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Besharat, Z., Ghadami Yazdi, M., Wakeham, D., Johnson, M., Rutland, M. W., Göthelid, M. & Grönbeck, H. (2018). Se-C Cleavage of Hexane Selenol at Steps on Au(111). Langmuir, 34(8), 2630-2636
Open this publication in new window or tab >>Se-C Cleavage of Hexane Selenol at Steps on Au(111)
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2018 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 8, p. 2630-2636Article in journal (Refereed) Published
Abstract [en]

Selenols are considered as an alternative to thiols in self-assembled monolayers, but the Se-C bond is one limiting factor for their usefulness. In this study, we address the stability of the Se-C bond by a combined experimental and theoretical investigation of gas phase-deposited hexane selenol (CH3(CH2)(5)SeH) on Au(111) using photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory (DFT). Experimentally, we find that initial adsorption leaves atomic Se on the surface without any carbon left on the surface, whereas further adsorption generates a saturated selenolate layer. The Se 3d component from atomic Se appears at 0.85 eV lower binding energy than the selenolate-related component. DFT calculations show that the most stable structure of selenols on Au(111) is in the form of RSe-Au-SeR complexes adsorbed on the unreconstructed Au(111) surface. This is similar to thiols on Au(111). Calculated Se 3d core-level shifts between elemental Se and selenolate in this structure nicely reproduce the experimentally recorded shifts. Dissociation of RSeH and subsequent formation of RH are found to proceed with high barriers on defect-free Au(111) terraces, with the highest barrier for scissoring R-Se. However, at steps, these barriers are considerably lower, allowing for Se-C bond breaking and hexane desorption, leaving elemental Se at the surface. Hexane is the selenol to selenolate formed by replacing the Se-C bond with a H-C bond by using the hydrogen liberated from transformation.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
Ray Photoelectron-Spectroscopy, Resolution Photoemission-Spectroscopy, Core-Level Shifts, Assembled Monolayers, Gold Surfaces, Mono Layers, Adsorption, Thiol, Alkanethiols, Stability
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-225082 (URN)10.1021/acs.langmuir.7b03713 (DOI)000426614100006 ()29405715 (PubMedID)2-s2.0-85042636157 (Scopus ID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research
Note

QC 20180328

Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2018-03-28Bibliographically approved
Besharat, Z., Halldin Stenlid, J., Soldemo, M., Marks, K., Önsten, A., Johnson, M., . . . Göthelid, M. (2017). Dehydrogenation of methanol on Cu2O(100) and (111). Journal of Chemical Physics, 146(24)
Open this publication in new window or tab >>Dehydrogenation of methanol on Cu2O(100) and (111)
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24Article in journal (Refereed) Published
Abstract [en]

Adsorption and desorption of methanol on the (111) and (100) surfaces of  Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120–620 K, in combination with density functional theorycalculations and sum frequency generation spectroscopy. The bare (100) surfaceexhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this  surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surfaceoxygen.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-211786 (URN)10.1063/1.4989472 (DOI)000404302600033 ()2-s2.0-85021446807 (Scopus ID)
Note

QC 20170816

Available from: 2017-08-13 Created: 2017-08-13 Last updated: 2017-11-10Bibliographically approved
Besharat, Z., Alvarez-Asencio, R., Tian, H., Yu, S., Johnson, C. M., Gothelid, M. & Rutland, M. W. (2017). In-situ evaluation of dye adsorption on TiO2 using QCM. EPJ Photovoltaics, 8
Open this publication in new window or tab >>In-situ evaluation of dye adsorption on TiO2 using QCM
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2017 (English)In: EPJ Photovoltaics, ISSN 2105-0716, Vol. 8Article in journal (Refereed) Published
Abstract [en]

