Dry Deposition of Biogenic Terpenes via Cationic Oligomerization on Environmental Aqueous Surfaces

Abstract

The products we observe are produced when the gaseous terpenes collide with the intact electroneutral aqueous jets as they emerge from the nozzle, i.e., before jets are broken up by the nebulizer gas. Since mass spectrometers detect net charge, the first step is the separation of pre-existing anions from cations in the electroneutral inflowing solutions. This is accomplished via the pneumatic breakup of the aqueous jet by a fast nebulizer gas that shears the outermost jet layers into droplets carrying net charges of either sign. These net charges are proportional to the concentrations of the protonated terpenes and their oligomers produced during gas-liquid collisions. Such droplets have a distribution of sizes and net charges 1,2 and, together, possess more surface and electrostatic energies than the original jet at the expense of the kinetic energy lost by the nebulizer gas. Since the nebulizer gas can fragment the jet but not

Fenton chemistry at aqueous interfaces

“…The species produced on the surface of such jets are analyzed in situ via online ES-MS. The present experimental setup essentially is the same as the one reported elsewhere (62,64,65). Solutions are pumped (100 μL·min −1 ) into the spraying chamber through a grounded stainless steel needle (100-μm bore) coaxial with a sheath-issuing nebulizer N 2 (g) at a high gas velocity v g (∼160 m/s).…”

“…We exploited the high sensitivity, surface selectivity, and unambiguous identification capabilities of a newly developed instrument based on online electrospray mass spectrometry (ES-MS) (58)(59)(60)(61)(62) to identify the primary products of reactions R1-R4 on aqueous FeCl 2 microjets exposed to gaseous H 2 O 2 and O 3 beams under ambient conditions [in N 2 (g) at 1 atm at 293 ± 2 K]. Our experiments are conducted by intersecting the continuously refreshed, uncontaminated surfaces of free-flowing aqueous microjets with reactive gas beams for τ ∼10-50 μs, immediately followed (within 100 μs; see below) by in situ detection of primary interfacial anionic products and intermediates via ES-MS (Methods, SI Text, and Figs.…”

“…S1 and S2). We have previously demonstrated that online mass spectrometric sampling of liquid microjets under ambient conditions is a surface-sensitive technique (58,(62)(63)(64)(65)(66)(67). Fig.…”

“…Everything happens as though the IF species involved in O-atom transfer are preferentially pushed to the surface of more concentrated Fe 2+ solutions. In this context, it is relevant to point out that we recently found that hydronium (H 3 O + ) emerges at the surface of water less than pH 4 as a "superacid" that protonates impinging gases having proton affinities larger than water (62,64,90). Thermodynamics dictates that this is possible only if interfacial H 3 O + is weakly hydrated.…”

Ion-Specific Long-Range Correlations on Interfacial Water Driven by Hydrogen Bond Fluctuations

“…[13][14][15][16][17][18][19] Data analysis based on mass balances and the kinetic theory of gases suggest that the thickness of the interfacial layers sampled in these experiments is less than a few nm, most likely below 1 nm. 9 More compellingly, we recently showed that the depth of the interfacial layers sampled in our experiments is controllable as a function of nebulizer gas velocity v g .…”