Abstract
Surface-Enhanced Raman Spectroscopy (SERS) allows for the highly specific detection of molecules by enhancing the inherently weak Raman signals near the surface of plasmonic nanostructures. A variety of plasmonic nanostructures have been developed for SERS signal excitation and collection in a conventional free-space microscope, among which the gold nanodomes offer one of the highest SERS enhancements. Nanophotonic waveguides have recently emerged as an alternative to the conventional Raman microscope as they can be used to efficiently excite and collect Raman signals. Integration of plasmonic structures on nanophotonic waveguides enables reproducible waveguide-based excitation and collection of SERS spectra, such as in nanoplasmonic slot waveguides. In this paper, we compare the SERS performance of gold nanodomes, in which the signal is excited and collected in free space, and waveguide-based nanoplasmonic slot waveguide. We evaluate the SERS signal enhancement and the SERS background of the different SERS platforms using a monolayer of nitrothiophenol. We show that the nanoplasmonic slot waveguide approaches the gold nanodomes in terms of the signal-to-background ratio. We additionally demonstrate the first-time detection of a peptide monolayer on a waveguide-based SERS platform, paving the way towards the SERS monitoring of biologically relevant molecules on an integrated lab-on-a-chip platform.
Highlights
Raman spectroscopy enables for the highly specific detection of molecules by probing their vibrational states
The fabrication process based on nanosphere lithography is implemented in a mass scale production, making gold nanodomes interesting for industrial applications
We evaluated the SERS performance of gold nanodomes in which the signal is excited and collected in free space and in waveguide-based nanoplasmonic slot waveguides
Summary
Raman spectroscopy enables for the highly specific detection of molecules by probing their vibrational states A variety of SERS substrates has been developed using top-town fabrication techniques such as nanosphere lithography [21,22,23,24], and deep-UV [11] and electron beam lithography [25,26]. These techniques enable precise control of the shape and position of the nanostructures, which allows more tunable and reproducible SERS enhancements [20]. Their fabrication is simple and scalable, while ensuring better control of the hotspot size and enhancement factor as compared to colloidal approaches
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