Fabrication of a large-area, flexible micro-pyramid PET film SERS substrate and its application in the detection of dye in herbal tea

A simple method, based on a roll-to-roll ultraviolet micro-pyramid imprinting technique and a nanoparticle self-assembling process in aqueous solution, to fabricate a large-area, flexible surface-enhanced Raman scattering (SERS) polyethylene glycol terephthalate substrate is proposed. The SERS substrate is demonstrated to be of high sensitivity. The detection concentration of Rhodamine 6G (R6G) measured by a portable Raman spectrometer is down to 10−9 mol l−1. The relative standard deviation values of different spots and different substrates are less than 13%. In addition, the feasibility for rapid detection of dye in herbal tea based on this SERS substrate and a portable Raman spectrometer is investigated. Three industrial dyes are employed to simulate the dyeing process. It is presented that R6G of 4.8\times {{10}^{-7}} g ml−1, malachite green of 10−6 g ml−1 and Auramine O of 10−6 g ml−1 in herbal tea could be detected rapidly. The experimental results imply that this method could be potentially applied in the field of dyed herbal tea detection.