LETTER pubs.acs.org/NanoLett Optical and Topological Characterization of Gold Nanoparticle Dimers Linked by a Single DNA Double Strand

bS Supporting Information Gold nanoparticles (AuNPs) have been extensively studied asphotothermal1,2 and optical contrast agents3,4 thanks to their large absorption and scattering cross sections at visible plasmon resonance frequencies. Functionalizing AuNPs with DNA strands is a powerful tool to drive the assembly of group-ings with optical properties that strongly depend on the distance between particles.5,6 This approach was successfully applied to the design of biosensors,79 molecular rulers,1014 and enhan-cers of Raman scattering1517 or fluorescence emission.18 For all these applications, it is desirable to fully control the chemical environment of the nanostructure and, in particular, to define the number of DNA strands grafted to each particle. Agarose gel electrophoresis,19 and more recently high-performance liquid chromatography (HPLC),20 were shown to allow the purifica-tion of gold nanoparticles linked to a known number of thiolate