Comparison of sensing characteristics of ChemFEC devices based on spin-coated thin films of calix[ n]arenes

Abstract

ChemFECs (chemical field effect capacitors) or EIS (Electrolyte-Insulator-Semiconductor) devices were coated with calix[ n]arene macrocycles for cation sensors development. Silicon nitride surface electrodes were spin-coated with p-tert-butylcalix[ n]arene molecules for n = 8, 9 and 11. Electrochemical capacitance measurements were carried out to evaluate the sensitivity of the calix[ n]arene layers towards specific cations as calcium and copper ions. Sensor responses were due to the “host-guest” specific interaction between the rigid cavity of calix[ n]arene receptors (ligand) and chemical ion species. The developed chemical sensors have demonstrated good analytical characteristic in terms of: stability, selectivity and lifetime. In addition, experimental results were fitted using the site binding model in order to determine complex association constants, pK (1.9 ≤ pK ≤ 6.39) and surface density of ligands, N L (9.10 14 ≤ N L ≤ 2.10 16). All results obtained in this work were compared with those obtained using silicon dioxide EIS electrodes coated with the same calix[ n]arene receptors using both spin-coating and thermal evaporation deposit processes.