Rapid and sensitive in-situ detection of malachite green and crystal violet in aquaculture using flexible SERS substrates via instant self-assembly

Rapid, low-cost, and in-situ detection of illegal residues on aquatic product surfaces remains a significant challenge. Herein, we developed a versatile surface-enhanced Raman scattering (SERS) sensor by integrating instant interfacial self-assembled silver nanostar film onto flexible polytetrafluoroethylene filter membrane (AgNS/PTFE) for sensitive detection of malachite green (MG) and crystal violet (CV) in crayfish. The entire process, from room-temperature substrate preparation to detection completion, takes less than 20 min. The AgNS/PTFE flexible substrate not only provides excellent hydrophobicity for signal enhancement with minimal sample volumes (2 μL) but also ensures good uniformity, resulting in a homogeneous and dense distribution of SERS-active hot spots with superior anti-interference properties and mechanical durability. By simple “drop/wipe” operations and data visualization treatment, this method achieved detection limits as low as 10 pg/mL for MG and 7 pg/mL for CV, with in-situ analysis in spiked and actual crayfish samples, demonstrating significant potential for food safety applications.