DNA-induced assembly of gold nanoprisms and polystyrene beads into 3D plasmonic SERS substrates

The utilization of nanoparticle-polymer bead hybrid nanostructures as a SERS substrate depends on the control of the deposition, density, and distribution of nanoparticles on the bead surface. Here we demonstrate the fabrication of a large area SERS substate via a two- step DNA mediated assembly of gold nanoprisms and polystyrene (PS) beads into a large ensemble of beads that are densely coated with nanoprisms. First, nanoprisms are loaded on PS beads through DNA hybridization. The close packed arrangement of anisotropic nanoprisms in different orientations on a bead surface results in a plasmonic substrate with a variable nanogap size ranging 1-20 nm. Nanoprisms-coated beads are then assembled into a large stack or aggregate of beads using a DNA-induced crystallization approach. Each aggregate consists of 20-50 nanoprisms-coated beads, leading to the formation a large area of three-dimensional SERS substrate with a high-density of hot spots for SERS enhancement. An excellent enhancement factor (EF) of 1.09x10(5) and a very high detection sensitivity (up to 10(-10)M) are observed for the analysis of a probe molecule (Methylene blue) using the SERS substrate.