This research result was achieved by a team headed by Dr. Yusuke Yamauchi, a MANA Scientist at the NIMS International Center for Materials Nanoarchitectonics (MANA; Director-General: Masakazu Aono), and Dr. Hu Ming, who is a Postdoctoral Researcher at MANA.
Prussian blue has a high cesium adsorption capacity, on the same level as natural minerals such as zeolite. To date, various attempts have been made to increase the adsorption capacity of Prussian blue by increasing its surface area by refinement/fabrication of mesoporous materials. However, with the conventional synthesis process for mesoporous material, the crystallinity of Prussian blue was greatly reduced by refinement, and the expected increase in surface area was not obtained. Therefore, the development of a new synthesis technique which increases the area of Prussian blue while maintaining its crystallinity, and thereby maximizes its adsorption capacity, was indispensable.
In this work, the NIMS researchers succeeded in fabricating nanoporous Prussian blue using a new etching type synthesis method. As illustrated in the accompanying figure, it was possible to induce spontaneous formation of an extremely large number of nanopores in particles of Prussian blue by adding water-soluble macromolecules to a solution in which nanoparticles of Prussian blue had been dispersed and stirring the resulting solution under an acidic condition.
The surface area showed a high value of more than 330m2/g, which is the largest area reported for Prussian blue until now and is also more than 10 times larger than the area of commercial Prussian blue particles. In a cesium adsorption experiment using this mesoporous Prussian blue, cesium adsorption was more than 8 times greater than that with the commercial Prussian blue. It is thought that a similar adsorption capacity can be expected in seawater. In order to further increase the cesium adsorption capacity of Prussian blue by metal replacement, the research team is attempting to apply this technique to Co-Fe Prussian blue analogues, etc. In the future, tests of these materials as adsorbents will be conducted, and development will be carried out with the aim of simplifying the process. As a result, development approaching practical applications, beginning with application to mass production, is expected.
This result was obtained as part of the research topic “Nanoscale Design of Nanomaterials toward Next Generation of Magnetic Recording Media” (Researcher: Yusuke Yamauchi), in the research area “Nanosystems and Emergent Functions” (Research Supervisor, Yoshihito Osada, RIKEN, Advanced Science Institute, Group Director), which is an individual research-type PRESTO Project (PRESTO: Precursory Research for Embryonic Science and Technology) of the Japan Science and Technology Agency (JST). This achievement will be announced on December 19, 2011 (local time) in the online edition of the Angewandte Chemie International Edition (published by the German Chemical Society).