Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Moussa, Samar G.; Finlayson-Pitts, Barbara J.

doi:10.1039/c000447b

Cited by 28 publications

(41 citation statements)

References 78 publications

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“…150,151 The fundamental nature of the OH + -CQC and -CH 3 surface reaction was further investigated by D'Andrea et al 136 when they examined the reaction of OH radicals with alkaneand alkene-thiol self-assembled monolayers deposited on gold using molecular beam scattering methods in an UHV environment. Coupled with RAIRS, this experiment showed real-time changes in surface functionalization over the entire course of OH exposure (as opposed to after different, long-exposure times 143 ), thus providing a more detailed spectroscopic picture of the progression of the reaction. Following examination of spectral changes during exposure, reaction mechanisms of OH with both self-assembled monolayers were proposed.…”

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Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces

et al. 2016

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Heterogeneous chemistry of the most important atmospheric oxidants, O 3 , NO 3 , and OH, plays a central role in regulating atmospheric gas concentrations, processing aerosols, and aging materials. Recent experimental and computational studies have begun to reveal the detailed reaction mechanisms and kinetics for gas-phase O 3 , NO 3 , and OH when they impinge on organic surfaces. Through new research approaches that merge the fields of traditional surface science with atmospheric chemistry, researchers are developing an understanding for how surface structure and functionality affect interfacial chemistry with this class of highly oxidizing pollutants. Together with future research initiatives, these studies will provide a more complete description of atmospheric chemistry and help others more accurately predict the properties of aerosols, the environmental impact of interfacial oxidation, and the concentrations of tropospheric gases.

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Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces

et al. 2016

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“…A detailed description of the procedure for depositing the SAMs onto the ATR crystal has been described previously. 45,46,59,60 Exposure of surfaces to HNO 3 and H 2 O…”

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“…The ATR crystal was placed in a horizontal flow-through cell (Pike Technologies) with a head space of B500 mL, 60 where it was purged overnight with a dry stream of N 2 inside the sample compartment of a Mattson Galaxy 5020 FTIR spectrometer. The stainless steel parts of the ATR cell were coated with halocarbon wax, and Teflon tubing and connections were used to minimize loss of HNO 3 on the sampling lines and walls of the cell.…”

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confidence: 99%

“…Organic trichlorosilanes form SAMs on both silica surfaces and on germanium, 54,60 although those on Ge are less stable. 54,60,[95][96][97][98][99][100][101] Nevertheless, SAMs are expected to cover the entire surface. Given the presence of the double bond in the SAM, the irregular SiO x coating of the Ge, and the instability of the SAM on Ge, some disorder is expected in the film.…”

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Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Moussa

Stern

Raff

et al. 2013

Phys. Chem. Chem. Phys.

