Systems Chemistry with the Nanocluster Ensemble

As the KiPAS Chief Researcher, chemistry Professor Nakajima launched research activities and is focusing together with Researcher Doctor Shibuta on nanocluster assemblies, which are higher order hierarchical functional materials originating from nanoclusters. The team is clarifying the physical properties of nanocluster assemblies fabricated with high order and uniformity as “system chemistry” and is advancing with research aimed at establishing a foundation for new nano-functional material science.
“Nanoclusters are aggregations of several atoms to several thousand atoms. Technology that makes it possible to freely build these nanoclusters is required, but we are endeavoring to develop a new technique called magnetron sputtering to do this. However, ahead of this, our research will next focus on clarifying nanocluster assembly structures and on how nanoclusters actually accumulate to obtain new functions. In other words, our research is focused on the theme of nanoclusters, but more specifically, we are attempting to discover the appeal of nanoclusters when they are aggregated to create new materials with properties that go beyond those of the individual nanoclusters themselves.”
For this purpose, the researchers are first advancing with efforts to enhance technology for the precision synthesis of functional nanoclusters and to develop a technique for the production of uniform thin films as substrates for their deposition. They are also creating highly ordered nanocluster accumulated films. In addition, the team is engaged in research to create various functions through ordered accumulation by combining highly sensitive techniques for measuring microscopic regions and pursuing the structures, electronic properties, and dynamics of those regions.
“Our goal is to clarify surface functionality, electron functionality, and electron dynamics through photoelectron spectroscopy using a unique approach that utilizes extremely short optical pulses of a femtosecond laser to capture electron movement in real time. More specifically, first we irradiate a femtosecond laser on a surface, and when we do that, the electrons enter an excited state in which they exhibit functionality from that point forward. Then, when the electrons in that excited state are probed by another femtosecond pulse, ejecting electrons to the outside of the surface. We’re using this unique technique that we call time-resolved photoelectron spectroscopy to search for the functionality of nanocluster accumulated thin films.”
As part of this research, the team is also developing original techniques to create nanoclusters as well as new methods for evaluation. One of those techniques utilizes technology to build surface nanostructures by sorting clusters produced in a vapor-phase by size and composition and then vapor-phase depositing the clusters in a non-destructive manner onto a substrate.
“This is what we call soft-landing technology. It’s a technique that we pursued on our own, and first we created a device that enables us to non-destructively align nanoclusters on a surface, after they have been selectively synthesized in a gas phase.
Then the substrate decorated by functional nanoclusters is transferred to a next measurement stage that performs photoelectron spectroscopy. That’s the kind of system that we’ve been totally developing on our own efforts. We’re developing a system that can be used to observe how electron behaves or carries on the precisely fabricated functional surface system, and we’re aiming to know how these observed information contribute to the practical functionality on the nanodevices."
Advancements in the research being promoted by researchers, professor Nakajima and doctor Shibuta, are expected to result in the creation of novel properties of nanocluster assembly materials including, for example, the creation of microscopic magnetic units and the development of high performance charge separating films and high-activity catalysts that are highly selective. These advancements are also expected to bring about further contributions to the areas of nanoengineering and biomaterial science.