecular dynamics I norganic salts present in marine boundary layer (MBL) aerosol originate from turbulent wave action at the surface of the ocean (1). These aerosols, typically of the micron size range and smaller, travel over continental regions by being entrained in the air mass in which they were created, and have been detected more than 900 km inland (2). Aerosols play a key role in the modification of global climate through their effect on cloud condensation nuclei prevalence, radiative balance, and level of precipitation (3). Aerosol composition and size have also been correlated to thunderstorm severity (4). Alkali metals (Na, K, Li, and Rb), alkaline earth metals (Mg, Ca), and ammonium (NH þ 4 ) make up the majority of cationic species, and halides (F, Cl, Br, and I) and oxidized sulfur and nitrogen ions make up the majority of inorganic anionic species found in MBL aerosol (5, 6). While calcium and magnesium are the most prevalent divalent cations in seawater and MBL aerosols, chloride anion is the dominant halide species (5). Although recent cloud drop measurements in the MBL show that calcium concentrations are about four times higher than magnesium concentrations, (6) the small size and high charge density of Mg 2þ gives rise to a strongly hydrated complex in aqueous solut...

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry

Casillas-Ituarte

Callahan

Tang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…Using deuterated and normal water, Allen and coworkers [Ma et al, 2007;Allen et al, 2009] showed that with increasing surface coverage of a phospholipid monolayer, the OD (or OH) dangling bond peak at ∼2735 cm −1 (3710 cm −1 ) does not simply disappear but is broadened and slightly red shifted due to an increased integration into the surface water network and/or confinement and perturbation imposed by the monolayer molecules. Wavenumbers of 2700 cm −1 and 3625 cm −1 have been reported for a densely covered H 2 O and D 2 O surface, respectively.…”

Section: Role Of Confined Watermentioning

confidence: 99%

Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

Laß¹,

Friedrichs²

2011

J. Geophys. Res.

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Natural nanolayers originating from sea surface and subsurface water samples collected in the Baltic Sea have been investigated using surface‐sensitive vibrational sum frequency generation (VSFG) spectroscopy. Distinct spectral signatures of CH and OH bond stretch vibrations have been detected at wavenumbers ranging from 2700 to 3900 cm−1. Measured water‐air interface spectra as well as observed signal intensity trends are discussed in terms of composition and structure of the natural organic nanolayer. Reasoning was based on the comparison with reference spectra, spectral trends inferred from previous VSFG studies, reported average composition of dissolved organic matter in seawater, and simplified assumption that surfactants can be classified as soluble (wet) and insoluble (dry) surfactants. Wet surfactants have been found to be dominant, and often lipid‐like compounds form a very dense surfactant nanolayer. Supported by comparison spectra of xanthan gum solutions, the observed VSFG spectral signatures were tentatively assigned to lipopolysaccharides or other lipid‐like compounds embedded in colloidal matrices of polymeric material. In addition, VSFG spectra of a polluted harbor water sample and a water sample covered with diesel oil are reported.

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“…[29][30][31][32][33][34][35][36][37][38][39][40] In particular, this technique has been applied to the in situ investigation of biomolecules, including peptides, [41][42][43][44][45][46][47][48][49][50][51][52] proteins, and DNA. [75][76][77][78][79] Previous work from our lab has demonstrated the ability of SFG spectroscopy to detect substrate modifications through a layer of adherent, fixed cells 80 and through living, nonadherent cells.…”

Section: Introductionmentioning

confidence: 99%

In vitro observation of dynamic ordering processes in the extracellular matrix of living, adherent cells

et al. 2011

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Collecting information at the interface between living cells and artificial substrates is exceedingly difficult. The extracellular matrix (ECM) mediates all cell-substrate interactions, and its ordered, fibrillar constituents are organized with nanometer precision. The proceedings at this interface are highly dynamic and delicate. In order to understand factors governing biocompatibility or its counterpart antifouling, it is necessary to probe this interface without disrupting labels or fixation and with sufficient temporal resolution. Here the authors combine nonlinear optical spectroscopy (sumfrequency-generation) and microscopy (second-harmonic-generation), fluorescence microscopy, and quartz crystal microgravimetry with dissipation monitoring in a strategy to elucidate molecular ordering processes in the ECM of living cells. Artificially (fibronectin and collagen I) and naturally ordered ECM fibrils (zebrafish, Danio rerio) were subjected to nonlinear optical analysis and were found to be clearly distinguishable from the background signals of diffusive proteins in the ECM. The initial steps of fibril deposition and ordering were observed in vitro as early as 1 h after cell seeding. The ability to follow the first steps of cell-substrate interactions in spite of the low amount of material present at this interface is expected to prove useful for the assessment of biomedical and environmental interfaces.

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Shedding light on water structure at air–aqueous interfaces: ions, lipids, and hydration

Cited by 119 publications

References 153 publications

Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry

Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry

Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

In vitro observation of dynamic ordering processes in the extracellular matrix of living, adherent cells

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Shedding light on water structure at air–aqueous interfaces: ions, lipids, and hydration

Cited by 119 publications

References 153 publications

Surface organization of aqueous MgCl 2 and application to atmospheric marine aerosol chemistry

Surface organization of aqueous MgCl 2 and application to atmospheric marine aerosol chemistry

Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

In vitro observation of dynamic ordering processes in the extracellular matrix of living, adherent cells

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Product

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Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry

Surface organization of aqueous MgCl ₂ and application to atmospheric marine aerosol chemistry