Graduate School of Advanced Science and Engineering, Waseda University
༤
༤ 㻌 ኈ 㻌 ㄽ 㻌 ᩥ 㻌 ᴫ 㻌 せ
Doctor Dissertation Synopsis
ㄽ ᩥ 㢟 ┠
Synthesis and Applications of Mesoporous Metal Oxide Films with Various Pore Architectures
⏦ ㄳ ⪅ (Applicant Name)
Xiangfen JIANG
ⵓ •ⰷ
(Major in Nanoscience and Nanoengineering, Research on Synthetic Chemistry of Nanomaterials)
May 2013
The synthesis of ordered mesoporous materials has attracted tremendous attention in the materials community. Among various morphologies of mesoporous materials, ordered mesoporous films are very attractive for applications in electronics, optics, sensing, etc. Control of the pore architectures in the films, such as vertical mesoporosity and large-sized mesopores, has a significant effect on performance in these applications.
Compared to closed pores and cage-type pores, connected mesoporosity allows more effective pore utilization.
In particular, vertically connected mesoporosity is much more desirable than horizontally connected mesoporosity, because the vertical orientation exhibits better diffusion of the guest species into the inner mesospace. Unfortunately, 2D hexagonal mesostructures generally tend to lie on the substrate surface. Although some special techniques, such as use of a patterned substrate and magnetic field, have been applied to the creation of vertical mesoporosity in mesoporous silica films, the preparation of mesoporous films with vertical mesoporosity is still very challenging and requires further studies.
In addition to the pore orientation, it is also very important to fabricate large mesopores since they facilitate the diffusion of guest molecules and can be utilized in emerging applications such as biotechnology involving large target species. In principle, the pore size is determined by the templating micelle.
Using long chain surfactants of high molecular weight enables fabrication ofordered large-sized mesoporous materials. In previous work, some amphiphilic block copolymers, such as Pluronic P123 and F127 (PEO-PPO-PEO type), have been extensively used as the templates. However, the obtained mesopore sizes prepared with P123 or F127 templates have been limited to at most 8 nm, due to relative small differences in hydrophobicity between the two blocks and limitations in molecular weight. These mesoporous films prepared with PEO-PPO-PEO-type block copolymers have been utilized as a matrix for large guest species such as dye molecules, conjugated polymers, and small-sized proteins, but mesopore sizes smaller than 10 nm limit their applications, especially toward biotechnology in which large bulky species are involved. Therefore, it is necessary to prepare thin films with large pores for such applications. Several efforts have focused on increasing the pore size. Adding hydrophobic swelling agents, which can enter hydrophobic parts of the block copolymers, can result in pore size expansion. However, the pore expansion by swelling agents is usually limited to 12 nm with retention of high pore order. Meanwhile, it has been proven that block copolymers with high molecular weights and big differences in hydrophobicity between the blocks can be directly utilized for the formation of large mesopores. Nevertheless, a more facile and straightforward process for synthesizing ordered mesoporous thin films with desired mesoporous architectures is still needed.
In my PhD program, I have focused on the rational design of mesoporous metal oxide films with various pore architectures, including vertical mesoporosity and large-mesopores. I have also successfully demonstrated several applications to emphasize the significance of the obtained well-defined films.
Chapter 1gives the background for my studies. The synthesis of ordered mesoporous thin films with various compositions and the challenges, especially in terms of controlling pore orientation and pore size, are reviewed. Their applications are also systematically reviewed.
