A simple colorimetric device for rapid detection of Hg2+ in water

A 'turn-on' fluorescent colorimetric device for Hg2+ sensing was built using a dual light-emitting diode system. Fluorescence generated from a rhodamine derivative (RHD), an indicator for Hg2+ sensing, was combined with a background red light, and the complex light was captured by a commercial charge coupled device camera or by the naked eye.