Synthesis Assembly Modeling Optics Electronics Magnetics Catalysis
Like atoms or molecules, but in the next level of hierarchy, nanocrystals can behave as artificial atoms serving as the building blocks to new designer solids. We develop routes to manipulate nanocrystals into one-dimensional wires as well as well-ordered 2D monolayers and 3D colloidal crystalline solids with symmetric and asymmetric building blocks. We develop processes to assemble NC superlattices over large areas, to form uniform layers of controlled thickness, or superlattices structured periodically on the micron scale in NC thickness. We are excited to probe more deeply how interactions between nanocrystals give rise to new collective phenomena particularly electronic transport, photoconductivity, and magnetic exchange coupling.
Single-Component Self-Assembly
Smectic Nanorod Superlattices Assembled on Liquid Subphases: Structure, Orientation, Defects, and Optical Polarization
(a) Horizontally aligned superlattice of CdSe/CdS NRs formed on EG with an electron diffraction pattern collected from the same location. (b) Vertically aligned multilayer superlattice of NRs also formed on EG with the corresponding electron diffraction pattern collected from the same location. Cartoons indicate the structure of the assemblies.
Binary Self-Assembly
Structural diversity in binary nanoparticle superlattices
The superlattices are assembled from a, 13.4 nm γ-Fe2O3 and 5.0 nm Au; b, 7.6 nm PbSe and 5.0 nm Au; c, 6.2 nm PbSe and 3.0 nm Pd; d, 6.7 nm PbS and 3.0 nm Pd; e, 6.2 nm PbSe and 3.0 nm Pd; f, 5.8 nm PbSe and 3.0 nm Pd; g, 7.2 nm PbSe and 4.2 nm Ag; h, 6.2 nm PbSe and 3.0 nm Pd; i, 7.2 nm PbSe and 5.0 nm Au; j, 5.8 nm PbSe and 3.0 nm Pd; k, 7.2 nm PbSe and 4.2 nm Ag; and l, 6.2 nm PbSe and 3.0 nm Pd nanoparticles. Scale bars: a–c, e, f, i–l, 20 nm; d, g, h, 10 nm. The lattice projection is labelled in each panel above the scale bar.
Heterodimer Self-Assembly
Self-Assembly of Atomically Aligned Nanoparticle Superlattices from Pt–Fe3O4 Heterodimer Nanoparticles
Ligand Assisted Self-Assembly
Nanocrystal Core Size and Shape Substitutional Doping and Underlying Crystalline Order in Nanocrystal Superlattices
Schematic representation of the inorganic core and whole NC dimensions for different sized (a) spherical NCs and (b) spherical and cubic NCs where a similar overall size can be achieved using bulky ligands as well as schematic representation of self-assembled monolayers of (c) single component SL, (d) substitutional doping, (e) size substitutional doping, and (f) shape substitutional doping in NC SLs.
Micro-fluidic Self-Assembly
Monodisperse Nanocrystal Superparticles through a Source–Sink Emulsion System
Schematic of the fabrication of monodisperse NC superparticles. Step 1: Generation of a monodisperse toluene-in-water “source” emulsion using droplet microfluidics. Each droplet contains a dispersion of NCs with initial volume fraction ϕi. Step 2: Introduction of a secondary hexadecane-in-water “sink” emulsion. The hexadecane droplets are 3 orders of magnitude smaller than the toluene droplets. Step 3: The sink emulsion swells with toluene from the source emulsion, shrinking the source droplets and ultimately forming NC superparticles. Step 4: After washing away the swollen sink emulsion, the NC superparticles appear monodisperse and spherical.