HAuCl4/K4Fe(CN)6 reaction mediated silver nanosol as SERS substrate for robust detection of malachite green residue in seafood

Irreproducibility is considered as a significant obstacle to the widespread use of surface enhanced Raman spectroscopy (SERS) as a sensing platform. However, in terms of the SERS performance in applications, less attention has been paid on the stability, i.e., repeatability and reproducibility compared to sensitivity. Here, based on HAuCl4/K4Fe(CN)6 reaction and silver nanosol (Ag NS), a reaction mediated SERS (R-SERS) platform was proposed for the detection of malachite green residue (MG) in aquatic products, aiming to improve both the sensitivity and stability of SERS. Wherein, the HAuCl4/K4Fe(CN)6 reaction produced Au0 grows on Ag NPs and provided additional "hot spots" to enhance signal intensity. Meanwhile, the reaction system released cyano group (-C equivalent to N) will cap on the surface of Ag or Au NPs and act as an internal signal at -2100 cm-1 to adjust the background signal. As a proof of principle, adenine (Ade, 730 cm- 1), ceftriaxone (Cef, 1345 cm-1) and MG (1170 cm-1) were selected as targets to discuss the detection performance, with linear ranges of 0.1 - 20 mu M, 0.1 - 10 mu M and 0.1 - 2 mu M and limit of detection (LOD, 3a/M) of 0.079 mu M, 0.050 mu M and 0.032 mu M, respectively. In practical applications, MG residue in aquatic products were detected with the recoveries ranged from 85 % to 98 % and the coefficient of variations of intra-assay below 6.6 %. The R-SERS platform, therefore, was demonstrated to enhance SERS intensity and stability with in situ growth of label on Ag NPs, suggesting its potential applications in SERS sensing.