The 289th MANA & the 126th ICYS Joint Seminar
Dr. Han Zhang & Dr. Shinsuke Ishihara
| Date | October 5, Friday |
| Time | 15:30-16:30 |
| Place | Auditorium, 1F, WPI - MANA Bldg., NAMIKI Site, NIMS |
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15:30-16:00
An ultra-bright and monochromatic electron point source enabled by nanotechnology
With field electron emitters embodied with one dimensional nanotubes and nanowires (NW), flexible transparent displays, high resolution X-ray micro-CTs, battery-driven chemical sensors, and high brightness electron guns for electron microscopes have emerged as practical prototypes.1 Field emission instability, its stringent vacuum requirement together with the high work function of emitter materials left large space for performance improvement to fully exploit their virtues. Here we report a new field emission point source that generates a monochromatic, laser-like collimated electron beam, with brightness over 100 times higher than current technology.2 The electron emission is localized to a few La atoms bonded to the tip apex of a LaB6 nanowire. The nano-structure exhibits a rare coexistence of an extremely low work function (2.07eV, below that of Cs) and high surface inertness, which are incompatible properties for conventional materials. While this new point source can be transformed into planar source through nanowire arrays, an immediate impact will be a record-breaking resolution for electron microscopy instrumentation, which awaits a brighter monochromatic stable electron source since the latest technology from the 1970s.
References
- a) P. Ghosh, et al., J. Am. Chem. Soc. 2010, 132, 4034-4035; b) H. Sugie, et al., Appl. Phys. Lett. 2001, 78, 2578-2580; c) A. Modi, N. Koratkar, E. Lass, B. Wei, P. Ajayan, Nature 2003, 424, 171-174; d) N. Dejonge, Y. Lamy, K. Schoots, T. Oosterkamp, Nature 2002, 420, 393-395.
- a) H. Zhang, Q. Zhang, J. Tang, and L.-C. Qin, J. Am. Chem. Soc. 2005, 127, 2862-2863; b) H. Zhang, Q. Zhang, J. Tang, and L.-C. Qin, J. Am. Chem. Soc. 2005, 127, 22, 8002-8003; c) H. Zhang, Q. Zhang, G. Zhao, J. Tang, O. Zhou, and L.-C. Qin, J. Am. Chem. Soc. 2005, 127, 38, 13120-13121; d) H. Zhang, et. al., Adv. Mater. 2006, 18, 1, 87-91; e) H. Zhang, et. al., Nano Lett. 2010, 10, 3539.
Speaker
Dr. Han Zhang, ICYS-Sengen Researchder, NIMS
Chair
Dr. Jie Tang, MANA PI, MANA, NIMS
16:00-16:30
Tailoring Nano- and Micro-Structure of Copper(II) Oxide toward PGM-free Exhaust Catalyst
Most of chemical energy production technologies such as fossil fuel combustion and fuel cell are relying upon platinum group metal (PGM) catalysts for cleaning toxic exhaust gas and/or promoting electrochemical reactions. While, in turn deposit of PGMs is localized and limited, so that the development of PGM-free catalysts are urgent mission of material science. Herein we report that single crystals of nanometer thickness can, when rationally organized, realize improved catalytic activities, selectivities and durability. We synthesized nanometer-thin single crystals of copper(II) oxide (CuO) with extremely developed {001} surfaces through a ligand-assisted hydrothermal reaction. The CuO crystals spontaneously intersected one another to form a highly porous micro-assembly, maximizing the effective {001} surfaces for the purification of nitrogen monoxide (NO). The conformation of the CuO micro-assembly not only permitted the smooth access of reactants to the {001} surfaces but also strongly suppressed thermal agglomeration of the catalytic center. Consequently, the CuO micro-assembly outperformed different CuO materials in durability and even rivaled an equivalent weight of PGM nanoparticles in the purification of NO. Our results indicate that adequate organization of nanometer-thin single crystals is a powerful approach toward high-performance catalysts without using precious-group metal elements.
Speaker
Dr. Shinsuke Ishihara, ICYS-MANA Researcher, NIMS
Chair
Dr. Kenjiro Miyano, Managing Director, ICYS, NIMS