题　目：Room-temperature Ice Growth on Functionalized Nano-graphene/graphite Hybrid Surfaces: Graphene Research Beyond Dirac Fermions
报告人：Dr. Yi Zheng （Department of Chemistry and Graphene Research Centre, National University of Singapore）
时　间：9月25日（周三），下午2：00
地　点：南校区第一实验楼406室

Abstract：
Graphene research has been focusing on its extraordinary electrical, optical, and thermal properties, which originate from the unique linear energyband dispersion close to the Dirac point. Despite being atomic thick, graphene has exceptional mechanical strength and can be readily integrated with functional materials to create novel device concepts and explore new physics. For example, based on graphene-ferroelectric heterostructures, non-volatile memories, low-voltage electronics, transparent conductors and saturable absorbers have been demonstrated recently. In this talk, we provide a different perspective on graphene research utilizing nano-graphene with designed functional groups. We show exotic physical phenomena of room-temperature ice growth and hot vapor frosting on a mesoscopic nano-graphene/graphite hybrid surface, on which the equilibrium liquid-ice phase boundary of 0？C becomes invalid. At ambient conditions, a sprinkle of nano-graphene oxides effectively condenses water nanodroplets and seeds ice wetting layer epitaxy on graphite by in-plane water diffusion. By breaking the temperature equilibrium, we grow micrometer-sized ice crystals by solid deposition of ambient vapor on the ice wetting layer. We demonstrate that ice crystals can be grown at least 50 degrees above the melting point in hot vapor environments of 85？C. Friction force microcopy shows unusual surface properties of these room-temperature ice crystals.
References
1. Y. Zheng et al, Appl. Phys. Lett. 94, 163505 (2009).
2. Y. Zheng et al, Phys. Rev. Lett. 105, 166602 (2010).
3. Y. Zheng, C. L. Su, J. Lu and K. P. Loh, Angew. Chem. Int. Ed. 52, 8708 (2013).

About the speaker:
Dr. Yi Zheng obtained his PhD from National University of Singapore in 2008, working on high-k dielectrics and small molecule semiconductor using the ballistic electron emission microscopy technique. After his graduation, he pioneered in the field of graphene-ferroelectric electronic devices, which have potential applications in non-volatile memories, transparent conductors and low-voltage electronics. He is now studying in water wetting dynamics and ice formation at ambient conditions, in which they use functionalized nano-graphene oxides to seed ice nucleation and control ice growth on hydrophilic-hydrophobic hybrid surfaces.