 The application of chemosensors is referred to as chemosensing, which is a form of molecular recognition.All chemosensors are designed to contain a signalling moiety and a recognition moiety, that is connected either directly to each other or through a some kind of connector or a spacer.The signalling is often optically based electromagnetic radiation, giving rise to changes in either (or both) the ultraviolet and visible absorption or the emission properties of the sensors.