Tokyo Institute of Technology · Engineering
Professor Yasuhiko Orita's research lab specializes in the development of sustainable and green synthesis methods for advanced nanomaterials, with a strong focus on supercritical fluids—particularly supercritical CO₂ and water—as reaction media and solvents. The lab pioneers solventless and low-waste processes for the controlled synthesis of metal oxide and metal nanoparticles, emphasizing size control, dispersibility, and eco-friendly processing. A key innovation lies in integrating machine learning for rapid screening of surface modifiers and solvents, while also advancing efficient, continuous, and scalable washing techniques using cosolvent-enhanced supercritical CO₂ to improve nanoparticle purification. The lab's work bridges fundamental materials chemistry with practical industrial applications in energy, catalysis, and biomedicine.
Figures are computed from collected data and may differ slightly.
In the synthesis of surface-modified nanocrystals (NCs), a simple and green chemistry approach to reduce liquid waste, particularly a solventless process, has been desired. In this study, we applied the supercritical CO<sub>2</sub> technology, which is an excellent solventless process, to the synthesis of surface-modified iron oxide NCs. The synthesis was performed at 30.0 ± 0.8 MPa of CO<sub>2</sub>, 18 h and 100 °C, where iron(iii) acetylacetonate, pure water and decanoic acid were used as sta
In the synthesis of metal oxide nanoparticles (NPs), methods to control their size and distribution have been desired. Precise and rapid control without the use of organic surfactants is a serious challenge. In this study, we report a strategy, dual-stage method using supercritical and subcritical water, for precise and rapid control of the size and distribution of NPs and applied it to the synthesis of CeO2 NPs. The synthesis was performed using three types of flow reactors, and the effects of
Rapid and continuous synthesis of metal nanoparticles using green solvent system is still a serious challenge for both fundamental and practical research. In this work, we report a new flow process using water in supercritical CO2 (w/scCO2) emulsion and applied it to the synthesis of silver nanoparticles (AgNPs). To investigate the performance of our system, AgNPs were synthesized by batch, flow and w/scCO2 emulsion flow system at 40 ºC while using AgNO3, NaBH(OAc)3, trisodium citrate and Aeroso
Low temperature synthesis of ZnO particles without using reactive materials, solvents and post-treatments is still a serious challenge for both fundamental research and industrial applications. In this research, we report the dry synthesis of ZnO particles only by using Zn(acac)<sub>2</sub> and supercritical CO<sub>2</sub> (scCO<sub>2</sub>) at the low temperature of 60 °C. The synthesis was performed using CO<sub>2</sub> and N<sub>2</sub> from 0.1 to 30.0 MPa for 18 h. As a result, ZnO yields i
Surface-modified nanoparticles (NPs) have attracted major interest in widespread applications due to their good dispersibility in solvents. Although the selection of modifiers and solvents is also crucial to achieving good dispersibility, experimental screening consumes a significant amount of financial, material, and time resources due to the many candidates of modifiers and solvents. In this work, supervised machine-learning models were established to screen modifiers and solvents while using
In practical applications of surface-modified nanoparticles (NPs), the washing stage has a number of challenges, such as insufficient washing, long treatment time, and various waste liquors. Cosolvent-enhanced supercritical CO2 (scCO2) is an appealing solvent system for complete, rapid, and eco-friendly washing owing to its high diffusivity and recyclability. In this paper, we report a rapid washing guideline for surface-modified NPs using ethanol-enhanced scCO2. Kinetic analysis was performed o
Methanol is an important industrial material for the production of medicines, fuels, and resins. Methanol is generally synthesized under catalyst by reacting CO and H2 through steam reforming of methane. This process is, however, energy consuming. Hence, a direct methanol synthesis method, which is less energy consuming, should be developed. The authors conducted flow-type partial oxidation of methane using the Fenton reaction under hydrothermal conditions for the direct synthesis of methanol fr
メタノールは薬品，燃料，樹脂などを生産するうえでの重要な工業基礎原料であり，一般にメタンの水蒸気改質で得られるCOとH2を触媒下で反応させることで合成する．しかし，このプロセスはエネルギー消費量が多く，直接合成法などの開発が望まれている．そこで，本研究ではメタンからのメタノール直接合成を目的として，H2O2を用いたメタンの流通式水熱部分酸化試験を行い，H2O2の予熱を予熱無，予熱有（120°C, 270°C以上）と，反応温度100–350°Cをパラメーターとして試験を実施した．その結果，反応温度350°C, 滞留時間31 s, H2O2予熱無では予熱270°C以上に比べメタン転化率が大幅に増大し，その結果メタノール収率も増加し類似研究より高い値を示した．H2O2の予熱無では，予熱段階でのH2O2の熱分解がなく，急速昇温によって強力な酸化剤である·OHの発生が反応場で起こり，メタン転化率が増大したと推察される．一方，H2O2の予熱270°C以上では反応管へ達する前にH2O2がすべてO2に分解したと推察された．
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