Synthesis of Hollow Nanoparticles by Template Coating in Low-Pressure Plasma

Hollow particles are of great interest for the encapsulation of materials such as drugs, dyes and cosmetics in order to controllably release them over time. These particles are commonly produced by a two-step process that starts with coating the surfaces of templates to a desired thickness followed by chemical dissolution or calcination of the template. This process has been employed for a variety of materials including ceramics, polymers, and metals. In our previous work [1], we developed a plasma-based process for depositing plasma polymers of various thicknesses onto micro- and nanoparticles. Here we report the preparation of hollow nanoparticles by a two-step process: (a) a particle that serves as a template is coated with amorphous hydrogenated carbon in a low pressure plasma; and (b) the core particle is then dissolved to produce a hollow nanoshell. TEM images depict the thickness and the uniformity of the adherent polymer coatings. In order to determine the permeability of the shell, coated KCl particles are dissolved in water and the conductivity of the solution is measured as a function of time. These nanoshells exhibit a delayed release response, which can be controlled via the deposition time of the film. [1] J. Cao and T. Matsoukas, Journal of Applied Physics 92, 2916 (2002)