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Schatz GC, Wodtke AM, Yang X. Spiers Memorial Lecture: New directions in molecular scattering. Faraday Discuss 2024; 251:9-62. [PMID: 38764350 DOI: 10.1039/d4fd00015c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2024]
Abstract
The field of molecular scattering is reviewed as it pertains to gas-gas as well as gas-surface chemical reaction dynamics. We emphasize the importance of collaboration of experiment and theory, from which new directions of research are being pursued on increasingly complex problems. We review both experimental and theoretical advances that provide the modern toolbox available to molecular-scattering studies. We distinguish between two classes of work. The first involves simple systems and uses experiment to validate theory so that from the validated theory, one may learn far more than could ever be measured in the laboratory. The second class involves problems of great complexity that would be difficult or impossible to understand without a partnership of experiment and theory. Key topics covered in this review include crossed-beams reactive scattering and scattering at extremely low energies, where quantum effects dominate. They also include scattering from surfaces, reactive scattering and kinetics at surfaces, and scattering work done at liquid surfaces. The review closes with thoughts on future promising directions of research.
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Affiliation(s)
- George C Schatz
- Dept of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Alec M Wodtke
- Institute for Physical Chemistry, Georg August University, Goettingen, Germany
- Max Planck Institute for Multidisciplinary Natural Sciences, Goettingen, Germany.
- International Center for the Advanced Studies of Energy Conversion, Georg August University, Goettingen, Germany
| | - Xueming Yang
- Dalian Institute for Chemical Physics, Chinese Academy of Sciences, Dalian, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen, China
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2
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Gao XF, Hood DJ, Zhao X, Nathanson GM. Creation and Reaction of Solvated Electrons at and near the Surface of Water. J Am Chem Soc 2023; 145:10987-10990. [PMID: 37191478 DOI: 10.1021/jacs.3c03370] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Solvated electrons (es-) are among nature's most powerful reactants, with over 2600 reactions investigated in bulk water. These electrons can also be created at and near the surface of water by exposing an aqueous microjet in vacuum to gas-phase sodium atoms, which ionize into es- and Na+ within the top few layers. When a reactive surfactant is added to the jet, the surfactant and es- become coreactants localized in the interfacial region. We report the reaction of es- with the surfactant benzyltrimethylammonium in a 6.7 M LiBr/water microjet at 235 K and pH = 2. The reaction intermediates trimethylamine (TMA) and benzyl radical are identified by mass spectrometry after they evaporate from solution into the gas phase. Their detection demonstrates that TMA can escape before it is protonated and benzyl before it combines with itself or a H atom. Diffusion-reaction calculations indicate that es- reacts on average within 20 Å of the surface and perhaps within the surfactant monolayer itself, while unprotonated TMA evaporates from the top 40 Å. The escape depth exceeds 1300 Å for the more slowly reacting benzyl radical. These proof-of-principle experiments establish an approach for exploring the near-interfacial analogues of aqueous bulk-phase radical chemistry through the evaporation of reaction intermediates into the gas phase.
