Research in the Liu group is focused on the physical and synthetic chemistries of nanomaterials. We are interested in a wide range of organic and inorganic materials, including but not limited to DNA, graphene, carbon nanotubes, and colloidal nanocrystals.

DNA-templated nanofabrication. By designing the base sequence, a long strand of DNA can be folded into almost any arbitrary shapes. These DNA nanostructures are ideal templates for bottom-up nanofabrication. We explore the catalytic activity of these DNA nanostructures for the etching reaction of SiO₂. The long term goal is to use these DNA nanostructures as nanoscale masks to pattern silicon wafer at the sub-10 nm resolution.

Reaction chemistry of graphene. Graphene, a single layer of graphite, has attracted a lot of attention recently due to its superior electronic and mechanical properties. We are interested in making graphene with both chemical vapor deposition (CVD) and solution exfoliation methods. Another focus is to develop chemistry to covalently modify graphene as well as to etch graphene into specific shapes and edge structures.

Photovoltaic property of individual single-walled carbon nanotubes. Single-walled carbon nanotubes are ideal light absorbing materials for plastic solar cells. However, their true potential in this type of application has never been measured. This is mainly due to the structure heterogeneity in the bulk sample, which contains both metallic and semiconducting nanotubes. We measure the photovoltaic property of individual single-walled carbon nanotubes by constructing a photovoltaic device from just one single-walled carbon nanotube.

Synthesis of colloidal nanocrystals. Colloidal inorganic nanocrystals have found applications in a broad range of fields, including fluorescence labeling, solar cells, and electronics. Traditionally, the syntheses of these materials are exclusively based on the trial-and-error approach. The chemistry of these syntheses is understood mostly at the phenomenological level. We study the colloidal nanocrystal synthesis using classical physical organic chemistry techniques. Of particular interests are the mechanisms of precursor-to-nanocrystal transformation and growth of inorganic nanocrystals. The long term goal is to synthesize multi-component, shape controlled nanostructures by design.