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Electrochirogenesis: The Possible Role of Low-Energy Spin-Polarized Electrons in Creating Homochirality. Symmetry (Basel) 2019. [DOI: 10.3390/sym11040528] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Electrochirogenesis deals with the induction of chirality by polarized electrons of which those with low energy (<15 eV) are seen to be the most effective. Possible sources of such electrons in the prebiotic universe are discussed and several examples where chiral induction by these electrons have been demonstrated are given. Finally, some possible scenarios where electrochirogenesis could have played a role in forming a chiral imbalance in a prebiotic setting have been speculated on and some possible future areas of research proposed.
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Amanatidis S, Yoder BL, Signorell R. Low-energy photoelectron transmission through aerosol overlayers. J Chem Phys 2017; 146:224204. [PMID: 29166077 PMCID: PMC5469680 DOI: 10.1063/1.4983995] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 05/08/2017] [Indexed: 11/14/2022] Open
Abstract
The transmission of low-energy (<1.8 eV) photoelectrons through the shell of core-shell aerosol particles is studied for liquid squalane, squalene, and di-ethyl-hexyl-sebacate shells. The photoelectrons are exclusively formed in the core of the particles by two-photon ionization. The total photoelectron yield recorded as a function of shell thicknesses (1-80 nm) shows a bi-exponential attenuation. For all substances, the damping parameter for shell thicknesses below 15 nm lies around 8 to 9 nm and is tentatively assigned to the electron attenuation length at electron kinetic energies of ≲1 eV. The significantly larger damping parameters for thick shells (>20 nm) are presumably a consequence of distorted core-shell structures. A first comparison of aerosol and traditional thin film overlayer methods is provided.
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Affiliation(s)
- Stavros Amanatidis
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Bruce L Yoder
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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Rosenberg RA. Spin-polarized electron induced asymmetric reactions in chiral molecules. Top Curr Chem (Cham) 2011; 298:279-306. [PMID: 21321806 DOI: 10.1007/128_2010_81] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Understanding the origin of chirality in nature has been an active area of research since the time of Pasteur. In this chapter we examine one possible route by which this asymmetry could have arisen, namely chiral-specific chemistry induced by spin-polarized electrons. The various sources of spin-polarized electrons (parity violation, photoemission, and secondary processes) are discussed. Experiments aimed at exploring these interactions are reviewed starting with those based on the Vester-Ulbricht hypothesis through recent studies of spin polarized secondary electrons from a magnetic substrate. We will conclude with a discussion of possible new avenues of research that could impact this area.
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Affiliation(s)
- Richard A Rosenberg
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
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Lu X, Zhi F, Shang H, Wang X, Xue Z. Investigation of the electrochemical behavior of multilayers film assembled porphyrin/gold nanoparticles on gold electrode. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2009.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Gandolfi C, Miyashita N, Kurth DG, Martinho PN, Morgan GG, Albrecht M. Organization of spin- and redox-labile metal centers into Langmuir and Langmuir–Blodgett films. Dalton Trans 2010; 39:4508-16. [DOI: 10.1039/b926023d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Sherratt PAJ, Cohen H, Seideman T. The information content of electron flow through adsorbed molecular monolayers. J Chem Phys 2009; 131:234701. [DOI: 10.1063/1.3273452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Garand E, Moula MG, Rowntree PA. Localization vs conduction: anionic excitations in alkanethiol self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:13850-13854. [PMID: 19360932 DOI: 10.1021/la803036v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Low-energy (6-11 eV) electron injection into Xe-coated self-assembled alkanethiol monolayers (SAMs) is reported. At most energies, the presence of the Xe film has negligible effect on the incident electrons, which penetrate the overlayer and induce significant C--H bond rupture at the terminal methyl sites and the subsurface methylene sites of the organic substrates. However, irradiation at 7.7 +/- 0.2 eV can lead to resonant electronic excitations of the Xe adsorbates to create transient anionic states in the Xe overlayer. Transfer of anionic excitations from the Xe overlayer to the SAM initially prepares excited anionic states at the terminal CH3 groups and leads to highly selective dissociations at the methyl sites, with negligible conduction along the alkane chain which would lead to subsurface C-H bond rupture at the methylene sites. These results demonstrate that the mobility of electronically excited charged states along the alkanethiol chains is significantly less than that of simple excess electrons and that highly site-selective chemical modifications can be induced by low-energy electrons in these highly homogeneous organic films.
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Affiliation(s)
- Etienne Garand
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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10
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Fradkin Z, Oron D, Naaman R. The effect of self-assembled monolayers on polarization-dependent two-photon photoemission and on the angular distribution of the photoelectrons. J Chem Phys 2007; 127:121102. [PMID: 17902886 DOI: 10.1063/1.2789413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of a self-assembled organized organic monolayer on the two-photon photoemission from semiconductor substrates was investigated. It has been found that the monolayer affects the relative yield of photoelectrons emitted by p-polarized versus s-polarized light. In addition, the monolayer affects the angular distribution of the ejected electrons. The effect on the photoelectron yield is attributed to the monolayer "smoothing" the electronic potential on the surface by eliminating surface states and dangling bonds. The effect on the angular distribution is attributed to a post-ejection interaction between the photoelectrons and the adsorbed molecules.
