Label-free, multiplexed, molecular sensing and imaging by stamping SERS

Surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique, where Raman scattering is boosted primarily by enhanced electric field due to localized surface plasmon resonance (LSPR). With advances in nanofabrication techniques, SERS has attracted great attention for label-free molecular sensing and imaging. However, the practical use of SERS has often encountered an inherent issues regarding a molecule transfer step where target molecules need to be within the close proximity of a SERS-active surface by either mixing with nanoparticles or coating onto surface-bound nanostructures. To address this issue, we have developed stamping surface-enhanced Raman spectroscopy (S-SERS) for label-free, multiplexed, molecular sensing and large-area, high-resolution molecular imaging on a flexible, non-plasmonic surface without solution-phase molecule transfer. In this technique, a polydimethylsiloxane (PDMS) thin film and nanoporous gold disk SERS substrate play the roles as molecule carrier and Raman signal enhancer, respectively. After stamping the SERS substrate onto the PDMS film, SERS measurements can be directly taken from the “sandwiched” target molecules. The performance of S-SERS is evaluated by the detection of Rhodamine 6G (R6G), urea, and its mixture with acetaminophen (APAP), in physiologically relevant concentration range, along with corresponding SERS spectroscopic maps. S-SERS features simple sample preparation, low cost, and high reproducibility, which could lead to SERS-based sensing and imaging for point-of-care and forensics applications.