Synthesis and Characterization of the Amphoteric Amino Acid Bifunctional Mesoporous Silica

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• 作者：Lu Han ; Juanfang Ruan ; Yongsheng Li ; Osamu Terasaki ; Shunai Che
• 刊名：Chemistry of Materials
• 出版年：2007
• 出版时间：May 29, 2007
• 年：2007
• 卷：19
• 期：11
• 页码：2860 - 2867
• 全文大小：485K
• 年卷期：v.19,no.11(May 29, 2007)
• ISSN：1520-5002

文摘

New amphoteric, amino acid bifunctional mesoporous silicas with highly ordered mesopores weresynthesized via the cooperative self-assembly of surfactants, co-structure-directing agents (CSDA), anda silica source. Uniform distributions of acid and base organic groups on the mesopore surfaces wereformed by interactions between the counter charged surfactant head groups and ionic parts of CSDAs,that is, between the cationic and anionic surfactant head groups and the carboxyl and amino groups ofCSDAs, respectively. For structural determination, the materials were characterized using X-ray diffraction(XRD), high-resolution transmission electron microscopy (HRTEM), and N₂ sorption measurements. Ithas been demonstrated that organic (NH₂ and COOH) pairs incorporated in the mesopore walls behaveas amino acids, collectively exhibiting an isoelectric point, pI, of ~6.0, a value close to that of a neutralamino acid. Further, the amphoteric amino acid moiety can be switched readily in a moment from netcationic and acidic to net anionic and basic by simply increasing the pH of the solution. Loading of theNH₂ and COOH groups was controlled at an almost equal basis of ca. 1.0 and 0.9 mmol/g SiO₂,respectively. Close adjacency of organic NH₂ and COOH groups was confirmed by the formation ofamide moieties. The basic idea employed here will be easily and widely applicable to the design ofrelevant mesoporous materials.