Figure 1 - Molecular structure of dye 1 with ring numbers (Se1 – Se4) and showing the torsion angles.
Figure 2 - (a) Calculated and experimental electronic spectra for dye 1. (b) extinction spectrum for the HGN alone, with dye 1 added and with the labeled HGN aggregated; (c) electron density of the p (left) and p* (right) orbitals which give the 826-nm band in (a) and (b).
Figure 3- Normalized resonance Raman spectra for dye 1 at three excitation wavelengths (514, 633, and 785 nm).
Figure 4 - For dye 1, comparison of the 785-nm resonance spectrum with the corrected theoretical spectrum and displacement diagrams for the 1588 cm-1 vibration.
Figure 5 - SERRS of dye 1 obtained with 785-nm and 633-nm excitation compared to resonance spectra.
Figure 6 - SERS of dye 1 obtained with 1064- and 1280-nm excitation.
Figure 7 - SERS spectrum of dye 1 taken with 1280-nm excitation and compared to the theoretical calculation with the Se1 or Se3 ring or both rings rotated.
Figure 8 - Extreme positions of the vibrational displacements for the vibration at 1179 cm-1 (a) with the positions superimposed and for the vibration at 732 cm-1 (b) with each extreme shown separately.
Figure 9 - (a) The ssp, ppp, and sps SFG spectra of dye 1 on a polycrystalline gold film. (b) PNA results for the 1600-cm-1 resonance showing a minimum at a polarization angle of -65.2°. (c) The molecular frame coordinate system used for orientation analysis of the pyrylium backbone and the relationship between the macroscopic laboratory frame and microscopic coordinate system (below). (d) Simulation of the ssp to ppp SFG intensity ratio for the 1600-cm-1 symmetric stretch.
Figure 10 - Space filled model of the dye on the surface showing the two selenophene rings rotated and the position of the thiopyrylium S atom.