1
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Tesvara C, Walenta C, Sautet P. Oxidative decomposition of dimethyl methylphosphonate on rutile TiO 2(110): the role of oxygen vacancies. Phys Chem Chem Phys 2022; 24:23402-23419. [PMID: 36128829 DOI: 10.1039/d2cp02246j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The decomposition of dimethyl methylphosphonate (DMMP, (CH3O)2P(O)(CH3)), a simulant to the toxic nerve agent Sarin, on the rutile TiO2(110) surface has been studied with temperature programmed desorption (TPD) and density functional theory (DFT) calculations. The reactivity of the TiO2(110) surface for DMMP decomposition is shown to be low, with mainly molecular desorption and only a small fraction of methanol and formaldehyde decomposition products seen from TPD at around 650 K. In addition, this amount of products is similar to the number of O vacancies on the surface. DFT calculations show that O vacancies are key for P-OCH3 bond cleavage of DMMP, lowering the barrier by 0.7 eV and enabling the reactive process to occur at around 600 K. This is explained by the closer position of DMMP with respect to the surface in the presence of O vacancies. Calculations show that the produced methoxy groups can transform into gas phase formaldehyde and methanol at the considered temperature (600 K), in agreement with experiments. O-C bond cleavage of DMMP is also a viable pathway at such a high temperature (600 K) for DMMP decomposition on r-TiO2, even in the absence of O vacancies, but the formation of a gas phase product is energetically unfavorable. O vacancies hence are the active sites for decomposition of DMMP into gas phase products on r-TiO2(110).
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Affiliation(s)
- Celine Tesvara
- Chemical and Biomolecular Engineering Department, University of California, Los Angeles, CA 90095, USA.
| | - Constantin Walenta
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Philippe Sautet
- Chemical and Biomolecular Engineering Department, University of California, Los Angeles, CA 90095, USA. .,Chemistry and Biochemistry Department, University of California, Los Angeles, CA 90095, USA
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2
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Williams OBJ, Katsiev K, Baek B, Harrison G, Thornton G, Idriss H. Direct Visualization of a Gold Nanoparticle Electron Trapping Effect. J Am Chem Soc 2022; 144:1034-1044. [PMID: 34985273 DOI: 10.1021/jacs.1c12197] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A new atomic-scale anisotropy in the photoreaction of surface carboxylates on rutile TiO2(110) induced by gold clusters is found. STM and DFT+U are used to study this phenomenon by monitoring the photoreaction of a prototype hole-scavenger molecule, benzoic acid, over stoichiometric (s) s-TiO2, Au9/s-TiO2, and reduced (r) Au9/r-TiO2. STM results show that benzoic acid adsorption displaces a large fraction of Au clusters from the terraces toward their edges. DFT calculations explain that Au9 clusters on stoichiometric TiO2 are distorted by benzoic acid adsorption. The influence of sub-monolayers of Au on the UV/visible photoreaction of benzoic acid was explored at room temperature, with adsorbate depletion taken as a measure of activity. The empty sites, observed upon photoexcitation, occurred in elongated chains (2 to 6 molecules long) in the [11̅0] and [001] directions. A roughly 3-fold higher depletion rate is observed in the [001] direction. This is linked to the anisotropic conduction of excited electrons along [001], with subsequent trapping by Au clusters leaving a higher concentration of holes and thus an increased decomposition rate. To our knowledge this is the first time that atomic-scale directionality of a chemical reaction is reported upon photoexcitation of the semiconductor.
