Atmospheric Spectroscopy and Photochemistry at Environmental Water Interfaces

Zhong, Jie; Kumar, Manoj; Anglada, Josep M.; Martins‐Costa, Marilia T. C.; Ruiz‐López, Manuel F.; Zeng, Xiao Cheng; Francisco, Joseph S.

doi:10.1146/annurev-physchem-042018-052311

Cited by 59 publications

(80 citation statements)

References 150 publications

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“…[14][15][16]24,25 The study is also relevant to the usage of droplets as micro and nano-reactors for accelerating chemical reactions [26][27][28][29][30][31] and to electrification phenomena in atmospheric aerosols. [32][33][34][35][36] In previous research we found a bi-layer structure of an aqueous charged droplet by using atomistic modeling, 37 as shown in the schematic in Fig. 1.…”

Section: Introductionmentioning

confidence: 91%

Molecular Characterization of the Surface Excess Charge Layer in Droplets

Kwan¹,

Consta²

2020

Preprint

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<div>Charged droplets play a central role in native mass spectrometry, atmospheric aerosols and in serving as micro-reactors for accelerating chemical reactions. The surface excess charge layer in droplets has often been associated with distinct chemistry. Using molecular simulations for droplets with Na+ and Cl- ions we have found that this layer is ≈ 1.5−1.7 nm thick and depending on the droplet size it includes 33%-55% of the total number of ions. Here, we examine the eﬀect of droplet size and nature of ions in the structure of the surface excess charge layer by using molecular dynamics. We ﬁnd that in the presence of simple ions the thickness of the surface excess charge layer is invariant not only with respect to droplet size but also with respect to the nature of the simple ions and it is not sensitive to ﬁne details of diﬀerent force ﬁelds used in our simulations.</div><div> In the presence of macroions the excess surface charge layer may extend to 2.0. nm. For the same droplet size, iodide and model hydronium ions show considerably higher concentration than the sodium and chloride ions. <br></div><div>We also ﬁnd that diﬀerences in the average water dipole orientation in the presence of cations and anions in this layer are reﬂected in the charge distributions. Within the surface charge layer, the number of hydrogen bonds reduces gradually relative to the droplet interior where the number of hydrogen bonds is on the average 2.9 for droplets of diameter < 4 nm and 3.5 for larger droplets. The decrease in the number of hydrogen bonds from the interior to the surface is less pronounced in larger droplets. In droplets with diameter < 4 nm and high concentration of ions the charge of the ions is not compensated only by the solvent polarization charge but by the total charge that also includes the other free charge. This ﬁnding shows exceptions to the commonly made assumption that the solvent compensates the charge of the ions in solvents with very high dielectric constant. The study provides molecular insight into the bi-layer droplet structure assumed in the equilibrium partitioning model of C. Enke and assesses critical assumptions of the Iribarne-Thomson model for the ion-evaporation mechanism. <br></div>

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Section: Introductionmentioning

confidence: 91%

Molecular Characterization of the Surface Excess Charge Layer in Droplets

Kwan¹,

Consta²

2020

Preprint

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“…Ion hydration and "specific ion" effects, 1,2 in the sense of Hofmeister's ranking of the lyotropic effects of aqueous ions, [2][3][4][5][6] play a significant role in the chemistry of the air/ water interface. 1,[7][8][9] This is an importance interface for atmospheric chemistry, [10][11][12][13] where for example interfacial Cl − and Br − are relevant to the chemistry of seawater aerosols, [14][15][16][17] while NO − 3 plays a role in atmospheric NO x chemistry. 13,18 Brine rejection at the seawater/ice interface has profound consequences for vertical circulation in Arctic and Antarctic waters.…”

