Enhancing SERS hotspots via MXene-supported Au nanostructures on carbon paper for ultrasensitive thiophanate-methyl sensing in fruits.

For the common fruit contaminant thiophanate-methyl (TPM) residue monitoring, a portable ultra-sensitive flexible surface-enhanced Raman scattering (SERS) chip was developed using carbon paper and electrochemical deposition technology for the rapid and efficient trace detection of TPM in fruits. The flexible chip was constructed using MXene (CP-MXene) through layer-by-layer assembly and plasmonic metal (CP-MXene@Au) by the chronopotentiometry method, which dramatically improved the intrinsic electrical conductivity contributing to forming SERS-active "hot spot" with superior stability and reproducibility. Based on prepared SERS chip, the TPM was rapidly detected as the lowest detection limit as 0.00923 μM and a wide detection linear range of 0.1-100 μM. Furthermore, TPM in fruits can be collected and recognized with excellent reusability and satisfactory recovery of 90.5-109.5%, demonstrating its good practical applicability. This flexible SERS chip is also highly sensitive and low-cost, providing a new idea for efficient food safety monitoring.