Portable Surface-Enhanced Raman Spectroscopy of Pyridine and Diazines on MoS₂

Raman spectroscopy is a widely used analytical technique for biosensing applications. It has been commonly applied to bulk samples. However, the applications to small amounts of chemical substances is challenging due to weak signals. Surface-enhanced Raman scattering (SERS) can be used to improve sensitivity by the electromagnetic enhancement mechanism using plasmonic nanoparticles or by the chemical mechanism using atomically-thin semiconducting 2D materials. Also, portable Raman spectroscopy instrumentation is needed for medical and industrial point-of-care applications. We investigate the effects of the addition of few-layer molybdenum disulfide (MoS₂) nanocrystals on the enhancement of Raman signals of pyridine and its diazine derivatives. The introduction of MoS₂ leads to the shifts of the Raman peak positions and changes in the relative peak intensities and overall signal strength of respective ν₁ mode for each of the diazines and pyridine, as well as affecting a range of other modes for each compound, observed using a handheld Raman spectrometer, an effect most apparent in the pyrimidine ν₁ mode. This information can be valuable to a number of potential fields including studies in biophotonics, which could have numerous industrial, medical and public safety applications.