Synthesis of hollow nanoparticles by plasma polymerization

A capacitively coupled low pressure plasma is used to produce particles by plasma polymerization of various organic precursors. The particles produced by this method are spherical, submicron in diameter, and contain a hollow center. Sixteen organic molecules were tested for the ability to produce hollow particles. Of these, 12 were found to reproducibly result in the formation of hollow particles while the other 4 either produced non-hollow particles or no particles at all under the conditions investigated here. Cyclohexane derivatives and the presence of an aromatic ring correlate strongly with a tendency to form hollow centers. The particle sizes vary from 70 nm to nearly 1 μm and the core diameter is on the average 18% of the particle diameter. The corresponding shell thickness ranges from 24 nm for styrene to about 360 nm for cyclohexane. To explain the formation of hollow centers a mechanism is proposed based on the hypothesis that the solid phase is formed via crosslinking and solidification of viscous drop. This mechanism explains the observed linear relationship between core size and particle size.