第145回目のスポットライトリサーチは、京都大学大学院理学研究科北川研究室の博士学生・張権さんにお願いしました。
北川研究室では、様々な機能性ナノ合金材料の設計・合成が行われています。特に、「元素間融合」と呼ばれる技術はその中でも特筆すべきものです。例えば、ロジウム（原子番号45）と銀（原子番号47）からなる合金がパラジウム（原子番号46）のような水素吸蔵性を持つことを報告しています。
今回の研究はナノ合金の精密設計に関するもので、以下のとおりNature Communication誌に掲載されました（オープンアクセスなので、どなたでも読めます）。また、プレスリリースで注目されています。
Selective control of fcc and hcp crystal structures in Au–Ru solid-solution alloy nanoparticles
Q. Zhang, K. Kusada, D. Wu, T. Yamamoto, T. Toriyama, S. Matsumura, S. Kawaguchi, Y. Kubota, H. Kitagawa
Nature Communications 2018, 9, 510. DOI: 10.1038/s41467-018-02933-6
今回インタビュー内容は英語ですが、分かりやすく書いていただきました。それでは、研究の詳細をご覧ください！
Q1. 今回のプレス対象となったのはどんな研究ですか？
The crystal structure is one of the most dominant factors that strongly affect the properties of an alloy because the electronic and surface structures change drastically with the crystal structure. However, to date, the influence of the crystal structure has rarely been studied because control of the crystal structure of alloy NPs is still a great challenge. In this work, we propose a new approach for selective control of the crystal structure in solid-solution alloys by using a chemical reduction method. By precisely tuning the reduction speed of the metal precursors, we demonstrated the first example of selective control by synthesizing fcc- and hcp-AuRu3 alloy nanoparticles. The alloy adopts a fcc structure when the Au precursor starts to be reduced slightly earlier, while it adopts an hcp structure when the reduction of Ru precursor begins slightly earlier.
金属組成を変えずに固溶体合金の構造を合成条件（構成元素のどちらの金属塩をわずかに先に還元させるか）によって選択的に作り分けることができたという点が最も大きな成果です。
Q2. 本研究テーマについて、自分なりに工夫したところ、思い入れがあるところを教えてください。
In general, the properties of alloy NPs have been controlled by the size, morphology, constituent elements and compositional ratio. The influence of the crystal structure on the properties of alloy NPs has rarely been studied. In this work, by proposing a new approach for selective control of the crystal structure, we introduced a new material design degree of freedom, “crystal structure”, to create novel chemical and physical properties for alloy NPs. In addition, our concept can provide a new method for controlling the crystal structure of not only Au–Ru system but also other alloy systems consisting of several elements that adopt different structures.
Q3. 研究テーマの難しかったところはどこですか？またそれをどのように乗り越えましたか？
The key step for this research is the reduction speeds control of the metal ions. We believe the reduction speed can be adjusted through choosing suitable metal precursors. Therefore, the reduction speeds of precursors with different ligand were first tested. Then, the precursors were combined to form the alloy NPs. This part of work takes around one year. I remember every day four or five syntheses were conducted but most of them were failed results. After carefully analyzing these experimental results, we gradually approach the final achievement. So, I think most of the good results cannot be achieved for few experiments. In addition, please carefully analyze your experimental results including the failed one, because even the fail experimental results may provide you some useful information.
Q4. 将来は化学とどう関わっていきたいですか？
Nowadays, with the increasing environmental concerns and accelerated consuming of fossil fuels, search for the alternative energy is becoming a significant issue for worldwide researchers. Chemistry plays an important role in developing the new clean energy. For metal and alloy NPs, one of the most important applications is catalysis on reactions for clean energy conversion for example, fuel cells, water electrolysis, metal–air batteries, and CO2 to fuel conversion. At present, we are focused on the developing of new solid solution alloy NPs and the basic property control of these alloy NPs. We will further explore their applications on catalysis clean energy conversion reactions and hope we can make a contribution to the development of the clean energy.
Q5. 最後に、読者の皆さんにメッセージをお願いします。
As a researcher in chemistry, we always meet some challenges and difficulties during the research. The process for solve these problems may take us a large amount of time. It is easy to make us feel disappointed. When you are in these situations, please keep optimistic and believe that there are no obstacles that cannot be overcome. Discussion is a very useful way to help you extricate yourself from a difficult situation and save your time on solving the problems. Please enjoy the fun of research and hope every young researcher can harvest plentiful result.
関連リンク
研究者の略歴
名前:張 権 (チョウ ケン, ZHANG QUAN)
所属: 京都大学 大学院理学研究科 化学専攻 固体物性化学研究室
略歴:１９８８年９月、中国河南生まれ。２０１０年６月、中国河南大学卒業。２０１３年３月、中国東華大学卒業。２０１４年１０月、京都大学大学院理学研究科研究生（北川 宏 教授）。２０１５年４月、京都大学大学院理学研究科化学専攻博士後期課程編入学（北川 宏 教授）。
研究テーマ:固溶体ナノ粒子の合成及び電極触媒特性の研究
