ZnO-nanotaper array sacrificial templated synthesis of noble-metal building-block assembled nanotube arrays as 3D SERS-substrates

This paper describes a ZnO-nanotaper array sacrificial templated synthetic approach for the fabrication of the arrays of nanotubes with tube-walls assembled by building-blocks of Ag-nanoplates, Au-nanorods, Pt-nanothorns or Pd-nanopyramids, thus possessing high-density 3D ＂hot spots＂ in sub-10-nm gaps of neighboring building blocks with nano-tips, -corners or -edges. Additionally, these hierarchical nanostructure arrays possess high surface area with rich surface chemistry, being beneficial to capturing the analyte. The Ag-nanoplate- assembled nanotube arrays can be used as sensitive surface-enhanced Raman scattering （SERS） substrates with good signal uniformity and reproducibility. Using such Ag hierarchical nanostructure arrays as SERS-substrates, not only has 10-14 M rhodamine 6G been identified, but also 10-7 M polychlorinated biphenyls （PCBs, a notorious class of persistent organic pollutants） are recognized, and even two congeners of PCBs can be identified in a mixture, showing the potential applications of the materials in SERS-based rapid detection of environmental organic pollutants.