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Affiliation(s)
- Xiao-Fei Gao
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - David J Hood
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Xianyuan Zhao
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Gilbert M Nathanson
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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3
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Gao XF, Nathanson GM. Exploring Gas-Liquid Reactions with Microjets: Lessons We Are Learning. Acc Chem Res 2022; 55:3294-3302. [PMID: 36378763 DOI: 10.1021/acs.accounts.2c00602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Liquid water is all around us: at the beach, in a cloud, from a faucet, inside a spray tower, covering our lungs. It is fascinating to imagine what happens to a reactive gas molecule as it approaches the surface of water in these examples. Some incoming molecules may first be deflected away after colliding with an evaporating water molecule. Those that do strike surface H2O or other surface species may bounce directly off or become momentarily trapped through hydrogen bonding or other attractive forces. The adsorbed gas molecule can then desorb immediately or instead dissolve, passing through the interfacial region and into the bulk, perhaps diffusing back to the surface and evaporating before reacting. Alternatively, it may react with solute or water molecules in the interfacial or bulk regions, and a reaction intermediate or the final product may then desorb into the gas phase. Building a "blow by blow" picture of these pathways is challenging for vacuum-based techniques because of the high vapor pressure of water. In particular, collisions within the thick vapor cloud created by evaporating molecules just above the surface scramble the trajectories and internal states of the gaseous target molecules, hindering construction of gas-liquid reaction mechanisms at the atomic scale that we strive to map out.The introduction of the microjet in 1988 by Faubel, Schlemmer, and Toennies opened up entirely new possibilities. Their inspired solution seems so simple: narrow the end of a glass tube to a diameter smaller than the mean free path of the vapor molecules and then push the liquid through the tube at speeds of a car on a highway. The narrow liquid stream creates a sparse vapor cloud, with water molecules spaced far enough apart that they and the reactant gases interact, at most, weakly. Experimentalists, however, confront a host of challenges: nozzle clogging, unstable jetting, searching for vacuum-compatible solutions, measuring low signal levels, and teasing out artifacts because the slender jet is the smallest surface in the vacuum chamber. In this Account, we describe lessons that we are learning as we explore gases (DCl, (HCOOH)2, N2O5) reacting with water molecules and solute ions in the near-interfacial region of these fast-flowing aqueous microjets.
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Affiliation(s)
- Xiao-Fei Gao
- Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Gilbert M Nathanson
- Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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4
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Lu W, Mackie CJ, Xu B, Head-Gordon M, Ahmed M. A Computational and Experimental View of Hydrogen Bonding in Glycerol Water Clusters. J Phys Chem A 2022; 126:1701-1710. [PMID: 35254809 DOI: 10.1021/acs.jpca.2c00659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Polyol-water clusters provide a template to probe ionization and solvation processes of paramount interest in atmospheric and interstellar chemistry. We generate glycerol water clusters in a continuous supersonic jet expansion and interrogate the neutral species with synchrotron-based tunable vacuum ultraviolet photoionization mass spectrometry. A series of glycerol fragments (m/z 44, 61, 62, and 74) clustered with water are observed. A judicious combination of backing pressure, nozzle temperature, and water vapor pressure allows for tuning the mol % of glycerol. The recorded appearance energies of the water cluster series m/z 62 and 74 are similar to that observed in pure glycerol, while the m/z 61 series shows a dependence on cluster composition. Furthermore, this series also tracks the water concentration of the beam. Theoretical calculations on neutral and ionized clusters visualize the hydrogen bond network in these water clusters and provide an assessment of the number of glycerol-glycerol, glycerol-water, and water-water hydrogen bonds in the cluster, as well as their interaction energies. This method of bond counting and interaction energy assessment explains the changes in the mass spectrum as a function of mol % and offers a glimpse of the disruption of the hydrogen bond network in glycerol-water clusters. The calculations also reveal interesting barrierless chemical processes in photoionized glycerol water clusters that are either activated or do not occur without the presence of water. Examples include spontaneous intramolecular proton transfer within glycerol to form a distonic ion, nonactivated breaking of a C-C bond, and spontaneous proton transfer from glycerol to water. These results appear relevant to radiation-induced chemical processing of alcohol-water ices in the interstellar medium.
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Affiliation(s)
- Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Cameron J Mackie
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Bo Xu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Martin Head-Gordon
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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5
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Li D, Zhao Q, Ren Q, Song Z, Zhang Q, Long M, Li H. Double activating peroxymonosulfate with g-C 3N 4/Fe 2(MoO 4) 3 to enhance photocatalytic activity under visible light irradiation. NEW J CHEM 2021. [DOI: 10.1039/d1nj02915k] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The peroxymonosulfate was double activated by photogenerated e−/h+ and Fe(iii).
