Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Sun, Jingyi

そん せいい
氏 名  SUN JINGYI 
授 与 学 位         博士（学術）
学 位 記 番 号 
学 位 授 与 年 月 日         2025 年 3 月 25 日
学位授与の根拠法規 学位規則第 4 条第 1 項 
研究科，専攻の名称 東北大学大学院環境科学研究科（博士課程）先進社会環境学専攻
学 位 論 文 題 目         Development of Comprehensive 3D Polarization Analysis Techniques in 
the Time-Frequency Domain and its Application (時間-周波数領域におけ
る包括的な 3 次元偏波解析法の開発と応用) 
指 導 教 員 東北大学教授　伊藤　高敏
論 文 審 査 委 員         主査　東北大学教授　伊藤　高敏　東北大学教授　森谷　祐一
研究員　Nori Nakata 　　　東北大学助教　椋平　祐輔
（ローレンス・バークレー国立研究所)
論 文 内 容 要 旨         
Abstract 
Seismic wave detection plays a key role in earthquake monitoring, hypocenter location, and 
geological structure studies. By accurately identifying different seismic phases and their arrival 
times, it provides critical data to determine hypocenter locations and understand focal 
mechanisms. Seismic wave detection also supports early warning systems and helps investigate 
fault dynamics, internal stratigraphy, and subsurface resource exploration. However, 
conventional detection methods face serious challenges in low signal-to-noise ratio (SNR) 
conditions and when only sparse seismic data is available. In low-SNR environments, weak 
seismic phases are often buried in background noise. In sparse station networks, reliable phase 
association and event location become highly uncertain. These challenges make seismic phase 
detection and hypocenter inversion under difficult conditions an urgent research focus. 
Polarization analysis is a key signal processing technique based on seismic wave 
propagation principles. As seismic waves propagate, their particle motion carries unique 
directional characteristics. These motion features can be used to distinguish different wave 
学術（環）博第376号
types and estimate incidence angles. Our previous study applied spectral matrix (SPM) analysis 
to characterize the 3D particle motion of P waves. However, SPM analysis struggles to capture 
planar motion characteristics typical of S-waves and later phases. To address these issues, this 
paper proposes a novel complex spectral matrix (cSPM) method for 3D particle motion analysis 
in the time-frequency domain. This method enhances the traditional SPM by introducing two 
time-delayed components, expanding the matrix rank to 3. This rank expansion breaks the 
mathematical limitation of conventional SPM. It allows cSPM to describe not only the linear 
motion of P-waves, but also the planar motion associated with S-waves and other later arrivals. 
Using eigen decomposition of the cSPM, we define polarization-based characteristic functions 
for both P- and S-waves. These functions enable accurate phase detection by tracking changes 
in 3D particle motion in the complex domain.  
We applied the proposed method to field data recorded at the Groningen gas field in the 
Netherlands. The dataset includes 4-hour continuous recordings and 2 months of long-term data. 
They contain cataloged seismic events. Our method effectively identifies not only the P-waves 
and S-waves associated with cataloged events in the dataset but also the P-waves and S-waves 
of previously unidentified low-SNR events. Using the detected P- and S-wave arrivals, we 
estimate P-S travel times and locate event hypocenters. All detected events are successfully 
located, demonstrating the reliability of the proposed method. 
To further enhance practical application, we propose a complete multi-phase detection 
and hypocenter inversion workflow based on cSPM at a single station. By using both particle 
motion characteristics and arrival times, we establish reliable links between seismic phases and 
detected events. Hypocenter locations are further refined using these phase associations. This 
cooperative analysis of phase detection and hypocenter inversion significantly improves the 
stability of event location. 
In summary, this study comprehensively develops the cSPM method, an advanced 
approach to 3D particle motion analysis for waveform phase detection in the time-frequency 
domain. The cSPM method accurately identifies wave phases and their arrival times, 
significantly advancing seismic monitoring and geological research. The robustness of the cSPM 
framework in identifying seismic phases is demonstrated even in challenging low SNR 
conditions and with single-station data. Future research directions could involve developing 
customized indicators of cSPM to meet more requirements. 
 