Chapter 2 shows the preparation of highly ordered mesoporous alumina thin ¿OPV and alumina-doped titania thin films with partial vertical mesoporosity by using a triblock copolymer Pluronic
P123 as the structure-directing agent. 2D grazing-incidence small-angle X-ray scattering (GI-SAXS) and cross-sectional electron microscopy proves the existence of two different mesopore structures (i.e., [001]-oriented P63/mmc and [111]-oriented Fm-3m symmetries). During the thermal decomposition and crystallization process, large uniaxial shrinkage occurs along the direction perpendicular to the substrate with the retention of horizontal mesoscale periodicity, thereby resulting in the formation of partial vertical mesoporosity in the¿OPThe obtained mesoporous Ȗ-alumina ¿OPshows high thermal stability up to 1000oC, which is highly useful in a wide range of research areas such as catalyst supports and separators. For the alumina-doped titania thin films, the Al content is uniformly doped into the framework up to 15 atomic percent without deteriorating the original ordered mesostructure. Because the uniformly doped Al content can prevent rapid crystal growth of anatase, the thermal stability of mesostructures gradually increases with increasing doped Al content. The above mesostructural conversion by thermal treatment is a very effective method for creating vertical mesoporosity.
Chapter 3 extends the concept to Pluronic F127-templated alumina thin films. In this case, the spherical micelles are stacked as [001]-oriented and [111]-oriented Im-3m, which are identified by GI-SAXS, together with top and cross-sectional observations of as-prepared films and calcined films at various temperatures. It is observed that over 80% of contraction occurred along the vertical direction in the final Ȗ-alumina thin film, and the primary cage-type mesopores are gradually diffused into vertically connected mesochannels as crystallization proceeds. This is the first report of ordered mesoporous Ȗ-alumina thin films combined with vertical mesoporosity and a crystalline framework with good thermal stability. The mesostructural conversion from anIm-3mmesostructure can prepare perfectly straight mesoporosity without any defects, in contrast to that from P123-templated films. The synthetic process is expected to be developed for other metal oxides in the future. This fascinating vertical mesoporosity can facilitate the incorporation of guest species, thus expanding the range of possible applications.
Chapter 4 describes two potential applications using mesoporous films with vertical mesoporosity.
Ordered mesoporous alumina-doped titania thin films with vertical mesoporosity (prepared in Chapter 2) are used to accommodate and confine leuco dyes. Due to the big differences in crystalline nature between dopant alumina and matrix titania, it is believed that the anatase pillars are covered by amorphous alumina layers. Due to this core-shell-like structure, dye molecules can be stably confined in the mesopores, avoiding decomposition by photocatalysis. As a result, we can realize a high-speed and high-quality passive matrix electrochromic display (ECD), which is a promising candidate for a reflective display device in the future. Meanwhile, ordered mesoporous Ȗ-alumina films with vertical mesoporosity (prepared in Chapter 3) are applied as the matrix for aligning conjugated polymer poly(9,9-di-noctylfluorenyl-2,7-diyl) (PFO). The PFO chains are simply drop-casted on the alumina thin film, and the resulting composite film shows significant anisotropic photoluminescence, indicating that the PFO backbones are successfully oriented along the vertical mesoporosity of alumina thin film matrix. Thus, vertical mesoporosity is very useful for several electrical applications, compared to normal mesoporous films with lying mesochannels.
Chapter 5shows the preparation of ordered mesoporous alumina films and titania thin films with large
mesopores (~ 30 nm). In both cases, PS(18000)-b-PEO(7500) of high molecular weight is selected as the structure-directing agent. Several systematic studies of the mesostructural formation reveal that the addition of ethanol has a significant effect on the formation, uniformity, and ordering of mesopores, with controlled hydrolysis and condensation of inorganic precursors. With an optimized amount of ethanol as co-solvent, there is no significant change in the micelle morphology that is formed on the substrate, even though the relative amount of PS-b-PEO to alumina source is dramatically varied. When the amount of alumina precursor is decreased, the pore walls gradually become thinner, thereby improving the pore connectivity. The ordered mesoporous alumina films obtained in this study exhibit high thermal stability up to 1000 oC, and their frameworks are successfully crystallized to the Ȗ-alumina phase. This technique is also applicable for the fabrication of highly ordered mesoporous titania films where titanium alkoxide (titanium tetra-isopropoxide or titanium tetra-n-butoxide) is used as the titanium precursor.
