Title: Kenan Distinguished Professor
Phone: (919) 962-0307
Liquids and gases confined in nanometer-sized pores often exhibit unique properties that are not seen in the bulk. For instance, gases and liquids that are normally isotropic in bulk, can become anisotropic inside a nanometer-sized container if the shape of the container is nonspherical (Science 294, 1505 (2001)); the hydrophobic character of a surface can become hydrophilic with change of temperature when water is nanoconfined by such a surface (Science 322, 80 (2008)); molecular transport of liquids, ionic transport of electrolyte, and gas diffusion could all behave very differently when passing through nanometer-sized pores (Hummer et al. Nature 414, 188 (2001); Holt et al. Science 312, 1034 (2006)). We are interested in revealing novel phenomena of such nanoconfined fluids and seek fundamental understandings of the physics involved. For instance, we are interested in finding out at what nanometer scale qualitative changes take place for a given physical property. Such endeavor is not only of fundamental importance but is also of direct relevance to important applications. Some of these applications we have been pursuing include hydrogen storage, shale gas, batteries, supercapacitors, and ion separations.
Interactions of liquid or gas molecules with nanomaterial surfaces are also of our main interests. Through control of nanomaterial surface structure we have been able to optimize important properties. For instance, catalytic efficiency of titania nanotubes can be optimized to achieve high decontamination rate of chemical warfare agents. Surface control can enhance the dielectric response of nanoparticle/liquid interfaces dramatically, allowing novel applications such as contrast agents via electromagnetic imaging for oil and gas exploration. Another important example of molecule/nanoparticle interaction we have been pursuing is the interaction between general anesthetics with proteins (natural nanomaterials). Here, the surface of proteins does not simply serve as a rigid surface. Structural and dynamic changes of proteins upon adsorption of anesthetic molecules make such processes very intriguing. We are actively investigating whether such interaction is controlled predominantly by enthalpic or entropic contributions. This is a crucial issue toward understanding the mechanism of general anesthesia, which is still lacking even after over a century in medical practice. Protein/metal oxide nanoparticle interactions are also being explored in our lab where surface structure and thermodynamics play crucial roles.
Finally, a long term research interest of the Wu group is the characteristics of supercooled liquids including metallic supercooled liquids. We are interested in discovering the dynamic characteristics that are essential for supercooled liquid undergoing glass transition (Nature 402, 160 (1999); PRL 91, 265502 (2003); PRL 99, 095501 (2007)). Structures, dynamics, and mechanical properties have been investigated both at atomic and macroscopic scales. The ultimate goal is the understanding of the nature of glass transition, one of the fundamental unsolved problems in condensed matter physics.
The primary research tool in our group is nuclear magnetic resonance (NMR). We develop unique NMR tools for our unique problems such as high-pressure NMR for gas adsorption, NMR-based isotherms for studying molecular interactions and thermodynamics, high-temperature NMR for studying metallic supercooled liquids, and device-based NMR for in-situ study of electrochemical processes. We synthesize most of the materials in our lab and we seek collaborations with leading materials research groups around the world for new materials. We have in our lab NMR, thermal analysis, and dielectric measurement tools and have access to a very broad range of materials characterization tools at UNC.
“Temperature dependence of lysozyme hydration and the role of elastic energy”
Hai-Jing Wang, Alfred Kleinhammes, Pei Tang, Yan Xu, Yue Wu, Physical Review E 83, 031924 (2011).
“NMR Methods for Characterizing the Pore Structures and Hydrogen Storage Properties of Microporous Carbons”
R. J. Anderson, T. P. McNicholas, A Kleinhammes, A. M. Wang, J. Liu, and Yue Wu, Journal of the American Chemical Society 132, 8618-8626 (2010).
“Temperature-Induced Hydrophobic-Hydrophilic Transition Observed by Water Adsorption”
Hai-Jing Wang, Xue-Kui Xi, Alfred Kleinhammes, and Yue Wu, Science 322, 80-83 (2008).
“Correlation of Atomic Cluster Symmetry and Glass-Forming Ability of Metallic Glass”
Xue-Kui Xi, Li-Long Li, Bo Zhang, Wei-Hua Wang, and Yue Wu, Physical Review Letters 99, 095501 (2007).
“Crossover of Microscopic Dynamics in Metallic Supercooled Liquid Studied by NMR”
Lilong Li, Jan Schroers, and Yue Wu, Physical Review Letters 91, 265502 (2003).
“Confinement Effect on Dipole-Dipole Interactions in Nanofluids”
J. Baugh, A. Kleinhammes, D. Han, Q. Wang, Y. Wu, Science 294, 1505-1507 (2001).
“Electronic Structures of Single-Walled Carbon Nanotubes Determined by NMR”
X. -P. Tang, A. Kleinhammes, H. Shimoda, L. Fleming, K. Y. Bennoune, S. Sinha, C. Bower, O. Zhou, Y. Wu, Science 288, 492-494 (2000).
“Diffusion mechanisms in metallic supercooled liquids and glasses”
X.-P. Tang, Ulrich Geyer, Ralf Busch, William L. Johnson, and Yue Wu, Nature 402, 160-162 (1999).
“Sharp Feature in the Pseudogap of Quasicrystals Detected by NMR”
X.-P. Tang, E. A. Hill, S. K. Wonnell, S. J. Poon, and Y. Wu, Physical Review Letters 79, 1070-1073 (1997).
“New Hydrogen Distribution in a-Si:H: An NMR Study”
Y. Wu, J. T. Stephen, D. X. Han, J. M. Rutland, R. S. Crandall, and A. H. Mahan， Physical Review Letters 77, 2049-2052 (1996).