Optimized optical trapping of gold nanoparticles.

Metallic nanoparticles are of significant interest due to their particular optical and biological applications. Gold nanoparticles are proven to be excellent candidate for in vivo micro-manipulation using Optical Tweezers. This manuscript reports on stable 3-D trapping of 9.5-254nm gold nanospheres using substantially decreased laser power. The lower limit is approximately 2 times smaller than previous record. 5.4nm gold nanospheres were trapped for only 2-3 seconds. For the first time, our experimental data verify the volume corrected Rayleigh model for particles smaller than 100nm in diameter. Measuring the maximum applicable force for gold nanoparticles, we have shown that a few tens of milli-Watts of laser power can produce pico-Newton range forces.