Surface enhanced Raman scattering detecting polycyclic aromatic hydrocarbons with gold nanoparticle-modified TiO2 nanotube arrays

A metal-semiconductor heterojunction material was fabricated by photocatalytically depositing Au nanoparticles (NPs) inside titania nanotubes, and have been applied, for the first time, to the surface enhanced Raman (SER) scattering detection of polycyclic aromatic hydrocarbons (PAHs). Due to the nanotubular structure of the Au-NPs/TiO2 nanotubes (NTs), a localized surface plasmon resonance is generated within the Au-NPs/TiO2 NTs, which results in an enhanced three-dimensional electromagnetic field. Raman enhancement occurs when the PAH molecules are spatially confined within the zone of the Au-NPs/TiO2 NTs. The achieved detection limit of 12.6 nM, by utilizing a low-cost small Raman spectrometer, is comparable to the published values obtained with surface enhanced Raman scattering. The recovery rates measured with different water samples range from 89.97% to 116.2%.