Identification and classification of ATS in oral fluid based on Ag nanoassemblies on Si surface doped with Au nanobipyramids

Abstract

Herein, a novel Ag NP substrate doped with Au nanobipyramids was designed and fabricated via a convenient procedure of galvanic reaction for the identification and classification of amphetamine-type stimulants (ATS) in oral fluids in combination with surface-enhanced Raman spectroscopy (SERS). The substrate was shown to have a three-dimensional nanostructure, high SERS activity, and good stability. In combination with SERS, the Ag NP substrate doped with Au nanobipyramids was able to detect ultra-low traces of ATS, including amphetamine, methylamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethylamphetamine in oral fluid, with limit of detection values as low as 10–14 mg/mL, which is much better than the current spectroscopic techniques, and there exists a good negative linear relation between concentration and peaks intensity at nanogram (10–9 mg/mL) concentration level. In addition, multivariate analysis showed that partial least squares-discriminant analysis model could discriminate among different ATS. The approach can be broadly applied to the ultra-low trace detection of ATS and would be particularly useful for the analyses of nitrogenous organic compounds.