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Affiliation(s)
- Oscar Bentley Jerdmyr Williams
- Department of Chemistry and London Centre for Nanotechnology (LCN), University College London (UCL), WC1H 0AH, London, U.K
| | - Khabiboulakh Katsiev
- Surface Science and Advanced Characterisation, SABIC-CRD at King Abdullah University for Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Byeongjin Baek
- SABIC Global Corporate Research, Sugar Land, Texas 77478, United States
| | - George Harrison
- KAUST Solar Center (KSC), Physical Sciences and Engineering Division (PSE), King Abdullah University for Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Geoff Thornton
- Department of Chemistry and London Centre for Nanotechnology (LCN), University College London (UCL), WC1H 0AH, London, U.K
| | - Hicham Idriss
- Department of Chemistry and London Centre for Nanotechnology (LCN), University College London (UCL), WC1H 0AH, London, U.K.,Surface Science and Advanced Characterisation, SABIC-CRD at King Abdullah University for Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
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3
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Truong PL, Kidanemariam A, Park J. A critical innovation of photocatalytic degradation for toxic chemicals and pathogens in air. J IND ENG CHEM 2021. [DOI: 10.1016/j.jiec.2021.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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4
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Schuler B, Lee JH, Kastl C, Cochrane KA, Chen CT, Refaely-Abramson S, Yuan S, van Veen E, Roldán R, Borys NJ, Koch RJ, Aloni S, Schwartzberg AM, Ogletree DF, Neaton JB, Weber-Bargioni A. How Substitutional Point Defects in Two-Dimensional WS 2 Induce Charge Localization, Spin-Orbit Splitting, and Strain. ACS NANO 2019; 13:10520-10534. [PMID: 31393700 DOI: 10.1021/acsnano.9b04611] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Control of impurity concentrations in semiconducting materials is essential to device technology. Because of their intrinsic confinement, the properties of two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are more sensitive to defects than traditional bulk materials. The technological adoption of TMDs is dependent on the mitigation of deleterious defects and guided incorporation of functional foreign atoms. The first step toward impurity control is the identification of defects and assessment of their electronic properties. Here, we present a comprehensive study of point defects in monolayer tungsten disulfide (WS2) grown by chemical vapor deposition using scanning tunneling microscopy/spectroscopy, CO-tip noncontact atomic force microscopy, Kelvin probe force spectroscopy, density functional theory, and tight-binding calculations. We observe four different substitutional defects: chromium (CrW) and molybdenum (MoW) at a tungsten site, oxygen at sulfur sites in both top and bottom layers (OS top/bottom), and two negatively charged defects (CD type I and CD type II). Their electronic fingerprints unambiguously corroborate the defect assignment and reveal the presence or absence of in-gap defect states. CrW forms three deep unoccupied defect states, two of which arise from spin-orbit splitting. The formation of such localized trap states for CrW differs from the MoW case and can be explained by their different d shell energetics and local strain, which we directly measured. Utilizing a tight-binding model the electronic spectra of the isolectronic substitutions OS and CrW are mimicked in the limit of a zero hopping term and infinite on-site energy at a S and W site, respectively. The abundant CDs are negatively charged, which leads to a significant band bending around the defect and a local increase of the contact potential difference. In addition, CD-rich domains larger than 100 nm are observed, causing a work function increase of 1.1 V. While most defects are electronically isolated, we also observed hybrid states formed between CrW dimers. The important role of charge localization, spin-orbit coupling, and strain for the formation of deep defect states observed at substitutional defects in WS2 as reported here will guide future efforts of targeted defect engineering and doping of TMDs.
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Affiliation(s)
- Bruno Schuler
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jun-Ho Lee
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Christoph Kastl
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Walter-Schottky-Institut and Physik-Department , Technical University of Munich , Garching 85748 , Germany
| | - Katherine A Cochrane
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Christopher T Chen
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Sivan Refaely-Abramson
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Materials and Interfaces , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Shengjun Yuan
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology , Wuhan University , Wuhan 430072 , China
| | - Edo van Veen
- Radboud University of Nijmegen , Institute for Molecules and Materials , Heijendaalseweg 135 , 6525 AJ , Nijmegen , The Netherlands
| | - Rafael Roldán
- Instituto de Ciencia de Materiales de Madrid , ICMM-CSIC, Cantoblanco, E-28049 , Madrid , Spain
| | - Nicholas J Borys
- Department of Physics , Montana State University , Bozeman , Montana 59717 , United States
| | - Roland J Koch
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Shaul Aloni
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Adam M Schwartzberg
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - D Frank Ogletree
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jeffrey B Neaton
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Physics , University of California at Berkeley , Berkeley , California 94720 , United States
- Kavli Energy Nanosciences Institute at Berkeley , Berkeley , California 94720 , United States
| | - Alexander Weber-Bargioni
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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5
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Sarkar A, Khan GG. The formation and detection techniques of oxygen vacancies in titanium oxide-based nanostructures. NANOSCALE 2019; 11:3414-3444. [PMID: 30734804 DOI: 10.1039/c8nr09666j] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
TiO2 and other titanium oxide-based nanomaterials have drawn immense attention from researchers in different scientific domains due to their fascinating multifunctional properties, relative abundance, environmental friendliness, and bio-compatibility. However, the physical and chemical properties of titanium oxide-based nanomaterials are found to be explicitly dependent on the presence of various crystal defects. Oxygen vacancies are the most common among them and have always been the subject of both theoretical and experimental research as they play a crucial role in tuning the inherent properties of titanium oxides. This review highlights different strategies for effectively introducing oxygen vacancies in titanium oxide-based nanomaterials, as well as a discussion on the positions of oxygen vacancies inside the TiO2 band gap based on theoretical calculations. Additionally, a detailed review of different experimental techniques that are extensively used for identifying oxygen vacancies in TiO2 nanostructures is also presented.
