Development of a novel wrinkle-structure based SERS substrate for drug detection applications

Abstract

A novel wrinkle-structure based surface enhanced Raman spectroscopy (SERS) substrate was successfully developed for the detection of drugs such as cocaine. The SERS substrate was fabricated by depositing silver nano-particle (Ag-NP) ink, with 150 nm particle size, using gravure printing process on a flexible and stretchable thermoplastic polyurethane (TPU) substrate. The wrinkle patterned structures, or rough metallic layers, were created by applying varying strains (25%, 50%, 75% and 100%) to the TPU substrate before printing Ag-NP. The wrinkle structures increase the number and depth of hotspots on the SERS substrate thus generating larger electromagnetic fields resulting in an enhanced Raman signal intensity. The capability of the printed wrinkled SERS substrate to enhance the Raman spectra of cocaine was investigated. An enhancement factor (EF) of 4 and 6 in the intensity of the Raman signal of cocaine on the wrinkle-structured SERS substrate was observed, when compared to the Raman signal of cocaine on a non-wrinkled SERS substrate and bare TPU substrate, respectively, for analytes with similar concentrations. The results of the wrinkle-structured SERS substrate demonstrated the feasibility of the gravure printed SERS substrate to be used in drug detection applications. Keywords: Cocaine, Gravure printing, SERS, Silver nanoparticles, Thermoplastic polyurethane (TPU), Wrinkle-structure