Single Gold Nanorods: Optical Trapping and Biosensing

Dr Peter Zijlstra

Marie Curie Fellow, Molecular Nano-Optics and Spin group, Huygens Laboratory, The University of Leiden, Netherlands

3:30 pm Tuesday, 12 October 2010,
EN102 (EN Building), Hawthorn.

Correlations between the local structure and mechanical properties are challenging to measure in a crowded environment such as a living cell. The environment in a living cell is highly organized and communication between different mechanical processes is essential to many functions. Optical tweezers are ideal tools to study cell mechanical properties, so optically trapping objects of the smallest possible size will be advantageous for experiments in such crowded environments. Gold nanoparticles can be trapped down to sizes of about 20 nm diameter, much smaller than typically used polystyrene or glass beads (~1 micron in diameter). Gold nanorods are especially promising: besides force, they also experience a torque in a polarized optical trap, due to their anisotropic polarizability. An additional advantage of using a gold nanorod is that the narrow and intense surface plasmon resonance is not only sensitive to the shape and size of the particle, but also to the refractive index of its local environment. As such the plasmon resonance can be used as a refractive index sensor to map structures in the near-field of the particle. I will show recent experimental results on the 3D optical trapping and biosensing with a single gold nanorod. I will also give a short outlook on the possibilities of using a trapped gold nanorod as a simultaneous force and index probe.

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