In situ synthesis of low-cost and large-scale flexible metal nanoparticle–polymer composite films as highly sensitive SERS substrates for surface trace analysis

Surface-enhanced Raman spectroscopy (SERS) has been one of the most promising analytical tools. Despite many efforts in the design of SERS substrates, it remains a great challenge for creating a general flexible substrate that could in situ detect analytes on diverse objects. Herein, we report our attempt to address this issue by developing a facile and versatile method capable of generating silver/gold nanoparticles in situ on the surface of a cellulose acetate (CA) polymer in a simple, cheap, practical, and capping agent-free way. The as-prepared substrates exhibit excellent sensitivity, which enabled detection of Rhodamine 6G at concentrations as low as 10−12 M. Taking advantage of the excellent flexibility and optical transparency of the CA matrix, the highly SERS-active substrate was applied for in situ identification and detection of pesticide residues on fruits. The results indicated that tetramethylthiuram disulfide (TMTD) and thiabendazole (TBZ) can be clearly identified at concentrations as low as 18.05 ng cm−2 and 15.1 ng cm−2, respectively, which were much lower than the maximum permitted residue doses with respect to food safety.