Fluorescence lifetime sensor of copper ions in water

We demonstrate an optical method for the selective detection of Cu(II) ions in water using time-resolved fluorescence resonance energy transfer from the dye rhodamine 800 encapsulated in a sensor. In comparison to copper, quenching by other metal ions such as cobalt, nickel, and chromium is shown to be negligible. The experimental arrangement incorporates picosecond diode laser excitation and time-correlated single-photon counting for detection. Down to 5 mM of copper deposited on the sensor can be measured and a linear response is obtained up to at least 50 mM. A lower limit of detection for the sensor in the region of 10 ppb is shown to be readily achievable with good resolution. (C) 1996 American Institute of Physics.