Development of an Ion-Sensor using Fluorescence Resonance Energy   Transfer
  A method is presented for the sensing of ions by determining the concentration of corresponding salts (KCl, NaCl, MgCl2, CaCl2, FeCl3, FeSO4, AlCl3) in water, based on Fluorescence resonance energy transfer (FRET) process. The principle of the proposed sensor is based on the change of FRET efficiency between two laser dyes Acriflavine and Rhodamine B in presence of different ions (K+, Na+, Mg2+, Ca2+, Fe2+, Fe3+, Al3+). Nanodimensional clay platelet laponite was used to enhance the efficiency of the sensor. 
Dibyendu Dey, Jaba Saha, D. Bhattacharjee, Syed Arshad Hussain
cond-mat.mtrl-sci physics.chem-ph