SERS, Raman, and DFT analyses of fentanyl and carfentanil: Toward detection of trace samples

We examine the normal Raman and the surface-enhanced Raman spectra of fentanyl and carfentanil. As an aid in the assignment of the spectral lines, we present a density functional theory calculation. Although Raman spectroscopy is a valuable analytic tool for the detection and identification of molecular species, it is a weak effect and requires specialized equipment for detection of trace samples. We therefore turn to surface-enhanced Raman spectroscopy, which utilizes the large enhancement of the Raman signal endowed by proximity to silver or gold nanoparticles. The enhancement factor (EF) obtained in this experiment is ≥1.6 × 105. This points the way towards future development of a simple and sensitive technique for the detection of analytes in trace quantities, particularly for wider application in forensic science.