On Ultrasmall Nanocrystals.

Ultrasmall nanocrystals are a growing sub-class of traditional nanocrystals that exhibit new properties at diameters typically below 2 nm. In this review, we define what constitutes an ultrasmall nanoparticle while distinguishing between ultrasmall and magic-size nanoparticles. After a brief overview of ultrasmall nanoparticles, including ultrasmall gold clusters, our recent work is presented covering the optical properties, structure, and application of ultrasmall CdSe nanocrystals.

Few-layer graphene as a support film for transmission electron microscopy imaging of nanoparticles.

One consistent limitation for high-resolution imaging of small nanoparticles is the high background signal from the amorphous carbon support film. With interest growing for smaller and smaller nanostructures, state of the art electron microscopes are becoming necessary for rudimentary tasks, such as nanoparticle sizing. As a monolayer of carbon, free-standing graphene represents the ultimate support film for nanoparticle imaging.

White light-emitting diodes based on ultrasmall CdSe nanocrystal electroluminescence.

We report white light-emitting diodes fabricated with ultrasmall CdSe nanocrystals, which demonstrate electroluminescence from a size of nanocrystals (<2 nm) previously thought to be unattainable. These LEDs have excellent color characteristics, defined by their pure white CIE color coordinates (0.333, 0.

Structure and ultrafast dynamics of white-light-emitting CdSe nanocrystals.

White-light emission from ultrasmall CdSe nanocrystals offers an alternative approach to the realization of solid-state lighting as an appealing technology for consumers. Unfortunately, their extremely small size limits the feasibility of traditional methods for nanocrystal characterization. This paper reports the first images of their structure, which were obtained using aberration-corrected atomic number contrast scanning transmission electron microscopy (Z-STEM).

Pinned emission from ultrasmall cadmium selenide nanocrystals.

We report pinning of the emission spectrum in ultrasmall CdSe nanocrystals with a diameter of 1.7 nm and smaller. It was observed that the first emission feature ceased to blueshift once the band edge absorption reached 420 nm, though the band edge absorption continued to blueshift with decreasing nanocrystal diameter.

Controlling the reactivity of ampiphilic quantum dots in biological assays through hydrophobic assembly of custom PEG derivatives.

Modifications of the quantum dot (QD) surface are routinely performed via covalent biomolecule attachment, and poly(ethylene glycol) (PEG) derivatization has previously been shown to limit nonspecific cellular interactions of QD probes. Attempts to functionalize ampiphilic QDs (AMP-QDs) with custom PEG derivatives having a hydrophobic terminus resulted in self-assembly of these PEG ligands to the AMP-QD surface in the absence of covalent coupling reagents. We demonstrate, via electrophoretic characterization techniques, that these self-assembled PEG-QDs exhibit improved passivation in biological environments and are less susceptible to unwanted protein adsorption to the QD surface.