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Affiliation(s)
- Di Li
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Qianqian Zhao
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Qiaoxia Ren
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Ziyue Song
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Qiuli Zhang
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Mingyang Long
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
| | - Hongmiao Li
- School of Chemistry and Chemical Engineering, Xi’an University of Architecture and Technology, Xi’an, 710055, China
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6
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Xu C, Treadway CM, Murray VJ, Minton TK, Malaska MJ, Cable ML, Hofmann AE. Inelastic scattering dynamics of naphthalene and 2-octanone on highly oriented pyrolytic graphite. J Chem Phys 2020; 152:244709. [PMID: 32610992 DOI: 10.1063/5.0011958] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The inelastic scattering dynamics of the isobaric molecules, naphthalene (C10H8) and 2-octanone (C8H16O), on highly oriented pyrolytic graphite (HOPG) have been investigated as part of a broader effort to inform the inlet design of a mass spectrometer for the analysis of atmospheric gases during a flyby mission through the atmosphere of a planet or moon. Molecular beam-surface scattering experiments were conducted, and the scattered products were detected with the use of a rotatable mass spectrometer detector. Continuous, supersonic beams were prepared, with average incident translational energies, ⟨Ei⟩, of 247.3 kJ mol-1 and 538.2 kJ mol-1 for naphthalene and 268.6 kJ mol-1 and 433.8 kJ mol-1 for 2-octanone. These beams were directed toward an HOPG surface, held at 530 K, at incident angles, θi, of 30°, 45°, and 70°, and scattered products were detected as functions of their translational energies and scattering angles. The scattering dynamics of both molecules are very similar and mimic the scattering of atoms and small molecules on rough surfaces, where parallel momentum is not conserved, suggesting that the dynamics are dominated by a corrugated interaction potential between the incident molecule and the surface. The effective corrugation of the molecule-surface interaction is apparently caused by the structure of the incident molecule and the consequent myriad available energy transfer pathways between the molecule and the surface during a complex collision event. In addition, the HOPG surface contributes to the corrugation of the interaction potential because it can absorb significant energy from collisions with incident molecules that have high mass and incident energy. Small differences in the scattering dynamics of the two molecules are inferred to arise from the details of the molecule-surface interaction potential, with 2-octanone exhibiting dynamics that suggest a slightly stronger interaction with the surface than naphthalene. These results add to a growing body of work on the scattering dynamics of organic molecules on HOPG, from which insight into the hypervelocity sampling and analysis of such molecules may be obtained.
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Affiliation(s)
- Chenbiao Xu
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Cal M Treadway
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Vanessa J Murray
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Timothy K Minton
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Michael J Malaska
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109, USA
| | - Morgan L Cable
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109, USA
| | - Amy E Hofmann
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109, USA
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7
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Wiens JP, Alexander WA. Sodium atom beam collisions with the liquid glycerol surface: Mass effects of deuteration. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.06.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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8
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Wang Y, Guo H, Zheng Q, Saidi WA, Zhao J. Tuning Solvated Electrons by Polar-Nonpolar Oxide Heterostructure. J Phys Chem Lett 2018; 9:3049-3056. [PMID: 29767527 DOI: 10.1021/acs.jpclett.8b00938] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Solvated electron states at the oxide/aqueous interface represent the lowest energy charge-transfer pathways, thereby playing an important role in photocatalysis and electronic device applications. However, their energies are usually higher than the conduction band minimum (CBM), which makes the solvated electrons difficult to utilize in charge-transfer processes. Thus it is essential to stabilize the energy of the solvated electron states. Taking LaAlO3/SrTiO3 (LAO/STO) oxide heterostructure with H2O-adsorbed monolayer as a prototypical system, we show using DFT and ab initio time-dependent nonadiabatic molecular dynamics simulation that the energy and dynamics of solvated electrons can be tuned by the electric field in the polar-nonpolar oxide heterostructure. In particular, for LAO/STO with p-type interface, the CBM is contributed by the solvated electron state when LAO is thicker than four unit cells. Furthermore, the solvated electron band minimum can be partially occupied when LAO is thicker than eight unit cells. We propose that the tunability of solvated electron states can be achieved on polar-nonpolar oxide heterostructure surfaces as well as on ferroelectric oxides, which is important for charge and proton transfer at oxide/aqueous interfaces.
