Novel Microsphere-Nanowire Colloidal Particles: Synthesis and Characterization

We show the fabrication and characterization of a novel type of colloids: microsphere-nanowire hybrid particles. Nanowires in the form of metals or metal oxides (through post-processing) are synthesized using electrodeposition in nanoporous templates, and the size of them are in the range of 50-200 nm in diameter and 200 nm-4 µm in length. Micron-sized particles are either polystyrene (PS) or silica with the diameter ranging from 1 to 10 µm. PS particles are synthesized by emulsion polymerization, while silica particles by sol-gel process. During microsphere formation process, nanowires are added into the suspension to initiate self-assembly to obtain hybrid microsphere-nanowire structures. Bimetallic nanowires are also fabricated with their surface being selectively modified, and then assembled onto microspheres to enable functionalization of the hybrid colloidal particles. Surface coverage of nanowires on microspheres can be controlled by appropriate concentration ratio between the two distinct components. The microsphere-nanowire structures are characterized using optical microscopy, electron microscopy (SEM and TEM) along with EDS. These hybrid colloidal particles have great potential in such applications as photonic crystals, advanced coating materials, novel sensors, or controlled delivery.