Analysis of the Motion of Gold Nanoparticles in Ionic Liquids Under Electron Irradiation

Nanoparticles exhibit unique properties as a result of their shape and size, making them useful for a variety of applications, particularly in medicine for drug delivery, biosensors, and imaging. Plasma synthesis of metal nanoparticles, which involves the use of reactive plasma species to reduce metal salts and form nanoparticles, can provide an alternative to conventional synthesis methods that require high pressures and the use of toxic materials. During the plasma exposure, significant mixing in the liquid is observed, and the level of mixing may influence the size of the resulting nanoparticles. To quantify mixing in the liquid, this study analyzes the motion of pre-fabricated 200-nm gold nanoparticles suspended in two ionic liquids. The motion is observed in a field emission scanning electron microscope, and PASCO and ImageJ were used to track the particles and analyze their motion. Results indicate that the average particle velocity and acceleration both increase with electron beam voltage, and the higher viscosity liquid gives slower average particle velocities. We observed variations in particle speeds depending on the distance from the center of the field of view. This suggests that the induced electric field from the SEM affects particle motion. The insights gained from this work will help optimize nanoparticle synthesis and quantify the parameters that control particle size.