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Vaida ME, Rawal TB, Bernhardt TM, Marsh BM, Rahman TS, Leone SR. Nonmetal-to-Metal Transition of Magnesia Supported Au Clusters Affects the Ultrafast Dissociation Dynamics of Adsorbed CH 3Br Molecules. J Phys Chem Lett 2022; 13:4747-4753. [PMID: 35612537 DOI: 10.1021/acs.jpclett.2c00968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The detection of intermediate species and the correlation of their ultrafast dynamics with the morphology and electronic structure of a surface is crucial to fully understand and control heterogeneous photoinduced and photocatalytic reactions. In this work, the ultrafast photodissociation dynamics of CH3Br molecules adsorbed on variable-size Au clusters on MgO/Mo(100) is investigated by monitoring the CH3+ transient evolution using a pump-probe technique in conjunction with surface mass spectrometry. Furthermore, extreme-UV photoemission spectroscopy in combination with theoretical calculations is employed to study the electronic structure of the Au clusters on MgO/Mo(100). Changes in the ultrafast dynamics of the CH3+ fragment are correlated with the electronic structure of Au as it evolves from monomers to small nonmetallic clusters to larger nanoparticles with a metallic character. This work provides a new avenue to a detailed understanding of how surface-photoinduced chemical reactions are influenced by the composition and electronic structure of the surface.
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Affiliation(s)
- Mihai E Vaida
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
- Renewable Energy and Chemical Transformations Cluster, University of Central Florida, Orlando, Florida 32816, United States
| | - Takat B Rawal
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
| | - Thorsten M Bernhardt
- Institute of Surface Chemistry and Catalysis, University of Ulm, 89069 Ulm, Germany
| | - Brett M Marsh
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
- Renewable Energy and Chemical Transformations Cluster, University of Central Florida, Orlando, Florida 32816, United States
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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Feizollah P, Berg MJ. Electromagnetically induced modification of gold optical properties. OPTICS EXPRESS 2022; 30:18374-18391. [PMID: 36221640 DOI: 10.1364/oe.459728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/02/2022] [Indexed: 06/16/2023]
Abstract
The reflection of light from a metal film, i.e., a mirror, is among the most fundamental and well-understood effects in optics. If the film thickness is greater than the wavelength, reflection is strong and is explained in simple terms by the Fresnel equations. For film thickness much less than the wavelength, reflection is far weaker and more exotic effects become possible. This is especially so if the light illuminating the film is pulsed at the femtosecond time scale. In this work, a phenomenon is proposed where few-femtosecond laser pulses temporarily modify a thin metal film's optical properties via processes that appear linear and classical in nature. By casting a pulsed standing-wave pattern across the metal surface, we consider the possibility that conduction electrons are redistributed to create temporary regions of partly enhanced or reduced density without the excitation of inter-band transitions. The process would constitute a temporary change to the conductivity of the metal, and thus, may be observable as changes to the metal's transmittance and reflectance. In regions where the density is enhanced (reduced), the transmittance is decreased (increased). The concept is termed Electromagnetically Induced Modification (EIM) and is premised on the fact that the pulse length is shorter than the relaxation time of the conduction electrons. An experiment is conducted to test the concept by measuring the change in reflectance and transmittance of gold films with thickness ranging from 20-300 Angstrom. The results show that the film's transmittance decreases only when the standing-wave pattern is present. As the pulse length is increased, or as the film thickness is increased, the changes disappear. The changes show little dependence on the pulse intensity as it is varied by a factor of two. To gain further insight, the Drude theory is used to develop a simplified model for EIM, which qualitatively agrees with the observations. However, neither the experiment nor the model can prove the validity of the EIM concept. As such, an assessment is made for the potential of alternative well-known processes to explain the observations.
