Chapter 17: Time-delayed Lanthanide Luminescent Sensors and Probes

The development of lanthanide-based signalling systems that can monitor the concentration, nature and presence of certain analytes has grown rapidly over the last 25 years or so. Given their unique photophysical properties, which includes line-like emission bands/transitions, long-wavelength emission range (spanning from the visible to the near-infrared) and long-lived excited states, it comes as no surprise that today luminescent lanthanide sensors, probes and materials (e.g. films, polymers, particles, etc.) have been developed for the recognition, sensing and imaging of ions, small molecules as well as large biomolecules (nucleic acids, peptides and proteins, etc.), systems and processes (such as enzymes, etc.). This chapter gives some insight into this rapidly developing field of research. A selected number of samples will be featured and their properties and function discussed. The object herein is to demonstrate the structural versatility and the various applications that such lanthanide luminescence systems have to offer, along with expanding on how the lanthanide ions act as sensing platforms, which is seldomly seen for their organic counterparts.