Luminescent lanthanide sensors applications

The photophysics of lanthanide complexes has drawn considerable attention in recent years, in part because of the potential applications of lanthanides (sensors, electroluminescent displays, etc.) and several recent reviews highlighting applications of luminescent lanthanide complexes have appeared. A discussion of infrared f-f luminescence of Yb, Nd, and Er in complexes having macrocyclic ligands such as porphyrins, cyclen derivatives, and calixarenes was published by Korovin and Rusakova. " In addition, DaSilva and co-workers describe the development of highly luminescent lanthanide complexes and their application as light-conversion molecular devices. ... 

Although the conductivity of the trivalent-ion / ""-aluminas is too low for solid electrolyte applications (e g. batteries, sensors), they have potential use in optics, phosphors, and lasers because they can serve as single crystal or powder hosts for the optically active lanthanide ions. For example, Eu +-/3""-alumina emits red luminescence when excited by UV rays. A Nd +-/3""-alumina single crystal shows luminescent... 

Medical applications are so far limited in number, but gadolinium complexes of DTPA and other hgands have become highly important injectible MRI contrast agents (see Metal-based Imaging Agents). The luminescent properties of the lanthanides are becoming exploited in luminescent sensors and bioassays. 

Lanthanide(III) complexes demand special attention in view of the specific spectra-structure relationship for biological applications, chiral catalysis, molecular magnetism and luminescence. One unique chiral stereochemistry is realized by the combination of labile Ln complexes and weak Na+-fluorocarbon interactionwhich show intense CD (circular dichroism) with variation of Ln(III) and/or M(I) ions to chiroptical spectra-structure relations and an important role in configurational chirality for chemical sensors, NMR shift reagents or chiral catalysis. Trivalent lanthanides are also found to be incorporated into heterobimetallic complexes showing intramolecular energy transfer processes. 

As mentioned earher, one distinct advantage of using the Ln elements is to harness their unique optical features, namely, luminescence. Indeed, there are countless examples of this very phenomenon within the hterature, with feasible applications in display technologies or sensors. Most of the luminescence studies done on these materials are usually based on Eu + or Tb emission (25,30,161,179). The reason for concentrating on these two ions is due to the ease with which they can be sensitized by an aromatic organic linker. Just the same, other lanthanides have been studied in these systems, including Dy + (180), Ho (181), (181), Pr (182), and Gd (24). Additionally, certain crystal... 

An alternative approach to multiparametrism makes use of lanthanide complexes in conjunction with quantum dots as acceptors [157]. Another growing field for applications of lanthanide complexes is the design of luminescent sensors responding to various analytes such as pH, anions (phosphate, carbonates), metal ions, hydrogen peroxide, and ATP. Since many enzymatic reactions are associated with the consumption or formation of small molecules like hydrogen peroxide. 

The luminescence of lanthanide ions in solids has been the subject of several books or chapters [1-12] and has an immense scope. Since 1 was asked to write this review within a short time, I have failed to give a comprehensive survey but have given a qualitative overview of several areas with some references to more quantitative treatments. Topics such as lanthanide luminescence of laser materials [4,8,13,14], sensors [15], hybrid materials [16], organolanthanide, and coordination compounds [17] are missing. So what is here in October 2009 - basically, a description of the luminescence spectra of lanthanide ions in the solid state and some applications of phosphor materials. 

Lanthanides in Living Systems Lanthanides Coordination Chemistry Lanthanides Luminescence Applications Lmninescence Lanthanides Magnetic Resonance Imaging Lanthanide Oxide/Hydroxide Complexes Carboxylate Lanthanide Complexes with Multidentate Ligands Rare Earth Metal Cluster Complexes Supramolecular Chemistry from Sensors and Imaging Agents to Functional Mononuclear and Polynuclear Self-Assembly Lanthanide Complexes. 

The first two chapters of this work cover theoretical and practical aspects of the emission process, the spectroscopic techniques and the equipment used to characterize the emission. Chapter 3 introduces and reviews the property of circularly polarized emission, while Chapter 4 reviews the use of lanthanide ion complexes in bioimaging and fluorescence microscopy. Chapter 5 covers the phenomenon of two-photon absorption, its theory as well as applications in imaging, while Chapter 6 reviews the use of lanthanide ions as chemo-sensors. Chapter 7 introduces the basic principles of nanoparticle upconversion luminescence and its use for bioimaging and Chapter 8 reviews direct excitation of the lanthanide ions and the use of the excitation spectra to probe the metal ion s coordination environment in eoordination compounds and biopolymers. Finally, Chapter 9 describes the formation of heterobimetallic complexes, in whieh the lanthanide ion emission is promoted through the hetero-metal. 

---