Sensing/sensors lanthanide ions

Cation recognition by luminescence sensing has also been reported. As referred to above, release and recapture of alkali and alkaline earth metal ions for [(bpy)Re(CO)3L ]+, where Lj contains an azacrown ether [63] was controlled by light. A sensor for lanthanide ions is shown in Fig. 27. The photoactive center was RcI( bpy ) and its emission was quenched by the lanthanide ion [119]. 

Systems capable of effecting the detection of lanthanide and actinide ions using electrochemical methods have generally consisted of a receptor or ionophore immobilized within a membrane to form an ion-selective electrode (ISE). This electrode is then pertmbed when a cation guest is boimd. On the other hand, optical sensors or optodes are based on a molecule that is either free standing or attached to a polymer matrix. In both cases, the expectation is that an optical response will be produced when the system is exposed to a particular anal5de. Needless to say, for either approach it is beneficial to have a receptor that is well tuned for the lanthanides and actinides. In practice, this has translated to the use of macrocycles rich in O, N, S, or P donor atoms as will be clear from the summary of recent work provided in this article. This article focuses on ISE- and optode-based approaches to lanthanide and actinide cation sensing. 

It is clear from the many examples discussed in this chapter that lanthanide lununescent sensors, probes and imaging agents have established themselves as a major player within the field of luminescent sensing. And we can only foresee that the role of these rare-earth ions will continue to grow in the years to come, and that the field of lanthanide luminescence sensing has a very bright and varied future. 

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