 
（別紙） 
 
論文審査結果の要旨及びその担当者 
 
論文提出者氏名  孫 静怡 (ソン セイイ) 
論 文 題 目        
Development of Comprehensive 3D Polarization Analysis Techniques in the Time-Frequency Domain and its 
Application (時間-周波数領域における包括的な3次元偏波解析法 の開発と応用)  
 
論文審査担当者 
 主査  教 授    伊藤 高敏  
     教 授    森谷 祐一  
     研究員    Nori Nakata (ローレンス・バークレー国立研究所) 
     助 教    椋平 祐輔  
 
論文審査結果の要旨 
 
地震波は、自然現象（地震・火山活動）や人工的な要因（爆発・流体注入・採掘作業など）によって発生し、地下
構造の理解や資源探査、地震リスク評価において重要な情報を提供する。地震波にはP波（縦波）、S波（横波）、表
面波があり、それぞれ異なる偏波特性を持つ。 
従来の地震波検出手法には、短時間平均／長時間平均（STA/LTA）、テンプレートマッチング、機械学習ベースの手
法があるが、これらには課題が存在する。特に、微小地震のような低信号対雑音比（SNR）のデータでは、従来の方
法では検出が困難であり、新しい解析手法の開発が求められている。本研究では、3次元偏波解析（3D Polarization 
Analysis）を活用し、地震波の偏波特性を解析することで、低SNRの地震波を効果的に検出する手法を提案する。 
 第１章は緒論である。 
 第２章では、3次元偏波解析の基礎的な理論、既存の時間領域、時間―周波数領域における解析手法・問題点に関
して述べている。 
 第３章では、本研究で新たに適用する信号処理について述べている。複素スペクトル行列解析 complex Spectral 
Matrix Analysis (cSPM)は、時間遅延成分を加えた複素行列であり、3つの固有ベクトルを取得できるため、より包
括的な偏波解析が可能である。従来のSPM解析法では、P波に代表される直線偏波のみが評価可能であったが、本
研究で開発した cSPMを用いることで、S波等の平面偏波を評価することも可能となった。 
 第４章では、cSPM の実データ解析へ応用の一例として、ノイズに埋もれがちな微小地震の S 波の検出を試みた
例について述べている。そこで、オランダ・グローニンゲンガス田で記録された地震データを用いて、P波S波の走
時差を検出し、それを直接震源決定にも応用した。震源の空間分布を明らかにした。cSPM解析により、従来手法で
は検出困難だった微小地震の識別が可能になり、提案手法の有用性が確認された。 
 第５章では、 cSPMの他の応用例について述べている。そこで、単一の観測点のみの情報を用いて、cSPMによ
り多様な実体波（P波、S波、変換波など）を検出し、震源決定に利用できることを明らかにした。 
 第６章は結論である。 
 以上より、本研究では、従来のSPM解析の限界を克服した、複素スペクトル行列（cSPM）解析を、地震学・資
源工学における実体波検出・評価問題に応用し、幾つかのテーマでフィールドデータに応用し、十分な結果を得られ
ることでその有用性を証明した。本手法は、今後も地震学研究や、地下構造の解明、資源探査、災害リスク評価など
の分野において重要な役割を果たすことが期待される。 
 よって、本論文は博士(学術)の学位論文として合格と認める。 
 
    


