Evidence for SERRS Enhancement in the Spectra of Ruthenium Dye-Metal Nanoparticle Conjugates

Metal-molecule interfaces have a high potential for applications in various fields of chemistry, as the features and functions of metal nanostructures can be modified and, to a certain degree, extended by surface bound molecules. In this article, the functionalization of complex colloidal particles, namely, Au nanopeanuts and Au/Pt/Au nano-raspberries, with the commercially available Ru complexes N719, N749, and Z907 is reported; these Ru complexes have already been applied as photosensitizers in dye-sensitized solar cells. A detailed investigation of the conjugates by means of Raman spectroscopy showed that the electronic structures of the ruthenium complexes are retained upon binding to the metal nanoparticles. Furthermore, microfluidics as an efficient tool for the systematic investigations of SER(R)S signal-enhancement dispersion in colloidal solutions was applied. The enhancement profiles obtained differed from the extinction spectra of the nanoparticles, indicating that electronically resonant processes are involved in the Raman signal enhancement of the investigated nanoparticle conjugates, in addition to the Raman signal enhancement due to the SERS effect.