Control of nanoparticle charge via condensation magnification

Previously, we reported a method for preparing highly charged nanoparticles via condensation magnification [Suh, J., Han, B., Kim, D. S., & Choi, M. (2005). A method for enhanced charging of nanoparticles via condensation magnification. Journal of Aerosol Science, 36, 1183–1193]. In the present work, we attempt to control the charge level of nanoparticles by varying the droplet size in the condensation magnification method. We also investigate whether both metallic and dielectric nanoparticles could be highly charged and their charge level can be controlled. Three different cases of 12 and 25 nm gold particles and 22 nm polystyrene polymer (PSP) particles were examined and for all three cases, the number of elementary charges could be successfully controlled by varying droplet sizes. The maximum charges of 12 and 25 nm gold nanoparticles were about 15 and 57 units, respectively, and that of 22 nm polystyrene polymer (PSP) particles was 43 units. Surface electric field strength corresponding to these maximum charges was found to be approximately independent of particle sizes indicating that ion evaporation model could be valid in our charging process.