Lotus Seedpod Inspired SERS Substrates: A Novel Platform Consisting of 3D Sub-10 nm Annular Hot Spots for Ultrasensitive SERS Detection

摘要

A novel lotus seedpod (LSP) like array substrate with tailorable annular nanogaps is reported for surface-enhanced Raman spectroscopy (SERS). High SERS activity with excellent Raman signal reproducibility is achieved for molecular detection. Finite-different time-domain simulation suggests that sub-10 nm annular nanogaps formed in the LSP array contribute significantly to the electromagnetic field enhancement for SERS measurements. The SERS substrate presents a detection limit as low as 10~(−12) m along with a relative standard deviation as small as 4.1−8.0% in the detection of rhodamine 6G (R6G). Moreover, the linear correlation between Raman intensity and the concentration of R6G indicates the capability of the substrate for quantitative SERS analyses. As a typical example, the SERS substrate is successfully applied to detecting the α-helical structure of amyloid-β oligomers at a low concentration of 0.1 × 10~(−6) m, which will be promising for label-free detection of Alzheimer’s disease in its earliest, presymptomatic, and most treatable stages. The as-fabricated LSP array substrates therefore hold exciting potentials toward SERS-based chemical and biomedical detections.