Electron beam manipulation of gold nanoparticles external to the beam

The electron beam (e-beam) of transmission electron microscopy (TEM) was utilized for in situ synthesizing and manipulating Au nanoparticles with various sizes in HAuCl4 aqueous solution. The driving force for e-beam manipulation was found to be a function of particle-to- beamdistance, mostly due to the electric force. From experimental observations, it was concluded that the e-beam can attract the Au nanoparticles in the HAuCl4 solution. This contributes to the dipole induced in the Au nanoparticle, which is attributed to the non-uniform positive potential built inside the observation window. On the other hand, this positive potential would induce a repulsion force with the positively charged Au nanoparticle. Therefore, repulsion behaviour of the Au nanoparticle induced by the e-beam was also observed.