English

時間-周波数領域における包括的な3次元偏波解析法の開発と応用

松野, 哲士

まつのさとし
氏 名  松野 哲士
授 与 学 位        博士（学術）
学 位 記 番 号 学術（環）博第 378 号 
学 位 授 与 年 月 日         2025 年 3 月 25 日
学位授与の根拠法規 学位規則第 4 条第 1 項 
研究科，専攻の名称 東北大学大学院環境科学研究科（博士課程）先進社会環境学専攻
学 位 論 文 題 目         Data-Driven Analyses of Element Transfer within Oceanic 
Crust During Fluid-Rock Interactions at Seafloor and 
Subduction Plate Interface（海洋底・沈み込みプレート境界にお
ける 岩石-流体相互作用に伴う元素移動のデータ駆動型解析） 
指 導 教 員 東北大学教授 岡本敦
論 文 審 査 委 員          主査 東北大学教授 岡本 敦 東北大学教授 渡邉 則昭
東北大学教授 辻森 樹 
（理学研究科）
東北大学准教授 宇野 正起
教授 Sarah Penniston-Dorland（メリーランド大学） 
論 文 内 容 要 旨         
The methodological limitations on element transfer analysis in altered and metamorphic rocks 
are twofold: 1. quantitative analysis of element transfer is impossible if the protolith for each 
sample cannot be quantitatively determined, and 2. because metamorphic rocks have undergone 
multistage reactions, they record the total element transfer from the starting material, making 
it impossible to determine the extent of individual reaction processes. This lack of numerical 
description is a problem not only at the outcrop scale but especially at the regional scale, which 
has disturbed quantitative analysis of fluid flow associated with the alteration of the oceanic 
crust and metamorphism in subduction zones. In the study of oceanic crust alteration, it has 
been impossible to compare chemical composition data from cores that have experienced 
different alteration condition, making the parameters controlling and influencing element 
transfer during alteration unclear. Regarding metamorphic rocks, element transfer in open 
systems at a regional scale remains unclear, leaving the depth and amount of fluid release and 
element mobile unknown. The released fluids are thought to flow through fluid pathways 
formed by localized, concentrated fluids and along the plate interface. During this process, the 
fluid interacts with the surrounding rocks as it flows through the fluid pathway, but the element 
transfer accompanying this reaction, the changes in mineral assemblage due to the reaction, 
and the volume of fluid flow remain unclear. 
In this thesis, I studied on element transfer during fluid-rock interaction within oceanic 
crust at seafloor and during metamorphism within subduction plate interface. For this purpose, 
I introduced and validated new methodologies on the machine-learning based protolith 
reconstruction and quantitative analyses of mineral modes and elemental transfer.  
In Chapter 2-1, for the purpose of reconstructing the mass transfer history of 
metabasalt, I developed protolith reconstruction models (PRMs) for metabasalt using machine-
learning algorithms. I designed models to estimate trace-element concentrations of basaltic 
rocks from the concentrations of a few (1–9) trace elements, trained with a global dataset for 
the compositions of fresh basalts in various settings, including mid-ocean ridge, ocean-island, 
and volcanic arc basalts. The developed PRMs succeeded in estimating basalt trace-element 
compositions (e.g., Rb, Ba, U, K, Pb, Sr, and rare-earth elements) from only four input elements 
with a reproducibility of ~ 0.1 log10 units (i.e., ± 25%). This method enables us to analyze 
quantitative mass transfer in regional metamorphic rocks or alteration zones where the 
protolith is heterogeneous or unknown. 
In Chapter 2-2, I developed regression-based machine-learning models and examined 
the relationships among elemental contents for basalts. I applied an extended gradient boosting 
algorithm (natural gradient boosting), which allows predictions with associated probability 
distributions, to a training dataset of global basalt compositions, including mid-ocean ridge, 
ocean island, and volcanic arc basalts. From four input elements (Th, Nb, Zr, and Ti), the trained 
models can successfully predict the contents of 12 trace elements (Rb, Ba, U, La, Ce, Pb, Sr, P, 
Nd, Y, Yb, and Lu; R2 > 0.7) and 5 major elements (SiO2, MgO, Na2O, CaO, and K2O; R2 > 0.67). 
The adopted model interpretation techniques quantitatively identified key input features for 
output element estimations, such as similar elemental incompatibility (e.g., Th–Rb contents) 
and elemental ratios/products involving different incompatible elements (e.g., Zr/Th ratios for 
Yb contents). This is consistent with well-established geochemical principles related to 
elemental incompatibility and tectonic setting, and was achieved without prior geochemical 
knowledge of the samples. On a projection of a reduced two-dimensional map constructed from 
the four input elements, numerical variations of the identified key input features were 
correlated with the output contents. Given the successfully constructed regression-based models 
based on only four input elements, basalt geochemical data have a low dimensionality.  
In Chapter 2-3, I applied the powder X-ray diffraction (PXRD) to low-grqade 
metamorphic rocks to quantify bulk mineral modes and compositional zoning ratio of amphibole. 
