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Nano Research 2014, 7(9): 1271-1279 https://doi.org/10.1007/s12274-014-0490-3
Research Article | Issue | Published: 17 July 2014

Direct measurement of the Raman enhancement factor of rhodamine 6G on graphene under resonant excitation

Show Author's Information Shibin Deng1,  Weigao Xu1,  Jinying Wang1,  Xi Ling2,  Juanxia Wu1,  Liming Xie3,  Jing Kong2,  Mildred S. Dresselhaus2,4,  Jin Zhang1( )
Center for NanochemistryBeijing National Laboratory for Molecular SciencesKey Laboratory for the Physics and Chemistry of NanodevicesState Key Laboratory for Structural Chemistry of Unstable and Stable SpeciesCollege of Chemistry and Molecular Engineering, Peking UniversityBeijing100871China
Department of Electrical Engineering and Computer ScienceMassachusetts Institute of TechnologyCambridge, Massachusetts02139USA
Key Laboratory of Standardization and Measurement for Nanotechnology of Chinese Academy of SciencesNational Center for Nanoscience and TechnologyBeijing100190China
Department of PhysicsMassachusetts Institute of TechnologyCambridge, Massachusetts02139USA
Keywords:
graphene, Raman enhancement, rhodamine 6G, polarization-difference resonance Raman spectroscopy, optical contrast spectroscopy
Cite this article:
Deng S, Xu W, Wang J, et al. Direct measurement of the Raman enhancement factor of rhodamine 6G on graphene under resonant excitation. Nano Research, 2014, 7(9): 1271-1279. https://doi.org/10.1007/s12274-014-0490-3
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Abstract Full text Electronic supplementary material About this article

Graphene substrates have recently been found to generate Raman enhancement. Systematic studies using different Raman probes have been implemented, but one of the most commonly used Raman probes, rhodamine 6G (R6G), has yielded controversial results for the enhancement effect on graphene. Indeed, the Raman enhancement factor of R6G induced by graphene has never been measured directly under resonant excitation because of the presence of intense fluorescence backgrounds. In this study, a polarization-difference technique is used to suppress the fluorescence background by subtracting two spectra collected using different excitation laser polarizations. As a result, enhancement factors are obtained ranging between 1.7 and 5.6 for the four Raman modes of R6G at 611, 1, 183, 1, 361, and 1, 647 cm-1 under resonant excitation by a 514.5 nm laser. By comparing these results with the results obtained under non-resonant excitation (632.8 nm) and pre-resonant excitation (593 nm), the enhancement can be attributed to static chemical enhancement (CHEM) and tuning of the molecular resonance. Density functional theory simulations reveal that the orbital energies and densities for R6G are modified by graphene dots.


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Electronic supplementary material
About this article

Direct measurement of the Raman enhancement factor of rhodamine 6G on graphene under resonant excitation

Show Author's information Shibin Deng1, Weigao Xu1, Jinying Wang1, Xi Ling2, Juanxia Wu1, Liming Xie3, Jing Kong2, Mildred S. Dresselhaus2,4, Jin Zhang1( )
Center for NanochemistryBeijing National Laboratory for Molecular SciencesKey Laboratory for the Physics and Chemistry of NanodevicesState Key Laboratory for Structural Chemistry of Unstable and Stable SpeciesCollege of Chemistry and Molecular Engineering, Peking UniversityBeijing100871China
Department of Electrical Engineering and Computer ScienceMassachusetts Institute of TechnologyCambridge, Massachusetts02139USA
Key Laboratory of Standardization and Measurement for Nanotechnology of Chinese Academy of SciencesNational Center for Nanoscience and TechnologyBeijing100190China
Department of PhysicsMassachusetts Institute of TechnologyCambridge, Massachusetts02139USA

Abstract

Graphene substrates have recently been found to generate Raman enhancement. Systematic studies using different Raman probes have been implemented, but one of the most commonly used Raman probes, rhodamine 6G (R6G), has yielded controversial results for the enhancement effect on graphene. Indeed, the Raman enhancement factor of R6G induced by graphene has never been measured directly under resonant excitation because of the presence of intense fluorescence backgrounds. In this study, a polarization-difference technique is used to suppress the fluorescence background by subtracting two spectra collected using different excitation laser polarizations. As a result, enhancement factors are obtained ranging between 1.7 and 5.6 for the four Raman modes of R6G at 611, 1, 183, 1, 361, and 1, 647 cm-1 under resonant excitation by a 514.5 nm laser. By comparing these results with the results obtained under non-resonant excitation (632.8 nm) and pre-resonant excitation (593 nm), the enhancement can be attributed to static chemical enhancement (CHEM) and tuning of the molecular resonance. Density functional theory simulations reveal that the orbital energies and densities for R6G are modified by graphene dots.

Keywords: graphene, Raman enhancement, rhodamine 6G, polarization-difference resonance Raman spectroscopy, optical contrast spectroscopy

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Publication history
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Acknowledgements

Publication history

Received: 03 February 2014
Revised: 28 April 2014
Accepted: 02 May 2014
Published: 17 July 2014
Issue date: September 2014

Copyright

© Tsinghua University Press and Springer‐Verlag Berlin Heidelberg 2014

Acknowledgements

Acknowledgements

This work was supported by NSFC (Nos. 21233001, 50972001, and 21129001), MOST (Nos. 2011YQ0301240201 and 2011CB932601), and Beijing Natural Science Foundation (No. 2132056).

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