title: Tailored surface-enhanced Raman nanopillar arrays fabricated by laser-assisted replication for biomolecular detection using organic semiconductor lasers.
abstract: Organic semiconductor distributed feedback (DFB) lasers are of interest as external or chip-integrated excitation sources in the visible spectral range for miniaturized Raman-on-chip biomolecular detection systems. However, the inherently limited excitation power of such lasers as well as oftentimes low analyte concentrations requires efficient Raman detection schemes. We present an approach using surface-enhanced Raman scattering (SERS) substrates, which has the potential to significantly improve the sensitivity of on-chip Raman detection systems. Instead of lithographically fabricated Au/Ag-coated periodic nanostructures on Si/SiO2 wafers, which can provide large SERS enhancements but are expensive and time-consuming to fabricate, we use low-cost and large-area SERS substrates made via laser-assisted nanoreplication. These substrates comprise gold-coated cyclic olefin copolymer (COC) nanopillar arrays, which show an estimated SERS enhancement factor of up to ∼ 10(7). The effect of the nanopillar diameter (60-260 nm) and interpillar spacing (10-190 nm) on the local electromagnetic field enhancement is studied by finite-difference-time-domain (FDTD) modeling. The favorable SERS detection capability of this setup is verified by using rhodamine 6G and adenosine as analytes and an organic semiconductor DFB laser with an emission wavelength of 631.4 nm as the external fiber-coupled excitation source.
authors.affiliation: Light Technology Institute (LTI) and ‡Institute of Physical Chemistry (IPC), Karlsruhe Institute of Technology , 76128 Karlsruhe, Germany.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Sergei
authors.initials: S
authors.lastname: Lebedkin
authors.forename: Heino
authors.initials: H
authors.lastname: Besser
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Pfleging
authors.forename: Stephan
authors.initials: S
authors.lastname: Prinz
authors.forename: Markus
authors.initials: M
authors.lastname: Wissmann
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Schwab
authors.forename: Irina
authors.initials: I
authors.lastname: Nazarenko
authors.forename: Markus
authors.initials: M
authors.lastname: Guttmann
authors.forename: Manfred M
authors.initials: MM
authors.lastname: Kappes
authors.forename: Uli
authors.initials: U
authors.lastname: Lemmer
mesh_terms: D000241:Adenosine / Q000032:analysis / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D054023:Lasers, Semiconductor; D036103:Nanotechnology / Q000295:instrumentation*; D009930:Organic Chemicals / Q000737:chemistry*; D012235:Rhodamines / Q000032:analysis / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000295:instrumentation*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000475:Alkenes; D009930:Organic Chemicals; D012235:Rhodamines; C026188:rhodamine 6G; D014867:Water; D012834:Silver; D006046:Gold; D000241:Adenosine
keywords: Raman spectroscopy; laser material processing; nanoimprint lithography; nanostructure fabrication; organic semiconductor distributed-feedback lasers; surface-enhanced Raman scattering