I compared obtained mineral modes with EPMA-derived mineral mode, and validated in bulk 
chemical compositions. Consequently, I showed that PXRD methods are more suitable for 
quantifying mineral modes compared to EPMA point counting due to the elimination of grain 
size influence. Beyond its suitability for mineral mode quantification, the digital nature of 
PXRD data allows for sample archiving, providing the potential to accumulate not only 
geochemical data but also mineral-related data for a comprehensive understanding of geological 
processes. 
In Chapter 3, I conducted for the first time quantitative analysis of the element mobility 
derived from a regional dataset of the altered basaltic crust from the Pacific ocean (data sourced 
from different drilling sites and alteration systems). Element mobilities changes with geological 
setting of sediment thickness, redox setting, and duration of alteration of the oceanic lithosphere. 
Our analyses show that older altered basalt has higher element mobility. In particular, Rb and 
K are enriched relative to their estimated contents in the protolith by a factor of 100 and 10, 
respectively, due to the formation of secondary minerals under oxidizing conditions. In the 
oxidizing settings of the South Pacific, enrichment in Ba and U was observed in samples with 
intense oxidation. In contrast, under relatively reducing conditions in the Northwest Pacific, 
alteration was associated with the formation of carbonate veins and U enrichment. The 
differences in quantitative element mobility and secondary mineralization demonstrate that 
sediment thickness and seafloor age control redox conditions and the duration of seafloor 
alteration. 
In Chapter 4-1, I investigated the low-grade metamorphic rocks from the Asemigawa-
are region in Sanbagawa metamorphic belt, Japan. I studied element transfer in subduction 
zone associated with fluid flow of dehydration and hydration in perspective of regional and 
outcrop scale. As the study for regional-scale samples from low- to high-grades along 
Asemigawa-river, I showed element transfer differences in response to metamorphic reactions 
during prograde and retrograde stages, respectively. With increasing experienced temperature, 
Rb, Ba, K and Sr was depleted. Until experiencing temperature of 550°C, 90% of element content 
was removed by dehydration. In contrast, hydration reaction associated with retrograde 
metamorphism enriched these elements with ten times compared to their protolith.  
In Chapter 4-2, fluid-rock reacted zone along lithological boundary of sediment-basalt 
were investigated at the low-grade zone of the Asemigawa River. I revealed the intense fluid-
rock interaction involving element transfer occurred in both lithology, resulting in a remarkable 
change of mineral assemblages in reacted basalt. Based on the detailed mass balance analyses, 
I revealed that pelitic schists recorded mass loss approximately 30% with fluid-mobile element 
depletion (Rb, Li, etc.), indicating that mass loss caused by fluid-rock interaction along 
lithological boundary. Metabasaltic rocks do not show distinct mass changes, but changes in 
mineral assemblages of actinolite disappearance, deceasing content of epidote, and increasing 
content of chlorite, quartz, and muscovite. Associated with mineral assemblage, element content 
are enriched in fluid-mailable element (Rb, Li, etc.). The time-integrated fluid flux calculated 
for each element ranged from 104 to 107 (m3/m2), with average values of 105.64±0.89 (m3/m2) for the 
pelitic schist and 105.50±0.68 (m3/m2) for mafic schist. This assemblage and content changes of 
mineral can vary rheology of lithological boundary, from perspective of mineral friction, altered 
basalt become more weaken with reaction progress. For the perspective of element recycling, 
fluid-deposited carbonaceous material was founded from reacted sedimentary rocks, possibly 
contributing as the carbon carrier to the Earth interior. 
In Chapter 5, I integrated obtained element transfer and fluid volume through analysis 
of seafloor alteration and element transfer integrates the fluid volume obtained in reaction zone 
of lithological boundary of pelitic-mafic schist. Regional-scale analysis using the PRMs revealed 
that element transfer in mafic rocks increased with peak metamorphic conditions, reaching up 
to 90% depletion of mobile elements in the Oligoclase-biotite zone, suggesting increasing time-
integrated fluid flux during prograde metamorphism and heterogeneous flux during retrograde 
metamorphism. Outcrop-scale investigation along a pelitic-mafic schist boundary showed over 
30% mass loss and a fluid flux exceeding 104 (m3/m2), correlating with regional-channelized flow 
and involving both trace and major element transfer. The significantly higher fluid flux at the 
outcrop scale compared to regional estimates indicates that focused fluid flow along lithological 
boundaries, sourced from regionally pervasive dehydration, drives substantial element transfer 
at the plate interface. 
 
