Micron Sized Crystallites from Films Embedded with Ag Nanocrystals

Abstract

One key pursuit over the past decade in the field of nanoscience has been the purposeful construction and characterization of micron and millimeter-scale materials composed of metallic nanocrystals, sometimes termed quantum dots or ?artificial atoms.? These artificial atoms, with diameters on the order of 5 to 25 nm, hold unique properties that are different from the isolated atom and that of the bulk solid, and thus represent a novel class of building blocks for creating solid state materials. In our work, the artificial atoms are 5 nm Ag nanocrystals, which are used to make thin films. These films are in turn used as a new starting material for constructing micron-scale polycrystalline superlattices or crystallites. First, Ag nanoparticles are densely packed into a film at the organic-aqueous interface, a method developed in our laboratory. The free energy of the system is lowered when these nanocrystals spontaneously assemble at the interface. Second, the resulting film is then displaced from the interface and manipulated to allow larger scale solid materials to form. These crystallites are characterized with Differential Interference Contrast Microscopy, Atomic Force Microscopy, Scanning Electron Microscopy and Transmission Electron Microscopy. Our significant findings are that (1) amber-colored crystallites on the 5 to 25 micron scale are easily created (and sometimes the preparation yields cylindrical rods), and (2) these amber colored crystallites and composed of individual Ag nanocrystals.