A SERS Substrate Based on Ultrasonic Stacking of Nanopowders on Thermoplastics

ABSTRACT Surface‐enhanced Raman spectroscopy (SERS) is often considered as a versatile tool for high‐sensitive detection of low concentrations of analytes. Typically, gold or silver patterned surfaces, namely the SERS substrates, are utilized to amplify Raman signal. However, most SERS substrates require microfabrication processes based on costly infrastructures. In this paper, we propose a simple yet effective scheme for fabricating SERS substrates on thermoplastics. The process involves ultrasonically stacking nanopowders on thermoplastic substrate via a stencil. We showed that gold surfaces on polymethly methacrylate (PMMA) substrates could be fabricated by ultrasonic means in less than 10 s by using a benchtop ultrasonic welder. We investigated the effect of process parameters, namely the pressure and the vibration time, on the surface topography and SERS performance. The results show that the process is mainly controlled by the vibration time, such that at moderate vibration times (~ 5 s), uniformly rough surfaces could be repeatably achieved. Fabricated samples were tested for SERS performance using 5,5′‐ditiobis (2‐nitrobenzoic acid) (DTNB) as the Raman reporter. We showed that the substrates fabricated under 2.7 MPa pressure and 5 s vibration time yielded comparatively low relative standard deviations (RSD) of SERS intensity—6.12% for point‐to‐point variation and 6.73% for batch‐to‐batch variation—along with an enhancement factor (EF) of 1.28 × 10 5 . The performance of the SERS substrates, considering RSD and EF, indicates that the proposed fabrication method could be a promising alternative for SERS based sensing applications.