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Prof. Xiang Zhang's Laboratory at UC Berkeley |
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Nanoplasmonic Resonators Objective Our current research goal is to engineer active substrates for plasmon enhanced fluorescent and Raman spectroscopy studies of biomolecular physics, and for ultra-sensitive biomolecular detections. Background Collective oscillations of free electrons in nano metal particles exhibit resonance at optical frequencies, which is usually called particle plasmons. The excitation of resonant plasmon not only significantly enhances local electromagnetic field surrounding the particles, but also scatters incident light very strongly, making nano metal particles the brightest scatters. By employing the state-of-art nano fabrication technologies, fundamental physics of plasmon-plasmon coupling, plasmon-photon and plasmon-molecular interactions are being studied. Basic understanding of these interactions paves the way to ultra-sensitive single bio-molecular detections. 
Results Profound understanding of plasmon coupling and field enhancements between nanoparticles of various shapes and sizes will allow us to control the required resonant frequencies. Electron-beam and focused-ion beam are being used for making Au and Ag nanoparticles in a very repeatable and controllable fashion. The plasmon resonance spectra of individual nano particles have been measured using optical microscopic system coupled with a spectrograph. We have demonstrated new designed nano-plasmonic resonator (NPR) with tunable plasmon resonant wavelength from visible to near-infrared wavelength. This is a great flexibility for Raman laser sources selection. With our nano-manufacturing process which is compatible with standard cleanroom manufacturing process, we are able to integrate our nano plasmonic sensor into a lab-on-a-chip with microfludic systems for real-time in-vivo detection.
Reference [1] Q.-H. Wei, K.-H. Su, S. Durant, and X. Zhang, "Plasmon Resonance of Finite One-Dimensional Au Nanoparticle Chains", Nano Letters, Vol. 4, No.6, 2004, pp 1067-1071 [ 2] Su K-H., Wei Q.-H., Zhang X., Mock J.J., Smith D.R. and Schultz, S., "Interparticle Coupling Effects on Plasmon Resonances of Nanogold Particles", Nano Letters, Vol 3(8), 2003, pp1087-1090
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