【公開日：2025.07.10】【最終更新日：2025.07.10】

課題データ / Project Data

課題番号 / Project Issue Number

23NM5403

利用課題名 / Title

金属酸化物の界面結合とナノ粒子分散性の向上

利用した実施機関 / Support Institute

物質・材料研究機構 / NIMS

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）物質・材料合成プロセス/Molecule & Material Synthesis（副 / Sub）-

【重要技術領域 / Important Technology Area】（主 / Main）マテリアルの高度循環のための技術/Advanced materials recycling technologies（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

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)

武田 良彦

所属名 / Affiliation

物質・材料研究機構

共同利用者氏名 / Names of Collaborators Excluding Supporters in the Hub and Spoke Institutes

Kim Minsung,廣瀬 玉紀

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

服部 晋也,伊坂 紀子

利用形態 / Support Type

（主 / Main）機器利用/Equipment Utilization（副 / Sub）,技術代行/Technology Substitution

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

NM-503：200kV電界放出形透過電子顕微鏡（JEM-2100F1）
NM-003：ラマン顕微鏡
NM-011：フーリエ変換赤外分光光度計
NM-013：ゼータ電位計
NM-014：動的光散乱光度計

報告書データ / Report

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

Tungsten oxide exhibits photochromic properties and is considered a promising material in various fields such as sensors, smart windows, and medical imaging due to its low manufacturing cost, simple synthesis methods, and chemical stability. However, it is still in the early stages of practical application due to its lower photochromic efficiency compared to other photochromic materials and its poor dispersion in solvents. To address these issues, titanium dioxide (TiO₂) was introduced to enhance the photochromic properties of tungsten oxide, and a solution-based coating method, capable of easily producing stable films, was selected. To improve the stability in organic solvents, an organic ligand was introduced. The synthesized tungsten oxide particles were analyzed using TEM to understand their structure. Additionally, the binding with the organic ligand (polyvinylpyrrolidone) was confirmed through FT-IR and Raman analyses. Finally, to assess the solvent dispersion of the ultimately synthesized material, Zeta-potential analysis and Dynamic Light Scattering (DLS) were conducted to confirm the stability of particles in the solvent. The objective of this research is to investigate the internal structure of the synthesized materials, confirm the intermolecular binding states, and understand the detailed structures and mechanisms.

実験 / Experimental

The tungsten oxide powder synthesized through hydrothermal method at the Organic Photo-functional Materials Laboratory at Seoul National University was utilized in this study. TEM analysis was conducted for morphology confirmation. Additionally, to verify the binding with organic compounds, Raman and FT-IR measurements were performed. Finally, for the assessment of the stability of the synthesized tungsten oxide particles in solution, Dynamic Light Scattering and Zeta-potential analyses were carried out. In addition, NM-504_TEM 200kV電界放出形透過電子顕微鏡 [JEM-2100F2] , NM-505_TEM 200kV透過電子顕微鏡 [JEM-2100] and NM-516 TEM試料作製装置群 [TEM sample preparation apparatus] were also used.