（別紙） 
 
論文審査結果の要旨及びその担当者 
 
論文提出者氏名  松野 哲士 
論 文 題 目        
Data-Driven Analyses of Element Transfer within Oceanic Crust During Fluid-Rock Interactions 
at Seafloor and Subduction Plate Interface 
（海洋底・沈み込みプレート境界における岩石-流体相互作用に伴う元素移動のデータ駆動
型解析） 
論文審査担当者 
主査 教 授 岡本 敦  
   教 授 渡邉 則昭  教  授 辻森 樹 (理学研究科) 
   准教授 宇野 正起  教 授 Sarah Penniston-Dorland (メリーランド大学) 
    
 
論文審査結果の要旨 
 
 地球表層の水が岩石と反応して地球内部へと持ち込まれる海洋底から沈み込みプレート境界は，地球内部の物質
循環を駆動する場である．特に，沈み込みプレート境界における岩石と水の反応は，流体圧の上昇や造岩鉱物の変
質，元素輸送など，地震発生や火山生成，元素循環の理解に重要である．しかしながら，地球内部の水や元素の循環
は直接観測できないため，沈み込みプレート境界のどの深度でどの元素がどのくらいの量どの程度局所化して移動
するのかは未だに明らかではない．本研究は，玄武岩質変質岩や変成岩を対象として，近年発達してきた地化学デー
タベースと機械学習および鉱物量比定量化手法を組み合わせたデータ駆動型解析で，海洋底およびプレート境界に
おける元素輸送量，鉱物反応量およびその温度依存性と局所性を明らかにしたもので，全編6章よりなる． 
 
