Effect of Coulombic Interactions on Rotational Mobility of Guests in Sol-Gel Silicate Thin Films

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• 作者：James W. Gilliland ; Kazushige Yokoyama ; and Wai Tak Yip
• 刊名：Chemistry of Materials
• 出版年：2004
• 出版时间：October 5, 2004
• 年：2004
• 卷：16
• 期：20
• 页码：3949 - 3954
• 全文大小：120K
• 年卷期：v.16,no.20(October 5, 2004)
• ISSN：1520-5002

文摘

We investigate the effect of Coulombic interactions on the mobility of rhodamine 6G (R6G)and Oregon Green 514 (ORG) in sol-gel silicates by measuring their mobility distributionsusing single molecule polarization measurements. While R6G is a cationic dye, ORG (pK_a =3.69 ± 0.08) is an anionic dye at neutral pH. The presence of more tumbling ORG moleculesin sol-gel silicates indicates that R6G and ORG experience opposite Coulombic interactionswith a predominately anionic silica sol-gel surface. On the other hand, the fact that tumblingORG only represents a minor portion of ORG investigated, even at pH 7, clearly illustratesthat Coulombic interaction alone does not control the mobility of an encapsulated guestmolecule in sol-gel silicates.