A Novel and Cost-Effective 1-Octadecanethiol SAMs-on-Au Based QCM Sensor for Detecting ClO2 Residues in Bleaching Wastewater

A novel and cost-effective 1-octadecanethiol self-assembled monolayers (SAMs)-on-Au-based quartz crystal microbalance (QCM) sensor is proposed in this study for detecting chlorine dioxide (ClO2) residues in bleaching wastewater. 1-octadecanethiol SAMs were coated on the Au electrode of QCM chip by Au-sulfur bond effect to form ClO2 sensing films. Both theoretical and experimental results show that substances with different oxidizing abilities have varying levels of corrosive effects on the 1-octadecanethiol SAMs-on-Au, resulting in different mass load changes on the Au electrode of the QCM chip. These changes, in turn, lead to resonant frequency shifts of the QCM chip. The prepared sensitive films were further analyzed by scanning electron microscope (SEM), X-ray energy dispersive spectroscopy (EDS), atomic force microscope (AFM), and contact angles. Real-time experiments were conducted for the measurement of ClO2 residues, and the functional relationship between the output signals and ClO2 concentrations was established. The sensor exhibits a resolution of 0.03 mg/L and demonstrates excellent selectivity, long-term stability, and reusability in the measurement range of ClO2 concentrations from 0.3 to 0.8 mg/L, making it a potential device for early warning of excessive ClO2 residues in bleaching wastewater cost-effectively.