Efficient Optical Trapping and

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. Silver and gold nanoparticles have since ancient times been utilized to color glass. Also, they have been used for medical purposes due to their antimicrobial properties and are very efficient as probes for nanotechniques. To some extent, the physical and chemical properties of silver nanoparticles are comparable to gold. However, use of gold nanoparticles in conjunction with fluorescent techniques is complicated by the fact that the absorption spectrum of gold nanoparticles peaks in the visible range where most fluorophores emit light. Hence, gold nanoparticles severely quench fluorescence