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Affiliation(s)
- Yanan Wang
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Hongli Guo
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- School of Physics and Technology, Center for Nanoscience and Nanotechnology, and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education , Wuhan University , Wuhan 430072 , China
| | - Qijing Zheng
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Wissam A Saidi
- Department of Mechanical Engineering and Materials Science , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
| | - Jin Zhao
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
- Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
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9
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Tesa-Serrate MA, Smoll EJ, Minton TK, McKendrick KG. Atomic and Molecular Collisions at Liquid Surfaces. Annu Rev Phys Chem 2016; 67:515-40. [PMID: 27090845 DOI: 10.1146/annurev-physchem-040215-112355] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The gas-liquid interface remains one of the least explored, but nevertheless most practically important, environments in which molecular collisions take place. These molecular-level processes underlie many bulk phenomena of fundamental and applied interest, spanning evaporation, respiration, multiphase catalysis, and atmospheric chemistry. We review here the research that has, during the past decade or so, been unraveling the molecular-level mechanisms of inelastic and reactive collisions at the gas-liquid interface. Armed with the knowledge that such collisions with the outer layers of the interfacial region can be unambiguously distinguished, we show that the scattering of gas-phase projectiles is a promising new tool for the interrogation of liquid surfaces with extreme surface sensitivity. Especially for reactive scattering, this method also offers absolute chemical selectivity for the groups that react to produce a specific observed product.
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Affiliation(s)
- Maria A Tesa-Serrate
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom;
| | - Eric J Smoll
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717;
| | - Timothy K Minton
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717;
| | - Kenneth G McKendrick
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom;
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10
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Pronschinske A, Pedevilla P, Coughlin B, Murphy CJ, Lucci FR, Payne MA, Gellman AJ, Michaelides A, Sykes ECH. Atomic-Scale Picture of the Composition, Decay, and Oxidation of Two-Dimensional Radioactive Films. ACS NANO 2016; 10:2152-2158. [PMID: 26735687 DOI: 10.1021/acsnano.5b06640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Two-dimensional radioactive (125)I monolayers are a recent development that combines the fields of radiochemistry and nanoscience. These Au-supported monolayers show great promise for understanding the local interaction of radiation with 2D molecular layers, offer different directions for surface patterning, and enhance the emission of chemically and biologically relevant low-energy electrons. However, the elemental composition of these monolayers is in constant flux due to the nuclear transmutation of (125)I to (125)Te, and their precise composition and stability under ambient conditions has yet to be elucidated. Unlike I, which is stable and unreactive when bound to Au, the newly formed Te atoms would be expected to be more reactive. We have used electron emission and X-ray photoelectron spectroscopy (XPS) to quantify the emitted electron energies and to track the film composition in vacuum and the effect of exposure to ambient conditions. Our results reveal that the Auger electrons emitted during the ultrafast radioactive decay process have a kinetic energy corresponding to neutral Te. By combining XPS and scanning tunneling microscopy experiments with density functional theory, we are able to identify the reaction of newly formed Te to TeO2 and its subsequent dimerization. The fact that the Te2O4 units stay intact during major lateral rearrangement of the monolayer illustrates their stability. These results provide an atomic-scale picture of the composition and mobility of surface species in a radioactive monolayer as well as an understanding of the stability of the films under ambient conditions, which is a critical aspect in their future applications.
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Affiliation(s)
- Alex Pronschinske
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Philipp Pedevilla
- Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London , London WC1E 6BT, United Kingdom
| | - Benjamin Coughlin
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Colin J Murphy
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Felicia R Lucci
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Matthew A Payne
- Department of Chemical Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Andrew J Gellman
- Department of Chemical Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Angelos Michaelides
- Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London , London WC1E 6BT, United Kingdom
| | - E Charles H Sykes
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
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11
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Faust JA, Nathanson GM. Microjets and coated wheels: versatile tools for exploring collisions and reactions at gas–liquid interfaces. Chem Soc Rev 2016; 45:3609-20. [DOI: 10.1039/c6cs00079g] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Scattering experiments using liquid microjets provide a window into collisions and reactions at the surfaces of high vapor pressure liquids.
