Detection of Chemical Host–Guest Interactions Using a Quartz Tuning Fork Sensing System

In this paper, we investigate the potential of using quartz tuning fork (QTF) sensing system for detection of specific metal ions in aqueous solutions with sample volume of $1~\mu \text{L}$ . Functionalized self-assembled monolayers (SAMs) of L-glutathione (LG) on gold-coated QTFs were used to sense specific analytes of CaCl₂ and HgCl₂, whereas functionalized L-cysteine based SAMs used to sense PbCl₂. The resonance frequency undergoes a shift in response to the interaction between functionalized QTF and target analyte. X-ray photoelectron spectroscopy was used to study the interaction of thiol groups between the functionalized SAM and gold coated on QTF surface. Our analysis revealed that active QTFs functionalized with LG are more sensitive to detection of CaCl₂ compared with HgCl₂. The SAM-based QTF sensors were found to be capable of detecting low concentrations ( $10^{- {12}}$ M) of divalent analyte solutes with high sensitivity.