 第１章は序論であり，海洋プレートの沈み込みと岩石―流体反応の重要性，変質・変成岩における元素輸送解析お
よび反応指標，地球化学における機械学習の既往研究についてまとめ，本研究の目的を述べている． 
 第２章は，データ駆動型の元素輸送解析のための手法開発であり，(i) 全球の玄武岩の地化学データベースの機械
学習により，変質・変成した岩石から元の岩石（原岩）の組成を推定する原岩組成復元モデルの構築，(ii) その挙動
を説明する”説明可能なAI”の解析と提示，(iii) 放射光粉末X線回折による全岩鉱物量比定量化手法の開発，を行い，
データ駆動型元素輸送解析に必要な鉱物量データ・元素移動量解析手法を構築した．(i)および(ii)は，変質・変成岩の
個々の原岩組成の推定を可能にした革新的な成果である．また，(iii)は複雑な変成岩の全岩鉱物量比をバイアス無く
迅速かつ大量に定量化できる手法であり，データ駆動型の岩石反応解析の基盤となる重要な成果である． 
 第３章は，複数掘削サイトにおける海洋底変質の元素輸送量を定量化し，海洋底変質の支配要因を明らかにした．
Rb, K 濃度が増加し粘土鉱物が生成する一般的な変質のほか，南太平洋ではBa と U が特異的に増加する酸化的な
変質が局所的に生じること，北西太平洋では比較的還元的な状態でU, PbおよびP が炭酸塩脈に伴い付加されるこ
とを明らかにした．これらは，従来は難しかった複数サイトの海洋底変質の比較をデータ駆動型解析により初めて達
成し，海洋底変質での元素移動は地殻の年齢と堆積物の厚みに支配されることを示した，重要な成果である． 
 第４章は，代表的な沈み込み帯起源の高圧変成帯である三波川帯を対象として元素輸送解析を行い，沈み込みプレ
ート境界での元素輸送を明らかにした．(i)異なる変成度の玄武岩質変成岩に対して，個々の岩石の反応進行度と元素
輸送量を評価することで， Rb, Ba, K, Srは約550℃までの累進変成作用で1/10から1/00程度まで段階的に溶脱す
ること，後退変成作用により10〜100倍程度まで付加されることを示した．(ii) 地震発生帯の下限に相当する320℃
付近の泥質／玄武岩質変成岩の境界において，泥質変成岩側で質量として約30 wt%も失われたこと，玄武岩質変成
岩側では質量の増減は微小なものの，RbやLi, Ba, Csは母岩に比べて250-400%も増加したことを示した．以上は，
プレート境界における元素輸送の温度依存性を反応ステージに基づき分離定量化することに成功し，かつ泥質/玄武
質変成岩境界がプレート境界の主要な流体流路であることを解明した，重要な成果である． 
 第５章は，以上を統合して，海洋底での変質から沈み込みプレート境界での変成作用まで，岩石―流体相互作用に
伴う元素移動を評価し，各元素の挙動と流体流路を示す包括的なモデルを提示した．重要な成果である． 
 第６章は，結論である． 
 
 以上，本論文は，地球内部の元素循環の解析に必要なデータ駆動型アプローチを開発・導入し，海洋底変質から沈
み込みプレート境界の変成作用までの元素移動を，地球化学データと鉱物反応データのデータ駆動解析から明らか
にしたもので，岩石学，地球化学，地球システム科学ならびに環境科学の発展に大いに資するものである． 
 
 よって，本論文は博士(学術)の学位論文として合格と認める． 


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Study on Efficient Exploration for Task-oriented Dialog Policy Learning Based on Reinforcement Learning