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12
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Pronschinske A, Pedevilla P, Murphy CJ, Lewis EA, Lucci FR, Brown G, Pappas G, Michaelides A, Sykes ECH. Enhancement of low-energy electron emission in 2D radioactive films. NATURE MATERIALS 2015; 14:904-907. [PMID: 26076306 DOI: 10.1038/nmat4323] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 05/07/2015] [Indexed: 06/04/2023]
Abstract
High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope (125)I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual (125)I atoms into (125)Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic (125)I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies.
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Affiliation(s)
- Alex Pronschinske
- Department of Chemistry, Tufts University, 62 Talbot Avenue Medford, Massachusetts 02155, USA
| | - Philipp Pedevilla
- Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1E 6BT, UK
| | - Colin J Murphy
- Department of Chemistry, Tufts University, 62 Talbot Avenue Medford, Massachusetts 02155, USA
| | - Emily A Lewis
- Department of Chemistry, Tufts University, 62 Talbot Avenue Medford, Massachusetts 02155, USA
| | - Felicia R Lucci
- Department of Chemistry, Tufts University, 62 Talbot Avenue Medford, Massachusetts 02155, USA
| | - Garth Brown
- PerkinElmer, Inc., 331 Treble Cove Road North Billerica, Massachusetts 01862, USA
| | - George Pappas
- PerkinElmer, Inc., 331 Treble Cove Road North Billerica, Massachusetts 01862, USA
| | - Angelos Michaelides
- Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1E 6BT, UK
| | - E Charles H Sykes
- Department of Chemistry, Tufts University, 62 Talbot Avenue Medford, Massachusetts 02155, USA
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13
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The solvation of electrons by an atmospheric-pressure plasma. Nat Commun 2015; 6:7248. [PMID: 26088017 PMCID: PMC4557361 DOI: 10.1038/ncomms8248] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/20/2015] [Indexed: 11/25/2022] Open
Abstract
Solvated electrons are typically generated by radiolysis or photoionization of solutes. While plasmas containing free electrons have been brought into contact with liquids in studies dating back centuries, there has been little evidence that electrons are solvated by this approach. Here we report direct measurements of solvated electrons generated by an atmospheric-pressure plasma in contact with the surface of an aqueous solution. The electrons are measured by their optical absorbance using a total internal reflection geometry. The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer. We estimate an average penetration depth of 2.5±1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination. Reactions with various electron scavengers including H+, NO2−, NO3− and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis. Free, or solvated, electrons in a solution are known to form at the interface between a liquid and a gas. Here, the authors use absorption spectroscopy in a total internal reflection geometry to probe solvated electrons generated at a plasma in contact with the surface of an aqueous solution
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14
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Bessire BK, Lahankar SA, Minton TK. Pyrolysis of phenolic impregnated carbon ablator (PICA). ACS APPLIED MATERIALS & INTERFACES 2015; 7:1383-1395. [PMID: 25490209 DOI: 10.1021/am507816f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Molar yields of the pyrolysis products of thermal protection systems (TPSs) are needed in order to improve high fidelity material response models. The volatile chemical species evolved during the pyrolysis of a TPS composite, phenolic impregnated carbon ablator (PICA), have been probed in situ by mass spectrometry in the temperature range 100 to 935 °C. The relative molar yields of the desorbing species as a function of temperature were derived by fitting the mass spectra, and the observed trends are interpreted in light of the results of earlier mechanistic studies on the pyrolysis of phenolic resins. The temperature-dependent product evolution was consistent with earlier descriptions of three stages of pyrolysis, with each stage corresponding to a temperature range. The two main products observed were H2O and CO, with their maximum yields occurring at ∼350 °C and ∼450 °C, respectively. Other significant products were CH4, CO2, and phenol and its methylated derivatives; these products tended to desorb concurrently with H2O and CO, over the range from about 200 to 600 °C. H2 is presumed to be the main product, especially at the highest pyrolysis temperatures used, but the relative molar yield of H2 was not quantified. The observation of a much higher yield of CO than CH4 suggests the presence of significant hydroxyl group substitution on phenol prior to the synthesis of the phenolic resin used in PICA. The detection of CH4 in combination with the methylated derivatives of phenol suggests that the phenol also has some degree of methyl substitution. The methodology developed is suitable for real-time measurements of PICA pyrolysis and should lend itself well to the validation of nonequilibrium models whose aim is to simulate the response of TPS materials during atmospheric entry of spacecraft.
