[ { "id": "authors:t36sw-dgd16", "collection": "authors", "collection_id": "t36sw-dgd16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190104-155625897", "type": "article", "title": "The chemical reactions in electrosprays of water do not always correspond to those at the pristine air\u2013water interface", "author": [ { "family_name": "Gallo", "given_name": "Adair, Jr.", "orcid": "0000-0001-5015-8111", "clpid": "Gallo-Adair-Jr" }, { "family_name": "Farinha", "given_name": "Andreia S. F.", "clpid": "Farinha-Andreia-S-F" }, { "family_name": "Dinis", "given_name": "Miguel", "clpid": "Dinis-Miguel" }, { "family_name": "Emwas", "given_name": "Abdul-Hamid", "clpid": "Emwas-Abdul-Hamid" }, { "family_name": "Santana", "given_name": "Adriano", "clpid": "Santana-Adriano" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-Robert-J" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Mishra", "given_name": "Himanshu", "orcid": "0000-0001-8759-7812", "clpid": "Mishra-Himanshu" } ], "abstract": "The recent application of electrosprays to characterize the air\u2013water interface, along with the reports on dramatically accelerated chemical reactions in aqueous electrosprays, have sparked a broad interest. Herein, we report on complementary laboratory and in silico experiments tracking the oligomerization of isoprene, an important biogenic gas, in electrosprays and isoprene\u2013water emulsions to differentiate the contributions of interfacial effects from those of high voltages leading to charge-separation and concentration of reactants in the electrosprays. To this end, we employed electrospray ionization mass spectrometry, proton nuclear magnetic resonance, ab initio calculations and molecular dynamics simulations. We found that the oligomerization of isoprene in aqueous electrosprays involved minimally hydrated and highly reactive hydronium ions. Those conditions, however, are non-existent at pristine air\u2013water interfaces and oil\u2013water emulsions under normal temperature and pressure. Thus, electrosprays should be complemented with surface-specific platforms and theoretical methods to reliably investigate chemistries at the pristine air\u2013water interface.", "doi": "10.1039/c8sc05538f", "pmcid": "PMC6422012", "issn": "2041-6520", "publisher": "Royal Society of Chemistry", "publication": "Chemical Science", "publication_date": "2019-03-07", "series_number": "9", "volume": "10", "issue": "9", "pages": "2566-2577" }, { "id": "authors:vrfte-7xh66", "collection": "authors", "collection_id": "vrfte-7xh66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140203-095934074", "type": "article", "title": "Tropospheric aerosol as a reactive intermediate", "author": [ { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" }, { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Yabushita", "given_name": "Akihiro", "clpid": "Yabushita-Akihiro" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Liu", "given_name": "Wei-Guang", "orcid": "0000-0002-6633-7795", "clpid": "Liu-Wei-Guang" }, { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "abstract": "In tropospheric chemistry, secondary organic aerosol (SOA) is deemed an end product. Here, on the basis of new evidence, we make the case that SOA is a key reactive intermediate. We present laboratory results on the catalysis by carboxylate anions of the disproportionation of NO_2 'on water': 2NO_2 + H_2O = HONO + NO_3^\u2212 + H^+ (R1), and supporting quantum chemical calculations, which we apply to reinterpret recent reports on (i) HONO daytime source strengths vis-\u00e0-vis SOA anion loadings and (ii) the weak seasonal and latitudinal dependences of NO_x decay kinetics over several megacities. HONO daytime generation via R1 should track sunlight because it is generally catalyzed by the anions produced during the photochemical oxidation of pervasive gaseous pollutants. Furthermore, by proceeding on the everpresent substrate of aquated airborne particulates, R1 can eventually overtake the photolysis of NO_2: NO_2 + h\u03bd = NO + O(^3P) (R2), at large zenith angles. Thus, since R1 leads directly to \u02d9OH-radical generation via HONO photolysis: HONO + h\u03bd = NO + \u02d9OH, whereas the path initiated by R2 is more circuitous and actually controlled by the slower photolysis of O_3: O_3 + h\u03bd (+H_2O) = O_2 + 2\u02d9OH, the competition between R1 and R2 provides a mechanistic switch that buffers \u02d9OH concentrations and NO_2 decay (via R1 and/or NO_2^+ \u02d9OH = HNO_3) from actinic flux variations.", "doi": "10.1039/C3FD00040K", "issn": "1359-6640", "publisher": "Royal Society of Chemistry", "publication": "Faraday