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Affiliation(s)
- Ayan Sarkar
- Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Block-JD2, Sector-III, Salt Lake, Kolkata 700106, West Bengal, India.
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6
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Maddox W, Acharya DP, Leong GJ, Sutter P, Ciobanu CV. Bias-Dependent Scanning Tunneling Microscopy Signature of Bridging-Oxygen Vacancies on Rutile TiO 2(110). ACS OMEGA 2018; 3:6540-6545. [PMID: 31458830 PMCID: PMC6644455 DOI: 10.1021/acsomega.8b01056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 06/07/2018] [Indexed: 06/10/2023]
Abstract
The rutile TiO2(110) surface has long-served as a well-characterized, prototypical transition-metal oxide surface used in heterogeneous catalysis and photocatalytic water splitting. Naturally occurring defects on this surface, called bridging-oxygen (BO) vacancies, are important as they determine the overall reactivity of the surface. Herein, we report a bias-dependent, scanning tunneling microscopy (STM) signature of the BO vacancies on TiO2(110): for sample bias voltages past a threshold of +3 V, the bright vacancies are flanked on either side (along the oxygen row) by two dark spots approximately shaped like half-moons. The BO vacancies have a bright aspect below the threshold bias also but are not surrounded by half-moon dark depressions. Using generalized gradient approximation calculations with Hubbard correction (GGA + U) for projected density of states (DOS) and simulated STM images, we find that the bias-dependent STM signature originates from (i) local DOS maxima of all BOs (lighter background that occurs above the threshold bias) and (ii) the increased separation between the first and second BO atoms neighboring the vacancy which leads to an apparent dip between these neighboring oxygens. These results offer a new striking example of the STM signature that appears without switching the polarity of the bias. Similar approaches can be employed for seeking distinguishing features on the surfaces of other large band gap semiconductors and insulators.
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Affiliation(s)
- Willie
B. Maddox
- Department
of Mechanical Engineering, Colorado School
of Mines, 1500 Illinois
Street, Golden, Colorado 80401, United States
| | - Danda P. Acharya
- Global
Foundries, 400 Stone
Break Extension, Malta, New
York 12020, United
States
| | - G. Jeremy Leong
- Department
of Mechanical Engineering, Colorado School
of Mines, 1500 Illinois
Street, Golden, Colorado 80401, United States
| | - Peter Sutter
- Department
of Electrical and Computer Engineering, University of Nebraska-Lincoln, P.O.
Box 880511, Lincoln, Nebraska 68588, United States
| | - Cristian V. Ciobanu
- Department
of Mechanical Engineering, Colorado School
of Mines, 1500 Illinois
Street, Golden, Colorado 80401, United States
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7
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Setvin M, Hulva J, Parkinson GS, Schmid M, Diebold U. Electron transfer between anatase TiO 2 and an O 2 molecule directly observed by atomic force microscopy. Proc Natl Acad Sci U S A 2017; 114:E2556-E2562. [PMID: 28289217 PMCID: PMC5380104 DOI: 10.1073/pnas.1618723114] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O2 molecules in the triplet state from negatively charged (O2)- radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO2 surface, we show that the tip-generated (O2)- radicals are identical to those created when (i) an O2 molecule accepts an electron from a near-surface dopant or (ii) when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO2 and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O2 and band bending induced by the (O2)- radicals. Temperature-programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.
