Nonlinear Vibrational Spectroscopic Studies of the Adsorption and Speciation of Nitric Acid at the Vapor/Acid Solution Interface

Soule, Melissa C. Kido; Blower, Patrick G.; Richmond, Geraldine L.

doi:10.1021/jp0686994

Cited by 62 publications

(39 citation statements)

References 56 publications

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“…In bulk water, nitrate is surrounded by a solvent cage that facilitates both the recombination of the NO 2 and OH radicals produced by reaction and their deactivation by collision with solvent molecules, thus decreasing the photolysis quantum yield. ,,, MD simulations have shown that when halide anions (especially bromide) are present, nitrate ions are dragged closer to the interface so that the water solvent cage surrounding them is reduced, , arguably making the escape of NO 2 to the gas phase easier. ,,− Nevertheless, despite the large amount of work done on nitrate photochemistry, open issues remain that are not yet completely understood. For instance, it was recently shown that an important part of nitric acid remains undissociated at the air–water interface, ,− and the relevance of the corresponding photochemistry is still undetermined.…”

Section: Photochemistry Of Oh Precursorsmentioning

confidence: 99%

Photoinduced Oxidation Reactions at the Air–Water Interface

et al. 2020

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Chemistry on water is a fascinating area of research. The surface of water and the interfaces between water and air or hydrophobic media represent asymmetric environments with unique properties that lead to unexpected solvation effects on chemical and photochemical processes. Indeed, the features of interfacial reactions differ, often drastically, from those of bulk-phase reactions. In this Perspective, we focus on photoinduced oxidation reactions, which have attracted enormous interest in recent years because of their implications in many areas of chemistry, including atmospheric and environmental chemistry, biology, electrochemistry, and solar energy conversion. We have chosen a few representative examples of photoinduced oxidation reactions to focus on in this Perspective. Although most of these examples are taken from the field of atmospheric chemistry, they were selected because of their broad relevance to other areas. First, we outline a series of processes whose photochemistry generates hydroxyl radicals. These OH precursors include reactive oxygen species, reactive nitrogen species, and sulfur dioxide. Second, we discuss processes involving the photooxidation of organic species, either directly or via photosensitization. The photochemistry of pyruvic acid and fatty acid, two examples that demonstrate the complexity and versatility of this kind of chemistry, is described. Finally, we discuss the physicochemical factors that can be invoked to explain the kinetics and thermodynamics of photoinduced oxidation reactions at aqueous interfaces and analyze a number of challenges that need to be addressed in future studies.

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Section: Photochemistry Of Oh Precursorsmentioning

confidence: 99%

Photoinduced Oxidation Reactions at the Air–Water Interface

et al. 2020

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“…At the molecular level, the changes in p K a are attributed to the preferential partitioning of neutral species at the air–water interface due to the energy cost associated with ions that are less solvated at the interface. Understanding local surface solvation effects and their impact on p K a is especially important, in part due to the key role that acidic and basic aqueous solutions play in environmental and atmospheric chemistry. − Additionally, surface p K a impacts interfacial biochemical phenomenon, such as protein folding and unfolding, owing to the pH dependence of amino acid protonation/deprotonation…”

Section: Introductionmentioning

confidence: 99%

Anomalous pH-Dependent Enhancement of p-Methyl Benzoic Acid Sum-Frequency Intensities: Cooperative Surface Adsorption Effects

et al. 2020

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Vibrational sum-frequency generation (SFG) spectroscopy is used to determine the surface pK a of p-methyl benzoic acid (pMBA) at the air–water interface by monitoring the carbonyl and carboxylate stretching modes over the pH range of 2 to 12. The SFG intensities of pMBA and its conjugate base, p-methyl benzoate (pMBA−), exhibit an anomalously large enhancement over a narrow pH range (∼0.5) centered at pH 6.3 near the SFG-determined surface pK a, 5.9 ± 0.1. The increase in the surface pK a relative to the bulk value of 4.34 is consistent with the trend previously observed for long chain carboxylic acids in which the surface pK a is higher than the bulk solution pK a. SFG polarization studies help distinguish the orientation and number density contributions to this observed anomalous surface phenomenon. The large SFG intensity increase is attributed to an increase in the pMBA and pMBA− surface concentrations in this narrow pH range due to a cooperative adsorption effect between pMBA and pMBA−. This cooperativity is manifested only on the 2D air–water interface, where the interactions between the acid and base are not as dielectrically screened as in the aqueous bulk phase. Surface effects are critical to understanding and controlling the reactivity, solubility, and behavior of organic acids at interfaces and can have an impact on biomedical applications.

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“…VOCs affect hydroxyl (OH) radical and ozone formation and oxidation processes (Jacob et al, 2005; Hüve et al, 2007). Ozone formation in photochemical reactions requires NOx and reactive VOCs (Crutzen, 1979; Logan, 1985), and for this reason, it is important to quantify seasonal VOC emission fluxes from different sources. These sources should be quantified more accurately, because several studies have shown that measured and modeled ozone deposition fluxes and OH radical reactivities include significant differences (Mogensen et al, 2011; Wolfe et al, 2011; Rannik et al, 2012; Zhou et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Interannual and Seasonal Dynamics of Volatile Organic Compound Fluxes From the Boreal Forest Floor

et al. 2019

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In the northern hemisphere, boreal forests are a major source of biogenic volatile organic compounds (BVOCs), which drive atmospheric processes and lead to cloud formation and changes in the Earth’s radiation budget. Although forest vegetation is known to be a significant source of BVOCs, the role of soil and the forest floor, and especially interannual variations in fluxes, remains largely unknown due to a lack of long-term measurements. Our aim was to determine the interannual, seasonal and diurnal dynamics of boreal forest floor volatile organic compound (VOC) fluxes and to estimate how much they contribute to ecosystem VOC fluxes. We present here an 8-year data set of forest floor VOC fluxes, measured with three automated chambers connected to the quadrupole proton transfer reaction mass spectrometer (quadrupole PTR-MS). The exceptionally long data set shows that forest floor fluxes were dominated by monoterpenes and methanol, with relatively comparable emission rates between the years. Weekly mean monoterpene fluxes from the forest floor were highest in spring and in autumn (maximum 59 and 86 μg m -2 h -1 , respectively), whereas the oxygenated VOC fluxes such as methanol had highest weekly mean fluxes in spring and summer (maximum 24 and 79 μg m -2 h -1 , respectively). Although the chamber locations differed from each other in emission rates, the inter-annual dynamics were very similar and systematic. Accounting for this chamber location dependent variability, temperature and relative humidity, a mixed effects linear model was able to explain 79–88% of monoterpene, methanol, acetone, and acetaldehyde fluxes from the boreal forest floor. The boreal forest floor was a significant contributor in the forest stand fluxes, but its importance varies between seasons, being most important in autumn. The forest floor emitted 2–93% of monoterpene fluxes in spring and autumn and 1–72% of methanol fluxes in spring and early summer. The forest floor covered only a few percent of the forest stand fluxes in summer.

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Nonlinear Vibrational Spectroscopic Studies of the Adsorption and Speciation of Nitric Acid at the Vapor/Acid Solution Interface

Cited by 62 publications

References 56 publications

Photoinduced Oxidation Reactions at the Air–Water Interface

Photoinduced Oxidation Reactions at the Air–Water Interface

Anomalous pH-Dependent Enhancement of p-Methyl Benzoic Acid Sum-Frequency Intensities: Cooperative Surface Adsorption Effects

Interannual and Seasonal Dynamics of Volatile Organic Compound Fluxes From the Boreal Forest Floor

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