ABSTRACT
A fiber-optic sensor for the detection of mercury ions in an aqueous environment was studied with rhodamine derivatives as sensing materials, namely Rhodamine-Ethylenediamine (RE) and Rhodaminederived Schiff base (RS). The rhodamine derivatives were synthesized with rhodamine 6G, and characterized by nuclear magnetic resonance spectrometer. Rhodamine derivatives having high light-sensitive properties are often used to detect a variety of metal ions. Rhodamine derivatives are non-fluorescent and colorless; whereas, ring-opening of the corresponding spirolactam gives rise to strong fluorescence emission, and a pink color. Synthesis of Rhodamine-derived Schiff base Portions of N-(rhodamine-6G)-lactam ethylenediamine and 4-diethylamino-salicylaldehyde were added to absolute ethanol. RE is synthesized from rhodamine 6G, and then RE is used to synthesize RS. The absorption intensity of RE dissolved in water with various metal ions was measured by UV spectrometer. The RS-immobilized thin film showed a linear correlation between the absorption intensity and mercury ion concentration.
