The Drude model of the free electron sea survives the transition to the nanoscale, but with surprising results. Most easily observed in noble metal nanoparticles, the plasmas of these particles interact with the photons of light, and develop resonant oscillations at specific frequencies. These are called plasmons, and where they arise is determined by the material, environment, size, and shape of the nanoparticle. As seen above, colloids of gold and silver nanoparticles can have vivid and varied colors.
Our current research focuses on the controlled assembly of anisotropic metal nanoparticles, followed by the spectroscopic and microscopic characterization of the resulting structures. Our goal is to create new systems with enhanced optical properties, with potential applications ranging from sensitive detection to integrated optical processing. The above image demonstrates our current ability to monitor the development gold bipyramid nanoparticle dimers in-situ (JPCC 2014 ). The below image demonstrates our ability, in collaboration with the Sibener lab, to control the long range alignment of gold nanorods using shallowly corrugated diblock copolymer templates. These nano-ribbons exhibit orientation dependent surface enhanced Raman scattering, with a 24x increase in signal intensity when aligned with, vs. against, the laser polarization (JPCC 2014).