A sensor for detecting heavy metals in water is provided. The sensor includes a first electrode and a second electrode, the first electrode and the second electrode having complementary interdigitated surfaces that are separated from each other by a first gap having a distance of greater than or equal to about 500 nm to less than or equal to about 10 μm. The sensor also includes a power source connectable to the first electrode and the second electrode. The sensor is configured to continuously monitor water for the presence of heavy metals. Methods of making and using the sensor are also provided.