Tip-enhanced Raman spectroscopy of 4,4′-bipyridine and 4,4′-bipyridine N,N'-dioxide adsorbed on gold thin films
A tip-enhanced Raman spectroscopy (TERS) set-up added on a scanning tunneling microscope (STM) was constructed and was used to study the molecular arrangement of 4,4′-bipyridine (4,4′-BiPy) and 4,4′-bipyridine N,N'-dioxide (4,4′-BiPyO2) adsorbed on Au(111). Over a monolayer of 4,4′-BiPy, in the...
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Published in | Surface science Vol. 617; pp. 1 - 9 |
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Main Authors | , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Kidlington
Elsevier B.V
01.11.2013
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | A tip-enhanced Raman spectroscopy (TERS) set-up added on a scanning tunneling microscope (STM) was constructed and was used to study the molecular arrangement of 4,4′-bipyridine (4,4′-BiPy) and 4,4′-bipyridine N,N'-dioxide (4,4′-BiPyO2) adsorbed on Au(111). Over a monolayer of 4,4′-BiPy, in the ambient atmosphere, intense TERS signals were recorded, involving AuN stretching vibration at 185cm−1. At the early stage of 4,4′-BiPy adsorption, the AuN stretching signal was not detected. By the aid of the theoretical calculations of the Raman scattering intensities for each vibrational normal mode, a standing-up, tilted orientation at monolayer coverage and a vertical orientation with the longitudinal molecular axis parallel to the surface at low surface coverage was concluded. Adsorption of 4,4′-BiPyO2 on Au(111) resulted in formation of a (6×9) adlattice. Moderately intense TERS signals were observed, containing the NO stretching modes and the in-plane ring vibrational modes. Neither AuO nor AuN stretching modes were observed. 4,4′-BiPyO2 was laid with the longitudinal axis parallel to the surface, and the molecular plane vertical to the surface. These results demonstrate that STM-TERS is an effective method for simultaneous imaging and vibrational analysis, facilitating identification of the adsorbed layers with the nanometer-scale spatial resolution and monolayer sensitivity.
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•STM of 4,4’-bipyridine and 4,4’-bipyridine N,N’-dioxide adlayers on Au(111).•Nanoimaging combined with vibrational analysis.•The Au-N stretching indicates chemisorption of 4,4’-bipyridine on Au(111).•Molecular orientation is deduced from calculation of Raman tensor elements. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0039-6028 1879-2758 |
DOI: | 10.1016/j.susc.2013.08.010 |