Xiangfen Jiang

Unusual antibacterial property of mesoporous titania films: drastic improvement by controlling surface area and crystallinity.

One of the most urgent requirements of human life in the 21 century is development of new antibacterial materials and sterilization technologies that can improve human health. Until now, the most commonly used antibacterial agents are based on chlorine, chlorine dioxide, and organic biocide compounds. These agents are extremely toxic for humans and their residues are also not environmentally friendly. Therefore, it is very important to develop antibacterial biocompatible materials. Titanium dioxide (titania, TiO2) materials in the anatase form have attracted great interest as a new antibacterial material. Titania can work well under ultraviolet (UV) light owing to its photo-semiconductor properties. Currently, this property has been widely utilized for various applications such as water treatment, air and environmental purification, hazardous waste remediation, and deactivation of bacteria. Commercial products with titania (e.g., self-cleaning glasses and anti-fogging coatings) are well known all over the world. To date, various titania-based nanostructures including nanorods and nanoparticles have been reported. To further enhance the photocatalytic performance, many efforts have been made for doping various metal/semiconductor elements into titania materials. In this system, the electrons accumulated on the metal and holes remained on the photocatalyst surface. Therefore, a significant reduction in the recombination rate is realized owing to better charge separation between the electrons and holes. Therefore, the titania-based composites with metal/semiconductor elements can enhance the overall photocatalytic efficiency and the damage of microorganisms of the cell. In this Communication, we focused on a further simple and low-cost synthetic method and synthesized mesoporous titania films by utilizing bottom-up nanotechnology with surfactant assembly. Mesoporous materials with extremely high surface area should be good candidates for the next generation of antibacterial materials. Compared with the traditional titania materials mentioned above, the high surface area originated from mesoporous networks can provide a higher amount of hydroxyl radicals (·OH) which can increase the photoactivity. In the past few years, special attention has been paid to the synthesis of mesoporous titania powders as effective photocatalysts including an antibacterial application. However, the mesoporous titania in the powder form has some disadvantages. The powders which are not fixed on substrates are washed out easily by external treatments and then the released particles themselves may pollute the environment. Also, nanosized powders generally cause serious problems to human health. Therefore, the mesoporous titania films reported here are more applicable [a] H. Oveisi, X. Jiang, Dr. Y. Nemoto, Prof. Dr. Y. Yamauchi World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS) 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 (Japan) Fax: (+81)29-860-4706 E-mail : Yamauchi.Yusuke@nims.go.jp [b] Dr. S. Rahighi, Prof. Dr. S. Wakatsuki Structural Biology Research Center High Energy Accelerator Research Organization (KEK) 1-1 Oho, Tsukuba, Ibaraki, 305-0801 (Japan) [c] H. Oveisi, Prof. Dr. A. Beitollahi Center of Excellence in Advanced Materials and Processing Department of Metallurgy and Materials Engineering Iran University of Science and Technology (IUST) Narmak, Tehran 16844 (Iran) [d] X. Jiang, Prof. Dr. Y. Yamauchi Faculty of Science and Engineering Waseda University 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan) [e] Prof. Dr. Y. Yamauchi Precursory Research for Embryonic Science and Technology (PRESTO) Japan Science and Technology Agency (JST) 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan). [] These authors contributed equally to this work. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000351.

New trend on mesoporous films: precise controls of one-dimensional (1D) mesochannels toward innovative applications

Mesoporous films with uniaxially oriented one-dimensional (1D) mesochannels have attracted much interest in a wide range of applications. In this highlight article, we briefly review the recent advances in this emerging field. Some general aspects including alignment methods, formation mechanisms, characterizations, and future challenges are introduced and discussed.

Synthesis of Continuous Mesoporous Alumina Films with Large-Sized Cage-Type Mesopores by Using Diblock Copolymers

Mesoporous alumina films with large-sized cage-type mesopores were prepared by using commercially available diblock copolymer (PS-b-PEO) and economic inorganic salt (AlCl(3)) as aluminum source. The obtained mesopore sizes drastically expand from 35u2005nm to 80u2005nm when the amount of ethanol in the precursor solutions were controlled. More interestingly, under an optimized amount of ethanol as co-solvent, there was no significant change of micelle morphology on the substrate, even though the relative amount of PS-b-PEO to alumina source was dramatically varied. When the amount of alumina precursor was decreased, the pore walls gradually became thinner, thereby improving pore connectivity. The ordered mesoporous alumina films obtained in this study exhibit high thermal stability up to 1000u2009°C, and their frameworks are successfully crystallized to γ-alumina phase. This technique could also be applicable for creating other metal oxide thin films with large mesopores.

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

Mesoporous silica and niobia thin films are fabricated by using precursor solutions including PS-b-PEO diblock copolymers. The mesopore arrangements are strongly affected by dip-coating speeds during the film formation. With the decrease of the coating speeds, the mesopores were more closely packed each other.

Preparation of Ordered Mesoporous Alumina‐Doped Titania Films with High Thermal Stability and Their Application to High‐Speed Passive‐Matrix Electrochromic Displays

Ordered mesoporous alumina-doped titania thin films with anatase crystalline structure were prepared by using triblock copolymer Pluronic P123 as structure-directing agent. Uniform Al doping was realized by using aluminum isopropoxide as a dopant source which can be hydrolyzed together with titanium tetraisopropoxide. Aluminum doping into the titania framework can prevent rapid crystallization to the anatase phase, thereby drastically increasing thermal stability. With increasing Al content, the crystallization temperatures tend to increase gradually. Even when the Al content doped into the framework was increased to 15 mol %, a well-ordered mesoporous structure was obtained, and the mesostructural ordering was still maintained after calcination at 550 °C. During the calcination process, large uniaxial shrinkage occurred along the direction perpendicular to the substrate with retention of the horizontal mesoscale periodicity, whereby vertically oriented nanopillars were formed in the film. The resulting vertical porosity was successfully exploited to fabricate a high-speed and high-quality passive-matrix electrochromic display by using a leuco dye. The vertical nanospace in the films can effectively prevent drifting of the leuco dye.