Effect of Au nanorod assemblies on surface-enhanced Raman spectroscopy

Monolayer and multilayer arrangements (consisting of disorder, parallel alignment and perpendicular superlattice) of hydrophobic gold nanorods have been prepared on silicon substrates via the evaporation-based self-assembly and the heat treatment methods, and the substrates were provided for the surface-enhanced Raman spectroscopic (SERS) examination. The perpendicular superlattice assembly of gold nanorods maximally enhanced intensities of Raman bands in comparison with parallel and disorder assemblies. Moreover, multilayer films of gold nanorods were more effective on SERS than monolayer films. The motive force of the Raman enhancement should be the adequate resonance coupling of localized surface plasmon waves at the reasonable density of spaces between neighboring rods. Moreover, the adsorption ability of analytes on the hydrophobic peripheral octadecyltrimethoxysilane groups will also improve the detection limit and develop the detection scope from aqueous to organic solutions.