Luminescent Chemical and Physical Sensors Based on Lanthanide Complexes

Abstract

Luminescent lanthanide complexes (LLCs) are versatile probes for the determination of a variety of analytes such as metal ions, anions, hydrogen peroxide, ATP, pH, or oxygen. Antenna chromophores have been introduced as ligands for sensitizing lanthanide emission. The ligand system or the lanthanide ion can act as receptors for reversible binding of analytes. Thus, the response of luminescence emission can occur via ligand or metal-centered processes, which will both be discussed. LLCs, particularly Eu 3+ and Tb 3+ complexes, have been incorporated in solid state matrices, e.g., polymer hydrogels or silica to obtain optical sensor layers. A selection of such sensitive materials will be outlined, including sensors for the analytically relevant parameters oxygen, pH, hydrogen peroxide, humidity, and temperature.

Lanthanide Probes for Bioresponsive Imaging

“…1,13 Intense light sources such as lasers are required to populate the excited states of Ln(III) ions by direct excitation and are impractical for the majority of biological imaging. 14,16,17 Attachment of a light-harvesting antenna circumvents this limitation by sensitizing the Ln(III) ion in what has been termed as the antenna effect (Figure 1A). 7,14,18–20 Light absorbed to the short-lived singlet excited state of the antenna (S0 → S1) can undergo intersystem crossing to the longer-lived triplet excited state (S1 → T1).…”

“…13,17,19,22 The general architecture of emissive lanthanide complexes consists of the metal center surrounded by a chelate and equipped with a sensitizer or antenna. The chelate serves to prevent the release of free lanthanides into the biological systems and to protect the lanthanide from quenching from vibrational energy dissipation by oscillators like O-H of water.…”

The Dark Side of Hydrogen Bonds in the Design of Optical Materials: A Charge‐Density Perspective

“…Lanthanide (Ln) complexes are of special interest as perspective emissive components for new optical materials. [1][2][3][4][5] In the case of Eu 3 + and Tb 3 + ions, the presence of water molecules in their first coordination sphere, an occurrence that is sometimes inevitable, results in a quenching of luminescence owing to multiphonon nonradiative relaxation by OÀH oscillators. [6][7][8] This effect becomes more pronounced as a water molecule approaches the metal center.…”

Fluoreszenzbildgebung mit chemischen Sensoren

“…Es ist festzuhalten, dass die Gesamtstruktur solcher Komplexe nicht aufgedeckt wurde und die hçchste Empfindlichkeit für einen Analyten manchmal bei einem rational nicht erklärbaren Verhältnis von Lanthanoidion zu Ligand erhalten wird, meist mit einem Überschuss des Lanthanoids. [89] Typische Beispiele sind optische Sensoren für Sauerstoff, pH-Wert, Wasserstoffperoxid, Luftfeuchtigkeit, Abbildung 13. Ein Komplex aus Europium und Tetracyclin wurde in eine Polymermatrix eingebaut, wodurch reversible optische Sensoren für Wasserstoffperoxid hergestellt wurden, die mithilfe von FLIM ausgelesen werden kçnnen.…”

“…[88] Die Anwendungen beider Arten von Lanthanoid-basierten Sonden in chemischen Sensoren wurden kürzlich zusammengefasst. [89] Typische Beispiele sind optische Sensoren für Sauerstoff, pH-Wert, Wasserstoffperoxid, Luftfeuchtigkeit, Abbildung 12. Lanthanoidkomplexe mit Cyclenliganden als Beispiel für Liganden-zentrierte Sonden für den pH-Wert [76] oder Alkalimetalle.…”