Fluoride ions can be detected ultra sensitively and selectively by using a new sensor, gamma-butyric acid containing perylenediimide (PDI) in water. EPR studies show the involvement of radical formation during sensing. Density functional theory also supports the electrostatic interaction between hydrated fluoride and the sensor molecule. Fluoride sensing is visible through naked eyes and fluorometrically. Moreover, this sensor can be regenerated by oxidizing the sensor-fluoride complex using NOBF4. This study convincingly demonstrates the complex formation of hydrated fluoride with PDI based sensor molecule in sensing of aqueous fluorides as it is evidenced by MALDI-TOF analysis and computational studies. (C) 2013 Published by Elsevier B. V.