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Affiliation(s)
- Z Fradkin
- Department of Chemical Physics, Weizmann Institute, Rehovot 76100, Israel
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11
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Altman M, Shukla AD, Zubkov T, Evmenenko G, Dutta P, van der Boom ME. Controlling structure from the bottom-up: structural and optical properties of layer-by-layer assembled palladium coordination-based multilayers. J Am Chem Soc 2007; 128:7374-82. [PMID: 16734493 DOI: 10.1021/ja061026e] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Layer-by-layer assembly of two palladium coordination-based multilayers on silicon and glass substrates is presented. The new assemblies consist of rigid-rod chromophores connected by terminal pyridine moieties to palladium centers. Both colloidal palladium and PdCl2(PhCN)2 were used in order to determine the effect of the metal complex precursor on multilayer structure and optical properties. The multilayers were formed by an iterative wet-chemical deposition process at room temperature in air on a siloxane-based template layer. Twelve consecutive deposition steps have been demonstrated resulting in structurally regular assemblies with an equal amount of chromophore and palladium added in each molecular bilayer. The optical intensity characteristics of the metal-organic films are clearly a function of the palladium precursor employed. The colloid-based system has a UV-vis absorption maximum an order of magnitude stronger than that of the PdCl2-based multilayer. The absorption maximum of the PdCl2-based film exhibits a significant red shift of 23 nm with the addition of 12 layers. Remarkably, the structure and physiochemical properties of the submicron scale PdCl2-based structures are determined by the configuration of the approximately 15 angstroms thick template layer. The refractive index of the PdCl2-based film was determined by spectroscopic ellipsometry. Well-defined three-dimensional structures, with a dimension of 5 microm, were obtained using photopatterned template monolayers. The properties and microstructure of the films were studied by UV-vis spectroscopy, spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and aqueous contact angle measurements (CA).
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Affiliation(s)
- Marc Altman
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, 76100, Israel
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Weiss EA, Kriebel JK, Rampi MA, Whitesides GM. The study of charge transport through organic thin films: mechanism, tools and applications. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2007; 365:1509-37. [PMID: 17430810 DOI: 10.1098/rsta.2007.2029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
In this paper, we discuss the current state of organic and molecular-scale electronics, some experimental methods used to characterize charge transport through molecular junctions and some theoretical models (superexchange and barrier tunnelling models) used to explain experimental results. Junctions incorporating self-assembled monolayers of organic molecules - and, in particular, junctions with mercury-drop electrodes - are described in detail, as are the issues of irreproducibility associated with such junctions (due, in part, to defects at the metal-molecule interface).
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Affiliation(s)
- Emily A Weiss
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
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Fragouli D, Kitsopoulos TN, Chiodo L, Della Sala F, Cingolani R, Ray SG, Naaman R. Imaging photoelectron transmission through self-assembled monolayers: the work-function of alkanethiols coated gold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:6156-62. [PMID: 17441738 DOI: 10.1021/la063471t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
In this paper, we present a new approach for studying the electronic properties of self-assembled monolayers and their interaction with a conductive substrate, the low-energy photoelectron imaging spectroscopy (LEPIS). LEPIS relies on imaging of photoelectrons ejected from a conductive substrate and subsequently transmitted through organic monolayers. Using this method, we measure the relative work-function of alkanethiols of different length on gold substrate, and we are able to follow the changes occurring when the surface coverage is varied. We also computed the work-function of model alkanethiols using a plane-wave density functional theory approach, in order to demonstrate the correlation between changes in the work-function with the monolayer organization and density.
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Affiliation(s)
- Despina Fragouli
- Institute of Electronic Structure and Laser (FORTH) and Department of Chemistry, University of Crete, 71110 Heraklion-Crete, Greece
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Naaman R, Sanche L. Low-Energy Electron Transmission through Thin-Film Molecular and Biomolecular Solids. Chem Rev 2007; 107:1553-79. [PMID: 17439288 DOI: 10.1021/cr040200j] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R Naaman
- Department of Chemical Physics, Weizmann Institute, Rehovot, Israel 76100
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Monti OLA, Baker TA, Nesbitt DJ. Imaging nanostructures with scanning photoionization microscopy. J Chem Phys 2006; 125:154709. [PMID: 17059285 DOI: 10.1063/1.2354478] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We report detailed studies of local electronic properties in nanostructured thin metallic films using scanning photoionization microscopy. This novel form of microscopy combines the advantages of diffraction-limited optical excitation with the ability to detect both photons and low kinetic energy photoelectrons, permitting sensitive characterization of heterogeneous surfaces under vacuum conditions. Using this technique, correlated measurements of multiphoton photoemission cross section and optical penetration depth are reported for Au films supported on Pt. These results present a first step toward combining confocal fluorescence or Raman microscopy with time-resolved photoelectron imaging spectroscopy in complex metal film environments, which should be ideally suited to investigating local plasmonic effects in nanostructures.
