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dc.contributor.advisorMishra, Himanshu
dc.contributor.authorGallo Junior, Adair
dc.date.accessioned2017-12-05T08:32:32Z
dc.date.available2018-12-04T00:00:00Z
dc.date.issued2017-12
dc.identifier.citationGallo Junior, A. (2017). An Investigation of Chemical Landscapes in Aqueous Electrosprays by Tracking Oligomerization of Isoprene. KAUST Research Repository. https://doi.org/10.25781/KAUST-0065C
dc.identifier.doi10.25781/KAUST-0065C
dc.identifier.urihttp://hdl.handle.net/10754/626292
dc.description.abstractElectrospray ionization mass spectrometry (ESIMS) is widely used to characterize neutral and ionic species in solvents. Typically, electrical, thermal, and pneumatic potentials are applied to create electrosprays from which charged ionic species are ejected for downstream analysis by mass spectrometry. Most recently, ESIMS has been exploited to investigate ambient proton transfer reactions at air-water interfaces in real time. We assessed the validity of these experiments via complementary laboratory experiments. Specifically, we characterized the products of two reaction scenarios via ESIMS and proton nuclear magnetic resonance (1H-NMR): (i) emulsions of pH-adjusted water and isoprene (C5H8) that were mechanically agitated, and (ii) electrosprays of pH-adjusted water that were collided with gas-phase isoprene. Our experiments unambiguously demonstrate that, while isoprene does not oligomerize in emulsions, it does undergo protonation and oligomerization in electrosprays, both with and without pH-adjusted water, confirming that C-C bonds form along myriad high-energy pathways during electrospray ionization. We also compared our experimental results with some quantum mechanics simulations of isoprene molecules interacting with hydronium at different hydration levels (gas versus liquid phase). In agreement with our experiments, the kinetic barriers to protonation and oligomerization of isoprene were inaccessible under ambient conditions. Rather, the gas-phase chemistries during electrospray ionization drove the oligomerization of isoprene. Therefore, we consider that ESIMS could induce artifacts in interfacial reactions. These findings warrant a reassessment of previous reports on tracking chemistries under ambient conditions at liquid-vapor interfaces via ESIMS. Further, we took some high-speed images of electrosprays where it was possible to observe the main characteristics of the phenomena, i.e. Taylor cone, charge separation, and Coulomb fission. Finally, we took the freedom to speculate on possible mechanisms that take place during electrospray ionization that affected our system and possibly may influence other common analytical techniques on ESIMS.
dc.language.isoen
dc.subjectelectrospray ionization
dc.subjectair-water interfaces
dc.subjectelectrospray droplets
dc.subjectisoprene oligomerization
dc.subjectreactions in electrospray
dc.subjectproton transfer reaction
dc.titleAn Investigation of Chemical Landscapes in Aqueous Electrosprays by Tracking Oligomerization of Isoprene
dc.typeThesis
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Division
dc.rights.embargodate2018-12-04
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberNunes, Suzana Pereira
dc.contributor.committeememberCavallo, Luigi
thesis.degree.disciplineEnvironmental Science and Engineering
thesis.degree.nameMaster of Science
dc.rights.accessrightsAt the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis became available to the public after the expiration of the embargo on 2018-12-04.
refterms.dateFOA2018-12-04T00:00:00Z


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