Chemistry @ IU

Contact Information:

(812) 855-7178
li23@indiana.edu
Simon 120A
Li Group Website

Professor Li received B.S. in Chemical Physics and M.S. in Theoretical Physics from University of Science and Technology, China, and was awarded his Ph. D. degree (2003) in Physical Chemistry from the University of California, Berkeley under the guidance of Professor A. Paul Alivisatos. He then was a postdoctoral associate in the group of Professor Samuel I. Stupp at Northwestern University, working on synthesis of organic nanostructures.

Professor Li’s research program centers around creating new materials to solve problems of great significance to energy and life sciences. His research group has been working on making efficient, low-cost organic solar cells with self-assembly strategies and developing faster and more sensitive dyes to study brain activities.

Research

Liquid Crystalline Organic Semiconductors for Solar Cells

Improving the electrical conductivity and hierarchical orders in organic semiconductors is essential in making efficient organic devices including solar cells and light emitting diodes. For these purposes, we design aromatic compounds to self-assemble into liquid crystalline phases, study their structural and electrical properties, and test the energy conversion performance of the solar cells made of them. The goal is to identify the parameters dictating the self-assembly, charge transfer and electrical conductivities of the materials, so that we can improve the liquid crystals and enhance the efficiency of the organic devices.

Voltage-Sensitive Dyes for Brain Imaging

Fast, sensitive methods to simultaneously monitor neuronal activities at multiple locations are key to understanding how the brains process information and to developing therapies for neuronal disorders. To facilitate the related work in neurosciences, we develop voltage-sensitive dyes that are capable of converting the voltage changes across neuron membranes during neuron actions to changes in optical signals, so that neuronal activities can be monitored optically.

Bottom-Up Approach to Graphenes

Graphenes contain a single atomic layer of graphite, and are an excellent element for carbon-based electronics. In the form of two-dimensional sheets graphenes are conductors; when cut into narrow ribbons they become semiconductors, with band gap dependent on the width of the ribbons. Currently how to tightly control the width of graphene ribbons and how to produce them in large quantities are two major challenges toward graphene-based electronics. We have developed new methods to build graphenes from benzene derivatives. We are currently studying their physical and chemical properties, as well as their applications in solar cells.

Publications

M. L. Mueller, X. Yan, B. Dragnea, L.-S. Li, "Slow Hot-Carrier Relaxation in Colloidal Graphene Quantum Dots", Nano Letters 11, 56 (2011).

L.-S. Li, X. Yan, "Colloidal Graphene Quantum Dots", J. Phys. Chem. Lett. 1, 2572 (2010).

X. Yan, X. Cui, B. Li, L.-S. Li, "Large, Solution-Processable Graphene Quantum Dots as Light Absorbers for Photovoltaics", Nano Letters 10, 1869 (2010).

X. Yan, X. Cui, L.-S. Li, "Synthesis of Large, Stable Colloidal Graphene Quantum Dots with Tunable Size", J. Am. Chem. Soc. 132, 5944 (2010).

L.-S. Li, "Fluorescence Probes for Membrane Potentials Based on Mesoscopic Electron Transfer", Nano Letters 7, 2981 (2007).

Awards

• 2008 NSF Early Career Award, National Science Foundation
• 2003 MRS Graduate Student Gold Award, American Materials Research Society
• 2002 Technology Transfer Award, US Department of Energy, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Highlights