The Role of Ligand Packing Frustration in Body-Centered Cubic (bcc) Superlattices of Colloidal Nanocrystals.

This paper addresses the assembly of body centered-cubic (bcc) superlattices of organic ligand-coated nanocrystals. First, examples of bcc superlattices of dodecanethiol-capped Au nanocrystals and oleic acid-capped PbS and PbSe nanocrystals are presented and examined by transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). These superlattices tend to orient on their densest (110) superlattice planes and exhibit a significant amount of {112} twinning.

Role of Halides in the Ordered Structure Transitions of Heated Gold Nanocrystal Superlattices.

Dodecanethiol-capped gold (Au) nanocrystal superlattices can undergo a surprisingly diverse series of ordered structure transitions when heated (Goodfellow, B. W.; Rasch, M.

Ordered structure rearrangements in heated gold nanocrystal superlattices.

Small-angle X-ray scattering (SAXS) data reveal that superlattices of organic ligand-stabilized gold (Au) nanocrystals can undergo a series of ordered structure transitions at elevated temperature. An example is presented of a body-centered cubic superlattice that evolves into a hexagonal close-packed structure, followed by the formation of binary simple cubic AB13 and hexagonal AB5 superlattices. Ultimately the superlattice decomposes at high temperature to bicontinuous domains of coalesced Au and intervening hydrocarbon.

Influence of composition on the performance of sintered Cu(In,Ga)Se2 nanocrystal thin-film photovoltaic devices.

Thin-film photovoltaic devices (PVs) were prepared by selenization using oleylamine-capped Cu(In,Ga)Se2 (CIGS) nanocrystals sintered at a high temperature (>500 °C) under Se vapor. The device performance varied significantly with [Ga]/[In+Ga] content in the nanocrystals. The highest power conversion efficiency (PCE) observed in the devices studied was 5.

Chloroform-enhanced incorporation of hydrophobic gold nanocrystals into dioleoylphosphatidylcholine (DOPC) vesicle membranes.

Vesicles of dioleoylphosphatidylcholine (DOPC) formed by extrusion (liposomes) with hydrophobic alkanethiol-capped Au nanocrystals were studied. Dodecanethiol-capped 1.8-nm-diameter Au nanocrystals accumulate in the lipid bilayer, but only when dried lipid-nanocrystal films were annealed with chloroform prior to hydration.

Melting and Sintering of a Body-Centered Cubic Superlattice of PbSe Nanocrystals Followed by Small Angle X-ray Scattering.

The structural evolution of a body-centered cubic (bcc) superlattice of 6.6 nm diameter organic ligand-coated PbSe nanocrystals was studied in situ by small angle X-ray scattering (SAXS) as it was heated in air from room temperature to 350°C. As it was heated above room temperature, the superlattice contracted slightly, but maintained bcc structure up to 110°C.

Reversible solvent vapor-mediated phase changes in nanocrystal superlattices.

Colloidal nanocrystals are being explored for use in a variety of applications, from solar cells to transistors to medical diagnostics and therapy. Ordered assemblies of nanocrystals, or superlattices, are one particularly interesting class of these materials, in which the nanocrystals serve as modular building blocks to construct nanostructures by self-assembly with spatial and temporal complexity and unique properties. From a fundamental perspective, the nanocrystals are simple molecular models that can be manipulated and studied to test statistical mechanical and thermodynamic models of crystallization and disorder.

Solution-liquid-solid synthesis of CuInSe₂ nanowires and their implementation in photovoltaic devices.

CuInSe₂ (CIS) nanowires were synthesized by solution-liquid-solid (SLS) growth in a high boiling solvent using bismuth nanocrystals as seeds. The nanowires tended to be slightly deficient in In and exhibited either cubic or hexagonal crystal structure, depending on the synthesis conditions. The hexagonal structure, which is not observed in bulk crystals, appears to evolve from large concentrations of twin defects.

Thickness-limited performance of CuInSe₂ nanocrystal photovoltaic devices.

This paper reports our latest results using colloidal CuInSe₂ nanocrystal inks to prepare photovoltaic (PV) devices. Thus far, devices with nanocrystal layers processed under ambient conditions with no post-deposition treatment have achieved power conversion efficiencies of up to 3.1%.

Alkyl passivation and amphiphilic polymer coating of silicon nanocrystals for diagnostic imaging.

A method to produce biocompatible polymer-coated silicon nanocrystals for medical imaging is shown. Silica-embedded Si nanocrystals are formed by HSQ thermolysis. The nanocrystals are then liberated from the oxide and terminated with Si-H bonds by HF etching, followed by alkyl monolayer passivation by thermal hydrosilylation.

Hydrophobic gold nanoparticle self-assembly with phosphatidylcholine lipid: membrane-loaded and janus vesicles.

Hybrids of hydrophobic sub-2-nm-diameter dodecanethiol-coated Au nanoparticles and phosphatidylcholine (PC) lipid vesicles made by extrusion were examined by cryogenic transmission electron microscopy (cryoTEM). The nanoparticles loaded the vesicles as a dense monolayer in the hydrophobic core of the lipid bilayer, without disrupting their structure. Nanoparticle-vesicle hybrids could also be made by a dialysis process, mixing preformed vesicles with detergent-stabilized nanoparticles, but this approach led to vesicles only partially loaded with nanoparticles that segregated into hemispherical domains, forming a Janus vesicle-nanoparticle hybrid structure.