Flexible Ag/nanocellulose fibers SERS substrate and its applications for in-situ hazardous residues detection on food

In this work, we have developed a sensitive, flexible, cost-effective Ag/Nanocellulose fibers SERS substrate (Ag@NCF substrate) which is suitable for in-situ food safety detection. NCFs build nanoporous networks as flexible templates. Ag nanoparticles time-efficiently, in-situ grow on the cross fibers, forming sensitive Ag clusters, providing a high density of 'hot-spot', further resulting in a significant enhancement of electromagnetic fields. The lowest distinguishable level of Rhodamine 6G is 10(-9) M and simplified models correspondingly reveal a high sensitivity of Ag@NCF substrate. In additions, the Ag@NCF film facilitates a simple, direct, in-situ 'paste-test' method for hazardous residue detection on actual food samples. The sensitive Ag@NCF substrates achieve ppb-level detection of pesticide and veterinary drug by a self-developed portable Raman spectrometer. The estimated LOD is low to 0.05 ppm for thiram, 0.09 ppm for thiabendazole, 0.0014 ppm for malachite green and 0.069 ppm for enrofloxacin, respectively. And hazardous residues could be directly detected on pear and fish by the Ag@NCF substrates. These results reveal that Ag@NCF substrate cooperated with portable Raman system is suitable for sensitive, in-situ, on-site pesticides and veterinary drugs detection on fruit or seafood and remains great potentials to expand to other on-site, in-situ applications.