Synthesis and Assembly of Janus Particles

Over the years, a wide variety of Janus particles with anisotropy in terms of size, shape and chemical functionality have been explored. Synthesis and self-assembly of such particles has been an area of active research. Owing to their anisotropic nature Janus particles experience highly directional interaction. However, assembly of Janus particles on a surface driven by attractive interaction is an area not yet properly explored. One of the probable reasons for this is that most of the synthesized Janus particles are surface immobilized and suffer from significant damage during dislodgement. Also, the anisotropic particles synthesized by chemical route lack uniformity and monodispersity.
Here we have developed a technique for dislodging surface bound Gold-PS Janus particles by UV induced degradation of a PMMA layer. By this method of dislodging Janus particles no damage to the particles occur. Also, an adhesion promoting layer is not required and PS particles with very thin gold coating (~5 nm) can be dislodged. We have also studied the assembly of the dislodged Janus particles on different surfaces and observed that on such surfaces the particles orient in a preferred fashion depending on the particle-substrate interaction.