Field-effect transistor based sensors for heavy metal ion detection in water systems

Real-time monitoring of heavy metal ions (HMIs) in water systems is regarded as a critical task in environmental analysis, given the acute and chronic threats these ions pose to public health. As an emerging platform, field-effect transistor (FET) based sensors are recognized for their combination of high sensitivity, real-time response, miniaturization, and cost-effectiveness. This review systematically examines recent advances in FET-based HMI sensors, with emphasis placed on working mechanisms, channel materials, surface functionalization, and integration with artificial intelligence (AI) and the Internet of Things (IoT). The working mechanisms of FET-based HMI sensors are categorized for the first time into three distinct types, based on the mode of ion FET interaction. Subsequently, the development of channel materials is reviewed, with performance characteristics and emerging trends highlighted, while current challenges in surface functionalization are also addressed. Selectivity issues are further explored, with efforts focused on AI/IoT-assisted sensor arrays discussed as a promising solution. Finally, future challenges and potential strategies are outlined to advance FET-based HMI sensors from fundamental research toward practical application.