Trace detection of multiwalled carbon nanotubes using Raman-enhancing silver nanocap arrays

A convenient strategy is demonstrated for trace detection of multiwalled carbon nanotubes (MWNTs) using Raman-enhancing silver nanocap arrays. Microstructural analysis indicates that the hot spots are evenly distributed on the substrate. A brief analytical methodology to evaluate the dispersity of adsorbed MWNTs with different ultra-low concentrations by 2D point-by-point Raman mapping is proposed. The detection limit of this method was found to be 3 ppb. Our results open new possibilities for applying surface-enhanced Raman scattering to trace detection of an inorganic probe.