Detection of explosives by surface enhanced Raman scattering using substrate with a monolayer of ordered Au nanoparticles

Monolayers with different structures arranged by 5 nm Au nanoparticles were grown using a self-assembly method on Si substrates. Raman spectra of ammonium nitrate (NH4NO3) and cyclotrimethylenetrinitramine (RDX) explosives adsorbed on bare and Au nanoparticle covered Si substrates were measured. Effects of Au monolayers and their structures on surface enhanced Raman scattering (SERS) of NH4NO3 and RDX were investigated. The monolayer arranged by Au nanoparticles into linear arrays is more sensitive to the explosives than that arranged into hexagonal close-packed structure. The detection limit using the substrate covered by a monolayer of Au nanoparticle linear arrays is about 7.7 ppm for NH4NO3 and 0.19 ppm for RDX. The integrated intensity of the vibration peak increases linearly with an increase in explosive concentration in log-log scales for both NH4NO3 and RDX. The enhancement factor is 7.0 x 10(4) for RDX. Monolayers of Au nanoparticles arranged into linear arrays have potential applications in detecting or identifying explosives at very low levels of concentration. (C) 2014 Elsevier B.V. All rights reserved.