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Affiliation(s)
- Martin Setvin
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | - Jan Hulva
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | | | - Michael Schmid
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
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8
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González C, Biel B, Dappe YJ. Adsorption of small inorganic molecules on a defective MoS2monolayer. Phys Chem Chem Phys 2017; 19:9485-9499. [DOI: 10.1039/c7cp00544j] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Different molecules physisorbed, chemisorbed or dissociated on a defective MoS2layer.
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Affiliation(s)
- César González
- Departamento de Electrónica y Tecnología de Computadores
- Campus de Fuente Nueva & CITIC
- Universidad de Granada
- E-18071 Granada
- Spain
| | - Blanca Biel
- Departamento de Electrónica y Tecnología de Computadores
- Campus de Fuente Nueva & CITIC
- Universidad de Granada
- E-18071 Granada
- Spain
| | - Yannick J. Dappe
- SPEC
- CEA
- CNRS
- Université Paris-Saclay
- CEA Saclay 91191 Gif-sur-Yvette Cedex
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9
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Grinter DC, R Remesal E, Luo S, Evans J, Senanayake SD, Stacchiola DJ, Graciani J, Fernández Sanz J, Rodriguez JA. Potassium and Water Coadsorption on TiO 2(110): OH-Induced Anchoring of Potassium and the Generation of Single-Site Catalysts. J Phys Chem Lett 2016; 7:3866-3872. [PMID: 27631665 DOI: 10.1021/acs.jpclett.6b01623] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Potassium deposition on TiO2(110) results in reduction of the substrate and formation of loosely bound potassium species that can move easily on the oxide surface to promote catalytic activity. The results of density functional calculations predict a large adsorption energy (∼3.2 eV) with a small barrier (∼0.25 eV) for diffusion on the oxide surface. In scanning tunneling microscopy images, the adsorbed alkali atoms lose their mobility when in contact with surface OH groups. Furthermore, K adatoms facilitate the dissociation of water on the titania surface. The K-(OH) species generated are good sites for the binding of gold clusters on the TiO2(110) surface, producing Au/K/TiO2(110) systems with high activity for the water-gas shift.
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Affiliation(s)
- David C Grinter
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Elena R Remesal
- Departamento de Química Física, Universidad de Sevilla , 41012 Sevilla, Spain
| | - Si Luo
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States
- Department of Chemistry, State University of New York (SUNY) at Stony Brook , Stony Brook, New York 11794, United States
| | - Jaime Evans
- Facultad de Ciencias, Universidad Central de Venezuela , Caracas 1020 A, Venezuela
| | - Sanjaya D Senanayake
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Dario J Stacchiola
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Jesus Graciani
- Departamento de Química Física, Universidad de Sevilla , 41012 Sevilla, Spain
| | | | - José A Rodriguez
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973, United States
- Department of Chemistry, State University of New York (SUNY) at Stony Brook , Stony Brook, New York 11794, United States
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10
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Vasseur G, Abadia M, Miccio LA, Brede J, Garcia-Lekue A, de Oteyza DG, Rogero C, Lobo-Checa J, Ortega JE. Π Band Dispersion along Conjugated Organic Nanowires Synthesized on a Metal Oxide Semiconductor. J Am Chem Soc 2016; 138:5685-92. [PMID: 27115554 PMCID: PMC4858753 DOI: 10.1021/jacs.6b02151] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
![]()
Surface-confined dehalogenation reactions
are versatile bottom-up
approaches for the synthesis of carbon-based nanostructures with predefined
chemical properties. However, for devices generally requiring low-conductivity
substrates, potential applications are so far severely hampered by
the necessity of a metallic surface to catalyze the reactions. In
this work we report the synthesis of ordered arrays of poly(p-phenylene) chains on the surface of semiconducting TiO2(110) via a dehalogenative homocoupling of 4,4″-dibromoterphenyl
precursors. The supramolecular phase is clearly distinguished from
the polymeric one using low-energy electron diffraction and scanning
tunneling microscopy as the substrate temperature used for deposition
is varied. X-ray photoelectron spectroscopy of C 1s and Br 3d core
levels traces the temperature of the onset of dehalogenation to around
475 K. Moreover, angle-resolved photoemission spectroscopy and tight-binding
calculations identify a highly dispersive band characteristic of a
substantial overlap between the precursor’s π states
along the polymer, considered as the fingerprint of a successful polymerization.
