Flexible, Transparent, and Free-Standing Silicon Nanowire SERS Platform for in Situ Food Inspection.

We demonstrated a flexible transparent and free-standing Si nanowire paper (SiNWP) as a surface enhanced Raman scattering (SERS) platform for in situ chemical sensing on warping surfaces with high sensitivity. The SERS activity has originated from the three-dimension interconnected nanowire network structure and electromagnetic coupling between closely separated nanowires in the SiNWP. In addition, the SERS activity can be highly improved by functionalizing the SiNWP with plasmonic Au nanoparticles. The hybrid substrate not only showed excellent reproducibility and stability of the SERS signal, but also maintained the flexibility and transparency of the pristine SiNWP. To demonstrate its potential application in food inspection, the Au nanoparticles-modified SiNWP was directly wrapped onto the lemon surface for in situ identification and detection of the pesticide residues. The results showed that the excellent SERS activity and transparency of the hybrid substrate enabled the detection of the pesticides down to 72 ng/cm(2), which was much lower than the permitted residue dose in food safety.