結果と考察 / Results and Discussion

Firstly, TEM analysis was conducted to confirm the morphology of tungsten oxide (Fig. 1). The synthesized tungsten oxide exhibits a plate-like shape with an approximate size of 30 nm. The lattice parameters were determined by XRD measurements to be a = 3.85 Å and c = 6.7 Å, matching the lattice parameters of a hexagonal structure. The image matched the results obtained from XRD. Additionally, to examine the distribution concerning the introduction of TiO₂, WO₃/TiO₂ composite materials were investigated (Fig. 2). When the TiO₂ input molar percentage exceeds approximately 10%, it surrounds and covers the tungsten oxide particles. This observation suggests that excessive TiO₂ can adversely affect the photochromic properties influenced by light, with an optimal input quantity of around 3%. Furthermore, the synthesized structure reveals that TiO₂ particles exhibit a square shape with an approximate size of 20 nm. It was observed that these TiO₂ particles are not encapsulating the tungsten particles but rather adhering to the surface in an adsorbed manner. To enhance the solvent dispersion, polyvinylpyrrolidone (PVP), serving as a dispersant, was introduced. To confirm this binding, RAMAN and FT-IR analyses were conducted (Fig. 3). In Fig.3., the peaks at 185, 256, 695, and 804 cm^-1, which correspond to hexagonal tungsten oxide, were observed. When combined with PVP, in Fig. 3(b), a peak in the range of 1590 to 1600 cm^-1 was observed, and a shoulder peak around 1380 cm^-1 was detected, which is anticipated to be a shoulder peak resulting from the bonding with WO₃. Observing the shoulder peaks and peaks of PVP, it is expected that WO₃ is combined with PVP. Also, in Fig.4., when comparing the green WO₃ graph to the blue WO₃/PVP graph, a slight shift from 1640 cm^-1 to 1649 cm^-1 is observed for the C=O bond peak of PVP. Furthermore, this shifted peak at 1651 cm-1 is also evident in the red WO₃/TiO₂/PVP graph. Additionally, comparing the C-N peak at 1296 cm^-1, slight shifts to 1288 cm^-1 and 1290 cm^-1 are observed. Notably, the stretching modes of the C=O at the binding end of PVP main peaks exhibit shifts in the range of 5 ~ 10 cm^-1, indicating formation in the adsorbed state. Based on the results, it was observed that there is only a slight shift in the peaks without the generation of new peaks or significant shifts, indicating that the introduced polyvinylpyrrolidone is formed in an adsorbed form on the surface.To assess the dispersion of the finally synthesized tungsten oxide/TiO₂/PVP particles in organic solvents, Zeta-potential analysis and Dynamic Light Scattering (DLS) were performed. First, in Fig.5., Zeta-potential analysis was conducted. The solvent used was ethanol, and measurements were taken three times, with the average values calculated. For only WO₃, the Zeta potential was approximately 28.8 mV, for WO₃/PVP it was 70.2 mV, for WO₃/TiO₂ it was 28.4 mV, and for the final substance WO₃/TiO₂/PVP, the Zeta potential was 68.3 mV. (Table 1) Generally, the solvent stability of metal oxide particles can be assessed based on a 30 mV criterion, distinguishing between stability and instability in solvents. From the results, those without the introduction of PVP showed values below 30 mV, indicating instability. In contrast, all cases with PVP exhibited values above 30 mV, confirming stability in organic solvents. Furthermore, to verify stability, Dynamic Light Scattering (DLS) measurements were conducted (Fig. 6). DLS involves illuminating particles undergoing Brownian motion in a solvent and measuring the reflected light to indirectly determine particle size. Generally, a narrower distribution and smaller size indicate greater stability. The results indicate that introducing PVP resulted in smaller particle sizes, suggesting enhanced stability in the solvent. (Table 2) While this provides indirect evidence of the trend, it confirms that the solvent stability was improved with the introduction of PVP.

図・表・数式 / Figures, Tables and Equations

Fig. 1. TEM analysis of the synthesized WO₃. The lattice parameter of (002) lattice is approximately 0.36 nm.

Fig. 2. TEM analysis of the synthesized WO₃. (a) only WO₃, (b) 3%, (C), 10%, (d)20%, and (e) encapsulated WO₃ by PVP. The size of the synthesized WO₃ is 30nm, plate-structure and TiO₂ is 20 nm, rectangular structure.

Fig. 3. (a) tungsten oxide particles, (b) tungsten oxide with polyvinylpyrrolidone

Fig. 4. FT-IR analysis. (Left) Wide range 4000 ~ 400 cm^-1 (right) 2000 ~ 1250cm^-1

Fig. 5. Zeta potential analysis of (a) WO₃, (b) WO₃/PVP, (c) WO₃/TiO₂, and (d)WO₃/TiO₂/PVP

Table 1. The average value of Zeta potential analysis

Fig. 6. Dynamic light scattering analysis of the synthesized materials. (a) WO₃,(b) WO₃/PVP, (c) WO₃/TiO₂, and (d) WO₃/TiO₂/PVP

Table 2. Distribution of the particles from dynamic light scattering analysis

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

We would like to express my gratitude to Dr. Isaka Noriko for her assistance in facilitating TEM analysis. Additionally, I extend my thanks to Dr. Hattori Shinya and Ms. Maruhashi Keiko for their support and guidance during the initial measurements and learning processes with the equipment.

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)

1. Min Sung Kim, Binder-enhanced reversible photochromic films by tungsten oxide hybrid composites for advanced applications, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 703, 135118(2024).
   DOI: 10.1016/j.colsurfa.2024.135118
   
2. Min-Sung Kim, Amplifying Photochromic Response in Tungsten Oxide Films with Titanium Oxide and Polyvinylpyrrolidone, Nanomaterials, 14, 1121(2024).
   DOI: 10.3390/nano14131121
   

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

特許 / Patents

特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件