Fluorescence of pyrene intramolecular excimers in Langmuir-Blodgett films

DiPyMe in SDS Micelles: Artifacts and Their Implications in the Interpretation of Micellar Properties

“…Di­(1-pyrenylmethyl) ether, also referred to as DiPyMe, belongs to the large family of bipyrenyl compounds that are composed of two pyrene moieties separated by a linear chain and which have been studied in great detail over the last four decades. − The photophysical properties of dipyrenyl alkanes first introduced in 1976 by Zachariasse have been carefully characterized in the 1980s and 1990s, particularly the effect that the spacer length between the two pyrene groups had on their ability to form an excimer. − ,, The salient features of these studies were that, for linkers long enough to avoid specific unfavorable conformations that in some cases prevented excimer formation all together, the efficiency of pyrene excimer formation decreased with increasing linker length and that up to two types of excimer species could be detected. Among bipyrenyl molecules, DiPyMe with a dimethyl ether linkage ,− and di­(1-pyrenyl)­propane (DiPyPr) with a propylene linker ,− have been the most studied probably because their short three-atom-long spacer endowed them with the smallest molecular dimension of all bipyrenyl compounds and excimer formation between an excited and ground-state pyrene took place diffusionally and very efficiently due to the short linker holding the pyrene groups in close proximity. Consequently, DiPyMe and DiPyPr were small enough to fit inside any hydrophobic microdomain generated by molecular or polymeric surfactants in aqueous solution while the diffusion-controlled process of pyrene excimer formation provided information about the local viscosity also referred to as the microviscosity of the medium in which DiPyMe and DiPyPr were embedded.…”

“…On the basis of all these interesting features, it is thus hardly surprising that DiPyMe has been employed to probe a wide range of heterogeneous media in aqueous solutions. In particular, lipid membranes, ,, polymeric micelles, ,,,,, and polymer matrices have all been investigated with DiPyMe. Considering such a sustained interest over a time period spanning more than three decades, it is thus somewhat surprising that the hydrolysis of DiPyMe in aqueous solutions has never been reported.…”

“…membranes, 1,11,14 polymeric micelles, 12,13,15,16,18,20 and polymer matrices 19 have all been investigated with DiPyMe. Considering such a sustained interest over a time period spanning more than three decades, it is thus somewhat surprising that the hydrolysis of DiPyMe in aqueous solutions has never been reported.…”

Influence of Pyrene-Based Fluorescent Probes on the Characteristics of DMPA/DMPC Langmuir−Blodgett Films

“…Two different types of pyrene-labeled phospholipids were used: one bearing the pyrene moiety at the end of one or two aliphatic chains ,, and the other with the fluorophore linked to the polar head group . To our knowledge, a few studies have been performed with fluorophores in LB films; some were conducted to determine lateral diffusion at the solid−liquid interface, and some others were performed to determine either the kinetics of pyrene fluorescence , or the formation of intramolecular excimers …”

“…10 To our knowledge, a few studies have been performed with fluorophores in LB films; some were conducted to determine lateral diffusion at the solid-liquid interface, 11 and some others were performed to determine either the kinetics of pyrene fluorescence 12,13 or the formation of intramolecular excimers. 14 In our case, two fluorescent probes were chosen, pyrene and 1-palmitoyl-2-pyrenyldecanoylphosphatidylcholine (PyC 10 PPC). The influence of these fluorescent probes on the behavior of the lipidic monolayer was controlled through the shape of surface pressure-molecular area isotherms, which was directly related to the concentration of the probe.…”