1
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Shih P, Berkelbach TC. Theory of acoustic polarons in the two-dimensional SSH model applied to the layered superatomic semiconductor Re6Se8Cl2. J Chem Phys 2024; 160:204705. [PMID: 38785287 DOI: 10.1063/5.0205066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 05/04/2024] [Indexed: 05/25/2024] Open
Abstract
Layered superatomic semiconductors, whose building blocks are atomically precise molecular clusters, exhibit interesting electronic and vibrational properties. In recent work [Tulyagankhodjaev et al., Science 382, 438 (2023)], transient reflection microscopy revealed quasi-ballistic exciton dynamics in Re6Se8Cl2, which was attributed to the formation of polarons due to coupling with acoustic phonons. Here, we characterize the electronic, excitonic, and phononic properties with periodic density functional theory. We further parameterize a polaron Hamiltonian with nonlocal (Su-Schrieffer-Heeger) coupling to an acoustic phonon to study the polaron ground state binding energy and dispersion relation with variational wavefunctions. We calculate a polaron binding energy of about 10 meV at room temperature, and the maximum group velocity of our polaron dispersion relation is 1.5 km/s, which is similar to the experimentally observed exciton transport velocity.
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Affiliation(s)
- Petra Shih
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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2
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Xu Y, Chen J, Aydt AP, Zhang L, Sergeyev I, Keeler EG, Choi B, He S, Reichman DR, Friesner RA, Nuckolls C, Steigerwald ML, Roy X, McDermott AE. Electron and Spin Delocalization in [Co 6 Se 8 (PEt 3 ) 6 ] 0/+1 Superatoms. Chemphyschem 2024; 25:e202300064. [PMID: 38057144 DOI: 10.1002/cphc.202300064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 11/01/2023] [Indexed: 12/08/2023]
Abstract
Molecular clusters can function as nanoscale atoms/superatoms, assembling into superatomic solids, a new class of solid-state materials with designable properties through modifications on superatoms. To explore possibilities on diversifying building blocks, here we thoroughly studied one representative superatom, Co6 Se8 (PEt3 )6 . We probed its structural, electronic, and magnetic properties and revealed its detailed electronic structure as valence electrons delocalize over inorganic [Co6 Se8 ] core while ligands function as an insulated shell. 59 Co SSNMR measurements on the core and 31 P, 13 C on the ligands show that the neutral Co6 Se8 (PEt3 )6 is diamagnetic and symmetric, with all ligands magnetically equivalent. Quantum computations cross-validate NMR results and reveal degenerate delocalized HOMO orbitals, indicating aromaticity. Ligand substitution keeps the inorganic core nearly intact. After losing one electron, the unpaired electron in [Co6 Se8 (PEt3 )6 ]+1 is delocalized, causing paramagnetism and a delocalized electron spin. Notably, this feature of electron/spin delocalization over a large cluster is attractive for special single-electron devices.
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Affiliation(s)
- Yunyao Xu
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Jia Chen
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Alexander P Aydt
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Lichirui Zhang
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Ivan Sergeyev
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Eric G Keeler
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Bonnie Choi
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Shoushou He
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - David R Reichman
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Richard A Friesner
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | | | - Xavier Roy
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Ann E McDermott
- Department of Chemistry, Columbia University New York, New York, 10027, USA
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3
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Sengupta T, Khanna SN. Converting CO 2 to formic acid by tuning quantum states in metal chalcogenide clusters. Commun Chem 2023; 6:53. [PMID: 36941466 PMCID: PMC10027883 DOI: 10.1038/s42004-023-00851-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 03/07/2023] [Indexed: 03/23/2023] Open
Abstract
The catalytic conversion of CO2 into valuable chemicals is an effective strategy for reducing its adverse impact on the environment. In this work, the formation of formic acid via CO2 hydrogenation on bare and ligated Ti6Se8 clusters is investigated with gradient-corrected density functional theory. It is shown that attaching suitable ligands (i.e., PMe3, CO) to a metal-chalcogenide cluster transforms it into an effective donor/acceptor enabling it to serve as an efficient catalyst. Furthermore, by controlling the ratio of the attached donor/acceptor ligands, it is possible to predictably alter the barrier heights of the CO2 hydrogenation reaction and, thereby, the rate of CO2 conversion. Our calculation further reveals that by using this strategy, the barrier heights of CO2 hydrogenation can be reduced to ~0.12 eV or possibly even lower, providing unique opportunities to control the reaction rates by using different combinations of donor/acceptor ligands.
