Seminar của các Giáo sư trường Tokyo Institute of Technology

Trân trọng kính mời các đồng nghiệp và sinh viên tới tham dự buổi seminar đặc biệt của Viện PRATI và PIAS.

Thời gian: 14h00, ngày 12/03/2019

Địa điểm: Phòng họp chính, nhà B1, Đại học Phenikaa, Yên Nghĩa, Hà Đông, Hà Nội

Nội dung seminar gồm 2 phần:

  1. Giới thiệu về nghiên cứu và các hướng nghiên cứu gần đây của 2 Giáo sư Toshiyuki Ikoma và Nobuhiro Matsushita.

  2. Giới thiệu về các chương trình sau đại học tại Viện Công nghệ Tokyo (Tokyo Institute of Technology).

I. GS. Toshiyuki Ikoma – Dept. of Materials Science and Engineering, Tokyo Institute of Technology

Hướng nghiên cứu chính: Biomaterials, Artificial bones, Catalysis for Air Purification.

Tiêu đề: Hydroxyapatite Nanocrystals for Medical Applications

Tóm tắt:

In increasing deaths from cancer, early detection of tumors has been demanded for early therapy. Fluorescent bioimaging technology for cancer diagnoses has been investigated; this technology is based on nanoparticles which can emit light by irradiation of an exciting light. The nanoparticles should be specifically incorporated into tumor cells via endocytosis. This technology will realize the early detection of tumor tissues before hypertrophy. There are still issues about nano-toxicology and phototoxicity. Hydroxyapatite (Ca10(PO4)6(OH)2; HAp) is one of important bio-minerals and composed of hard tissues. HAp with plate-like morphology has approximately 40 nm in length and 5nm in width in which phosphate groups in the lattice is substituted by carbonate ions. Thus, the sintered porous body has been applied as artificial bone materials for the last several decades. These facts strongly indicate that the HAp nanoparticles show excellent biocompatibility and low cytotoxicity. Luminescent HAp nanocrystals have been prepared by different methods; for example, lanthanide-doped HAp nanorods have been focused in cell imaging by precipitation, hydrothermal, or microemulsion method. The europium(III)-doped HAp (Eu:HAp) nanorods show lower phototoxicity since the wavelength of exciting light could be higher than 400 nm. To improve the incorporation of nanorods into cells, surface functionalization should be desired. In this study, Eu:HAp nanorods were synthesized by a hydrothermal method to decrease the carbonate contents in the HAp lattice, and the surface of nanorods were functionalized with silane coupling agents and folic acid (FA) to enhance endocytosis of cancer cells. The Eu:HAp nanorods were synthesized by the hydrothermal method; the hydrothermal treatment was at 150C for 24 hours in which the molar ratio of Ca and Eu(III) was fixed at 9 to 1. The surface of nanorods was initially covered with 3-aminopropultriethoxysilane (APTES) to cover whole surface area of the nanorods. Then, FA was covalently crosslinked at amino groups of APTES; the molar contents of FA against that of APTES covered on the nanorods were controlled at 1.0 (FA1), 0.5 (FA0.5), 0.3 (FA0.3), and (FA0.1). The photoluminescent properties of FA-functionalized nanorods were measured at 397nm of the exciting light, and the incorporation of the nanorods into cancerous cells (HeLA and A549) were conducted at 1 day incubation. The Eu:HAp nanorods showed a single phase of HAp from the X-ray diffraction pattern, and had a low carbonate content from the Infrared spectrum. Fluorescence spectra of the FA-functionalized Eu:HAp nanorods were measured; although the intensity of the nanorods with ATEPS were not changed, those of the FA-functionalized Eu:HAp nanorods were apparently decreased with the increase of FA. This was caused by the absorption of exciting light at 397nm for FA. Functionalization of FA on Eu:HAp nanorods apparently exhibited larger incorporation number at 4.7 than the Eu:HAp nanorods; however, less FA amount caused larger incorporation number of the nanorods. These results suggested that the optimum amount of FA was of great important for photoluminescent property and caused specific incorporation of Eu:HAp nanorods into cells.

II. GS. Nobuhiro MatsushitaDept. of Materials Science and Engineering, Tokyo Institute of Technology

Hướng nghiên cứu chính: Solution-based processes for functional ceramic materials for Environmental/Energy, Bio-medical and Electronics applications

Tiêu đề: Solution-processed Ferrite Films and ZnO Films – High Frequency Applications and Transparent Conductive Oxides

Tóm tắt:

Spin-spray process enables to deposit the crystallized ferrite films and ZnO films on glass and polyimide substrate by only spraying source solutions including source metal ions and reaction solutions including pH adjuster at temperature below 100˚C without post-deposition heat treatments.

The fabricated ferrite films exhibited both of a high real part of magnetic permeability μ up to hundreds MHz and a strong magnetic loss μ (imaginary part of magnetic permeability) in GHz ranges. The Zn composition x = 0 – 0.56 of ZnxFe3-xO4 film was controlled by Zn ion concentrations in reaction solution. Although the film without Zn substitution had low resistivity in 10-1 Ωcm order, Zn0.36Fe2.64O4 film had the resistivity in 102 Ωcm order enough high for the application in MHz range. The films had large saturation magnetization of 570-600 emu/cm3. They exhibited relatively high μ of 80 and high resonance frequency of 500 MHz. The planar power inductor, 850 x 850 μm in area and 49 μm in height, was fabricated by sandwiching two-turn cupper coil using Zn-substituted ferrite layerrs. This planar inductor exhibited high L of 10 nH and Q of 20 at 100 MHz which is enough for the practical application as planar inductor. Ni0.2Zn0.3Fe2.5O4 films deposited on polyimide sheets (25 μm thick) and their transmission loss ΔPloss and the reflection coefficient S11 in GHz range were evaluated by pressing the ferrite films onto 50 ohm microstrip line. The film 5 μm in thickness exhibited transmission loss ΔPloss of 40 %, which was superior to 20 % of commercialized noise suppression sheet 25 μm in thickness. The reflections coefficient S11 < -10 dB in GHz range was enough small to be used as the conducted noise suppressors.

Functional transparent conductive oxide (TCO) films have been used for various applications. Among the TCO materials, zinc oxide (ZnO) is one of superior candidates as alternative materials for ITO due to their several merits such as low cost of raw material and wide band gap energy (~ 3.7 eV). We succeed in fabricating transparent zinc oxide (ZnO) film by spin-spray method, a kind of solution process, at low temperature below 100ºC adding tri-sodium citrate in the solutions. The films irradiated by UV black light exhibited the low resistivity below -10-2 Ωcm due to hydrogen doping.

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