Study of the membrane morphology and investigation of sensitivity to ions for sensors based on calixarenes

Abstract

Many investigations on dielectric, electronic and spectroscopic characterisation have been achieved on molecular materials for their eventual application as sensors or electronic devices. Calixarenes exhibit an interesting supramolecular structure on account of their receptor properties; they represent receptor molecules of widely varying size for metal cations and organic molecules. They are comparatively new cyclic condensation products of para-substituted phenols and formaldehyde; they form a series of well-defined cyclic oligomers. Therefore, the variation of cavity size according to the requirements (i.e. ion sensitivities) of different guests is possible. The macro cycles are characterised by the phenolic unit number (4,6,8,…). p-tert-Butyl calix[ n]arene ( n = 4 and 8), used as a sensitive membrane incorporating the receptor molecule on the top of the gate oxide, was characterised. The calixarene was thermally evaporated on the oxide to form a semiconductor-oxide-film capacitance structure. It is shown, by means of structural and spectroscopic studies, that films have good adherence to the oxide and are chemically very stable allowing the use of such a structure as a chemical sensor in liquid media. The studies of ISFET structure using calix[ n]arene membranes are in progress, showing an interesting selectivity and stability.