Mimicking the solvation of aqueous Na+ in the gas phase

Patwari, G. Naresh; Lisy, James M.

doi:10.1063/1.1574018

Cited by 77 publications

(79 citation statements)

References 28 publications

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“…Studies showed that these different behaviors were largely due to their different hydration number and hydration free energies. [69,70,71,72] Recently, using SFG vibrational spectroscopy, Cremer and co-workers investigated the ion effects on the water molecules at the polymer surfactant aqueous interfaces. [73,74] In these studies, significant anion effects and insignificant cation effect were observed.…”

Section: Resultsmentioning

confidence: 99%

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Bian

Feng

Guo

et al. 2009

The Journal of Chemical Physics

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Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data, the orientational parameter D,(D= cosθ / cos 3 θ ) value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six salts caused increase of the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl ∼ NaF > KF. Since these changes can not be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational parameter D values of the interfacial water molecules changed to opposite directions for the aqueous solutions of the three sodium salts versus the aqueous solutions of the three potassium salts. These findings clearly indicated unexpected specific Na + and K + cation effects at the aqueous solution surface.These effects were not anticipated from the recent molecular dynamics (MD) simulation results, which concluded that the Na + and K + cations can be treated as small non-polarizable hard ions and they are repelled from the aqueous interfaces. These results suggest that the electrolyte aqueous solution surfaces are more complex than the currently prevalent theoretical and experimental understandings.2

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Section: Resultsmentioning

confidence: 99%

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Bian

Feng

Guo

et al. 2009

The Journal of Chemical Physics

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“…2A), suggesting that at least 16 water molecules are required to solvate and preserve the hydrated 3+ form of the metal ion. The loss of a water molecule is entropically favored over the charge separation reaction for SO 4 3+ . Also apparent in this spectrum, and others shown here, is the nodal behavior, suggestive of either shell structures of water around the central metal ion, or perhaps reflecting preferred droplet sizes upon the final Rayleigh fission of larger, highly charged droplets originating from the electrospray ionization process.…”

Section: Triply Charged Metal Ions Solvated By Watermentioning

confidence: 99%

“…Clusters containing singly charged metal ions have been formed using several different methods and the structures of these clusters have been investigated in significant detail [1][2][3][4][5][6][7]. Formation of hydrated multiply charged ions is more challenging due to competing effects of dissociation aided by Coulomb repulsion of two charged product ions [8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Formation of hydrated triply charged metal ions from aqueous solutions using nanodrop mass spectrometry

Bush

Saykally

Williams

2006

International Journal of Mass Spectrometry

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Forming hydrated clusters containing triply charged metal ions is challenging due to the competing process of dissociation by forming the metal hydroxide with one less net charge and a protonated water molecule. It is demonstrated for the first time that it is possible to form such clusters using a method we call "nanodrop mass spectrometry". Clusters of the form [M(H 2 O) n ] 3+ , where M = Ce, Eu, and La, are generated using electrospray ionization and are mass analyzed in a Fourier-transform ion cyclotron resonance mass spectrometer with an ion cell cooled to −140 °C. Clusters containing trivalent La with n ranging from 16 to over 160 can be readily produced. These clusters are stable at this temperature for many seconds, enabling all standard methods to probe structure and reactivity of these unusual species. Photodissociation experiments on extensively hydrated clusters of trivalent lanthanum using resonant infrared radiation indicate that a minimum of 17 water molecules is necessary to stabilize these trivalent clusters under the low-energy ion excitation conditions and long time frame of these experiments. These results indicate that a minimum droplet size of approximately a nanometer is necessary for these trivalent species to survive intact. This suggests that elemental speciation of trivalent metal ions from aqueous solutions should be possible using nanodrop mass spectrometry.