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Schütz M, Gemel C, Klein W, Fischer RA, Fässler TF. Intermetallic phases meet intermetalloid clusters. Chem Soc Rev 2021; 50:8496-8510. [PMID: 34114586 DOI: 10.1039/d1cs00286d] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this article intermetalloid clusters of Cu-Zn, Cu-AI, Cu-Sn, and Cu-Pb are discussed. Intermetallic compounds based on these metal combinations are of the Hume-Rothery type with well-defined structures related to the valence electron count of the involved metals. Many Zintl-type and molecular clusters with these metals are known with remarkable structural parallels to the respective solid-state phases. On several examples, this article discusses intermetalloid clusters in terms of their metal core structures and relates them to structural principles in intermetallic solid-state phases. Also the syntheses of such clusters are addressed. Zintl-type and molecular clusters are most generally accessible from organometallic precursor complexes with redox processes between the different metals as an underlying synthesis concept.
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Affiliation(s)
- Max Schütz
- Department of Chemistry, Technical University of Munich, Munich, Germany.
| | - Christian Gemel
- Department of Chemistry, Technical University of Munich, Munich, Germany.
| | - Wilhelm Klein
- Department of Chemistry, Technical University of Munich, Munich, Germany.
| | - Roland A Fischer
- Department of Chemistry, Technical University of Munich, Munich, Germany.
| | - Thomas F Fässler
- Department of Chemistry, Technical University of Munich, Munich, Germany.
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Ernst WE, Hauser AW. Metal clusters synthesized in helium droplets: structure and dynamics from experiment and theory. Phys Chem Chem Phys 2020; 23:7553-7574. [PMID: 33057510 DOI: 10.1039/d0cp04349d] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Metal clusters have drawn continuous interest because of their high potential for the assembly of matter with special properties that may significantly differ from the corresponding bulk. Controlled combination of particular elements in one nanoparticle can increase the options for the creation of new materials for photonic, catalytic, or electronic applications. Superfluid helium droplets provide confinement and ultralow temperature, i.e. an ideal environment for the atom-by-atom aggregation of a new nanoparticle. This perspective presents a review of the current research progress on the synthesis of tailored metal and metal oxide clusters including core-shell designs, their characterization within the helium droplet beam, deposition on various solid substrates, and analysis via surface diagnostics. Special attention is given to the thermal properties of mixed metal clusters and questions about alloy formation on the nanoscale. Experimental results are accompanied by theoretical approaches employing computational chemistry, molecular dynamics simulations and He density functional theory.
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Affiliation(s)
- Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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Eulenstein AR, Franzke YJ, Bügel P, Massa W, Weigend F, Dehnen S. Stabilizing a metalloid {Zn 12} unit within a polymetallide environment in [K 2Zn 20Bi 16] 6. Nat Commun 2020; 11:5122. [PMID: 33046705 PMCID: PMC7552394 DOI: 10.1038/s41467-020-18799-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 09/01/2020] [Indexed: 11/27/2022] Open
Abstract
The access to molecules comprising direct Zn–Zn bonds has become very topical in recent years for various reasons. Low-valent organozinc compounds show remarkable reactivities, and larger Zn–Zn-bonded gas-phase species exhibit a very unusual coexistence of insulating and metallic properties. However, as Zn atoms do not show a high tendency to form clusters in condensed phases, synthetic approaches for generating purely inorganic metalloid Znx units under ambient conditions have been lacking so far. Here we show that the reaction of a highly reductive solid with the nominal composition K5Ga2Bi4 with ZnPh2 at room temperature yields the heterometallic cluster anion [K2Zn20Bi16]6–. A 24-atom polymetallide ring embeds a metalloid {Zn12} unit. Density functional theory calculations reveal multicenter bonding, an essentially zero-valent situation in the cluster center, and weak aromaticity. The heterometallic character, the notable electron-delocalization, and the uncommon nano-architecture points at a high potential for nano-heterocatalysis. Low-valent zinc clusters, though exceedingly rare, are appealing synthetic targets because there is evidence that they may show unconventional chemical and physical behavior. Here, the authors obtain a large heterometallic zinc-bismuth cluster anion and discover that it bears a metalloid {Zn12} core with four-center bonding and essentially zero-valent character.
