Influence of the Solvent on the Surface-Enhanced Raman Spectra of Ruthenium(II) Bipyridyl Complexes

Abstract

In the present work a new dye, [Ru(dcbpyH2)2(bpy-TPA2)](PF6)2, and the well-known (Bu4N)2[Ru(dcbpyH)2(NCS)2] complex were investigated. The electronic transitions of both dyes showed solvatochromic shifts due to specific interactions of the ligands with the solvent molecules. The surface-enhanced Raman (SER) spectra of the dyes dissolved in water, ethanol, and acetonitrile were measured in silver and gold colloidal solutions. The results demonstrate that the dyes were adsorbed on the metallic nanoparticles in different ways for different solvents. It was also found that in the gold colloid, the aqueous solutions of both dyes did not produce any SERS signal, whereas in ethanolic solution the SERS effect was very weak. Deprotonation, H-bonding, and donor-acceptor interactions seem to determine these different behaviors. Our results indicate the important role of the charge-transfer mechanism in SERS.

Electric Field-induced Charge Transfer of (Bu4N)2[Ru(dcbpyH)2-(NCS)2] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

“…This view is consistent with the recent SERS study of N719 on colloidal nanoparticles. 29 It is noteworthy that the ν(NCS) bands are clearly observed at 2106, 2126, and 2076 cm , on Au, Ag, and Cu, respectively. From the SERS selection rule, 30 it was reported that the charge transfer (CT) mechanism could also significantly contribute the enhancement of the SERS intensities.…”

“…The bands are strongly solvent dependent and consistent with the previous report. 29 The intraligand charge transfer band was observed at 308 nm when the process was performed in water. The metal ligand charge transfer bands were observed at 370 nm and 502 nm.…”

“…Our assignment is mainly based on the previous literatures. 29 Considering that N719 should adsorb on metal surfaces via a strong anchoring with the NCS group, the molecule is expected to have a perpendicular orientation. From the electromagnetic (EM) selection rules, 30 the vibrational mode perpendicular to the surface should be more enhanced than the parallel one.…”

“…28 Solvent dependent charge transfer of the ruthenium bipyridine (Ru-bpy) dye on colloidal Ag and Au surface has been recently reported by means of SERS. 29 Although quite a few studies have explored the different adsorption structures of SAMs on metal surfaces, [20][21][22][23][24][25][26][27][28] no reports have investigated ruthenium bipyridine (Ru-bpy) dye on metal surfaces using potential dependent vibrational spectroscopy.…”

Infrared Spectroscopic Study of α-Cyano-4-hydroxycinnamic Acid on Nanocrystalline TiO2Surfaces: Anchoring of Metal-Free Organic Dyes at Photoanodes in Dye-Sensitized Solar Cells

“…7 In addition temperature-dependent interfacial vibrational spectroscopic tools can provide information on the energetics or phase transition of adsorbates on surfaces. [8][9][10] Despite several spectroscopic reports on Ruthenim (II) complexes, [11][12][13][14] there has not been either investigation on the spectroscopic study or the thermal degradation and the resulting change in molecular architecture in detail for a cyanoacrylic acid film fabricated on the TiO2 surfaces to the best of our knowledge. In this present work, temperature-dependent diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy was applied to understand the nature of adsorption and structural change of α-cyano-4-hydroxycinnamic acid (CHCA) on the TiO2 surfaces.…”