Section: Introductionmentioning

confidence: 99%

“…1,[7][8][9] This is an importance interface for atmospheric chemistry, [10][11][12][13] where for example interfacial Cl − and Br − are relevant to the chemistry of seawater aerosols, [14][15][16][17] while NO − 3 plays a role in atmospheric NO x chemistry. 13,18 Brine rejection at the seawater/ice interface has profound consequences for vertical circulation in Arctic and Antarctic waters. 19,20 It is well established that certain ions partition preferentially at the liquid/vapor interface, 1,9,[21][22][23][24][25][26][27][28][29] and the effect is reproducible in molecular dynamics (MD) simulations.…”

Section: Introductionmentioning

confidence: 99%

Probing Interfacial Effects on Ionization Energies: The Surprising Banality of Anion-Water Hydrogen Bonding at the Air/Water Interface

Paul¹,

Herbert²

2021

Preprint

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Liquid microjet photoelectron spectroscopy is an increasingly common technique to measure vertical ionization energies (VIEs) of aqueous solutes, although the interpretation of these experiments is subject to questions regarding sensitivity to bulk versus interfacial solvation environments. Here, we compute aqueous-phase VIEs for a set of inorganic anions, some of which partition preferentially at the air/water interface, using a combination of molecular dynamics simulations and electronic structure calculations. The results are in excellent agreement with experiment, regardless of whether the simulation data are restricted to ions at the air/water interface or to those in bulk liquid water. Although the computed VIEs are sensitive to ion-water hydrogen bonding, we find that the short-range solvation structure is sufficiently similar in the bulk and interfacial environments that it proves impossible to discriminate between the two on the basis of the VIE, a conclusion that has important implications for the interpretation of liquid-phase photoelectron spectroscopy. More generally, analysis of the simulation data suggests that partitioning of soft anions at the air/water interface is largely a second (or third) solvation shell effect, arising from disruption of water-water hydrogen bonds and not from significant changes in first-shell anion-water hydrogen bonding. <br>

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“…[11][12][13][14] Indeed, the so-called "on-water" catalytic effect [15] presently represents one of the most fascinating issues in atmospheric chemistry. [16,17] The rate of many reactions increases when they occur at aqueous interfaces, sometimes by several orders of magnitude with respect to the same process in gas phase or bulk water. However, there is not yet a complete understanding of this phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Isoprene Reactivity on Water Surfaces from ab initio QM/MM Molecular Dynamics Simulations

Martins‐Costa

Ruiz‐López

2020

ChemPhysChem

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Isoprene is the most abundant volatile organic compound in the atmosphere after methane. While gas-phase processes have been widely studied, the chemistry of isoprene in aqueous environments is less well known. Nevertheless, some experiments have reported unexpected reactivity at the air-water interface. In this work, we have carried out combined quantumclassical molecular dynamics simulations of isoprene at the airwater interface, as well as ab initio and density functional theory calculations on isoprene-water complexes. We report the first calculation of the thermodynamics of adsorption of isoprene at the water surface, examine how hydration influences its electronic properties and reactivity indices, and estimate the OH-initiated oxidation rate. Our study indicates that isoprene interacts with the water surface mainly through HÀ π bonding. This primary interaction mode produces strong fluctuations of the π and π* bond stabilities, and therefore of isoprene's chemical potential, nucleophilicity and ionization potential, anticipating significant dynamical effects on its reactivity at the air-water interface. Using data from the literature and free energies reported in our work, we have estimated the rate of the OH-initiated oxidation process at the air-water interface (5.0 × 10 12 molecule cm À 3 s À 1) to be about 7 orders of magnitude larger than the corresponding rate in the gas phase (8.2 × 10 5 molecule cm À 3 s À 1). Atmospheric implications of this result are discussed.

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Atmospheric Spectroscopy and Photochemistry at Environmental Water Interfaces

Cited by 59 publications

References 150 publications

Molecular Characterization of the Surface Excess Charge Layer in Droplets

Molecular Characterization of the Surface Excess Charge Layer in Droplets

Probing Interfacial Effects on Ionization Energies: The Surprising Banality of Anion-Water Hydrogen Bonding at the Air/Water Interface

Isoprene Reactivity on Water Surfaces from ab initio QM/MM Molecular Dynamics Simulations

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