Functionalization of multilayer carbon shell-encapsulated gold nanoparticles for surface-enhanced Raman scattering sensing and DNA immobilization

In this paper, we reported the surface modification of multilayer carbon shell-encapsulated gold nanoparticles (Carbon Nanoparticles, or CNPs) via an oxygen plasma treatment approach and their subsequent functionalization with extraneous gold (Au) nanoparticles for Surface-enhanced Raman Scattering (SERS) sensing and DNA immobilization. The oxygen plasma treatment process led to purification of the multilayer carbon shell, reduction of the shell thickness, and derivatization of carbon shell with functional carboxylic groups. This further opens potential opportunities for surface functionalization of CNPs with extraneous Au nanoparticles or λ-DNA fragments, which were both achieved through a well-defined carbodiimide based covalent linking chemistry without removing the CNPs from the substrate. The resulting CNP-Au nanoparticle hybrids as well as the CNP-DNA architectures were characterized using various microscopic and spectroscopic techniques. The CNP-Au nanoparticle hybrids were further used as highly-sensitive SERS substrate for the detection of trace amount water-containing organic molecule. Meanwhile, they were also fundamentally simulated for their plasmonic behavior using discrete dipole approximation (DDA) method to understand the basic Raman enhancement principle. On the other hand, highly-ordered assembly of CNP-DNA architectures were also demonstrated in detail for their great potential in future DNA detection/recognition and bio-device applications.