Highly active Au NP microarray films for direct SERS detection

The fabrication of flexible surface-enhanced Raman scattering (SERS) substrates with high sensitivity and signal consistency in a simple and low-cost way have been a crucial and urgent challenge. In this study, we demonstrated a flexible transparent three-dimensional (3D) ordered micro-hemisphere (MHS) array PDMS film with self-assembled Au nanoparticles (NPs) (an Au NP-MHS array film) as a surface-enhanced Raman scattering (SERS) platform for the in situ detection of pesticides in food. According to the finite difference time domain (FDTD) simulation results, the Au NP-MHS array film possesses high-density and ordered "hot spots" to enhance the electromagnetic field (EMF), so that the sensitivity and signal consistency are effectively improved. The optimized Au NP-MHS array film exhibits fascinating SERS sensitivity, with a limitation of crystal violet (CV) reaching 10^-12 M as well as excellent consistency (RSD = 4.89% at 10^-8 M). For in situ pesticide detection in fruits, this flexible film was pasted on the surfaces of tomatoes. The carbendazol and parathion were directly detected, and distinctly identified even at a low concentration (10^-8 M). The flexible Au NP-MHS array film could be a potential candidate for the SERS substrate applied in the rapid and true inspection.