Preorganization of Langmuir Monolayers of Crown-Substituted 1,8-Naphthalimide to Enhance the Efficiency of Silver Ion Binding at Interfaces

This work is devoted to studying the possibility of using a previously developed method of cation-induced preorganization of Langmuir monolayers of crown-containing chromoionophores by barium cations located in the subphase to enhance the sensor response of thin-film sensitive elements based on the amphiphilic crown derivative of 1,8-naphthalimide (NICr). The direct evidence that barium cations remain inert towards the NICr monolayer while analyte cations localize in the monolayer in close proximity to the sulfur atoms of the ionophore groups was provided by XSW method. The effect of such preorganization on the efficiency of silver-ion binding by NICr monolayers at interfaces was studied. Fluorescence spectra of monolayers and Langmuir–Blodgett films obtained from them were used as a response signal to the sensor-analyte interaction. It is important to note that in the presence of Ag⁺ the fluorescence intensity of the studied planar systems increases, which is most convenient for registration (“switch-on” sensors). It was demonstrated that monolayer preorganization leads to an increase in the response signal to silver ion binding by 2–2.5 times. This confirms the universality of proposed approach and allows us to plan further studies of system under consideration to optimize its characteristics