Characterization of indigo carmine with surface‐enhanced resonance Raman spectroscopy (SERRS) using silver colloids and island films,and theoretical calculations

The application of resonance Raman (RR) and surface‐enhanced resonance Raman (SERR) spectroscopies to the qualitative and semiquantitative analysis of the artificial dye indigo carmine has been examined using sodium‐citrate‐reduced silver colloid and island films with various roughnesses. Additional, the Raman spectrum of the solid state and density functional theory (DFT) calculations helped to a better understanding of the fully optimized geometry and of the vibrational wavenumbers of the dye. A strong chemical interaction of indigo carmine with the silver colloidal particles was observed mainly at very low concentration of 0.03 × 10^?9 M and with silver film surfaces at a concentration of 10^?4 M . The indigo carmine orientation possibilities while going to different metallic substrates are discussed. Copyright © 2007 John Wiley & Sons, Ltd.