Charge Transfer Enhancement in the SERS of a Single Molecule

We measured the surface-enhanced Raman scattering (SERS) of individual gold nanoparticle-4-aminobenzenethiol (ABT)-gold film junctions to investigate the charge-transfer (CT) enhancement of the SERS signals. Despite the mild electromagnetic field enhancement (∼105) and high surface density of the AB...

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Bibliographic Details
Published in:Nano letters 2010-10, Vol.10 (10), p.4040-4048
Main Authors: Park, Won-Hwa, Kim, Zee Hwan
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties
Materials science
Nanocrystalline materials
Nanoscale materials and structures: fabrication and characterization
Physics
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
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Summary:We measured the surface-enhanced Raman scattering (SERS) of individual gold nanoparticle-4-aminobenzenethiol (ABT)-gold film junctions to investigate the charge-transfer (CT) enhancement of the SERS signals. Despite the mild electromagnetic field enhancement (∼105) and high surface density of the ABT-molecules (∼240 molecules/hotspot) at the junctions, we observed the clear spectral and temporal signatures of CT-enhanced single-molecule SERS (SM-SERS). The result reveals that only a small fraction of the molecules at the junction has a significant CT-enhancement of 101∼103, whereas the rest of the molecules are nearly CT-inactive. Furthermore, the result also proves that overall (charge-transfer and electromagnetic) enhancement of 106∼108 is sufficient to observe the SM-SERS of an electronically off-resonant molecule, which disproves the widespread belief that a minimum enhancement of ∼1014 is required for SM-SERS.
ISSN:1530-6984
1530-6992
DOI:10.1021/nl102026p