SERS spectroscopy for the therapeutic N-butyl-2-isonicotinoylhydrazine-1-carboxamide in silver nanocolloids at different concentrations: Experimental and DFT investigations

•Analysis of a carboxamide derivative's SERS spectra at different concentrations.•Theoretical modelling of SERS using silver cluster.•Presence of inactive Raman modes in SERS spectra with enhancements. SERS at different concentrations and vibrational spectroscopic studies of N-butyl-2-isonicotinoylhydrazine-1-carboxamide (INC) are reported. DFT calculations based on silver cluster model and TD-DFT calculations support experimental observations. Raman band enhancements that are only present in some of the SERS spectra further point to the contribution of charge transfer interactions to the overall enhancements INC's Raman modes. The presence of the inactive nR bands in the SERS spectrum is due to the presence of Ag and these show the chemisorption nature of INC with the silver surface in an inclined orientation according to selection rules. The method created in this study can accurately quantify INC and might be applied to medications with structural relevance. [Display omitted]