  A method is presented for the sensing of water hardness by determining the
concentration of calcium and magnesium 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
(Acf) and Rhodamine B (RhB) in presence of permanent hard water components
(CaCl2 and MgCl2). Nanodimensional clay platelet laponite was used to enhance
the efficiency of the sensor.
