Editors : D.B. Mitzi, D. Ginley, B. Smarsly, D.V. Talapin
a1 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A.
We chemically synthesized charged gold nanoparticles coated with hydrophobic organic molecules, which are stable in hexane but unstable in toluene. If a hexane droplet with charged gold nanoparticles is mixed with a larger toluene droplet, they immediately float to the airtoluene interface forming a monolayer of close-packed gold nanoparticles. The monolayer can be deposited to any substrate simply by the solvent molecules' evaporation with no limit in size and without using any sophisticated instrument. As a demonstration, we fabricated a very large monolayer of close-packed gold nanoparticles covering the whole surface of a 3 inch silicon wafer. We further showed that excess organic ligand molecules do not affect the charged gold nanoparticles' property of floating to and forming a monolayer at the air-toluene interface. However, these very slowly evaporating molecules remain on a substrate, affect the two-dimensional ordering, and significantly reduce the contrast in scanning electron microscopy.