Summary of Research Project Results under JSPS FY2002
"Research for the Future Program"

1.Research Institution Keio University
2.Research Area Physical and Engineering Sciences
3.Research Field Photoscience
4.Term of Project FY 1998 - FY 2002
5.Project Number 98P01203
6.Title of Project Development of Sub-nanosized Aggregates Having Novel Optical Properties

7.Project Leader
Name Institution,Department Title of Position
Atsushi, Nakajima Keio University, Faculty of Science and Technology Professor

8.Core Members

Name Institution,Department Title of Position
Koji, Kaya Okazaki National Research Institutes, Institute for Molecular Science Director General
Shinji, Hayashi Kobe University, Faculty of Engineering Professor
Masaaki, Fujii Okazaki National Research Institutes, Institute for Molecular Science Professor

9.Summary of Research Results

In our project, we have aimed at the creation of sub-nanosized aggregates having novel optical properties on the basis of fundamental understanding about electronic and geometrical structures to develop new optoelectronic materials, and we have investigated three following themes.
(1) luminescent semiconductor nano-cluster/nano-crystal    Two different approaches of gas phase and matrix, towards sub-nanosized silicon/germanium particles, were taken to evaluate their optical properties quantitatively. These works have successfully revealed fundamental understanding of quantum size effect on luminescence and the substantial contribution of silicon /germanium oxides. Based on the luminescence mechanism of nano-sized semiconductors, we have proposed two concepts for optical devices: (a) emission enhancement with microcavity structure by silicon nano-crystals and (b) doping of rare earth atoms for efficient energy transfer or for formation of a novel caged structure.
(2) creation of novel organometallic nano-cluster    In gas phase reactions, we have discovered various geometrical structures of organometallic nano-cluster, such as low-dimensional sandwich and core-shell ball. Their electronic and magnetic properties were quantitatively evaluated by photoionization /photoelectron spectroscopy or by Stern-Gerlach experiments, showing that the organometallic clusters are promising function units of optoelectronic /magnetic properties. We have successfully established the patented soft-landing technique of size-selective deposition upon a substrate covered with low-temperature argon matrix or with self-assembled monolayer of alkylthiol.
(3) networked nano-cluster formed through hydrogen bondings    We have developed a new production method to generate networked molecular clusters through hydrogen bondings up to 500 molecules, and electronic properties and hydrogen transfer dynamics in the electronic excited states were revealed spectroscopically. Bridging between an isolated molecule and bulk liquid/solid was successfully built for fundamental concepts and applications based on molecular nano-clusters.

10.Key Words
(1)Nano-cluster   (2)Nano-crystal   (3)Optical properties
(4)Luminescent Semiconductor   (5)Organometallic Cluster   (6)Hydrogen Bonded Network
(7)Electronic Structure   (8)Magnetic Properties   (9)Soft-landing Technique