A Portable and Reusable Sensor System Based on Graphene for Real-Time and Sensitive Detection of Lead Ions in Water

Long-term exposure to Pb2+ can cause irreversible damage to the nervous, cardiovascular, and reproductive systems. Therefore, developing a fast and sensitive detection system capable of monitoring minuscule concentrations of Pb2+ is essential. In this study, we have demonstrated a fully portable sensor system enabling rapid, sensitive, and real-time monitoring of Pb2+. The sensor system adopts the remote-gate field-effect transistor (RGFET) detection scheme and is easy to operate, even for non-experts. The sensor system comprises two printed circuit boards (PCBs): a sensor PCB with a remote gate electrode and an analyzer PCB with a metal–oxide–semiconductor field-effect transistor (MOSFET) transducer and peripheral electronics to manage sensor signals. To achieve a high sensitivity for Pb2+, we utilized a graphene ink drop-casted on the sensor PCB as a sensing membrane. The graphene film is straightforward to deposit and remove, enabling the sensor PCB to be reused multiple times. The sensor system is further linked to a smartphone app that instantly monitors the sensor response, allowing for rapid point-of-use detection. The sensor has a high sensitivity of 21.7% when the limit of detection (LOD) value of 1 nM (~0.2 ppb) is being detected, and the typical detection time for each sample is approximately 60 seconds. This portable sensor system advances sensing technologies and could potentially supplement expensive, laborious conventional sensing equipment.