Insights Into the Molecular Recognition Mechanism of 5-Hydroxy-Indol Acetic Acid by Imprinted Xero-Gel Materials

Molecular recognition by molecularly imprinted polymers is based on the interaction of the template molecule and the polymeric matrix, usually through hydrogen bonds and/or hydrophobic interactions. In this work, we used different spectroscopic techniques in order to shed light on the recognition process of 5-hydroxyindolacetic acid (5-HIAA) by a molecularly imprinted silica-based xero-gel. X-ray photoelectron spectroscopy as well as infrared spectroscopy is used to reveal the recognition process. From the data, a double interaction mechanism can be confirmed which involves (a) hydrogen bonds between the surface hydroxyl groups of the imprinted xero-gel and the hydroxyl-moiety of 5-HIAA and (b) π–π stacking interactions among the aromatic residues in the xero-gel provided by the phenyltrimethoxysilane precursor and the indol group of the 5-HIIA.