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Affiliation(s)
- Armin R Eulenstein
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany.,Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, Hans-Meerwein-Str. 6, 35032, Marburg, Germany
| | - Yannick J Franzke
- Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, 76131, Karlsruhe, Germany.,Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany
| | - Patrick Bügel
- Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Werner Massa
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany
| | - Florian Weigend
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany. .,Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
| | - Stefanie Dehnen
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany. .,Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, Hans-Meerwein-Str. 6, 35032, Marburg, Germany.
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Young BT, Pathan MAK, Jiang T, Le D, Marrow N, Nguyen T, Jordan CE, Rahman TS, Popolan-Vaida DM, Vaida ME. Catalytic C 2H 2 synthesis via low temperature CO hydrogenation on defect-rich 2D-MoS 2 and 2D-MoS 2 decorated with Mo clusters. J Chem Phys 2020; 152:074706. [PMID: 32087629 DOI: 10.1063/1.5129712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Rational design of novel catalytic materials used to synthesize storable fuels via the CO hydrogenation reaction has recently received considerable attention. In this work, defect poor and defect rich 2D-MoS2 as well as 2D-MoS2 decorated with Mo clusters are employed as catalysts for the generation of acetylene (C2H2) via the CO hydrogenation reaction. Temperature programmed desorption is used to study the interaction of CO and H2 molecules with the MoS2 surface as well as the formation of reaction products. The experiments indicate the presence of four CO adsorption sites below room temperature and a competitive adsorption between the CO and H2 molecules. The investigations show that CO hydrogenation is not possible on defect poor MoS2 at low temperatures. However, on defect rich 2D-MoS2, small amounts of C2H2 are produced, which desorb from the surface at temperatures between 170 K and 250 K. A similar C2H2 signal is detected from defect poor 2D-MoS2 decorated with Mo clusters, which indicates that low coordinated Mo atoms on 2D-MoS2 are responsible for the formation of C2H2. Density functional theory investigations are performed to explore possible adsorption sites of CO and understand the formation mechanism of C2H2 on MoS2 and Mo7/MoS2. The theoretical investigation indicates a strong binding of C2H2 on the Mo sites of MoS2 preventing the direct desorption of C2H2 at low temperatures as observed experimentally. Instead, the theoretical results suggest that the experimental data are consistent with a mechanism in which CHO radical dimers lead to the formation of C2H2 that presents an exothermic desorption.
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Affiliation(s)
- Brett T Young
- Department of Chemistry, University of Central Florida, Orlando, Florida 32816, USA
| | - Md Afjal Khan Pathan
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Tao Jiang
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Duy Le
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Nikki Marrow
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Trong Nguyen
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Cody E Jordan
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | | | - Mihai E Vaida
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
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Marsh BM, Lamoureux BR, Leone SR. Ultrafast time-resolved extreme ultraviolet (XUV) photoelectron spectroscopy of hole transfer in a Zn/n-GaP Schottky junction. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2018; 5:054502. [PMID: 30417027 PMCID: PMC6197984 DOI: 10.1063/1.5046776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/18/2018] [Indexed: 06/09/2023]
Abstract
The addition of a metal overlayer to a semiconductor photocatalyst is a frequently used synthetic route to passivate the surface and, via the formation of a Schottky barrier, to enhance catalytic activity of the photocatalyst material. While it is known that Schottky junctions decrease recombination by charge separation, measurements of the depletion region dynamics have remained elusive. Here, we use ultrafast pump-probe transient photoelectron spectroscopy to measure material-specific dynamics of the Zn/n-GaP(100) system. Through photoemission measurements the Schottky barrier height is determined to be 2.1 ± 0.1 eV at 10 monolayers of total Zn deposition. Transient photoemission measurements utilizing a 400 nm pump pulse show that, after excitation, holes are transferred from n-GaP(100) to the Zn overlayer within a few ps, as evidenced by shifts of the Zn 3d and Ga 3d core levels to higher binding energies. Within the timescale of the experiment (130 ps) no carrier recombination is observed in the junction. Furthermore, a long-lived surface photovoltage signal is observed at times >1 ms after photoexcitation. This work further exemplifies the potential of transient extreme ultraviolet photoelectron spectroscopy as a material-specific technique for the study of heterojunctions.
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Affiliation(s)
| | - Bethany R Lamoureux
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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