Research Themes:
Nanoparticle Technology: From synthesis to practical applications

Green chemistry methodology is used to reduce raw material consumption, waste, and hazardous substances through designing environmentally-friendly chemical reactions, and/or by controlling the higher-order structures of nanomaterials.

Our group fabricates new functional materials based on this perspective, with a focus on nanoparticles. Our three main research projects are as follows.

1) Development of functional properties of colloidal semiconductor nanoparticles via higher-order structuring

Colloidal semiconductor nanoparticles (quantum dots: QDs) exhibit a strong quantum confinement effect and, thus, can be considered as “artificial atoms”. Therefore, the function of a QD ensemble is determined not only by the physicochemical properties of a single QD, but also by the inter-dot interactions that vary with their higher-order structure.

We synthesize QDs and their higher-order structures via a colloid chemical route, and investigate structure-property relations. Specifically, we aim to clarify inter-dot interactions in the higher-order structures of II-VI, III-V, IV-VI and thermoelectric semiconductor QDs.

In addition, we hope to create QD solids capable of new functions based on inter-dot interactions, which are not observed in a single QD. At the same time, we aspire to develop the practical applications of QDs, such as LED, solar cell, photodetector, and thermoelectric devices.

 

2) Application of magnetic nanoparticles to biotechnology and environmental technology

In general, ferromagnetic materials only have ferromagnetic properties over a certain critical size. This is due to the disordering of magnetic moments becoming prominent, which is caused by thermal disturbance (superparamagnetism).

The area density of magnetic storage media increases with each passing year, and researchers have aimed at the realization of the density of Tbit/in2. Magnetic nanoparticles (MNPs) have attracted attention and have been intensively investigated for this purpose. In magnetic storage media, one of the most important challenges is the fight against superparamagnetism.

However, the superparamagnetic nanoparticles are very important for medical applications, such as MRI contrast agents, magnetic immunodiagnostics, magnetic separation, and magnetic hyperthermia. Our research group concentrates on these applications of superparamagnetic nanoparticles.

We synthesize MNPs, functionalize their surfaces, and develop basic techniques for medical and environmental applications.

TEM images and photographs of (a) oleic acid-capped and (b) 2-aminoethanethiol-capped FePt NPs.

 

3) Development of biosensing technologies utilizing metalic nanoparticles

Current genetic diagnostics suffer from high-cost and time-consuming operations, because they usually need precise temperature control and/or expensive reagents.

Recently, various biosensors using metalic, such as gold and silver, NPs have been proposed, e.g. LSPR sensors. Thus, easy-to-use and rapid analyses of DNA or protein become to be realized.

We are currently developing novel biosensors based on original ideas and techniques, and apply them to ultra-sensitive biodetection systems in the near future.

 

Others

We are also studying on the formation mechanism of nanoparticles in wet chemical synthesis and the intriguing phenomena related to the quantum confinement effect.

We propose a new microscopic quantum mechanical model for describing the nonstochastic dynamics of the nanoscopic light-emissive quantum dot. The model is extended beyond a single quantum dot to consider the Coulomb repulsion between neighboring quantum dots in the ionic states caused by the random fluctuations of charge carriers.