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Affiliation(s)
- Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
| | - Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
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4
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Sengupta T, Khanna SN. Rational Design of Bimetallic Metal Chalcogenide Clusters for CO 2 Dissociation. J Phys Chem A 2022; 126:5702-5710. [PMID: 35973159 DOI: 10.1021/acs.jpca.2c03560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thermochemical dissociation of CO2 on pure, ligated, and mixed transition metal (W, Cu) chalcogenide clusters are investigated using the first-principles gradient-corrected density functional approach. It is shown that although the pure and ligated metal chalcogenide clusters exhibit significantly high barriers for CO2 dissociation, the computed barriers for the mixed clusters are relatively lower. The lowest barrier is obtained for the Cu3W3Se8 cluster, which shows a dramatically reduced barrier height of only 0.41 eV. Detailed analysis reveals that the substitution of W by Cu sites leads to a charge transfer from Cu to W sites, resulting in locally active W sites. The lowering of the CO2 dissociation barriers can be attributed to the facile transfer of charge from the locally active W sites and also due to the alteration of the binding energy of CO2 to the charged W sites. Our studies provide an alternate strategy to design novel thermochemical catalysts for CO2 adsorption and subsequent dissociation.
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Affiliation(s)
- Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
| | - Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
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5
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Bista D, Aydt AP, Anderton KJ, Paley DW, Betley TA, Reber AC, Chauhan V, Bartholomew AK, Roy X, Khanna SN. High-Spin Superatom Stabilized by Dual Subshell Filling. J Am Chem Soc 2022; 144:5172-5179. [PMID: 35289175 DOI: 10.1021/jacs.2c00731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Quantum confinement in small symmetric clusters leads to the bunching of electronic states into closely packed shells, enabling the classification of clusters with well-defined valences as superatoms. Like atoms, superatomic clusters with filled shells exhibit enhanced electronic stability. Here, we show that octahedral transition-metal chalcogenide clusters can achieve filled shell electronic configurations when they have 100 valence electrons in 50 orbitals or 114 valence electrons in 57 orbitals. While these stable clusters are intrinsically diamagnetic, we use our understanding of their electronic structures to theoretically predict that a cluster with 107 valence electrons would uniquely combine high stability and high-spin magnetic moment, attained by filling a majority subshell of 57 electrons and a minority subshell of 50 electrons. We experimentally demonstrate this predicted stability, high-spin magnetic moment (S = 7/2), and fully delocalized electronic structure in a new cluster, [NEt4]5[Fe6S8(CN)6]. This work presents the first computational and experimental demonstration of the importance of dual subshell filling in transition-metal chalcogenide clusters.
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Affiliation(s)
- Dinesh Bista
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23220, United States
| | - Alexander P Aydt
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Kevin J Anderton
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Daniel W Paley
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Theodore A Betley
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Arthur C Reber
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23220, United States
| | - Vikas Chauhan
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23220, United States
| | | | - Xavier Roy
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23220, United States
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6
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Li J, Cui M, Yang H, Chen J, Cheng S. Ligand-field regulated superalkali behavior of the aluminum-based clusters with distinct shell occupancy. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.02.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Bista D, Sengupta T, Reber AC, Khanna SN. Interfacial magnetism in a fused superatomic cluster [Co 6Se 8(PEt 3) 5] 2. NANOSCALE 2021; 13:15763-15769. [PMID: 34528648 DOI: 10.1039/d1nr00876e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An isolated Co6Se8(PEt3)6 cluster is non-magnetic; however, we find that a magnetic unit can be formed by fusing two Co6Se8(PEt3)5 superatoms into a [Co6Se8(PEt3)5]2 dimer. Theoretical studies indicate that the dumbbell-shaped [Co6Se8(PEt3)5]2 dimer has a spin moment of 2μB, and the spin density is primarily localized at the interfacial Co-sites where two clusters are fused into a dimer. The dimer has a low ionization energy of 4.17 eV, allowing the dimer to donate charge to C70 during the formation of a cluster assembled material, as seen in recent experiments by Nuckolls and co-workers. The donation of charge causes the dimer's magnetic moment to drop from 2μB to 1μB. We hypothesize that adding electrons to the dimer, such as doping impurities to the crystal lattice, may enhance the magnetic moment by neutralizing the charged cluster. This reveals a strategy for stabilizing magnetic moments in ligated cluster assemblies.
