SERS studies of isolated and agglomerated gold nanoparticles functionalized with a dicarboxybipyridine-trimercaptotriazine-ruthenium dye

A dicarboxybipyridine-trimercaptotriazine ruthenium complex, primarily designed for dye solar cells, has been successfully employed for generating electrostatically stabilized gold colloids, because of its high negative charge and capability of binding to gold nanoparticles via the sulfur groups. Surprisingly, a strong surface-enhanced Raman scattering enhancement has been observed for the isolated nanoparticles, exceeding those recorded after inducing agglomeration. Such unusual response has been ascribed to the predominant contribution of the charge-transfer and resonance Raman mechanisms, more than compensating for the lack of the local hot spots, in relation to the agglomerated systems. Copyright (c) 2014 John Wiley & Sons, Ltd.