Discussions", "publication_date": "2013-04-08", "volume": "165", "pages": "407-420" }, { "id": "authors:bmzfq-tec61", "collection": "authors", "collection_id": "bmzfq-tec61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130729-103126540", "type": "conference_item", "title": "First principles based theory complemented with electrospray ionization mass spectrometry to address environmental abiotic and biotic reactions", "author": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Colussi", "given_name": "A. J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" }, { "family_name": "Pascal", "given_name": "Tod A.", "orcid": "0000-0003-2096-1143", "clpid": "Pascal-T-A" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-R-J" } ], "abstract": "We will summarize recent advances in First-principles based methods for predicting interfacial entropy and free energy with\napplications to reactions at surfaces of water contg. various electrolytes. At Caltech, we have recently adapted an electrospray\nionization mass spectrometer to selectively probe physicochem. phenomena on liq. surfaces. Thus, together with theory and\nexpts. we have demonstrated that (1) anions present at air-water interface can electrostatically preorganize surrounding water\nmols. to facilitate proton transfer events, (2) the neg. charge of the air-water interface is due to the presence of excess OH- at\nthe aerial interface with a point-of-zero-charge at pH \u223c 3, and (3) rate enhancements obsd. in the proton catalyzed reactions at\nfluctuating aq. interfaces is due to inadequate hydration of hydronium, H_3O+. These findings should further our understanding\nof atm. chem., colloidal science, 'on-water' and enzymic catalysis and proton transfer reactions along and across membranes,\nincluding fuel cells and cellular processes.", "publisher": "Caltech Library", "publication_date": "2013-04" }, { "id": "authors:ydq07-bwx28", "collection": "authors", "collection_id": "ydq07-bwx28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130301-100027846", "type": "article", "title": "Quantum chemical insights into the dissociation of nitric acid on the surface of aqueous electrolytes", "author": [ { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-R-J" }, { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "abstract": "Recent experiments in our laboratory have shown that the probability of gaseous HNO_3 deprotonation on the surface of water is dramatically enhanced by anions. Herein, we report a quantum chemical study of how a HNO_3 molecule transfers its proton upon approaching water clusters containing or not a chloride ion. We find that HNO_3 always binds to the outermost water molecules both via donating and accepting hydrogen-bonds, but the free energy barrier for subsequent proton transfer into the clusters is greatly reduced in the presence of Cl^\u2212. As the dissociation of HNO_3 embedded in water clusters is barrierless, we infer that interfacial proton transfer to water is hindered by the cost of creating a cavity for NO_(3)^\u2212. Our findings suggest that nearby anions catalyze HNO_3 dissociation by preorganizing interfacial water and drawing the proton\u2014away from the incipient [H^(+)---NO_(3)^\u2212] close ion-pairs generated at the interface. This catalytic mechanism would operate in the 1 mM Cl^\u2212 range (1 Cl\u2212 in \u223c5.5 \u00d7 10^4 water molecules) covered by our experiments if weakly adsorbed HNO_3 were able to explore extended surface domains before desorbing or diffusing (undissociated) into bulk water.", "doi": "10.1002/qua.24151", "issn": "0020-7608", "publisher": "Wiley", "publication": "International Journal of Quantum Chemistry", "publication_date": "2013-02-15", "series_number": "4", "volume": "113", "issue": "4", "pages": "413-417" }, { "id": "authors:qx6d4-0mz65", "collection": "authors", "collection_id": "qx6d4-0mz65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130103-133136391", "type": "article", "title": "Br\u00f8nsted basicity of the air\u2013water interface", "author": [ { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-R-J" }, { "family_name": "Stewart", "given_name": "Logan A.", "clpid": "Stewart-L-A" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" } ], "abstract": "Differences in the extent of protonation of functional groups lying on either side of water\u2013hydrophobe interfaces are deemed essential to enzymatic catalysis, molecular recognition, bioenergetic transduction, and atmospheric aerosol\u2013gas exchanges. The sign and range of such differences, however, remain conjectural. Herein we report experiments showing that gaseous carboxylic acids RCOOH(g) begin to deprotonate on the surface of water significantly more acidic than that supporting the dissociation of dissolved acids RCOOH(aq). Thermodynamic analysis indicates that > 6 H_(2)O molecules must participate in