田村, 紘一

グラフェンチャネルトランジスタにおけるテラヘルツ電磁波検出の物理機構解明に関する研究

武田, 一希

プラズマ－液体界面における活性種の輸送機構解明

石橋, 一晃

金属薄膜における円偏光誘起テラヘルツ波放射

Tohoku University博士（工学）要約のみthesi

TOJO, AKIKO

論文内容要約 
In recent years, significant attention has been directed toward advancing compact, point-of-care 
testing (POCT) devices to improve patient care and alleviate the burden on the medical care system. 
This also applies to blood gas analyzers, which are crucial for emergency diagnosis. To address this 
trend, we are developing a miniature electrochemical sensor utilizing screen printing technology. In 
electrochemical sensor designs, not only the reduction of sample volume (for reducing the burden on 
patients) and miniaturized devices are important factors, but also a selection of electrode materials 
considering functionality, cost, and environmental impact, as well as the implementation of highly 
selective detection principles to ensure measurement accuracy. However, several challenges persist 
in designing and miniaturizing sensors, 
especially oxygen and enzyme sensors, 
which pose unique difficulties. To 
overcome these challenges, a holistic 
approach encompassing the design of 
electrode materials and the development 
of the sensor as a whole is essential. 
Therefore, we focused on 
graphene-coated porous silica spheres 
(G/PSS), a porous carbon material with 
a thin carbon layer deposited on the pore walls through chemical vapor deposition. G/PSS offers 
high electrical conductivity, uniform spherical particles, and excellent mechanical strength, enabling 
electrode fabrication via screen printing. Additionally, its pores can accommodate target substances, 
such as mediators and enzymes, and the pore size (2-100 nm) can be controlled to the target 
substances. Due to these advantages, G/PSS, which offers tunable pore sizes to match specific 
           とうじょう  あきこ 
氏 名          東 條 朗 子 
研究科，専攻の名称 東北大学大学院工学研究科（博士課程）化学工学専攻 
学 位 論 文 題 目          バイオセンシング応用に向けたカーボンナノ構造体の設計           
論 文 審 査 委 員          主査 東北大学教授 西原 洋知 東北大学教授 笠井 均 
             東北大学教授 長尾 大輔                               
substances and compatibility with mass-production techniques for electrode fabrication, holds great 
potential as an electrode material for biosensors. In this study, we performed trimethylsilylation 
treatment on the surface of PSS, which has an average pore size of 15 nm and a particle size of 10 
µm, using it as a template for the electrode material. The pore size was adjusted to 15 nm to allow 
proteins to enter and serve as a reaction field, while the particle size was set to 10 µm to create gaps 
in the electrode, facilitating diffusion over several micrometers. 
First, we developed a new reference electrode material suitable for small oxygen sensors (Fig. 1a). 
In the process of miniaturizing Clark-type oxygen electrodes by screen printing, the commonly used 
Ag/AgCl electrode causes contamination of the working electrode and device deterioration due to 
silver ion release. To address this issue, we developed a novel electrode material using G/PSS with 
embedded Prussian blue (PB), denoted as PB/G/PSS, specifically designed for a reference electrode 
used in a three-electrode system. PB is a redox species that is an improvement over Ag/AgCl since it 
is significantly less water soluble than AgCl. To load PB within the G/PSS matrix, PB was directly 
synthesized by impregnating the pores of G/PSS with potassium ferrocyanide, followed by the 
addition of iron chloride. Following PB synthesis, the material properties of PB/G/PSS were 
investigated. SEM images and porous characteristics showed no significant differences before and 
after PB synthesis, but ICP analysis detected Fe corresponding PB loading of 1.1 wt%, confirming 
successful incorporation into PB/G/PSS. On the other hand, no peaks were observed in the XRD 
pattern of PB/G/PSS, indicating that the 1.1 wt% of PB was dispersed as tiny clusters undetectable 
by XRD, and the difference in water vapor adsorption between G/PSS and PB/G/PSS further 
supports its high dispersion. In electrochemical analysis, a reversible redox peak was observed by 
cyclic voltammetry and remained in the same curve for 30 days, indicating that PB was working 
effectively without leaching. Furthermore, open circuit potential has been kept constant within 30 
mV for 31 days. These findings demonstrate that PB/G/PSS has excellent potential as a silver-free 
reference electrode. Afterward, we demonstrated a small oxygen sensor (s-OS) assembled through 
screen printing using PB/G/PSS as a reference electrode. The s-OS with PB/G/PSS reference 
electrode operated stably for 5 days without contamination, while the s-OS with Ag/AgCl reference 
electrode rapidly deteriorated within a day due to silver deposition on its working electrode. This 
new PB/G/PSS reference electrode, with enhanced stability, is a promising alternative to Ag/AgCl 
reference electrodes, especially for small electrochemical POCT devices. 
Second, we propose PB/G/PSS as an innovative and cost-effective working electrode for a small 
