(351b) Engineering Anisotropic Colloids for Magnetic Assembly

Directed assembly of surface-anisotropic (sa) colloids has gained immense interest in recent years as a potential pathway in controlling and achieving hierarchical colloidal structures. Structures obtained from the assembly of surface-anisotropic particles in external fields are interesting for photonic applications.

Sulfate-terminated polystyrene (PS) colloids are surface-modified using iron deposition in high vacuum and oxygen-rich environments to obtain magnetic Janus colloids. Low concentrations of iron and iron-oxide Janus colloids are subjected to a permanent magnetic field where they are magnetized depending on their cap composition. The assembly behavior of the Janus colloids is studied as a function of (i) degree of oxidation, (ii) cap size, (iii) cap thickness, and (iv) solution medium composition. Three types of assembly behavior are observed varying from no assembly via staggered chains to double chains. Subsequently, staggered and double chains are isolated and characterized using Scanning Electron Microscopy, Transmission Electron Microscopy, and X-ray Energy Dispersive Spectroscopy.