Optical Recognition of n-Butylammonium and 1,5-Pentanediammonium Picrates by a Calix[5]arene Monolayer Covalently Assembled on Silica Substrates

High quality silica substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer. To these, a calix[5]arene bearing a 12-aminododecyl moiety at the lower rim was then covalently bonded, producing a new calix[5]arene-based monolayer on silica substrates. The surface chemical characterization of these hybrid materials was carried out by X-ray photoelectron spectroscopy. The optical sensing properties of this monolayer were studied at room temperature by UV-vis measurements. The system is shown to have recognition properties for n-butylammonium ions at parts per million levels and for a biologically relevant analyte such as 1,5-pentanediammonium ion (cadaverine32Hþ). The adopted synthetic procedure has proven to be effective in transferring molecular properties to a solid state device.