An ultrasensitive near-infrared satellite SERS sensor: DNA self-assembled gold nanorod/nanospheres structure

Abstract

Coupled plasmonic assemblies have recently attracted tremendous research interest in the field of Surface Enhanced Raman Scattering (SERS) due to their unique optical and biocompatible properties. Using DNA to connect different parts of assembled plasmonic nanostructures has been a simple but useful method to achieve the expected nanocomposites. This work prepared a satellite SERS substrate based on gold nanorod/gold nanosphere structures, in the hope of providing a novel SERS sensor for biomedicine related applications. A seed growth method was adopted to fabricate gold nanorods, using a region specific method to connect the gold nanorod core with the gold nanosphere satellites. The fabricated nanocomposites were further self-assembled with p-mercaptobenzoic acid (p-MBA) molecule layers as Raman reporters for SERS experiments. The obtained satellite nanostructure could produce “hot spots” between the gold nanorods and gold nanospheres to improve the SERS sensitivity and also to function as a key factor to tune the localized surface plasmon resonance (LSPR) absorption band to the near-infrared region. Finally, the optimized satellite SERS sensor was applied in the detection of Crystal Violet (CV) with a limit of detection as low as 10⁻¹¹ M, proving that the self-assembled nanocomposite could act as an effective substrate for single molecule detection.