A SERS tattoo for in situ, ex situ, and multiplexed detection of toxic food additives

We demonstrate a gold island film (GIF) coated tattoo paper as acid free ‘green’ fabrication of transferable plasmonic patterns for surface enhanced Raman spectroscopy (SERS) based screening of food toxins. A tattoo paper, with a water soluble release layer, was optimally sputter coated with a gold pattern which can be transferred onto any real fruit surface to enable in situ molecular detection (Thiabendazole, TBZ, used here) from the surface of the fruit (orange used here). The GIF loading and morphology is simply controlled by varying the sputtering time between 1 and 8 min. The integrated plasmonic field strength, calculated by finite difference time domain simulations, peaked for the GIF obtained with 3 min of sputtering time to match the experimental results. The SERS tattoo can also be transferred to a copper foil to enable conventional ex situ molecular detection (Di 2-ethylhexyl phthalate, DEHP, used here) in commercial sports drinks. The SERS tattoo could detect 0.1 μM (0.2 ppm) of TBZ on orange in situ, and 0.0009 vol.% DEHP in sports drink ex situ. Multiplexed SERS experiments were performed to detect specific signals of TBZ, and commercial soybean oil from their combination.