Lanthanides, luminescent sensors/switche

In this section, a number of systems that have been shown to act as sensors and/or switches will be discussed. These systems have been subdivided based on their mode of operation as described in Scheme 5. In the following section these modes of operation, in conjunction with the concept of modulation, will be shown to produce lanthanide luminescent sensors and switches. 

Although not particularly designed to be a pH-sensitive luminescent probe, Beeby et al. described a phenanthridine-carrying water-soluble Yb complex, in which the photosensitisation mechanism is switched as a functi(m of pH [93], A crown ether-modified neodymium(III) cryptand was proposed for barium ion detection [94], but as with many prototype cation sensors, the probe only works in acetonitrile. Moreover, the complex necessitates ultraviolet excitation, which removes one of the main advantages of using NIR luminescent lanthanide complexes. 

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