Comparative Study of a Sensing Platform via Functionalized Calix[4]resorcinarene Ionophores on QCM Resonator as Sensing Materials for Detection of Heavy Metal Ions in Aqueous Environments

Abstract

AbstractA flow type quartz crystal microbalance with impedance analysis capability (QCM‐I) chemical sensor was tested for heavy metal (HM) ions detection in aqueous solutions. The sensor development is based upon the complexing ability of the functionalized AT‐cut quartz resonator gold surface, by calixresorcinarenes, towards the HM ions. These calixresorcinarenes coated QCM sensors were tested for selectively adsorbing HM ions, such as copper, lead, mercury, and cadmium, from solution over a wide range of concentration (5‐1000 ppm) through complexation with functional groups in the coating layers. QCM‐Calix based chemosensors, C‐dec‐9‐en‐1‐ylcalix[4]resorcinarene (ionophore I), C‐undecylcalix[4]resorcinarene (ionophore II), C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(S‐)‐α‐methylbenzylamine (ionophore III) and C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(R+)‐α‐methylbenzylamine (ionophore IV), were synthesized and immobilized to detect HM ions of Pb2+, Cd2+, Hg2+, and Cu2+ in aqueous solutions. Using the impedance analysis, which facilitates a complete description of the acoustic loading of the crystal surface, the full width at half maximum of the QCM resonance peak (FWHM) values are obtained from the impedance spectra. FWHM variations revealed the effectiveness of the proposed ionophores in detecting HM at different levels. Sensitivities and wide linear relationships between HM concentration and FWHM were interpreted. Detection limits of (0.32, 0.57, 0.37, 0.89 ppm) and (1.63, 0.18, 0.76, 0.2 ppm) were determined for ionophore I and II, for Cd2+, Cu2+, Hg2+ and Pb2+ ions, respectively. Ionophore (I) showed binding preferences towards Cd2+ ions where ionophore (II) produced similar selectivity toward Cu2+ and Pb2+ ions. Ionophores III and IV were used for the assessment of ▵FWHM values to comprehend the detection affinities of the ionophores toward HM ions.