Fall 2010 IAB
September 15 to 17

Brendan Turner

Nature-Inspired Au-CNT Structures for Plasmonic Applications

Plasmonic nanostructures have enabled a variety of new methods for interfacing with biological systems. Specifically, when incident light impinges on metal nanostructures it induces collective electron oscillations or plasmons. These plasmons can be used for sensing technologies such as surface enhanced Raman spectroscopy (SERS) and plasmon resonance energy transfer (PRET). We report a novel nano-plasmonic structure based on de-wetting of Au on carbon nanotubes (CNTs). Just as beads of dew form on blades of grass, the poor adhesion between Au and CNTs gives rise to a collinear collection of discrete Au nanoparticles on the CNTs after evaporation. This Au coating forms a three dimensional collection of plasmonic nanoparticles ideal for SERS. The AuCNT structure is easily fabricated (< 5 hours) and scalable (up to 150 mm wafers). Also, by annealing the AuCNT structure we can control the formation of regular sized Au beads, effectively tuning the plasmon resonance from 850 nm to 500 nm. The viability of this hybrid plasmonic nanostructure has been demonstrated with SERS. Raman spectroscopy can identify target molecules through characteristic interactions of light with the molecules’ vibrational modes. However, the effect is very weak. In SERS, both the incident and scattered light are amplified through localized surface plasmons on metal nanostructures. A properly tuned SERS substrate generates an enhanced spectroscopic ‘fingerprint’ for detecting target molecules at low concentrations (1 nM with the AuCNT substrate). By taking advantage of simple bottom-up fabrication techniques we have created an easily fabricated, uniform, and scalable structure. We anticipate the stability and simplicity of the Au-CNT structure will lead to plasmonic applications such as Raman tags and localized heating as well as SERS and PRET.