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Affiliation(s)
- Dinesh Bista
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
| | - Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
| | - Arthur C Reber
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
| | - Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
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8
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Khanna SN, Reber AC, Bista D, Sengupta T, Lambert R. The superatomic state beyond conventional magic numbers: Ligated metal chalcogenide superatoms. J Chem Phys 2021; 155:120901. [PMID: 34598575 DOI: 10.1063/5.0062582] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The field of cluster science is drawing increasing attention due to the strong size and composition-dependent properties of clusters and the exciting prospect of clusters serving as the building blocks for materials with tailored properties. However, identifying a unifying central paradigm that provides a framework for classifying and understanding the diverse behaviors is an outstanding challenge. One such central paradigm is the superatom concept that was developed for metallic and ligand-protected metallic clusters. The periodic electronic and geometric closed shells in clusters result in their properties being based on the stability they gain when they achieve closed shells. This stabilization results in the clusters having a well-defined valence, allowing them to be classified as superatoms-thus extending the Periodic Table to a third dimension. This Perspective focuses on extending the superatomic concept to ligated metal-chalcogen clusters that have recently been synthesized in solutions and form assemblies with counterions that have wide-ranging applications. Here, we illustrate that the periodic patterns emerge in the electronic structure of ligated metal-chalcogenide clusters. The stabilization gained by the closing of their electronic shells allows for the prediction of their redox properties. Further investigations reveal how the selection of ligands may control the redox properties of the superatoms. These ligated clusters may serve as chemical dopants for two-dimensional semiconductors to control their transport characteristics. Superatomic molecules of multiple metal-chalcogen superatoms allow for the formation of nano-p-n junctions ideal for directed transport and photon harvesting. This Perspective outlines future developments, including the synthesis of magnetic superatoms.
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Affiliation(s)
- Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, USA
| | - Arthur C Reber
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, USA
| | - Dinesh Bista
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, USA
| | - Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, USA
| | - Ryan Lambert
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, USA
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9
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Diaz CM, Basurto L, Adhikari S, Yamamoto Y, Ruzsinszky A, Baruah T, Zope RR. Self-interaction-corrected Kohn-Sham effective potentials using the density-consistent effective potential method. J Chem Phys 2021; 155:064109. [PMID: 34391355 DOI: 10.1063/5.0056561] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Density functional theory (DFT) and beyond-DFT methods are often used in combination with photoelectron spectroscopy to obtain physical insights into the electronic structure of molecules and solids. The Kohn-Sham eigenvalues are not electron removal energies except for the highest occupied orbital. The eigenvalues of the highest occupied molecular orbitals often underestimate the electron removal or ionization energies due to the self-interaction (SI) errors in approximate density functionals. In this work, we adapt and implement the density-consistent effective potential method of Kohut, Ryabinkin, and Staroverov [J. Chem. Phys. 140, 18A535 (2014)] to obtain SI-corrected local effective potentials from the SI-corrected Fermi-Löwdin orbitals and density in the Fermi-Löwdin orbital self-interaction correction scheme. The implementation is used to obtain the density of states (photoelectron spectra) and HOMO-LUMO gaps for a set of molecules and polyacenes. Good agreement with experimental values is obtained compared to a range of SI uncorrected density functional approximations.
