Rapid and sensitive SERS detection of food contaminants by using nano-Ag aggregates with controllable hydrophobicity

Abstract

There is an increasing demand for rapid and sensitive detection of hydrophobic contaminants in foods. A rapid and sensitive surface enhanced Raman scattering (SERS) detection method was developed for this purpose, based on the surface modification of nano-Ag aggregates, which had rich hot spots and controllable hydrophobicity. Cationic surfactants with different carbon chain lengths were employed to modify the aggregation of Ag nanoparticles. The adsorption of cationic surfactants on nano-Ag aggregates increased the hydrophobicity of the surface of the nano-Ag aggregates as the SERS substrate. By changing the carbon chain length of the surfactant, the hydrophobicity of the SERS substrate was able to be tuned to match with the hydrophobicity of the contaminants to be detected. Different hydrophobic contaminants such as Auramine O, Sudan I and Sudan III could be quantitatively detected, with a detection limit as low as 6.1 × 10−8, 7.5 × 10−9, 2.1 × 10−9 mol L−1, respectively. Compared with the traditional inorganic salt aggregation method which was unable to meet the requirements of direct quantitative detection in the sample matrices, the developed method was confirmed to have the advantages of low detection limit, good reproducibility (relative standard deviation (RSD) is less 7.6%), short operation time (about 1 min), and no need of any complicate pretreatment for sample preparation.