Carbon nanotubes and nanopipes have been shown to have great potential as cellular probes, for use as nanofluidic devices to transport solutions to or from cells. Making these nanopipes able to sense within the cells allows a huge of amount of additional information to be obtained. Surface-enhanced Raman spectroscopy (SERS) is a technique allowing greatly increased Raman signals used for trace detection and characterization of biological specimens with extremely high spatial resolution. In this work, both carbon nanotubes and nanopipes have been functionalized with SERS-active nanoparticles to allow development of versatile nanoprobes. Glycine was used to estimate the SERS activity and corresponding enhancement factor (10^8).

In this work, we experimentally investigated the surface-enhanced Raman spectroscopy (SERS) activity of faceted gold nanoparticles, which have been theoretically predicted to yield giant enhancements. Glycine was used to determine the SERS activity as a function of pH and ionic strength and to estimate the corresponding enhancement factor (EF). By optimizing the synthesis conditions of the flat prismatic nanoparticles, it was possible to control their size and shape. We demonstrate that the maximum SERS intensity increases with the edge length of the triangle, reaching a maximum EF of 13 for 1.9 μm triangles (the largest tested). The corresponding glycine detection limit was as low as 1012 M, close to the single-molecule threshold.

Controlled amounts of nanoparticles ranging in size and composition were embedded in the walls of carbon nanotubes during a template-assisted chemical vapour deposition (CVD) process. The encapsulation of gold nanoparticles enabled surface enhanced Raman spectroscopy (SERS) detection of glycine inside the cavity of the nanotubes. Iron oxide particles are partially reduced to metallic iron during the CVD process giving the nanotubes ferromagnetic behaviour. At high nanoparticle concentrations, particle agglomerates can form. These agglomerates or larger particles, which are only partially embedded in the walls of the nanotubes, are covered by additional carbon layers inside the hollow cavity of the tube producing hillocks inside the nanotubes, with sizes comparable to the bore of the tube.