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The major research themes in our lab include near-infrared (NIR) emitting lanthanide materials for medical and optical applications, photoredox catalysts for efficient chemical conversion, and broadband light-harvesting materials for cost-effective solar energy utilization.

(1) Near-infrared Emitting Lanthanide Materials for Medical and Optical Applications

Certain lanthanide ions, such as ytterbium (III) with emission at 980 nm, are good candidates for sensitive detection of tumor markers. Over the last two decades, some elegant NIR emitting lanthanide complexes with different sensitizers have been studied; however, low emission efficiency and the choice of the UV or near UV light as excitation source are still problematic regarding their applications. The goal of our research is to use a molecular engineering approach to develop novel lanthanide complexes that can be sensitized effectively under the excitation of red light. Specifically, we are using porphyrin and BODIPY dyes as building blocks to make stable and functionalized lanthanide complexes. As demonstrated in the following graph, attaching iodinated BODIPY moieties to a phenanthroline ligand and expanding π-conjugation of porphyrin have great potential to address the aforementioned problems.

(2) Photoredox Catalysts for Chemical Conversion

Photoredox catalysts are often ruthenium and iridium complexes. A physical combination of them with a conventional catalyst such as palladium (II), nickel (II), or copper (II) can promote a variety of chemical conversions including C-C cross-coupling, C-N cross-coupling, and C-H arylation reactions. Depending upon the photocatalysts and conventional catalysts, the reactions can proceed through a single electron transfer mechanism (SET), an energy transfer process (EnT), or a radical mechanism. We are very interested in developing "two-in-one" catalysts, in which organic chromophores are integrated into a conventional catalyst to realize the intramolecular SET or EnT process as shown in the following figure. We found that the BODIPY-functionalized palladium (II) complex catalyzed Sonogashira C-C cross-coupling reactions efficiently.

(3) Broadband Light-harvesting Materials for Solar Energy Utilization

Sunlight is abundant and renewable. It can be converted to other energy storage forms such as electricity or can be used to assist the conversion of carbon dioxide to other value-added products and splitting of water to hydrogen and oxygen. Two challenges are narrow solar spectral coverage of light absorbers and weak adsorption of dyes on electrodes. For example, dye molecules must remain on the surface of Pt-decorated TiO2 nanoparticles during the solar water splitting. We found that 8-hydroxyquinoline is an excellent anchoring group in dye-sensitized solar cells as shown in the following graph. The goal of this research is to construct stable and efficient electrodes using well-designed broadband light absorbers for solar water splitting.

If you are interested in pursuing the aforementioned research in our group and would like to make your contribution to the field, please free to send an email to Dr. He for details. We are accepting self-motivated undergraduate and graduate researchers!

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