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Affiliation(s)
- Brody K Bessire
- Department of Chemistry and Biochemistry, 103 Chemistry and Biochemistry Building, Montana State University , Bozeman, Montana 59717, United States
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15
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Zurheide F, Dierking CW, Pradzynski CC, Forck RM, Flüggen F, Buck U, Zeuch T. Size-Resolved Infrared Spectroscopic Study of Structural Transitions in Sodium-Doped (H2O)n Clusters Containing 10–100 Water Molecules. J Phys Chem A 2014; 119:2709-20. [DOI: 10.1021/jp509883m] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Florian Zurheide
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Christoph W. Dierking
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Christoph C. Pradzynski
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Richard M. Forck
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Florian Flüggen
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Udo Buck
- Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Thomas Zeuch
- Institut für Physikalische Chemie, Tammannstaße
6, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
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16
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Wiens JP, Nathanson GM, Alexander WA, Minton TK, Lakshmi S, Schatz GC. Collisions of Sodium Atoms with Liquid Glycerol: Insights into Solvation and Ionization. J Am Chem Soc 2014; 136:3065-74. [DOI: 10.1021/ja4106144] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Justin P. Wiens
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Gilbert M. Nathanson
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - William A. Alexander
- Department of Chemistry, The University of Memphis, Memphis, Tennessee 38152, United States
| | - Timothy K. Minton
- Department of Chemistry and
Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Sankaran Lakshmi
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - George C. Schatz
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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17
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Signorell R, Yoder BL, West AHC, Ferreiro JJ, Saak CM. Angle-resolved valence shell photoelectron spectroscopy of neutral nanosized molecular aggregates. Chem Sci 2014. [DOI: 10.1039/c3sc53423e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Angle-resolved photoelectron spectroscopy opens a new avenue to probe the orbital character of solutes and solvents from the nanoscale to the bulk.
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Affiliation(s)
- Ruth Signorell
- ETH Zürich
- Laboratory of Physical Chemistry
- Zürich, Switzerland
| | - Bruce L. Yoder
- ETH Zürich
- Laboratory of Physical Chemistry
- Zürich, Switzerland
| | - Adam H. C. West
- ETH Zürich
- Laboratory of Physical Chemistry
- Zürich, Switzerland
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18
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Alexander WA, Zhang J, Murray VJ, Nathanson GM, Minton TK. Kinematics and dynamics of atomic-beam scattering on liquid and self-assembled monolayer surfaces. Faraday Discuss 2013; 157:355-74; discussion 375-98. [PMID: 23230778 DOI: 10.1039/c2fd20034a] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have conducted investigations of the energy transfer dynamics of atomic oxygen and argon scattering from hydrocarbon and fluorocarbon surfaces. In light of these results, we appraise the applicability and value of a kinematic scattering model, which views a gas-surface interaction as a gas-phase-like collision between an incident atom or molecule and a localized region of the surface with an effective mass. We have applied this model to interpret the effective surface mass and energy transfer when atoms strike two different surfaces under identical bombardment conditions. To this end, we have collected new data, and we have re-examined existing data sets from both molecular-beam experiments and molecular dynamics simulations. We seek to identify trends that could lead to a robust general understanding of energy transfer processes induced by collisions of gas-phase species with liquid and semi-solid surfaces.
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Affiliation(s)
- William A Alexander
- Department of Chemistry and Biochemistry, Montana State University, 103 Chem/Biochem Bldg., Bozeman, MT 59717, USA
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19
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Affiliation(s)
- Bernd Abel
- Leibniz Institute of Surface Modification (IOM), Chemical Department, D-04318 Leipzig, Germany, and Wilhelm-Ostwald Institute for Physical and Theoretical Chemistry, D-04103 Leipzig, Germany;
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20
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Pradzynski CC, Forck RM, Zeuch T, Slavicek P, Buck U. A Fully Size-Resolved Perspective on the Crystallization of Water Clusters. Science 2012; 337:1529-32. [DOI: 10.1126/science.1225468] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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