Asymmetrical Janus Particles and symmetrical “Core-Shell” Colloids
Over the last decade there have been immense efforts to fabricate monolith and core-shell colloidal materials with tailored structural, optical, and surface properties. The core-shell concept is particularly interesting and provides a variety of opportunities to change properties of colloidal particles. The core-shell concept typically implies tailoring the surface properties of particles, often accomplished by coating or encapsulating them within a shell of a preferred material.
There are plenty of methods for modification of particles by using of different surfactants, silanes and polymers. Most of conventional methods allow uniform or homogenous coating of the particles. On the other hand, one can expect interesting properties from the asymmetrically coated particles i.e. the particles whose surface chemical composition differs on two sides. These particles are often called Janus particles and were suggested by de Genne for the first time.
Janus particles (JPs) i.e. the colloidal particles having different properties (such as charge, polarity, optical and magnetic properties) at opposite sides are an example of synthetic asymmetrical systems. Due to anisotropy of properties, the JPs are unique among other micro- and nanoparticles. Recently, the JPs demonstrated huge potential as drug-carriers, emulsion stabilizers, micro rheological probes and functional elements for design of electronic paper. Moreover, due to asymmetrical structures, the JPs are able to aggregate into fascinating hierarchical structures, thereby, building blocks for complex superstructures.