名前を赤で表記しているメンバーは当研究室の学生・院生、青で表記しているメンバーは当研究室の教員です。
原著論文
- Azmi Alvian Gabriel, Tetsu Yonezawa
Salt-stable ZnO Nanoparticles Stabilized by Citric-acid-crosslinked Canna edulis ker. Starch
International Journal of Biological Macromolecules, in press.【Elsevier】（IF = 8.5）
DOI: 10.1016/j.ijbiomac.2026.152130（Published (web) 22 April 2026）
【研究室内研究】
Abstract: This study examines how citric acid crosslinking density in Canna edulis ker. starch (CEkS) governs electrosteric stabilization of ZnO nanoparticles under saline stress. Citric acid–modified CEkS polymers spanning degrees of substitution (DS = 0.26–0.67) were synthesized and used to cap ZnO nanoparticles via aqueous co-precipitation. FTIR and XRD confirmed ester formation and ZnO crystallinity, while thermal analysis indicated enhanced thermal resilience of the crosslinked polymer–ZnO system. Colloidal stability was quantified by hydrodynamic diameter (DLS), zeta potential, and UV–Vis turbidity during storage across 0–200 mM NaCl. An intermediate-crosslinked formulation (CA35%) provided the most robust salt tolerance: at 200 mM NaCl, CA35% reached 1271 ± 5 nm after 7 days, whereas the non–modified CEkS control grew to 2633 ± 18 nm. In salt-free dispersions, CA35% remained 301 ± 2 nm at 7 days, while the control reached 2896 ± 6 nm. Higher-crosslinked samples formed stiffer shells that were less tolerant to ionic compression, accelerating aggregation despite more negative surface charge. Overall, the results establish a practical crosslinking–stability design rule for polysaccharide-capped ZnO nanocolloids in ionic media and provide a foundation for subsequent, application-specific validation where safety or regulatory testing is required.
- Po-Keng, Hsiao, Yen-Lun Kung, Yun-Pei Liu, Shihwen Tseng, Tetsu Yonezawa, Chun-Hu Chen, Ying-Chih Pu
Universal Interfacial Engineering via Amorphous Inorganic Binders: Passivating Surface States and Accelerating Hole Transfer across Metal Oxide Photoanodes in Photoelectrochemical Water Oxidation
The Journal of Physical Chemistry Letters, in press.【ACS】（IF = 4.7）
DOI: 10.1021/acs.jpclett.6c00767 （Published (web) 17 April 2026）
【国際共同研究】
Abstract: Interfacial engineering of photoanodes is essential for efficient solar water splitting; however, many existing strategies rely on complex, multistep processes or hydrothermal growth, limiting scalability and reproducibility. Here, we present a universal interfacial engineering platform based on a sub-2 min acidic redox-assisted deposition (ARD) of an amorphous inorganic binder, cobalt–manganese oxyhydroxide (CMOH). Using two-step-fabricated BiVO4 as a literature-standard benchmark, we demonstrate that an ultrathin CMOH overlayer markedly enhances photoelectrochemical (PEC) water oxidation performance. The conformal CMOH coating (∼3.5 nm) is deposited under ambient conditions via a simple dip-coating process and is broadly applicable to metal oxide photoanodes, including BiVO4, WO3, and ZnO. The CMOH-modified BiVO4 photoanode delivers a high photocurrent density of ∼6.0 mA cm–2 and a hole-transfer efficiency of ∼82% at 1.23 VRHE, together with a remarkable applied bias photon-to-current efficiency (ABPE) of 1.68% at 0.66 VRHE. These enhancements originate from effective surface-state passivation by the CMOH overlayer, leading to over a 4-fold reduction in the surface recombination rate constant, as revealed by intensity-modulated photocurrent spectroscopy (IMPS). In addition, the reduced Tafel slope (78.5 mV dec–1) suggests that the CMOH layer promotes interfacial charge transfer and enhances the water oxidation kinetics of the BiVO4 photoanode. This work elucidates the critical role of amorphous CMOH oxygen evolution catalysts in mediating photoinduced charge-carrier dynamics and establishes a facile and scalable strategy to broadly enhance the PEC performance of metal oxide photoanodes for large-scale solar fuel production.
- Tetsu Yonezawa, Qianhao Zuo
Copper Particle Sintering for Low-Temperature Electronic Joining: A Review of Materials Design and Processing Strategies【Review】
Advanced Engineering Materials, in press.【Wiley】（IF = 3.3）
【研究室内研究】
Abstract: Low-temperature copper (Cu) sinter-bonding has emerged as a promising alternative for conductive layers in electronic parts and die-attachment in power electronics packaging, particularly for packaging wide-bandgap (WBG) semiconductors such as silicon carbide (SiC) and gallium nitride (GaN). WBG devices operate at higher temperatures and require bonding materials with superior thermal and mechanical properties. Compared to conventional soldering techniques, Cu sinter-bonding offers enhanced electrical and thermal conductivity, better resistance to electrochemical migration, and lower material costs. However, challenges such as the oxidation of Cu particles, achieving optimal densification, and controlling processing conditions must be addressed for its widespread application. In this review, the mechanisms of Cu sinter‐bonding, key sintering parameters, and recent advances in Cu paste formulations, including surface modification, hybrid particle systems, and alloying with additional metals, are summarized. Optimization strategies for pressure, temperature, solvent, atmosphere, and substrate metallization to improve the performance of Cu joints are discussed in detail. The potential of Cu sinter-bonding in next-generation electronic packaging is analyzed, along with challenges and future research directions.