Thus, these results establish the first spectroscopic evidence that
atomically precise carbon-based nanostructures can readily be synthesized
on top of a transition-metal oxide surface, opening the prospect for
the bottom-up production of novel molecule–semiconductor devices.
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Affiliation(s)
- Guillaume Vasseur
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain
| | - Mikel Abadia
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain
| | - Luis A Miccio
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain
| | - Jens Brede
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science , 48011 Bilbao, Spain
| | - Dimas G de Oteyza
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science , 48011 Bilbao, Spain
| | - Celia Rogero
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain
| | - Jorge Lobo-Checa
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza , 50009 Zaragoza, Spain.,Departamento de Física de la Materia Condensada, Universidad de Zaragoza , 50009 Zaragoza, Spain
| | - J Enrique Ortega
- Centro de Física de Materiales (Consejo Superior de Investigaciones Científicas (CSIC)/Universidad del País Vasco (UPV)-Euskal Herriko Unibertsitatea (EHU)-Materials Physics Center (MPC) , Paseo Manuel Lardizabal 5, 20018 San Sebastián, Spain.,Donostia International Physics Center (DIPC) , Paseo Manuel Lardizabal 4, 20018 San Sebastián, Spain.,Departamento Física Aplicada I, Universidad del País Vasco , 20018 San Sebastián, Spain
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11
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González C, Abad E, Dappe YJ, Cuevas JC. Theoretical study of carbon-based tips for scanning tunnelling microscopy. NANOTECHNOLOGY 2016; 27:105201. [PMID: 26861537 DOI: 10.1088/0957-4484/27/10/105201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.
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Affiliation(s)
- C González
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette Cedex, France. Departamento de electrónica y Tecnología de Computadores, Universidad de Granada, Fuente Nueva & CITIC, Aynadamar E-18071 Granada, Spain
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12
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Influence of support morphology on the bonding of molecules to nanoparticles. Proc Natl Acad Sci U S A 2015; 112:7903-8. [PMID: 26080433 DOI: 10.1073/pnas.1506939112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Supported metal nanoparticles form the basis of heterogeneous catalysts. Above a certain nanoparticle size, it is generally assumed that adsorbates bond in an identical fashion as on a semiinfinite crystal. This assumption has allowed the database on metal single crystals accumulated over the past 40 years to be used to model heterogeneous catalysts. Using a surface science approach to CO adsorption on supported Pd nanoparticles, we show that this assumption may be flawed. Near-edge X-ray absorption fine structure measurements, isolated to one nanoparticle, show that CO bonds upright on the nanoparticle top facets as expected from single-crystal data. However, the CO lateral registry differs from the single crystal. Our calculations indicate that this is caused by the strain on the nanoparticle, induced by carpet growth across the substrate step edges. This strain also weakens the CO-metal bond, which will reduce the energy barrier for catalytic reactions, including CO oxidation.
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13
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Pang CL, Yurtsever A, Onoda J, Sugimoto Y, Thornton G. (2 n × 1) Reconstructions of TiO 2(011) Revealed by Noncontact Atomic Force Microscopy and Scanning Tunneling Microscopy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2014; 118:23168-23174. [PMID: 25309642 PMCID: PMC4191060 DOI: 10.1021/jp507422s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/02/2014] [Indexed: 06/04/2023]
Abstract
We have used noncontact atomic force microscopy (NC-AFM) and scanning tunneling microscopy (STM) to study the rutile TiO2(011) surface. A series of (2n × 1) reconstructions were observed, including two types of (4 × 1) reconstruction. High-resolution NC-AFM and STM images indicate that the (4 × 1)-α phase has the same structural elements as the more widely reported (2 × 1) reconstruction. An array of analogous higher-order (2n × 1) reconstructions were also observed where n = 3-5. On the other hand, the (4 × 1)-β reconstruction seems to be a unique structure without higher-order analogues. A model is proposed for this structure that is also based on the (2 × 1) reconstruction but with additional microfacets of {111} character.
