Research interests of my group lie in the development of new materials based on the self-assembly of colloidal nanostructures. These self-assembled NC superstructures and their carbon-based derivatives show a great promise for energy conversion and storage applications. The primary goal is to understand how the structure and interface/surface properties NC superstructures affect material properties and device performance.

 

1. Synthesis of monodisperse colloidal nanostructures

Low-dimensional nanostructures, such as 0D NCs, 1D nanowires, and 2D nanosheets, are the subject of intense research because of their unique size- and shape-dependent physiochemical properties. These low-dimensional nanostructures are also the main building blocks for bottom-up construction of mesoscopic/macroscopic superstructures. The synthesis of  high-quality, monodisperse nanostructures is the key to the realization of superstructures.

 

 

2. Self-assembly of NC superstructures

The ability to  assemble higher-ordered superstructures from colloidal NCs with precisely controlled compositions and morphologies is crucial for the development of NC-based functional devices. NP superlattices are also a fundamentally important platform for exploring electronic coupling, charge transport, and energy transfer of NP ensembles.

 

 

3. Ordered mesoporous few-layer-graphene frameworks derived from NC superlattices

The native ligands (oleic acid and/or oleylamine) tethered to the surface of metal oxide NCs can be converted to an ultrathin (~2 nm) carbon shell while preserving NC ordering when the NC superlattices are subjected to calcination under inert atmosphere. The subsequent acid leaching followed by graphitization at higher temperatures can lead to highly ordered mesoporous frameworks constructed from a few layers of graphene. The pore size of mesoporous graphitic carbon framewroks is tunnable in the range of 5-20 nm by varying the size of metal oxide NCs.

 

 

4. NC superstructures and their carbon-based derivatives for energy applications

Self-assembled NC superstructures and their carbonaceous derivatives are of both fundamental and technological importance for energy conversion (electrocatalysis) and storage devices (supercapacitors, lithium-ion batteries, Li-S batteries, etc.), the performance of which can be optimized by engineering the structure of NC assemblies. More importantly, the well-defined structural features of self-assembled NC superlattices render them a fundamentally important platform for investigating structural evolution of individual active nanoparticles during the electrochemical process.

 

4.1 Interconnected, carbon-coated NC superlattices for Li-ion batteries

 

4.2 Tubular monolayer superlattices of hollow Mn3O4 NCs for oxygen reduction

4.3 Mesoporous graphene frameworks for supercapacitors

 

4.4 Single-atom-decorated cubic graphene frameworks for oxygen reduction

 

4.5 S@mesoporous graphene spheres for Li-S batteries