From Two-Dimensional to Three-Dimensional at the Air/Water Interface: The Self-Aggregation of the Acridine Dye in Mixed Monolayers

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• 作者：Carlos Rubia-Pay谩 ; Eugenio Jimenez-Mill谩n ; Juan J. Giner-Casares ; Gerald Brezesinski ; Mar铆a T. Mart铆n-Romero ; Luis Camacho
• 刊名：Langmuir
• 出版年：2013
• 出版时间：April 16, 2013
• 年：2013
• 卷：29
• 期：15
• 页码：4796-4805
• 全文大小：506K
• 年卷期：v.29,no.15(April 16, 2013)
• ISSN：1520-5827

文摘

The formation of well-defined supramolecular structures on the nanoscopic scale is a fundamental step in nanotechnology. The fine control of the layer-by-layer growth of the supramolecular assemblies at interfaces is most desirable. The collapse of a mixed monolayer composed of two surfactants in an equimolar ratio (the organic dye N-10-dodecyl acridine (DAO) and stearic acid (SA)) is analyzed herein. The collapse process of the DAO/SA mixed monolayer has been monitored using surface pressure鈥搈olecular area (蟺鈥揂) and surface potential isotherms, UV鈥搗isible reflection spectroscopy, polarization-modulated infrared reflection鈥揳bsorption spectroscopy (PM-IRRAS), Brewster angle microscopy (BAM), and synchrotron-based in situ X-ray reflectivity (XRR) measurements. The collapse of the DAO/SA mixed monolayer leads to an ordered trilayer. The growth of anisotropic 2D domains of micrometric size is observed during the formation of the trilayer, related to the ordering of the acridine polar headgroups. The trilayer is organized with the first and third monolayers displaying the polar headgroups pointing to the aqueous subphase, whereas the intermediate layer displays the polar headgroups pointing to the air. The trilayer is stabilized by the strong self-aggregation acridine dye group of the DAO molecule. The controlled transition from a monolayer to a trilayer described herein is proposed as a model for further interfacial supramolecular structures of tunable thickness comprising organic dyes.