【公開日：2024.07.25】【最終更新日：2024.06.29】

課題データ / Project Data

課題番号 / Project Issue Number

23UT0319

利用課題名 / Title

金属酸化物ナノ粒子の合成と物性に関する研究

利用した実施機関 / Support Institute

東京大学 / Tokyo Univ.

機関外・機関内の利用 / External or Internal Use

内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)

技術領域 / Technology Area

【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-

【重要技術領域 / Important Technology Area】（主 / Main）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials

キーワード / Keywords

電子顕微鏡/ Electronic microscope,エネルギー貯蔵/ Energy storage,光学顕微鏡/ Optical microscope,X線回折/ X-ray diffraction,ナノ粒子/ Nanoparticles

利用者と利用形態 / User and Support Type

利用者名（課題申請者）/ User Name (Project Applicant)

吉清 まりえ

所属名 / Affiliation

東京大学 大学院理学系研究科

共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes

生井 飛鳥,MacDougall Jessica,賈 方達

ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes

押川 浩之,福川 昌宏,寺西 亮佑,森田 真理

利用形態 / Support Type

（主 / Main）機器利用/Equipment Utilization（副 / Sub）-

利用した主な設備 / Equipment Used in This Project

UT-008：高分解能トップエントリー型透過電子顕微鏡
UT-005：原子分解能元素マッピング構造解析装置
UT-102：高分解能走査型分析電子顕微鏡
UT-103：高分解能走査型電子顕微鏡
UT-007：高分解能分析電子顕微鏡

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

In this study, a composite material of core epsilon iron oxide (ε-Fe₂O₃) nanoparticles within a shell matrix of Prussian blue (PB) nanocrystals was synthesized by a co-precipitation method. Annealing of the composite sample at 300 °C and 500 °C in air showed the PB phase was converted into ε-Fe₂O₃ due to a seed-mediated effect from the pre-existing core ε-Fe₂O₃ in the composite.

実験 / Experimental

An aqueous dispersion of core ε-Fe₂O₃ nanoparticles was prepared by an established method and coated in PB by the addition of HCl and K₄[Fe(CN)₆]. The resulting precipitate was neutralised with NaHCO₃, washed in water and ethanol and dried to give the composite sample. The composite sample was then annealed at 300 °C and 500 °C for 2 hours in air. A further sample of only PB was prepared in the same manner by the substitution of core ε-Fe₂O₃ nanoparticles with FeCl₃ and was annealed under the same conditions.The particle morphology was observed by transmission electron microscopy (TEM), and the phase compositions were determined by Rietveld analysis of the powder X-ray diffraction (PXRD) patterns. The thermal decomposition of the PB phase was investigated by thermogravimetric analysis (TGA). Magnetic measurements were taken using a super-conducting quantum interference device (SQUID).

結果と考察 / Results and Discussion

The initial composite sample was shown by TEM to consist of spherical epsilon iron oxide nanoparticles (d_TEM = 21±6 nm, corresponding to the initial size of the core ε-Fe₂O₃) embedded in spherical or cubic PB nanocrystals. PXRD analysis showed the composite contained 27% ε-Fe₂O₃ and 73% PB. TGA showed there was a reduction in mass around 250 °C as the PB phase of the composite thermally decomposed into iron oxides. TEM images showed the PB was decomposed into very small nanoparticles at 300 °C, which then formed into larger particles at 500 °C with a wide particle size range. After annealing, the PXRD patterns showed that the 300 °C annealed sample contained 30% γ-Fe₂O₃ and 70% ε-Fe₂O₃ and the 500 °C annealed sample contains 86% ε-Fe₂O₃ and 14% α-Fe₂O₃. This shows that the PB phase of the composite has converted to ε-Fe₂O₃ with relatively high purity at low temperatures. TEM images of the 500 °C annealed sample show that some large angular particles which have morphology akin to the PB nanocrystals in the composite, have lattice spacing belonging to ε-Fe₂O₃. The magnetic hysteresis loops of the samples showed the relatively large coercive field expected from ε-Fe₂O₃ samples with a wide particle size range.The annealing products of the sample containing only PB was shown to contain γ-Fe₂O₃ and β-Fe₂O₃ at 300 °C and α-Fe₂O₃ at 500 °C. The inclusion of ε-Fe₂O₃ nanoparticles within the PB phase is thought to act as seeds, enabling the formation of ε-Fe₂O₃ from PB, which is otherwise unfavorable.

図・表・数式 / Figures, Tables and Equations

TEM images of core nanoparticles (left), composite (middle), and annealed sample (right).

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

参考文献
J. MacDougall, A. Namai, M. Yoshikiyo, S. Ohkoshi, Seed-mediated Generation of Epsilon Iron Oxide Nanocrystals at 300 °C, Chemistry Letters, 52, 2023, 229–232, https://doi.org/10.1246/cl.220545

謝辞本研究では、特にTEM観察において総合研究機構ナノ工学研究センターの押川様、福川様にご協力を頂きました。厚く御礼を申し上げます。

成果発表・成果利用 / Publication and Patents

論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

1. A. Namai, S. Ohkoshi "Study of metal-substituted ε-iron oxide ferrite nanomagnets exhibiting large magnetic anisotropy" ナノ学会合同部会シンポジウム, 2023/11/22
2. M. Yoshikiyo, A. Namai, S. Ohkoshi "Theoretical study of the optical properties of epsilon iron oxide" International Symposium on Ancient Chinese Black Glazed Iron Oxide Crystals, 2023/11/6
3. J. MacDougall, A. Namai, M. Yoshikiyo, S. Ohkoshi "Synthesis, properties and annealing products of ε-Fe2O3@Prussian blue composite nanoparticles" PDSTM 2023, 2023/11/30
4. J. MacDougall, A. Namai, M. Yoshikiyo, S. Ohkoshi "Synthesis and Characterisation of ε-Fe2O3@Prussian Blue Composite Nanoparticles and their Annealing Products" The 15th Research Forum Cryogenic Research Center, 2024/2/16

特許 / Patents

特許出願件数 / Number of Patent Applications：2件
特許登録件数 / Number of Registered Patents：3件