Study of Molecular Trapping by Gold Nanofinger Arrays on Surface-Enhanced Raman Substrates
Kim, Ansoon; Ou, Fung Suong; Ohlberg, Douglas A.A.; Hu, Min; Williams, R. Stanley; Li, Zhiyong
Keyword(s): SERS, XPS, molecule trapping, gold finger, nanoimprint lighography
Abstract: The binding of trans-1,2-bis(4-pyridyl)-ethylene (BPE) molecules on substrates arrayed with gold nanofingers has been studied by surface enhanced Raman spectroscopy (SERS) and angle-resolved x-ray photoelectron spectroscopy (AR-XPS). Based on the SERS and XPS results, BPE molecules are found to interact with the gold nanofingers through the lone pair electrons of pyridyl nitrogens, not through delocalized π electrons. Furthermore, by comparing the AR-XPS spectra of finger arrays pre-closed before exposure to BPE with the spectra of arrays that closed after exposure to BPE, we observed at decreasing take- off angles, for which the surface sensitivity is enhanced, an increasing component of the nitrogen photoelectron peaks in the latter case which was associated with pyridyl nitrogen atoms residing on bridging sites. These results demonstrate that BPE molecules were trapped between the neighboring gold finger tips during the finger closing process. This resulted in a substantial increase in the SERS signal intensity since the self-limiting sub-nm gap between the fingertips is Raman hot spot.
Additional Publication Information: To be presented at Journal of the American Chemical Society
External Posting Date: January 21, 2011 [Fulltext]. Approved for External Publication
Internal Posting Date: January 21, 2011 [Fulltext]