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Affiliation(s)
- Chi Lun Pang
- Department
of Chemistry and London Centre for Nanotechnology, University College London, London WC1H 0AJ, United Kingdom
| | - Ayhan Yurtsever
- Graduate
School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan
- Institute
of Scientific and Industrial Research, Osaka
University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Jo Onoda
- Graduate
School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan
| | - Yoshiaki Sugimoto
- Graduate
School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan
| | - Geoff Thornton
- Department
of Chemistry and London Centre for Nanotechnology, University College London, London WC1H 0AJ, United Kingdom
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14
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Mönig H, Todorović M, Baykara MZ, Schwendemann TC, Rodrigo L, Altman EI, Pérez R, Schwarz UD. Understanding scanning tunneling microscopy contrast mechanisms on metal oxides: a case study. ACS NANO 2013; 7:10233-10244. [PMID: 24111487 DOI: 10.1021/nn4045358] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A comprehensive analysis of contrast formation mechanisms in scanning tunneling microscopy (STM) experiments on a metal oxide surface is presented with the oxygen-induced (2√2×√2)R45° missing row reconstruction of the Cu(100) surface as a model system. Density functional theory and electronic transport calculations were combined to simulate the STM imaging behavior of pure and oxygen-contaminated metal tips with structurally and chemically different apexes while systematically varying bias voltage and tip-sample distance. The resulting multiparameter database of computed images was used to conduct an extensive comparison with experimental data. Excellent agreement was attained for a large number of cases, suggesting that the assumed model tips reproduce most of the commonly encountered contrast-determining effects. Specifically, we find that depending on the bias voltage polarity, copper-terminated tips allow selective imaging of two structurally distinct surface Cu sites, while oxygen-terminated tips show complex contrasts with pronounced asymmetry and tip-sample distance dependence. Considering the structural and chemical stability of the tips reveals that the copper-terminated apexes tend to react with surface oxygen at small tip-sample distances. In contrast, oxygen-terminated tips are considerably more stable, allowing exclusive surface oxygen imaging at small tip-sample distances. Our results provide a conclusive understanding of fundamental STM imaging mechanisms, thereby providing guidelines for experimentalists to achieve chemically selective imaging by properly selecting imaging parameters.
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Affiliation(s)
- Harry Mönig
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster , Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany
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15
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Sánchez-Sánchez C, Martínez JI, Lanzilotto V, Biddau G, Gómez-Lor B, Pérez R, Floreano L, López MF, Martín-Gago JÁ. Chemistry and temperature-assisted dehydrogenation of C60H30 molecules on TiO2(110) surfaces. NANOSCALE 2013; 5:11058-11065. [PMID: 24071968 DOI: 10.1039/c3nr03706a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited, under ultra-high vacuum, a submonolayer coverage of C60H30 and studied, by a combination of experimental techniques (STM, XPS and NEXAFS) and theoretical methods, the different chemical on-surface interaction stages induced by the increasing temperature. We show that room temperature adsorbed molecules exhibit a weak interaction and freely diffuse on the surface, as previously reported for other aromatics. Nevertheless, a slight annealing induces a transition from this (meta)stable configuration into chemisorbed molecules. This adsorbate-surface interaction deforms the C60H30 molecular structure and quenches surface diffusion. Higher annealing temperatures lead to partial dehydrogenation, in which the molecule loses some of the hydrogen atoms and LUMO levels spread in the gap inducing a net total energy gain. Further annealing, up to around 750 K, leads to complete dehydrogenation. At these temperatures the fully dehydrogenated molecules link between them in a bottom-up coupling, forming nanodomes or fullerene-like monodisperse species readily on the dielectric surface. This work opens the door to the use of on-surface chemistry to generate new bottom-up tailored structures directly on high-K dielectric surfaces.
