Surface enhanced Raman scattering of melamine on silver substrate: An experimental and DFT study

•Experimental and DFT studies of SERS of melamine on silver substrate is investigated.•Interaction of melamine and different Agn cluster (n = 4–20) were computed.•676 and 983 cm− 1 typical peaks were enhanced and well reproduced by calculations.•Spectra enhancement results from charge transfer phenomenon within molecule.•SERS of melamine show distinct spectra like ring breathing or trigonal bending.

Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that allows amplifying weak Raman signals by the excitation of localized surface plasmons. In this paper, we used nanoscale roughened silver surface to enhance Raman signals of melamine analyte. Silver nanoparticles were synthesized by wet-chemical method and employed for SERS measurement. Theoretically, optimized geometries and vibrational frequencies of melamine and melamine absorbed on silver-cluster surface were calculated by using the B3LYP/6-31G(d) method. Then, the predicted spectrograms are compared with the experimental Raman spectra. As a result, Raman signals of melamine were dramatically enhanced by using obtained silver nanoparticles as the substrate. Typical peaks of melamine at 676 and 983 cm− 1 were enhanced and could be obviously observed in experiments. The calculated vibrational frequencies seem to relatively coincide with the experimental values. SERS effect of melamine on nanoscale silver was also explained by analyzing molecular frontier orbitals (HOMO and LUMO) melamine–silver complexes.

Graphical abstractExperimental and density functional theory studies of Surface enhanced Raman scattering of melamine on silver nanoparticles has been reported.Figure optionsDownload full-size imageDownload as PowerPoint slide