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Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer surface of a germanium infrared-transmitting attenuated total reflectance (ATR) crystal that was coated with a thin layer of silicon oxide (SiO x ). The SAM was exposed at 298 AE 2 K to dry HNO 3 in a flow of N 2 , followed by HNO 3 in humid N 2 at a controlled relative humidity (RH) between 20-90%. For comparison, similar studies were carried out using a similar crystal without the SAM coating. Changes in the surface were followed using Fourier transform infared spectroscopy (FTIR). In the case of the SAMcoated crystal, molecular HNO 3 and smaller amounts of NO 3 À ions were observed on the surface upon exposure to dry HNO 3 . Addition of water vapor led to less molecular HNO 3 and more H 3 O + and NO 3 À complexed to water, but surprisingly, molecular HNO 3 was still evident in the spectra up to 70% RH.This suggests that part of the HNO 3 observed was initially trapped in pockets within the SAM and shielded from water vapor. After increasing the RH to 90% and then exposing the film to a flow of dry N 2 , molecular nitric acid was regenerated, as expected from recombination of protons and nitrate ions as water evaporated. The nitric acid ultimately evaporated from the film. On the other hand, exposure of the SAM to HNO 3 and H 2 O simultaneously gave only hydronium and nitrate ions. Molecular dynamics simulations of defective SAMs in the presence of HNO 3 and water predict that nitric acid intercalates in defects as a complex with a single water molecule that is protected by alkyl chains from interacting with additional water molecules. These studies are consistent with the recently proposed hydrophobic nature of HNO 3 . Under atmospheric conditions, if HNO 3 is formed in organic layers on surfaces in the boundary layer, e.g. through NO 3 or N 2 O 5 reactions, it may exist to a significant extent in its molecular form rather than fully dissociated to nitrate ions. IntroductionNitric acid is considered to be the end-product of oxidation of oxides of nitrogen in the atmosphere. 1 This acid reacts with ammonia and amines to form solid or aqueous phase nitrate particles, and can also be taken up into other types of atmospheric particles. Removal of gaseous HNO 3 and particulate nitrates takes place primarily through wet and dry deposition, in what were once considered to be terminal removal processes. However, there are now a number of laboratory and field studies that suggest that nitric acid can be converted back into gaseous oxides of nitrogen such as NO, NO 2 and HONO. 2-8Nitric acid is a strong acid, but it requires a cluster of at least four water molecules to dissociate in the gas phase. [9][10][11] In bulk aqueous solutions and on ice, nitric acid can form hydrates with 1, 2 or 3 water molecules, depending on the concentration. 12-24 Such hydrates, as well as the HNO 3 dimer, have also been seen on solid surfaces during the hydrolysis of NO 2 at

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“…1). 48 The interior walls of the cell were coated with halocarbon wax (Halocarbon Products Corporation, River Edge, NJ). The cell had inlet and outlet ports on the sides to flow desired concentrations of gases over the crystal at a total flow rate of 70 cm 3 min…”

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Thermal and photochemical reactions of NO2 on chromium(iii) oxide surfaces at atmospheric pressure

Nishino

Finlayson-Pitts

2012

Phys. Chem. Chem. Phys.

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While many studies of heterogeneous chemistry on Cr 2 O 3 surfaces have focused on its catalytic activity, less is known about chemistry on this surface under atmospheric conditions. We report here studies of the thermal and photochemical reactions of NO 2 on Cr 2 O 3 at one atm in air. In order to follow surface species, the interaction of 16-120 ppm NO 2 with a 15 nm Cr 2 O 3 thin film deposited on a germanium crystal was monitored in a flow system using attenuated total reflectance (ATR) coupled to a Fourier transform infrared (FTIR) spectrometer. Gas phase products were monitored in the effluent of an B285 ppm NO 2 -air mixture that had passed over Cr 2 O 3 powder in a flow system. A chemiluminescence NO y analyzer, a photometric O 3 analyzer and a long-path FTIR spectrometer were used to probe the gaseous products. In the absence of added water vapor, NO 2 formed nitrate (NO 3 À ) ions coordinated to Cr 3+ . These surface coordinated NO 3 À were reversibly solvated by water under humid conditions. In both dry and humid cases, nitrate ions decreased during irradiation of the surface at 302 nm, and NO and NO 2 were generated in the gas phase. Under dry conditions, NO was the major gaseous product while NO 2 was the dominant species in the presence of water vapor. Heating of the surface after exposure to NO 2 led to the generation of both NO 2 and NO under dry conditions, but only NO 2 in the presence of water vapor. Elemental chromium incorporated into metal alloys such as stainless steel is readily oxidized in contact with ambient air, forming a chromium-rich metal oxide surface layer. The results of these studies suggest that active photo-and thermal chemistry will occur when boundary layer materials containing chromium(III) or chromium oxide such as stainless steel, roofs, automobile bumpers etc. are exposed to NO 2 under tropospheric conditions.

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Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Cited by 28 publications

References 78 publications

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Thermal and photochemical reactions of NO2 on chromium(iii) oxide surfaces at atmospheric pressure

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Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Cited by 28 publications

References 78 publications

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Thermal and photochemical reactions of NO2 on chromium(iii) oxide surfaces at atmospheric pressure

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Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O₃, NO₃, and OH, on organic surfaces