Templating CdSe tetrapods at the air/water interface with POPC lipids.

Surfactants have been widely used as templating agents to pattern the orientation of nanoparticles of various conformations. Here we report the use of a lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), as a template to order CdSe tetrapods (TPs) at the air/water interface using a Langmuir-Blodgett trough. The surface pressure versus area isotherms for CdSe TPs and CdSe TPs/POPC are examined and monitored by Brewster angle microscopy (BAM). The transferred thin films are further characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Initially disc-like structures containing randomly oriented TPs form during solvent evaporation. Upon decreasing surface area, these discs merge into larger continental structures. In a mixed CdSe TPs/POPC system, these discs organize into wire-like networks upon compression. We detail how lipid molecules can be used to direct the two-dimensional assembly of TPs.