Rational engineering of highly sensitive SERS substrate based on nanocone structures

Abstract

At last meeting, we reported a new type of surface-enhanced Raman Spectroscopy (SERS) substrates based on metal (Au or Ag) coated Si nanocones fabricated by a Bosch etching process. The substrate showed reliable SERS performance with an analytical enhancement factor greater than 6 × 10⁷ for trans-1,2-bis(4-pyridyl)-ethylene (BPE) molecules. However, the process is limited to single crystalline silicon material, also silicon can absorb both incident and scattered light, making it difficult to investigate the SERS enhancement mechanism. To further improve the sensitivity of the SERS substrate, we have recently developed a process to duplicate the Si nanocones by a cross-linked polymer using 3-D nanoimprint lithography (NIL). The SERS substrate made by NIL demonstrated better enhancement factors for both 633 nm excitation and 785 nm excitation with analytical enhancement factors of over 10¹¹ demonstrated. We will report the rational engineering of the nanocone based SERS substrate and the fundamental understanding of the enhancement mechanism.