Dual-mode SERS/colorimetric sensing of xanthine in fish and shrimp based on peroxidase like activity multifunctional CoS@au nanoflower

Xanthine (XOE) is an important indicator for evaluating the freshness of aquatic products. This study successfully synthesized three-dimensional cobalt sulfide nanoflowers loaded with gold nanoparticles (CoS@Au). This material innovatively constructs an enzyme nanoflower cascade sensing system and integrates peroxidase like catalytic activity with surface enhanced Raman spectroscopy (SERS) enhancement capability on the same platform. In the presence of hydrogen peroxid (H 2 O 2 ), CoS@Au It can catalyze the oxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) to generate oxTMB, while producing significant color changes, strong UV–vis absorption, and Raman signals. This study presents a dual-mode sensor that effectively integrates the intuitive simplicity of colorimetry with the high sensitivity of SERS. This design overcomes the limitations of single-mode methods, such as restricted detection sensitivity and susceptibility to interference, by enabling cross-validation between the two modes. The constructed SERS/colorimetric platform achieves a detection limit of 9.69 × 10 −11  mol/L for XOE, thereby realizing ultrasensitive detection and visual analysis of analytes in shrimp and fish food samples. These results demonstrate its strong application potential in complex practical applications.