UV-Induced Reaction Kinetics of Dilinoleoylphosphatidylethanolamine Monolayers

Abstract

The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure.

Characterizing Ultrathin and Thick Organic Layers by Surface Plasmon Resonance Three-Wavelength and Waveguide Mode Analysis

“…Parts A and B of Figure S3 (Supporting Information, section SIII) show the compression isotherms of SA and HSPC measured on pure water and UAc-containing subphases. UAc was chosen as the subphase counterion as it has been shown to enable the deposition of more than one monolayer of phospholipids on a solid substrate. , The compression isotherms reveal that the UAc expands the liquid state of both the SA and HSPC monolayers compared with the monolayers measured on a pure water subphase. This is an effect opposite what is usually encountered with multivalent counterions, such as Mn 2+ , Cd 2+ , and Tb 3+ .…”

STM Study of trans-Stilbene Self-Organized on the Ag/Ge(111)-(√3 × √3)R30° Surface

“…4 However, relatively little work has been performed on the photoisomerizationinduced structural change on surfaces. 5 In this work, we study the surface structure of TSB adsorbed on Ag/Ge-(111)-( 3 × 3)R30°. The main focus is to investigate how the interactions between adsorbed molecules and between surface adsorbates and substrate influence the surface structure.…”

“…Photoisomerization of stilbene in solution has been well studied and reviewed by Waldeck . However, relatively little work has been performed on the photoisomerization-induced structural change on surfaces . In this work, we study the surface structure of TSB adsorbed on Ag/Ge(111)-( × ) R 30°.…”

Structural transitions of lipid monolayers on metallic nanoparticles

“…Therefore, they are also expected to reflect any kind of structural transition which affects the liquid crystalline domain. In the following, changes of the lipid structure are facilitated by annealing at different levels of humidity and by UV-induced polymerization of the unsaturated aliphatic chains [8,9]. The resulting consequences on the particle arrangement and the inter-particle distances are observed experimentally and interpreted using a structural model of the given heterogeneous system.…”

“…This fact may explain the observation that a high level of humidity is necessary to induce the interdigitation process. UV irradiation is known to start a chain reaction leading to the polymerization of the unsaturated hydrocarbon chains of phospholipids [8,9]. The particle arrangement, in contrast, does not change significantly after UV treatment.…”