New Nanomaterial Chemistry of Superstructured Nanoclusters

Atsushi Nakajima (Professor, Department of Chemistry)

Creating new concepts for materials is one of the important perspectives in chemistry. The synthesis of nanoscale atomic groups with near-spherical, cage-like shapes, or nanostructures where the same units are stacked in multiple layers, is a cutting-edge research theme in “nanocluster science.” In my laboratory, using the unique, one-of-a-kind research equipment shown in Photo 1, we are pioneering the creation of nanoclusters with superstructures, such as cage and multilayer structures.

One of the important concepts in the material world is “hierarchy.” Atoms and molecules, as well as solids and liquids, are part of the “hierarchical structure” of matter. This hierarchical structure of matter extends in both smaller and larger directions. Atoms are composed of electrons, protons, and neutrons; furthermore, protons and neutrons are composed of elementary particles such as quarks. The hierarchy in the larger direction continues to the Earth (a planet), the solar system, the galaxy, and the universe. In the material world, new concepts emerge each time a new hierarchical level is crossed. Research into the new material group of “nanocluster science” can be seen as an idea to create a new hierarchical level between atoms/molecules and solids/liquids.

We have discovered that a cage-like nanostructure, as shown in Figure 1, can be formed from 16 silicon atoms and one titanium metal atom. This functions as a quantum dot, serving as a unit for magnetic memory or light emission. Furthermore, it is considered to be a type of superatom, where atoms assemble and behave as a new unit. In addition to this, we have also discovered superatoms made of one boron atom and 12 aluminum atoms, and these cage-like atomic assemblies, or superatoms, are opening up a new world of materials.

Furthermore, by skillfully reacting metal atoms with organic molecules, a one-dimensional nanostructure with a multilayer structure, as shown in Figure 2, is formed. Nanowire materials, where a simple repeating structure is formed in only one direction, become a stage for expressing new quantum properties in which electrons, spins, and atomic nuclei arrangements cooperate. For example, we have found that forming a multilayer structure with vanadium metal and benzene molecules creates a “cluster magnet.” This cluster magnet exhibits ferromagnetism at room temperature, so by arranging these magnets, it may be possible to create magnetic storage materials with a density more than 100 times higher than what is currently available. Nanoclusters are a group of materials at a new hierarchical level that transcends the periodicity of the elements, and there are growing expectations for the emergence of new functions.

Photo 1: An example of our original research equipment.

We are conducting world-class performance measurements primarily using vacuum equipment.