Location: the meeting room on 3rd floor of Catalyst Building
Time: 2014.08.18(Monday) 2:00pm
Lecturer: Prof. Yangyang
College of Chemistry and Chemical Engineering & State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China (since Apr. 2013).
Abstract:
Diffusion is a spontaneous migration of particles due to thermal motion and an exclusive mode for atom transfer in a solid. In this presentation, a strategy is introduced for tailoring low-dimensional inorganic nanostructures by regulating the thermal diffusion at heterogeneous solid–solid interfaces. First, core–shell nanostructures derived from ZnO single-crystal nanowire arrays are used as an example to reveal the mechanisms of solid-state reactions at core–shell interfaces of one-dimensional nanostructures, in which ZnO–Al2O3, ZnO–TiO2, ZnO–SiO2, and ZnO–polycrystalline ZnO coaxial core–shell nanowires are respectively constructed by atomic layer deposition (ALD). The uniform and conformal features of ALD lead to precise thickness control of the shells on each individual nanowire. Due to the interdiffusion distinctions of the different systems in interfacial reactions at elevated temperatures, hollow, porous and multitwinned ternary oxide nanowires are designed and fabricated. In particular, we present our understandings on void evolution induced by unbalanced diffusion. The roles of desorption, stress, and/or defects are discussed on void evolution and nanotube formation. Our results demonstrate that the stress- and defects-engineered diffusion mechanisms can be used to specifically design porous nanostructures and to prepare nanocomposites decorated by metal nanoparticles, which will open up a new window in exploitation of the solid-state diffusion at the nanoscale. Finally, we extend this strategy to axial multilayered metal nanowires. The Ni/Pt interface is found to be an efficient platform for enhancing the outward diffusion of Ni during oxidation and for manipulating the nucleation of vacancies in Ni, which intrinsically behaves in an uncontrolled manner. As a result, nanopeapods consisting of highly ordered, wavy NiO nanopods embedded with equally spaced Pt nanopeas are fabricated by the oxidation of multisegmented Ni/Pt nanowires at low temperatures.
Introduction:
Dr. Yang Yang is a professor in College of Chemistry and Chemical Engineering & State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China (since Apr. 2013). He obtained B.Sc. (1997) and Ph.D. (2003) degrees in chemistry from Nanjing University, China. From Oct. 2004 to Oct. 2006, he was awarded as a JSPS long-term research fellow at the University of Hyogo, Japan, focusing on the self-assembly of nanoparticles. From Nov. 2006 to Mar. 2010, he was a postdoctoral researcher at the Max Planck Institute of Microstructure Physics, Germany, investigating atomic layer deposition and solid state reactions at the nanoscale. From Apr. 2010 to Mar. 2013, he worked as a group leader in the Laboratory for Nanotechnology at the Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany, focusing on doping of inorganic nanostructures as well as fabrication and applications of functional nanocomposites. Until now he has published more than 60 peer-reviewed journal publications including Angew. Chem. Int. Edit, JACS, Small, Nano Lett., ACS Nano, Chem. Mater. et al. His research interests include the reactivity and stability of nanowires and nanotubes, nanoscale interfacial diffusion, atomic layer deposition, and self-assembly of nanomaterials.
Recent publications (*corresponding author)
1. R. Kozhummal, Y. Yang,* F. Güder, U. M. Kü？ükbayrak, M. Zacharias, ACS Nano, 2013, 7, 2820–2828.
2. R. Kozhummal, Y. Yang,* F. Güder, A. Hartel, X. Lu, U. M. Kü？ükbayrak, A. Mateo-Alonso, M. Elwenspoek, M. Zacharias, ACS Nano, 2012, 6, 7133–7141.
3. Y. Yang,* L. Liu,* F. Güder, A. Berger, R. Scholz, O. Albrecht, M. Zacharias, Angew. Chem. Int. Ed., 2011, 50, 10855–10858.
4. Y. Yang,* R. B. Yang, H. J. Fan, R. Scholz, Z. Huang, A. Berger, Y. Qin, M. Knez, U. G？sele, Angew. Chem. Int. Ed., 2010, 49, 1442–1446.
5. Y. Yang,* D. S. Kim, Y. Qin, A. Berger, R. Scholz, H. Kim, M. Knez, U. G？sele, J. Am. Chem. Soc., 2009, 131, 13920–13921.
6. Y. Yang,* R. Scholz, H. J. Fan, D. Hesse, U. G？sele, M. Zacharias, ACS Nano, 2009, 3, 555–562.
Contacts: Gold Catalyst Research Centre Yuan Hexin (82463017)