Chapter 6shows an extension of the above PS-b-PEO-based synthesis to mesoporous BaTiO3 film.
BaTiO3is well known as a non-toxic ferroelectric material. Its ferroelectric transition temperature Tcis about 130
oC, which is too low for practical use. Besides the composition substitution, introducing strain via the substrate or another composition have been proven to effectively increase the Tc. Mesopores with a pore diameter of ~ 25 nm can be observed in the amorphous film calcined at 400 oC and are directly templated by the PS-b-PEO micelles. When the thermal annealing temperature is increased, significant mesostructure change occurs, accompanied by crystallization of the amorphous framework into a tetragonal phase (P4mm). Even though the original pore structure is slightly altered, the newly reconstructed framework still contains mesoporosity. The mesostructured BaTiO3 film shows the strongest dielectric properties, and its temperature-dependent dielectric constant indicates that the Tccan be as high as 468 oC, compared to 130 oC for the corresponding BaTiO3 film without mesostructures. This enhancement is attributed to the control of strain by introducing well-organized mesostructures, which is not attainable in poorly-ordered mesoporous films. Thus, well-ordered mesoporous films with desired compositions can enable a variety of functions in the future.
Chapter 7 summarizes and concludes all my results on mesoporous thin films with vertical mesoporosity and large mesopores. Through this PhD work, I would like to show the significance of nanoscale control on pore architectures for various applications. I believe that my studies on these topics fill in important gaps in several research areas and provide insight for related research.
No. 1
᪩
᪩✄⏣Ꮫ ༤ኈ㸦ᕤᏛ㸧 Ꮫ⏦ㄳ ◊✲ᴗ⦼᭩
(List of research achievements for application of doctorate (Dr. of Engineering), Waseda University)
Ặ ྡ Xiangfen JIANG ༳
㸦As of July 16, 2013㸧
✀ 㢮 ู(By Type)
㢟ྡ㸪Ⓨ⾲࣭Ⓨ⾜ᥖ㍕ㄅྡ㸪Ⓨ⾲࣭Ⓨ⾜ᖺ᭶㸪㐃ྡ⪅㸦⏦ㄳ⪅ྵࡴ㸧 (theme, journal name, date & year of publication, name of authors inc. yourself)
(1) Paper
ż
1. Controlled Synthesis of Well-Ordered Mesoporous Titania Films with Large Mesopores Templated by Spherical PS-b-PEO MicellesEuropean Journal of Inorganic Chemistry,2013, 2013, 3286-3291. (June 5, 2013).
Xiangfen Jiang, Norihiro Suzuki,Bishnu Prasad Bastakoti, Wei-Jung Chen, Yu-Tzu Huang, and Yusuke Yamauchi
ż
2. Preparation of Ordered Mesoporous Alumina-Doped Titania Films with High Thermal Stability and Their Application to High-Speed Passive-Matrix Electrochromic DisplayChemistry-A European Journal, DOI: 10.1002/chem.201300737. (June 28, 2013).
