Surface-enhanced Raman Spectroscopy, Raman, and Density Functional Theoretical Analyses of Fentanyl and Six Analogs

The authors examined fentanyl and its six analogs using wB97XD/cc-pVTZ density functional theoretical (DFT) calculations as well as Raman and Surface-enhanced Raman spectroscopy (SERS). The in silico DFT calculations provided the vibrational frequencies, Raman activities, and normal mode assignment for each analog. Raman spectroscopy can detect crystalline fentanyl analogs but cannot obtain bands for samples in solution. Therefore, the authors utilized gold/silver nanospheres and gold/silver nanostars to examine them. The gold/silver nanostars provided stronger signals for the fentanyl analogs, and their SERS spectra can easily distinguish these fentanyl analogs from nonfentanyl opioids and other common drugs of abuse using principal component analysis and other statistical tests. Overall, their results demonstrate that SERS shows great potential to distinguish fentanyl analogs and detect trace quantities of these compounds in mixtures of seized drugs. (Published Abstract Provided)