Nanocrystal Research

We are interested in nanocrystals for applications in electronics, opto-electonics and catalysis.

Nanocrystals are small crystals that are typically less than 20nm in size. The small size gives them properties that are different from their bulk form, such as enhanced photoluminescence, increased absorption cross-section, improved catalytic performance and discrete energy states similar to an artificial atom. When the nanocrystals are made from semiconducting material, the electrons and holes feel quantum confinement effects and can thus be termed quantum dots. Nanocrystals have wide ranging applications such as solar cells, light emitting diodes, biomedical imaging tags, catalysts and sensors.

We are interested in semiconducting nanocrystals in the form of colloidal quantum dots and their opto-electronic properties. Our recent work has expanded into catalytic nanoparticles such as Pt and understanding their detailed structural forms.

The current research interests of the group in the nanocrystal area is the interfacing with 2D materials. We aim to develop processing methods that can control how nanocrystals are attached to the surface of graphene, BN or MoS2/WS2 2D crystals. This area is important as it extends the functionality of 2D materials for applications in solar cells, chemical sensors, catalysis, photodetectors and light emitting diodes. We primarily use transmission electron microscopy to characterize the structure at the atomic level and develop new treatments that improve the interface between the 2D and 0D structures.

Pt nanoparticles are known for their high catalytic efficiency, which can be expanded hybridizing with MoS2. The image to the right shows an ADF-STEM image of small epitaxial Pt nanocrystals on monolayer MoS2.

The TEM images below show Cobalt Chloride nanocrystals formed on the surface of few layer graphene by direct deposition from a solution precursor. The images are taken using an aberration-corrected transmission electron microscope operated at an accelerating voltage of 80 kV.

In our recent work, illustrated below, we examined PbTe nanocrystals on the surface of suspended monolayer graphene. We were able to see how a ligand exchange process modified the closed-packed array of PbTe nanocrystals into an interconnected aggregation. This helps understand how this chemical treatment influences solar cell performance.

We have studied the detailed atomic structure of unique sub-nm MoS wires fabricated in 2D monolayer MoS2. Recent work investigated the unique torsional rotations that the wires undergo during atom loss and rebonding to edge sites.