Materials Research and Technology

Biography

Biography: Haruhisa Kato

Abstract

There have been numerous reports on nano sized materials and investigations of the relationship between their size and physical properties. In general, commercial nanomaterials are provided as dry powder. The sizes of the primary nanoparticles are determined using the Brunauer, Emmett and Teller method or a microscopic technique. However, nanomaterials are easily aggregated in liquid phase when one want to disperse them to make novel functional application, since the high ionic nature of the solution and the electrostatic/Van der Waals interaction between nanomaterials result in secondary particles. In such a sense, the accurate characterization of the nano suspension is necessary to understand the real properties of nanomaterials in liquid phase, not only characterization of primary particles by gas-phase characterization method such as electron microscope. This study therefore concerns with characterization of the nano suspension using Pulsed Field Gradient Nuclear Magnetic Resonance (PFG-NMR) techniques. PFG-NMR spectroscopy has not been commonly employed to determine the size of nanomaterials because of the very low local reorientation mobility of hard sphere type molecules such as gold sphere. The short T2 relaxation time also makes it difficult to determine the size of hard-core materials and large molecules. However, the PFG-NMR requires no special handling or preparation of the sample. In addition, the individual self-diffusion coefficients in a multi-component system can be obtained by simultaneously monitoring NMR signals at different chemical shifts. In this study, we therefore used this PFG-NMR technique and developed the quantitative evaluation of the size of materials in nano suspension and also determine the number of bound dispersant on nanomaterials to recognize the real structure of nanomaterials in liquid phase. Since the dispersant is one of the key to disperse nanomaterials stably in liquid phase our characterization on both nanomaterials and dispersant in nano suspension by PFG-NMR should be significant in nano technological field.

Recent Related Publications

1. Kato H, Nakamura A, Ouchi N, Kinugasa S. (2016) Determination of bimodal size distribution using dynamic light scattering methods in the submicrometer size range, Mat. Express, 6: 175-185.
2. Kato H, Nakamura A, Horie M (2015) Acceleration of suspending single-walled carbon nanotubes in BSA aqueous solution induced by amino acid molecules. J. Colloid Int. Sci, 437: 156-162.
3. Kato H, Nakamura A,  Horie M (2014) Behavior of Surfactants in Aqueous Dispersions of Single-Walled Carbon Nanotubes. RSC Adv. 4: 2129-2136.
4. Kato H, Nakamura A, Noda N, (2014) Determination of Size Distribution of Silica Nanoparticles: A Comparison of Scanning Electron Microscopy, Dynamic Light Scattering, and Flow Field-Flow Fractionation with Multiangle Light Scattering Methods. Mat. Express, 4: 144-152.
5. Kato H, Nakamura A, Mastubara K (2012) Dynamics and Role of Rosin Acid Molecules for Preparation of Well-Dispersed CaCO3 Colloidal Suspensions J. Nanopart. Res. 14: 950-1.
6. Kato H, Shinohara N, Nakamura A, Horie M, Fujita K, Takahashi K, Iwahashi H, Endoh S, Kinugasa S (2011) Characterization of Fullerene Colloidal Suspension in a Cell Culture Medium for in vitro Toxicity Assessment. Mol. Biosys. 6: 1239-1246.
7. Kato H, (2011) Tracking Nanoparticles inside Cells. Nature Nanotech 6: 139-140.