Size Analysis of Trapped Goldnanoparticles using Polarimetry

Abstract

We have developed a method of charging and trapping single gold spheres with a radius of 50 nm for the purpose of ablation. To achieve this we use electrospray ionisation to separate and trap these particles. Charged particles are trapped inside a linear ion trap. As we intend to do laser ablation on single gold nanospheres we need to determine whether the trapped particles are aggregated. Therefore, we test a method to do in-situ measurements of the size of the particles in the trap, by comparing the polarisation dependent scattering of those particles with Mie theory.

We have carried out experiments with a Helium-Neon laser and a 785 nm diode laser on five different particles for which the results seem to indicate radii of 466(2) nm, 465(1) nm, 577(2) nm, 342(1) nm and 577(2) nm. A second experiment was done on different particles with three diode lasers (642 nm, 785 nm,852 nm) on two different particles. These experiments suggest particle sizes of 179(1) nm and 179(1) nm. As a single gold colloid has a radius of 50 nm, we found that trapped particles were aggregated.