Superhydrophobic “wash free” 3D nanoneedle array for rapid, recyclable and sensitive SERS sensing in real environment

Rapid sensitive sensing in wide fields such as food science and medical science by using Surface-enhanced Raman scattering (SERS) has been a promising technique recently. Inspired by the bionic superhydrophobic surface, we prepared a superhydrophobic Ag nanoparticles (Ag NPs) decorated Cu(OH)₂ nanoneedle array SERS substrate by a facile electrochemical method. Different with the traditional SERS detection method, molecules are detected in droplets rapidly on the substrate based on the superhydrophobicity, offering low concentration and recyclable detection. The substrate exhibits excellent Raman signal enhancement by using several probe molecules. The nanoneedle array structure offers simultaneously a 3D scaffold for Ag NPs forming unique electromagnetic field enhancement and a superhydrophobic surface for recyclable using. The recyclability in SERS detection was tested by using crystal violet and rhodamine 6G as the probe molecules alternatively, obtaining at least 6 times reutilization without any cleaning process with little fluctuation of the signal intensity. Practical application in real environment has been investigated by detecting melamine in milk and thiram in apple juice, with the detection limits approximately 0.1 ppm, far lower than the national standard. With the advantages of easy preparing, high sensitivity and recyclability, the prepared substrates are expected owing great potential in rapid detection in food safety, medical testing and environmental monitoring in the future.