Selective detection of calcium cations on macromolecular Langmuir monolayer and Langmuir-Schaefer films

In this study, we report the interfacial Langmuir monolayer behavior and surface morphological features of a dendronic terthiophene linked via a tetraethylene glycol moiety (3T5O3T) and its complexation with calcium cations. Surface pressure-mean molecular area (pi-A) isotherms show distinct behavior due to the secondary interaction of cations with the ionophore units. Furthermore, two Langmuir-Schaefer (LS) films with and without calcium cations exhibited significantly different surface morphological features from atomic force microscopy (AFM) imaging. Quartz crystal microbalance (QCM) measurements reveal changes in frequency and resistance enabling selective sensing of calcium cations on the LS films. Thus, well-organized 3T5O3T LS films on the solid substrates are potential candidates for highly selective chemosensing.