What Controls the Optical Properties of DNA-Linked Gold Nanoparticle Assemblies?*

Abstract

This chapter describes a study aimed at understanding the factors that control the optical properties of DNA-linked gold nanoparticle aggregates containing oligonucleotide linkers of varying length. The pre- and postannealed DNA-linked assemblies were characterized by sedimentation rate, transmission electron microscopy, dynamic light scattering, and UV-visible spectroscopy which show that the oligonucleotide linker length kinetically controls the size of the aggregates that are formed under the preannealed conditions, thereby controlling the optical properties. DNA-based assembly method results in macroscopic assemblies consisting of thousands of particles and, therefore, offers a unique opportunity to study the collective properties of large nanoparticle network assemblies that have longer interparticle distances than previously studied systems. Mie theory was used to calculate extinction spectra for the DNA-linked nanoparticle aggregates from the dielectric functions of the aggregates. The aggregate dielectric functions were derived from the dielectric functions of the nanoparticles and of the aqueous medium using a recently developed effective medium theory.