Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2

Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO2. The Raman signals of p-NTP and m-NTP that were chem...

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Main Authors: Teguh, Jefri S., Liu, Fang, Xing, Bengang, Yeow, Edwin Kok Lee
Other Authors: School of Physical and Mathematical Sciences
Format: Article
Language:English
Published: 2013
Online Access:https://hdl.handle.net/10356/96166
http://hdl.handle.net/10220/12953
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-961662020-03-07T12:37:10Z Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2 Teguh, Jefri S. Liu, Fang Xing, Bengang Yeow, Edwin Kok Lee School of Physical and Mathematical Sciences Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO2. The Raman signals of p-NTP and m-NTP that were chemisorbed onto TiO2 were significantly enhanced with respect to their corresponding neat compounds. In particular, an enhancement factor (EF) of 102–103 was observed for both p-NTP and m-NTP, with m-NTP displaying a larger EF compared to p-NTP. The Raman signal of o-NTP on TiO2 was not detectable, owing to interference from fluorescence emissions. A molecule-to-TiO2 charge-transfer mechanism was responsible for the enhanced Raman signals observed in p-NTP and m-NTP. This transfer was due to a strong coupling between the adsorbate and the metal oxide, which led to an optically driven CT transition from the HOMO of NTP into the conduction band of TiO2. Based on the mesomeric effect, the NO2 group para to the thiol had a stronger electron-withdrawing ability than the NO2 group at the meta position. A less-efficient CT transition from p-NTP to TiO2 in the surface complex resulted in a weaker Raman-signal enhancement for p-NTP compared to m-NTP. The DFT calculation determined that the HOMO and the LUMO of NTP bound to TiO2 were located entirely on the adsorbate and the semiconductor, respectively, thereby supporting the experimental findings that a molecule-to-TiO2 mechanism was the driving force behind the observed SERS effect. 2013-08-02T07:40:12Z 2019-12-06T19:26:30Z 2013-08-02T07:40:12Z 2019-12-06T19:26:30Z 2012 2012 Journal Article Teguh, J. S., Liu, F., Xing, B.,& Yeow, E. K. L. (2012). Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol Isomers Chemisorbed on TiO2. Chemistry - An Asian Journal, 7(5), 975-981. 1861-4728 https://hdl.handle.net/10356/96166 http://hdl.handle.net/10220/12953 10.1002/asia.201100934 en Chemistry - an Asian journal
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
description Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO2. The Raman signals of p-NTP and m-NTP that were chemisorbed onto TiO2 were significantly enhanced with respect to their corresponding neat compounds. In particular, an enhancement factor (EF) of 102–103 was observed for both p-NTP and m-NTP, with m-NTP displaying a larger EF compared to p-NTP. The Raman signal of o-NTP on TiO2 was not detectable, owing to interference from fluorescence emissions. A molecule-to-TiO2 charge-transfer mechanism was responsible for the enhanced Raman signals observed in p-NTP and m-NTP. This transfer was due to a strong coupling between the adsorbate and the metal oxide, which led to an optically driven CT transition from the HOMO of NTP into the conduction band of TiO2. Based on the mesomeric effect, the NO2 group para to the thiol had a stronger electron-withdrawing ability than the NO2 group at the meta position. A less-efficient CT transition from p-NTP to TiO2 in the surface complex resulted in a weaker Raman-signal enhancement for p-NTP compared to m-NTP. The DFT calculation determined that the HOMO and the LUMO of NTP bound to TiO2 were located entirely on the adsorbate and the semiconductor, respectively, thereby supporting the experimental findings that a molecule-to-TiO2 mechanism was the driving force behind the observed SERS effect.
author2 School of Physical and Mathematical Sciences
author_facet School of Physical and Mathematical Sciences
Teguh, Jefri S.
Liu, Fang
Xing, Bengang
Yeow, Edwin Kok Lee
format Article
author Teguh, Jefri S.
Liu, Fang
Xing, Bengang
Yeow, Edwin Kok Lee
spellingShingle Teguh, Jefri S.
Liu, Fang
Xing, Bengang
Yeow, Edwin Kok Lee
Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
author_sort Teguh, Jefri S.
title Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
title_short Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
title_full Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
title_fullStr Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
title_full_unstemmed Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol isomers chemisorbed on TiO2
title_sort surface-enhanced raman scattering (sers) of nitrothiophenol isomers chemisorbed on tio2
publishDate 2013
url https://hdl.handle.net/10356/96166
http://hdl.handle.net/10220/12953
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