Surface-Enhanced Raman Scattering and Fluorescence on Gold Nanogratings

Abstract

Surface-enhanced Raman scattering (SERS) spectroscopy is a sensitive sensing technique. It is desirable to have an easy method to produce SERS-active substrate with reproducible and robust signals. We propose a simple method to fabricate SERS-active substrates with high structural homogeneity and signal reproducibility using electron beam (E-beam) lithography without the problematic photoresist (PR) lift-off process. The substrate was fabricated by using E-beam to define nanograting patterns on the photoresist and subsequently coat a layer of gold thin film on top of it. Efficient and stable SERS signals were observed on the substrates. In order to investigate the enhancement mechanism, we compared the signals from this substrate with those with photoresist lifted-off, which are essentially discontinuous gold stripes. While both structures showed significant grating-period-dependent fluorescence enhancement, no SERS signal was observed on the photoresist lifted-off gratings. Only transverse magnetic (TM)-polarized excitation exhibited strong enhancement, which revealed its plasmonic attribution. The fluorescence enhancement showed distinct periodic dependence for the two structures, which is due to the different enhancement mechanism. We demonstrate using this substrate for specific protein binding detection. Similar periodicity dependence was observed. Detailed theoretical and experimental studies were performed to investigate the observed phenomena. We conclude that the excitation of surface plasmon polaritons on the continuous gold thin film is essential for the stable and efficient SERS effects.

Rapid Determination of the ‘Legal Highs’ 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy

“…In comparison, these low concentrations may not be detected using non-SERS Raman due to a decrease in sensitivity, and therefore a loss in peak resolution compared to SERS. The possibility to identify and quantify low concentrations of the target drugs gives the technique a potential use for testing both seizure samples and biological matrices [ 59 ] or even in instances where the fluorescence overwhelms the Raman signals [ 60 ]. Furthermore, in situ SERS substrate activation provides some benefits to overcoming a possible time-dependent decrease of the surface and plasmonic properties, which could affect the reproducibility and reliability of the measurements [ 29 ].…”

A Nanoplasmonic-Based Biosensing Approach for Wide-Range and Highly Sensitive Detection of Chemicals

“…In particular, in [39] the PMMA substrate has been considered a transparent substrate instead of a waveguide. Moreover, a similar nanostructure has also demonstrated an excellent solution to realize Surface-enhanced Raman scattering (SERS) active substrates [40].…”

Selectively enhanced Raman/fluorescence spectra in photonic–plasmonic hybrid structures

“…Some groups have recently studied this issue in different pure plasmonic systems. [38][39][40][41][42][43] However, to the best of our knowledge, this issue has been rarely studied in the optoplasmonic system.…”