Rapid identification and quantification of illicit drugs on nanodendritic surface-enhanced Raman scattering substrates

In this paper, we demonstrate rapid, sensitive and specific detection of illicit drugs in both aqueous samples and saliva using surface-enhanced Raman scattering (SERS) substrates with a unique, dendritic architecture. The substrates are prepared on a reusable microelectrode platform by electrokinetically assembling colloidal silver nanoparticles from a droplet. Identification and quantification of illicit drugs is accomplished on these substrates with the aid of Principal Component Analysis (PCA) coupled with a Support Vector Machine (SVM). We demonstrate 100% accuracy in the detection of four different illicit drugs (cocaine, heroin, THC, and oxycodone), and 98.3% accuracy in the quantification of cocaine across four orders of magnitude. Finally, we demonstrate a simple method, with limited sample processing, for the ultrasensitive detection of cocaine in saliva to a limit of detection of 100 ppb.