We study the assembly of disc shaped nanoparticles in AC electric fields generated by parallel co-planar electrode geometry. The particles are approximately 300nm in diameter and are suspended in an aqueous medium along with a stabilizing surfactant. On application of electric field, the particles form chains and 2D crystals in the bulk. The resulting structure has been analyzed using optical microscopy and electron microscopy by locking the structure in a photopolymerized gel. In addition to the structure formed in the bulk, the particles also assemble in a “brush” like structure at the electrodes. There, large field gradients leads to strong electrohydrodynamic flows and dielectrophoresis. These flows and forces advect particles to the interface, promoting its growth. The thickness of the brush depends strongly on the field strength and field frequency. On increasing the field strength or decreasing the frequency the brush thickness increases. Finally, in the co-planar electrode geometry, we find that electrohydrodynamic forces also occur between particles, primarily disrupting the ordered structures. By changing the electrode geometry from co-planar to perpendicular using parallel plate ITO electrodes, we can create a system where assembly is driven due to these hydrodynamic flows. We compare the resulting structures and order-disorder transitions formed under the two electrode geometries.