One-step fabrication of metal nanoparticles on polymer film by femtosecond LIPAA method for SERS detection

Flexible transparent SERS substrates have aroused great interest as a rapid and in situ detection method for trace chemicals. We demonstrate a one-step and environmentally friendly method to fabricate flexible fluorinated ethylene propylene (FEP) surface plasmon resonance film by femtosecond laser induced plasma assisted ablation (LIPAA) for in situ SERS detection. By tuning laser fluence, the distributions and sizes of silver and gold nanoparticles generated by femtosecond LIPAA are studied. Using a Rhodamine 6G (R6G) Raman probe with a 532 nm laser excitation, the proposed Ag NPs/FEP and Au NPs/FEP substrates show enhancement factors of 5.6 x 10(7) and 2.4 x 10(6), respectively, as compared to a bare FEP film without the metallic nanoparticles. The Raman signals show good uniformity and a linear relationship with the concentration of R6G solution. In addition, the detection limit of thiram on an apple for in situ measurement is 0.1 mg/Kg, corresponding to 7.96 ng/cm(2). The proposed SERS detection approach has great potential to pave a new way in food safety applications, such as detecting pesticides in harvested fruits.