 This can be achieved through either a single measurement or through the use of continuous monitoring.The signalling moiety acts as a signal transducer, converting the information (recognition event between the chemosensor and the analyte) into an optical response in a clear and reproducible manner.Most commonly, the change (the signal) is observed by measuring the various physical properties of the chemosensor, such as the photo-physical properties seen in the absorption or emission, where different wavelengths of the electromagnetic spectrum are used.