Dr. Hiroharu Yui, Professor

Dr. Hiroharu Yui

Development of Novel Measurement Methods for Aqueous Solutions utilizing Electrons and Their Applications

Department of Chemistry, Faculty of Science Division I, Tokyo University of Science

*The organization and the title are those when awarded

Abstract

  • 日本語
  • English

水溶液中で作動する電極・触媒表面や細胞内小器官の間隙,酵素の反応ポケットといった界面・ナノ空間に存在する水の微視的構造環境を計測できる技術への要望が高まりつつある。そのような局所空間の水は絶対量が少ないだけでなく,埋もれた環境に存在するため,その計測技術には高感度性だけでなく測定空間選択性も要求される。本研究はラマン散乱分光法をベースとし,電子を信号増強プローブとした新しい水の局所構造分析法を提案するものである。ラマン散乱スペクトルは水の微視的構造環境変化を鋭敏に反映するため,電子を目的計測部位に選択的に生成する技術と組み合わせることができれば,新しい水計測法の開発につながると期待できる。

New analytical tools that enable the measurements on water in nanometer-sized interfacial and confined nanospaces have been required. Water in such restricted nanospaces plays important roles for chemical processes at the surfaces of electrodes and catalysts, in nanospaces between intracellular organelles, and in reaction pockets of enzymes. However, such analytical tools have to meet the requirements both high-sensitivity and site-specificity, because the total amount of water in such nanospaces is extremely small and it is generally buried in surrounding aqueous solutions. Here we developed a new Raman spectroscopic technique based on a signal enhancement utilizing transiently generated electrons. Since Raman spectra sensitively reflect local water structures, it can be expected that the electron-enhanced Raman technique will provide a new tool to measure water in restricted environments when it is combined with site-selective electron-injecting methods.

Research summary

Raman spectroscopy, which is a kind of laser spectroscopy, is a useful analytical tool to identify molecular structures.

But with liquid samples, it is difficult to develop industrial applications because the signal is very weak.

Prof. Yui discovered a new Raman enhancement phenomenon, named electron-enhanced Raman scattering, which enhances the Raman scattering intensity by up to 100,000 times, utilizing electron effect generated by irradiating strong laser pulse into an aqueous sample.

The discovery led him to the development of a new analytical technique that can measure Raman spectra by only one shot of irradiation, even under a strong background.

This new method analyzes microscopic structures and properties of such samples as surface of aqueous solutions and “super-critical water”.

It is expected to be applied to the continuous online measurements of various aqueous samples, such as rinse water at the semiconductor production site, cooling water of power plants and running water in the environment.

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