enzyme sensor targeting H2O2 detection (Fig. 1b). In devices with conventional platinum electrodes, 
overlapping oxygen reduction and ascorbic acid oxidation reactions interfere with the H2O2 
measurements. As a result, ascorbic acid must be physically removed beforehand, and H2O2 is 
typically measured by its oxidation current at high potential. An electrocatalyst that induces distinct 
redox reactions at separate potentials could eliminate the need to filter out ascorbic acid, simplifying 
the device and making it more affordable and compact. Therefore, we investigated the catalytic 
activity of H2O2 and explored its potential as a substitute for platinum, a precious metal. 
Interestingly, we found that the PB/G/PSS electrode has a distinct potential window (-0.1 to -0.05 V), 
devoid of interference from O₂ reduction and ascorbic acid oxidation. This allows for accurate H₂O₂ 
detection through reduction currents, even in the presence of dissolved oxygen and ascorbic acid. 
Applying the PB/G/PSS construct in a device, we showed reliable glucose detection through 
enzyme-mediated reactions in a compact device by screen printing. We further refined the design for 
glucose-sensing applications in biological solutions, targeting future applications in blood-based 
detection. Additionally, leveraging the dual functionality of PB/G/PSS as both a working and 
reference electrode, we successfully demonstrated a fully functional enzyme sensor with noble-free 
electrodes that leverage a streamlined and integrated architecture. This work highlights the 
versatility and potential of PB/G/PSS electrodes in advancing next-generation biosensor 
technologies. 
 Finally, we evaluated the electrochemical properties of Fe-incorporated ordered carbon frameworks 
(OCFs) to mimic biological reactions. Heme, an iron-centered porphyrin complex found in 
hemoproteins, plays a key role in oxygen transport, storage, activation, and gas sensors (Fig. 1c). 
While numerous biomimetic nanostructures, including heme, have been developed, these systems 
lack the ability to hierarchically organize nanocomponents, which is a critical requirement for 
reproducing the functional complexity of natural heme proteins. Natural hemoproteins have been 
investigated as electrode materials, utilizing their exceptional selectivity and reactivity to drive 
reactions that are difficult or unattainable with conventional catalysts. However, proteins have a 
limited number of active centers, such as Hb with only four, which limits their reaction efficiency. 
To overcome this, we focus on a molecular design approach. By incorporating the concept of 
artificial enzymes and constructing electrodes with porphyrin-based materials, we aim to mimic 
biological reactions while preserving structural frameworks and active sites. This approach could 
open up new possibilities beyond natural protein. We focused on OCFs, carbon materials with 
well-defined three-dimensional structures, as frameworks for mimicking biological reactions. Our 
group successfully synthesized various OCFs with single-atomic metal species. Fe-incorporated 
OCFs, with more active sites than heme and electrical conductivity due to their carbonized 
framework, are a promising candidate for an ideal artificial enzyme. We synthesized Fe-based cyclic 
porphyrin (denoted as 1np) and carbonized them at 600 °C (denoted as 1np_600). The carbonization 
yield was high, reaching 94 wt%, and the XRD pattern revealed that the ordered structure was 
preserved even after carbonization. To examine the electrochemical behavior, electrodes were 
prepared by mixing 1np or 1np_600 with carbon paste. The CV curves for 30 cycles revealed that 
carbonization improved electrode stability. We also investigated the catalytic activity of H2O2. The 
redox current of H2O2 was observed in the CV curve of 1np_600, and the reduction current increased 
linearly up to 2.5 mM by chronoamperometry. 1np_600 demonstrated electron transfer and H₂O₂ 
catalytic functions, key properties of hemoproteins, and shows promise as a next-generation 
electrode material for detecting H2O2. 
 In summary, we explored the potential of carbon nanostructures in biosensing applications. We 
successfully developed highly crystalline PB-loaded G/PSS and a metal-leaching-free reference 
electrode, significantly enhancing the operational lifespan of miniaturized oxygen sensors. We 
demonstrated that PB/G/PSS electrodes are capable of quantifying H2O2 even in the presence of 
ascorbic acid, and developed a noble-metal-free enzyme sensor. Additionally, we synthesized 
“hemoprotein-like OCFs”, with retained porphyrin framework and active center, mimicking 
biological reactions for sensing applications. The sensor showed remarkable electrochemical 
stability and high catalytic activity toward H2O2, confirming its potential for future biosensing 
applications. 
 


バイオセンシング応用に向けたカーボンナノ構造体の設計

HIRASE, Shotaro

【Symposium mini review】The Model of Marine Speciation: Evolution of Abalone Species due to Vertical and Horizontal Heterogeneity in Coastal Environments

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