Solvent Effect on Mobility and Photostability of Organic Dyes Embedded inside Silica Sol-Gel 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：2005
- 出版时间：December 27, 2005
- 年：2005
- 卷：17
- 期：26
- 页码：6702 - 6712
- 全文大小：520K
- 年卷期：v.17,no.26(December 27, 2005)
- ISSN：1520-5002
文摘
Polarization resolved fluorescence from single molecules was measured from rhodamine 6G (R6G),sulforhodamine B (SRB), Oregon Green 514 (ORG), and didodecyl-3,3,3',3'-tetramethylindocarbocyanine(DilC12) embedded in silica sol-gel thin films in contact with water and ethanol. Positively chargedR6G was found to be firmly immobilized, regardless of the solvent medium. Despite its net negativecharge, zwitterionic SRB was found mostly immobilized in both solvent media. The immobilization ofSRB was attributed to a delicate balance of Coulombic interaction, hydrogen bonding, and molecularimprinting effect. While R6G showed a significant decrease in photostability in a solvent medium becauseof enhanced solvent interactions, hydrogen bonding appeared to effectively retard the molecular motionsof solvated SRB such that its photostability exceeded those in dry films. The mobility of negativelycharged ORG was found to be moderately enhanced through repulsion, but Coulombic force was not asinfluential as hydrophobic interaction, which was responsible for the high mobility found for DiIC12 indry films. When in water and ethanol, the hydrophobic chains of DiIC12 were pushed by the solventtoward the less polar silica matrix, forcing DiIC12 to the solid-liquid interface and transforming asubstantial amount of tumbling DiIC12 into intermediate DiIC12. Since the photostability of DiIC12 isclosely related to the dynamics associated with its hydrophobic chains, DiIC12 in both water-covered andethanol-covered films displayed comparable photostability because of the similar silica environmentsurrounding the hydrophobic chains.