Graphene-quantum-dot assembled nanotubes: a new platform for efficient Raman enhancement.

Graphene quantum dots (GQDs), single or few-layer graphenes with a size of only several nanometers, are a new type of quantum dots (QDs) with unique properties. The assembly of QDs in a geometrically well-defined fashion opens up opportunities to obtain access to the full potential of assembled QDs by virtue of the collective properties of the ensembles. In the current study, we present the well-organized assembly of zero-dimensional (0D) functional GQDs into 1D nanotube (NT) arrays and demonstrate their remarkable potential as a new metal-free platform for efficient surface-enhanced Raman scattering (SERS) applications. The hierarchically porous 1D nanotube structure of 0D GQDs has been prepared by electrophoresis deposition within a nanoporous AAO template. On the basis of the unique porous nanotube architecture of GQDs, the GQD-NTs could ensure a more efficient charge transfer between the target molecules and the GQDs and thus produce much stronger SERS effect, exceeding that on flat graphene sheets. The unique architecture of 1D nanotubes of 0D GQDs provides a new point of view for designing and fabricating SERS substrates.