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Affiliation(s)
- Oliver L A Monti
- JILA, National Institute of Standards and Technology, Boulder, Colorado 80303-0440, USA
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Neuman O, Naaman R. New Optical Absorption Band Resulting from the Organization of Self-Assembled Monolayers of Organic Thiols on Gold. J Phys Chem B 2006; 110:5163-5. [PMID: 16539440 DOI: 10.1021/jp060003j] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Experimental evidences are presented supporting the existence of a new optical absorption band observed when monolayers of alkylthiol are self-assembled on gold substrate. This new absorption is centered at about 800 nm and has a very broad absorption peak. The intensity of the new band correlates with the density of molecules and the quality of the organization of the monolayer.
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Ray SG, Daube SS, Leitus G, Vager Z, Naaman R. Chirality-induced spin-selective properties of self-assembled monolayers of DNA on gold. PHYSICAL REVIEW LETTERS 2006; 96:036101. [PMID: 16486734 DOI: 10.1103/physrevlett.96.036101] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2005] [Indexed: 05/06/2023]
Abstract
Here we show that self-assembled monolayers on gold of double-stranded DNA oligomers interact with polarized electrons similarly to a strong and oriented magnetic field. The direction of the field for right-handed DNA is away from the substrate. Moreover, the layer shows very high paramagnetic susceptibility. Interestingly, thiolated single-stranded DNA oligomers on gold do not show this effect. The new findings are rationalized based on recent results in which high paramagnetism was measured for diamagnetic films adsorbed on diamagnetic substrates.
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Affiliation(s)
- S G Ray
- Department of Chemical Physics, The Weizmann Institute, Rehovot 76100, Israel
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Naaman R, Vager Z. New electronic and magnetic properties emerging from adsorption of organized organic layers. Phys Chem Chem Phys 2006; 8:2217-24. [PMID: 16688303 DOI: 10.1039/b518103h] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New electronic and magnetic properties are induced by the adsorption of closed packed monolayers on solid substrates. For many thiolated molecules self-assembled on gold, a surprisingly large paramagnetism is observed. In the case where the layers are made from chiral molecules, in addition an unexpectedly large electronic dichroism is observed, which manifests itself as spin specific electron transmission. This dichroism was observed for monolayers made from polyalanine and from DNA. Self-assembled monolayers of double-stranded DNA oligomers on gold interact with polarized electrons similarly to a strong and oriented magnetic field. The direction of the field for right-handed DNA is away from the substrate. Moreover, the layer shows very high paramagnetic susceptibility. Interestingly, thiolated single-stranded DNA oligomers on gold do not show this effect. All the observations can be rationalized by assuming organization induced charge transfer between the substrate and the organic layer. The charge transfer results in spin alignment of the transferred electrons/holes. While for achiral molecules the spin alignment varies among the domains, in the case of monolayer made from chiral molecules the alignment is the same across the entire sample. When magnetic field is applied, large magnetic moment is observed that results from orbital magnetism.
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Affiliation(s)
- Ron Naaman
- Department of Chemical Physics, Weizmann Institute, Rehovot, Israel.
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Ray SG, Cohen H, Naaman R, Liu H, Waldeck DH. Organization-Induced Charge Redistribution in Self-Assembled Organic Monolayers on Gold. J Phys Chem B 2005; 109:14064-73. [PMID: 16852766 DOI: 10.1021/jp050398r] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The charge redistribution that occurs within dipolar molecules as they self-assemble into organized organic monolayer films has been studied. The extent of charge transfer is probed by work function measurements, using low-energy photoelectron spectroscopy (LEPS), contact potential difference (CPD), and X-ray photoelectron spectroscopy (XPS), with the latter providing fine details about the internal charge distribution along the molecule. In addition, two-photon photoelectron spectroscopy is applied to investigate the electronic structure of the adsorbed layers. We show that charge transfer acts to reduce the dipole-dipole interaction between the molecules but may either decrease or increase the molecule-to-surface dipole moment.
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Affiliation(s)
- S G Ray
- Department of Chemical Physics and Chemical Research Support, Weizmann Institute, Rehovot 76100, Israel
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Abstract
Many of the mutagenic or lethal effects of ionization radiation can be attributed to damage caused to the DNA by low-energy electrons. To gain insight on the parameters affecting this process, we measured the low-energy electron (<2 eV) transmission yield through self-assembled monolayers of short DNA oligomers. The electrons that are not transmitted are captured by the layer. Hence, the transmission reflects the capturing efficiency of the electrons by the layer. The dependence of the capturing probability on the base sequence was studied, as was the state of the captured electrons. It is found that the capturing probability scales with the number of G bases in the single-stranded oligomers and depends on their clustering level. Using two-photon photoelectron spectroscopy, we find that, once captured, the electrons do not reside on the bases. Rather, the state of the captured electrons is insensitive to the sequence of the oligomer. Double-stranded DNA does not capture electrons as efficiently as single-stranded oligomers; however, once captured, the electrons are bound more strongly than to the single strands.
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Affiliation(s)
- S G Ray
- Department of Chemical Physics and Chemical Research Support, Weizmann Institute, Rehovot 76100, Israel
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