Xiangfen Jiang, Bishnu Prasad Bastakoti, Wu Weng, Tetsuya Higuchi, Hamid Oveisi, Norihiro Suzuki, Wei-Jung Chen, Yu-Tzu Huang, and Yusuke Yamauchi
ż
3. Synthesis of Continuous Mesoporous Alumina Films with Large-Sized Cage-Type Mesopores by Using Diblock CopolymersChemistry-An Asian Journal,2012, 7, 1713-1718. (March 2, 2012)
Xiangfen Jiang, Norihiro Suzuki, Bishnu Prasad Bastakoti, Kevin C.-W. Wu, and Yusuke Yamauchi
ż
4. Vertically-oriented Conjugated Polymer Arrays in Mesoporous Alumina via Simple Drop-casting and Appearance of Anisotropic PhotoluminescenceChemical Communications,2012, 48, 549-551. (January 14, 2012)
Xiangfen Jiang, Atsushi Ishizumi, Norihiro Suzuki, Masanobu Naito, and Yusuke Yamauchi
ż
5. Synthesis of Highly Ordered Mesoporous Alumina Thin Films and Their Framework&U\VWDOOL]DWLRQWRȖ-Alumina Phase
Dalton Transactions,2011, 40, 10851-10856. (May 23, 2011)
Xiangfen Jiang, Hamid Oveisi, Yoshihiro Nemoto, Norihiro Suzuki, Kevin C.-W. Wu, and Yusuke Yamauchi
ż
6. A MesoporousȖ-Alumina Film with Vertical Mesoporosity: The Unusual Conversion from a Im-3mMesostructure to Vertically OrientedȖ-Alumina NanowiresAngewandte Chemie-International Edition,2011, 50, 7410-7413. (January 17, 2011)
Hamid Oveisi#,Xiangfen Jiang#, Masataka Imura, Yoshihiro Nemoto, Yasuhiro Sakamoto, and Yusuke Yamauchi (#equally contributed)
ż
7. Synthesis of Continuous Mesoporous Ga-Doped Titania Films with Anatase Crystallized FrameworkJournal of Nanoscience and Nanotechnology,2011, 11, 6926-6933. (January 31, 2011)
Hamid Oveisi#, Ali Beitollahi, Xiangfen Jiang#, Keisuke Sato, Yoshihiro Nemoto, Naoki Fukata, and Yusuke Yamauchi (#equally contributed)
8. Electrochemical Synthesis of Transparent, Amorphous C60-Rich Photoactive Low Doped Film with Interconnected Structure
Small,2013, 9, 2064-2068. (January 29, 2013)
Mao Li, Shinsuke Ishihara, Kei Ohkubo, Meiyong Liao, Qingmin Ji, Cheng Gu, Yuyu Pan, Xiangfen Jiang, Misaho Akada, Jonathan P. Hill, Takashi Nakanishi, Yuguang Ma, Yusuke
No. 2
᪩
᪩✄⏣Ꮫ ༤ኈ㸦ᕤᏛ㸧 Ꮫ⏦ㄳ ◊✲ᴗ⦼᭩
(List of research achievements for application of doctorate (Dr. of Engineering), Waseda University)
✀ 㢮 ู(By Type)
㢟ྡ㸪Ⓨ⾲࣭Ⓨ⾜ᥖ㍕ㄅྡ㸪Ⓨ⾲࣭Ⓨ⾜ᖺ᭶㸪㐃ྡ⪅㸦⏦ㄳ⪅ྵࡴ㸧 (theme, journal name, date & year of publication, name of authors inc. yourself)
(2) Presentation
Yamauchi, Shunichi Fukuzumi, and Katsuhiko Ariga
9. Formation of secondary Moire patterns for characterization of nanoporous alumina structures in multiple domains with different orientations
Nanoscale,2013, 5, 2285-2289. (February 7, 2013)
Qinghua Wang, Satoshi Kishimoto, Xiangfen Jiang, and Yusuke Yamauchi
10. Hybridization of Photoactive Titania Nanoparticles with Mesoporous Silica Nanoparticles and Investigation of Their Photocatalytic Activity
Bulletin of the Chemical Society of Japan,2011, 84, 812-817. (June 25, 2011)
Norihiro Suzuki,Xiangfen Jiang, Logudurai Radhakrishnan, Kimiko Takai, Kotaro Shimasaki, Yu-Tzu Huang, Nobuyoshi Miyamoto, and Yusuke Yamauchi
