Plasmonic AgNPs Reinforced Flexible Stainless Steel Mesh SERS Sensor for In Situ Detection of Methylene Blue on Curved Samples

A stainless steel mesh loaded with silver nanoparticles (SSM/Ag) was developed as a low-cost and high-performance flexible surface-enhanced Raman spectroscopy (SERS) substrate for residual detection of methylene blue (MB) on curved samples. The sensor's performance was systematically investigated using rhodamine 6G (R6G) as a target molecule. The SSM/Ag substrate showed a limit of detection (LOD) of 10 −8 M and an enhancement factor (EF) of 1.4 × 10 6 . The experiment also utilized the SSM/Ag substrate to detect MB residues by wiping Alternanthera philoxeroides leaves, immersing river water samples, and performing in situ detection of the delivery label on the cup body. The results showed that the limits of detection (LODs) for these three cases were 10 −6 , 10 −7 , and 10 −7 M, respectively, exhibiting a reproducibility relative standard deviation (RSD) below 12%. This provides strong evidence for the validity and feasibility of the SSM/Ag substrate for in situ detection of MB residues on curved samples.