Surface‐enhanced Raman spectroscopic investigations of thiazole orange derivatives using visible and near‐infrared excitation

Abstract

AbstractSurface‐enhanced Raman spectra of the two thiazole orange derivatives, TO6 {1‐(N,N'‐tetramethyl‐1,3‐propanediaminopropyl)‐4‐[3‐methyl‐2,3‐dihydro(benzo‐1,3‐thiazole)‐2‐methyliden] quinolinium triiodide} and TOTO {1,1′‐(4,4,8,8‐tetramethyl‐4,8‐diazaundecamethylene)‐bis‐ 4‐[3‐methyl‐2,3‐dihydro(benzo‐1,3‐thiazole)‐ 2‐methylidene] quinoliniumtetraiodide}, were recorded with visible (457.9 and 514.5 nm) and near‐infrared (1064 nm) excitation on silver colloids. The spectra were compared with the corresponding non‐enhanced Raman spectra obtained in the near‐infrared region and the resonance Raman spectra obtained with visible excitation. The qualitative enhancement pattern is explained within the electromagnetic theories. Partial assignment of the vibrational wavenumbers was achieved by comparison of observed band positions and intensities in the IR and Raman spectra with wavenumbers and intensities from quantum chemical calculations. Information on the adsorption geometry at the silver surface can be obtained on basis of this assignment. The surface‐enhanced Raman spectrum of TOTO on gold colloids was recorded with 1064 nm excitation and compared with the corresponding spectra on silver colloids.