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Affiliation(s)
- Carlos Sánchez-Sánchez
- Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain.
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16
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Vollnhals F, Woolcot T, Walz MM, Seiler S, Steinrück HP, Thornton G, Marbach H. Electron Beam-Induced Writing of Nanoscale Iron Wires on a Functional Metal Oxide. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2013; 117:17674-17679. [PMID: 24159366 PMCID: PMC3805331 DOI: 10.1021/jp405640a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/05/2013] [Indexed: 05/06/2023]
Abstract
Electron beam-induced surface activation (EBISA) has been used to grow wires of iron on rutile TiO2(110)-(1 × 1) in ultrahigh vacuum. The wires have a width down to ∼20 nm and hence have potential utility as interconnects on this dielectric substrate. Wire formation was achieved using an electron beam from a scanning electron microscope to activate the surface, which was subsequently exposed to Fe(CO)5. On the basis of scanning tunneling microscopy and Auger electron spectroscopy measurements, the activation mechanism involves electron beam-induced surface reduction and restructuring.
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Affiliation(s)
- Florian Vollnhals
- Lehrstuhl für Physikalische
Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
| | - Tom Woolcot
- London Centre for Nanotechnology
and Department of Chemistry, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
| | - Marie-Madeleine Walz
- Lehrstuhl für Physikalische
Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
| | - Steffen Seiler
- Lehrstuhl für Physikalische
Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Lehrstuhl für Physikalische
Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
| | - Geoff Thornton
- London Centre for Nanotechnology
and Department of Chemistry, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- G.T.:
e-mail, ; London Centre for Nanotechnology
and Department of Chemistry, University
College London, 17-19 Gordon Street, London WC1H 0AH, U.K. H.M.: e-mail, ; Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
| | - Hubertus Marbach
- Lehrstuhl für Physikalische
Chemie II and Interdisciplinary Center for Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
- G.T.:
e-mail, ; London Centre for Nanotechnology
and Department of Chemistry, University
College London, 17-19 Gordon Street, London WC1H 0AH, U.K. H.M.: e-mail, ; Lehrstuhl für Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstraße
3, D-91058 Erlangen, Germany
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17
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Pang CL, Lindsay R, Thornton G. Structure of clean and adsorbate-covered single-crystal rutile TiO2 surfaces. Chem Rev 2013; 113:3887-948. [PMID: 23676004 DOI: 10.1021/cr300409r] [Citation(s) in RCA: 264] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Chi Lun Pang
- London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom
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18
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Woolcot T, Teobaldi G, Pang CL, Beglitis NS, Fisher AJ, Hofer WA, Thornton G. Scanning tunneling microscopy contrast mechanisms for TiO2. PHYSICAL REVIEW LETTERS 2012; 109:156105. [PMID: 23102341 DOI: 10.1103/physrevlett.109.156105] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 08/26/2012] [Indexed: 05/20/2023]
Abstract
Controlled dual mode scanning tunneling microscopy (STM) experiments and first-principles simulations show that the tunneling conditions can significantly alter the positive-bias topographic contrast of geometrically corrugated titania surfaces such as rutile TiO2(011)-(2×1). Depending on the tip-surface distance, two different contrasts can be reversibly imaged. STM simulations which either include or neglect the tip-electronic structure, carried out at three density functional theory levels of increasing accuracy, allow assignment of both contrasts on the basis of the TiO2(011)-(2×1) structure proposed by Torrelles et al. [Phys. Rev. Lett. 101, 185501 (2008)]. Finally, the mechanisms of contrast formation are elucidated in terms of the subtle balance between the surface geometry and the different vacuum decay lengths of the topmost Ti(3d) and O(2p) states probed by the STM-tip apex.
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Affiliation(s)
- T Woolcot
- London Centre for Nanotechnology, London, United Kingdom
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Sanchez-Sanchez C, Lanzilotto V, Gonzalez C, Verdini A, de Andres PL, Floreano L, Lopez MF, Martin-Gago JA. Weakly Interacting Molecular Layer of Spinning C60Molecules on TiO2(110) Surfaces. Chemistry 2012; 18:7382-7. [DOI: 10.1002/chem.201200627] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Indexed: 11/11/2022]
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