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“…According to this picture, it shall be hard to imagine how such longrange interactions can be so different for the Na + and the K + cations, since people already knew that the solvation of the Na + and the K + cations hardly go beyond the second solvation shell. [57,58] On the other hand, in the currently prevalent paradigm, the adsorption of the more polarizable anions to the aqueous solution surfaces should be enhanced, but not the less polarizable anions, such as the F − , and the cations, such as the Na + and the K + cations.Then the difficulties shall be the same as in the classical picture on how the significantly different Na + and the K + cation effects are originated.Richmond and co-workers observed the change of the SFG spectra for the NaF aqueous solution surfaces, [24] which is further confirmed in our measurement as reported here.They concluded that even though the F − anion concentration was 'diminished' in the top surface water layers, the presence of F − anion in the surface region can still affect the hydrogen bonding structure of the water molecules in the surface region in different ways from the larger and more polarizable Br − and I − anions. According to the same reasoning as Richmond and co-workers proposed for the F − anion, the presence of the Na + and the K + cations in the surface layers, even though diminished from the bulk concentration, can also be expected.…”

mentioning

confidence: 99%

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confidence: 99%

Spectroscopic evidence for the specific Na+ and K+ interactions with the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces

Feng

Bian

Guo

et al. 2009

The Journal of Chemical Physics

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Sum frequency generation vibrational spectra of the water molecules at the NaF and KF aqueous solution surfaces showed significantly different spectral features and different concentration dependence. This result is the first direct observation of the cation effects of the simple alkali cations, which have been believed to be depleted from the aqueous surface, on the hydrogen bonding structure of the water molecules at the electrolyte solution surfaces. These observations may provide important clue to understand the fundamental phenomenon of ions at the air/water interface. † Also Graduate University of the Chinese Academy of Sciences.* To whom correspondence should be addressed. E-mail: hongfei@iccas.ac.cn; Tel: 86-10-62555347; Fax:86-10-62563167. 1In this letter we would like to report the significantly different sum-frequency generation vibrational spectra of the NaF and KF aqueous solution surfaces. These results suggested that the ion effects on the interfacial water hydrogen bonding structure are quite different for the NaF and KF salts. These results may provide direct counterexamples to the physical picture based on the currently prevalent molecular dynamics (MD) simulations with the polarizable force field, which have predicted that the adsorption of the more polarizable anions, such as the I − and Br − anions, are significantly enhanced at the electrolyte aqueous solution surfaces, while the less polarizable anions, such as the F − and Cl − anions, and the non polarizable cations, such as the Na + and K + cations, are repelled from the electrolyte aqueous solution surfaces. [1,2,3,4,5] Recently, there have been a great deal of theoretical and experimental studies on the ion solvation and ion effects at the electrolyte aqueous solution surfaces. [1,2,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] It has been well established that the ssp SFG spectra for the neat air/water interface has two prominent features, one is the narrow peak centered at 3700cm −1 and the other is the fairly broad band in the 3000-3600cm −1 . The former is the signature of the non hydrogenbonded O-H group which sticks out of the liquid phase, i.e. the so called 'free O-H'; while the latter is the signature of the O-H stretching vibrations of the differently hydrogen-bonded water molecules on the liquid side in the vicinity of the air/water interface. [38,39,40,41,42] These signatures of the interfacial water molecules can be observed in the SFG-VS because the water molecules at the air/water interface are orientationally ordered. [38,39,40,41,42,46] It has been known that addition of the electrolytes into the bulk aqueous phase can introduce changes in the ssp SFG spectra in the hydrogen-bonded water region, i.e. 3000- [3,6,17,18,24,39,47] In order to systematically investigate the anion effects on the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces, the ssp 3 SFG-VS spectra of the NaF, NaCl, NaBr and NaI slat solution surfaces were measured by two independent groups. [17...

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Mimicking the solvation of aqueous Na+ in the gas phase

Cited by 77 publications

References 28 publications

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Formation of hydrated triply charged metal ions from aqueous solutions using nanodrop mass spectrometry

Spectroscopic evidence for the specific Na+ and K+ interactions with the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces

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