Differentiation of illicit drugs with THz time-domain spectroscopy

The terahertz time-domain spectroscopy(THz-TDS) was used for sensing and identifying illicit drugs.The absorption spectra of seven illicit drug samples(morphine and its hydrochloride,cocaine hydrochloride,codeine phosphate,papaverine hydrochloride,pethidine hydrochloride,and thebaine) were studied by THz-TDS at 0.3-2.0 THz at room temperature.The geometric structure and vibration frequencies of morphine were calculated by density functional theory.The four absorption features were dominated by intra-/inter-molecular collective or lattice vibration modes.Each illicit drug has a distinct signature in its THz spectra.The results indicate that the THz-TDS can be used to identify and discriminate illicit drugs by their characteristic fingerprints.