Study on the detection of cocaine in Argentinian banknotes by SERS

Abstract

Flexible Surface-Enhanced Raman Spectroscopy (SERS) substrates based on silver nanoparticles (AgNP) immobilized in agar gels have been developed to detect cocaine in $ 100 Argentinian banknotes by SERS spectroscopy. The AgNP were characterized by absorption spectroscopy and Scanning Transmition Electron Microscopy (STEM). The SERS substrates were first evaluated using a probe molecule, methylene blue (MB), with well-known SERS activity. The achieved limit of detection (LOD) was ∼3 pg.cm−2 (∼60 molecules/spot). SERS experiments with cocaine hydrochloride were performed using these substrates; the LOD achieved was ∼70 ng.cm−2 (0.7 fg/spot). Cocaine was detected on intentionally contaminated $ 100 Argentinian banknotes. Finally, the analysis of 10 banknotes in circulation (one of which was intentionally contaminated as a blind test) resulted in the detection of cocaine in two of the banknotes analysed.