the deprotonation of RCOOH(g) on water, but quantum mechanical calculations on a model air\u2013water interface predict that such event is hindered by a significant kinetic barrier unless OH\u2212 ions are present therein. Thus, by detecting RCOO\u2212 we demonstrate the presence of OH\u2212 on the aerial side of on pH > 2 water exposed to RCOOH(g). Furthermore, because in similar experiments the base (Me)_(3)N(g) is protonated only on pH < 4 water, we infer that the outer surface of water is Br\u00f8nsted neutral at pH \u223c3 (rather than at pH 7 as bulk water), a value that matches the isoelectric point of bubbles and oil droplets in independent electrophoretic experiments. The OH\u2212 densities sensed by RCOOH(g) on the aerial surface of water, however, are considerably smaller than those at the (>1 nm) deeper shear planes probed in electrophoresis, thereby implying the existence of OH\u2212 gradients in the interfacial region. This fact could account for the weak OH\u2212 signals detected by surface-specific spectroscopies.", "doi": "10.1073/pnas.1209307109", "pmcid": "PMC3503180", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2012-11-13", "series_number": "46", "volume": "109", "issue": "46", "pages": "18679-18683" }, { "id": "authors:ancx4-1wa85", "collection": "authors", "collection_id": "ancx4-1wa85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121009-104621400", "type": "article", "title": "Branched Polymeric Media: Boron-Chelating Resins from\n Hyperbranched Polyethylenimine", "author": [ { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Yu", "given_name": "Changjun", "clpid": "Yu-Changjun" }, { "family_name": "Chen", "given_name": "Dennis P.", "clpid": "Chen-Dennis-P" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Dalleska", "given_name": "Nathan F.", "orcid": "0000-0002-2059-1587", "clpid": "Dalleska-N-F" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Diallo", "given_name": "Mamadou S.", "orcid": "0000-0002-2571-1568", "clpid": "Diallo-M-S" } ], "abstract": "Extraction of boron from aqueous solutions using selective resins is important in a variety of applications including desalination, ultrapure water production, and nuclear power generation. Today's commercial boron-selective resins are exclusively prepared by functionalization of styrene-divinylbenzene (STY-DVB) beads with N-methylglucamine to produce resins with boron-chelating groups. However, such boron-selective resins have a limited binding capacity with a maximum free base content of 0.7 eq/L, which corresponds to a sorption capacity of 1.16 \u00b1 0.03 mMol/g in aqueous solutions with equilibrium boron concentration of ~70 mM. In this article, we describe the synthesis and characterization of a new resin that can selectively extract boron from aqueous solutions. We show that branched polyethylenimine (PEI) beads obtained from an inverse suspension process can be reacted with glucono-1,5-d-lactone to afford a resin consisting of spherical beads with high density of boron-chelating groups. This resin has a sorption capacity of 1.93 \u00b1 0.04 mMol/g in aqueous solution with equilibrium boron concentration of ~70 mM, which is 66% percent larger than that of standard commercial STY-DVB resins. Our new boron-selective resin also shows excellent regeneration efficiency using a standard acid wash with a 1.0 M HCl solution followed by neutralization with a 0.1 M NaOH solution.", "doi": "10.1021/es301518x", "issn": "0013-936X", "publisher": "American Chemical Society", "publication": "Environmental Science and Technology", "publication_date": "2012-08-21", "series_number": "16", "volume": "46", "issue": "16", "pages": "8998-9004" }, { "id": "authors:2nhgy-6jx30", "collection": "authors", "collection_id": "2nhgy-6jx30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120525-111436467", "type": "article", "title": "Anions dramatically enhance proton transfer through aqueous interfaces", "author": [ { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-R-J" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" } ], "abstract": "Proton transfer (PT) through and across aqueous interfaces is a fundamental process in chemistry and biology. Notwithstanding its importance, it is not generally realized that interfacial PT is quite different from conventional PT in bulk water. Here we show that, in contrast with the behavior of strong nitric acid in aqueous solution, gas-phase HNO_3 does not readily dissociate upon collision with the surface of water unless a few ions (>1 per 10^6 H2O) are present. By applying online electrospray ionization mass spectrometry we monitor in situ the surface of aqueous jets exposed to HNO3_(3(g)) beams and found that NO_3 \u2212 production increases dramatically on >30-\u03bcM inert electrolyte solutions. We also performed quantum mechanical calculations confirming that HNO3 dissociation\non the surface of small water clusters is hindered by a sizable barrier, which is drastically lowered in the presence of an anion. Anions electrostatically assist in drawing the proton away from NO_3 \u2212, which lingers outside the cluster because its incorporation\nis hampered by the energetic cost of opening a cavity therein.