Ruthenium dye functionalized gold nanoparticles and their spectral responses

Abstract

The functionalization of metal nanoparticles provides access to materials with unique chemical and physical properties for a wide range of applications, e.g. in catalysis, optoelectronics and material science. However, the fundamental light induced charge transfer processes and electronic interactions at the functional nanoparticle–molecule interface, which constitute these unique properties, are not yet fully understood. In this work monodisperse spherical gold nanoparticles functionalized by the photoactive ruthenium dyes (Bu₄N)₂[Ru(dcbpyH)₂(NCS)₂], (Bu4N)₃[Ru(tcterpy)(NCS)₃] and [Ru(dnbpy)(dcbpyH₂)(NCS)₂] (Bu₄N = tetrabutylammonium, dcbpyH = 2,2′-bipyridyl-4,4′-dicarboxylato, NCS = isothiocyanato, tcterpy = 2,2′:6′,6′′-terpyridyl-4,4′,4′′-tricarboxylato, dnbpy = 2,2′-bipyridyl-4,4′-dinonyl) known as N719, N749 and Z907, and [Ru(tbbpy)₂(tpphz)](PF₆)₂ (tbbpy = 4,4′-butyl-2,2′-bipyridine, tpphz = tetrapyridophenazine, PF₆ = hexafluorophosphate) (Ru) were synthesized in aqueous solution applying a conjugation and a phase transfer reaction approach, respectively. The functionalized nanoparticles obtained were analyzed by UV-vis spectroscopy, TEM imaging and Raman spectroscopic techniques in order to investigate the molecular structures of the photoactive ruthenium dyes at the gold surface. The results indicate, that the dyes' fully conjugated electronic structure and therefore, their photophysical properties, are preserved or only slightly altered upon binding to the surface of the gold nanoparticles, which potentially allows for rapid and efficient transport of charges to the nanoparticles after photoexcitation.