Efficient optical trapping and visualization of silver nanoparticles.

We performed efficient optical trapping combined with sensitive optical detection of individual silver nanoparticles. The particles ranging in size from 20 to 275 nm in diameter were trapped in three dimensions using low laser power by minimizing spherical aberrations at the focus. The optical forces were quantified, and we found that the larger the particle, the stronger the optical force. The particles were imaged by an additional strongly scattered laser.