- Phonnapha Tangthuam, Vipada Aupama, Manaswee Suttipong, Tae-Kyu An, Insik In, Tetsu Yonezawa, Dowon Bae, Li-Hsien Yeh, Soorathep Kheawhom
From Molecule to Stack: A Cross-Scale Design Framework for Aqueous Organic Redox Flow Batteries【Review】
Batteries and Supercaps, 9(5), e70301 (2026). 【Wiley】（IF = 4.7）DOI: 10.1002/batt.70301 （Published (web) 21 April 2026）【国際共同研究】
Abstract: Aqueous organic redox flow batteries (AORFBs) have emerged as promising candidates for long-duration grid-scale energy storage due to their decoupled power-energy architecture and the tunability of organic redox-active molecules. Rapid progress across molecular design, membranes, electrodes, and system engineering has produced a diverse but largely compartmentalized body of literature, in which structure-property relationships are often analyzed in isolation. In this review, we present a cross-scale design framework that connects molecular descriptors to interfacial processes and, ultimately, to device-level performance constraints. We compare major classes of organic redox-active molecules, including quinones, viologens, phenazines, nitroxide radicals, and imides, and examine how substituent engineering governs redox potential, solubility, stability, and viscosity. These molecular characteristics are then linked to electrolyte transport, membrane selectivity, and electrode kinetics, highlighting how coupled phenomena such as crossover, aggregation, and viscosity-mass transfer limitations emerge under practical operating conditions. Building on this framework, we analyze how membrane swelling, charge-state-dependent partitioning, and electrode-molecule interactions jointly determine efficiency, lifetime, and degradation pathways. We further discuss system-level constraints arising from concentration-dependent viscosity, mass transport limitations, and crossover-driven state-of-charge imbalance. Finally, we propose deployment-relevant benchmarking metrics and reporting practices and outline key directions for advancing molecular stability, selective membranes, and viscosity-aware system design. - Amogelang G. Metseeme, Thabakgolo T. Letsau, Shidong Song, Tetsu Yonezawa, Phumlani F. Msomi
Anion exchange membranes for electrically rechargeable zinc–air batteries: Structure-transport-degradation relationships and design strategies【Review】
Next Materials, 12, 102025 (2026). 【Elsevier】【Open Access】
DOI: 10.1016/j.nxmate.2026.102025 (Published (web) 7 April 2026)
【国際共同研究】
Abstract: Electrically rechargeable zinc–air batteries (ERZABs) are promising for grid and mobility energy storage due to zinc’s abundance, high theoretical capacity, and relatively benign chemistry. A critical component governing their performance is the anion exchange membrane (AEM), which must efficiently conduct hydroxide ions while suppressing zincate crossover and maintaining stability in strongly alkaline environments. This review examines how polymer structure, cation chemistry, water management, and microphase morphology collectively influence hydroxide transport and long-term durability. Particular attention is given to the interplay between ion exchange capacity, water uptake, conductivity, and dimensional stability, as well as the role of membrane microstructure in controlling multivalent ion transport. Advances in membrane fabrication strategies, including crosslinking, blending, pore-filling, and electrospinning, are evaluated in terms of their impact on transport and mechanical integrity. Recent developments in ether-free polyaromatic backbones and sterically protected cations have enabled hydroxide conductivities exceeding 100 mS cm⁻¹ at elevated temperatures with improved alkaline stability. However, many reported values are obtained under fully hydrated conditions and may not directly reflect ERZAB operation, where carbonation, hydration gradients, and cycling stresses influence performance. By linking polymer design to ion transport, degradation behavior, and device-level constraints, this review provides a structured perspective on AEM development and identifies key considerations for achieving durable and efficient ERZAB systems.
- Yi Zheng, Hiroki Tsukamoto, Tetsu Yonezawa
Low‑Temperature Sintering Copper Inks: In- Situ X‑Ray Diffraction of Decomposition, Enhanced Conductivity and Morphology, and Nickel‑Improved Weather Resistance
ChemNanoMat, 12(4), e202500768 (2026).【Wiley】（IF = 2.6）
DOI: 10.1002/cnma.202500768（Published（web）17 April 2026）
【研究室内研究】
Abstract: We present a metal–organic decomposition (MOD) copper ink based on copper formate and 1-amino-2-propanol (MIPA), with octylamine (OA) as a printability modifier and nickel formate as an antioxidation additive. X-ray diffraction (XRD) indicates complex formation and storage stability at low temperature, while Fourier-transform infrared (FT-IR) confirms coordination of MIPA to CuF. Thermogravimetric–differential thermal analysis (TG–DTA) shows that the CuF/MIPA/OA complex lowers the decomposition temperature from 215°C (CuF) to ∼130°C; in-situ XRD detects metallic Cu even at ∼120°C. Copper films sintered on alumina under nitrogen exhibit decreasing resistivity with increasing temperature below 200°C, reaching 2.86 × 10−5 Ω·cm at 180°C for a CuF:MIPA:OA molar ratio of 1:1.3:0.8. Scanning electron microscope (SEM) reveals progressive densification with temperature. Incorporating NiF (5–10 wt%) increases the initial resistivity but markedly improves weather resistance over 35 days. These results establish a coherent low-temperature route to copper metallization and elucidate how complex chemistry and Ni addition govern conductivity and durability.