A Novel Thiol-Functionalized Graphene Oxide-Based Quartz Crystal Microbalance Sensor for Cadmium Ion Detection

Since heavy metals are not biodegradable and bioaccumulative, the increasing levels of cadmium (Cd²⁺) and other heavy metal contamination of water supplies seriously threaten the environment and public health. Although conventional detection methods are sensitive, they are often costly, time-consuming, and unsuitable for on-site applications. We report on the development of a new, affordable, and extremely sensitive quartz crystal microbalance (QCM) sensor for the detection of cadmium ions that is based on 3-mercaptopropyltrimethoxysilane-functionalized graphene oxide (3-MPTMS-GO). Hummer’s modified method created graphene oxide (GO), which was then functionalized with 3-MPTMS through salinization. Using TEM, Raman spectroscopy, FT-IR, UV-Vis spectroscopy, AFM, contact angle measurements, and Zeta potential analysis, structural and surface characterizations were carried out to verify successful functionalization and improved surface characteristics. Excellent sensitivity towards Cd2+ ions was shown by the QCM sensor coated with 3-MPTMS-GO at different pH levels 3, 7, and 11. The optimal sensor performance was observed at neutral pH. through calibration study, the sensor exhibited linear detection range from 0.05 ppm to 0.1 ppm (R2 = 0.930) with a limit of detection (LOD) of 0.003 ppm which aligns with WHO standards. Moreover, the sensor demonstrated excellent regeneration capability over 10 reuse cycles using EDTA treatment. This initial study demonstrates the promising potential of the 3-MPTMS-GO-based QCM sensor as a proof-of-concept platform for cadmium detection in controlled laboratory conditions, requiring comprehensive validation before practical environmental monitoring applications.