Separation and concentration of specific target compounds are one of the most important issues for environmental remediation and usage of natural resources especially rare elements and compounds. Accordingly, various nanospace materials have been synthesized in our laboratory to find useful phenomena. By using layered silicates, ions and molecules can be concentrated from aqueous and vapor phases. The large surface area and tunable surface properties derived from the layered structures contribute to molecular recognition. The choice of materials and modification of the nanostructure were carefully investigated to optimize the performance based on molecular recognition (selective adsorption, substrate selective reaction, detection, etc.). The progress made in materials syntheses (variation of layered materials, sophisticated modification, controlled morphology, and processing) has made the design of materials more attractive and realistic.
Molecular Recognition of Layered Silicates
The molecular recognition phenomenon, which occurs in the interlayer space of layered solids by highlighting how the structural design is correlated to performance. Molecular recognition herein is not limited to specific binding to a particular molecular species and other functional materials designs, in which molecular interactions on layered silicate play a role.
Schematic drawing of our materials design concept for molecular recognition.
Our research team at VISTEC has been studying on molecular recognition by designing nanostructures. The procedures include surface modification and hierarchical design for absorption and reaction selectivity. Here, the examples using layered silicate are introduced.
Selectivity of Ion Exchange
Layered silicate is a group of layered clay minerals consisting of negatively charged silicate layers and readily exchangeable interlayer cations which is cation exchangers. For example, magadiite selectively and effectively adsorbed Zn2+ from sea water.
Selective Adsorption of Molecule
It has been recognized that various layered silicates adsorb polar molecules and cations. The surface properties of layered silicates have been modified toward selective and effective concentration of target molecules.
Catalytic reactions often require selectivity, therefore, the application of solids with well-defined nanospace as heterogeneous catalysts has been investigated.
The detection of certain kinds of molecules is an important subject from viewpoints such as environmental monitoring. The separation of target molecules from competitors is one of the most important factors for this purpose. Therefore, detection requires molecular recognition. For example, the appearance of the luminescence of Eu3+ intercalated in montmorillonite by the adsorption of 4-nonylphenol.
External Stimuli-Responsive Change in the Arrangement of Interlayer Ions
Stimuli-responsive properties have been investigated for the creation of smart materials. Through the modification of layered solids with stimuli-responsive functional groups, changes in the molecular-recognition ability of layered solids have been examined. Photoresponsive adsorbents for phenol through the introduction of a cationic azo dye into the interlayer space of layered silicates was designed as an example.
Schematic drawing of the photoinduced intercalation /deintercalation of phenol in azo dye modified montmorillonite.
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Dr. Makoto Ogawa (Professor)
Dr. Sareeya Bureekaew (Lecturer)
Dr. Surakerk Onsuratoom (Postdoctoral Research Fellow)
Dr. Tetsuo Yamaguchi (Postdoctoral Research Fellow)
Dr. Hojoon Shin (Postdoctoral Research Fellow)
Dr. Sebastian Bosch (Postdoctoral Research Fellow)
Ms. Thipwipa Sirinakorn
Mr. Kasimanat Vibulyaseak
Mr. Natthawut Homhuan
Ms. Kamonnart Imwiset
Ms. Aranee Teepakakorn
Mr. Wichayut Reanthonglert
Ms. Soontaree Intasa-ard