On the other hand, chemical sensors and biosensor systems that utilize field-effect transistor (FET) technology have shown great promise in detecting heavy metal ions in various environments with advancement in nanomaterials and nanostructures. The FET sensor systems consist of several functional blocks that work together to detect and measure analyte-specific signals. The two critical components of these systems are the recognition element and the transducer. The recognition element is responsible for binding the probes-target, generating a signal that corresponds to the presence of the heavy metal ions and its abundance. Common recognition elements include antibodies, single-stranded DNA, and ion-sensing membranes. In bio-/chem-sensors, the recognition element is often immobilized on a solid surface layer on the transducer. The transducer, on the other hand, converts the quantitative or semi-quantitative information about the target into a measurable signal. This signal can be a current, potential, or temperature change. Popular nanosensor transducers used in FET/chemiresistive sensor development include graphene, carbon nanotubes, and silicon. Researchers have explored the potential of several semiconductor materials as transducers in FET/chemiresistive sensor development. These transducers have been used in various transducer platforms to develop chemical or biosensors for heavy metal ions monitoring. A wide range of recognition elements has been explored to realize the detection of heavy metal ions. The use of FET sensor technology in heavy metal ions detection has numerous advantages, including high sensitivity, low cost, and real-time monitoring capabilities. The use of nanosensors as transducers has also improved the sensitivity and selectivity of these sensor systems. However, the performance of these sensors is affected by several factors, including the stability of the recognition element, the sensitivity of the transducer, and the specificity of the sensing interface. These factors must be carefully considered to ensure the accurate detection and measurement of heavy metal ions in various environments.