Immobilization inside Langmuir−Blodgett Films of a Fluorescent Artificial Receptor for Zn(II) Recognition

Abstract

This work is focused on the study of the immobilization of a synthetic fluorescent macrocycloureide in a nanostructure obtained through Langmuir−Blodgett (LB) technique. Its interfacial behavior shows that it can take various orientations at the air/water interface. Mixed with behenic acid it is successfully transferred in Y-type onto hydrophobic substrates. The related LB films were controlled through Fourier transform IR spectroscopy and Nomarski microscopy. Fluorescence emission spectra were recorded in air, water, and phosphate buffer at pH 12. Three signals were emitted, corresponding to three different forms of the immobilized macrocycloureide: monomer, dimer, and molecule stacks. Micromolar concentrations of zinc could be detected through signal fluorescence enhancement of the dimer emission, giving evidence that the immobilized macrocycloureide keeps its fluorescence properties and its ability for molecular recognition of Zn(II) ions.

Atypical Behavior of a New Dialkyl Macrocycloureide in Langmuir−Blodgett Film Formation

“…20 Moreover, the presence of the macrocycloureide moiety was revealed by the specific bands previously described. 4…”

“…In a previous work, the immobilization of this macrocycloureide in a nanostructure was obtained through the Langmuir−Blodgett technique, and as the macrocycloureide alone cannot be transferred onto the substrate, it was compulsory to use a host molecule such as docosanoic acid to buildup Langmuir−Blodgett (LB) films. The immobilized macrocycloureide keeps its fluorescent properties and gives a recognition signal in a presence of zinc at micromolar concentrations …”

“…The immobilized macrocycloureide keeps its fluorescent properties and gives a recognition signal in a presence of zinc at micromolar concentrations. 4 Nevertheless, the fluorescence intensity was low owing to the weak macrocycloureide/host ratio. To avoid the presence of host molecules, two saturated alkyl chains with 18 atoms of carbon has been covalently linked to the original macrocycloureide according to a procedure described elsewhere.…”