End-to-End Alignment of Gold Nanorods on Topographically Enhanced, Cylinder Forming Diblock Copolymer Templates and Their Surface Enhanced Raman Scattering Properties

Abstract

We present a facile methodology for the end-to-end assembly of gold nanorods of various aspect ratios on corrugated, horizontal, cylinder-forming diblock copolymer templates. Although the depth of corrugation is significantly smaller than the diameter of the nanorods, they exhibit excellent selectivity (>98%) and alignment for placement in the polymer grooves due to capillary forces and the substrate’s topography. Enhanced corrugation of the diblock template is achieved by chemical swelling prior to deposition of the metallic nanorods. Graphoepitaxy of the diblock copolymer in nanoconfining channels is employed to achieve essentially perfect long-range orientation of the substrate, while subsequent deposition of nanorod arrays whose alignment maps onto that of the diblock template with high fidelity provides novel organic–inorganic hybrid surfaces whose surface enhanced Raman spectroscopy (SERS) properties are characterized. These arrays of aligned gold nanorods exhibit polarization-dependent spectra for adsorbed molecular species with a 24-fold enhancement in signal intensity when the trenches are aligned with parallel versus perpendicular orientation with respect to the incident polarization of the excitation laser. The simple construction of these systems and their unique SERS properties provide a new and efficacious platform for the construction of functional nanodevices.