Reflection–absorption IR and surface-enhanced IR spectroscopy of tetracarboethoxy t-butyl-calix[4]arene, as a host molecule with potential applications in sensor devices

A vibrational study of the calix[4]arene derivative 25,26,27,28-tetracarboethoxy-p-tert-butylcalix[4]arene (TCEC) is accomplished in this work. This characterization implies a study of its adsorption on metal (Cu and Ag) films by reflection–absorption IR spectroscopy (RAIRS) and surface-enhanced IR (SEIR) in transmission and reflection–absorption configurations. Metal surfaces for SEIR were obtained by a simple direct immobilization on Ge of Ag nanoparticles suspended in water. The goal of this research was an accurate vibrational characterization of the above calixarene molecule, paying special attention in the structural marker bands of ester groups, which play an important role in the molecular adsorption on such metals. The information derived from this study will serve to better understand the interaction of ester-functionalised calixarenes with these metals, in order to prepare sensor films with selective affinity towards polycyclic aromatic hydrocarbons (PAHs). The application of these surface techniques confirmed the importance of the ester groups in the immobilization and self-assembly of these host molecules to the metal surface and provided information about the orientation adopted by TCEC on the metal.