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Affiliation(s)
- Carlos M Diaz
- Department of Physics, University of Texas at El Paso, El Paso, Texas 79968, USA
| | - Luis Basurto
- Department of Physics, University of Texas at El Paso, El Paso, Texas 79968, USA
| | - Santosh Adhikari
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Yoh Yamamoto
- Department of Physics, University of Texas at El Paso, El Paso, Texas 79968, USA
| | - Adrienn Ruzsinszky
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Tunna Baruah
- Department of Physics, University of Texas at El Paso, El Paso, Texas 79968, USA
| | - Rajendra R Zope
- Department of Physics, University of Texas at El Paso, El Paso, Texas 79968, USA
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10
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Omoda T, Takano S, Tsukuda T. Toward Controlling the Electronic Structures of Chemically Modified Superatoms of Gold and Silver. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2001439. [PMID: 32696588 DOI: 10.1002/smll.202001439] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/12/2020] [Indexed: 06/11/2023]
Abstract
Atomically precise gold/silver clusters protected by organic ligands L, [(Au/Ag)x Ly ]z , have gained increasing interest as building units of functional materials because of their novel photophysical and physicochemical properties. The properties of [(Au/Ag)x Ly ]z are intimately associated with the quantized electronic structures of the metallic cores, which can be viewed as superatoms from the analogy of naked Au/Ag clusters. Thus, establishment of the correlation between the geometric and electronic structures of the superatomic cores is crucial for rational design and improvement of the properties of [(Au/Ag)x Ly ]z . This review article aims to provide a qualitative understanding on how the electronic structures of [(Au/Ag)x Ly ]z are affected by geometric structures of the superatomic cores with a focus on three factors: size, shape, and composition, on the basis of single-crystal X-ray diffraction data. The knowledge accumulated here will constitute a basis for the development of ligand-protected Au/Ag clusters as new artificial elements on a nanometer scale.
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Affiliation(s)
- Tsubasa Omoda
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Shinjiro Takano
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Tatsuya Tsukuda
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto, 615-8520, Japan
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11
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Mason JL, Folluo CN, Jarrold CC. More than little fragments of matter: Electronic and molecular structures of clusters. J Chem Phys 2021; 154:200901. [DOI: 10.1063/5.0054222] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jarrett L. Mason
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, USA
| | - Carley N. Folluo
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, USA
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, USA
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12
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Koyasu K, Tsukuda T. Gas-phase studies of chemically synthesized Au and Ag clusters. J Chem Phys 2021; 154:140901. [DOI: 10.1063/5.0041812] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Kiichirou Koyasu
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033,
Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520,
Japan
| | - Tatsuya Tsukuda
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033,
Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520,
Japan
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13
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Bista D, Sengupta T, Reber AC, Khanna SN. A Magnetic Superatomic Dimer with an Intense Internal Electric Dipole Moment. J Phys Chem A 2021; 125:816-824. [DOI: 10.1021/acs.jpca.0c10262] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dinesh Bista
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
| | - Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
| | - Arthur C. Reber
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
| | - Shiv N. Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000, United States
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14
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Structural order enhances charge carrier transport in self-assembled Au-nanoclusters. Nat Commun 2020; 11:6188. [PMID: 33273476 PMCID: PMC7713068 DOI: 10.1038/s41467-020-19461-x] [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: 02/15/2020] [Accepted: 10/01/2020] [Indexed: 11/08/2022] Open
Abstract
The collective properties of self-assembled nanoparticles with long-range order bear immense potential for customized electronic materials by design. However, to mitigate the shortcoming of the finite-size distribution of nanoparticles and thus, the inherent energetic disorder within assemblies, atomically precise nanoclusters are the most promising building blocks. We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au32(nBu3P)12Cl8 nanoclusters into micro-crystals. This enables the determination of emergent optoelectronic properties which resulted from long-range order in such assemblies. Compared to the same nanoclusters in glassy, polycrystalline ensembles, we find a 100-fold increase in the electric conductivity and charge carrier mobility as well as additional optical transitions. We show that these effects are due to a vanishing energetic disorder and a drastically reduced activation energy to charge transport in the highly ordered assemblies. This first correlation of structure and electronic properties by comparing glassy and crystalline self-assembled superstructures of atomically precise gold nanoclusters paves the way towards functional materials with novel collective optoelectronic properties.
