Copper is a widely used metal that can leak into the environment through various routes. In low concentrations, copper is an essential nutrient; however, exposure to high levels of copper even for a short period of time can cause gastrointestinal disturbance. Long term exposure causes liver or kidney damage. Most fluorescent sensors for Cu2+ detection give quenched fluorescence, because Cu2+ is a paramagnetic metal ion. These sensors are prone to false positive results because anything that can quench fluorescence could be mistakenly interpreted as Cu2+.

This new sensor can give over 13-fold enhancement in fluorescence in the presence of very low concentrations of Cu2+. Most sensors for Cu2+ detection are based on fluorescent organic molecules that can selectively bind Cu2+. Upon Cu2+ binding, these molecules usually show quenched fluorescence. Although some of these sensors are very sensitive and selective for Cu2+, their practical applications are limited due to their light-down nature. This invention can provide highly sensitive and selective detection of Cu2+ in heavy water. In this invention, Cu2+ recognition and signaling are spatially separated. Therefore, Cu2+ quenching efforts are minimized.