Impedance Spectrum of QCM Sensor Coated With 18-Crown-6-Ether Solved in THF, Chloroform and Toluene

Abstract

Abstract Crown ether is a form of ethylene oxide cyclo-oligomer. Crown ether has a strong ability to form a complex with cations. The crown ether has been used as part of the electrochemical sensor and optical sensor because of its selectivity to several cations. There was no report on the use of the 18-crown-6-ether as a single coating layer on the QCM sensor. This work investigates the loading effect of the 18-crown-6-ether as a selective coating for QCM sensors as a pre-requirement for a selective coating layer. The impedance spectrum of the QCM sensor coated with 18-crown-6-ether at different concentrations solved in three different solvents was measured. The effects of solvents and 18-crown-6-ether concentrations to the calculated thickness and the effect of the QCM sensor impedance was investigated. The solvents used are Toluene, Tetrahydrofuran (THF), and Chloroform. The results show that the film behaves like a rubber material, which is shown by the impedance value of the sensor at the series resonance frequency. It can be concluded that the thickness of the 18-crown-6-ether layer must be maintained less than one μm to avoid damping on the QCM sensor.