\nPresent results provide both direct experimental evidence and mechanistic\ninsights on the counterintuitive slowness of PT at water- hydrophobe boundaries and its remarkable sensitivity to electrostatic effects.", "doi": "10.1073/pnas.1200949109", "pmcid": "PMC3387034", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2012-06-26", "series_number": "26", "volume": "109", "issue": "26", "pages": "10228-10232" }, { "id": "authors:57124-05634", "collection": "authors", "collection_id": "57124-05634", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120716-073513495", "type": "article", "title": "Protonation and Oligomerization of Gaseous Isoprene on Mildly Acidic Surfaces: Implications for Atmospheric Chemistry", "author": [ { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" } ], "abstract": "In a global process linking the Earth's climate with its ecosystems, massive photosynthetic isoprene (ISOP) emissions are converted to light-scattering haze. This phenomenon is imperfectly captured by atmospheric chemistry models: predicted ISOP emissions atop forest canopies would deplete the oxidizing capacity of the overhead atmosphere, at variance with field observations. Here we address this key issue in novel laboratory experiments where we apply electrospray mass spectrometry to detect online the products of the reactive uptake of gaseous ISOP on the surface of aqueous jets as a function of acidity. We found that ISOP is already protonated to ISOPH\u02c6+ and undergoes cationic oligomerization to (ISOP)_2H\u02c6+ and (ISOP)_3H\u02c6+ on the surface of pH < 4 water jets. We estimate uptake coefficients, \u03b3ISOP = (0.5 \u2013 2.0) \u00d7 10\u02c6(\u20136) on pH = 3 water, which translate into the significant reuptake of leaf-level ISOP emissions in typical (surface-to-volume ~ 5 m\u02c6(\u20131)) forests during realistic (a few minutes) in-canopy residence times. Our findings may also account for the rapid decay of ISOP in forests after sunset and help bring the global budget of volatile organic compounds closer to balance.", "doi": "10.1021/jp2110133", "issn": "1089-5639", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry A", "publication_date": "2012-06-21", "series_number": "24", "volume": "116", "issue": "24", "pages": "6027-6032" }, { "id": "authors:qhqv1-m0393", "collection": "authors", "collection_id": "qhqv1-m0393", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130128-132834762", "type": "article", "title": "Hofmeister effects in micromolar electrolyte solutions", "author": [ { "family_name": "Enami", "given_name": "Shinichi", "orcid": "0000-0002-2790-7361", "clpid": "Enami-Shinichi" }, { "family_name": "Mishra", "given_name": "Himanshu", "clpid": "Mishra-Himanshu" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Colussi", "given_name": "Agust\u00edn J.", "orcid": "0000-0002-3400-4101", "clpid": "Colussi-A-J" } ], "abstract": "Ions induce both specific (Hofmeister) and non-specific (Coulomb) effects at aqueous interfaces. More than a century after their discovery, the origin of specific ion effects (SIE) still eludes explanation because the causal electrostatic and non-electrostatic interactions are neither local nor separable. Since direct Coulomb effects essentially vanish below \u223c10 \u03bcM (i.e., at >50 nm average ion separations in water), we decided to investigate whether SIE operate at, hitherto unexplored, lower concentrations. Herein, we report the detection of SIE above \u223c0.1 \u03bcM in experiments where relative iodide/bromide populations, \u03c7 = I^\u2212/Br^\u2212, were determined on the surface of aqueous (NaI + NaBr) jets by online electrospray mass spectrometry in the presence of variable XCl (X = H, Na, K, Cs, NH_4, and N(C_4H_9)_4) and NaY (Y = OH, Cl, NO_3, and ClO_4) concentrations. We found that (1) all tested electrolytes begin to affect \u03c7 below \u223c1 \u03bcM and (2) I^\u2212 and Br^\u2212 are preferentially suppressed by co-ions closely matching their interfacial affinities. We infer that these phenomena, by falling outside the reach of even the longest ranged electrostatic interactions, are dynamical in nature.", "doi": "10.1063/1.4704752", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "2012-04-21", "series_number": "15", "volume": "136", "issue": "15", "pages": "Art. No. 154707" } ]