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15
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Liu G, Zhang C, Ciborowski SM, Asthana A, Cheng L, Bowen KH. Mapping the Electronic Structure of the Uranium(VI) Dinitride Molecule, UN 2. J Phys Chem A 2020; 124:6486-6492. [PMID: 32700533 DOI: 10.1021/acs.jpca.0c03735] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A combined anion photoelectron spectroscopic and relativistic coupled-cluster computational study of the electronic structure of the UN2 molecule is presented. Because the photoelectron spectrum of the uranium dinitride negative ion, UN2-, directly reflects the electronic structure of neutral UN2, we have measured and relied upon the photoelectron spectrum of the UN2- anion as a means of mapping the electronic structure of neutral UN2. In addition to the electron affinity of the UN2 ground state, energy levels of the UN2 excited states were well characterized by the close interplay between the experiment and high-level theory. We found that both electron attachment and electronic excitation significantly bend the UN2 molecule and elongate its U≡N bond. Implications for the activation of UN2 are discussed.
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Affiliation(s)
- Gaoxiang Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Chaoqun Zhang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Sandra M Ciborowski
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ayush Asthana
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Lan Cheng
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kit H Bowen
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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16
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Bista D, Chauhan V, Sengupta T, Reber AC, Khanna SN. A ligand-induced homojunction between aluminum-based superatomic clusters. NANOSCALE 2020; 12:12046-12056. [PMID: 32469025 DOI: 10.1039/d0nr02611e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A superatomic molecule formed by joining two metallic clusters linked by an organometallic bridge can behave like a semiconductor and the addition of ligands can induce a significant energy level shift across an inter-cluster homojunction. This shift is induced by the N-ethyl-2-pyrrolidone ligands, and the placement of the ligands strongly affects the direction of the dipole moment, including the case where the dipole moment is parallel to the cluster interface. This computational study provides an alternative strategy for constructing nanometer-scale electronic interfaces between clusters mimicking semiconductor motifs. The semiconducting features in the PAl12 clusters emerge from the grouping of the quantum states in a confined nearly free electron gas that creates a substantial energy gap. An organometallic Ge(CH3)2(CH2)2 bridge links the clusters while maintaining the cluster's electronic shell structure. The amount of level shifting between the bridged clusters can be changed by controlling the number of ligands. Attaching multiple ligands can result in a broken gap energy alignment in which the HOMO level of one cluster is aligned with the LUMO level of the other bridged cluster. Furthermore, the singly ligated bridged superatomic molecule is found to exhibit promising features to separate the electron-hole pairs for photovoltaic applications.
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Affiliation(s)
- Dinesh Bista
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23284-2000, USA.
| | - Vikas Chauhan
- Ramjas College, University of Delhi, Delhi-110007, India
| | - Turbasu Sengupta
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23284-2000, USA.
| | - Arthur C Reber
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23284-2000, USA.
| | - Shiv N Khanna
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23284-2000, USA.
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17
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Reber AC, Chauhan V, Bista D, Khanna SN. Superatomic molecules with internal electric fields for light harvesting. NANOSCALE 2020; 12:4736-4742. [PMID: 32049078 DOI: 10.1039/c9nr09229c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Traditional p-n junctions used for photovoltaics require an interface where a light induced electron-hole pair is separated by an electric field. Developing alternative strategies for forming strong internal electric fields for electron-hole pair separation offers the possibility for better performance. We demonstrate that fusing two superatomic clusters with donor/acceptor ligands on opposite sides of the cluster leads to such a strong internal electric field. In two fused metal-chalcogenide Re6S8Cl2(L)4 clusters with donor PMe3 ligands and acceptor CO ligands on the opposite sides of the fused clusters, the electronic levels undergo shifts analogous to band bending in traditional p-n junctions. The fused cluster has a large dipole moment, and an optical spectrum that strongly absorbs excitation above the HOMO-LUMO gap of the fused clusters, but is optically very weak for the lowest energy excitation that can lead to electron-hole pair recombination. This is because the electron is localized on the CO portion of the fused cluster, while the electron-hole pair is localized on the PMe3 side of the cluster. It is shown that the electronic states localized on each side of the cluster can be aligned/misaligned by applying a voltage in different directions, offering diode like characteristics.
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Affiliation(s)
- Arthur C Reber
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23220, USA.
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