11. New Trend on Mesoporous Films: Precise Controls of One-dimensional (1D) Mesochannels toward Innovative Applications
Journal of Materials Chemistry,2011, 21, 8934-8939. (April 26, 2011) Kevin C.-W. Wu,Xiangfen Jiang, and Yusuke Yamauchi
12. Improved Inactivation Effect of Bacteria: Fabrication of Mesoporous Anatase Films with Fine Ag Nanoparticles Prepared by Coaxial Vacuum Arc Deposition
Chemistry Letters,2011, 40, 420-422. (April 15, 2011)
Hamid Oveisi, Simin Rahighi, Xiangfen Jiang, Yoshiaki Agawa, Ali Beitollahi, Soichi Wakatsuki, and Yusuke Yamauchi
13. Cerium-doped Mesoporous TiO2 Thin Films: Controlled Crystallization of Anatase with Retention of Highly Ordered Mesostructure
Microporous and Mesoporous Materials,2011, 139, 38-44. (October 11, 2010)
Hamid Oveisi, Xiangfen Jiang, Yoshihiro Nemoto, Ali Beitollahi, and Yusuke Yamauchi
14. Mesoporous SiO2 and Nb2O5 Thin Films with Large Spherical Mesopores Through Self-Assembly of Diblock Copolymers: Unusual Conversion to Cuboidal Mesopores by Nb2O5
Crystal Growth
Crystengcomm,2011, 13, 40-43. (September 28, 2010)
Norihiro Suzuki, Masataka Imura, Yoshihiro Nemoto,Xiangfen Jiang, and Yusuke Yamauchi 14 Papers 1. 7KHUPDOO\ 6WDEOH 0HVRSRURXV Ȗ-Alumina Film with Vertical Mesoporosity: Unusual Mesostructual Conversion from Im-3mWR9HUWLFDOO\2ULHQWHGȖ-Alumina Nanowires (Poster Presentation)
JSPS A3 Foresight Seminar: Present Status and Future Prospects of Mesoporous Materials, Tokyo, Japan (September 3, 2010)
Xiangfen Jiang, Hamid Oveisi, and Yusuke Yamauchi
2. 7KHUPDOO\ 6WDEOH 0HVRSRURXV Ȗ-Alumina Film with Vertical Mesoporosity Derived from Pluronic F127-directed Im-3mStructure(Poster Presentation)
The 2ndNIMS-Waseda International Symposium, Tsukuba, Japan (December 1, 2010) Xiangfen Jiang, Hamid Oveisi, Yasuhiro Sakamoto, and Yusuke Yamauchi
No. 3
᪩
᪩✄⏣Ꮫ ༤ኈ㸦ᕤᏛ㸧 Ꮫ⏦ㄳ ◊✲ᴗ⦼᭩
(List of research achievements for application of doctorate (Dr. of Engineering), Waseda University)
✀ 㢮 ู(By Type)
㢟ྡ㸪Ⓨ⾲࣭Ⓨ⾜ᥖ㍕ㄅྡ㸪Ⓨ⾲࣭Ⓨ⾜ᖺ᭶㸪㐃ྡ⪅㸦⏦ㄳ⪅ྵࡴ㸧 (theme, journal name, date & year of publication, name of authors inc. yourself)
(3) Book
3. Solvent Enginnering for Pore Size Control: from Ultra-Large Mesopores to Macropores (Poster Presentation)
The 3rdNIMS(MANA)-Waseda International Symposium, Tokyo, Japan (November 1, 2011) Xiangfen Jiang, Norihiro Suzuki, and Yusuke Yamauchi
4. Controlled Synthesis of Ordered Mesoporous Titania Thin Film with Large-sized Mesopores (Poster Presentation)
The 4thNIMS(MANA)-Waseda International Symposium, Tsukuba, Japan (March 10, 2013) Xiangfen Jiang, Bishnuprasad Bastakoti, Norihiro Suzuki, and Yusuke Yamauchi
4 Presentation 1. Synthesis of Mesoporous Metal Oxides and Metals and Their Applications (Chapter 6)
Nanoporous Materials: Synthesis and Applications, Taylor & Francis Group, Boca Raton (2013) Hongjing Wang,Xiangfen Jiang, and Yusuke Yamauchi
