 Other examples of chemosensors that work on the principle of switching fluorescent emission either on or off include, Förster resonance energy transfer (FRET), internal charge transfer (ICT), twisted internal charge transfer (TICT), metal-based emission (such as in lanthanide luminescence), and excimer and exciplex emission and aggregation-induced emission (AIE).Chemosensors were one of the first examples of molecules that could result in switching between 'on' or 'off' states through the use of external stimuli and as such can be classed as synthetic molecular machine, to which the Nobel Prize in Chemistry was awarded to in 2016 to Jean-Pierre Sauvage, Fraser Stoddart and Bernard L. Feringa.The application of these same design principles used in chemosensing also paved the way for the development of molecular logic gates mimics (MLGMs), being first proposed using PET based fluorescent chemosensors by de Silva and co-workers in 1993.