We measured the adsorption characteristics of two organic dyes; triphenylamine-cyanoacrylic acid (TPA-C) and phenoxazine (MP13), on TiO2, directly in a solution based on quartz crystal microbalance (QCM). Monitoring the adsorbed amount as a function of dye concentration and during rinsing allows determination of the equilibrium constant and distinction between chemisorbed and physisorbed dye. The measured equilibrium constants are 0.8 mM(-1) for TPA-C and 2.4 mM(-1) for MP13. X-ray photoelectron spectroscopy was used to compare dried chemisorbed layers of TPA-C prepared in solution with TPA-C layers prepared via vacuum sublimation; the two preparation methods render similar spectra except a small contribution of water residues (OH) on the solution prepared samples. Quantitative Nanomechanical Mapping Atomic Force Microscopy (QNM-AFM) shows that physisorbed TPA-C layers are easily removed by scanning the tip across the surface. Although not obvious in height images, adhesion images clearly demonstrate removal of the dye.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-248715 (URN)10.1051/epjpv/2017002 (DOI)000396159700001 ()2-s2.0-85061784497 (Scopus ID)
Note

QC 20190514

Available from: 2019-04-10 Created: 2019-04-10 Last updated: 2019-05-14Bibliographically approved
Soldemo, M., Halldin Stenlid, J., Besharat, Z., Ghadami Yazdi, M., Önsten, A., Leygraf, C., . . . Weissenrieder, J. (2016). The Surface Structure of Cu2O(100). The Journal of Physical Chemistry C, 120(8), 4373-4381
Open this publication in new window or tab >>The Surface Structure of Cu2O(100)
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 8, p. 4373-4381Article in journal (Refereed) Published
Abstract [en]

Despite the industrial importance of copper oxides, the nature of the (100) surface of Cu2O has remained poorly understood. The surface has previously been subject to several theoretical and experimental studies, but has until now not been investigated by atomically resolved microscopy or high-resolution photoelectron spectroscopy. Here we determine the atomic structure and electronic properties of Cu2O(100) by a combination of multiple experimental techniques and simulations within the framework of density functional theory (DFT). Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) characterized the three ordered surface structures found. From DFT calculations, the structures are found to be energetically ordered as (3,0;1,1), c(2 x 2), and (1 x 1) under ultrahigh vacuum conditions. Increased oxygen pressures induce the formation of an oxygen terminated (1 x 1) surface structure. The most common termination of Cu2O(100) has previously been described by a (3 root 2 x root 2)R45 degrees unit cell exhibiting a LEED pattern with several missing spots. Through atomically resolved STM, we show that this structure instead is described by the matrix (3,0;1,1). Both simulated STM images and calculated photoemission core level shifts compare favorably with the experimental results.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-184532 (URN)10.1021/acs.jpcc.5b11350 (DOI)000371562000024 ()2-s2.0-84960171601 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20160406

Available from: 2016-04-06 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
Rihtnesberg, D. B., Almqvist, S., Wang, Q., Sugunan, A., Yang, X., Toprak, M., . . . Göthelid, M. (2011). ZnO nanorods/nanoflowers and their applications. In: Proc. - Int. NanoElectronics Conf., INEC: . Paper presented at 4th IEEE International Nanoelectronics Conference, INEC 2011, 21 June 2011 through 24 June 2011, Tao-Yuan.
Open this publication in new window or tab >>ZnO nanorods/nanoflowers and their applications
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2011 (English)In: Proc. - Int. NanoElectronics Conf., INEC, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Single-crystalline zinc oxide (ZnO) nanorods (NRs) have been synthesized through a chemical bath deposition method. Their diameter is about 80 nm, and their length range from 1 μm to 7 μm can be controlled by growth time. Formation of nanoflower arrays composed of nanorods has been also achieved utilizing a standard micro-fabrication technique. Two types of ZnO nanorods devices are detailed to demonstrate their optoelectronic applications.

Series
Proceedings - International NanoElectronics Conference, INEC, ISSN 2159-3523
Keywords
nanoflowers, nanorods, UV photodetectors, ZnO, Chemical bath deposition methods, Growth time, Micro-fabrication techniques, Optoelectronic applications, Single-crystalline, ZnO nanorod, Nanoelectronics, Zinc oxide
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-150752 (URN)10.1109/INEC.2011.5991615 (DOI)2-s2.0-80053000955 (Scopus ID)9781457703799 (ISBN)
Conference
4th IEEE International Nanoelectronics Conference, INEC 2011, 21 June 2011 through 24 June 2011, Tao-Yuan
Note

QC 20140909

Available from: 2014-09-09 Created: 2014-09-09 Last updated: 2014-09-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9828-7753

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