Luminescent optical probes based on lanthanide chelates have attracted particular attention over the last decades in the biomedical field due to their versatile magnetic and photoluminescent properties. Lanthanides exhibit large Stokes shifts and, therefore, reabsorption effects can be avoided. Their narrow emission bands allow for excellent spectral discrimination, they are resistant to photobleaching, and time-resolved detection can be facilitated thanks to their long photoluminescence lifetimes in the millisecond time regime. These characteristics make lanthanides useful for numerous applications. These include their broad employment in molecular imaging, such as in magnetic resonance imaging (MRI) as contrast agents. Lanthanide nanoparticles have been widely used in high-sensitivity immunoassays as well as in the detection and imaging of fingerprints.
