Letian to join Purdue

On August 2017, Letian is moving to Purdue University, Davidson School of Chemical Engineering as an assistant professor to start his independent scientific research career. The Dou group will focus on hybrid materials and nanomaterials for energy harvesting and electronics. Several graduate student and postdoc positions are available. Visiting students/scholars are also welcomed. Send CV to dou10@purdue.edu.

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Letian’s paper on PNAS

Our paper about inorganic halide perovskite nanowire multi-color heterojunctions has been published on PNAS. Halide perovskites are promising semiconductor materials for solutionprocessed optoelectronic devices. Their strong ionic bonding nature results in highly dynamic crystal lattices, inherently allowing rapid ion exchange at the solid–vapor and solid–liquid interface. Here, we show that the anion-exchange chemistry can be precisely controlled in single-crystalline halide perovskite nanomaterials when combined with nanofabrication techniques. We demonstrate spatially resolved multicolor CsPbX3 (X = Cl, Br, I, or alloy of two halides) nanowire heterojunctions with a pixel size down to 500 nm with the photoluminescence tunable over the entire visible spectrum. In addition, the heterojunctions show distinct electronic states across the interface, as revealed by Kelvin probe force microscopy.

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Zhiqiang’s paper on JACS

Zhiqiang’s paper about Cu@Au core−shell nanowires has been published on JACS. Copper nanowire networks are considered a promising alternative to indium tin oxide as transparent conductors but are not stable in air. In this work, we developed the synthesis of ultrathin Cu@Au core−shell nanowires using trioctylphosphine as a strong binding ligand to prevent galvanic replacement reactions. The epitaxial overgrowth of a gold shell with a few atomic layers on the surface of copper nanowires can greatly enhance their resistance to heat (80 °C), humidity (80%) and air for at least 700 h, while their optical and electrical performance remained similar to the original high-performance copper.

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Fan’s paper published on JACS

Fan’s paper on Cu nanowire synthesis using organic free radicals has been published on JACS. In this work, we report a new, general synthetic approach that uses heat driven benzoin radicals to grow ultrathin copper nanowires with tunable diameters. In-situ temperature dependent electron paramagnetic resonance (EPR) spectroscopic studies show that the active reducing agent is the free radicals produced by benzoins under elevated temperature. The nice thing is that the reducing power of benzoin can be readily tuned by symmetrically decorating functional groups on the two benzene rings. The controllable reactivity gives the carbon organic radical great potential as a versatile reducing agent that can be generalized in other metallic nanowire syntheses.

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