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When the size of materials is reduced to the nanoscale dimension, physical and chemical properties can change dramatically. In addition, nanostructures also afford new exciting opportunities of low-cost processing. We are interested in a broad range of nanoscale properties including electronic, photonic, electrochemical, mechanical, catalytic and interfacial properties. Understanding these properties has important technological implications in energy conversion and storage, electronics, biotechnology and environmental technology. We study fundamentals of nanomaterials including nanowires, colloidal nanocrystals and patterned nanostructures, develop low-cost processings and address critical issues in real-world applications.

Advanced materials synthesis and fabrication

We developed a set of synthetic and fabrication techniques to obtain designed nanostructure materials with composition, size and shape control. Our most recently study demonstrated chiral branched nanowires induced by both screw-dislocation and vapor-liquid-solid (VLS) mediated growth, showing the existence of well-known “Eshelby Twist” (Nature Nanotechnology 3, 477-481, 2008). These techniques include:

Energy Storage

Energy storage devices such as lithium ion batteries and supercapacitors are important for portable electronics, vehicle electrification and smart grid. We develop novel nanostructured materials to address critical performance parameters related to energy storage including energy density, power density, safety, cycle and calendar life and cost. Nanostructures have the advantages of facile strain relaxation, enhance power rate but also present a challenge of forming stable electrode-electrolyte interface. Recently we invented silicon nanowire anodes for lithium ion batteries, which offer 10 times higher specific charge capacity of the existing carbon anodes (Nature Nanotechnology 3, 31-35, 2008). The following projects are currently being carried out:


A photovoltaic device consists typically of multiple materials layer including antireflection, transparent electrodes, pn junction absorber, bottom contact and substrate. $/W is the most critical solar cell parameter, which requires both high power efficiency and low cost. Effective sun light management and charge carrier collection are necessary for high power efficiency. Low-cost materials, processing and possibility for large manufacturing are also desirable. We design nanostructured materials, photovoltaic cells and processing to address these challenges.  The following projects are carried out:

Topological Insulator

Following the discovery of two-dimensional topological insulator edge states in HgTe quantum wells at cryogenic temperatures, three dimensional (3D) topological insulators were recently discovered in Bismuth Selenide (Bi2Se3) and related compounds. Theoretical prediction and angle resolved photon emission spectroscopy studies show quantum spin Hall surface states in these 3D topological insulator materials. However, most of the studies thus far have been on bulk size materials and it is challenging to observe directly the surface topological state conduction since its effects are masked by the residue bulk carrier. We are working on topological insulator nanostructures, which can manifest the surface conduction states due their large surface-to-volume ratios. For example, we show transport evidence of topological surface states through periodic Aharonov-Bohm quantum interference effects in layered single-crystalline Bi2Se3 nanoribbons. The following projects are currently carried out:

  • Topological nanostructure synthesis and doping: nanoribbons and nanoplates.
  • Electron transport and devices
  • Potential applications of topological insulator materials

Printable energy and electronic devices

  • Nanoscale paper and textile technologies

    We exploited the novel microstructure of paper and developed nanostructured paper and textile as a platform for a wide range of energy and environmental device applications, including ultracapacitors, batteries, water filtration, microbial fuel cells and printed electronics. The excellent union of nanomaterials such as carbon nanotubes and silver nanowires with paper and textile lead to the success for emerging devices with outstanding performances. We are also interested in the understanding of the fundamental interactions between nanoscale materials such as carbon nanotube and bionanowires with paper and textile fibers.

    The following projects are currently carried out:

    • Graphene-textile and paper for supercapacitors
    • High-performance microbial fuel cells
    • 3D Li-ion textile batteries
    • Printing metal nanowires on paper


Nano-environmental technologies


Nanoscale tools

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